Dissertations / Theses: 'Radiographic Method'

1

Skipper, Julie A. "Feasibility of Radiographic Absorptiometry of the Mandible as an Osteoporosis Screening Method." Wright State University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=wright1057695994.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Hecla, Jake J. "A combined radiographic and time-of-flight method for zero-knowledge warhead verification." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112474.

Full text

Abstract:

Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017. "June 2017." Cataloged from PDF version of thesis. Includes bibliographical references (pages 49-51). A novel means of combined spectroscopic and radiographic zero-knowledge warhead verification has been developed and investigated using Monte Carlo simulations. This verification approach, henceforth called "epi-ZK," uses time-structured beams of epithermal neutrons to verify weapon isotopics and geometry without creating or transmitting meaningful information about the device design. This method seeks to remedy information security and hoax resistance issues inherent in previously proposed zero-knowledge verification methods such as fast neutron radiography with preloaded detector arrays and NRF based methods. By using a combination of epithermal neutron radiography and time-of-flight analysis, the epi-ZK method achieves sensitivity to subtle isotopic and geometric hoaxes, while preserving a high level of information security. Results using a MCNP5¹ model of the verification setup on the "Black Sea Object" pit geometry as well as a speculative HEU implosion weapons design indicate that the method would be highly effective, even using existing research reactor or accelerator neutron sources. This method of verification therefore presents a viable means of verification for weapons previously excluded from treaties such as ST ART due to a lack of information-secure means of assuring device authenticity. by Jake J. Hecla. S.B.

APA, Harvard, Vancouver, ISO, and other styles

3

Davidson, Robert Andrew. "Radiographic contrast-enhancement masks in digital radiography." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1932.

Full text

Abstract:

Radiographic film/screen (F/S) images have a narrow latitude or dynamic range. The film’s ability to record and view all the anatomy within the x-ray field is limited by this narrow dynamic range. The advent of digital radiographic means of storing and displaying radiographic images has improved the ability to record and visualise all of the anatomy. The problem still exists in digital radiography (DR) when radiographic examinations of certain anatomical regions are undertaken. In this work, the value of anatomically shaped radiographic contrast-enhancement masks (RCMs) in improving image contrast and reducing the dynamic range of images in DR was examined. Radiographic contrast-enhancement masks are digital masks that alter the radiographic contrast in DR images. The shape of these masks can be altered by the user. Anatomically shaped RCMs have been modelled on tissue compensation filters (TCFs) commonly used in F/S radiographic examinations. The prime purpose of a TCF is to reduce the dynamic range of photons reaching the image receptor and hence improve radiographic contrast in the resultant image. RCMs affect the dynamic range of the image rather than the energy source of the image, that of the x-ray photons. The research consisted of three distinct phases. The first phase was to examine physical TCFs and their effects on F/S radiographic images. Physical TCFs are used in radiographic F/S examinations to attenuate the x-ray beam to compensate for varying patient tissue thicknesses and/or densities. The effect of the TCF is to reduce resultant radiographic optical density variations in the image, allowing the viewer to observe a range of densities within the image which would otherwise not be visualised. Physical TCFs are commonly aluminium- or lead-based materials that attenuate the x-ray beam. A TCF has varying physical thickness to differentially attenuate the iii beam and is shaped for specific anatomical situations. During this project, various commonly used physical TCFs were examined. Measurements of size and thickness were made. Characteristics of linear attenuation coefficients and half-value thicknesses were delineated for various TCF materials and at various energies. The second phase of the research was to model the physical TCFs in a digital environment and apply the RCMs to DR images. The digital RCMs were created with similar characteristics to mimic the shapes to the physical TCFs. The RCM characteristics can be adjusted by the viewer of the image to suit the anatomy being imaged. Anatomically shaped RCMs were designed to assist in overcoming a limitation when viewing digital radiographic images, that of the dynamic range of the image. Anatomically shaped RCMs differ from other means of controlling the dynamic range of a digital radiographic image. It has been shown that RCMs can reduce the range of optical densities within images with a large dynamic range, to facilitate visualisation of all anatomy within the image. Physical TCFs are used within a specific range of radiographic F/S examinations. Digital radiographic images from this range of examinations were collected from various clinical radiological centres. Anatomically shaped RCMs were applied to the images to improve radiographic contrast of the images. The third phase of the research was to ascertain the benefits of the use of RCMs. Various other methods are currently in use to reduce the dynamic range of digital radiographic images. It is generally accepted that these methods also introduce noise into the image and hence reduce image quality. Quantitative comparisons of noise within the image were undertaken. The anatomically shaped RCMs introduced less noise than current methods designed to reduce the dynamic range of digital radiographic images. It was shown that RCM methods do not affect image quality. Radiographers make subjective assessment of digital radiographic image quality as part of their professional practice. To assess the subjective quality of images enhanced with anatomically shaped RCMs, a survey of radiographers and other iv qualified people was undertaken to ascertain any improvement in RCM-modified images compared to the original images. Participants were provided with eight pairs of image to compare. Questions were asked in the survey as to which image had the better range of optical densities; in which image the anatomy was easiest to visualise; which image had the simplest contrast and density manipulation for optimal visualisation; and which image had the overall highest image quality. Responses from 123 participants were received and analysed. The statistical analysis showed a higher preference by radiographers for the digital radiographic images in which the RCMs had been applied. Comparisons were made between anatomical regions and between patient-related factors of size, age and whether pathology was present in the image or not. The conclusion was drawn that digital RCMs correctly applied to digital radiographic images decrease the dynamic range of the image, allowing the entire anatomy to be visualised in one image. Radiographic contrast in the image can be maximised whilst maintaining image quality. Using RCMs in some digital radiographic examinations, radiographers will be able to present optimised images to referring clinicians. It is envisaged that correctly applied RCMs in certain radiographic examinations will enhance radiographic image quality and possibly lead to improved diagnosis from these images.

APA, Harvard, Vancouver, ISO, and other styles

4

Davidson, Robert Andrew. "Radiographic contrast-enhancement masks in digital radiography." University of Sydney, 2006. http://hdl.handle.net/2123/1932.

Full text

Abstract:

Doctor of Philosophy Radiographic film/screen (F/S) images have a narrow latitude or dynamic range. The film’s ability to record and view all the anatomy within the x-ray field is limited by this narrow dynamic range. The advent of digital radiographic means of storing and displaying radiographic images has improved the ability to record and visualise all of the anatomy. The problem still exists in digital radiography (DR) when radiographic examinations of certain anatomical regions are undertaken. In this work, the value of anatomically shaped radiographic contrast-enhancement masks (RCMs) in improving image contrast and reducing the dynamic range of images in DR was examined. Radiographic contrast-enhancement masks are digital masks that alter the radiographic contrast in DR images. The shape of these masks can be altered by the user. Anatomically shaped RCMs have been modelled on tissue compensation filters (TCFs) commonly used in F/S radiographic examinations. The prime purpose of a TCF is to reduce the dynamic range of photons reaching the image receptor and hence improve radiographic contrast in the resultant image. RCMs affect the dynamic range of the image rather than the energy source of the image, that of the x-ray photons. The research consisted of three distinct phases. The first phase was to examine physical TCFs and their effects on F/S radiographic images. Physical TCFs are used in radiographic F/S examinations to attenuate the x-ray beam to compensate for varying patient tissue thicknesses and/or densities. The effect of the TCF is to reduce resultant radiographic optical density variations in the image, allowing the viewer to observe a range of densities within the image which would otherwise not be visualised. Physical TCFs are commonly aluminium- or lead-based materials that attenuate the x-ray beam. A TCF has varying physical thickness to differentially attenuate the iii beam and is shaped for specific anatomical situations. During this project, various commonly used physical TCFs were examined. Measurements of size and thickness were made. Characteristics of linear attenuation coefficients and half-value thicknesses were delineated for various TCF materials and at various energies. The second phase of the research was to model the physical TCFs in a digital environment and apply the RCMs to DR images. The digital RCMs were created with similar characteristics to mimic the shapes to the physical TCFs. The RCM characteristics can be adjusted by the viewer of the image to suit the anatomy being imaged. Anatomically shaped RCMs were designed to assist in overcoming a limitation when viewing digital radiographic images, that of the dynamic range of the image. Anatomically shaped RCMs differ from other means of controlling the dynamic range of a digital radiographic image. It has been shown that RCMs can reduce the range of optical densities within images with a large dynamic range, to facilitate visualisation of all anatomy within the image. Physical TCFs are used within a specific range of radiographic F/S examinations. Digital radiographic images from this range of examinations were collected from various clinical radiological centres. Anatomically shaped RCMs were applied to the images to improve radiographic contrast of the images. The third phase of the research was to ascertain the benefits of the use of RCMs. Various other methods are currently in use to reduce the dynamic range of digital radiographic images. It is generally accepted that these methods also introduce noise into the image and hence reduce image quality. Quantitative comparisons of noise within the image were undertaken. The anatomically shaped RCMs introduced less noise than current methods designed to reduce the dynamic range of digital radiographic images. It was shown that RCM methods do not affect image quality. Radiographers make subjective assessment of digital radiographic image quality as part of their professional practice. To assess the subjective quality of images enhanced with anatomically shaped RCMs, a survey of radiographers and other iv qualified people was undertaken to ascertain any improvement in RCM-modified images compared to the original images. Participants were provided with eight pairs of image to compare. Questions were asked in the survey as to which image had the better range of optical densities; in which image the anatomy was easiest to visualise; which image had the simplest contrast and density manipulation for optimal visualisation; and which image had the overall highest image quality. Responses from 123 participants were received and analysed. The statistical analysis showed a higher preference by radiographers for the digital radiographic images in which the RCMs had been applied. Comparisons were made between anatomical regions and between patient-related factors of size, age and whether pathology was present in the image or not. The conclusion was drawn that digital RCMs correctly applied to digital radiographic images decrease the dynamic range of the image, allowing the entire anatomy to be visualised in one image. Radiographic contrast in the image can be maximised whilst maintaining image quality. Using RCMs in some digital radiographic examinations, radiographers will be able to present optimised images to referring clinicians. It is envisaged that correctly applied RCMs in certain radiographic examinations will enhance radiographic image quality and possibly lead to improved diagnosis from these images.

APA, Harvard, Vancouver, ISO, and other styles

5

Malusek, Alexandr. "Calculation of scatter in cone beam CT : Steps towards a virtual tomograph." Doctoral thesis, Linköping : Department of Medical and Health Sciences, Linköping University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11275.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Hackman, S. Lucina M. R. "Age estimation in the living : a test of 6 radiographic methods." Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/b8281974-f44c-444d-b958-001ccfea451f.

Full text

Abstract:

There is a growing recognition that there is a requirement for methods of age estimation of the living to be rigorously tested to ensure that they are accurate, reliable and valid for use in forensic and humanitarian age estimation. The necessity for accurate and reliable methods of age estimation are driven both by humanitarian, political and judicial need. Age estimation methods commonly in use today are based on the application of reference standards, known as atlases, which were developed using data collected from children who participated in longitudinal studies in the early to mid-1900s. The standards were originally developed to provide a baseline to which radiographs could be compared in order to assess the child’s stage of skeletal development in relation to their chronological age, a purpose for which they are still utilised in the medical community. These atlases provide a testable link between skeletal age and chronological age which has been recognised by forensic practitioners who have essentially hijacked this medical capability and applied it to their fields. This has resulted in an increased use of these standards as a method of predicting the chronological age from the skeletal age of a child when the former is unknown. This novel use of the atlases on populations who are distinct, ethnically, temporally and geographically, from those whose data was gathered and was used in the design of the standard leaves the forensic outcomes vulnerable to challenge in court. This study aims to examine the reliability and accuracy of these standards in relation to a modern population, providing a sound statistical base for the use of these standards for forensic purposes. Radiographs were collected from the local hospital from children who had been X-rayed for investigation during attendance at the local A&E department. Four body areas were selected for investigation; the hand-wrist, the elbow, the knee and the foot-ankle and tests were undertaken to assess the radiographs using six commonly uses methods of age estimation. Further images of the wrist and elbow were collected from children in New Delhi, India. These images were subject to age estimation utilising the methods described.

