End-to-end testing of the Leksell Gamma Knife Icon system
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The Leksell Gamma Knife Icon is a stereotactic radiosurgery system that is used to non-invasively treat brain lesions. It incorporates 192 fixed cobalt-60 sources, which ensures the highest degree of accuracy during treatment due to the minimization of potential error from stationary sources. The gamma knife’s precision and special modifications for conformity to the human brain ensure faster treatments and fractionated options, delivered in a few hours on a single day, as opposed to treatment on consecutive days. A titanium-alloy frame affixed to the skull of a patient before each treatment has defined the stereotactic coordinate system of previous gamma knife models, as well as provided complete patient immobilization during treatment. However, the newest gamma knife model from Elekta, the Icon, introduced a frameless treatment option that utilizes an on-board cone-beam computed tomography (CBCT) imager for patient positioning and a motion tracking system to monitor patient movement during treatment. When using this option, the stereotactic coordinate system is defined by the CT image taken before treatment, and a thermoplastic mask is used for moderate patient immobilization, as opposed to the titanium-alloy frame. Since the opportunities for positioning misalignment and out-of-tolerance patient movement is now introduced to the treatment, thorough research and end-to-end testing was conducted to make sure that correction calculations and monitoring methods are being performed to keep these concerns to a minimum and provide an accurate and precise radiosurgery procedure. This project was conducted to consider extreme patient movement during radiosurgery procedures and provide additional end-to-end testing on the Leksell Gamma Knife system at Emory Saint Joseph’s Hospital in Atlanta, Georgia. The performed testing verified the integrated imaging system by treating a moving target that required position shifts between treatments to mimic patient misalignments, observing the ability of the system to accurately correct patient shifts during setup. Additionally, this work evaluated the motion tracking system by treating a moving target, which mimicked patient chin-like movements during treatment, monitoring the tolerance at which there was a clinical detriment to the quality of the plan due to patient motion.