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Статті в журналах з теми "Low radiation images"
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Ismail, Susilo Widodo, and Konstantin Brazovskiy. "Spatial resolution and noise measurement of low-dose CT ACR phantom images." Journal of Physics: Conference Series 2945, no. 1 (January 1, 2025): 012013. https://doi.org/10.1088/1742-6596/2945/1/012013.
Повний текст джерелаАнотація:
Abstract Computed tomography (CT) is an instrument that is still widely used to diagnose and evaluate patient conditions from images produced by the CT scan process. CT scan images are formed from X-ray beams that penetrate the patient’s body and are captured by a detector and then displayed on a monitor screen. A fairly high dose of X-ray radiation is required to produce images with high resolution, good contrast, and low noise. However, this is contrary to the principles of ALARA, as low as reasonably achievable, and patient safety by using high-dose radiation. Various efforts to reduce the dose of X-ray radiation have been made. One of which is to use a low dose by operating the X-ray CT-scan machine at low voltage. Still, the consequence is that the resulting CT scan image has greater noise and lower spatial resolution compared to the image produced from the full radiation dose. This research measured spatial resolution by its modulation transfer function (MTF) and noise on open-source images taken at 25% dose by operating a 50-kV x-ray CT-scan machine on ACR phantom images using the IndoQCT application. The results are the noise of 25% dose images has an average of 86.71% greater and 41.96% lower spatial resolution than full-dose images. These results show that there are problems in using low-dose CT scans and open up opportunities to solve this problem by image reconstruction or image processing.
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Sathishkumar, B. S., and G. Nagarajan. "An efficient algorithm for computer tomography in low radiation images." Advances in Modelling and Analysis B 61, no. 4 (December 30, 2018): 189–97. http://dx.doi.org/10.18280/ama_b.610403.
Повний текст джерела
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Woeltjen, Matthias Michael, Julius Henning Niehoff, Arwed Elias Michael, Sebastian Horstmeier, Christoph Moenninghoff, Jan Borggrefe, and Jan Robert Kroeger. "Low-Dose High-Resolution Photon-Counting CT of the Lung: Radiation Dose and Image Quality in the Clinical Routine." Diagnostics 12, no. 6 (June 11, 2022): 1441. http://dx.doi.org/10.3390/diagnostics12061441.
Повний текст джерелаАнотація:
This study aims to investigate the qualitative and quantitative image quality of low-dose high-resolution (LD-HR) lung CT scans acquired with the first clinical approved photon counting CT (PCCT) scanner. Furthermore, the radiation dose used by the PCCT is compared to a conventional CT scanner with an energy-integrating detector system (EID-CT). Twenty-nine patients who underwent a LD-HR chest CT scan with dual-source PCCT and had previously undergone a LD-HR chest CT with a standard EID-CT scanner were retrospectively included in this study. Images of the whole lung as well as enlarged image sections displaying a specific finding (lesion) were evaluated in terms of overall image quality, image sharpness and image noise by three senior radiologists using a 5-point Likert scale. The PCCT images were reconstructed with and without a quantum iterative reconstruction algorithm (PCCT QIR+/−). Noise and signal-to-noise (SNR) were measured and the effective radiation dose was calculated. Overall, image quality and image sharpness were rated best in PCCT (QIR+) images. A significant difference was seen particularly in image sections of PCCT (QIR+) images compared to EID-CT images (p < 0.005). Image noise of PCCT (QIR+) images was significantly lower compared to EID-CT images in image sections (p = 0.005). In contrast, noise was lowest on EID-CT images (p < 0.001). The PCCT used significantly less radiation dose compared to the EID-CT (p < 0.001). In conclusion, LD-HR PCCT scans of the lung provide better image quality while using significantly less radiation dose compared to EID-CT scans.
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Horenko, Illia, Lukáš Pospíšil, Edoardo Vecchi, Steffen Albrecht, Alexander Gerber, Beate Rehbock, Albrecht Stroh, and Susanne Gerber. "Low-Cost Probabilistic 3D Denoising with Applications for Ultra-Low-Radiation Computed Tomography." Journal of Imaging 8, no. 6 (May 31, 2022): 156. http://dx.doi.org/10.3390/jimaging8060156.
Повний текст джерелаАнотація:
We propose a pipeline for synthetic generation of personalized Computer Tomography (CT) images, with a radiation exposure evaluation and a lifetime attributable risk (LAR) assessment. We perform a patient-specific performance evaluation for a broad range of denoising algorithms (including the most popular deep learning denoising approaches, wavelets-based methods, methods based on Mumford–Shah denoising, etc.), focusing both on accessing the capability to reduce the patient-specific CT-induced LAR and on computational cost scalability. We introduce a parallel Probabilistic Mumford–Shah denoising model (PMS) and show that it markedly-outperforms the compared common denoising methods in denoising quality and cost scaling. In particular, we show that it allows an approximately 22-fold robust patient-specific LAR reduction for infants and a 10-fold LAR reduction for adults. Using a normal laptop, the proposed algorithm for PMS allows cheap and robust (with a multiscale structural similarity index >90%) denoising of very large 2D videos and 3D images (with over 107 voxels) that are subject to ultra-strong noise (Gaussian and non-Gaussian) for signal-to-noise ratios far below 1.0. The code is provided for open access.
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Li, Lu-Lu, Huang Wang, Jian Song, Jin Shang, Xiao-Ying Zhao, and Bin Liu. "A feasibility study of realizing low-dose abdominal CT using deep learning image reconstruction algorithm." Journal of X-Ray Science and Technology 29, no. 2 (March 11, 2021): 361–72. http://dx.doi.org/10.3233/xst-200826.
Повний текст джерелаАнотація:
OBJECTIVES: To explore the feasibility of achieving diagnostic images in low-dose abdominal CT using a Deep Learning Image Reconstruction (DLIR) algorithm. METHODS: Prospectively enrolled 47 patients requiring contrast-enhanced abdominal CT scans. The late-arterial phase scan was added and acquired using lower-dose mode (tube current range, 175–545 mA; 80 kVp for patients with BMI ≤24 kg/m2 and 100 kVp for patients with BMI > 24 kg/m2) and reconstructed with DLIR at medium setting (DLIR-M) and high setting (DLIR-H), ASIR-V at 0% (FBP), 40% and 80% strength. Both the quantitative measurement and qualitative analysis of the five types of reconstruction methods were compared. In addition, radiation dose and image quality between the early-arterial phase ASIR-V images using standard-dose and the late-arterial phase DLIR images using low-dose were compared. RESULTS: For the late-arterial phase, all five reconstructions had similar CT value (P > 0.05). DLIR-H, DLIR-M and ASIR-V80% images significantly reduced the image noise and improved the image contrast noise ratio, compared with the standard ASIR-V40% images (P < 0.05). ASIR-V80% images had undesirable image characteristics with obvious “waxy” artifacts, while DLIR-H images maintained high spatial resolution and had the highest subjective image quality. Compared with the early-arterial scans, the late-arterial phase scans significantly reduced the radiation dose (P < 0.05), while the DLIR-H images exhibited lower image noise and good display of the specific image details of lesions. CONCLUSIONS: DLIR algorithm improves image quality under low-dose scan condition and may be used to reduce the radiation dose without adversely affecting the image quality.