APA, Harvard, Vancouver, ISO, and other styles

7

Foss, Olav A. "The Rotation Ratios Method - A Method to describe altered spatial orientation in sequential radiographs from one pelvis." Doctoral thesis, Norwegian University of Science and Technology, Department of Neuroscience, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2127.

Full text

Abstract:

The Rotation Ratios MethodEn metode for beskrivelse av endret romlig bekkeninnstilling svedsekvensielle røntgenopptak av samme bekkenSammendraget:Sekvensielle røntgenopptak av ett og samme bekken blir rutinemessig brukt bl.a. innen ortopedisk kirurgi. Ofte sammenliknes korresponderende røntgenmål for å vurdere sykdomsutvikling eller vurdere effekten av en behandling. Tre-dimensjonale objekt blir transformert til to-dimensjonale bilder ved røntgenopptak. Både den romlige innstillingen av objektet og fokusering av røntgenrøret i forhold til objektet påvirker avbildingen. Endringer i disse innstillingene kan derfor påvirke aktuelle røntgenmål og representere en feilkilde når korresponderende røntgenmål sammenliknes. I en serie av fire arbeid presenteres utviklingen av en målemetode som beskriver endringer i bekkeninnstilling om to akser, basert på standard frontale (AP) bekkenopptak.To parametre som beskriver endring i bekkeninnstilling eller endring i røntgenfokusering ble validert ved bruk av definerte røntgenopptak av et bekkenfantom.Et dataprogram for simulering av røntgenopptak av rigide objekt ble utviklet og validert. Dette programmet representerer et virtuelt røntgenlaboratorium der objektorientering, røntgenfokusering, mm. kan endres.Dette dataprogrammet ble brukt til simulering av 4653 røntgenbilder av 141 utvalgte bekken, representerende en normalpopulasjon. Simulerte røntgenmål fra disse bildene ble brukt i utviklingen av et formelapparat for klinisk bruk. Korreksjonsfaktorer for kjønn og bekkenstørrelse ble innarbeidet.Metoden, som er en algoritme inkluderende både manuelle og matematiske prosedyrer ble validert. Først ble de manuelle delene validert enkeltvis før en samlet validering ble gjort der en sammenliknet 1020 beregnede bekkenrotasjoner mot korresponderende reelle.Metoden synes å ha god nok nøyaktighet for klinisk bruk.

APA, Harvard, Vancouver, ISO, and other styles

8

Rosenbaum, Kayla A. "Radiography Students: Factors Contributing to their Stress and Methods of Coping." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3111.

Full text

Abstract:

College students experience high levels of stress, especially those in health care programs. The purpose of this study was to determine what factors contribute to Tennessee radiography student stress levels and the methods by which they cope with stress. Additionally, do demographic factors affect radiography student stress levels? The research was conducted February 4 to March 30, 2016. A survey was distributed to students in a radiography program at two and four year colleges in Tennessee. Participants were asked questions on factors that influence their stress levels, coping strategies, and health issues experienced in the past year. Descriptive statistics, independent samples t-test, and Pearson correlations were used to determine what factors influenced student stress levels, the most effective coping strategies, and if demographics affected student stress levels. This analysis revealed that school causes students the most stress, while taking a break was the most used stress coping strategy.

APA, Harvard, Vancouver, ISO, and other styles

9

Hashim, Hanizah Aman. "The reproducibility of Johnston's cephalometric superimposition method in analyzing activator treatment changes." Thesis, The University of Sydney, 1990. http://hdl.handle.net/2123/4932.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Huang, Zhao-Wei. "Automated Scoring for Cystic Fibrosis in Chest Radiographs based on Deep Learning Methods." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20401.

Full text

Abstract:

Cystic fibrosis (CF) is a genetic disease that attacks multiple organs. It is an incurable illness in the respiratory system, with about one-sixth of native Australians suffering from it. Cystic Fibrosis Community Care* shows that 1 in 25 people in Australia are carrying defective CF genes and nearly 90 babies each year are born with CF. Clinicians diagnosed the pulmonary CF mainly through chest radiographs (CXRs). This study proposes a novel computer-aided diagnostic (CAD) framework with deep learning features for automated scoring of CF in CXRs. Within this framework, key components and algorithms are developed, examined and refined to achieve the best scoring performance as compared to human observers. We present a framework to analyse chest radiographs for cystic fibrosis using machine learning methods. We compare the representational power of deep learning features with traditional texture features. Specifically, we respectively employed VGG-16-based deep learning features and Tamura- and Gabor-filter-based textural features to represent the cystic fibrosis images. We demonstrate that VGG-16 features perform best, with a maximum agreement of 82%. In addition, Tamura features’ accuracy of Tamura reaches 78%. We also present a framework to analyse chest radiographs for cystic fibrosis using deep learning methods. We compare the effectiveness of two typical deep convolution neural networks, ResNet-152 and VGG-16, both of which are transferred the knowledge learned from the ChestX-ray14 dataset. We had the best scoring accuracies of 91% for ResNet-152 and 86% for VGG-16, 12.3% and 3.6% respectively better than the networks pre-trained by natural images on ImageNet. The overall best performance was exhibited by transfer-learning-based ResNet-152 with random forest classifier. It achieved 91.5% accuracy for classification across three levels of scoring (10, 15 and 20).

APA, Harvard, Vancouver, ISO, and other styles

11

Dubory, Arnaud. "Interface os-implant titane et ingénierie tissulaire A cadaveric validation of a method based on impact analysis to monitor the femoral stem insertion Bone marrow mesenchymal stem cells predict radiographic osseointegration of cementeless titanium hip cups Survival, adhesion, and expression of osteoblastic genes of human derived-bone marrow mesenchymal stromal cells on PEEK and titanium-coated PEEK lumbar interbody cages." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC0067.

Full text

Abstract:

Introduction : Le titane, à la fois utilisé comme moyen de fixation d’un implant devant ses propriétés biomécaniques proches de l’os et comme moyen d’ostéointégration a pris une place prépondérante en orthopédie. L’ostéointégration d’un implant titane (IT) essentielle pour la pérennité de ce dernier, dépend de 2 phases : une phase primaire MECANIQUE correspondant à l’impaction ou tenue primaire de l’IT et une phase secondaire BIOLOGIQUE correspondant à la colonisation de l’IT par le tissu osseux.L’objectif de ce travail fut d’évaluer et d’améliorer lors de ces deux phases la stabilité et l’ostéointégration de l’implant titane :(1) Évaluer la tenue primaire des tiges fémorales en titane non cimentées par l’analyse de l’impact correspondant à la mesure de l’impact au cours du temps.(2) Évaluer si la quantité de CSM contenues dans l’aile iliaque est corrélée à la survie sans reprise de des implants acétabulaires impactés dans le cadre de l’ostéonécrose aseptique de la tête fémorale.(3) Améliorer l’ostéointégration des IT par les méthodes de thérapie cellulaire en étudiant in vitro la survie et la division des cellules stromales mésenchymateuses humaines (CSM) osseuses au contact de cages lombaires inter-somatiques recouvertes d’alliage titane rugueux.Matériels et Méthodes: L’évaluation de la tenue primaire des tiges fémorales en titane sans ciment selon l’analyse de l’impact a été réalisée à l’aide d’un marteau muni d’un capteur de force piézo-électrique sur 20 sujets anatomiques soit 40 hanches. On a comparé le nombre de coups de marteau pour obtenir l’impaction idéale de la prothèse selon 3 méthodes d’évaluation différentes : le nombre de coups nécessaires pour le chirurgien (Nchir), le nombre de coups nécessaires par l’analyse vidéo de l’enfoncement de la tige dans le fémur (Nvid) et le nombre de coups nécessaires par l’analyse de l’impact (NI).Pour savoir si la quantité de CSMs dans la crête iliaque pouvait refléter l’ostéointégration des implants acétabulaires impactées et le risque de reprise chirurgicale, on a comparé le taux de CSMs mesuré lors de la réalisation d’une ponction concentration et réinjection dans la zone d’ostéonécrose et l’évolution clinico-radiographique des implants acétabulaires mis en place par la suite pour ces même patients (n=90) qui ont eu une arthroplastie totale de hanche in fine. Le recul moyen était de 15 ans.La survie cellulaire des CSM osseuses humaines a été évaluée sur des cages intersomatiques lombaires recouvertes de titane. Trois groupes (n=5) furent constitués : un groupe contrôle, un groupe cages avec surface titane, un groupe cage sans titane. Sur chaque implant, 1 microlitre contenant 106 CSM osseuses humaines a été mis en culture. L’analyse de la survie cellulaire, de la prolifération cellulaire et de l’expression de gènes de différenciation ostéoblastique ont été réalisés et comparés.Résultats : Concernant la première étude sur l’intérêt de l’analyse de l’impact pour la tenue de la tige fémorale, la différence entre NI, Nchir et Nvid était inférieure ou égale à 3 pour plus de 85% des configurations réalisées. Concernant la deuxième étude, il a été mis en évidence qu’un faible nombre de CSM dans la crête iliaque était un facteur de risque de révision chirurgicale chez les patients traités par un implant acétabulaire sans ciment. La troisième étude a montré que les CSMs pouvaient survivre, se développer pendant 96 heures et exprimer des gènes de différenciation ostéoblastique de manière identique sur les cages avec ou sans titane.Conclusion : L’analyse de l’impact permet de donner une information objective sur la tenue primaire de la tige fémorale en titane et impactée. Le titane est aussi un milieu favorisé de survie et de prolifération des CSM osseuses prédestinées à devenir des cellules ostéoformatrices surtout qu’un faible nombre de CSM semble être un risque d’échec d’ostéointégration des implants acétabulaires sans ciment Introduction: Titanium, both used as a mean of fixing an implant to its biomechanical properties close to the bone and as a mean of osseointegration has taken a prominent place. The implant stability is essential for the durability of a titanium implant (TI); it depends on 2 phases: a primary phase, MECHANICAL, corresponding to the impaction or primary holding of the TI and a secondary phase, BIOLOGICAL, corresponding to the colonization of TI by bone tissue.The objective of this work was to evaluate and improve during these two phases the osseointegration of the titanium implant:(1) To evaluate the primary stability of uncemented titanium femoral stems by impact analysis corresponding to the measurement of impact over time.(2) To evaluate whether the amount of mesenchymal stromal cells (MSCs) contained in the iliac crest is correlated with the non-recovery survival of acetabular implants impacted in a context of aseptic osteonecrosis of the femoral head.(3) To improve the osseointegration of TI by cell therapy methods in vitro by studying the survival and division of human MSCs in contact with interbody lumbar cages coated with rough titanium alloy.Methods: The evaluation of the primary stability of cementless titanium femoral stems according to the impact analysis was carried out using a hammer equipped with a piezoelectric force sensor on 20 anatomical subjects, i.e. 40 hips. The number of hammer strokes was compared to obtain the ideal impaction of the prosthesis according to 3 different evaluation methods: number of impacts required by the surgeon (Nsurg), number of impacts required by the video analysis of the depression of the stem in the femur (Nvid), numbers of impacts needed by the impact analysis (Ni).To determine whether the amount of MSCs in the iliac crest could reflect the osseointegration of impacted acetabular implants and the risk of surgical revision. The rate of MSCs measured when performing a surgical cell therapy for aseptic osteonecrosis of the femoral head and the clinical and radiographic outcome of acetabular implants subsequently established for these same patients (n = 90), who had total hip arthroplasty in fine were compared. The mean follow-up was 15 years.The cell survival of bone marrow-derived MSCs was evaluated on lumbar interbody cages coated with titanium. Three groups (n = 5) were formed: a control group, a cage group with titanium surface, a cage group without titanium. On each implant, 1 microliter containing 106 human bone MSCs was cultured. The analysis of cell survival, cell proliferation and expression of osteoblastic genes were performed and compared.Results: Regarding the impact analysis of the cementless femoral stem impaction, the difference between NI, Nchir and Nvid was lower than 3 for more than 85% of the configurations performed.For the second study, a small number of MSCs in the iliac crest was a risk factor for surgical revision in patients treated with a cementless acetabular implant.The third study showed that MSCs could grow until 96 hours and could express osteoblastics genes 21 days after cell seed. No difference between PEEK cage and Titanium-coated PEEK has been found.Conclusion: The impact analysis provides objective data on the primary holding of the titanium impacted femoral stem. Titanium is also a favored biomaterial for the survival and proliferation of bone marrow-derived MSC predestined to become osteforming cells, especially since a small number of MSCs seems to be a risk of failure of osseointegration of cementless acetabular implants

