Isocenter characteristics of an external ring proton gantry
- Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, CA (United States)
Purpose: Determine the shape, size, geometric center, and virtual center of the isocenter for a proton gantry and compare to electron/X-ray accelerator gantries. Methods and materials: The majority of commercial electron/X-ray accelerator gantries consist of a rotating treatment head mounted to a stationary stand through a slewing ring bearing. The world's first proton gantry uses two rotating external rings, to which is mounted a fixed treatment nozzle with a movable snout that extends close to the center of rotation. The radial aspect of the isocenter for two similar proton gantries and two different electron/X-ray gantries were measured in the gantry frame of reference with a front pointer and a theodolite. These results were then transformed into room coordinates. The axial aspect of the isocenter was measured with a dial indicator. Results: The radial aspect of the isocenter for slewing ring gantries has the shape of two concentric circles. The radial aspect of the isocenter for external ring gantries is shaped like a butterfly. The size of the mechanical isocenter is independent of the gantry style. Conclusions: The locations of the geometric and virtual centers can be determined to within 0.2 mm. Multiple gantry angle treatments can be delivered with a single setup allowing 2 mm for gantry and nozzle deflections. Precision treatments can be delivered allowing only 0.5 mm if the measured isocenter path is applied.
- OSTI ID:
- 20630993
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 60, Issue 5; Other Information: DOI: 10.1016/j.ijrobp.2004.08.052; PII: S0360-3016(04)02545-3; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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