A primary research of intensity-modulated dose verification based on anatomic structure of three-dimensional images

Abstract

Objective To verify IMRT plans in point,planar and 3D dose,and to concretely analyze the dose differences of 3D anatomic structure based on Gamma passing rate.Methods Thimble ion-chamber,Matrixx and ArcCheck were separately used to measure six nasopharyngeal carcinoma treatment plans and six lung cancer treatment plans.The dose measurement deviation of the center point was compared as well as the Gamma passing rate of dose verification under the criteria of both 3％/3 mm and 2％/2 mm,the group t-test and one-way ANOVA were also proceeded.3DVH system was used to analyze the dose measurement deviation of target volume (TV) and organ at risk (OAR) through DVH.Results For IMRT and VMAT treatment plans,the mean deviation of point dose was (0.59 ± 1.31) ％ and (-1.00 ± 1.03)％ respectively,and the maximum deviation was less than 3％.Under the criterion of 3％/3 mm,the Gamma passing rate measured by Matrixx,ArcCheck and 3DVH for IMRT plans was 96.28％,97.55％ and 99.02％ respectively,and for VMAT plans,the corresponding results of three different detectors were 97.24％,99.67％ and 98.48％.The results analyzed and compared by 3DVH showed that even under the condition of high Gamma pass rate (more than 95％ for a Gamma criterion of 3％/3 mm),the DVH metrics of both TV and OAR in two cases (account for 16.7％ of the total plan) were significantly different on the clinical parameters,including GTV,spinal cord and brain stem etc.Conclusions The analysis of dose difference of the measurement results based on Gamma pass rate and on anatomic structure of 3D images can more effectively evaluate the influence of dose error to the implementing of clinical plan and the impact to the clinical treatment. Key words: Anatomic structure of three-dimensional images; Dose verification; γ passing rate