基于三维影像解剖结构的调强剂量验证的初步研究

目的 对调强治疗计划进行点、平面和三维剂量验证,在γ通过率基础上具体分析三维解剖结构的剂量误差。方法 分别用指形电离室、Matrixx和ArcCheck测量鼻咽癌和肺癌调强治疗计划各 6例,分别比较IMRT和VMAT治疗计划中心点测量剂量偏差,并行成组t检验。比较IMRT和VMAT治疗计划在3%/3 mm、2%/2 mm标准下剂量验证的γ通过率,并行单因素方差分析。使用3DVH来分析患者靶区和OAR的测量剂量偏差。结果 IMRT和VMAT治疗计划中心点剂量平均偏差分别为(0.59±1.31)%和(－1.00±1.03)%,最大偏差均<3%。在3%/3 mm标准下,IMRT计划Matrixx、ArcCheck和3DVH的γ通过率分别为96.28%、97.55%和99.02%,VMAT计划的分别为97.24%、99.67%和98.48%。3DVH系统比较结果表明γ通过率较高情况下(3%/3 mm标准>95%),有 2例治疗计划(占总计划16.7%)测量结果中的靶区和OAR的DVH存在明显偏差,包括GTV、脊髓和脑干等在临床指标下的差异。结论 通过γ分析基于三维影像解剖结构来分析测量结果能更有效评估剂量误差对临床计划执行的影响和对临床治疗的损害。

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

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㎜ and 2%/2㎜,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㎜, 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.