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Practical Implementation of Patient-Specific Quality Assurance for Small and Multiple Brain Tumors in CyberKnife with Fixed Collimators

 Eungman Lee  ;  Kwangwoo Park  ;  Jin Sung Kim  ;  Yong Bae Kim  ;  Ho Lee 
 Korean Journal of Medical Physics (의학물리), Vol.29(2) : 53-58, 2018 
Journal Title
 Korean Journal of Medical Physics (의학물리) 
Issue Date
CyberKnife ; Microchamber ; EBT3 ; Patient-specific quality assurance ; Brain tumor
This paper evaluates patient-specific quality assurance (PSQA) in the treatment of small and multiple tumors by the CyberKnife system with fixed collimators, using an ion chamber and EBT3 films. We selected 49 patients with single or multiple brain tumors, and the treatment plans include one to four targets with total volumes ranging from 0.12 cc to 3.74 cc. All PSQA deliveries were performed with a stereotactic dose verification phantom. The A16 microchamber (Standard Imaging, WI, USA) and Gafchromic EBT3 film (Ashland ISP Advanced Materials, NJ, USA) were inserted into the phantom to measure the point dose of the target and the dose distribution, respectively. The film was scanned 1 hr after irradiation by a film digitizer scanner and analyzed using RIT software (Radiological Imaging Technology, CO, USA). The acceptance criteria was <5% for the point dose measurement and >90% gamma passing rate using 3%/3 mm and relative dose difference, respectively. The point dose errors between the calculated and measured dose by the ion chamber were in the range of −17.5% to 8.03%. The mean point dose differences for 5 mm, 7.5 mm, and 10 mm fixed cone size was −11.1%, −4.1%, and −1.5%, respectively. The mean gamma passing rates for all cases was 96.1%. Although the maximum dose distribution of multiple targets was not shown in the film, gamma distribution showed that dose verification for multiple tumors can be performed. The use of the microchamber and EBT3 film made it possible to verify the dosimetric and mechanical accuracy of small and multiple targets. In particular, the correction factors should be applied to small fixed collimators less than 10 mm.
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1. College of Medicine (의과대학) > Dept. of Radiation Oncology (방사선종양학교실) > 1. Journal Papers
Yonsei Authors
Kim, Yong Bae(김용배) ORCID logo https://orcid.org/0000-0001-7573-6862
Kim, Jinsung(김진성) ORCID logo https://orcid.org/0000-0003-1415-6471
Park, Kwang Woo(박광우) ORCID logo https://orcid.org/0000-0002-9843-7985
Lee, Eung Man(이응만)
Lee, Ho(이호) ORCID logo https://orcid.org/0000-0001-5773-6893
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