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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Diffusion kurtosis imaging (DKI) in the human calf muscles

Lindquist, Mirabelle 17 February 2016 (has links)
Human calf muscle injuries are relatively common among individuals from various backgrounds. Miniscule tears in the muscles of the calf such as the medial gastrocnemius, lateral gastrocnemius, and soleus, may be difficult to identify using traditional imaging modalities. Diffusion kurtosis imaging (DKI), is one type of diffusion imaging that has presented with some strengths over diffusion tensor imaging (DTI) and diffusion weighted imaging (DWI). Though DTI studies in the human calf have been published, no DKI studies in the human calf exist to our knowledge. The objective of this study is to determine whether or not DKI is applicable in identifying quantitative changes between states of dorsiflexion and relaxation in the human calf. One female participant underwent DKI. Data from the scanning was quantitatively analyzed via the use of FSLView and the NODDI MATLAB toolbox. A change in mean voxel intensity in the calf and mean orientation dispersion index was identified in each of the five slices analyzed, in each muscle group (medial gastrocnemius, lateral gastrocnemius, and soleus). Most of the changes, whether an increase or decrease in mean value—between the states of dorsiflexion and relaxation—were statistically significant. We conclude that DKI may have a future in identifying physical/quantitative changes in calf muscles between the tense/relaxed states. Further studies using DKI on the human calf should be conducted in the future and address the limitations of the current study. Further investigation could possibly benefit individuals with miniscule calf muscle injuries.
2

Relationship between primary liver hepatocellular carcinoma volumes on portal-venous phase CT imaging

Aisaborhale, Ehimen Edward 12 March 2016 (has links)
The liver is an important organ in the body. It is located under the rib cage on the right side. The liver performs many important functions, it processes food for nutrients that the body requires and also helps in the detoxification of harmful materials. Like any organ in the body, the liver is susceptible to diseases such as liver cancer. Liver cancer is the growth and spread of unhealthy cells of the liver. There are several risk factor for liver cancer, these are: Cirrhosis (scarring of the liver), long term hepatitis B and hepatitis C infection and diabetes patients with long term drinking problem. Hepatocellular Carcinoma is the most common form of liver cancer in adult population which begins in the main type of liver cell (hepatocyte). Because Hepatocellular carcinoma starts from the primary liver cell itself (hepatocytes), as such it is a primary liver cancer. About 30,000 Americans are diagnosed with primary liver cancer yearly, making it an important disease that plaques our society and therefore needs proper diagnosis. In clinical evaluation of primary liver cancer such as HCC, the use of medical imaging technology has been commonplace. Most medical facilities across the country and globally typically use Computed Tomography (CT) and/or Magnetic Resonance Imaging (MRI) in the diagnosis and treatment follow up of Hepatocellular carcinoma. The medical imaging devices are used to determine the extent and volume of the tumor of the cancerous liver cells. In clinical trials involving the imaging of HCC tumors, the typical protocol used in the CT imaging of HCC involves the use of contrast enhanced dual phase acquisition. This approach is based on the physiology of the blood flow through the liver. Since HCC tumors are hypervascular in nature, it would thus be more apparent in the arterial phase of an acquired CT image. The aforementioned characteristic was tested with a volume paradigm which measure and compare the volume of both the arterial phase and portal venous phase acquired images in the experiment. Overall this study helps in furthering goals to reduce the patient dose from the x-ray tubes during clinical trials. The results of the experiments (n = 19, t = 0.67, p = 0.26), indicates no significant difference between the volume of the HCC tumor images acquired both in the AP and PVP.
3

Multiparametric 3 Tesla magnetic resonance imaging as a clinical tool to characterize prostate cancer

Dunn, Matthew Christopher 12 March 2016 (has links)
Scientists have come a long way in understanding prostate cancer as a disease and how its progression affects the men who develop it. Prostate adenocarcinoma may be present without causing clinical symptoms. Prostate cancer may metastasize, which increases the likelihood of fatality. The cause of the disease is still not completely clear, but genetics, race, tissue damage, history of previous infections, diet, and environmental influences appear to play a role in its development. Magnetic resonance imaging (MRI) has become an excellent clinical tool to characterize prostate cancer without the use of ionizing radiation or surgery. It is concluded that MRI is the optimal imaging modality to achieve detection, characterization, and staging of intracapsular and extracapsular prostate disease. The advances in MRI technology, particularly 3 Tesla, allows for reduced surgical intervention thus improving quality of life for patients with the disease.
4

Optic nerve atrophy: a comparison of two imaging modalities to evaluate their sensitivity for diagnostic purposes

