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Original Article

Korean Journal of Medical Physics 2010; 21(4): 340-347

Published online December 25, 2010

Copyright © Korean Society of Medical Physics.

A Method to Calculate a Pass Rate of the Ճ-index Analysis in Tomotherapy Delivery Quality Assurance (DQA)

단층치료기를 이용한 방사선 치료의 환자별 정도관리 평가를 위한 감마인덱스의 정량화 방법

Dahl Park*, Yong Ho Kim*, Won Taek Kim, Dong Won Kim, Dong Hyun Kim*, Hosang Jeon§, Ji Ho Nam§, Sangwook Lim

박달*ㆍ김용호*ㆍ김원택ㆍ김동원ㆍ김동현*ㆍ전호상§ㆍ남지호§ㆍ임상욱

*Department of Radiation Oncology, Medical Research Institute, Pusan National University Hospital, Busan, Department of Radiation Oncology, Pusan National University School of Medicine, Yangsan, §Pusan National University Yangsan Hospital, Kosin University College of Medicine, Busan, Korea

*부산대학교병원 방사선종양학과, 부산대학교병원 의학연구소, 부산대학교 의학전문대학원 방사선종양학교실, §부산대학교양산병원 방사선종양학과, 고신대학교 의과대학 방사선종양학교실

Abstract

DQA, a patient specific quality assurance in tomotherapy, is usually performed using an ion chamber and a film. The result of DQA is analysed with the treatment planning system called Tomo Planning Station (TomoPS). The two-dimensional dose distribution of film measurement is compared with the dose distribution calculated by TomoPS using the Ճ-index analysis. In Ճ-index analysis, the criteria such as 3%/3 mm is used and we verify that whether the rate of number of points which pass the criteria (pass rate) is within tolerance. TomoPS does not provide any quantitative information regarding the pass rate. In this work, a method to get the pass rate of the Ճ-index analysis was suggested and a software PassRT which calculates the pass rate was developed. The results of patient specific QA of the intensity modulated radiation therapy measured with I'mRT MatriXX (IBA Dosimetry, Germany) and DQA of tomotherapy measured with film were used to verify the proposed method. The pass rate was calculated using PassRT and compared with the pass rate calculated by OmniPro I'mRT (IBA Dosimetry, Germany). The average difference between the two pass rates was 0.00% for the MatriXX measurement. The standard deviation and the maximum difference were 0.02% and 0.02%, respectively. For the film measurement, average difference, standard deviation and maximum difference were 0.00%, 0.02% and 0.02%, respectively. For regions of interest smaller than 24.3×16.6 cm2 the proposed method can be used to calculate the pass rate of the gamma index analysis to one decimal place and will be helpful for the more accurate DQA in tomotherapy.

KeywordsTomoTherapy, Patient specific quality assurance, Ճ-index

Korean Society of Medical Physics

Vol.35 No.2
June 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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