APA, Harvard, Vancouver, ISO, and other styles

12

Barritt, Andrew Stephen. "Detection of hydrogen embrittlement in steel and steel alloys using methods of neutron radiography." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32597.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Erskine, Richard B. "A method of three-dimensional analysis of skull radiographs using paired views with selected rotation between exposure." Thesis, University of Dundee, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261784.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Harvey, Steven Brian. "Interactive computer methods for morphometric and kinematic measurement of images of the spine." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU116153.

Full text

Abstract:

The aim of this project was to develop robust interactive computer methods for measuring the shape and movement of the lumbar spine vertebrae from lateral radiographs of the spine. In order to achieve this aim, two software packages were written - the Aberdeen Vertebral Morphometry System (AVMS) and the Aberdeen Spinal Videofluoroscopy System (ASVS). AVMS was designed to analyse static images from dual energy x-ray absorptiometry (DXA) imaging densitometers. Comparative precision tests of the ability of AVMS software and Lunar EXPERT-XL software to measure vertebral height were undertaken using four vertebrae from the same lateral spine image (male, 67 years). Two of the vertebrae in this image were abnormal and two were normal. It was concluded that AVMS had higher precision when measuring abnormal and normal vertebrae. The effects of axial rotation and lateral bending, which lead to movement out of the sagittal plane, were investigated by generating a three-dimensional computer model of two adjacent vertebrae and projecting it on to the sagittal plane. The projected model was measured as if it were a radiograph, allowing the effects of out-of-plane movement and errors in reference point placement to be calculated. ASVS was used to acquire and analyse a sequence of images of the spine in motion obtained using videofluoroscopy and incorporated the findings of the computer modelling work. A clinical study for the measurement of intervertebral motion using ASVS during flexion-extension was organised and seven subjects suffering from severe lower back pain were recruited. Analysis of the image sequences using the computerised measurement system in ASVS revealed the apparent effect of analgesia/sedative on the shape and size of centroidal trajectories of vertebrae, and the differences in trajectory shape between subjects. It was concluded that ASVS was able to quantify spinal motion at a minimal radiation dose to the subject.

APA, Harvard, Vancouver, ISO, and other styles

15

Lemmon, Heber. "Methods for reduced platen compression (RPC) test specimen cutting locations using micro-CT and planar radiographs." Texas A&M University, 2003. http://hdl.handle.net/1969/310.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Yeo, Inhwan. "New methods for improving x-ray film in-phantom dosimetry for megavoltage photon radiotherapy." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/17615.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Sorppanen, S. (Sanna). "Kliinisen radiografiatieteen tutkimuskohde:käsiteanalyyttinen tutkimus kliinisen radiografiatieteen tutkimuskohdetta määrittävistä käsitteistä ja käsitteiden välisistä yhteyksistä." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:951428058X.

Full text

Abstract:

The objective of this study was to analyse the central concepts of radiography and connections between them, assumed to define the focus of the radiography science. The objective was also to define these concepts theoretically, and to formulate a model defining the focus of radiography science. Radiography refers here to radiographers' professional work, education and radiography science. The concepts of nursing, environment, health and human being were used as starting point for the study, as they are commonly applied, but not clearly defined in radiography. The study was conducted in three phases in accordance with the hybrid method of concept analysis. During the theoretical phase, the theoretical phase model and tentative definitions were developed on the grounds of literature. These were further developed during the empirical phase, as the empirical phase model was formulated on the grounds of empirical data. Data were collected in the form of interviews and written material from selected experts (n = 8). In the analytical phase, theoretical definitions and the model of the focus of radiography science were formulated as a synthesis of the results of former phases. The total number of data was 1,147 pages, and it was analysed with the method of qualitative content analysis. Based on the results, the concept of nursing was substituted with the concept of clinical radiography and radiotherapy, which was defined as radiographer's work within health care. Seamless combination of patient care and service as well as technical usage of radiation and radiation protection was found to be the core of a radiographer's work, aimed at serving the health care field as part of a multiprofessional teamwork. Essential characteristics of the work were found to be theoretical and practical-technical expertise, guiding elements, implementation as a process, and responsibility for safety as well as optimizing decision-making. Environment was defined as the physical and functional environment in health care, cultural environment, cognitive environment, and context of a radiographer's expertise. The concept of health was substituted with the concept of health and illness, which was defined as a holistic and variable state of being that is indirectly affected by radiation. A human being was defined as a dignified individual or community, which is also a holistic and variable being. Connections were found to be positive, negative, characterizing, directing, functional and experimental by nature. On the basis of the results, radiography science could be named the clinical science of radiography and radiotherapy. The model formulated in this study describes the focus of the clinical science of radiography and radiotherapy on a general level. The results may be exploited in the development of the clinical science of radiography and radiotherapy, in theory development and in education within radiography. They may also clarify the identity of this science and understanding regarding it Tiivistelmä Tutkimuksen tarkoituksena oli analysoida radiografian keskeisiä käsitteitä ja niiden välisiä yhteyksiä, joiden voidaan olettaa määrittävän radiografiatieteen tutkimuskohdetta. Tarkoituksena oli määritellä käsitteet teoreettisesti sekä muodostaa käsitteiden ja niiden välisten yhteyksien perusteella malli radiografiatieteen tutkimuskohteesta. Radiografialla tarkoitetaan tässä tutkimuksessa röntgenhoitajan työtä ja koulutusta sekä radiografiatiedettä. Lähtökohtana käytettiin hoitotieteen käsitteitä hoitotyö, ympäristö, terveys ja ihminen, joita on radiografiassa käytetty ja sovellettu, mutta ei täsmällisesti määritelty. Tutkimus toteutettiin kolmivaiheisesti hybridisen käsiteanalyysimenetelmän mukaan. Teoreettisessa vaiheessa muodostettiin kirjallisuuden perusteella käsitteiden työmääritelmät ja teoreettisen vaiheen malli. Empiirisessä vaiheessa muodostettiin empiirisen vaiheen malli asiantuntijoilta (n = 8) kerätyn kirjallisen ja haastatteluaineiston perusteella. Analyyttisessä vaiheessa muodostettiin tulosten systemaattiseen vertailuun perustuvana synteesinä käsitteiden teoreettiset määritelmät ja malli radiografiatieteen tutkimuskohteesta. Aineiston kokonaismäärä oli 1147 sivua, ja se analysoitiin laadullisella sisällönanalyysillä. Tutkimuksen tuloksena hoitotyö-käsite korvattiin käsitteellä kliininen röntgenhoitajan työ. Se määriteltiin röntgenhoitajan terveydenhuollossa toteuttamaksi työksi, jonka ydin on teknisen säteilynkäytön ja säteilysuojelun sekä potilaan hoidon ja palvelun saumaton yhdistäminen. Ytimen avulla työ palvelee terveydenhuollon toimintaympäristöä osana moniammatillista tiimityötä. Työn keskeiset ominaisuudet ovat teoreettinen ja käytännöllis-tekninen asiantuntijuus, ohjaavat tekijät, prosessimaisuus sekä turvallisuusvastuu ja optimoiva päätöksenteko. Ympäristö määriteltiin fyysiseksi terveydenhuollon toimintaympäristöksi, kulttuuriympäristöksi, kognitiiviseksi ympäristöksi ja röntgenhoitajan asiantuntijuuden muodostamaksi ympäristöksi. Terveys-käsite korvattiin käsitteellä terveys ja sairaus, joka määriteltiin kokonaisvaltaiseksi ilmiöksi ja muuttuvaksi tilaksi, jonka kannalta keskeisiä ovat säteilyn välilliset vaikutukset. Ihminen määriteltiin arvokkaaksi yksilöksi tai yhteisöksi, joka on kokonaisvaltainen ja muuttuva olento. Käsitteiden väliset yhteydet voivat olla positiivisia, negatiivisia, luonnehtivia ja ohjaavia yhteyksiä sekä tekemis- ja kokemisyhteyksiä. Tulosten perusteella radiografiatieteen nimeksi sopisi kliininen radiografiatiede. Tutkimuksessa tuotettu malli määrittää kliinisen radiografiatieteen tutkimuskohdetta yleisluontoisesti. Tuloksia voidaan hyödyntää lähinnä kliinisen radiografiatieteen kehittämisessä, teorianmuodostuksessa ja radiografian koulutuksessa. Tulokset voivat myös auttaa selkeyttämään kliinisen radiografiatieteen identiteettiä ja lisäämään sitä koskevaa ymmärrystä

APA, Harvard, Vancouver, ISO, and other styles

18

Gold, Brenda Joan. "A roentgen stereophotogrammetric analysis system for the measurement of subsidence of the femoral components in total hip arthroplasty." Thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/26276.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Lamoš, Martin. "Modelování metod číslicového zpracování obrazu u digitální radiografie." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218768.

Full text

Abstract:

This paper describes a MATLAB application with the main purpose of the simulation of noise components and noise elimination methods of Digital Radiography. The main parts of simulator are the model of a scene, procedures for loading the noise components to image data and methods for image processing. Various methods are employed depending on the type of noise. Subtraction techniques are used for the elimination of structural noise. The physical noise suppression is obtained using several methods of cumulation and Pixel Shift is used to reduce motion artifacts caused by the existence of moving noise. The techniques of superposition highlight the areas of interest in an image. Included are also auxiliary procedures for simulator running and presentation of final data. The model and the presented application can be used mainly for educational purposes as a powerful didactic tool.

