Average vector method for determining isocenter of rotated radiotherapy equipment
ZHANG Xiang, FAN Wengang, SHI Shaohua, YE Peiqing, ZHANG Hui
Beijing Key Laboratory of Precision/Ultra-Precision Manufacturing Equipments and Control, State Key Laboratory of Tribology, Institute of Manufacture Engineering, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
Abstract：The isocentric accuracy of rotated radiotherapy equipment significantly influences the treatment accuracy. The average vector method is used to find the optimal isocenter considering the mechanical deformation of the rotated radiotherapy equipment. The maximum distance between the isocenter which is treated as the optimization variable and the ray vectors is considered as a constraint. An objective function is then designed to calculate the average distance between the isocenter that meets the constraint and the ray vectors. Finally, the location of the optimal isocenter and the isocentric envelop are obtained. A test with this method gives the radius of the isocentric envelop as 0.311 mm which is equal to that given by the vector-end-effector method, and about 15.5% less than that given by the point-end-effector method. The results also show that the average distance between the optimal isocenter and the ray vectors is 0.206 mm, about 11.2% less than that by the vector-end-effector method and 28% less than that by the point-end-effector method.
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ZHANG Xiang, FAN Wengang, SHI Shaohua, YE Peiqing, ZHANG Hui. Average vector method for determining isocenter of rotated radiotherapy equipment. Journal of Tsinghua University(Science and Technology), 2015, 55(7): 744-749.
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