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Dissertations / Theses on the topic 'DWI'

Author: Grafiati

Published: 4 June 2021

Last updated: 11 March 2023

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1

Scott, Franklyn Johnson. "Exploring Punishment for Driving While Intoxicated (DWI) and Driving Under Influence (DUI) Offenders." ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/554.

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Drinking and driving has been the focus of research since the 1960s, but researchers have not defined the meaning of punishment for offenders who continue to drink and drive. The purpose of this study was to explore the impact of punishment on driving while intoxicated (DWI) and driving under the influence (DUI) defendants to assess the likelihood of preventing subsequent offenses. This study also sought to describe the behaviors of defendants who are perpetrating multiple offenses. The protection motivation theory was the theoretical foundation of this qualitative case study. The sample included a diverse group of 16 men between the ages of 21 and 35 who were recruited via a flyer in traffic court. Participants were interviewed, and interview data were transcribed verbatim and then coded for themes relating to punishments and DWI/DUIs. Initial interpretations were subjected to member checking for greater trustworthiness of the final report. The results of this study showed that the participants accepted responsibility for the frequent behaviors of drinking and driving and for being too intoxicated to make the decision to drive prior to their arrest. The results of the analyses indicated that the participants responded well to the punishment and opted to change their behaviors. Allowing offenders to describe and own their behaviors could positively create social change in these individuals, thus preventing them from incurring future DWI and DUI arrest.

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2

Sauter, Ingo. "Wertigkeit der DWI-MRT in der Tumordiagnostik." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-117028.

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3

Cachola, Gonçalo da Silva Brissos Chimelas. "Dependence of IVIM-DWI estimations on acquisition parameters." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10914.

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Dissertação para obtenção do Grau de Mestre em Engenharia Biomédica
Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver conditions in the Western world. It is normally associated with health disorders such as obesity, diabetes and hypertriglyceridemia. The gold standard for the diagnosis and staging of NAFLD is liver biopsy, which is highly invasive and is associated with high morbidity and inherent sampling error. Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) is able to distinguish between true molecular diffusion and the pseudo-random motion of water molecules inside micro vessels. IVIM-DWI has emerged in the recent years as a possible alternative to probe tissue changes in NAFLD. However few studies have addressed the problem of the dependence of IVIM-DWI parameters on pulse sequence parameters. In order to study this dependence, two studies were carried-out: 1) A simulation study, where we studied the influence of acquisition parameters on the error and bias associated with IVIM-DWI parameters; 2) In-vivo study in order to test the performance of the b-value sequences derived from the simulation studies. Results showed that the parameter which is more affected by the acquisition parameters is D*. Furthermore, it was also shown that the higher the number of b-values used to sample the data, the better the estimation of IVIM-DWI parameters is. However, after a certain number of points and for low SNRs, the effect of noise in extra b-values counteracts the effect of having more data points. It was also shown that the b-value sequence that is used to sample the data greatly influences IVIM-DWI estimations. We concluded that the conventionally used b-value sequence does not provide optimum IVIM-DWI estimations. Furthermore, results show that different weights should be attributed to each IVIM-DWI parameter in order to obtain a better performance of the optimized b-value sequence. Also, it was seen that the influence of T2 relation effects should be accounted for in the IVIM-DWI model. Lastly, our study showed that in the presence of steatosis, the value D* significantly decreased while D only slightly decreased. However, the differences between patients with steatosis and healthy controls were extremely influenced by the number of b-values used, leading to different diagnosis depending on the number of b-values used in the acquisition.

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4

Green, Cailyn Florence. "Waiting Times and DWI, Court-Mandated Treatment Completion." ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/6899.

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Drivers under the influence of alcohol cause nearly one third of all fatal motor vehicle accidents. Ambulatory outpatient alcohol abuse treatment has been clinically shown to increase abstinence, which could decrease the chance of subsequent DWI offences. A barrier to successful completion is extended waiting periods prior to treatment engagement. The theory of patient waiting supports the longer a patient waits to begin treatment the lower the likelihood of successful completion. By exploring the impact of waiting times on DWI court mandated clients, referral courts and treatment facilities can work together to create a successful completion strategy for offenders. The research question focused on if days waiting can predict successful outpatient treatment completion in court mandated adults. The TEDS-D archival data set was used, consisting of data collected between 2006-2011 from federally funded substance abuse treatment centers throughout the USA. The variables time awaiting treatment, treatment level, gender, race, employment status, and age were used as controls. A logistic regression using a random sample of 4,947 participants determined days waiting was significant but weak in nature. The variables of employment status and age are stronger predictors of treatment completion. An interaction effect analysis of days waiting and age results in clients over 45 years old being significantly impacted by days waiting while younger clients are not. Court and treatment agencies can use this information to give priority intake appointments to older clients to increase chances of treatment completion.

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5

Norèn, Ulf, and Sebastian Palmred. "Magnetresonanstomografi med diffusionsprotokoll vid stroke : En retrospektiv deskriptiv studie." Thesis, Uppsala universitet, Radiologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296220.

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ABSTRACT Aim: The aim of this retrospective study was to identify which indications prompted an MRI examination using the protocol ”Brain screening/Stroke” and whether the screening revealed recent infarcts and their localisation. Method: The data, which was subtracted from RIS (Röntgeninformationssystem), covered all consultation responses from stroke-rounds performed during 2015 at Akademiska Hospital in Uppsala (UAS). A total of 235 patients underwent an MRI-examination using the protocol ”Brain screening/Stroke”. Of this total population, 9 patients with a suspected or confirmed tumour were excluded. The information was collected at UAS during the period 11-22 April, 2016. Results: No indications were reported from the material collected. Hence, the method was insufficient to give an answer to the question at hand. In the final selection of 226 patients, no stroke could be detected in 42 % of the cases, 23 % had recent infarcts, 21 % had both recent and old infarcts and 14 % had only old infarcts. By gender the results were as follows: Of the total population, 85 patients were female. In 48% of these cases no stroke was detected, 21 % had recent infarcts, 20 % had old infarcts and 11 % had both recent and old infarcts. The remaining 142 patients were male. In 38% of these no stroke was detected, in 27% of the cases both an old an a recent stroke were detected , in 24% of the cases a recent stroke was detected and 11% had only old infarcts. Looking again at the total population, the consultation responses mentioned only recent infarcts and where these were located. The majority of the recent infarcts detected, 23 % were located in the Lobes of the brain, followed by 16% in the Cortex of the brain, 16% in the Brainstem, 13% in the Cerebellum, 10 % were locaded in ”Other parts of the brain”, 8 % were in the Talamus, 7 % were in White matter and the final 6 % in the Basala ganglia. The total number of recent infarcts detected was 189. Conclusion: The main question for this study was to see if it was possible to discover acute infarcts, using diffusion weighted MRI, and the localisation of those discovered. The method chosen worked well, but to get a better overview, more studies should be done, examining infarcts in greater detail. This knowledge may, in turn, be used as a basis for stroke diagnosis. It might also be of interest to complete this study, with a more in-depth analysis of the connection between different kinds of infarcts and the patient’s gender and age.

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6

Leclair, Nadine Stéfanie. "Diffusionsgewichtete Ganzkörper-MR-Bildgebung bei Kindern mit Chronischer Rekurrierender Multifokaler Osteomyelitis." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-218109.