APA, Harvard, Vancouver, ISO, and other styles

20

Uys, Andre. "A pilot study to assess dental age estimation in black South African children using Demirjian's method." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/27740.

Full text

Abstract:

The age estimation method as described by Demirjian is the most frequently used tool to estimate the sub-adult dental age in forensic dentistry. This technique has been shown to over or under estimate the chronological age of sub-adults when applied to specific population groups. The aim of this study was to compare a black South African population sample with the original French-Canadian model to determine if Demirjian’s method accurately reflects the true chronological age of this population group. A sample of panoramic radiographs from 279 boys and 325 girls between the ages of 6 and 16 was obtained from the School of Dentistry University of Pretoria, and from orthodontists in private practice in the Pretoria region. The panoramic radiographs were used to score the seven left mandibular teeth. The calculated maturity score was used to determine the Demirjian dental age. All panoramic radiographs were scored by one examiner. A subset of 20 panoramic radiographs was scored by a second examiner and reliability tested using a Wilcoxon Matched Pairs Test. This research showed that black South African children have a more advanced dental age compared to French-Canadian children. Demirjian overestimated the age for boys by 0.8 years and for girls by 0.5 years. The dental age assessment provided by Demirjian is not suitable for black South African children. As a result, new standards of dental age assessment should be established for this population. Copyright Dissertation (MSc(Odont))--University of Pretoria, 2011. Oral Pathology and Oral Biology unrestricted

APA, Harvard, Vancouver, ISO, and other styles

21

Olsson, Magnus. "Metod för dosoptimering av digitalt detektorsystem i klinisk drift." Thesis, Linköping University, Department of Biomedical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2471.

Full text

Abstract:

The county of Dalarna is at present carrying through a process of digitalization where traditional x-ray film is being replaced with digital detectors. Earlier used methods for dose optimization turned out not being sufficient. This report presents a method to harmonize dose levels between x- ray sites equipped with Fujifilm imaging plate systems. An exposure index, S, related to the dose level of the examination is computed to every x-ray image. S turned out to be inversely proportional to the detector dose used at the examination. Detector dose is also the one simulated factor that doubtlessly affects S the most.There are however a lot of parameters, e.g difference between patients, that are not easily simulated even though they still have considerable affect. The method for harmonizing dose levels between x-ray sites are based on statistics of collected S-values for a kind of examination. The average of the collected S-values levels variations and is a more solid measure of the dose level for the examination. By means of this method the dose level of frontal images of the lungs at a site have been reduced by 30 per cent without endanger the diagnostic security.

APA, Harvard, Vancouver, ISO, and other styles

22

Osei, Ernest Kwaku. "Assessment of fetal radiation dose to patients and staff in diagnostic radiology." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323356.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Nilsson, Tore. "Simulation supported training in oral radiology : methods and impact on interpretative skill." Doctoral thesis, Umeå : Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1118.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Tangboonduangjit, Puangpen. "Intensity-modulated radiation therapy dose maps the matchline effect /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060724.095712/index.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

VITUCCI, GIUSEPPE. "Advances in instruments and methods for neutron transmission imaging." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241081.

Full text

Abstract:

Il lavoro presentato in questa tesi si concentra sullo sviluppo e sul miglioramento della strumentazione e dei metodi applicati all'imaging a trasmissione di neutroni. Le attività di ricerca sono state svolte presso il laboratorio di "Imaging and Materials Science and Engineering" (IMAT). Questa struttura fa parte della sorgente di neutroni ISIS presso il Rutherford Appleton Laboratory (UK). I neutroni qui sono prodotti dalla spallazione di un bersaglio di tungsteno colpito da protoni con energia di 800 MeV. I neutroni risultanti vengono moderati e convogliati attraverso le guide dei fasci verso l'area sperimentale IMAT. Lo spettro dei neutroni è caratterizzato dalla presenza di neutroni termici e freddi con una lunghezza d'onda compresa tra 0,68 e 6,8 A. IMAT è stato progettato per acquisire impulsi di neutroni in modalità tempo di volo, registrando il tempo di arrivo dei neutroni, relativo alla loro energia, con una risoluzione temporale massima di 10 ns. Questa analisi viene eseguita con un rilevatore di nuova generazione, che è una combinazione di un convertitore di neutroni “MicroChannel Plate” e un readout elettronico “TIMEPIX”. Mediante questo apparato, radiografie e tomografie con un campo visivo di 28 mm^2 possono essere generate con una risoluzione spaziale di 55 um e a particolari energie dei neutroni incidenti. Una fotocamera CMOS di maggiori dimensioni può essere utilizzata in combinazione con gli scintillatori a 6LiF/ZnS per acquisire immagini fino a 200 * 200 mm^2 in modalità white-beam. Ciò apre diverse possibilità. Da una parte, la tecnica di imaging neutronico risolta in energia può essere utilizzata per studiare composizione e texture dei campioni tramite software di analisi dei Bragg Edge, a costo di un campo visivo ridotto. Dall’altra, i campioni più grandi possono essere studiati con fotocamere standard basate su CMOS o CCD, ma perdendo qualsiasi informazione sull'energia dei neutroni in ingresso. In questo lavoro, la prima parte è dedicata alla descrizione della strumentazione IMAT, incluso il progetto della beamline, l'area sperimentale e i rivelatori. La seconda parte è diretta a casi di studio basati su queste nuove tecniche di strumentazione e di imaging. In particolare, nel campo del patrimonio culturale, tali metodi non distruttivi sono utilizzati, in quanto i campioni sono spesso piccoli e delicati. Per esempio, abbiamo analizzato una perla "soufflè". La loro particolarità risiede nel fatto che sono vuote all'interno. L'ispezione della struttura morfologica della parte interna e l'individuazione dei diversi orientamenti dei cristalliti sono stati condotti con tecniche di imaging risolte in energia. Un secondo esperimento, presentato in questa tesi, riguarda lo studio di una serie di griglie metalliche con una dimensione fino a 200 * 10 mm^2. In questo caso, un modo rapido e non distruttivo per verificare lo spessore dello strato di carburo di boro di 1 um depositato sulle lamelle è stato implementato con successo, considerando un'incertezza di 120 nm. La terza parte è rivolta a mostrare due nuovi metodi sviluppati per migliorare la fotocamera del rivelatore MCP in termini di risoluzione spaziale e affidabilità. Per quanto riguarda la risoluzione spaziale, è stata testata una nuova procedura basata su un algoritmo di centroiding. Questo metodo di acquisizione consente di superare il vincolo fisico dato dalla dimensione dei pixel del readout elettronico e di acquisire immagini con risoluzioni fino a quattro volte superiori. Inoltre, è stato sviluppato un sistema per migliorare le immagini generate dal rivelatore MCP in post-elaborazione. Uno dei punti deboli del readout TIMEPIX installato sul rivelatore MCP è il fatto di essere costituito da quattro matrici di pixel assemblate insieme. Ciò porta a notevoli artefatti che possono causare problemi nell'analisi dei dati. Una procedure con software specifico è stata implementata per risolvere il problema. The work presented in this thesis focuses on the development and improvement of instrumentation and methods applied to neutron transmission imaging. In particular, the research activities have been performed at the "Imaging and Materials Science and Engineering" (IMAT) instrument. This facility is a part of the ISIS neutron source at the Rutherford Appleton Laboratory, in UK. The neutrons here are produced by spallation of a tungsten target hit by protons with energy of 800 MeV. The resulting neutrons are then moderated and convoyed through beam guides towards the IMAT experimental area. The neutrons spectrum in this case is characterized by the presence of thermal and cold neutrons with a wavelength in the range of 0.68 - 6.8 A. IMAT has been designed to acquire neutron pulses in Time-Of-Flight mode, by recording the time of arrival of neutrons, related to their energy, with a maximum of 10 ns timing resolution. This analysis is performed with a new generation detector, that is a combination of a MicroChannel Plate neutron converter with a TIMEPIX electronic readout. By means of this apparatus, radiographies and tomographies with a field of view of 28 mm^2 can be generated with a spatial resolution of 55 \textmu m and with respect to specific neutron energies. Beside this device, a larger CMOS camera can be used in combination with 6LiF/ZnS based neutron screen scintillators to acquire images up to 200 * 200 mm^2 in white-beam imaging. Such configuration opens several possibilities in different case scenarios. In one hand, the energy-resolved neutron imaging technique can be used to investigate the phase fraction composition and texture of the samples via Bragg Edge analysis software tools, at the cost of a reduced field of view. On the other hand, bigger samples can be studied with standard CMOS or CCD based white-beam imaging cameras, but loosing any information about the energy of the incoming neutrons. In this work, the first part is devoted to the description of the IMAT instrumentation, including the beamline design, the experimental area and the detectors. The second part is directed to case studies that made use of these novel instrumentation and imaging techniques. In particular, the cultural heritage takes advantage of such non-destructive methods where small and delicate specimens must be analysed. In this class of examples, a "soufflè" pearl was considered. The peculiarity of these cultured pearls resides in the fact that they are empty inside. The inspection of the morphological structure of the inner part, as well as the individuation of the different orientations of the nacres crystallites was conducted with energy-resolved imaging. A second experiment, presented in this thesis, regards the diagnosis of a series of metallic grids with a size up to 200 * 10 mm^2. For this case, a fast and non destructive way to verify the thickness of 1 um boron carbide layer deposited over the lamellae was successfully implemented, within an uncertainty of 120 nm. The third part is directed to show two new methods developed to improve the MCP detector camera in terms of spatial resolution and reliability. For what concerns the spatial resolution, a new procedure based on a centroiding algorithm has been tested. This acquisition method enables the possibility to go over the physical constraint given by the dimension of the pixels of the electronic readout and to acquire images with a resolutions up to four times higher. Furthermore, an improvement to the resulting images generated by the MCP detector has been developed, based on a post-processing approach. Actually, one of the weak spots of the TIMEPIX readout installed on the MCP detector is that it is constituted by four matrices of pixels assembled together. This brings to noticeable artifacts which, in some cases, may produce issues in the data analysis. A procedure, including a customized software, was implemented to fix such problem.

APA, Harvard, Vancouver, ISO, and other styles

26

Thacker, Samta C. "Development of a Monte Carlo simulation method for use in investigating CT (Computed Tomography) mammography." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0430104-153425.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Carvalho, Fabíola Bastos de. "Avaliação das alterações radiográficas após tratamento endodôntico de dentes com lesão periapical empregando dois programas de interpretação de imagens /." Araraquara: [s.l.], 2006. http://hdl.handle.net/11449/90406.

