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동일 기종 선형가속기간 8 MV 광자선에 대한 빔 매칭 정확도 평가

Evaluation of Beam-Matching Accuracy for 8 MV Photon Beam between the Same Model Linear Accelerator

방사선기술과학 2020년 43권 2호 p.105 ~ 114
김연래 ( Kim Yon-Lae ) - Choonhae College of Health Sciences Department of Radiologic Technology

정진범 ( Chung Jin-Beom ) - Seoul National University Bundang Hospital Department of Radiation Oncology
강성희 ( Kang Seong-Hee ) - Seoul National University Bundang Hospital Department of Radiation Oncology

Abstract


This study aimed to assess of beam-matching accuracy for an 8 MV beam between the same model linear accelerators(Linac) commissioned over two years. Two models were got the customer acceptance procedure(CAP) criteria. For commissioning data for beam-matched linacs, the percentage depth doses(PDDs), beam profiles, output factors, multi-leaf collimator(MLC) leaf transmission factors, and the dosimetric leaf gap(DLG) were compared. In addition, the accuracy of beam matching was verified at phantom and patient levels. At phantom level, the point doses specified in TG-53 and TG-119 were compared to evaluate the accuracy of beam modelling. At patient level, the dose volume histogram(DVH) parameters and the delivery accuracy are evaluated on volumetric modulated arc therapy(VMAT) plan for 40 patients that included 20 lung and 20 brain cases. Ionization depth curve and dose profiles obtained in CAP showed a good level for beam matching between both Linacs. The variations in commissioning beam data, such as PDDs, beam profiles, output factors, TF, and DLG were all less than 1%. For the treatment plans of brain tumor and lung cancer, the average and maximum differences in evaluated DVH parameters for the planning target volume(PTV) and the organs at risk(OARs) were within 0.30% and 1.30%. Furthermore, all gamma passing rates for both beam-matched Linacs were higher than 98% for the 2%/2 mm criteria and 99% for the 2%/3 mm criteria. The overall variations in the beam data, as well as tests at phantom and patient levels remains all within the tolerance (1% difference) of clinical acceptability between beam-matched Linacs. Thus, we found an excellent dosimetric agreement to 8 MV beam characteristics for the same model Linacs.

키워드

심부선량백분율 ; 선량분포 ; 사용준비 ; 선량체적히스토그람 ; 전달 정확성
Percentage depth dose ; Dose profile ; Commissioning ; Dose volume histogram ; Delivery accuracy
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