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Zielsetzung: Die Chronisch-Rekurrierende Multifokale Osteomyelitis/Chronische Nicht-bakterielle Osteitis (CRMO/CNO) ist eine seltene auto-inflammatorische Erkrankung, deren typische Symptome starke Knochenschmerzen und lokale Schwellungen sind. Da die Ursachen muskuloskelettaler Beschwerden bei Kindern und Heranwachsenden vielfältig sein können, ist die differentialdiagnostische Unterscheidung einer CRMO/CNO von anderen Erkrankungen, unspezifischen Schmerzen oder einer malignen Grunderkrankung als Quelle der Symptome schwierig. Neue Techniken wie die diffusionsgewichtete Bildgebung (DWI) in der Magnetresonanztomographie (MRT) erlauben Rückschlüsse auf die Gewebestruktur und können in bestimmten Fällen eine Unterscheidung zwischen entzündlichen und malignen Prozessen vereinfachen. Ziel dieser Studie war es daher, die Sichtbarkeit von CRMO-/CNO-Läsionen mittels der DWI-Ganzkörperbildgebung zu evaluieren und den potentiellen klinischen Wert zu untersuchen. Material und Methoden: Sechzehn Patienten mit bekannter CRMO/CNO wurden bei 3 Tesla untersucht. Das Untersuchungsprotokoll beinhaltete u. a. 2D Short Tau Inversion Recovery (STIR) und diffusionsgewichtete Sequenzen in axialer Schichtführung. Die Sichtbarkeit von Läsionen in der DWI und der STIR wurde von 2 Auswertern im Konsensus evaluiert. Für alle Läsionen und in der korrespondierenden Referenzlokalisation wurden der Apparent Diffusion Coefficient (ADC) ermittelt. Ergebnisse: Insgesamt wurden 33 Läsionen eingeschlossen (durchschnittlich 2 Läsionen pro Patient), die sowohl in der STIR als auch in der DWI sichtbar waren. Diese waren vornehmlich in den langen Röhrenknochen lokalisiert. Der mittlere ADC-Wert in Läsionen betrug 1283 mm2/s und war somit signifikant höher als in der Referenzregion, hier betrug der mittlere ADC 782 mm2/s. Im ADCVerhältnis (Läsion vs. Referenzregion) zeigten 82 % der Läsionen eine relative Signalintensitätssteigerung um mehr als 10 %, und 76 % (25 Läsionen) zeigten eine Intensitätssteigerung von mehr als 15 %. Der mittlere relative Signalintensitätsanstieg betrug 69 %. Schlussfolgerung: Diese Studie zeigt, dass die diffusionsgewichtete Ganzkörperbildgebung bei 3 Tesla zuverlässig bei Kindern durchgeführt werden kann. Die ADC-Werte waren in CRMO-/CNO-Läsionen im Vergleich zur Referenzregion signifikant erhöht. Daher wird die Ganzkörperbildgebung in Kombination mit klinischen Angaben von uns als vielversprechende Methode angesehen, um benigne inflammatorische Prozesse anhand der ADC-Werte von bestimmten Malignitäten zu unterscheiden.

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7

Eisenhauer, Jasmin. "Entwicklung zerebraler Läsionen in der MRT nach akuter Ischämie im definierten kurzfristigen Verlauf unter konservativer Therapie." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-224442.

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Beim akuten ischämischen Schlaganfall ist die Größe der initialen DWI-Läsion (Diffusions-gewichtete Sequenz) in der zerebralen MRT zur Abschätzung der Prognose des Patienten umstritten. Die Beobachtung des Verlaufs der DWI-Läsion in den ersten Tagen nach einem Schlaganfall scheint hierfür besser geeignet. Hierbei zeigt sich, dass ein Infarktwachstum eher mit einem schlechteren klinischen Ergebnis korreliert. Ein mögliches Infarktwachstum vorherzusagen ist deshalb von großem Interesse. Bei nicht-lakunären Infarkten, die durch Verschlüsse größerer Arterien verursacht werden, ist die Ausbreitung des Infarktkerns in zuvor minderperfundierte Areale (d.h. in die Penumbra), als Ursache eines Wachstums anerkannt. Die Penumbra wird als die Differenz zwischen DWI- und PWI-Läsionen (Perfusions-gewichtete Sequenz) angesehen, was als PWI/DWI-Mismatch bezeichnet wird. Unklar ist, ob dieses Mismatch-Konzept auch auf lakunäre Ischämien (DWI-Läsionen < 2 cm Ø) angewandt werden kann. Ziel dieser prospektiven Studie war, den Zusammenhang zwischen dem initialen DWI/PWI-Mismatch und der Infarktentwicklung im kurzfristigen Verlauf bei 100 konservativ behandelten Patienten zu untersuchen. Das Patientenkollektiv war hinsichtlich der Infarktsubtypen (lakunäre und nicht-lakunäre) als inhomogen einzustufen. Am Tag der Aufnahme und an Tag 7 wurden anhand eines MRT-Schlaganfallprotokolls die Volumina der DWI und PWI-Läsionen, die Mismatch-Volumina, das Infarktwachstum, das relative Mismatch und das relative Infarktwachstum untersucht. Das Infarktwachstum zeigte einen engen Zusammenhang mit dem initialen DWI/PWI-Mismatch. Dies traf vor allem dann zu, wenn man die relativen Werte betrachtete. Hieraus ergibt sich, dass ein großes initiales Mismatch ein späteres Infarktwachstum wahrscheinlicher macht. Für die Zukunft könnte man daher davon ausgehen, dass das relative Mismatch, bezogen auf die relative Infarktentwicklung, einen besseren prognostischen Wert aufweist, als die absoluten Werte.

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8

Harisanto, Eddy S. "The dual function of the Indonesian Armed Forces (Dwi Fungsi ABRI)." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277237.

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9

Krisnawati, Lucia Dwi [Verfasser], and Klaus [Akademischer Betreuer] Schulz. "Plagiarism detection for Indonesian texts / Lucia Dwi Krisnawati ; Betreuer: Klaus Schulz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/111406808X/34.

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10

Krisnawati, Lucia D. [Verfasser], and Klaus [Akademischer Betreuer] Schulz. "Plagiarism detection for Indonesian texts / Lucia Dwi Krisnawati ; Betreuer: Klaus Schulz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/111406808X/34.

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11

Bilk, Philip [Verfasser]. "Funktionelle und diagnostische MR-Bildgebung der Transplantatniere mittels DWI und ASL / Philip Bilk." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2013. http://d-nb.info/1043587403/34.

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12

Christiansen, Thomas J. (Thomas James). "Planning strategies as predictors of DWI recidivism for problem and non-problem drinkers." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332485/.

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This study investigates the relationships between planning strategies on how to avoid future DWI arrest and actual DWI recidivism for a group of problem and non-problem drinkers. A sample of 75 individuals who were arrested for DWI and completed a DWI training program in 1987 was gathered.

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13

Borges, Renato Callado. "Ferramentas computacionais para a síntese de imagens de difusão por ressonância magnética." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-23042014-120357/.

