Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 220 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 69-74).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 73-78). Also available in electronic version.

Thesis (Ph. D.)--Washington State University, December 2007. / Includes bibliographical references (p. 138-148).

Thesis (M.S. in Biomedical Engineering)--Vanderbilt University, Aug. 2007. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Alabama at Birmingham, 2006. / Description based on contents viewed June 26, 2007; title from title screen. Includes bibliographical references.

Positron Emission Tomography (PET) plays an essential role in the management of patients with cancer. It is used to detect and characterise malignancy as well as monitor response to therapy. PET is a quantitative imaging tool, producing images that quantify the uptake of a radiotracer that has been administered to the patient. The most common measure of uptake derived from the image is known as a Standardised Uptake Value (SUV). Data acquired on the scanner is processed to produce images that are reported by clinicians. This task is known as image reconstruction and uses computational algorithms to process the scan data. The last decade has seen substantial development of these algorithms, which have become commercially available: modelling of the scanner spatial resolution (resolution modelling) and time of flight (TOF). The Biograph mCT was the first scanner from Siemens Healthcare to feature these two algorithms and the scanner at Central Manchester University Hospitals was the first Biograph mCT to go live in the UK. This PhD project, sponsored by Siemens Healthcare, aims to evaluate the effect of these algorithms on SUV in routine oncology imaging through a combination of phantom and patient studies. Resolution modelling improved visualisation of small objects and resulted in significant increases of uptake measurements. This may pose a challenge to clinicians when interpreting established uptake metrics that are used as an indication of disease status. Resolution modelling reduced the variability of SUV. This improved precision is particularly beneficial when assessing SUV changes during therapy monitoring. TOF was shown to reduce image noise with a conservation of FDG uptake measurements, relative to non-TOF algorithms. As a result of this work, TOF has been used routinely since mid-2014 at the CMUH department. This has facilitated a reduction of patient and staff radiation dose and an increase of 100 scans performed each year in the department.

BACKGROUND: Migraine is a primary headache disorder that has a high prevalence and burden of disease throughout the world. Migraine symptoms include throbbing head pain, nausea, hypersensitivity to light, sound, and smell, and autonomic, cognitive, emotional, and motor disturbances. About a third of migraineurs have aura symptoms which are transient neurological symptoms with gradual onset before the migraine attack, visual disturbances, sensory loss, and/or communication impairment. The trigeminovascular system, central descending modulation, and brainstem descending modulation have been implicated in the pathophysiology of migraine. However, the exact neurovascular mechanism for migraine has not been determined. Several imaging techniques have been used to find structural and functional brain changes in migraineurs. OBJECTIVE: In order to further existing knowledge of migraine pathophysiology, structural brain differences were investigated using imaging between migraineurs and healthy individuals and differences within migraineurs. METHODS: Thirty-two patients with migraine (25 females) and 32 healthy control subjects (25 females) age-, ethnicity-, and gender-matched participated in our study. Magnetic resonance imaging (MRI) scans were collected from each participant. Then, voxel-based morphometry (VBM) was utilized to find any gray matter (GM) volume differences between migraine patients and controls. Also, VBM was performed in specific regions-of-interest (ROIs) to compare 11 migraine patients with aura (MA) and 11 migraine patients without aura (MO). RESULTS: A significant increase in regional gray matter volume difference was observed for migraine patients compared to control subjects in the intracalcarine gyrus of the visual cortex (corrected, p<0.05). In the VBM analysis of ROIs, the similarities between the MO and MA subjects included increases in the anterior cingulate cortex (ACC), hippocampus, insula, and intracalcarine cortex, along with decreases in the ACC and insula (uncorrected, p<0.05). MO subjects had decreases in the amygdala, hippocampus, intracalcarine cortex, and thalamus, but not in the MA subjects (uncorrected, p<0.05). The MA patients had increases in the amygdala and thalamus, but not in the MO patients (uncorrected, p<0.05). DISCUSSION: It can be concluded that the visual cortex is involved in the migraine mechanism since a large increase in GM volume difference was found in migraine, MO, and MA cohorts, as well as results from previous studies. Numerous GM volume changes in MO and MA cohorts reinforce evidence that particular brain regions are a part of migraine pathophysiology, but there were some regions that do not. Further research using imaging analysis and with larger study populations should be conducted to enhance our understanding of the migraine mechanism and differences that arise between migraine groups, so that diagnosis and treatment administration can be improved.

Hyperspectral imaging is the collection, processing and analysis of spectral data in numerous contiguous wavelength bands while also providing spatial context. Some of the commonly used instruments for hyperspectral imaging are pushbroom scanning imaging systems, grating based imaging spectrometers and more recently electronically tunable filters. Electronically tunable filters offer the advantages of compactness and absence of mechanically movable parts. Electronically tunable filters have the ability to rapidly switch between wavelengths and provide spatial and spectral information over a large wavelength range. They involve the use of materials whose response to light can be altered in the presence of an external stimulus. While these filters offer some unique advantages, they also present some equally unique challenges. This research work involves the design and development of a multichannel imaging system using electronically tunable Liquid Crystal Fabry-Perot etalons. This instrument is called the Liquid Crystal Hyperspectral Imager (LiCHI). LiCHI images four spectral regions simultaneously and presents a trade-off between spatial and spectral domains. This simultaneity of measurements in multiple wavelengths can be exploited for dynamic and ephemeral events. LiCHI was initially designed for multispectral imaging of space plasmas but its versatility was demonstrated by testing in the field for multiple applications including landscape analysis and anomaly detection. The results obtained after testing of this instrument and analysis of the images are promising and demonstrate LiCHI as a good candidate for hyperspectral imaging. The challenges posed by LiCHI for each of these applications have also been explored.

La conception des sondes ultrasonores pour l’imagerie médicale est traditionnellement basée sur l’utilisation de matériaux piézoélectriques. Depuis quelques années, est apparue la technologie des CMUTs, (Capacitive Micromachined Ultrasonic Transducers). Ces microsystèmes électromécaniques se présentent comme une alternative attractive à la piézoélectricité, offrant la possibilité d’explorer de nouveaux designs de sonde, et d’expérimenter de nouveaux modes d’imagerie. Ce travail s’inscrit dans une dynamique de développement et d’évaluation des sondes CMUTs, de la modélisation à la démonstration par l’image. Des transducteurs multi-éléments CMUTs ont ainsi été conçus, et des prototypes de sondes d’échographie finalisés ont pu être réalisés, ce en adaptant les développements à la transduction capacitive et aux systèmes d’imagerie conventionnels. Leurs comportements électroacoustiques et acoustiques ont été étudiés et comparés à des sondes standards. Finalement, des démonstrations par l’image ont été apportées, et les points forts de cette technologie pour l’imagerie médicale ont pu être établis. / Fabrication of ultrasound probes for medical imaging conventionally exploits piezoelectric based materials. CMUTs technology (Capacitive Micromachined Ultrasonic Transducers) has emerged about a decade ago. These electromechanical micro-systems are presented as an alternative transduction mode, and gives new opportunities for probe design and novel imaging techniques. This dissertation aims to develop and review CMUTs probes for ultrasound imaging, from modeling to imaging demonstration. Multi-elements transducers with CMUT technology have been thus developed, and ultrasound probes were successfully achieved. Developments have been carried out, taking care of both capacitive transduction and standard ultrasound systems. Electro-acoustic and acoustic behavior were evaluated and compared to the state of the art piezoelectric probes. Finally, quantitative imaging assessments have been performed and have pointed out the strengths of CMUT technology for ultrasound imaging

abstract: Magnetic resonance spectroscopic imaging (MRSI) is a valuable technique for assessing the in vivo spatial profiles of metabolites like N-acetylaspartate (NAA), creatine, choline, and lactate. Changes in metabolite concentrations can help identify tissue heterogeneity, providing prognostic and diagnostic information to the clinician. The increased uptake of glucose by solid tumors as compared to normal tissues and its conversion to lactate can be exploited for tumor diagnostics, anti-cancer therapy, and in the detection of metastasis. Lactate levels in cancer cells are suggestive of altered metabolism, tumor recurrence, and poor outcome. A dedicated technique like MRSI could contribute to an improved assessment of metabolic abnormalities in the clinical setting, and introduce the possibility of employing non-invasive lactate imaging as a powerful prognostic marker. However, the long acquisition time in MRSI is a deterrent to its inclusion in clinical protocols due to associated costs, patient discomfort (especially in pediatric patients under anesthesia), and higher susceptibility to motion artifacts. Acceleration strategies like compressed sensing (CS) permit faithful reconstructions even when the k-space is undersampled well below the Nyquist limit. CS is apt for MRSI as spectroscopic data are inherently sparse in multiple dimensions of space and frequency in an appropriate transform domain, for e.g. the wavelet domain. The objective of this research was three-fold: firstly on the preclinical front, to prospectively speed-up spectrally-edited MRSI using CS for rapid mapping of lactate and capture associated changes in response to therapy. Secondly, to retrospectively evaluate CS-MRSI in pediatric patients scanned for various brain-related concerns. Thirdly, to implement prospective CS-MRSI acquisitions on a clinical magnetic resonance imaging (MRI) scanner for fast spectroscopic imaging studies. Both phantom and in vivo results demonstrated a reduction in the scan time by up to 80%, with the accelerated CS-MRSI reconstructions maintaining high spectral fidelity and statistically insignificant errors as compared to the fully sampled reference dataset. Optimization of CS parameters involved identifying an optimal sampling mask for CS-MRSI at each acceleration factor. It is envisioned that time-efficient MRSI realized with optimized CS acceleration would facilitate the clinical acceptance of routine MRSI exams for a quantitative mapping of important biomarkers. / Dissertation/Thesis / Doctoral Dissertation Bioengineering 2016