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KMID : 0384620060170040212
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Korean Journal of Medical Physics
2006 Volume.17 No. 4 p.212 ~ p.223
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Development of Quality Assurance Program for the On-board Imager Isocenter Accuracy with Gantry Rotation
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Cheong Kwang-Ho
Jo Byung-Chul
Kang Sei-Kwon
Kim Kyoung-Joo
Bae Hoon-Sik
Suh Tae-Suk
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Abstract
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Positional accuracy of the on-board imager (OBI) isocenter with gantry rotation was presented in this paper. Three different type of automatic evaluation methods of discrepancies between therapeutic and OBI isocenter using digital image processing techniques as well as a procedure stated in the customer acceptance procedure (CAP) were applied to check OBI isocenter migration trends. Two kinds of kV x-ray image set obtained at OBI source angle of and every and raw projection data for cone-beam CT reconstruction were used for each evaluation method. Efficiencies of the methods were also estimated. If a user needs to obtain an isocenter variation map with full gantry rotation, a method taking OBI image for every and fitting with 5th order polynomial was appropriate. However for a mere quality assurance (QA) purpose of OBI isocenter accuracy, it was adequate to use only four OBI Images taken at the OBI source angle of . Maximal discrepancy was 0.44 mm which was observed between the OBI source angle of OBI isocenter accuracy was maintained below 0.5 mm for a year. Proposed QA program may be helpful to Implement a reasonable routine QA of the OBI isocenter accuracy without great efforts.
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KEYWORD
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On-board Imager (OBI), Isocenter, Linac, Gantry rotation
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