Visual Perception and Cognition in Image-Guided Intervention

Surgical image visualization and interaction systems can dramatically affect the efficacy and efficiency of surgical training, planning, and interventions. This is even more profound in the case of minimally-invasive surgery where restricted access to the operative field in conjunction with limited field of view necessitate a visualization medium to provide patient-specific information at any given moment. Unfortunately, little research has been devoted to studying human factors associated with medical image displays and the need for a robust, intuitive visualization and interaction interfaces has remained largely unfulfilled to this day. Failure to engineer efficient medical solutions and design intuitive visualization interfaces is argued to be one of the major barriers to the meaningful transfer of innovative technology to the operating room. This thesis was, therefore, motivated by the need to study various cognitive and perceptual aspects of human factors in surgical image visualization systems, to increase the efficiency and effectiveness of medical interfaces, and ultimately to improve patient outcomes. To this end, we chose four different minimally-invasive interventions in the realm of surgical training, planning, training for planning, and navigation: The first chapter involves the use of stereoendoscopes to reduce morbidity in endoscopic third ventriculostomy. The results of this study suggest that, compared with conventional endoscopes, the detection of the basilar artery on the surface of the third ventricle can be facilitated with the use of stereoendoscopes, increasing the safety of targeting in third ventriculostomy procedures. In the second chapter, a contour enhancement technique is described to improve preoperative planning of arteriovenous malformation interventions. The proposed method, particularly when combined with stereopsis, is shown to increase the speed and accuracy of understanding the spatial relationship between vascular structures. In the third chapter, an augmented-reality system is proposed to facilitate the training of planning brain tumour resection. The results of our user study indicate that the proposed system improves subjects\u27 performance, particularly novices\u27, in formulating the optimal point of entry and surgical path independent of the sensorimotor tasks performed. In the last chapter, the role of fully-immersive simulation environments on the surgeons\u27 non-technical skills to perform vertebroplasty procedure is investigated. Our results suggest that while training surgeons may increase their technical skills, the introduction of crisis scenarios significantly disturbs the performance, emphasizing the need of realistic simulation environments as part of training curriculum

Doctor of Philosophy

dissertationGlobally, hepatocellular carcinoma (HCC) of the liver is diagnosed in over 700,000 people annually and trends indicate increasing prevalence. The majority of cases, >80%, are detected at advanced stages where systemic chemotherapies have little efficacy. The primary curative treatment is liver transplant, but if a donor liver is not available, only palliative care such as transarterial chemoembolization (TACE) is possible. TACE targets the tumor blood supply. An embolic containing a chemotherapeutic agent is injected into the tumor's vasculature via an endovascular catheter, subsequently shutting down blood flow while delivering localized chemotherapy. A presently approved product, Lipiodol, is an oily emulsion mixed with a chemotherapeutic used in conjunction with gelatin particles or synthetic polymer beads that act as emboli. Calibrated spherical drug eluting beads are now gaining favor for this procedure, replacing the multistep oil emulsion system. These beads, however, have shortcomings: aggregation of smaller diameter beads, fracturing of beads while under strain in the catheter, off target embolization particularly in pulmonary circulation, elution of only charged small molecule therapeutics, nondegradability, limited tumor depth penetration, and revascularization induced by a hypoxic state. To address these limitations, a genetically engineered silk-elastinlike protein polymer (SELP) system was developed to create a liquid-to-solid embolic agent capable of retaining and releasing a wider range of therapeutics, controlled degradation into nontoxic amino acids, and soluble until injected into the body where they transition irreversibly to a solid hydrogel network. This provides potential for ideal injectability as a low viscosity fluid at room temperature followed by optimal embolization by a highly stable hydrogel at body temperature. The proposed research involved engineering a SELP formulation with suitable viscosity for injection into the tumor vasculature via a microcatheter and a suitable gelation rate and gel strength for stable embolization. The drug release properties of the polymer matrix were determined for small molecule chemotherapeutics such as doxorubicin and anti-angiogenic sorafenib. Preliminary in vivo performance of the novel system for TACE was evaluated using a rodent model. Future directions include expansion of in vivo studies, particularly in an animal model for HCC and TACE to study therapeutic efficacy and longterm biocompatibility