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Trabalhos anteriores sobre a síntese de imagens de difusão por ressonância magnética se limitaram a estudos sobre estruturas microscópicas, menores que as dimensões típicas de um voxel (e.g., [BF08] [BF13] [LFS + 10] e [BA94]). Isto decorre em parte devido às metodologias utilizadas, que têm como ponto em comum serem simulações de tipo Monte Carlo, nas quais os elementos mínimos da simulação são as partículas de água. Portanto o custo computacional destas simulações é proporcional ao número de partículas a simular, e isto limita os volumes que podem ser simulados a tamanhos microscópicos. Propomos uma metodologia alternativa, que utiliza a imagem T 2 de uma amostra para sintetizar imagens de difusão por ressonância magnética. Os elementos mínimos desta nova metodologia são os pontos da imagem T 2 , e portanto seu custo computacional é proporcional à resolução da imagem T 2 utilizada, o que permite a síntese a partir de amostras de qualquer tamanho físico. Estas sínteses são realizadas por meio da integração numérica da equação do artigo seminal de Stejskal e Tanner [ST65] que relaciona a atenuação do sinal de ressonância magnética devida à difusão com os parâmetros da sequência de pulsos PGSE. Usamos os parâmetros típicos dessa sequência (b, gamma, tau\', g 0, g, delta e Delta), que podem ser configurados explicitamente em máquinas de ressonância magnética, para calcular valores do coeficiente de difusão aparente D em direções arbitrárias. Desenvolvemos software, disponibilizado [Bor] por licença GPL [Fou07], para realizar estas simulações, e para especificar uma máscara de direções, útil para modelar a difusão de uma amostra. Estas ferramentas permitem o estudo sistemático das variações dos parâmetros na síntese de imagens de difusão por ressonância magnética. Apresentamos um estudo de um fantoma de capilares imersos em água, exemplificando como utilizar as ferramentas para investigar a influência destes parâmetros na difusão da água da amostra.
Previous work on the synthesis of diffusion-weighted magnetic resonance imaging are limited to microscopic structures, smaller than the typical dimensions of a single voxel (e.g., [BF08] [BF13] [LFS + 10] and [BA94]). This is consequence, in part, of the methodologies used, that have in common the adoption of Monte Carlo simulation strategies, in which the minimal elements of simulation are the water particles. Therefore the computational cost of these simulations is proportional to the number of particles to simulate, and this limits the volume to be simulated to microscopic sizes. We propose a novel methodology, that uses the T 2 image from a sample to synthesize diffusion-weighted magnetic resonance images. The mininal elements of this novel methodology are the points of the T 2 image, and therefore its computational cost is proportional to the resolution of the T 2 image to be used, which allows the synthesis from samples of any physical size. These syntheses are made through numerical integration of the equation from the seminal article by Stejskal and Tanner [ST65] that relates the attenuation of the magnetic resonance signal due to diffusion to the parameters of the PGSE pulse sequence. We use the typical parameters of this sequence (b, gamma, tau\', g 0, g, delta and Delta), that can be explicitly configured in magnetic resonance machines, to calculate apparent diffusion coefficients D in arbitrary directions. We developed software, available [Bor] through GPL license [Fou07], to run these simulations, and to specify a mask of directions useful to model diffusion. These tools allow the systematic study of parameter variation in the synthesis of diffusion-weighted magnetic resonance images. We present a case study of a phantom made of capillary tubes immersed in water, to exemplify the use of these tools and how to investigate the influence of parameter variation on diffusion in the sample.

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Aavik, Julie Jensen. "Drunk - Driving, Relapse Pattern and Risky Driving Behavior Among Participants in a DWI Prevention Programme." Thesis, Norges teknisk-naturvitenskapelige universitet, Fakultet for samfunnsvitenskap og teknologiledelse, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11705.

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The overall aim of the study was to examine relapse among participants in the DWI Prevention Programme and those who get prison sentence after driving when influenced by alcohol and to examine the participants’ attitudes towards drunk – driving, risk behavior and traffic safety. A direct evaluation of the sentence and penal accomplishment is also examined. The sample of the survey study (see article 1) was 44 from the DWI – sample and 44 from the prison – sample that completed a questionnaire answering about their attitudes towards drunk – driving, risk behavior and traffic safety. The results presented in article 2 are based on transcripts of criminal convicts that participated in the DWI Prevention Programme during the period of 1998 – 2002 in the Salten District ( n = 68) and a sample of convicts to an unconditional sentence for drunk - driving in the same time periode (n = 112). The 1st analysis revealed that the DWI – sample had more ideal attitudes towards drunk – driving, risk behavior and traffic safety. There were also significant differences in how they evaluated their sentence and penal accomplishment. The DWI - sample were generally more satisfied with the penal accomplishment, the way they was treated and how the relationships around them were. They were also more satisfied with the contents of the penal accomplishment. Multivariate analysis, Kaplan – Meier and Cox regression was used in the 2nd analysis calculating if there were significant differences between the samples, survival time and to investigate effects of several variables upon the time a specified event takes to happen. In this study the relapse time was shorter for men than for women and the youngest age – groups had a shorter relapse time than the oldest age – groups. The Kaplan – Meier plot revealed that the prison – group have a shorter relapse time compared to the DWI – group. Based on the results of the two articles we can conclude that the DWI Prevention Programme had a very good effect on the participants compared to those who get traditional prison – sentence. The participants in the programme had the most ideal attitudes and the longest survival time after participating. When it comes to survival time among gender and age, women and the older age – groups had the longest survival time.

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Gaganis, Evanthia [Verfasser], and Wolfgang [Akademischer Betreuer] Reith. "Neue DWI-Läsionen beim Carotisstent mit und ohne proximales Protektionssystem / Evanthia Gaganis ; Betreuer: Wolfgang Reith." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2016. http://d-nb.info/1166140059/34.

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16

Gottschling, Sebastian [Verfasser], Alexey [Gutachter] Surov, Andreas Gutachter] Bach, and Karl-Titus [Gutachter] [Hoffmann. "DWI und histologische Parameter von Meningeomen / Sebastian Gottschling ; Gutachter: Alexey Surov, Andreas Bach, Karl-Titus Hoffmann." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2018. http://nbn-resolving.de/urn:nbn:de:gbv:3:4-1981185920-142284.

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Fatayer, Jawad A. "Factors Related to the Perceived Effectiveness of the Adult Probation DWI Program From the Probationers' Perspective." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332507/.

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Using questionnaire survey generated data from the DWI Probation Program in Dallas County. This study investigated the factors related to the perceived effectiveness of that program from the probationers perspectives. The findings in this study indicate that the perceived effectiveness of the DWI program by the probationers is an area that calls for more research and investigations. The findings have shown that factors related to the perceived effectiveness of the program by the probationers have a profound effect on the efficiency of the program as a whole in order to achieve its stated objectives.

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Dávid, Christian [Verfasser], and Peter [Akademischer Betreuer] Bachert. "Motion Compensation for Free-Breathing Abdominal Diffusion-Weighted Imaging (MoCo DWI) / Christian Dávid ; Betreuer: Peter Bachert." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1208550330/34.

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Gottschling, Sebastian [Verfasser], Alexey [Gutachter] Surov, Andreas [Gutachter] Bach, and Karl-Titus [Gutachter] Hoffmann. "DWI und histologische Parameter von Meningeomen / Sebastian Gottschling ; Gutachter: Alexey Surov, Andreas Bach, Karl-Titus Hoffmann." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2018. http://d-nb.info/1210728257/34.

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20

Lewis, Benjamin C. "Radiotherapy Response Using Intravoxel Incoherent Motion Magnetic Resonance Imaging in Liver Patients Treated with Stereotactic Body Radiotherapy." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5821.

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Magnetic resonance imaging is utilized as an important tool in radiation oncology for delineation of healthy and cancerous tissues, and evaluating the functionality of those tissues, structures, and organs. Currently, the clinical imaging protocol at Virginia Commonwealth University includes anatomical imaging for tissue and structure delineation, and to observe treatment induced changes. Diffusion weighted imaging (DWI) is also acquired for calculation of apparent diffusion coefficient (ADC) values to provide quantitative information on tissue diffusivity and microstructure. However, anatomical images and ADC values may not display the true extent of changes in tissue. This work seeks to further utilize the capabilities of MRI and expand its role in treatment response monitoring for liver cancer patients treated with stereotactic body radiotherapy (SBRT). To do so, an imaging protocol and image analysis methodology to evaluate treatment changes on pre- and post-treatment image sets was developed. An extension of DWI, termed intravoxel incoherent motion (IVIM) imaging, was utilized to quantitatively assess levels of perfusion and diffusion within the liver and tumor. Acquisition of high-quality diffusion weighted images of the liver necessitated the development of an MR safe respiratory motion management device, which was designed, constructed and evaluated in this work. An imaging protocol was developed providing anatomical and functional images of the liver, acquired under breath hold, utilizing the respiratory motion management device. An IVIM parameter calculation and texture analysis workflow was developed using MATLAB, and applied to acquired data sets from multiple studies, including past clinical cases, investigator, healthy volunteer, and liver cancer patient . Differences in IVIM and texture analysis parameters were investigated for healthy and diseased tissue, and for select dose regions from pre- and post-treatment imaging sessions. Significant differences, at a voxel level, were found between healthy and diseased tissue, and pre- and post-treatment volumes, for multiple parameters, including apparent diffusion coefficient, pure diffusion, and perfusion, as well as for various texture features. Overall, this study showed the potential of IVIM and texture analysis to be used for discriminating between healthy and diseased tissues in the liver, and for indication of treatment response.

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Pesare, Maria Francesca. "Studio del tensore di diffusione per la differenziazione delle strutture renali." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10175/.

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La tecnologia della diffusion tensor imaging (DTI) è una tecnica non invasiva, che permette di effettuare una caratterizzazione in vivo di diversi tessuti, è una tecnica consolidata in ambito neurologico e rappresenta una metodica ancora da esplorare ma molto promettente in ambito renale. Questo lavoro di tesi si concentra in primo luogo sulla differenziazione di diverse strutture renali quali, la corteccia e la medulla del rene sano, le cisti del rene affetto dalla malattia policistica autosomica dominante e i carcinomi. La seconda parte del lavoro si concentra sui reni policistici, in quanto è una delle malattie genetiche più comuni e la principale causa di insufficienza renale e non è, ad oggi, stata adeguatamente affrontata in questo genere di studi. Il secondo obiettivo è, quindi, di valutare se la tecnica dell’imaging di diffusione potrebbe essere utile per fornire informazioni sullo stato della malattia e sul grado si avanzamento di essa. Sono stati implementati in Matlab gli algoritmi per la costruzione del tensore di diffusione a partire dalle immagini DWI e per la selezione delle ROI sulle varie regioni di interesse. I risultati ottenuti per l’analisi dei reni policistici dimostrano che per gli intervalli temporali considerati non è possibile correlare il valore di diffusività media del parenchima e lo stadio di avanzamento della malattia, stabilito dai valori di eGFR. Per quanto riguarda i risultati ottenuti dalla differenziazione delle diverse strutture renali la tecnica della diffusion imaging risulta essere potenzialmente in grado di differenziare i diversi tessuti renali e di valutare separatamente la funzionalità dei reni.

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Jepsen, Peter Austin. "Improvements in Diffusion Weighted Imaging Through a Composite Body and Insert Gradient Coil System." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3700.

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Diffusion Magnetic Resonance Imaging (DMRI) is a class of Magnetic Resonance Imaging (MRI) techniques with broad medical applications ranging from characterization of tumors and brain damage to potential prediction of stroke. Gradient coil and signal-to- noise ratio (SNR) constraints limit spatial resolution, accuracy, and scan time in DMRI. Achieving high b-values (measures of a scan's sensitivity to diffusion) often require scans with long diffusion gradient pulses, leading to significant magnetic resonance (MR) signal decay before the signal can be sampled. This signal loss reduces the accuracy of diffusion parameter estimation. The ability to sample the MR signal sooner while maintaining the same b-value is restricted by the maximum amplitude and slew rate of gradient coils. A composite system utilizing body and high-powered insert gradient coils can achieve high b-values more quickly, enabling a shorter delay between excitation and signal sampling and improved accuracy of diffusion parameter estimation. Alternately, such a system can achieve higher b-values at an equivalent delay between excitation and signal sampling. This thesis describes the implementation of such a system, experiment design for evaluating the benefits of the system to DMRI, and design of a diffusion phantom. Also included are a characterization of a composite system's improvements to DMRI based on analysis of experimentally-obtained data and simulation results validating those findings. Finally, recommendations for further improvements to diffusion MRI are given.

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Jelden, Michael [Verfasser], and Christian [Akademischer Betreuer] Rübe. "Untersuchungen zur diffusionsgewichteten MRT (DWI) in der Bestrahlungsplanung des nicht-kleinzelligen Bronchialkarzinoms / Michael Jelden ; Betreuer: Christian Rübe." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2017. http://d-nb.info/1135184577/34.

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Lambertini, Matilde. "La risonanza magnetica pesata in diffusione per la valutazione delle lesioni mammarie." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12215/.

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Nella pratica clinica la valutazione del tessuto mammario viene effettuata utilizzando tecniche come la mammografia convenzionale o la risonanza magnetica con mezzo di contrasto. Tuttavia queste tecniche presentano sensibilità e accuratezza limitata e non sempre permettono la differenziazione delle lesioni mammarie. Tra le diverse tecniche diagnostiche di imaging biomedico, la risonanza magnetica, con l’utilizzo delle più recenti metodiche di acquisizione come il diffusion weighted imaging, offre la possibilità di effettuare uno studio sia morfologico sia funzionale dell’organo in esame, senza utilizzare mezzi di contrasto o radiazioni ionizzanti. La tecnica di Diffusion Weighted Imaging (DWI) si basa sullo studio del moto diffusivo delle molecole d’acqua nei tessuti biologici ed è in grado di fornire rilevanti informazioni sulla struttura dei tessuti e sulla presenza di eventuali alterazioni patologiche. Il più recente sviluppo della DWI è rappresentato dalle tecniche IVIM (Intra Voxel Incoherent Motion): questo metodo studia la componente di diffusività e di perfusione nei tessuti biologici e potenzialmente potrebbe permettere di discriminare una lesione maligna da una benigna. Il lavoro di tesi nasce come una revisione della più recente letteratura relativa all’utilizzo della tecnica IVIM per fornire informazioni sullo stato della lesione mammaria e sul grado di avanzamento della stessa. In particolare, l’analisi di studio è concentrata nella valutazione dei metodi che permettono di ottenere i coefficienti specifici della tecnica.

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Goldmann, Torben [Verfasser], Kai [Akademischer Betreuer] Kallenberg, Michael [Akademischer Betreuer] Knauth, and Florian [Akademischer Betreuer] Stockhammer. "Diffusion-weighted Imaging (DWI) und Diffusion-tensor Imaging (DTI) zur Analyse möglicher Ausbreitungswege/-formen von malignen Gliomen / Torben Goldmann. Gutachter: Michael Knauth ; Florian Stockhammer. Betreuer: Kai Kallenberg." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044361387/34.

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Hohenhaus, Marc [Verfasser]. "MRT bei zerebralen Ischämien – Stellenwert von FLAIR-Gefäßhyperintensitäten und hochauflösender DWI-Sequenz sowie Risikofaktoranalyse bei Leistungssportlern / Marc Hohenhaus." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2014. http://d-nb.info/1046832913/34.

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Sihono, Dwi Seno Kuncoro [Verfasser], and Frederik [Akademischer Betreuer] Wenz. "Real-Time Ultrasound Image-Guidance and Tracking in External Beam Radiotherapy / Dwi Seno Kuncoro Sihono ; Betreuer: Frederik Wenz." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1204637644/34.

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Lampinen, Björn. "Protocol optimization of the filter exchange imaging (FEXI) sequence and implications on group sizes : a test-retest study." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-196327.

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Diffusion weighted imaging (DWI) is a branch within the field of magnetic resonance imaging (MRI) that relies on the diffusion of water molecules for its contrast. Its clinical applications include the early diagnosis of ischemic stroke and mapping of the nerve tracts of the brain. The recent development of filter exchange imaging (FEXI) and the introduction of the apparent exchange rate (AXR) present a new DWI based technique that uses the exchange of water between compartments as contrast. FEXI could offer new clinical possibilities in diagnosis, differentiation and treatment follow-up of conditions involving edema or altered membrane permeability, such as tumors, cerebral edema, multiple sclerosis and stroke. Necessary steps in determining the potential of AXR as a new biomarker include running comparative studies between controls and different patient groups, looking for conditions showing large AXR-changes. However, before designing such studies, the experimental protocol of FEXI should be optimized to minimize the experimental variance. Such optimization would improve the data quality, shorten the scan time and keep the required study group sizes smaller. Here, optimization was done using an active imaging approach and the Cramer-Rao lower bound (CRLB) of Fisher information theory. Three optimal protocols were obtained, each specialized at different tissue types, and the CRLB method was verified by bootstrapping. A test-retest study of 18 volunteers was conducted in order to investigate the reproducibility of the AXR as measured by one of the protocols, adapted for the scanner. Group sizes required were calculated based on both CRLB and the variability of the test-retest data, as well as choices in data analysis such as region of interest (ROI) size. The result of this study is new protocols offering a reduction in coefficient of variation (CV) of around 30%, as compared to previously presented protocols. Calculations of group sizes required showed that they can be used to decide whether any patient group, in a given brain region, has large alterations of AXR using as few as four individuals per group, on average, while still keeping the scan time below 15 minutes. The test-retest study showed a larger than expected variability however, and uncovered artifact like changes in AXR between measurements. Reproducibility of AXR values ranged from modest to acceptable, depending on the brain region. Group size estimations based on the collected data showed that it is still possible to detect AXR difference larger than 50% in most brain regions using fewer than ten individuals. Limitations of this study include an imprecise knowledge of model priors and a possibly suboptimal modeling of the bias caused by weak signals. Future studies on FEXI methodology could improve the method further by addressing these matters and possibly also the unknown source of variability. For minimal variability, comparative studies of AXR in patient groups could use a protocol among those presented here, while choosing large ROI sizes and calculating the AXR based on averaged signals.

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Miekley, Marcel [Verfasser], and Eugen [Gutachter] Ruckhäberle. "Evaluation der ASL-Bildgebung und höherer mathematischer Modelle der DWI-Bildgebung in der MRT-Mammographie / Marcel Miekley ; Gutachter: Eugen Ruckhäberle." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2019. http://d-nb.info/1178112616/34.

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Hansen, Heather Ann. "Developmental changes in connectivity between the amygdala subnuclei and occipitotemporal cortex." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556631333522481.

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Ohno, Ayami. "The comparison of high-resolution diffusion weighted imaging (DWI) with high-resolution contrast-enhanced MRI in the evaluation of breast cancers." Kyoto University, 2020. http://hdl.handle.net/2433/259003.

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Lucchi, Sofia. "La risonanza magnetica per la valutazione della funzionalità renale in pazienti affetti da malattia policistica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9301/.

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Scopo. La risonanza magnetica (RM) in diffusione (Diffusion Weighted imaging DWI) permette di ottenere dati quantitativi sul movimento dei protoni liberi in acqua mediante la valutazione di alcuni parametri tra cui il coefficiente di diffusione apparente (Apparent Diffusion Coefficient ADC). Questo parametro potrebbe essere usato per differenziare i diversi tipi di tessuti (cisti di diverso tipo, parenchima sano, parenchima non più funzionante, …) e stabilire il danno renale. Lo scopo del presente lavoro è quello di valutare la correlazione tra il valore di ADC e il tessuto renale al fine di verificare la potenziale capacità di questo parametro di offrire informazioni funzionali e poter predire l’insorgenza di cisti e quindi l’aumento di volume del rene. Materiali e Metodi. 11 pazienti di cui 2 donne e 9 uomini (età compresa tra i 55 e i 75 anni) sono stati sottoposti a esame RM con sistema ad alto campo 1,5T. Tutti i pazienti erano affetti da malattia policistica. Il protocollo prevedeva l’utilizzo di una sequenza SE-EPI pesata in diffusione, le immagini sono state acquisite per diversi valori di b-value (500 s/mm², 700 s/mm², 900 s/mm², e 1500 s/mm²). Risultati. Osservando i valori di ADC (coefficiente di diffusione apparente) ottenuti per diversi valori di b e in due differenti regioni del rene, corrispondenti a cisti e parenchima, si sono riscontrati valori diversi . Indipendentemente dal b-value, le cisti hanno un valore di ADC minore rispetto al valore di ADC delle zone parenchimali. Al crescere del b-value, tali valori diventano più piccoli. Conclusioni. La DWI permette di ottenere valori di ADC in grado di discriminare tessuti.

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Hagio, Tomoe, and Tomoe Hagio. "Parametric Mapping and Image Analysis in Breast MRI." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621809.

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Breast cancer is the most common and the second most fatal cancer among women in the U.S. Current knowledge indicates that there is a relationship between high breast density (measured by mammography) and increased breast cancer risk. However, the biology behind this relationship is not well understood. This may be due to the limited information provided by mammography which only yields information on the relative amount of fibroglandular to adipose tissue in the breast. In our studies, breast density is assessed using quantitative MRI, in which MRI-based tissue-dependent parameters are derived voxel-wise by mathematically modeling the acquired MRI signals. Specifically, we use data from a radial gradient- and spin-echo imaging technique, previously developed in our group, to assess fat fraction and T₂ of the water component in relation to breast density. In addition, we use diffusion-weighted imaging to obtain another parameter, apparent diffusion coefficient (ADC) of the water component in the breast. Each parametric map provides a different type of information: fat fraction gives the amount of fat present in the voxel, the T₂ of water spin relaxation is sensitive to the water component in the tissue, and the ADC of water yields other type of information, such as tissue cellularity. The challenge in deriving these parameters from breast MRI data is the presence of abundant fat in the breast, which can cause artifacts in the images and can also affect the parameter estimation. We approached this problem by modifying the imaging sequence (as in the case of diffusion-weighted imaging) and by exploring new signal models that describe the MRI signal accounting for the presence of fat. In this work, we present the improvements made in the imaging sequence and in the parametric mapping algorithms using simulation and phantom experiments. We also present preliminary results in vivo in the context of breast density-related tissue characterization.

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Shimizu, Hironori. "Comparison of acquired diffusion weighted imaging and computed diffusion weighted imaging for detection of hepatic metastases." Kyoto University, 2015. http://hdl.handle.net/2433/200435.

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35

Limasale, Yanuar Dwi Putra [Verfasser], Carsten [Akademischer Betreuer] Werner, Carsten [Gutachter] Werner, and Tilo [Gutachter] Pompe. "Engineering the transport of signaling molecules in glycosaminoglycan-based hydrogels / Yanuar Dwi Putra Limasale ; Gutachter: Carsten Werner, Tilo Pompe ; Betreuer: Carsten Werner." Dresden : Technische Universität Dresden, 2021. http://d-nb.info/1227833253/34.

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Utami, Dwi Amanda [Verfasser], Peter [Akademischer Betreuer] Kukla, and Miriam [Akademischer Betreuer] Pfeiffer. "Modern, equatorial carbonates from Kepulauan Seribu, Indonesia : facies, isotope geochemistry, and microplastic as a sedimentary component / Dwi Amanda Utami ; Peter Kukla, Miriam Pfeiffer." Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/1235180239/34.

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Mutke, Matthias Anthony [Verfasser]. "MRT Biomarker für Perfusion und Infarktdemarkierung : Arterial Spin Labeling und DWI-Quantifizierung bei Patienten mit chronischen und akuten zerebrovaskulären Erkrankungen / Matthias Anthony Mutke." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2017. http://d-nb.info/1126504238/34.

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Flammini, Lucia. "Studio e valutazione delle potenzialità della tecnica IVIM per la caratterizzazione dei carcinomi al seno." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12202/.

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Il carcinoma mammario rappresenta la forma di neoplasia più diffusa al mondo. Nel 2015 sono stati diagnosticati solo in Italia circa 48.000 nuovi casi di carcinomi della mammella femminile. La diagnosi del carcinoma mammario riveste un’importanza fondamentale in quanto minori sono le sue dimensioni al momento della diagnosi maggiori sono le probabilità di guarigione. Il complesso processo di sviluppo e crescita tumorale vede infatti una latenza di molti anni, durante la quale la malattia non manifesta sintomi che possono indurre il medico a sospettarne l’esistenza. Grazie al contributo delle indagini strumentali è possibile diagnosticare e la maggior parte delle volte prevenire l’insorgenza di metastasi diffuse. La diagnosi precoce non consente solo di ottenere altissime percentuali di guarigione ma consente alla paziente di poter essere curata con interventi sempre meno invasivi e soprattutto di poter evitare il ricorso alla chemioterapia. La mammografia a raggi x rappresenta la tecnica di imaging più utilizzata ed è anche la tecnica che attualmente consente di individuare il maggior numero di tumori in fase iniziale. Tuttavia alcune sue limitazioni relative in primo luogo alla quantità di radiazioni alla quale il paziente viene sottoposto e alla bassa sensibilità nel caso di tumori ad alta densità aprono la strada a tecnologie innovative. La risonanza magnetica è una di queste e sebbene sia ancora oggi considerata una tecnica non convenzionale, è l'oggetto principale degli studi attuali. In particolare la risonanza magnetica in diffusione permette di fare indagini morfologiche e funzionali del tessuto tumorale mammario. Le nuove tecniche di imaging come la DWI (Diffusion Weighted Imaging) presentano notevoli potenzialità. In questo elaborato, verranno analizzate, a partire dagli studi pubblicati più recentemente, le tecniche più avanzate basate su DWI in grado di distinguere i contributi di diffusione e perfusione per caratterizzare le lesioni al seno.

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Horsley, Laura. "Imaging biomarkers of the tumour microenvironment to assess early response in patients treated with anti-angiogenic therapy." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/imaging-biomarkers-of-the-tumour-microenvironment-to-assess-early-response-in-patients-treated-with-antiangiogenic-therapy(b051dfc5-d3ec-44a7-8fb6-a641626f0f89).html.

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Background: Angiogenesis is the process by which new blood vessels develop from existing vasculature and is a critical step in all tumours to facilitate growth beyond a few millimetres. As this process is largely inactive in physiological circumstances in adults, it represents an attractive therapeutic target in oncology. Drugs that target the angiogenic process are classified as anti-angiogenic agents. The first anti-angiogenic drug to be approved by the FDA was bevacizumab; a recombinant humanized monoclonal antibody against VEGF. Randomised studies in colorectal cancer (and other solid malignancies) have reported prolonged progression free survival and overall survival for bevacizumab. However, standard radiological criteria, Response Evaluation Criteria In Solid Tumours (RECIST), although widely employed to assess response to therapy in clinical trials, are generally insensitive to the predominantly cytostatic effects of anti-angiogenic and other targeted therapies. Alternative methods of predicting or assessing early response to such agents are needed, particularly given the cost and toxicity implications of such treatments. However, biomarkers to aid selection of patients for anti-angiogenic therapies, including bevacizumab, remain elusive. Purpose: To investigate Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI), Diffusion Weighted Imaging (DWI) and circulating angiocytokines, measured using an ELISA multiplex, as prognostic markers in patients with metastatic colorectal cancer treated with bevacizumab and chemotherapy. Results: Seventy patients were treated. DCE-MRI and DWI parameters showed good reproducibility with coefficient of variation between 3.7 to 23% for parameters. The median progression free survival, the primary end point of the trial, was 9.3 months. The overall response rate was 44%. The clinical variables which were significant for progression free survival on univariate analysis were: performance status (p=0.005), CEA (p=0.04) and serum LDH (p=0.005). Biomarkers which were significant for progression free survival on univariate analysis were serum VEGF-A (p=0.02), serum HGF (p=0.005), sVEGFR-2 (p=0.02). In each case, low values of the biomarker were associated with improved outcome. Multivariate analysis identified Ktrans (p=0.015), performance status (p=0.008) and serum HGF (p=0.003) as the most significant predictors of progression free survival. A prolonged progression free survival was associated with a good ECOG performance status, high Ktrans and low serum HGF.Conclusions: Whilst these results are encouraging, future work is required to establish whether HGF and Ktrans are prognostic markers for metastatic colorectal cancer and their precise role in the prediction of patients likely to benefit from treatment with bevacizumab.

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Bertani, G. A. "EMORRAGIA SUBARACNOIDEA: VALUTAZIONE NEUROPSICOLOGICA E CON RM 3T IN FASE PRECOCE: RISULTATI PRELIMINARI." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/233160.

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TITLE: Subarachnoid Hemorrhage: cognitive evaluation and 3T MRI imaging in the acute phase; preliminary results AUTHOR: Giulio Andrea Bertani ABSTRACT INTRODUCTION: Aneurysmal subarachnoid hemorrhage (SAH) is a cerebrovascular disease characterized by high mortality and severe complications, in particular hydrocephalus and vasospasm. Traditional imaging techniques and outcome assessment scales (GOS, MRS) are unable to clarify the complex pathophysiological mechanisms of the disease or to adequately evaluate the impact on cognitive functions. AIMS: To investigate patients in the acute phase after SAH by advanced neuroimaging techniques (MRI) and in-depth neuropsychological evaluations, in order to assess acute cognitive deficits and to connect them to the numerous clinical and radiological variables which affect the course of the disease. METHODS: In the setting of a larger ongoing observational study, we selected 23 adult patients suffering from aneurysmal SAH. Following aneurysm treatment (clipping or coiling), patients underwent 3T brain MRI with MRA within 48 hours and 7-10 days, using a dedicated protocol; in the same times patient underwent neuropsychological assessments for language, memory, executive functions, praxis, orientation and personal autonomy. Monitoring of arterial flow by means of Transcranial Doppler (TCD) was performed. RESULTS: the majority of patients had marked cognitive deficits in all areas examined after SAH, with only marginal improvements at time 2. Early MRI showed ischemic volumes of less than 2 ml in 17 cases, between 2 and 10 ml in 3 and greater than 10 ml in 1; at T2 6 new lesions were detected, 5 less than 2 ml and 1 between 2 and 10 ml. The neuropsychological assessments showed multiple relationships with clinical and radiological parameters, location and side of the aneurysm, hydrocephalus and vasospasm; the correlation with ischemic lesions showed contradictory results. CONCLUSIONS: This study documents the pronounced cognitive impairment following SAH, despite a modest load in terms of ischemic lesions detected by MRI. It confirms that some features of the disease, such as the location and lateralization of the aneurysm, and the type of treatment have a deep influence on cognitive performances in the short term. This research also puts the basis for future selection of a battery of tests specifically designed to detect early subtle neuropsychological abnormalities, which are often associated with severe complications of SAH.

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Utami, Anisa Dwi [Verfasser], Bernhard [Akademischer Betreuer] [Gutachter] Brümmer, and Stephan von [Gutachter] Cramon-Taubadel. "Price Formation in the Indonesian Beef Industry: The Role of Policy Intervention / Anisa Dwi Utami ; Gutachter: Bernhard Brümmer, Stephan von Cramon-Taubadel ; Betreuer: Bernhard Brümmer." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1128400669/34.

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[Verfasser], Mashoedah, Martin D. [Akademischer Betreuer] Hartmann, Surjono Herman [Akademischer Betreuer] Dwi, and Zamroni [Akademischer Betreuer]. "Developing instructional media integrated with learning style instrument for undustrial electronics study programs of vocational High Schools / Mashoedah ; Martin D. Hartmann, Herman Dwi Surjono, Zamroni." Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227198043/34.

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Riceputi, Giulia. "Valutazione funzionale delle lesioni al seno tramite nuovi parametri di perfusione e diffusione dall'imaging in risonanza magnetica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13207/.

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La tecnica di screening attualmente più diffusa è la mammografia a raggi X, che rappresenta il principale metodo diagnostico in fase precoce di neoplasia maligna alla mammella. Essa ha, però, una sensibilità solamente del 69-90% che può ridursi fino al 48% in caso di parenchima denso. Il principale rischio associato alla mammografia è l’esposizione alle radiazioni: i raggi X, infatti, ionizzano le molecole modificando la composizione dei tessuti incrementando la possibilità di incorrere nel cancro. I pericoli di questa tecnica diagnostica sono stati dimostrati da diverse ricerche indipendenti[6]. Un’ulteriore tecnica diagnostica per il carcinoma mammario è la risonanza magnetica con mezzo di contrasto (DCE MRI). La risonanza magnetica con mezzo di contrasto è un importante strumento per la rilevazione e la caratterizzazione delle lesioni al seno con una sensibilità del 90% ma con una specificità che varia ampiamente fra il 30% e l’84%. I mezzi di contrasto rappresentano in genere dei mezzi sicuri per l’organismo: generalmente effetti collaterali e reazioni sono rare ma non è escluso che possano verificarsi. È in questo scenario che si stanno aprendo nuove prospettive per l’imaging diagnostico mammario. Una nuova tecnica, la Diffusion Weighted Imaging (DWI), un tipo di risonanza magnetica senza mezzo di contrasto che sfrutta le proprietà di diffusione dell’acqua, si sta sempre più affermando come metodologia diagnostica. Nel presente elaborato di tesi verranno studiate le potenzialità di queste nuove tecniche per caratterizzare le lesioni al seno attraverso lo studio dei parametri di diffusione e di perfusione.

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Cherillo, Francesco Antonio. "Trattografia con tensore di diffusione in risonanza magnetica: nuove frontiere per la neurochirurgia oncologica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19867/.

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Una grande sfida per la ricerca oncologica è la diagnosi precoce e la terapia in distretti anatomici di difficile raggiungimento farmaco-chirurgico. Uno di questi è il Sistema Nervoso. Questa tesi studia il principio di funzionamento dell’imaging di risonanza magnetica pesata in diffusione sino una particolare metodica di utilizzo con tensore di diffusione (TDI) con accenno alle potenzialità della trattografia. Dal confronto tra due pregevoli studi emerge che l’uso della trattografia basata su tensore di diffusione sia un’ottima integrazione d’imaging alla classica scansione RM, importante nel planning preoperatorio. In particolare, per tumori situati in sedi funzionali, sembra che l’informazione derivante dall’analisi trattografica possa determinare un miglioramento sostanziale dei sintomi del paziente limitando i postumi con effetti invalidanti. Grazie al miglioramento delle tecniche di imaging e allo sviluppo di procedure mini-invasive in microchirurgia, tali complicanze sono decisamente diminuite. A tal scopo la trattografia basata su tensore di diffusione, rispetto a scansioni standard di RM, fornisce informazioni importanti sulla localizzazione dei tratti corticospinali, e strutture nervose peritumorali. La potenza della trattografia, con alla base l’imaging a tensore di diffusione, può essere sfruttata in un intervento chirurgico grazie ai principi della neuronavigazione. Grazie alla scienza emergente della connettomica, strettamente collegata al tensore di diffusione, è possibile migliorare i dati quantitativi basati su un concetto di “rete cerebrale”, gli approcci e il planning chirurgici riducendo al minimo il rischio operatorio. Da tale metodica di imaging pare essere possibile derivare parametri che consentono di collegare la patologia della sostanza bianca al quadro clinico, monitorare la plasticità cerebrale, il recupero della funzione post-chirurgica e utilizzare la connettomica come biomarker.

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Rini, Dwi Setyo [Verfasser], Erwin [Akademischer Betreuer] Grill, and Ruiz Ramón Angel [Akademischer Betreuer] Torres. "Positional cloning and physiological analysis of novel Arabidopsis mutants involved in drought stress signalling / Dwi Setyo Rini. Gutachter: Ramón Angel Torres Ruiz ; Erwin Grill. Betreuer: Erwin Grill." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1072224798/34.

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46

Higueras-Esteban, Alfredo. "Multimodal 3D computer planning system for the implantation of stereotactic electrodes in refractory epilepsy." Doctoral thesis, Universitat Pompeu Fabra, 2021. http://hdl.handle.net/10803/672880.

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Neurosurgery is evolving towards the use of minimally invasive procedures. In this dissertation, we present several tools designed to fulfill the multimodal and multidisciplinary requirements of Stereoencephalography (SEEG) and epilepsy surgery. The resulting planning platform, named SYLVIUS, provides a digitalized workflow intended to facilitate clinical decision-making which has been used in Hospital del Mar, Barcelona for the evaluation of nineteen SEEG implantations. The platform allows for 3D-stereo visualization and interaction with head-tracking capabilities, providing novel interaction tools for the analysis of vascular and tractography data. Also, we present a clinical study of the risks and benefits of using digital subtraction angiography (DSA) performed with SYLVIUS. Finally, we describe two interactive trajectory planning tools, one designed to early signal the presence of vascular structures near a trajectory, and another one to find avascular alternative paths to a given potentially dangerous one maximizing adherence to either the entry, the target, or the insertion angle of the initial trajectory.
La neurocirugía está evolucionando hacia el uso de procedimientos mínimamente invasivos. En esta disertación, presentamos varias herramientas diseñadas para cumplir con los requisitos multimodales y multidisciplinarios de la estereoencefalografía (SEEG) y la cirugía de epilepsia. La plataforma de planificación resultante, denominada SYLVIUS, proporciona un flujo de trabajo digitalizado destinado a facilitar la toma de decisiones clínicas que se ha utilizado en el Hospital del Mar de Barcelona para la evaluación de diecinueve implantaciones de SEEG. La plataforma permite la visualización e interacción en estéreo 3D con capacidades de seguimiento de la cabeza, proporcionando nuevas herramientas de interacción para el análisis de datos vasculares y de tractografía. Además, presentamos un estudio clínico de los riesgos y beneficios del uso de la angiografía por sustracción digital realizada con SYLVIUS. Finalmente, describimos dos herramientas interactivas de planificación de trayectorias, una diseñada para señalar tempranamente la presencia de estructuras vasculares cerca de una trayectoria, y otra para encontrar rutas alternativas avasculares a una trayectoria potencialmente peligrosa, maximizando la adherencia a la entrada, el objetivo o el ángulo de inserción.

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47

Giacalone, Elisabetta. "Graph-based analysis of brain structural connectivity using different diffusion MRI reconstruction techniques." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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Abstract:

Il cervello si può definire un network complesso in cui delle regioni sono interconnesse fra loro. L'imaging di risonanza magnetica pesato in diffusione (DWI) insieme alla trattografia, permettono di ricostruire i fasci di fibre assonali di sostanza bianca indagando la connettività strutturale tra le aree di sostanza grigia. Il "connettoma" risultante può essere analizzato e caratterizzato attraverso la graph theory. Il lavoro che ho sviluppato presso l'unità di RM funzionale del Policlinico S. Orsola-Malpighi, e il DIBINEM, Università di Bologna, si propone di ricostruire il connettoma tramite due diversi metodi trattografici probabilistici confrontando i risultati ottenuti da acquisizioni DWI con diverso numero di direzioni del gradiente di diffusione (NDGD), ma con rapporto segnale rumore (SNR) costante. È stata effettuata un’acquisizione a 66 e tre a 22-NDGD per 18 soggetti sani. Le scansioni a 22-NDGD sono state mediate fra loro per ottenere un SNR comparabile con le 66-NDGD (22avg) e poter confrontare correttamente i diversi NDGD. Questo tipo di analisi non è ancora presente in letteratura. Dopo aver segmentato il cervello in diverse aree è stata effettuata la trattografia, tramite gli algoritmi PROBTRACKX2 e iFOD2, per costruire un network pesato del connettoma. Abbiamo effettuato misure locali e globali sui network e analizzato le proprietà di small-world e l'organizzazione modulare. Tali misure sono state confrontate fra i diversi NDGD e algoritmi trattografici. Si è visto come PROBTRACKX2 risulti più sensibile alle variazioni del SNR nel confronto dei network a 22 e 22avg. Per entrambi gli algoritmi sono state misurate differenze significative fra i network a 66 e a 22avg suggerendo che l'aumento della risoluzione angolare influenza fortemente le proprietà del network. In particolare, a livello locale si evidenzia un'alterazione delle misure nodo-specifiche nelle zone della sostanza grigia profonda e nell'area fronto temporale, per entrambi gli algoritmi.

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Lv, Yating. "Application of resting-state fMRI methods to acute ischemic stroke." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-126910.

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Diffusion weighted imaging (DWI) and dynamic susceptibility contrast-enhanced (DSC) perfusion-weighted imaging (PWI) are commonly employed in clinical practice and in research to give pathophysiological information for patients with acute ischemic stroke. DWI is thought to roughly reflect the severely damaged infarct core, while DSC-PWI reflects the area of hypoperfusion. The volumetric difference between DWI and DSC-PWI is termed the PWI/DWI-mismatch, and has been suggested as an MRI surrogate of the ischemic penumbra. However, due to the application of a contrast agent, which has potentially severe side-effects (e.g., nephrogenic systemic fibrosis), the DSC-PWI precludes repetitive examinations for monitoring purposes. New approaches are being sought to overcome this shortcoming. BOLD (blood oxygen-level dependent) signal can reflect the metabolism of blood oxygen in the brain and hemodynamics can be assessed with resting-state fMRI. The aim of this thesis was to use resting-state fMRI as a new approach to give similar information as DSC-PWI. This thesis comprises two studies: In the first study (see Chapter 2), two resting-state fMRI methods, local methods which compare low frequency amplitudes between two hemispheres and a k-means clustering approach, were applied to investigate the functional damage of patients with acute ischemic stroke both in the time domain and frequency domain. We found that the lesion areas had lower amplitudes than contralateral homotopic healthy tissues. We also differentiated the lesion areas from healthy tissues using a k-means clustering approach. In the second study (see Chapter 3), time-shift analysis (TSA), which assesses time delays of the spontaneous low frequency fluctuations of the resting-state BOLD signal, was applied to give similar pathophysiological information as DSC-PWI in the acute phase of stroke. We found that areas which showed a pronounced time delay to the respective mean time course were very similar to the hypoperfusion area. In summary, we suggest that the resting-state fMRI methods, especially the time-shift analysis (TSA), may provide comparable information to DSC-PWI and thus serve as a useful diagnostic tool for stroke MRI without the need for the application of a contrast agent.

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Yu, Xue, and 于雪. "Imaging of peritoneal metastasis : evaluation of diagnostic performance of DWI-MRI and FDG-PET/CT, correlation of the functional indices and feasibility study based on amide proton transfer MRI." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193483.

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Introduction Peritoneal metastasis is advanced disease and is usually widely disseminated at the time of discovery. It is crucial to detect peritoneal metastasis at an early stage and to allow precise patient selection for the right treatments. Both fluorodeoxyglucose positron emission tomography/computed tomography (FDGPET/CT) and magnetic resonance imaging (MRI) are used in peritoneal metastasis detection. Standardized uptake value (SUV), derived from FDGPET/ CT can evaluate glucose metabolism in cells, whilst apparent diffusion coefficient (ADC) derived from diffusion-weighted MRI (DWI) is used for quantitative analysis of tumour cellularity. Amide proton transfer (APT) MRI is a novel imaging technique based on exchangeable amide protons as endogenous contrast agent and can measure the increased amide proton signal in malignant tissues indirectly through bulk water proton signals. This thesis aims to: 1) compare the diagnostic performance of FDG-PET/CT and MRI in peritoneal metastasis evaluation; 2) study the relationship between SUV and ADC in peritoneal metastasis; 3) investigate the feasibility of APT in peritoneal metastasis evaluation. Materials and Methods Patients with peritoneal metastasis detected on FDG-PET/CT were prospectively recruited for MRI. FDG-PET/CT and MRI images were reviewed independently by two radiologists in separate sessions. Diagnostic characteristics were calculated for both imaging techniques. SUVmax and SUVmean were obtained by placing ROIs on PET, while ADCmin and ADCmean were calculated by contouring lesions on DWI. APT MRI was performed using a single-slice turbo spin echo sequence, with a block of presaturation pulses at 33 frequency offsets. ROIs were placed on peritoneal metastasis and muscle on APT. Mean of integrated asymmetrical magnetic transfer ratio (MTRasym) over 3-4 ppm with respect to water resonance was calculated for peritoneal metastasis and muscle. Results Eight patients were recruited in this study with 128 anatomical sites evaluated. DWI/MRI had good diagnostic performance (sensitivity = 92%, specificity = 99%, accuracy = 98%) compared to that of FDG-PET/CT (sensitivity = 90%, specificity= 100%, accuracy = 98%). Thirty-four peritoneal metastases were selected for quantitative analysis. Significant inverse correlation was found between ADCmean and SUVmax (r = -0.528, p = 0.001) and between ADCmean and SUVmean (r = -0.548, p = 0.001). ADCmin was significantly and negatively correlated with SUVmax (r = -0.508, p = 0.002) and SUVmean (r = -0.513, p = 0.002). In the above study cohort, 6 patients underwent APT imaging with 8 peritoneal metastases evaluated. Seven lesions showed positive APT signal and one had negative APT signal. The mean APT signal for peritoneal metastasis was 2.28%±1.76%, significantly different from that of muscle (-2.79%±0.95%, p < 0.001). Conclusions In conclusion, both DWI/MRI and FDG-PET/CT had good diagnostic performance in peritoneal metastasis evaluation. The negative correlation between SUV and ADC suggested an inverse relationship between tissue metabolism and cellularity. APT MRI is feasible to generate sufficient contrast signal for peritoneal metastasis and has potential to discriminate peritoneal tumours from its surrounding soft tissue using integrated MTRasym as a quantitative marker. These functional indices allow understanding of the biological behaviours of peritoneal tumours and could act as adjuncts in peritoneal metastasis imaging.
published_or_final_version
Diagnostic Radiology
Master
Master of Philosophy

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50

Boyer, Peter Gerard. "A Study of Bioluminescent and Magnetic Resonance Imaging in Murine Glioblastoma Models." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408624457.

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