Cheng, Anh-Dao M. 12 July 2017 (has links)
PURPOSE: To evaluate the efficacy of MRI as a diagnostic tool by comparing it to OCT in patients with suspected optic nerve atrophy. Currently, MRI is an established noninvasive imaging modality for tumors and inflammatory tissues; however their use in optic nerve atrophy is limited to advanced cases. Our study investigates the use of OCT, a more sensitive imaging modality, compared to MRI as a potential adjunct to the clinical diagnosis of optic nerve atrophy. METHODS: This retrospective study analyzed 27 medical records (40 eyes) of patients with suspected optic nerve atrophy referred to the Neuro-ophthalmology Clinic of the Beth Israel Deaconess Medical Center (2009-2016) who had both MR imaging of the orbits and SD-OCT scans. Based on the RNFL thickness obtained from OCT scans, optic atrophy was defined as border, mild, moderate, or severe. MRIs were used to measure the optic nerve area, optic nerve diameter and sheath area of all eyes. From there, the ratio of optic nerve area to sheath area, percent difference in optic nerve diameters in a patient and percent difference in optic nerve areas in a patient were determined. RESULTS: As atrophy worsens, the optic nerve area and sheath area seem to steadily decline. The ratio between the two seems to remain constant (0.27) regardless of degree of atrophy. Focusing on unilateral patients, the percent difference in optic nerve area with mild optic atrophy seemed minimal (14%). It becomes more significant in moderate and severe atrophy cases (56.06% and 26.18% respectively). Overall, there does not seem to be a strong correlation between MRI measurements and OCT RNFL values. CONCLUSIONS: Overall, a strong correlation was not found between MRI measurements and OCT RNFL thickness values. While a general trend existed, there was too much variation to determine cut off points for atrophy based solely on the measurement of a single eye. MRI may be useful in identifying severe and moderate optic nerve atrophy especially in unilateral patients. Once the RNFL thins to about 70 μm, the difference in size is detectable on MRI. For all cases of mild optic atrophy and bilateral moderate atrophy, OCT remains a more reliable imaging diagnostic. Changes in nerve size appear minimal compared to a healthy human. The optic nerve sheath was also shown to decrease in size in cases of atrophy. Future studies with a larger sample size are needed to produce more conclusive results.
5

Quantitative T1 mapping in cardiomyopathy

Hendry, Owen MacLeod 12 March 2016 (has links)
Recent advancements in techniques of Cardiac Magnetic Resonance Imaging provide extended quantitative measurements of myocardial T1. Important tissue characteristics can be tracked noninvasively to allow practitioners to quantify important properties of regional and global myocardium function. Quantification of these T1 measures involves the compilation of multiple images to create a T1 recovery curve, providing a map that estimates the T1 value as an encoded pixel value. After contrast injection, the data is compared with native (no applied contrast agent) T1 to examine myocardial disease involving the interstitium as well as the extracellular volume fraction. Myocardial T1 mapping is an emerging biomarker for quantification of myocardial disease (since an important indicator of heart disease is the expansion of myocardial interstitial space, as is fibrosis). This paper explores the detection and quantification of cardiac involvement using delayed gadolinium enhancement combined with T1 mapping and myocardial extracellular volume fraction. It extends the research being conducted on Cardiac sarcoidosis, an important cardiomyopathy. Cardiac sarcoidosis is a multisystem granulomatous disease of unknown etiology. Cardiac MR is able to detect the active, inflammatory phase of the disease as well as the chronic phase where scarring and fibrosis are dominant. The use of gadolinium-based contrast agents improves the ability to discriminate ischemic from nonischemic etiologies, owing to different patterns among the various nonischemic cardiomyopathies. Since gadolinium shortens T1 relaxation time, the result is a brighter signal intensity in areas with increased interstitial space on inversion recovery T1-weighted sequences. The 1.5 Tesla Philips Achieva XR Scanner was used to collect the pre- and post- contrast images from five anonymous patients (subjects), following the MOLLI protocol. These images were stacked and run through MRMap, which creates parametric image maps of the MOLLI data. Data was graphed employing the Gado Partition Coefficient.
6

Compressed sensing and undersampling k-space

Rahimpour, Yashar 08 April 2016 (has links)
In the field of medical imaging, one of the most important concepts consists of the creation of the image from an obtained signal. The creation of the image is broken down into a subset of tasks. The first is the basic concept of isolating the element crucial to creating an image. One example is the isolation of different atoms in different modalities, for example PET or SPECT. Second, is using the intrinsic properties of these atoms to create a signal that can be recorded, this is done by magnets, gradients, coils, and other technological advances specific to other imaging modalities. Third, is the method used to record the signal. This can be done in many different ways, including but not limited to, radon space and k-space. Last but not least is the transform of the data in their respective spaces into images that are read by technologists. What is described here is, a very simple explanation for the process that different modalities go through in order to create an image. This review paper will be focused mainly on k-space acquisition and the different ways that the acquisition of k-space and image creation can be accelerated to improve patient time spent in the machine.
7

