Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 84-91).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Ansari, Armin, Committee Member ; Hertel, Nolan, Committee Chair ; Wang, Chris, Committee Member. Includes bibliographical references.

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Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser.

There is increasing interest in the use of small field of view (SFOV) portable gamma cameras in medical imaging. A novel hybrid optical-gamma camera (HGC) has been developed through a collaboration between the Universities of Leicester and Nottingham. This system offers high resolution gamma and optical imaging and shows potential for use at the patient bedside, or in the operating theatre. The aim of this thesis was to translate the HGC technology from in vitro laboratory studies to clinical use in human subjects. Pilot studies were undertaken with the HGC as part of this thesis. Furthermore, efforts have been made to transform the HGC technologies into a new medical device, known as Nebuleye. Initial physical evaluation of the pre-production prototype camera was carried out as part of the device developmental process, highlighting some aspects of the design that require further modification. A complete and rigorous testing scheme to assess the pre-production prototype camera has been developed and successfully implemented. The newly introduced tests enabled the system uniformity, system sensitivity, detector head shielding leakage, optical-gamma image alignment and optical image quality of the hybrid camera to be assessed objectively. This harmonised testing scheme allows characterisation and direct comparison of SFOV gamma cameras. In vitro and in vivo preclinical imaging was undertaken to examine the performance of the SFOV gamma cameras for experimental animal studies. The results of animal study have shown for the first time the feasibility and performance of these SFOV gamma cameras for imaging mice injected with a newly developed 111In labelled hybrid tracer. Further investigations are needed to improve the system resolution and prepare the camera system for combined gamma-near infrared fluorescence imaging in future. A systematic in vitro laboratory assessment method has been established to examine the imaging performance of the SFOV gamma camera in radioguided sentinel lymph node biopsy (SLNB) and radioactive seed localisation procedures for breast cancer surgery. Further preparatory work was undertaken to carry out a pilot clinical trial of the use of the pre-production prototype camera in sentinel node localisation procedures during breast cancer surgery. The clinical study protocol and routine quality control procedures have been established and are suitable for future use. Baseline data on the camera performance assessed using the routine quality control scheme have been obtained. Finally, the capabilities of the SFOV gamma camera were assessed. This has provided baseline data on user feedback and the imaging consequences on operator motion effects, as well as examining the detectability of a range of radionuclides, including 99mTc, 111In, 123I, 125I and 75Se. The first clinical results of the use of the HGC in clinical hybrid optical-gamma imaging in patients administered with 99mTc and 123I labelled radiopharmaceuticals have been reported. This clinical study has demonstrated the feasibility and capability of HGC in various clinical applications performed at the patient bedside, which included patients undergoing bone, thyroid, lacrimal drainage and lymphatic imaging as well as DaTscan studies. In conclusion, the work in this thesis has demonstrated the successful translation of an SFOV hybrid gamma camera for clinical use. This system would be ideally suited for use in the operating theatre for radioguided procedures such as sentinel node detection and tumour localisation. This system also offers potential for use with the new generation of hybrid fluorescent-radionuclide tracers currently under development.

When performing nuclear magnetic resonance (NMR) it is desirable to maximise the available polarisation of the spin system in order to achieve optimal signal-to-noise ratios. One method of achieving this is via the process of spin-exchange optical pumping (SEOP). SEOP can be used to produce hyperpolarised (HP) noble gases, which possess numerous applications in the fields of science and medicine, ranging from spectroscopic imaging of porous media to Magnetic Resonance Imaging (MRI) of the human lungs. The SEOP process involves transfer of angular momentum from circularly polarised laser photons to the electrons of an alkali metal vapour. Noble gas nuclei can then be polarised via collisions with the alkali metal vapour. Ultra-low frequency Raman Spectroscopy may be used to perform rotational temperature measurements of a nitrogen buffer gas in these SEOP experiments in real-time, in an attempt to understand the poorly understood and highly complex system dynamics and energy transport processes. The work contained in this thesis aims to investigate the co-dependence of these dynamics, in order to characterise the SEOP process in greater detail for a variety of gas mixtures, temperatures and alkali metal targets. With this, it is hoped that HP noble gases may be produced with greater efficiency, achieving faster build-up rates and higher net magnetisation. In addition to in situ Raman spectroscopy, additional diagnostic techniques were implemented in order to illustrate the co-dependence of variables during the thermal exchange processes present in SEOP. Low-field NMR spectroscopy was utilised to determine the 129Xe net spin polarisation (P_Xe) as a function of time and position within the SEOP vessel, whilst near-infra-red (NIR) optical absorption spectroscopy allowed an estimate of the alkali metal polarisation and global pump laser power absorption to be determined. Additionally, initial studies into the use of optical absorption spectroscopy at various wavelengths for determination of the alkali metal number density are discussed. A chronology of experiments conducted using an `in-line', optically filtered Raman probe arrangement will be presented, culminating in the development of a fully automated, single-axis translational stage to perform rapid measurement of the rotational nitrogen temperature (T_N2) within the optical pumping cell with a high degree of temporal and spatial precision. The automated nature of the system facilitates a >3-fold improvement in the rate of thermal data acquisition, with greater ease and reliability than the previous manual method. In addition to pure rubidium, rotational temperature determination via Raman spectroscopy is demonstrated in a variety of rubidium/caesium hybrid alloy mixtures. In this way it may be possible to more efficiently utilise the greater spin exchange rate of caesium with 129Xe to achieve hybrid Rb/Cs cross-polarisation. The result of this is the first observation of 129Xe polarisation in a hybrid Rb/Cs system exceeding that of an equivalent pure Rb system under otherwise identical experimental conditions.

Orientador: Solange Maria de Almeida / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-08T09:56:06Z (GMT). No. of bitstreams: 1 Lopes_SergioLucioPereiradeCastro_D.pdf: 9307649 bytes, checksum: f51f187aabfe9f5bd990e438d78272da (MD5) Previous issue date: 2007 / Resumo: O objetivo deste estudo foi avaliar a articulacao temporomandibular (ATM) de individuos portadores de Depressao Maior. A amostra foi constituida por 40 individuos diagnosticados por um medico psiquiatra, como portadores de Depressao Maior, segundo as diretrizes do DSM-IV (Manual de Diagnostico e Estatistica das Perturbacoes Mentais). Estes foram submetidos a exames clinicos e por imagem, que se constituiu de Ressonância Magnetica. Pela analise dos resultados, observou-se em relacao aos dados da anamnese, que a presenca da cefaleia recorrente foi a alteracao mais relatada, sendo citada como sempre presente (52,5% dos individuos) e ocasionalmente presente (47,5% destes). Em relacao ao exame clinico, a presenca de trajetoria mandibular alterada ocorreu em 85% dos individuos, sendo que 62,5% destes apresentaram desvio e 22,5% deflexao. Ruido articular, ocorreu em 70% das articulacoes (69% destas sendo estalido). Dor a funcao articular foi o sintoma mais observado, ocorrendo em 61,25% das articulacoes. No exame por imagem, o deslocamento de disco ocorreu em 54 articulacoes (67,5% da amostra), sendo o deslocamento sem reducao observado em 5 articulacoes (6,25%). Alteracao na posicao da cabeca da mandibula foi observada em 57 articulacoes (71,25% da amostra), sendo o posicionamento posterior o mais frequente, ocorrendo em 43 articulacoes (53,75%). Mobilidade anormal da cabeca da mandibula foi observada em 58 articulacoes (52 destas apresentaram hipermobilidade) (65%). Utilizando-se o Teste Exato de Fisher e o Teste do ?2 como analises estatisticas, observou-se nao haver relacao entre posicao do disco e dor a funcao da articulacao (p=0,34); entre funcao do disco e dor a funcao da articulacao (p=0,32); entre posicao do disco e dor muscular (p=0,40); entre funcao do disco e dor muscular (p=0,42) e entre posicao do disco e posicao da cabeca da mandibula (p=0,30). Verificou-se haver relacao entre posicao do disco e ruidos articulares (p=0,00) e entre posicao do disco e trajetoria mandibular (p=0,00). Somente um individuo apresentou dor, ruido articular e limitacao de movimentos da mandibula, sendo que este apresentava deslocamento de disco. Concluiu-se desta forma que, na amostra avaliada, a presenca de depressao maior nao foi um fator desencadeante para a desordem temporomandibular / Abstract: The aim of this study was to evaluate the temporomandibular joint (TMJ) of individuals with Major Depression. The sample comprised 40 individuals who were previously diagnosised as Major Depressed patients by a psychiatrist, using the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders). The subjects were submitted to clinical and imaging examination, which comprised TMJ magnetic resonance imaging. The result analysis showed that the headache was related as always present (52.5% of the individuals) or frequently present (47.5% of the individuals). With regard to clinical exam, the altered mandibular pathway occurred in 85% of the individuals, with 62.5% presenting deviation and 22.5% deflection. The joint noise occurred in 70% of the joints (69% cliking). Joint functional pain was the most frequent symptom observed, occurring in 61.25% of the joints. In the imaging exams, the disc displacement occurred in 54 joints (67.5% of the sample) the disc displacement without reduction was observed in 5 TMJ (6.25%). The mandibular condyle position was altered in 57 joints (71.25% of the sample) and the most frequent position observed was the posterior position (43 TMJ) (53.75%). Abnormal mandibular condyle mobility was observed in 58 joints (52 of then with hipermobility) (65%). Application of the Fisher¿s Exact Test and ?2 Test as statistical analysis revealed no relationship between disc position and joint functional pain (p=0.34);disc function and joint functional pain (p=0.32); disc position and muscle pain (p=0.40); disc function and muscle pain (p=0.42) and disc position and mandibular condyle position (p=0.30). A relationship was observed between disc position and joint noise (p=0.00) and between disc position and mandibular pathway (p=0.00). Only one individual reported pain, joint noise and limited mandibular movement, and this one presented disc displacement. Thus, it was concluded that the Major Depression presence was not an important appearance factor for the temporomandibular disorder, in this sample / Doutorado / Radiologia Odontologica / Doutor em Radiologia Odontológica

Les techniques d’ablations percutanées sont des procédés de radiologie interventionnelle ayant pour objectif la prise en charge mini invasive des pathologies tumorales. La technique la plus répandue est la radiofréquence. De nouvelles techniques (micro-ondes et la cryothérapie) ont fait leur apparition récemment élargissent le champ des possibles. A travers ce travail nous avons mis en avant différentes innovations significatives dans la prise en charge des patients tout au long de leur parcours. Nous avons tenté de montrer que les techniques émergentes telle que les micro-ondes sont des techniques fiables et reproductibles à condition que les volumes d'ablation soient déterminés in vivo. La sécurisation des procédures et la diminution des taux de complications constitue un point important permettant de renforcer le caractère mini invasif des ce techniques. Nous avons réussi à étudier la physiopathologie des pneumothorax survenus aux décours des radiofréquences pulmonaires, montré que la simple visualisation d'un trajet de RF après retrait de l'aiguille constituait un facteur de risque indépendant de pneumothorax et de mise en place de drain thoracique. Nous avons proposé une méthode originale permettant de combler ces trajets et montré le bénéfice significatif pour le patient en termes de survenue de pneumothorax et de mise en place de drain thoracique. Nous nous sommes enfin intéressés aux nouvelles modalités de suivi des patients, et notamment à l'émergence du scanner double énergie dans le suivi de ces patients pour lesquels il n'existe aucune modalité d'imagerie permettant de dépister les récidives précoces. / Percutaneous ablative techniques are interventional radiology procedures aimed at minimally invasive management of tumors. The most common technique is radiofrequency. New techniques (microwaves and cryotherapy) have emerged recently. Through this work we have put forward various significant innovations in the care of patients. We have tried to show that emerging techniques such as microwaves are reliable and reproducible techniques. The safety of procedures and the reduction of complication rates is an important point to reinforce the minimal invasiveness of these techniques. We have successfully studied the pathophysiology of pneumothoraxes occurring during pulmonary radiofrequency defects and showed that the simple visualization of an RF path after removal of the needle constituted an independent risk factor for pneumothorax and the placement of a thoracic drain. We proposed an original method to fill these pathways and showed significant benefit for the patient in terms of pneumothorax and chest tube placement. Finally, we were interested in the new ways of monitoring patients, and role of dual energy scanner in the follow-up of those patients for whom there is no imaging modality to detect early recurrences

Recently, systems that integrate positron emission tomography and magnetic resonance imaging (PET/MR) have become available for clinical use. This new technology, which combines the high spatial resolution and superior soft-tissue contrast of MR with the picomolar sensitivity, quantitative capabilities, and wide array of tracers of PET, has the potential to benefit patients and provide insights that were previously unattainable in standalone systems. Simultaneous measurement of PET and MR parameters provides complementary information, allowing for a more complete assessment of disease, as well as cross validation and calibration of MR and PET measurements and techniques. To take full advantage of such a multi-modal system, accurate quantification of the PET data is necessary. Due to the low spatial resolution of PET – which can be further reduced by external factors like patient motion – and the inherent lack of anatomic detail, accurate quantification can be challenging. The simultaneously acquired MR information provides an opportunity to optimize PET quantification and analysis. In order to fully realize the benefits provided by the simultaneously acquired MR data, the MR data cannot be treated as discrete sequences, but as the continuous flow of information. This is due to differences in the time required for data collection to generate PET and MR images. This work describes the development and optimization of a pipeline for the reconstruction and analysis of PET data in a brain-dedicated prototype PET/MR system, the BrainPET (Siemens Healthcare). First, the performance of the BrainPET system was optimized for neurological imaging. MR-hardware interference and characteristics of the PET camera were quantified and a method for multimodal alignment was developed. To simplify and streamline the reconstruction and quantification process, a platform was designed which utilizes the functionality of a number of specialized brain imaging analysis software packages in an automated fashion. Second, MR-based methods addressing specific challenges to PET quantification were addressed. Simultaneously acquired structural MR data was used to correct the PET data for attenuation and partial volume effects. The use of MR data for motion correction was addressed and a unified algorithm which derives motion estimates from the PET data when MR data is unavailable was presented. Finally, the value of the optimized PET processing for neurological studies was evaluated in three instances: first an upper limit on the physiologic noise introduced by MR imaging on cerebral metabolism was estimated using PET and found to be minimal; next the benefit of MR-based motion correction and partial volume effect correction were estimated in a patient study; and lastly, a method to derive the PET radiotracer input function from the PET data using multiple MR sequences was presented. / Biophysics

Study rationale The incidence, location, morphology and size characteristics of cerebral aneurysms in patients presenting to Groote Schuur hospital with either subarachnoid haemorrhage or 3 rd nerve palsy have not been established by a formal audit. Objectives To determine the patient demographics, frequency of CT angiographic detection of cerebral aneurysms and aneurysmal characteristics in patients presenting to Groote Schuur Hospital with sub-arachnoid haemorrhage and /or 3 rd nerve palsy Materials and methods Computed tomographic angiographic reports of cerebral vessels of patients who presented either with subarachnoid haemorrhage or 3 rd nerve palsy to Groote Schuur hospital were reviewed over a 19-month period from January 2018 – July 2019. The data obtained were coded, entered and analysed using IBM SPSS version 25 software. Descriptive statistics was used to report the means, modes and frequencies. Demographic and aneurysmal data were compared with a similar period 5 years previously. Results One hundred and twenty-one aneurysms (121) were analysed in 2018 -2019 and 124 in 2013-2014. The large majority were solitary (92% in both groups), small (94% and 90%) and saccular (96% and 87%) respectively. Significantly more fusiform aneurysms (13% vs 6%) were seen in the earlier group. 8 % of patients had multiple aneurysms. Less than 1% were ‘giant' ( >20mm). The mean age of the patients was the same for both periods (47 years). The mean aneurysm body size was 5.7mm and 7.1mm and the mean body: neck ratio was 6 2.1 vs 1.8b). Themost frequent locations were the posterior communicating artery (31.4% [2018/2019], 35% [2013- 2014]), anterior communicating artery (29% [2018/2019], 18.5% [2013/2014]) and the middle Cerebral Arteries (13.2% [2018/2019], 13.7% [2013/2014]). The least common sites were the Superior Cerebellar artery (SCA) [2018/2019] and the Vertebral artery (0.8%) [2013/2014]. Conclusion This study has compared the demographics of patients presenting to Groote Schuur Hospital with CT angiographically confirmed symptomatic intracranial aneurysms over two periods (January to July) 5 years apart. Both the patient demographics and the aneurysmal architecture were consistent over these time periods. Further our findings conform to that described previously both in Southern Africa and abroad i.e aneurysms which have bled are most commonly related to the posterior communicating, anterior communicating and the middle cerebral arteries and most aneurysms are small and saccular in shape. Over the periods studied, there was no change in the number of patients presenting to Groote Schuur Hospital for CT cerebral angiography and Interventional treatment post aneurysm rupture. These data represent a baseline for future statistical comparison and the information extrapolated from this study will be useful for interventive planning and resource mobilization at our institution and within the Western Cape Department of Health.