Full text

Abstract:

Orientador: Marcelo Gonçalves Banca: Mário Tanomaru Filho Banca: Eduardo Kazuo Sannomiya Resumo: O objetivo desse estudo foi avaliar as alterações radiográficas de lesões periapicais, nos períodos de proservação de 0, 2, 4 e 6 meses após o tratamento endodôntico, por meio da subtração radiográfica digital realizada pelo programa Adobe Photoshop 6.0, e da demarcação de seus limites externos na tela do computador utilizando o programa VixWin 2000. E em seguida, fazer uma comparação entre as áreas de reparação ou perda óssea visualizadas nos dois programas. Foram utilizados 13 dentes anteriores de humanos com necrose pulpar e lesão periapical crônica, que foram tratados endodonticamente. Após o tratamento endodôntico, para realização da radiografia final, foi utilizada uma técnica para padronização das imagens que consistiu no uso de um posicionador para filmes radiográficos, o qual foi estabilizado com material de impressão (silicona) colocado sobre os bordos incisais dos dentes radiografados. Para as radiografias de proservação realizadas 2, 4 e 6 meses após o tratamento endodôntico foi utilizado o mesmo método. Os filmes radiográficos foram processados automaticamente, digitalizados por meio de um scanner, e em seguida feita a subtração digital. As imagens digitalizadas de 0, 2, 4 e 6 meses, foram importadas para o programa VixWin 2000 para que os limites externos das lesões periapicais nos diferentes períodos de proservação fossem delimitados por dois examinadores. As imagens geradas pela subtração digital também foram levadas para o programa VixWin 2000 para que as áreas das alterações radiográficas fossem delimitadas pelos examinadores. Os resultados mostraram uma correlação não significante entre as medidas das áreas de reparação ou perda óssea detectadas pelos dois programas (o coeficiente de correlação intraclasse variou de 0,02 a 0,45)... (Resumo completo, clicar acesso eletrônico abaixo) Abstract: The aim of this study was to evaluate the radiographics changes of periapical lesions in the follow-up periods of 0, 2, 4 and 6 months after endodontic treatment using digital subtracted radiography in the software Adobe Photoshop 6.0 and by delimiting yours edges with a pointing device in the software VixWin 2000. The comparison of the areas of repair or bone loss visualized in the two softwares was also evaluated. It were used 13 human teeth with no pulp vitality and chronic periapical lesion that were root canal treated. After the root canal treatment standardized periapical radiographs were obtained immediately postoperatively and at 2, 4, and 6 months using individualized silicone bit blocks and Rinn XCP film holder. Each periapical radiographs were automatic processing, digitized by a scanner and then subtracted. The digitized radiographic images of 0, 2, 4 and 6 months after root canal treatment were imported to the software VixWin 2000 in order to the edges of the periapical lesions were drawn with a pointing device for two examiners. The subtracted digital images were also imported to the software VixWin 2000 in order to the areas of repair or bone loss were drawn by the examiners. The results showed no significant correlation between the measure of the areas of repair or bone loss visualized in the two softwares (the intraclass correlation coefficient varied from 0,02 to 0,45). The results of interexaminer assessment demonstrated a significant correlation between the measure of the areas of repair or bone loss detected by the two examiners in the softwares (the intraclass correlation coefficient varied from 0,82 to 0,99). The bone repair was detected in all periodos of follow-up, been more evident in the period from the final of root canal tretament and two months of follow-up. Mestre

APA, Harvard, Vancouver, ISO, and other styles

28

Irrera, Paolo. "Traitement d'images de radiographie à faible dose : Débruitage et rehaussement de contraste conjoints et détection automatique de points de repère anatomiques pour l'estimation de la qualité des images." Thesis, Paris, ENST, 2015. http://www.theses.fr/2015ENST0031/document.

Full text

Abstract:

Nos travaux portent sur la réduction de la dose de rayonnement lors d'examens réalisés avec le Système de radiologie EOS. Deux approches complémentaires sont étudiées. Dans un premier temps, nous proposons une méthode de débruitage et de rehaussement de contraste conjoints pour optimiser le compromis entre la qualité des images et la dose de rayons X. Nous étendons le filtre à moyennes non locales pour restaurer les images EOS. Nous étudions ensuite comment combiner ce filtre à une méthode de rehaussement de contraste multi-échelles. La qualité des images cliniques est optimisée grâce à des fonctions limitant l'augmentation du bruit selon la quantité d’information locale redondante captée par le filtre. Dans un deuxième temps, nous estimons des indices d’exposition (EI) sur les images EOS afin de donner aux utilisateurs un retour immédiat sur la qualité de l'image acquise. Nous proposons ainsi une méthode reposant sur la détection de points de repère qui, grâce à l'exploitation de la redondance de mesures locales, est plus robuste à la présence de données aberrantes que les méthodes existantes. En conclusion, la méthode de débruitage et de rehaussement de contraste conjoints donne des meilleurs résultats que ceux obtenus par un algorithme exploité en routine clinique. La qualité des images EOS peut être quantifiée de manière robuste par des indices calculés automatiquement. Étant donnée la cohérence des mesures sur des images de pré-affichage, ces indices pourraient être utilisés en entrée d'un système de gestion automatique des expositions We aim at reducing the ALARA (As Low As Reasonably Achievable) dose limits for images acquired with EOS full-body system by means of image processing techniques. Two complementary approaches are studied. First, we define a post-processing method that optimizes the trade-off between acquired image quality and X-ray dose. The Non-Local means filter is extended to restore EOS images. We then study how to combine it with a multi-scale contrast enhancement technique. The image quality for the diagnosis is optimized by defining non-parametric noise containment maps that limit the increase of noise depending on the amount of local redundant information captured by the filter. Secondly, we estimate exposure index (EI) values on EOS images which give an immediate feedback on image quality to help radiographers to verify the correct exposure level of the X-ray examination. We propose a landmark detection based approach that is more robust to potential outliers than existing methods as it exploits the redundancy of local estimates. Finally, the proposed joint denoising and contrast enhancement technique significantly increases the image quality with respect to an algorithm used in clinical routine. Robust image quality indicators can be automatically associated with clinical EOS images. Given the consistency of the measures assessed on preview images, these indices could be used to drive an exposure management system in charge of defining the optimal radiation exposure

APA, Harvard, Vancouver, ISO, and other styles

29

Chapple, Claire Louise. "The optimisation of radiation dose in paediatric radiology." Thesis, University of Newcastle Upon Tyne, 1998. http://hdl.handle.net/10443/497.

Full text

Abstract:

The importance of monitoring, and where possible reducing, the level of radiation dose from diagnostic X-ray examinations has been recognised for many years and is becoming of increasing concern. Dose reduction is of particular concern in paediatric radiology, and there are specific problems associated with the monitoring and comparison of radiation doses to children. Any optimisation study relies on a framework of good dosimetry. Two techniques have been developed to improve the collection of patient dose data: the automation of survey techniques to increase the quantity of data collected; and a method of correcting for patient size which reduces one source of variability in the data. An optimisation strategy has been developed, consisting of theoretical simulations, experimental verification and clinical implementation. Monte Carlo techniques were used for the theoretical study, which investigated the effect of beam filtration on radiation dose and image quality for a wide range of parameters, specifically for a neonatal size phantom. Simulations included both radiography of bone in soft tissue and fluoroscopy of iodine and barium based contrast media. The results were assessed in terms of the beam spectra and the absorption and transmission characteristics of the phantom and image receptor. Experimental measurements of dose and contrast were made for a simple slab phantom corresponding to that simulated, and results showed good agreement with those predicted. A further set of experimental measurements were carried out using anthropomorphic phantoms in a clinical setting, which demonstrated how the theoretical predictions translated to clinical practice. A clinical trial of the use of a 0.1mm copper filter for fluoroscopic examinations of infants was performed, and the filter shown to give substantial dose reduction with no significant loss in image quality. Some general recommendations on dose quantities and the application of optimisation strategies to paediatric radiology have been made.

APA, Harvard, Vancouver, ISO, and other styles

30

Lester, Sonia. "A study of scattered radiation in diagnostic radiology using Monte Carlo simulation." Thesis, Institute of Cancer Research (University Of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287993.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Elgamri, Alya Isam Eldin Gafar. "A Comparison of the dental age estimation methods of Phillips and Proffit in a sample of South African children at the Tygerberg Dental Faculty." University of the Western Cape, 2015. http://hdl.handle.net/11394/5036.

Full text

Abstract:

Magister Scientiae Dentium - MSc(Dent) Background: Dental age is an indicator of the physiological maturity of growing children. Different methods for estimating the dental age in comparison to the chronological age were proposed in the literature. Objective: The aim of this study was to compare the accuracy of two methods i.e. the Phillips and Proffit methods in estimating the dental age in a sample of South African children at the Tygerberg dental faculty. Methods: A retrospective study was conducted by randomly selecting 100 panoramic radiographs with known chronological age. The sample contained an equal number of girls and boys (50 in each group) and the chronological age ranged between 6 and 11 years. Dental age for each radiograph was estimated using the Phillips and the Proffit methods respectively. The mean difference between dental and chronological age was calculated. Dental and chronological ages were compared using overall bias and random errors. Results: The results showed that for the girls’ sample, the Phillips method underestimated the age by 4 months which is statistically significant (p-value =0.03). The Proffit method underestimated the age by 2 days which is not statistically significant (p-value =0.97). Both methods however have the same frequency of random errors. For the boys’ sample, Phillips’ method underestimated the age by 6 months which is statistically significant (p-value <0.0001). Proffit’s method underestimated the age by 2 months which is not statistically significant (p-value= 0.15). The Phillips method was shown to have fewer random errors in boys. Discussion: The above mentioned results showed that for dental age estimation for girls, Proffit’s method would be more appropriate. This rationale is explained by the conclusion that it only underestimates the age by 2 days and has the same frequency of random errors as Phillips’ method. However, if one had to choose between the two methods for boys, the situation should be evaluated carefully. For boys, the Phillips method has fewer random errors but a larger overall bias (6 months) whereas Proffit’s method has more random errors but less overall bias (2 months). The choice between the two methods should therefore depend on the purpose of the estimation. If the method is used for estimating the age in a single individual with an unknown chronological age, Phillips’ method would be more preferable. However, if the method is used for age estimation in populations with a known mean chronological age, Proffit is preferred. Conclusion: Proffit’s description for dental development has been shown to be accurate in estimating the DA. It may therefore be considered to be a legitimate DA estimation method and not just a developmental description for the dentition.

APA, Harvard, Vancouver, ISO, and other styles

32

Wouters, Francis Roger. "Objective methods of recording gingivitis and marginal periodontitis in man a laser, radiography- and computer-based study of gingival swelling and interproximal alveolar bone levels /." Stockholm : Kongl. Carolinska Medico Chirurgiska Institutet, 1988. http://catalog.hathitrust.org/api/volumes/oclc/18102871.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Irrera, Paolo. "Traitement d'images de radiographie à faible dose : Débruitage et rehaussement de contraste conjoints et détection automatique de points de repère anatomiques pour l'estimation de la qualité des images." Electronic Thesis or Diss., Paris, ENST, 2015. http://www.theses.fr/2015ENST0031.

