Intuitive navigation in the targeting of radiation therapy treatment beams

This research focused on the possible benefits to be gained from using the intuitive navigation made possible by head-mounted displays (HMDs) in the targeting of radiation therapy treatment beams. A tumor surrounded by various types of healthy tissue can present a very complex 3-D situation which must be thoroughly understood for effective treatment to be possible. Conventional 2-D treatment planning suffers from reliance on 2-D diagnostic imaging and dose computations to represent an inherently 3-D problem. Current state-of-the-art treatment planning systems use 3-D models of the patient and compute 3-D dose distributions, but complete exploration of the solution space of possible beam orientations can be hindered by not-so-intuitive navigation controls. The thesis of this dissertation was that the head-mounted display will permit freer exploration of the patient anatomy and range of possible beam orientations, thereby resulting in more efficient treatment planning.; To that end, I developed a new, intuitive navigation mode, which used the orientation of a HMD to determine the direction from which its wearer viewed a 3-D model of the patient's anatomy. When the user looked down, he viewed the anatomy from above. Looking up yielded a view from below, and turning his head horizontally in a circle completely scanned around the model. Although it did not have a real-world metaphor, this mode (dubbed Orbital mode) proved to be surprisingly easy to use and well-suited to the task of targeting treatment beams. I compared Orbital mode with more conventional joystick-based rotation in a user study in which radiation oncology professionals designed treatment beam configurations for lung tumor cases. Slightly faster performance was found with Orbital mode, although there appeared to be no significant difference in the quality of the beam configurations. Movement in Orbital mode was more omnidirectional than with the joystick, most likely due to the mechanical construction of the joystick, which preferentially encouraged left-right and forward-back deflection. The overall conclusion from this study was that HMDs in their present state are not appropriate for clinical use, but with future developments in HMD technology, the benefits of intuitive navigation may appear in mainstream radiation treatment planning.