Thesis (M.S.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2005. Directed by Janet Hampikian. / Zhuqing Zhang, Committee Member ; Roger Narayan, Committee Member ; Brent Carter, Committee Member ; Janet Hampikian, Committee Chair. Includes bibliographical references.

published_or_final_version / Surgery / Master / Master of Medical Sciences

Thesis (M. Med. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 30-34).

published_or_final_version / Surgery / Master / Master of Medical Sciences

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xi, 140 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 117-128).

Thesis (Ph.D.)--George Mason University, 2008. / Vita: p. 83. Thesis director: Juan R. Cebral. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computational Sciences and Informatics. Title from PDF t.p. (viewed Aug. 27, 2008). Includes bibliographical references (p. 78-82). Also issued in print.

Thesis (Ph.D.)--George Mason University, 2008. / Title from PDF t.p. (viewed Oct. 14, 2008). Thesis director: Juan R. Cebral. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computational Sciences and Informatics. Vita: p. 98. Includes bibliographical references (p. 90-97). Also available in print.

Thesis (MSc (Radiography))--Cape Peninsula University of Technology, 2019 / Introduction: Intracranial aneurysm coil embolization is a fluoroscopically guided interventional procedure that is often preferred over surgical clipping for the treatment of intracranial aneurysms. Fluoroscopically guided procedures are associated with high levels of radiation doses which have the potential to induce skin injuries; and this necessitates adherence to radiation protection measures, especially the optimization of radiation exposure during fluoroscopically guided procedures. Optimization of radiation exposure can be achieved by applying the as low as reasonably achievable (ALARA) principle and by implementing diagnostic reference levels (DRLs). Monitoring and documentation of radiation doses at the end of each procedure is also essential to identify patients that are at risk of developing radiation-induced injuries for possible follow-up. Aim: This research study aimed to determine the average radiation dose to patients' thyroid glands and skin during intracranial aneurysm coil embolization. The objectives were to establish preliminary DRLs for intracranial aneurysm coil embolization; to ascertain whether the anatomical location of the intracranial aneurysm had an effect on the radiation dose and to compare the measured thyroid gland and skin doses to the Monte Carlo calculated doses. Methods: A prospective quantitative research study was conducted on 34 participants who had intracranial aneurysms that required coil embolization during the study period. Radiation doses to the anterior neck of participants, over the thyroid gland region, were measured using lithium fluoride thermoluminescent dosimeters (TLDs). In addition, the air-kerma area product (KAP) values were used to determine the participants' skin dose and the DRLs. Considering that it is not possible to perform direct thyroid measurements on human beings, phantom-based simulation studies were performed to evaluate the difference between the dose measured on the anterior neck and the dose measured directly on the thyroid gland. Three different aneurysm coil embolization scenarios were simulated during the phantom-based simulation studies. TLDs were placed on the anterior neck and in the thyroid hole of the phantom, which represents the anatomical location of the thyroid gland, during each simulation. The thyroid and skin doses were also calculated using a Monte Carlo program. The measured thyroid gland and skin doses were compared to the doses obtained from Monte Carlo calculations. Results: The average percentage difference between the anterior neck doses and thyroid radiation doses was found to be 61%. This value was added to the radiation dose measured on the anterior neck of participants to obtain the thyroid absorbed doses during coil embolization procedures. The thyroid absorbed doses ranged between 3.2 and 20.95 mGy with a mean of 11.25 mGy. The KAP values ranged between 33 and 125 Gy.cm2. The DRL established during this study was 68 Gy.cm2, 616 image frames and 30 minutes of fluoroscopy time. There was no agreement between measured thyroid dose and calculated thyroid doses while there was strong positive correlation between measured and calculated skin doses. The results showed no statistically significant relationship between aneurysm location and the radiation dose. Conclusion: The skin doses in this research study were below the threshold doses suggested in the literature for deterministic effects of radiation. The study results therefore suggest that patients that undergo intracranial aneurysm coil embolization at the research site are not at risk of developing radiation-induced skin injuries. The established DRLs were also lower than internationally published DRLs for intracranial aneurysm coil embolization.

Despite facing technical issues (e.g., overfitting, vanishing and exploding gradients), deep neural networks have the potential to capture complex patterns in data. Understanding how depth impacts neural networks performance is vital to the advancement of novel deep learning architectures. By varying hyperparameters on two sets of architectures with different depths, this thesis aims to examine if there are any potential benefits from developing deep networks for segmenting intracranial aneurysms from 3D TOF-MRA scans in the ADAM dataset. / Master of Science / With the technologies we have today, people are constantly generating data. In this pool of information, gaining insight into the data proves to be extremely valuable. Deep learning is one method that allows for automatic pattern recognition by iteratively improving the disparity between its prediction and the ground truth. Complex models can learn complex patterns, and such models introduce challenges. This thesis explores the potential benefits of deep neural networks whether they stand to gain improvement despite the challenges. The models will be trained to segment intracranial aneurysms from volumetric images.

A retrospective review was made of the case records, angiograms and computed tomography (CT) relating to a total of 263 patients with subarachnoid haemorrhage (SAH) due to ruptured berry aneurysms who were admitted to the Department of Neurosurgery, Wentworth Hospital during the four years 1983-1986. The part of the thesis concerning vasospasm (VS) includes two independent studies on calcium blocker Nimodipine (NO) in the prevention and treatment of VS done by the author. The aim of the thesis is to analyse the management problems of aneurysmal SAH, and investigate factors influencing outcome in order to establish the best possible management policy. The results are discussed and related to the recent data from literature. The main factors influencing outcome were: clinical condition of the patient, the timing of admission and surgery, hypertension and hyperglycaemia on admission, presence of vasospasm and related CT appearance of a thick layer of blood or clot in subarachnoid haemorrhage (CT-Fisher 3). The systemic administration of the calcium blocker nimodipine did not reverse or prevent delayed vasospasm and caused serious adverse effects i.e. hypotension and hyperglycaemia. The results of the thesis suggest a change in management policy and timing of surgery should depend. on clinical condition of the patient on admission (Hunt & Hess grading)(HH I/II grade (HH as possible regardless of timing of admission and results of radiological investigations (CT, angiography). Early surgery (1-3 days) should be the aim of the effort including referral, transport and hospital organisation. III grade (HH surgery should be performed soon after day 10 post-SAH. Particular attention should be paid to the careful preparation and selection of patients for angiography. IV/V grade (HH in specialised units as s000n as possible, preferably neurological or neurosurgical wards, and operated on as soon as their grade improves or, in selected (by surgeon, radiologist and anaesthetist) cases by delayed surgery ( after day 10 post-SAH). / Thesis (M.Med.)-University of Natal, Durban, 1988.