Spectroscopic detection of pathological severity in Alzheimer's disease

Herpy, James Philip 12 July 2017 (has links)
Alzheimer’s disease (AD) has emerged as one of the most widespread and devastating forms of dementia. Over the past few decades, AD has consistently increased in prevalence worldwide due to the rising proportion of elderly individuals and lack of effective screening and treatment modalities. To date, few economically viable and widely applicable tools exist to make definitive, early diagnoses of the disease. Therefore, there is a clear need for interventions that facilitate accurate diagnoses, monitoring, and therapeutic treatment of AD. In the course of AD, cognitive impairment is preceded by physiological changes to the central nervous system (CNS). This includes neuronal atrophy, synaptic dysfunction, and the abnormal post-translational modification of the proteins tau and beta-amyloid (A), which contributes to the deposition of intracellular neurofibrillary tangles (NFTs) and extracellular neuritic plaques (NPs). The pathological cellular changes in AD occur long before the clinical course of the disease, and biomarkers for these changes can be detected prior to measurable cognitive decline. Because the biochemical changes associated with AD are irreversible, effective tools for diagnosis must detect the presence and severity of molecular pathology during the preliminary stages of the disease’s insidious onset. Biomarkers of AD can be detected by neuroimaging technologies, including magnetic resonance imaging (MRI), positron emission tomography (PET), and blood or cerebrospinal fluid (CSF) analyses. However, these methods are not currently suited to diagnose and monitor the unique pathogenesis of AD prior to cognitive decline. An ideal instrument for widespread AD screening, diagnosis, and monitoring must be noninvasive, inexpensive, portable, and accommodating to the cognitive sensitivities of patients on a spectrum from mild cognitive impairment (MCI) to full-blown dementia. Recently, several spectroscopic methods of assessing AD pathology have met these criteria and may be better suited for widespread clinical application. The objective of this thesis is to evaluate the use of near-infrared optical spectroscopy (NIRS) to detect pathological severity in human AD. Near-infrared (NIR) light is poorly absorbed by biological tissue, and can safely penetrate bone, skin, vasculature, and neuronal tissue. NIRS has traditionally been used in biomedical contexts to evaluate cerebral oxygenation changes, however the dense protein aggregates NFTs and NPs in AD tissue have recently been shown to characteristically affect several optical parameters of a NIR signal, including fluorescence and particle path (scattering). To date, applications of NIRS have been used to differentiate AD brains from non-AD controls in vitro, and further identify MCI patients in vivo, suggesting the NIR signal can identify molecular changes in AD. Severe AD cases are characterized by increased involvement of NFTs and NPs in the cerebral cortex, which would be expected to further affect the extent of NIR scatter. The current study aims to quantify AD-related pathology for investigation into whether the extent of optical scattering is correlated with the severity of amyloid plaque load and NFT density in the temporal cortex. Quantification of these lesions was accomplished using immunohistochemistry (IHC) and stereological analyses. Preliminary results show that the severity of AD pathology detected via IHC can be correlated with measured parameters of an in vitro near-infrared signal. Future studies aim to further characterize the relationship between scattering intensity and pathological severity, as well as evaluate the in vivo potential of this technology in predicting the clinical outcome and cognitive status of individuals in different stages of AD.
8

Assessment of the healing of vascularized fibula bone graft in the reconstruction of the mandible using computed tomography