Full text

Abstract:

Nos travaux portent sur la réduction de la dose de rayonnement lors d'examens réalisés avec le Système de radiologie EOS. Deux approches complémentaires sont étudiées. Dans un premier temps, nous proposons une méthode de débruitage et de rehaussement de contraste conjoints pour optimiser le compromis entre la qualité des images et la dose de rayons X. Nous étendons le filtre à moyennes non locales pour restaurer les images EOS. Nous étudions ensuite comment combiner ce filtre à une méthode de rehaussement de contraste multi-échelles. La qualité des images cliniques est optimisée grâce à des fonctions limitant l'augmentation du bruit selon la quantité d’information locale redondante captée par le filtre. Dans un deuxième temps, nous estimons des indices d’exposition (EI) sur les images EOS afin de donner aux utilisateurs un retour immédiat sur la qualité de l'image acquise. Nous proposons ainsi une méthode reposant sur la détection de points de repère qui, grâce à l'exploitation de la redondance de mesures locales, est plus robuste à la présence de données aberrantes que les méthodes existantes. En conclusion, la méthode de débruitage et de rehaussement de contraste conjoints donne des meilleurs résultats que ceux obtenus par un algorithme exploité en routine clinique. La qualité des images EOS peut être quantifiée de manière robuste par des indices calculés automatiquement. Étant donnée la cohérence des mesures sur des images de pré-affichage, ces indices pourraient être utilisés en entrée d'un système de gestion automatique des expositions We aim at reducing the ALARA (As Low As Reasonably Achievable) dose limits for images acquired with EOS full-body system by means of image processing techniques. Two complementary approaches are studied. First, we define a post-processing method that optimizes the trade-off between acquired image quality and X-ray dose. The Non-Local means filter is extended to restore EOS images. We then study how to combine it with a multi-scale contrast enhancement technique. The image quality for the diagnosis is optimized by defining non-parametric noise containment maps that limit the increase of noise depending on the amount of local redundant information captured by the filter. Secondly, we estimate exposure index (EI) values on EOS images which give an immediate feedback on image quality to help radiographers to verify the correct exposure level of the X-ray examination. We propose a landmark detection based approach that is more robust to potential outliers than existing methods as it exploits the redundancy of local estimates. Finally, the proposed joint denoising and contrast enhancement technique significantly increases the image quality with respect to an algorithm used in clinical routine. Robust image quality indicators can be automatically associated with clinical EOS images. Given the consistency of the measures assessed on preview images, these indices could be used to drive an exposure management system in charge of defining the optimal radiation exposure

APA, Harvard, Vancouver, ISO, and other styles

34

Hirvasniemi, J. (Jukka). "Novel X-ray-based methods for diagnostics of osteoarthritis." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526210384.

Full text

Abstract:

Abstract Osteoarthritis (OA) is the commonest joint disease in the world, and it has a major socioeconomic impact. OA causes progressive degenerative changes in the composition and structure of articular cartilage and subchondral bone. Clinical diagnosis of OA is based on physical examination and qualitative evaluation of changes on plain radiographs. Current clinical imaging methods are subjective or insensitive to early OA changes. Therefore, new methods are needed so as to quantify composition of the cartilage and characteristics of the subchondral bone. The aim of this thesis was to evaluate the potential of clinically applicable X-ray-based methods for the assessment of the cartilage proteoglycan content as well as the structure and density of subchondral bone in a knee joint. Subchondral bone density and structure (local binary patterns, Laplacian, and fractal-based algorithms) analysis methods for two-dimensional (2-D) plain radiographs were validated against three-dimensional (3-D) bone microarchitecture obtained from micro-computed tomography ex vivo and applied to plain radiographs in vivo. Furthermore, a method developed for the evaluation of articular cartilage proteoglycan content from computed tomography (CT) was validated against a delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), which is widely used as a proteoglycan sensitive method, in subjects referred for an arthroscopy of the knee joint. Subchondral bone density and structure evaluated from 2-D radiographs were significantly related to the bone volume fraction and true 3-D microarchitecture of bone, respectively. In addition, bone density- and structure-related parameters from radiographs were significantly different among subjects with different stages of OA. Cartilage proteoglycan content evaluated from CT was significantly related to dGEMRIC method. Furthermore, dGEMRIC was associated with bone structure from a 2-D radiograph. In conclusion, analysis of bone structure and density is feasible from clinically available 2-D radiographs. A novel CT method sensitive to proteoglycan content should be considered when a 3-D view of cartilage quality is needed Tiivistelmä Nivelrikko on maailman yleisin nivelsairaus. Se aiheuttaa merkittävää kärsimystä potilaille, ja sillä on suuri taloudellinen vaikutus yhteiskuntaan. Nivelrikko aiheuttaa palautumattomia muutoksia nivelrustokudoksen ja rustonalaisen luun koostumukseen ja rakenteeseen. Nivelrikon diagnoosi perustuu kliiniseen tutkimukseen ja röntgenkuvien silmämääräiseen arviointiin. Nykyiset nivelrikon kliiniset kuvantamismenetelmät ovat subjektiivisia eivätkä riittävän tarkkoja nivelrikon varhaisten muutosten osoittamiseen, minkä vuoksi rustokudoksen koostumuksen ja rustonalaisen luun muutosten arviointiin tarvitaan uusia menetelmiä. Tämän väitöskirjantyön tarkoituksena oli tutkia uusien röntgensäteilyyn perustuvien menetelmien soveltuvuutta polvinivelen rustokudoksen proteoglykaanipitoisuuden sekä luun tiheyden ja rakenteen arviointiin. Rustonalaisen luun tiheyttä ja rakennetta arvioitiin digitaalisesta röntgenkuvasta tietokonepohjaisilla menetelmillä ja tuloksia verrattiin mikrotietokonetomografiassa nähtävään luun kolmiulotteiseen rakenteeseen. Röntgenkuvasta laskettavia muuttujia verrattiin myös eriasteisesta nivelrikosta kärsivien henkilöiden välillä. Rustokudoksen proteoglykaanipitoisuutta epäsuorasti mittaavaa tietokonetomografiamenetelmää verrattiin vastaavaan magneettikuvausmenetelmään henkilöillä, jotka olivat menossa polven niveltähystykseen. Röntgenkuvasta laskettu rustonalaisen luun tiheys ja rakenne olivat tilastollisesti selkeästi yhteydessä luun tilavuusmäärään ja mikrorakenteeseen, ja ne erosivat eriasteisesta nivelrikosta kärsivien henkilöiden välillä. Proteoglykaanipitoisuutta arvioivien tietokonetomografia- ja magneettikuvausmenetelmien välillä oli tilastollisesti merkitsevä korrelaatio. Ruston proteoglykaanipitoisuutta arvioivan magneettikuvausmenetelmän ja röntgenkuvasta laskettavan luun rakenteen välillä oli myös tilastollinen yhteys. Loppupäätelmänä voidaan todeta, että luun tiheyttä ja rakennetta on mahdollista arvioida kliinisesti saatavilla olevista röntgenkuvista. Tietokonetomografiamenetelmän käyttöä tulee harkita tutkimuksissa silloin, kun rustokudoksen tilasta halutaan kolmiulotteista tietoa

APA, Harvard, Vancouver, ISO, and other styles

35

Carvalho, Fabíola Bastos de [UNESP]. "Avaliação das alterações radiográficas após tratamento endodôntico de dentes com lesão periapical empregando dois programas de interpretação de imagens." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/90406.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:24:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-03-24Bitstream added on 2014-06-13T19:52:06Z : No. of bitstreams: 1 carvalho_fb_me_arafo.pdf: 565333 bytes, checksum: 1218d203c1a346abccf56852aac282d9 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) O objetivo desse estudo foi avaliar as alterações radiográficas de lesões periapicais, nos períodos de proservação de 0, 2, 4 e 6 meses após o tratamento endodôntico, por meio da subtração radiográfica digital realizada pelo programa Adobe Photoshop 6.0, e da demarcação de seus limites externos na tela do computador utilizando o programa VixWin 2000. E em seguida, fazer uma comparação entre as áreas de reparação ou perda óssea visualizadas nos dois programas. Foram utilizados 13 dentes anteriores de humanos com necrose pulpar e lesão periapical crônica, que foram tratados endodonticamente. Após o tratamento endodôntico, para realização da radiografia final, foi utilizada uma técnica para padronização das imagens que consistiu no uso de um posicionador para filmes radiográficos, o qual foi estabilizado com material de impressão (silicona) colocado sobre os bordos incisais dos dentes radiografados. Para as radiografias de proservação realizadas 2, 4 e 6 meses após o tratamento endodôntico foi utilizado o mesmo método. Os filmes radiográficos foram processados automaticamente, digitalizados por meio de um scanner, e em seguida feita a subtração digital. As imagens digitalizadas de 0, 2, 4 e 6 meses, foram importadas para o programa VixWin 2000 para que os limites externos das lesões periapicais nos diferentes períodos de proservação fossem delimitados por dois examinadores. As imagens geradas pela subtração digital também foram levadas para o programa VixWin 2000 para que as áreas das alterações radiográficas fossem delimitadas pelos examinadores. Os resultados mostraram uma correlação não significante entre as medidas das áreas de reparação ou perda óssea detectadas pelos dois programas (o coeficiente de correlação intraclasse variou de 0,02 a 0,45)... The aim of this study was to evaluate the radiographics changes of periapical lesions in the follow-up periods of 0, 2, 4 and 6 months after endodontic treatment using digital subtracted radiography in the software Adobe Photoshop 6.0 and by delimiting yours edges with a pointing device in the software VixWin 2000. The comparison of the areas of repair or bone loss visualized in the two softwares was also evaluated. It were used 13 human teeth with no pulp vitality and chronic periapical lesion that were root canal treated. After the root canal treatment standardized periapical radiographs were obtained immediately postoperatively and at 2, 4, and 6 months using individualized silicone bit blocks and Rinn XCP film holder. Each periapical radiographs were automatic processing, digitized by a scanner and then subtracted. The digitized radiographic images of 0, 2, 4 and 6 months after root canal treatment were imported to the software VixWin 2000 in order to the edges of the periapical lesions were drawn with a pointing device for two examiners. The subtracted digital images were also imported to the software VixWin 2000 in order to the areas of repair or bone loss were drawn by the examiners. The results showed no significant correlation between the measure of the areas of repair or bone loss visualized in the two softwares (the intraclass correlation coefficient varied from 0,02 to 0,45). The results of interexaminer assessment demonstrated a significant correlation between the measure of the areas of repair or bone loss detected by the two examiners in the softwares (the intraclass correlation coefficient varied from 0,82 to 0,99). The bone repair was detected in all periodos of follow-up, been more evident in the period from the final of root canal tretament and two months of follow-up.

APA, Harvard, Vancouver, ISO, and other styles

36

Baradi, Divyank. "Control strategies and inspection methods for welded part." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-16383.

Full text

Abstract:

Present and future demonstrator designs were used to demonstrate the quality assurance of welds. The NDT methods tested on prototype demonstrator parts are: visual inspection, radius gauges, throat size gauge, liquid-penetrant testing, magnetic particle testing and ultrasonics with pulse echo and phased array. The other methods like eddy current, time of flight diffraction, radiography, impression test, macro test and infrared thermographs are currently being analyzed along with their inspection costs. The control plans for present and future designs with corresponding present and future NDT methods are suggested to minimize a shift in process. Magnetic particle testing revealed a lack of fusion and cracks for fillet welds, whereas ultrasonic pulse echo and phased array identified an internal lack of fusion, inner pores/slag inclusions on butt welds. Ultrasonic PAUT & TOFD could be used for accurate defect identification and thermography for online identification of lack of penetration, depth of penetration and weld parameters. Weight reduction by improved weld quality (WIQ)

APA, Harvard, Vancouver, ISO, and other styles

37

Stenström, Mats. "Computerised microtomography : non-invasive imaging and analysis of biological samples, with special reference to monitoring development of osteoporosis in small animals /." Linköping : Univ, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5030.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Barros, Hilton José Melo. "Medidas radiográficas relacionadas ao risco de ocorrência de osteoartrite do quadril." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/5/5140/tde-05032010-125943/.