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Wu, Dan, Gang Wang, Bingyang Bian, Zhuohang Liu, and Dan Li. "Benefits of Low-Dose CT Scan of Head for Patients With Intracranial Hemorrhage." Dose-Response 19, no. 1 (January 1, 2020): 155932582090977. http://dx.doi.org/10.1177/1559325820909778.
Повний текст джерелаАнотація:
Objectives: For patients with intracranial hemorrhage (ICH), routine follow-up computed tomography (CT) scans are typically required to monitor the progression of intracranial pathology. Remarkable levels of radiation exposure are accumulated during repeated CT scan. However, the effects and associated risks have still remained elusive. This study presented an effective approach to quantify organ-specific radiation dose of repeated CT scans of head for patients with ICH. We also indicated whether a low-dose CT scan may reduce radiation exposure and keep the image quality highly acceptable for diagnosis. Methods: Herein, 72 patients with a history of ICH were recruited. The patients were divided into 4 groups and underwent CT scan of head with different tube current–time products (250, 200, 150, and 100 mAs). Two experienced radiologists visually rated scores of quality of images according to objective image noise, sharpness, diagnostic acceptability, and artifacts due to physiological noise on the same workstation. Organ-/tissue-specific radiation doses were analyzed using Radimetrics. Results: In conventional CT scan group, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of ICH images were significantly higher than those in normal brain structures. Reducing the tube current–time product may decrease the image quality. However, the predilection sites for ICH could be clearly identified. The SNR and CNR in the predilection sites for ICH were notably higher than other areas. The brain, eye lenses, and salivary glands received the highest radiation dose. Reducing tube current–time product from 250 to 100 mA can significantly reduce the radiation dose. Discussion: We demonstrated that low-dose CT scan of head can still provide reasonable images for diagnosing ICH. The radiation dose can be reduced to ∼45% of the conventional CT scan group.
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Brendlin, Andreas S., David Plajer, Maryanna Chaika, Robin Wrazidlo, Arne Estler, Ilias Tsiflikas, Christoph P. Artzner, Saif Afat, and Malte N. Bongers. "AI Denoising Significantly Improves Image Quality in Whole-Body Low-Dose Computed Tomography Staging." Diagnostics 12, no. 1 (January 17, 2022): 225. http://dx.doi.org/10.3390/diagnostics12010225.
Повний текст джерелаАнотація:
(1) Background: To evaluate the effects of an AI-based denoising post-processing software solution in low-dose whole-body computer tomography (WBCT) stagings; (2) Methods: From 1 January 2019 to 1 January 2021, we retrospectively included biometrically matching melanoma patients with clinically indicated WBCT staging from two scanners. The scans were reconstructed using weighted filtered back-projection (wFBP) and Advanced Modeled Iterative Reconstruction strength 2 (ADMIRE 2) at 100% and simulated 50%, 40%, and 30% radiation doses. Each dataset was post-processed using a novel denoising software solution. Five blinded radiologists independently scored subjective image quality twice with 6 weeks between readings. Inter-rater agreement and intra-rater reliability were determined with an intraclass correlation coefficient (ICC). An adequately corrected mixed-effects analysis was used to compare objective and subjective image quality. Multiple linear regression measured the contribution of “Radiation Dose”, “Scanner”, “Mode”, “Rater”, and “Timepoint” to image quality. Consistent regions of interest (ROI) measured noise for objective image quality; (3) Results: With good–excellent inter-rater agreement and intra-rater reliability (Timepoint 1: ICC ≥ 0.82, 95% CI 0.74–0.88; Timepoint 2: ICC ≥ 0.86, 95% CI 0.80–0.91; Timepoint 1 vs. 2: ICC ≥ 0.84, 95% CI 0.78–0.90; all p ≤ 0.001), subjective image quality deteriorated significantly below 100% for wFBP and ADMIRE 2 but remained good–excellent for the post-processed images, regardless of input (p ≤ 0.002). In regression analysis, significant increases in subjective image quality were only observed for higher radiation doses (≥0.78, 95%CI 0.63–0.93; p < 0.001), as well as for the post-processed images (≥2.88, 95%CI 2.72–3.03, p < 0.001). All post-processed images had significantly lower image noise than their standard counterparts (p < 0.001), with no differences between the post-processed images themselves. (4) Conclusions: The investigated AI post-processing software solution produces diagnostic images as low as 30% of the initial radiation dose (3.13 ± 0.75 mSv), regardless of scanner type or reconstruction method. Therefore, it might help limit patient radiation exposure, especially in the setting of repeated whole-body staging examinations.
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Oakley, Paul A., and Deed E. Harrison. "Death of the ALARA Radiation Protection Principle as Used in the Medical Sector." Dose-Response 18, no. 2 (April 1, 2020): 155932582092164. http://dx.doi.org/10.1177/1559325820921641.
Повний текст джерелаАнотація:
ALARA is the acronym for “As Low As Reasonably Achievable.” It is a radiation protection concept borne from the linear no-threshold (LNT) hypothesis. There are no valid data today supporting the use of LNT in the low-dose range, so dose as a surrogate for risk in radiological imaging is not appropriate, and therefore, the use of the ALARA concept is obsolete. Continued use of an outdated and erroneous principle unnecessarily constrains medical professionals attempting to deliver high-quality care to patients by leading to a reluctance by doctors to order images, a resistance from patients/parents to receive images, subquality images, repeated imaging, increased radiation exposures, the stifling of low-dose radiation research and treatment, and the propagation of radiophobia and continued endorsement of ALARA by regulatory bodies. All these factors result from the fear of radiogenic cancer, many years in the future, that will not occur. It has been established that the dose threshold for leukemia is higher than previously thought. A low-dose radiation exposure from medical imaging will likely upregulate the body’s adaptive protection systems leading to the prevention of future cancers. The ALARA principle, as used as a radiation protection principle throughout medicine, is scientifically defunct and should be abandoned.
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Silin, A. Yu, I. S. Gruzdev, G. V. Berkovich, A. E. Nikolaev, and S. P. Morozov. "Possibilities of applying model-based iterative reconstructions in computed tomography of the lungs." Medical Visualization 24, no. 3 (October 10, 2020): 107–13. http://dx.doi.org/10.24835/1607-0763-2020-3-107-113.
Повний текст джерелаАнотація:
Aim: A literature review of the possibilities of applying model iterative reconstruction (MIR) in computed tomography to improve image quality, including in low-dose scanning protocols.Materials and methods. The analysis of publications devoted to the application of MIR to reduce the radiation dose and improve the quality of images in CT diagnostics of lung pathology with an emphasis on the value of the achieved radiation dose was carried out.Results. The use of MIR eliminates digital noise from medical images, improving their quality. This feature can significantly reduce radiation exposure with low-dose protocols without loss of diagnostic quality. On average, application of MIR allows to reduce the radiation dose by 70% compared to a standard protocol, without increasing the noise level of CT images and maintaining the contrast-to-noise ratio. Previous studies have shown positive experience with the use of MIR in lung cancer screening programs and monitoring of cancer patients.Conclusion. The introduction of MIR in clinical practice can optimize the radiation exposure on the population without reducing the quality of CT images, however, the threshold dose to achieve a satisfactory image quality remains unexplored.
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Zhang, Xinan. "Passive millimeter wave imaging low altitude detection technology." Applied and Computational Engineering 62, no. 1 (May 20, 2024): 211–17. http://dx.doi.org/10.54254/2755-2721/62/20240429.
Повний текст джерелаАнотація:
Passive millimeter wave imaging refers to the passive detection of naturally occurring background millimeter waves. After receiving external millimeter wave thermal radiation signals, the passive millimeter wave detection system will form images based on temperature differences and detect targets. Passive millimeter wave imaging has the advantages of non-radiation, non-contact, perspective imaging, good concealment, small size, and low power consumption. It is widely used in safety inspections, aircraft landing, low visibility navigation, sea surface detection and other fields. Driven by high and new technology, passive millimeter wave imaging low-altitude detection technology is rapidly developing. This paper introduced the basic principle of passive millimeter wave imaging, including the characteristics of millimeter wave radiation and Black-body radiation law, as well as its comparison with ordinary optical radiation. It also described the basic model of current passive millimeter wave imaging low altitude detection technology, explored the shortcomings of this technology and pointed out further work as well.
Дисертації з теми "Low radiation images"
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Saleem, Afsah. "Machine learning for computer-aided diagnostics from complex medical images." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2025. https://ro.ecu.edu.au/theses/2927.
Повний текст джерелаАнотація:
Machine learning has significantly transformed medical image analysis in the current age of artificial intelligence offering vast potential in improving disease diagnosis and management. Cardiovascular diseases (CVDs) are among the leading cause of global mortality, emphasizing the need for early detection for effective intervention and prevention. Abdominal Aortic Calcification (AAC) is an early indicator and contributor to Atherosclerotic Cardiovascular Diseases (ASCVDs) and is commonly assessed through imaging modalities such as computed tomography (CT), X-rays, and Dual-energy X-ray Absorptiometry (DXA). Among these, lateral spine DXA scans, commonly used for osteoporosis screening, offer a cost-effective and low-radiation opportunity for opportunistic CVD risk assessment. Despite advancements in medical imaging technologies, AAC evaluation still relies on manual interpretation by trained clinicians, a process that is labor-intensive, subjective, and prone to variability. Automating the process of AAC quantification can address these challenges and enable consistent, early screening for CVD risk.
This research presents robust machine-learning frameworks for the automated and accurate prediction of the AAC-24 score and its classification into relevant risk classes (low, moderate, and high). First, we explore deep feature ensembling methods to develop a deep feature fusion network for AAC-4 scoring using regression loss. However, its performance was limited by class ambiguities from inter-class similarities, intra-class variations, and low resolution VFA DXA artifacts. To mitigate this problem, we formulate AAC-24 scoring as an ordinal regression problem and propose a novel supervised contrastive ordinal learning (SCOL) framework. SCOL leverages a label-dependent distance metric to capture the ordinal nature of AAC labels. Using SCOL, we develop a Dual-encoder Contrastive Ordinal Learning (DCOL) framework to learn contrastive ordinal representation at global and local levels, improving feature separability and class diversity in the latent space among the AAC-24 categories. Clinical validation demonstrated a strong association between ML-AAC-24 scores and ASCVD risk, with substantial agreement between ML predictions and expert assessments. To enhance generalizability across different imaging modalities, SCOL framework is further explored for lateral spine X-rays via cross-domain fine-tuning, enhancing its utility in diverse clinical settings.
To strengthen this work on highly imbalanced disease grading medical datasets, a prototype-based learning approach is incorporated within the SCOL framework to develop a generic disease grading system. The framework is evaluated on public datasets for diabetic retinopathy grading and breast cancer staging, demonstrating its ability to learn robust, ordinal-aware prototypes that generalize across diverse medical imaging tasks. Additionally, to enhance the interpretability and reliability of automated systems in clinical diagnosis, we develop a context-aware ordinal learning framework for granular-level AAC-24 scoring. We address the challenges of SCOl in handling class imbalance for ordinal regression tasks and introduce SCOL+. We explore SCOL+ in a multi-label setting to determine the extent of calcification in each section of the aorta to aid clinicians in making detailed and interpretable diagnoses.
In this thesis, the AAC algorithms are developed using five large clinical datasets obtained from machines with different manufactures, including patients from Australia, Canada, and the United States, spanning both male and female patients. In conclusion, as DXA scans are commonly captured in various clinical scenarios, this research offers a novel and opportunistic approach to cardiovascular disease detection and monitoring in clinical practice, potentially revolutionizing the way we approach CVD risk screening.
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Nerborg, Amanda, and Elias Josse. "IR Image Macine Learning for Smart Homes." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-42344.
Повний текст джерелаАнотація:
Sweden is expecting an aging population and a shortage of healthcare professionals in the near future. This amounts to problems like providing a safe and dignified life for the elderly both economically and practically. Technical solutions that contribute to safety, comfort and quick help when needed is essential for this future. Nowadays, a lot of solutions include a camera, which is effective but invasive on personal integrity. Griddy, a hardware solution containing a Panasonic Grid-EYE, an infrared thermopile array sensor, offers more integrity for the user. Griddy was developed by students in a previous project and was used for this projects data collecting. With Griddy mounted over a bed and additional software to determine if the user is on the bed or not a system could offer monitoring with little human interaction. The purpose was to determine if this system could predict human presence with high accuracy and what limitations it might have. Two data sets, a main and a variational, were captured with Griddy. The main data set consisted of 240 images with the label “person” and 240 images with the label “no person”. The machine learning algorithms used were Support Vector Machine (SVM), k-Nearest Neighbors (kNN) and Neural Network (NN). With 10-Fold Cross Validation, the highest accuracy found was for both SVM and kNN (0.99). This was verified with both algorithms accuracy (1.0) on the test set. The results for the variational data set showed lower reliability in the system when faced with variations not presented in the training, such as elevated room temperature or a duvet covering the person. More work needs to be done to expand the main data set to meet the challenge of variations.I Sveriges väntas i den närmaste framtiden en åldrande population och en brist på vårdpersonal. Detta innebär både ekonomiska och praktiska problem för att ge äldre ett säkert och värdigt liv. Tekniska lösningar som kan bidra med säkerhet, komfort och snabb hjälp vid behov är av essentiell vikt i framtiden. Idag innehåller många lösningar en kamera. Detta är en effektiv men integritetskränkande lösning. Griddy, som är en hårdvarulösning innehållande en Panasonic Grid-EYE, en infraröd termosensor, erbjuder mer integritet för brukaren. Griddy utvecklades av studenter i ett tidigare projekt och användes för datainsamling i detta projektet. Genom att montera Griddy över sängen och använda en tillhörande mjukvara, som avgör om brukaren är i sängen eller inte, skulle ett system kunna erbjuda övervakning med lite mänsklig inblandning. Syftet var att ta reda på om detta system skulle kunna avgöra brukarens närvaro med hög tillförlitlighet och vilka begränsningar systemet skulle ha. Två datasamlingar samlades in med hjälp av Griddy. En huvudsaklig datasamling och en med variation. Den huvudsakliga datasamlingen bestod av 240 bilder med etiketten "person" och 240 bilder med etiketten "ingen person". Algoritmerna för maskininlärning som användes var Support Vector Machine (SVM), k-Nearest Neighbors (kNN) och Neural Network (NN). Med 10-Fold Cross Validation fanns den högsta tillförlitligheten med algoritmerna SVM och kNN (0.99). Detta verifierades med tillförlitligheten för testsamlingen hos SVM och kNN (1.0). För datasamlingen med variation visade resultaten på en lägre tillförlitlighet när systemet mötte variationer som det inte tränats med, såsom förhöjd rumstemperatur eller ett täcke över personen. Slutsatsen är att en huvudsaklig datasamling bör utökas med mer variation så att systemet tränas till att klara större utmaningar.
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Aubry, Alexandre. "Approche matricielle de l'opérateur de propagation des ondes ultrasonores en milieu diffusant aléatoire." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://pastel.archives-ouvertes.fr/pastel-00004213.
Повний текст джерелаАнотація:
Cette thèse étudie les propriétés de l'opérateur de propagation des ondes ultrasonores en milieu aléatoire. Le dispositif expérimental consiste en un réseau multi-éléments placé en vis-à-vis d'un milieu désordonné. L'opérateur de propagation est donné par la matrice des réponses inter-éléments mesurées entre chaque couple de transducteurs. En s'appuyant sur la théorie des matrices aléatoires, le comportement statistique de cet opérateur a été étudié en régime de diffusion simple et multiple. Une cohérence déterministe des signaux est ainsi mise en évidence en régime de diffusion simple, cohérence qui disparaît dès que la diffusion multiple prédomine. Cette différence de comportement a permis la mise au point d'un radar intelligent séparant les échos simplement et multiplement diffusés. On peut ainsi extraire l'écho direct d'une cible échogène enfouie dans un milieu hautement diffusant, bien que ce dernier soit source de diffusion multiple et d'aberration. Une deuxième approche consiste, au contraire, à extraire une contribution de diffusion multiple noyée dans une contribution de diffusion simple largement prédominante. L'étude de l'intensité multiplement diffusée permet de mesurer des paramètres de transport (p.ex. la constante de diffusion D) caractérisant la propagation de l'onde multiplement diffusée. Un passage en champ lointain (ondes planes) permet d'obtenir une mesure fiable de D en étudiant le cône de rétrodiffusion cohérente. Un passage en champ proche, via l'utilisation de faisceaux gaussiens, permet d'effectuer des mesures locales de D en étudiant la croissance du halo diffusif. Cette approche a été appliquée au cas de l'os trabéculaire humain autour de 3 MHz.
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Lin, Meng-yu, and 林孟郁. "Evaluation of Reconstruction Algorithm on Image Quality of Low-Radiaton-Dose Lung CT." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41085533391777812755.
Повний текст джерелаАнотація:
碩士中臺科技大學
放射科學研究所
99
Low-radiation-dose lung CT is a promising method for lung cancer screening. The image quality is affected by parameters of reconstruction algorithm, so it is important to choose proper reconstruction algorithm under low-radiation-dose. The purpose of this study is to evaluate the effect of five different reconstruction algorithms on image quality of low- radiation-dose lung CT. In this study, each lung cancer screening image (low-radiation-dose lung CT) was divided into five groups (A, B, C, F and L) with usage of five different reconstruction algorithms. These images were subjectively reviewed by two chest radiologists with the five-point scale, and were objectively compared by usage of the Moran I test and contrast-to-noise ratio(CNR). In the subjective comparison, the mean and standard deviation were 4.07± 0.61 in group A, 4.15± 0.58 in group B, 4.37± 0.59 in group C, 4.33± 0.59 in group F, and 4.00± 0.73 in group L. The interobserver agreement have significant different（p＜ 0.001）. In the objective comparison, the result of sharp algorism, C and F group, in Moran I test and CNR was similar. Although loss of some image information in the sharp algorithm, C and F group, it may be a compromise in image noise and spatial resolution because the result of group C and F in the subjective comparison was better than others. The sharper algorism of group L is even more different than others in Moran I test, and is also worse than others in subjective comparison due to more noise. This study showed the importance of objective and subjective methods in comparison of the image quality.
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Matthews, Jeffrey Blair. "Characterisation of the apoptotic response due to low doses of radiation using automated image cytometry." Thesis, 1997. http://hdl.handle.net/2429/7376.
Повний текст джерелаАнотація:
Traditionally, cell survival following x-irradiation has been assumed to follow a
monotonic dose response, even at very low doses. Recent improvements to the low
dose assay have revealed that many cell lines exhibit a complex response whereby cells
are hyper-radiosensitive to X-rays at these doses (HRS) followed by an increased
radioresistance (IRR) as dose approaches 1 Gy. This hypersensitivity may be eliminated
by pre-treatment with small priming doses of x-rays, and there is evidence that the
increased radioresistance may be a reflection of an inducible repair mechanism.
Because molecular evidence strongly suggests a coupling of DNA repair and apoptosis,
or programmed cell death, a hypothesis was put forth that HRS/IRR would be reflected
in changes in the levels of apoptotic cell death over this dose region. To test this
hypothesis, a very large cell population would be required.
To overcome the technical and statistical problems associated with such
measurements, an automated image cytometric method of apoptotic cell classification
was developed. Image acquisition software was adapted to gather double-stained cell
images from slides prepared using cell fixation and staining methods which emphasised
apoptotic morphology. Chinese hamster ovary cells were classified individually by
discriminant analysis of morphological and nuclear texture features calculated for each
image. Discriminant functions were constructed from a manually classified set of over
60,000 cell images categorised as "normal", "apoptotic", "cell doublets" or "debris" and all
subsequent cell images collected were classified using these functions. Application of
this technique resulted in a 99.8% accuracy in classification of the normal cell
population, and 81.7% classification accuracy for apoptotic cells. This method was then applied to study the time course of the apoptotic response of CHO cells following xirradiation.
Following irradiation with 5 Gy, no increase above control levels of apoptosis was
noted until 18 hours post-irradiation, which corresponded to the release of the G2-block
as determined by DNA-content analysis. Apoptotic frequency increased to a peak level
of 12.1%±4.6 at 42 hours post-irradiation. CHO cells irradiated with 0.25 or 1.0 Gy also
exhibited peak levels at 42 hours, although no cell cycle perturbations were noted
following irradiation. A secondary peak in apoptosis was noted 60 hours post-irradiation
for these doses. Cells exposed to 0.5 Gy however, showed no distinct peak in apoptosis
frequency. Analysis of the cumulative amounts of apoptosis observed at 6 hour time
intervals over a 72 hour period following irradiation showed greater levels of apoptosis in
the 0.25 Gy irradiated population than in the cells exposed to 0.5 Gy. These results were
not statistically significant when subjected to Student's t-test analysis. Experiments using
small priming doses of x-rays 6 hours prior to challenge doses failed to show a reduction
in apoptotic frequency as would be expected if apoptosis were directly responsible for
the HRS/IRR phenomenon.
While a direct involvement of apoptosis in HRS/IRR cannot be ruled out, these
results do not generally support the original hypothesis. The post-mitotic nature of
apoptosis in CHO cells, several generations following low dose irradiation, obscures the
relationship of these results to cell survival data. However, there may be some
implications for cell survival measurements due to effects on resulting colony size. These
studies suggest that the characterisation of the low dose apoptotic response requires
further investigation. The automated techniques developed here will aid significantly in
this pursuit.
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CHEN, KENG-QIANG, and 陳鏗鏘. "Evaluation of image Quality and Radiation Dose by Low-Dose Computed Tomography for Diagnosis of Pulmonary Nodules." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/58698504997276173291.
Повний текст джерелаАнотація:
碩士元培醫事科技大學
醫學影像暨放射技術系碩士班
104
Lung cancer is ten leading causes of death in Taiwanbased on the statistical data from the Ministry of Health and Welfare in 2014., The earlier it is diagnosed the better the chance of getting early and effective treatment.Currently, low-dose multi-slice computed tomography (MSCT) is considered to be the most widely applicable modality for evaluation of lung cancer. The aim of this study was to compare the effective dose for imaging of lung within three different Medical Imagiing Systems. This retrospective study was conducted fromJanuary 2015 to March 2015at Mackay Memorial Hospital. One hundred patients were randomly selected to perform lung CT scan without injecting contrast agent by three different computed tomographyscanner (A, B, C). f The CT settings were selected the procedure of low-dose lung cancer screening. The CT parameters were set as 120 kVp fixed tube voltage, 20 mAs tube current,and 1 mm slice thickness under automatic exposure control (AEC) (slice thickness) is. Each lung CT imaging was then examined for evidence of simplex lesions mist frosted glass nodules by two experienced radiologists. The results showed that the volume CT dose index (CTDIvol) was significant lower at Group A (1.31 ± 0.22 mGy) than Group B (1.71 ± 0.29 mGy) and Group C (1.94 ± 0.43 mGy) (p <0.0001), The mean effective dose (E) were significant lower at Group A (0.63 ± 0.12 mSv) than Group B (0.92 ± 0.18 mSv) than Group C (0.95 mSv ± 0.23 mSv). The image interpretation of the smallest nodule diameter was 1.6 mm (Group A), 1.6 mm (Group B) and 1.4 mm (Group C). Patients with the body mass index (BMI) < 24 kg/m2, we observed the average effective dose was 0.58 mSv (n = 26, Group A), 0.81mSv (n =24, Group B), 0.85mSv (n =28, Group C). However, patients with BMI ≥ 24 kg/m2 we found the average effective dose was 0.68 mSv (n = 24, Group A), 1.02 mSv (n = 26, Group B), 1.09 mSv (n = 22, Group C). The results of this study showed that the tube current, tube voltage, rotation time, collimation, pitch, the parameter of reconstruction, scout image, scan length BMIwould affect the radiation dose and image quality. We suggested that reducing tube current, tube voltage scan length and, increasing pitch and detectors, fasting scan time and setting automatic exposure control would reduce radiation dose and maintain good image quality while screening lung caner by using MSCTnt Keywords: Low-dose CT, lung nodules, image quality, effective dose
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Chen, Chiao-Yun, and 陳巧雲. "Low Radiation Dose Protocols for Colorectal Cancer, Renal and Urinary System Diseases using Dual-Energy CT: Image Quality, Diagnostic Accuracy, and Dose Reduction." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/14021368310479185890.
Повний текст джерелаАнотація:
博士高雄醫學大學
醫學研究所博士班
105
Computed tomography (CT) has recently become the single largest source of medical radiation delivered to the general population. The large number of patients receiving CT examinations has raised concerns regarding radiation exposure of patients, the risk of radiation-induced cancers, and increased cancer deaths later in life. In response to this concern, calls have been made for developing new CT protocols to reduce radiation dose while maintaining an optimal image. Of course, reducing the number of scans, more immediately to reduce the radiation dose received by the patient With recent advances in CT technology, dual-energy computed tomography (DECT) simultaneously acquires datasets at two different photon spectra (typically 140kVp and 80kVp) in a single acquisition, and iodine (the main component of contrast medium) can be distinguished from other materials owing to its stronger photoelectric absorption at low tube voltages near K-edge of iodine. Using dual-energy scanning, X-rays of two different levels of attenuation coefficient generated data set, the computer operator to scan tissue classification characteristic analysis performed on the material composition can be provided in different tissues distinction, have the ability to distinguish between the basic composition of a substance, now known to have the calcium content of the bones can be distinguished component, intravascular contain iodine ingredients, uric acid ingredients of the urinary stones and enhancement of the soft tissue. Iterative image reconstruction method (Sinogram affirmed iterative reconstruction, SAFIRE) is a recent reconstruction algorithm, uses a noise modeling technique supported by raw data (sinogram data), to reduce noise and maintain image sharpness. The rapid reduction of noise and artifact images can improve image quality which can achieve the purpose of reducing the radiation dose. The project focuses of the study are using the dose reduction techniques of dual-energy CT, combined with image reconstruction (Sinogram affirmed iterative reconstruction, SAFIRE), for the diagnosis of colorectal cancer and kidney and urinary tract disease, image quality assessment and evaluation of radiation dose reduction.
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Parsons, David, and David Parsons. "The production and detection of optimized low-Z linear accelerator target beams for image guidance in radiotherapy." 2012. http://hdl.handle.net/10222/15393.
Повний текст джерелаАнотація:
Recent work has demonstrated improvement of image quality with low atomic number (Z) linear accelerator (linac) targets and energies as low as 3.5 MV compared to a standard 6 MV therapeutic beam. In this work, the incident electron beam energy has been lowered to energies between 1.90 and 2.35 MeV. The improvement of megavoltage planar image quality with the use of carbon and aluminum linac targets has been assessed compared to a standard 6 MV therapeutic beam.
Common electronic portal imaging devices contain a 1.0 mm copper conversion plate to increase detection efficiency of a therapeutic megavoltage spectrum. When used in imaging with a photon beam generated with a low-Z target, the conversion plate attenuates a substantial proportion of photons in the diagnostic range, thereby reducing the achievable image quality. Image quality as a function of copper plate thickness has been assessed for planar imaging and cone beam computed tomography.
Книги з теми "Low radiation images"
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Buechel, Ronny R., and Aju P. Pazhenkottil. Basic principles and technological state of the art: hybrid imaging. Edited by Philipp Kaufmann. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0121.
Повний текст джерелаАнотація:
The core principle of hybrid imaging is based on the fact that it provides information beyond that achievable with either data set alone. This is attained through the combination and fusion of two datasets by which both modalities synergistically contribute to image information. Hybrid imaging is, thus, more powerful than the sum of its parts, yielding improved sensitivity and specificity. While datasets for integration may be obtained by a variety of imaging modalities, its merits are intuitively best exploited when combining anatomical and functional imaging, particularly in the setting of evaluation of coronary artery disease (CAD) as this combination allows a comprehensive assessment with regard to presence or absence of coronary atherosclerosis, the extent and severity of coronary plaques, and the haemodynamic relevance of stenosis. In clinical practice, the combination of CT coronary angiography (CCTA) with myocardial perfusion studies obtained by single-photon emission computed tomography (SPECT) and by positron emission tomography (PET) has been well established. Recent literature also reports on the feasibility of combining CCTA with cardiac magnetic resonance imaging. Finally, recent advances in CCTA and SPECT imaging have led to a substantial reduction of radiation exposure, now allowing for comprehensive morphological and functional diagnostic work-up by cardiac hybrid SPECT/CCTA imaging at low radiation dose exposures ranging below 5 mSv.
Частини книг з теми "Low radiation images"
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Wodzinski, Marek. "Benchmark of Deep Encoder-Decoder Architectures for Head and Neck Tumor Segmentation in Magnetic Resonance Images: Contribution to the HNTSMRG Challenge." In Lecture Notes in Computer Science, 204–13. Cham: Springer Nature Switzerland, 2025. https://doi.org/10.1007/978-3-031-83274-1_15.
Повний текст джерелаАнотація:
Abstract Radiation therapy is one of the most frequently applied cancer treatments worldwide, especially in the context of head and neck cancer. Today, MRI-guided radiation therapy planning is becoming increasingly popular due to good soft tissue contrast, lack of radiation dose delivered to the patient, and the capability of performing functional imaging. However, MRI-guided radiation therapy requires segmenting of the cancer both before and during radiation therapy. So far, the segmentation was often performed manually by experienced radiologists, however, recent advances in deep learning-based segmentation suggest that it may be possible to perform the segmentation automatically. Nevertheless, the task is arguably more difficult when using MRI compared to e.g. PET-CT because even manual segmentation of head and neck cancer in MRI volumes is challenging and time-consuming. The importance of the problem motivated the researchers to organize the HNTSMRG challenge with the aim of developing the most accurate segmentation methods, both before and during MRI-guided radiation therapy. In this work, we benchmark several different state-of-the-art segmentation architectures to verify whether the recent advances in deep encoder-decoder architectures are impactful for low data regimes and low-contrast tasks like segmenting head and neck cancer in magnetic resonance images. We show that for such cases the traditional residual UNet-based method outperforms (DSC = 0.775/0.701) recent advances such as UNETR (DSC = 0.617/0.657), SwinUNETR (DSC = 0.757/0.700), or SegMamba (DSC = 0.708/0.683). The proposed method (lWM team) achieved a mean aggregated Dice score on the closed test set at the level of 0.771 and 0.707 for the pre- and mid-therapy segmentation tasks, scoring 14th and 6th place, respectively. The results suggest that proper data preparation, objective function, and preprocessing are more influential for the segmentation of head and neck cancer than deep network architecture.
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Haouchine, Nazim, Parikshit Juvekar, Xin Xiong, Jie Luo, Tina Kapur, Rose Du, Alexandra Golby, and Sarah Frisken. "Estimation of High Framerate Digital Subtraction Angiography Sequences at Low Radiation Dose." In Medical Image Computing and Computer Assisted Intervention – MICCAI 2021, 171–80. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-87231-1_17.
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Millet, Philippe, Guilaume Bernard, and Paul Brelet. "Reducing the Radiation Dose by a Factor of 4 Thanks to Real-Time Processing on the Tulipp Platform." In Towards Ubiquitous Low-power Image Processing Platforms, 175–92. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53532-2_10.
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Herva, Vesa-Pekka, Aki Hakonen, Roger Norum, Oula Seitsonen, and Markus Fjellström. "Introduction." In Arctic Encounters, 1–13. Cham: Springer Nature Switzerland, 2025. https://doi.org/10.1007/978-3-031-85016-5_1.
Повний текст джерелаАнотація:
Abstract The dulled patina on the olive-black shell of the noise-cancelling headsets suggested they had been part of the long-serving helicopter’s gear for some time. Inside the cockpit, a mobile phone panned the horizon. Radiating off the screen, the image resembled the opening scene of a 1970s blockbuster. Outside, an otherworldly boulder-ridden landscape of valleys and streams whisked by, the shadow of the chopper skimming along the surface. The roar of the turbine engine must have echoed in every nook and crevice, but the headsets guarded us from the noise, mellowing it down to a low electric purr.
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Gayou, O. "Image-guided stereotactic body radiation therapy using a low-Z target imaging beam line and a high dose rate unflattened beam." In IFMBE Proceedings, 130–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03474-9_38.
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Saxena, Priyank, and R. Sukesh Kumar. "Restoration of CT Images Corrupted With Fixed Valued Impulse Noise Using an Optimum Decision-Based Filter." In Advances in Multimedia and Interactive Technologies, 220–39. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-5246-8.ch008.
Повний текст джерелаАнотація:
The main aim of this chapter is to perform the restoration of computed tomography (CT) images acquired at the reduced level of radiation dose. Reduction in radiation dose affects the image quality as it increases noise and decreases low contrast resolution. In this chapter, an optimum decision-based filter (ODBF) is proposed as an image-space denoising technique, to detect and restore the low dose CT (LDCT) images corrupted with fixed valued impulse noise (salt and pepper) of unequal density. The detection stage employs k-means clustering to discriminate the noise-free pixels from the noisy-pixels by splitting the image data into three clusters of different intensities. The restoration stage employs mask else trimmed median (METM) estimation followed by an optional adaptive mask sizing for restoration of noisy pixels. The proposed method demonstrates noticeable improvement over other existing methods in restoration of LDCT images while maintaining the image contrast and edge details.
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Ziyad, Shabana R., Radha V., and Thavavel Vaiyapuri. "Noise Removal in Lung LDCT Images by Novel Discrete Wavelet-Based Denoising With Adaptive Thresholding Technique." In Research Anthology on Improving Medical Imaging Techniques for Analysis and Intervention, 706–21. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-6684-7544-7.ch035.
Повний текст джерелаАнотація:
Cancer is presently one of the prominent causes of death in the world. Early cancer detection, which can improve the prognosis and survival of cancer patients, is challenging for radiologists. Low-dose computed tomography, a commonly used imaging test for screening lung cancer, has a risk of exposure of patients to ionizing radiations. Increased radiation exposure can cause lung cancer development. However, reduced radiation dose results in noisy LDCT images. Efficient preprocessing techniques with computer-aided diagnosis tools can remove noise from LDCT images. Such tools can increase the survival of lung cancer patients by an accurate delineation of the lung nodules. This study aims to develop a framework for preprocessing LDCT images. The authors propose a noise removal technique of discrete wavelet transforms with adaptive thresholding by computing the threshold with a genetic algorithm. The performance of the proposed technique is evaluated by comparing with mean, median, and Gaussian noise filters.
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Alla Takam, Clémence, Aurelle Tchagna Kouanou, Odette Samba, Thomas Mih Attia, and Daniel Tchiotsop. "Big Data Framework Using Spark Architecture for Dose Optimization Based on Deep Learning in Medical Imaging." In Artificial Intelligence. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97746.
Повний текст джерелаАнотація:
Deep learning and machine learning provide more consistent tools and powerful functions for recognition, classification, reconstruction, noise reduction, quantification and segmentation in biomedical image analysis. Some breakthroughs. Recently, some applications of deep learning and machine learning for low-dose optimization in computed tomography have been developed. Due to reconstruction and processing technology, it has become crucial to develop architectures and/or methods based on deep learning algorithms to minimize radiation during computed tomography scan inspections. This chapter is an extension work done by Alla et al. in 2020 and explain that work very well. This chapter introduces the deep learning for computed tomography scan low-dose optimization, shows examples described in the literature, briefly discusses new methods for computed tomography scan image processing, and provides conclusions. We propose a pipeline for low-dose computed tomography scan image reconstruction based on the literature. Our proposed pipeline relies on deep learning and big data technology using Spark Framework. We will discuss with the pipeline proposed in the literature to finally derive the efficiency and importance of our pipeline. A big data architecture using computed tomography images for low-dose optimization is proposed. The proposed architecture relies on deep learning and allows us to develop effective and appropriate methods to process dose optimization with computed tomography scan images. The real realization of the image denoising pipeline shows us that we can reduce the radiation dose and use the pipeline we recommend to improve the quality of the captured image.
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Fessler Pierre, Prevot Guy, and Hilt B. "Ultra Low Dose X-ray Spinal Examinations." In Studies in Health Technology and Informatics. IOS Press, 2002. https://doi.org/10.3233/978-1-60750-932-5-191.
Повний текст джерелаАнотація:
The study and treatment of spinal deformities may lead to excessive doses of radiation for patients (especially children) examined by conventional X-ray radiology apparatus. In order to avoid this very crucial problem, a new X-ray radiology system has been devised. The new apparatus uses a high efficiency linear solid-state detector and highly sensitive electronics, operating in single X-ray counting mode (quantum mode). The scan parameters and image filtering are computer controlled. Data is acquired in real time by a high speed VME system. In this paper, the first images recorded using this new apparatus are shown. The main conclusion of the preliminary comparative dosimetric analysis is that it is possible to divide the patient’s dose by a factor of at least ten to one hundred with the quantum X-ray radiology apparatus.
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Nalladega Vijayaraghava, Sathish Shamachary, Murray Terry, Shin Eunsung, Jata Kumar, Blodgett Mark, and Knopp Jeremy S. "Experimental Investigation of Low Frequency Electromagnetic Wave Interaction with Metallic Nanoparticles." In Studies in Applied Electromagnetics and Mechanics. IOS Press, 2010. https://doi.org/10.3233/978-1-60750-554-9-87.
Повний текст джерелаАнотація:
The interaction of electromagnetic radiation with small metallic particles has been studied in greater detail during the last decade. It is well known that the noble metallic nanoparticles, like gold and silver exhibit remarkable optical properties, viz, strong colors exhibited by these nanoparticles. These particles acquire a characteristic color due to plasmon resonance. Plasmon resonance occurs due to coherent oscillation of the conduction band electrons induced by the incident electromagnetic field at optical frequencies. Optical techniques are conventionally used to detect the surface plasmon resonance modes in metallic nanoparticles with nanometer resolution. In these techniques, the electric field around the nanoparticle is usually sensed and imaged. Moreover, these techniques are used at optical frequencies. The imaging of magnetic field around the nanoparticles at high frequencies is very complicated. The imaging of magnetic field around nanoparticles at low frequency electromagnetic radiation has not been reported so far in the literature, to the knowledge of the authors. In this paper, we report a new methodology to image magnetic moments of metallic nanoparticles in low frequency electromagnetic fields. To accomplish this, a traditional atomic force microscope (AFM) is externally modified to detect near-field magnetic fields of the nanoparticles. Samples of silver and platinum nanoparticles are kept in the electromagnetic field excited at frequencies in the range of 30-100 kHz. The magnetic field around the nanoparticles is then detected by a magnetic AFM tip-cantilever positioned at a distance of few nanometers. The output of the cantilever is used to separate topography and magnetic field image using external electronic instrumentation. Magnetic field images are obtained at different frequencies and the effect of size, shape and frequency on the magnetic field distribution is studied. The results of the magnetic field distribution are analyzed in view of the possibility of using the methodology for sensing application.
Тези доповідей конференцій з теми "Low radiation images"
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Wang, Tong, Yunsong Feng, Wei Jin, Siyu Wang, and Changqi Zhou. "Research on dual-band infrared image fusion based on Planck's radiation law." In Infrared Technology and Applications, edited by Xue Li and Xin Tang, 27. SPIE, 2024. https://doi.org/10.1117/12.3048447.
Повний текст джерела
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Ferwerda, H. A., and C. H. Slump. "Statistical Aspects of Low-Dose Electron Microscopy." In Quantum-Limited Imaging and Image Processing. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/qlip.1986.wa3.
Повний текст джерелаАнотація:
The bombardment by electrons of (biological) objects in the electron microscope leads to radiation damage. Accordingly we have to minimize the number of electrons impinging on the object in order to get a reliable image. The image gets a very noisy appearance (shot noise) and the results derived from these images become stochastic quantities of which we would like to obtain the probability distributions. For this program to be carried out we have to know the relation between the image and the object. A schematic of the imaging process is depicted in Fig. 1. The image plane is supposed to be covered by N2 ideal electron counters, where N2 is the number of degrees of freedom (Shannon number) of the image.
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Rarback, Harvey, Christopher Jacobsen, John Kenney, Janos Kirz, and Roy Rosser. "X-ray microscopy with synchrotron radiation." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.wl1.
Повний текст джерелаАнотація:
Soft x rays are an excellent probe for high spatial resolution detection of low atomic number specimens. We have developed a scanning microscope at the National Synchrotron Light Source (NSLS) which uses a small (~0.2-μm) spot of x rays in the 24-44-Å wavelength range. The microscope can form transmission images in real time at a fixed wavelength, or, by making an image of the difference in transmission on either side of an element's absorption edge, it can make a high resolution map of that element’s concentration. We have used the microscope primarily for imaging and microanalysis of biological specimens. However, with minor modifications the instrument can be used for high resolution material science studies of surfaces or bulk specimens without the requirements of excessive specimen thinning or vacuum compatibility presently required by electron probe instruments. The x-ray probe is presently formed by a Fresnel zone plate fabricated at IBM using electron-beam lithography. We will improve the resolution considerably with higher resolution zone plates fabricated by a variety of techniques. We will also increase the throughput of the instrument several orders of magnitude by moving from a bending magnet source of synchrotron radiation to the soft x-ray undulator soon to be installed on the x-ray storage ring at the NSLS. With these improvements we plan to make high resolution (< 1000-Å) scanned images in <1 min.
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Palmer, J. R., and G. R. Morrison. "Differential Phase Contrast Imaging in the Scanning Transmission X-ray Microscope." In Short Wavelength Coherent Radiation: Generation and Applications. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/swcr.1991.wa15.
Повний текст джерелаАнотація:
In the scanning transmission x-ray microscope (STXM) the specimen is scanned in a raster by an x-ray probe formed with a Fresnel zone plate. To achieve near diffraction limited resolution it is necessary to have a coherent source, even when forming an incoherent brightfield image by measuring the x-ray intensity transmitted by the object. This has so far been the only imaging mode used in the STXM and for hydrated biological specimens is well suited to soft x-ray wavelengths within the “water window” (2·33 to 4·36 nm) where carbon absorbs much more strongly than water. However, by the use of phase contrast rather than amplitude contrast, it is possible to form images at wavelengths where the absorption is low, resulting in lower radiation dose for the same level of contrast. Calculations made by Howells [1] and Rudolph and Schmahl [2] have demonstrated very clearly the advantages of phase contrast imaging at wavelengths outside the water window.
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Photiou, Christos, Iosif Strouthos, Constantina Cloconi, and Costas Pitris. "Early identification of low-grade acute radiation dermatitis using in vivo optical coherence tomography (OCT) images of human head and neck." In Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXVII, edited by Joseph A. Izatt and James G. Fujimoto. SPIE, 2023. http://dx.doi.org/10.1117/12.2650318.
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Oseen-Senda, K. M., F. Lundell, A. Hillenbach, and J. Pauchet. "Visualization of Low Heat and Mass Flux Boiling in a Small Metal Pipe Using Neutron Radiography." In ASME 2004 2nd International Conference on Microchannels and Minichannels. ASMEDC, 2004. http://dx.doi.org/10.1115/icmm2004-2374.
Повний текст джерелаАнотація:
High speed visualization of boiling pentane in a circular steel tube (Di = 1.2 mm, Do = 2 mm) has been performed at the Neutrograph instrument at the Institut Laue-Langevin in Grenoble, France. The heat and mass flux were both very low and appropriate for cooling of PEM fuel cells. The spatial resolution of the images is approximately 0.15 mm and the maximum frequency is 154 Hz. In the images, the liquid-vapor differentiation is clearly visible. Time resolved measurements of the outer pipe wall temperature, synchronized with the images, show that at low mass flow rates, the pipe wall is high above the saturation temperature and the pipe filled with vapor and liquid slugs. At higher flow rates, the wall is superheated when filled with liquid and at saturation temperature during boiling when exposed to a liquid-vapor mixture. An irregular switching between these two states was observed. The superheated wall is shown to be consistent with superheated liquid in the pipe prior to boiling. Unfortunately the strong γ-radiation produced by the neutrons has a substantial effect on the onset of boiling, which is why comparisons with non-irradiated systems might be difficult.
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Ignatiev, M., V. Senchenko, V. Dozhdikov, I. Smurov, and P. Bertrand. "Digital Diagnostics Based on CCD Imaging for Monitoring Thermal Spray Processes." In ITSC2002, edited by C. C. Berndt and E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2002. http://dx.doi.org/10.31399/asm.cp.itsc2002p1001.
Повний текст джерелаАнотація:
Abstract This paper describes the development of a diagnostic system that monitors in-flight particle diameters, velocities, and temperatures during thermal spraying. The system is based on a low-cost CCD camera and user-developed software. The camera incorporates a 732 x 282 pixel sensor with high sensitivity in the near IR range where the only radiation is that of the particles. User-developed software modules handle signal processing, image analysis, calibration, and data visualization. In video images, particles appear as light tracks of varying length, width, and intensity, corresponding (respectively) to velocity, diameter, and temperature. A test case in which Cr2O3 powder is sprayed in a plasma jet demonstrates the capabilities of the diagnostic system. Paper includes a German-language abstract.
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Ghanbarzadeh Dagheyan, Ashkan, Ali Molaei, Richard Obermeier, Chang Liu, Aida Kuri Martinez, and Jose Martinez Lorenzo. "Initial Results of a Bimodal, Ultrasound-Microwave, Imaging System for Early Detection of Breast Cancer." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-72174.
Повний текст джерелаАнотація:
Unlike x-ray, ultrasound imaging (USI) uses nonionizing acoustic radiation to detect tumors in various body organs, including breast. In the reconstructed images, a radiologist can distinguish between a tumor and a non-malignant cyst, which is highly valuable in making true-positive diagnoses. However, clinical data shows that the addition of ultrasound to mammography, as a separate but auxiliary imaging tool, can increase the false-positive rates [1]. Nonetheless, in a co-registered manner, when an ultrasound image is used as prior information for another breast imaging modality, USI has the potential to make diagnosis more accurate. Previously, we presented the early results of a near-field radar imaging (NRI) system, developed as an add-on unit to the Digital Breast Tomosynthesis to enhance its low radiological contrast. In this work, the early results of a bimodal, USI-NRI, imaging system is presented by adding an ultrasound sensor to our previous system. A simple experimental configuration was utilized for the purpose of proving the concept. The initial results of this study can open the way for safer (in terms of radiation) and more accurate breast imaging in future.
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Loos, Gary C., Timothy W. Sinor, and J. M. Abraham. "Aluminum Gallium Arsenide/Gallium Arsenide Photon Counting Cameras for Very Low Light Level Wavefront Sensing." In Adaptive Optics. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/adop.1996.atha.2.
Повний текст джерелаАнотація:
The feasibility of using adaptive optics (AO) systems on large ground based optical telescopes for producing compensated images of both astronomical sources and artificial earth satellites has been demonstrated by a number of research groups. AO systems consist conceptually of a wavefront sensor (WFS) which measures atmospherically induced wavefront phase perturbations faster than the rate at which they occur and a wavefront phase compensation device, typically a deformable mirror, which takes the WFS data and produces a conjugate phase correction nulling the distortion. In the case of faint sources, the ability of an AO system to produce phase corrections is limited by the signal-to-noise ratio (SNR) in the WFS. In the case of the Shack Hartmann (SH) WFS this limit is a function of the SNR required to estimate with sufficient accuracy the centroid positions of unresolved images of the source formed by a lenslet array on an array of quadrant detectors composing the subapertures of the WFS. Although the use of laser guidestars may allow the substitution of faint source radiation with a bright artificial AO beacon, considerations of cost and complexity motivate a continuing interest in improving the detection sensitivity of a source referenced, low light level (LLL) WFS. This paper explores the promise of aluminum gallium arsenide/gallium arsenide (AlGaAs/GaAs) heterostructure photocathodes coupled to shot noise limited photon counting (PC) cameras and compares their performance with the read noise limited charge coupled device (CCD) cameras often used in this application. Figure (1) illustrates the quantum efficiency of the various detectors to be considered in the study, including two high performance AlGaAs/GaAs photocathodes recently obtained from Litton Electro-Optical Systems.
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Soysal, D., and A. Ansar. "Novel Insights into Liquid Behavior in Atmospheric Plasma Jets." In ITSC 2012, edited by R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, A. McDonald, and F. L. Toma. ASM International, 2012. http://dx.doi.org/10.31399/asm.cp.itsc2012p0816.
Повний текст джерелаАнотація:
Abstract Infrared images are used to characterize the atmospheric plasma and the influence of the liquid injection. In the infrared spectral range of low energies of the rotational vibrational transitions can be captured, which are emitted by hot liquid vapors. In addition, the combustion of organic liquids like ethanol and pentanol can be seen directly with an increase of the emitted radiation. The examination of the spray clouds suggests a correlation between Ohnesorge number and the spray angle. Lower Ohnesorge numbers lead to more focused vapor beams.