Nadershahh, Mohammed 08 April 2016 (has links)
PURPOSE: Vascularized bone graft has become the standard for the reconstruction of large Mandibular defects, those with soft tissue defect or after radiation to the area. Fibula free flap represents the workhorse for simultaneous bone and soft tissue reconstruction of the Mandible. The aim of this study is to quantify bone formation, if any, in the graft-mandible and graft-graft gaps using computed tomography (CT) scans by developing a reliable threshold-based post-imaging processing tool, compare the healing of fibula to the mandible to the healing of the fibula to itself using this tool, and to investigate potential factors affecting bone formation specifically the linear distance between the bony edges during surgery. PATIENTS AND METHODS: This is a multicenter study centered at Boston medical center. DICOM images were analyzed using Osirix software (V.3.7.1, 32 bits) after blinding identifying data. The inclusion criteria for this study: 1) patients received a vascularized Fibula free flap for Mandible reconstruction; 2) patients who have at least 2 postoperative CT scans with at least one month interval; 3) the first CT is within the first 3 months after the surgery; 4) no signs of clinical failure of the graft or hardware failure. The reliability of this technique was tested using two independent blinded examiners. Each blinded examiner tested each scan three times. Pearson's correlation coefficient was used to assess inter-rater reliability while the mean, Standard deviation error, and standard deviation of the mean assessed the intra-rater reliability. Paired T-test was used to compare the amount of volume change over time in participants who had both graft-graft gaps and graft-Mandible gaps. Multiple linear regressions were used to investigate the relation between the initial linear distance between the bony edges of the gap, age, and time interval against the percentage of change in gap volume. All statistics were conducted using Microsoft excel software and SPSS. RESULTS: Twenty bony gaps from nine subjects were included in this study. This includes five graft-graft gaps and fifteen graft-Mandible gaps. The first post-operative CT scan was done within first three months after surgery (range= 2-77 days, mean= 22.2 days). Each subject had two CT scans with time interval ranging between 33 days to 390 days (mean= 191.1 days). The subjects' age ranged between 30 and 72 years (mean= 56.1 years). 12 bony gaps were used for assessing inter-rater and intra-rater reliability. The Pearson's correlation coefficient for inter-rater reliability was 0.94. Inter-reliability standard deviation error average was 0.03 and the standard error of the mean average was 0.003. Two-tailed paired T-test comparing the interval change in volume of graft-graft gaps to graft-Mandible gaps was 0.304. We found a significant negative correlation between absolute volume change and distance in mm (Pearson =-0.476, p-value=0.017). 22.7% of the variability in volume change can be explained by the initial linear distance between the bony edges of the gaps in millimeter. CONCLUSION: Small bony gaps between the fibula bone graft and the mandible after mandibular reconstruction can be reliably assessed. The healing of the fibula to itself was not found to be significantly different from the healing of fibula to the mandible in the same subject. The initial linear distance between the bone edges of the gap is inversely related to subsequent bone formation. It is recommended to adapt the bony segments as close as possible to increase bone formation.
9

Improved detection and characterization of obscured central gland tumors of the prostate: texture analysis of non contrast and contrast enhanced MR images for differentiation of benign prostate hyperplasia (BPH) nodules and cancer

Banaja, Duaa 03 November 2016 (has links)
OBJECTIVE: The purpose of this study to assess the value of texture analysis (TA) for prostate cancer (PCa) detection on T2 weighted images (T2WI) and dynamic contrast-enhanced images (DCE) by differentiating between the PCa and Benign Prostate Hyperplasia (BPH). MATERIALS & METHODS: This study used 10 retrospective MRI data sets that were acquired from men with confirmed PCa. The prostate region of interest (ROI) was delineated by an expert on MRI data sets using automated prostate capsule segmentation scheme. The statistical significance test was used for feature selection scheme for optimal differentiation of PCa from BPH on MR images. In pre-processing, for T2-WI, Bias correction and all images intensities are standardized to a representative template. For DCE images, Bias correction and all images are registered to time point 1 for that patient. Following pre-processing texture, features from ROI were extracted and analyzed. Texture features that were extracted are: Intensity mean and standard deviation, Sobel (Edge detection), Haralick features, and Gabor features. RESULTS: In T2-WI, statistically significant differences were observed in Haralick features. In DCE images, statistically significant differences were observed in mean intensity, Sobel, Gabor, and Haralick features. CONCLUSION: BPH is better differentiated in DCE images compared to T2-WI. The statically significant features may be combined to build a BPH vs. cancer detection system in future.
10

MRI overview for fat quantification in non-alcoholic fatty liver disease in the clinical and research settings

Kavanaugh, Ryan 13 July 2017 (has links)
The general purpose of this master’s thesis is to describe the MRI techniques used in scanning and post processing for quantifying liver fat percentages for the purpose of diagnosis and research. At the onset we will look at epidemiological data regarding nonalcoholic fatty liver disease, which is often called by the name of hepatic steatosis. Based on the prevalence of this disease it is worthwhile to fully understand non-invasive (MRI) analysis, and its use in the clinical and research setting. Following an introductory section regarding the basis of magnetic resonance imaging, we will take a more in-depth look at current methods utilized for liver fat quantification. Due to the massive population of those of suffer from this disease worldwide it is prudent to analyze current methods, as well as the implications that such research has and will have on the pharmaceutical approach to treating this disease. The purpose of this thesis is to elucidate the MRI techniques utilized for liver fat quantification and provide a comprehensive view of how these techniques are used for diagnosis in the clinical setting, and longitudinal studies in the research setting to measure liver fat levels and how they react to various treatment approaches.

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