Full text

Abstract:

O estudo busca determinar fatores predisponentes para osteoartrite do quadril, por meio da avaliação de parâmetros radiográficos nos quadris de indivíduos idosos. Foram realizadas medições em radiografias de 106 indivíduos com idade acima de 60 anos, sendo um grupo com osteoartrite do quadril e um segundo grupo de indivíduos sem osteoartrite (grupo controle). As incidências radiográficas utilizadas foram ântero-posterior da pelve em ortostase, falso perfil de Lequesne e Dunn a 45 graus de flexão do quadril. Após aplicação de critérios de seleção bem definidos para osteoartrite primária do quadril, o número de quadris avaliados foi 112 quadris de indivíduos normais e 72 quadris de indivíduos com osteoartrite. Os parâmetros radiográficos estudados foram ângulo centro-borda de Wiberg, ângulo de Tönnis, índice acetabular de profundidade por diâmetro, percentual de cobertura da cabeça do fêmur, ângulo colo-diafisário, ângulo centro-borda anterior, offset entre a cabeça e o colo do fêmur, ângulo alfa, esfericidade da cabeça do fêmur e versão do acetábulo. As medidas radiográficas ângulo colo-diafisário, ângulo alfa, índice acetabular de profundidade por diâmetro e percentual de cobertura da cabeça do fêmur apresentaram valores médios significativamente diferentes nos pacientes com osteoartrite primária, quando comparados aos do grupo controle, sugerindo serem fatores predisponentes para a osteoartrite do quadril This study aimed to determine factors that predispose towards hip osteoarthritis, by means of evaluating the radiographic parameters of elderly individuals hips. Radiographic measurements were made on 106 individuals aged 60 years or over: one group with hip osteoarthritis and another group of individuals without osteoarthritis (control group). The radiographic views used were the antero-posterior view of the pelvis in orthostatic position, Lequesnes false profile and Dunns view with 45 degrees of hip flexion. After applying well-defined selection criteria for primary osteoarthritis of the hip, the numbers of hips evaluated were 112 hips from normal individuals and 72 hips from individuals with osteoarthritis. The radiographic parameters studied were the Wiberg center-edge angle, Tönnis angle, acetabular index of depth to diameter, percentage coverage of the femoral head, neck-shaft angle, anterior center-edge angle, femoral neck-head offset, alpha angle, sphericity of the femoral head and acetabular version. The radiographic measurements of the neck-shaft angle, alpha angle, acetabular index of depth to diameter and percentage coverage of the femoral head presented mean values that were significantly different between the patients with idiopathic osteoarthritis and the control group. This suggests that these factors may predispose towards hip osteoarthritis

APA, Harvard, Vancouver, ISO, and other styles

39

Wheeler, Mark Lee. "A comparative study of art and the convolution method as applied to cross borehole geophysical tomography." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183124445.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Long, Deirdré. "An analysis of dose effectiveness and incidence of late rectal complications of high dose-rate brachytherapy in the radical treatment of cervical cancer." Thesis, Bloemfontein : Central University of Technology, Free State, 2007. http://hdl.handle.net/11462/94.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Lopresti, Mattia. "Non-destructive X-ray based characterization of materials assisted by multivariate methods of data analysis: from theory to application." Doctoral thesis, Università del Piemonte Orientale, 2022. http://hdl.handle.net/11579/143020.

Full text

Abstract:

X-ray based non-destructive techniques are an increasingly important tool in many fields, ranging from industry to fine arts, from medicine to basic research. Over the last century, the study of the physical phenomena underlying the interaction between X-rays and matter has led to the development of many different techniques suitable for morphological, textural, elementary, and compositional analysis. Furthermore, with the development of the hardware technology and its automation thanks to IT advancements, enormous progress has been made also from the point of view of data collection and nowadays it is possible to carry out measurement campaigns by collecting many GigaBytes of data in a few hours. Already huge data sets are further enlarged when samples are analyzed with a multi-technique approach and/or at in situ conditions with time, space, temperature, and concentration becoming additional variables. In the present work, new data collection and analysis methods are presented along with applicative studies in which innovative materials have been developed and characterized. These materials are currently of high application interest and involve composites for radiation protection, ultralight magnesium alloys and eutectic mixtures. The new approaches have been grown up from an instrumental viewpoint and with regard to the analysis of the data obtained, for which the use and development of multivariate methods was central. In this context, extensive use has been made of principal component analysis and experimental design methods. One prominent topic of the study involved the development of in situ analysis methods of evolving samples as a response to different types of gradients. In fact, while in large structures such as synchrotrons carrying out analyzes under variable conditions is now consolidated practice, on a laboratory scale this type of experiments is still relatively young and the methods of data analysis of data sets evolving systems have large perspectives for development especially, if integrated by multivariate methods.

APA, Harvard, Vancouver, ISO, and other styles

42

Mukkananchery, Abey. "Iterative Methods for the Reconstruction of Tomographic Images with Unconventional Source-detector Configurations." VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1244.

Full text

Abstract:

X-ray computed tomography (CT) holds a critical role in current medical practice for the evaluation of patients, particularly in the emergency department and intensive care units. Expensive high resolution stationary scanners are available in radiology departments of most hospitals. In many situations however, a small, inexpensive, portable CT unit would be of significant value. Several mobile or miniature CT scanners are available, but none of these systems have the range, flexibility or overall physical characteristics of a truly portable device. The main challenge is the design of a geometry that optimally trades image quality for system size. The goal of this work has been to develop analysis tools to help simulate and evaluate novel system geometries. To test the tools we have developed, three geometries have been considered in the thesis, namely, parallel projections, clam-shell and parallel plate geometries. The parallel projections geometry is commonly used in reconstruction of images by filtered back projection technique. A clam-shell structure consists of two semi-cylindrical braces that fold together over the patient's body and connect at the top. A parallel plate structure uses two fixed flat or curved plates on either side of the patient's body and image from fixed sources/detectors that are gated on and off so as to step the X-ray field through the body. The parallel plate geometry has been found to be the least reliable of the three geometries investigated, with the parallel projections geometry being the most reliable. For the targeted application, the clam-shell geometry seems to be the solution with more chances to succeed in the short term. We implemented the Van Cittert iterative technique for the reconstruction of images from projections. The thesis discusses a number of variations on the algorithm, such as the use of the Conjugate Gradient Method, several choices for the initial guess, and the incorporation of a priori information to handle the reconstruction of images with metal inserts.

APA, Harvard, Vancouver, ISO, and other styles

43

Spencer, Benjamin. "On-line C-arm intrinsic calibration by means of an accurate method of line detection using the radon transform." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAS044/document.

Full text

Abstract:

Les ``C-arm'' sont des systémes de radiologie interventionnelle fréquemment utilisés en salle d'opération ou au lit du patient. Des images 3D des structures anatomiques internes peuvent être calculées à partir de multiples radiographies acquises sur un ``C-arm mobile'' et isocentrique décrivant une trajectoire généralement circulaire autour du patient. Pour cela, la géométrie conique d'acquisition de chaque radiographie doit être précisément connue. Malheureusement, les C-arm se déforment en général au cours de la trajectoire. De plus leur motorisation engendre des oscillations non reproductibles. Ils doivent donc être calibrés au cours de l'acquisition. Ma thèse concerne la calibration intrinsèque d'un C-arm à partir de la détection de la projection du collimateur de la source dans les radiographies.Nous avons développé une méthode de détection de la projection des bords linéaires du collimateur. Elle surpasse les méthodes classiques comme le filtre de Canny sur données simulées ou réelles. La précision que nous obtenons sur l'angle et la position (phi,s) des droites est de l'ordre de: phi{RMS}=+/- 0.0045 degrees et s{RMS}=+/- 1.67 pixels. Nous avons évalué nos méthodes et les avons comparés à des méthodes classiques de calibration dans le cadre de la reconstruction 3D Mobile isocentric x-ray C-arm systems are an imaging tool used during a variety of interventional and image guided procedures. Three-dimensional images can be produced from multiple projection images of a patient or object as the C-arm rotates around the isocenter provided the C-arm geometry is known. Due to gravity affects and mechanical instabilities the C-arm source and detector geometry undergo significant non-ideal and possibly non reproducible deformation which requires a process of geometric calibration. This research investigates the use of the projection of the slightly closed x-ray tube collimator edges in the image field of view to provide the online intrinsic calibration of C-arm systems.A method of thick straight edge detection has been developed which outperforms the commonly used Canny filter edge detection technique in both simulation and real data investigations. This edge detection technique has exhibited excellent precision in detection of the edge angles and positions, (phi,s), in the presence of simulated C-arm deformation and image noise: phi{RMS} = +/- 0.0045 degrees and s{RMS} = +/- 1.67 pixels. Following this, the C-arm intrinsic calibration, by means of accurate edge detection, has been evaluated in the framework of 3D image reconstruction

APA, Harvard, Vancouver, ISO, and other styles

44

Silva, Rita de Cássia de Lima. "Avaliação do uso de detectores finos para a produção de imagem com feixes de prótons." Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/299.

Full text

Abstract:

CAPES Desde os primeiros trabalhos propondo o uso dos prótons para a construção da imagem, a principal vantagem, sobre os raios X, foi esperada como um resultado da propriedade específica do fluxo de próton em diminuir acentuadamente no fim do alcance da partícula. Esta ideia foi declarada, porém não foi checada. No presente trabalho, esta hipótese foi investigada usando simulação Monte Carlo, com o auxílio do software SRIM-2008, para o caso de um detector que registra pequena parte da energia de saída do próton (detector fino). Primeiramente, foi determinada a espessura do detector para a investigação da perda de energia dos prótons em um objeto de água com 20 cm. Foi estudada a dose absorvida necessária para distinguir dois objetos de água com espessura de 20 cm e 20,1 cm, como função da energia inicial. O resultado foi comparado com os dados obtidos por um detector grosso, que registra energia total de saída. A investigação realizada mostrou que a ideia principal de se trabalhar no fim de alcance dos prótons para a construção da imagem, não é correta quando se utiliza detector fino bem como detector grosso. Em geral, os sistemas de detecção, baseados em medidas de energia total de saída, são preferíveis àqueles que se baseiam em detectores finos. Since the earliest works proposing the use of protons for imaging, the main advantage of protons over X-rays was expected to be a result of the specific property of the proton flux dropping off very steeply at the end of the particle range. This idea was declared but was not checked. In the present work, this assumption was investigated using the Monte Carlo simulation, with the help of SRIM-2008 software, for the case of a detector that registers only a small part of the proton exit energy (thin detector). First, a thickness of such detector was determined for the investigated water object of 20 cm. Then, it was studied the minimum dose absorbed by an object that is necessary to distinguish two water objects with the thicknesses of 20 cm and 20.1 cm as a function of the initial energy. The results were compared with the case of thick detector that registers the total exit energy. The carried out investigation shows that the principal idea of proton imaging to work near the end of the proton range is not correct in the case of thin detector as well as for thick one. In general, detector systems based on the measurement of the total exit energy are preferable to systems based on thin detectors.

APA, Harvard, Vancouver, ISO, and other styles

45

Kocich, Tomáš. "Komplexní diagnostika konstrukce bytového domu před rekonstrukcí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225417.

Full text

Abstract:

This thesis deals with the diagnosis of a residential building from the late nineteen twenties for the needs of reconstruction. The methods generally used in the diagnosis of structures are briefly described in the theoretical part. More deeply this section describes the methods that were used during this particular research. The practical part deals with the diagnosis of the object itself. The first section describes the layout of the villa, its design solution, its faults and defects detected during the inspection. The next section deals with evaluating the current state of construction materials. Static reports of several structural parts were calculated in the last section.

APA, Harvard, Vancouver, ISO, and other styles

46

Langet, Hélène. "Sampling and Motion Reconstruction in Three-dimensional X-ray Interventional Imaging." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00845148.

Full text

Abstract:

Medical imaging has known great advances over the past decades to become a powerful tool for the clinical practice. It has led to the tremendous growth of interventional radiology, in which medical devices are inserted and manipulated under image guidance through the vascular system to the pathology location and then used to deliver the therapy. In these minimally-invasive procedures, X-ray guidance is carried out with C-arm systems through two-dimensional real-time projective low-dose images. More recently, three-dimensional visualization via tomographic acquisition has also become available. This work tackles tomographic reconstruction in the aforementioned context. More specifically, it deals with the correction of motion artifacts that originate from the temporal variations of the contrast-enhanced vessels and thus tackles a central aspect of tomography: data (angular) sampling. The compressed sensing theory identifies conditions under which subsampled data can be recovered through the minimization of a least-square data fidelity term combined with sparse constraints. Relying on this theory, an original reconstruction framework is proposed based on iterative filtered backprojection, proximal splitting, '1-minimization and homotopy. This framework is derived for integrating several spatial and temporal penalties. Such a strategy is shown to outperform the analytical filtered backprojection algorithm that is used in the current clinical practice by reducing motion and sampling artifacts in well-identified clinical cases, with focus on cerebral and abdominal imaging. The obtained results emphasize one of the key contributions of this work that is the importance of homotopy in addition to regularization, to provide much needed image quality improvement in the suggested domain of applicability.

APA, Harvard, Vancouver, ISO, and other styles

47

Reis, Lucas Paixão. "Metodologia para geração de modelos de mama com distribuição espacial de tecido glandular." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2015. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=349.

Full text

Abstract:

A mamografia é a principal técnica radiográfica utilizada para imagens das mamas. A mama é um órgão radio-sensível e existe um risco de câncer induzido pela radiação associado com a mamografia. A dose glandular média (DG) é a grandeza dosimétrica aceita para caracterizar o risco de câncer induzido pela radiação. Estudos anteriores concluíram que a DG depende não somente do conteúdo glandular, mas também da distribuição do tecido glandular dentro da mama. Neste trabalho, é proposto um novo método para a geração de modelos computacionais de mama com tecido epitelial e distribuição espacial do tecido glandular de pacientes submetidos a exames de mamografia digital. Cento e setenta modelos computacionais de mama com diferentes glandularidades foram simulados e os resultados foram comparados com valores de coeficientes de conversão para DG recomendados. As diferenças encontradas sugerem que os coeficientes de conversão recomendados internacionalmente podem superestimar a dose glandular média para mamas menos densas e subestimar a dose glandular média para as mamas mais densas. A metodologia descrita neste trabalho constitui uma ferramenta poderosa para a dosimetria em mamografia, principalmente para estudos de risco. Mammography is the main radiographic technique used for breast imaging. A major concern with mammographic imaging is the risk of radiation-induced breast cancer due to the high sensitivity of breast tissue. The mean glandular dose (DG) is the dosimetric quantity widely accepted to characterize the risk of radiation induced cancer. Previous studies have concluded that DG depends not only on the breast glandular content but also on the spatial distribution of glandular tissue within the breast. In this work, a new method for generating breast models featuring skin composition and glandular tissue distribution from patients undergoing digital mammography is proposed. A hundred and seventy breast models with different breast glandularity were simulated and the results were compared with those obtained from recommended DG conversion factors. The results show that the internationally recommended conversion factors may be overestimating the mean glandular dose to less dense breasts and underestimating the mean glandular dose for denser breasts. The methodology described in this work constitutes a powerful tool for breast dosimetry, especially for risk studies.

APA, Harvard, Vancouver, ISO, and other styles

48

Miguel, Omar Ferreira. "Avaliação radiográfica comparativa de quadris dolorosos e sem dor em indivíduos adultos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/5/5140/tde-04112010-151612/.

Full text

Abstract:

O objetivo do estudo foi correlacionar a presença de alterações radiográficas em quadris de pacientes portadores de dor no quadril a um grupo de pacientes sem dor no quadril. Foram avaliados 122 pacientes com dor no quadril, e 100 pacientes sem dor no quadril. Todos com idade entre 20 e 50 anos. Os pacientes foram submetidos a exames radiográficos, nas incidências AP de pelve ortostático, falso perfil de Lequesne, Dunn, Dunn 45° e Ducroquet. Os parâmetros avaliados foram inclinação e versão acetabular, ângulo CE de Wiberg, espaço articular superolateral, ângulo , ângulo de Lequesne, ângulo VCA, diferença entre o raio da cabeça e do colo femorais (off set), esfericidade da cabeça femoral e a presença de ressalto na transição da cabeça com o colo femoral. Concluiu-se que as melhores incidências para o diagnóstico de impacto femoroacetabular são AP de pelve ortostático, Dunn 45° e Ducroquet, e que as seguintes alterações estão correlacionadas com dor nos quadris: off set diminuído, ângulo aumentado, ângulo de Lequesne aumentado, ângulo CE de Wiberg diminuído, espaço articular diminuído e presença de ressalto na transição cabeça-colo femoral This study aimed to compare two groups of patients, with and with out hip pain, and correlate them with the existence of radiograph alterations. Weve studied 122 patients with hip pain and 100 asymptomatic; the ages were between 20 to 50 years old in both groups. All patients were roentnographicaly studied in anteroposterior pelvis in orthostatic position, Lequesne false profile, Dunns, Dunns 45° and Ducroquets view. The radiograph parameters analized were the acetabular inclination and vertion, Wiberg CE angle, Lequesne VCA angle, Lequesnes antevertion angle (), angle, superior and lateral joint space, femoral off set, nonspherical of the femoral head and the presence of a bump on the head-neck transition. We conclude that the best incidences to diagnosis of femoroacetabular impingement are AP pelvis orthostatic, Dunn 45° and Ducroquet. The following alterations are correlate with hip pain: lower off set, higher angle, higher Lequesne angle, lower CE angle of Wiberg, lower articular space and bump in the femoral head-neck transition

APA, Harvard, Vancouver, ISO, and other styles

49

Silva, André Goyanna Pinheiro. "Tratamento endovascular das fístulas carotidocavenosas indiretas." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/5/5151/tde-16102014-094552/.

Full text

Abstract:

As fístulas arteriovenosas da região do seio cavernoso constituem as fístulas carotidocavernosas que podem ser diretas ou indiretas. As indiretas são raras, a sua sintomatologia é variada e o tratamento é controverso. Este estudo compreendeu a análise prospectiva de 44 pacientes portadores de fístulas carotidocavernosas indiretas (FCCI) no período de 01 de janeiro de 1994 e 31 de janeiro de 2004, 42 com etiologia espontânea e dois pacientes com etiologia traumática, sendo estes analisados separadamente. Doze (12) pacientes foram submetidos à conduta expectante e orientados a realizar manobras de compressão carótido-jugular. O tratamento endovascular foi realizado por via arterial, venosa ou combinação dos dois, num total de 30 pacientes. Considerando o grupo inteiro, ocorreu trombose espontânea em aproximadamente 24% dos pacientes. Os sintomas e o aspecto angiográfico após o tratamento evoluíram com melhora ou cura em 100% dos casos, com oclusão completa das FCCI em 63,3%, a grande maioria destes submetidos a apenas um procedimento. Além dos acessos venosos tradicionais aos seios cavernosos, vias de acesso alternativas através da veia oftálmica superior foram realizadas por punção percutânea de veia facial, veia supratroclear ou veia frontal. O material embolizante mais utilizado foi o adesivo tissular líquido, \"cola\", isoladamente ou em conjunto com outros materiais. Houve complicações transitórias em 13,3% dos pacientes tratados e nenhuma complicação permanente foi observada, o que demonstrou a baixa morbidade deste procedimento The arteriovenous fistulas of the cavernous sinus (CS) region constitute the carotid-cavernous fistula, which can be direct or indirect. The indirect type is quite rare, its clinical features is very inespecific and its treatment modalities controversial. Forty-four patients with indirect carotid-cavernous fistulas (ICCF) were studied in a prospective manner between January 1994 to January 2004, 42 with spontaneous etiology and 2 with traumatic etiology, being these analyzed separately. Twelve (12) patients were submitted to a expectant management and instructed to perform carotid-jugular compression. Endovascular treatment was accomplished by arterial approach, vein approach or combination of both, in a total of 30 patients. Considering the entire group, spontaneous thrombosis was observed in approximately 24%. Symptoms and the angiographic features after endovascular treatment improved or disappeared in 100% of the cases, with total obliteration in 63.3%, most of them submitted to just one procedure. Despite the traditional venous routes to the CS, alternative accesses through the superior ophthalmic vein (SOV) were accomplished by percutaneous puncture of the facial, supratrochlear or frontal vein. Liquid adhesive (glue) was the most often embolic material used isolated or with other materials. No permanent complication was observed and only 13,3% of the patients treated cursed with transitory complications, what demonstrated the low morbidity of this procedure

APA, Harvard, Vancouver, ISO, and other styles

50

Marciano, Abraham. "Méthodes d'Analyse et de Recalage d'images radiographiques de fret et de Véhicules." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLED040/document.

Full text

Abstract:

La société contemporaine fait face à un niveau de menace sans précédent depuis la seconde guerre mondiale. La lutte contre le trafic illicite mobilise aussi l’ensemble desorganes de police, visant à endiguer le financement du crime organisé. Dans cet effort, les autorités s’engagent à employer des moyens de plus en plus modernes, afin notamment d’automatiser les processus d’inspection. L’objectif de cette étude est de développer des outils de vision par ordinateur afin d’assister les officiers de douanes dans la détection d’armes et de narcotiques. Letravail présenté examine l’emploi de techniques avancées de classification et de recalage d’images pour l’identification d’irrégularités dans des acquisitions radiographiques de fret. Plutôt que de recourir à la reconnaissance par apprentissage, nos méthodes revêtent un intérêt particulier lorsque les objets ciblés présentent des caractéristiques visuelles variées. De plus, elles augmentent notablement la détectabilité d’éléments cachés dans des zones denses, là où même les algorithmes de reconnaissance n’identifieraient pas d’anomalie. Nos travaux détaillent l’état de l’art des méthodes de classification et de recalage, explorant aussi diverses pistes de résolution. Les algorithmes sont testés sur d’importantes bases de données pour apprécier visuellement et numériquement leurs performances Our societies, faced with an unprecedented level of security threat since WWII, must provide fast and adaptable solutions to cope with a new kind of menace. Illicit trade also, oftencorrelated with criminal actions, is viewed as a defining stake by governments and agencies. Enforcement authorities are thus very demandingin terms of technological features, asthey explicitly aim at automating inspection processes. The main objective of our research is to develop assisting tools to detect weapons and narcotics for lawenforcement officers. In the present work, we intend to employ and customize both advanced classification and image registration techniques for irregularity detection in X-ray cargo screening scans. Rather than employing machine-learning recognition techniques, our methods prove to be very efficient while targeting a very diverse type of threats from which no specific features can be extracted. Moreover, the proposed techniques significantly enhance the detection capabilities for law-enforcement officers, particularly in dense regions where both humans or trained learning models would probably fail. Our work reviews state-of-the art methods in terms of classification and image registration. Various numerical solutions are also explored. The proposed algorithms are tested on a very large number ofimages, showing their necessity and performances both visually and numerically

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Radiographic Method'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles