形变配准在宫颈癌近距离放疗分次间剂量评估中的可行性研究

目的:比较近距离放疗分次间靶区和正常组织在形变配准(DIR)和简单累加剂量体积直方图(DVH)情况下，累积剂量的剂量学差异，分析在宫颈癌三维近距离放疗计划中，形变配准技术应用于靶区和正常组织剂量评估的可行性。方法:回顾性选取13例宫颈癌近距离放疗病例，每个病例均进行了4次CT定位的近距离放疗。对每个病例的4次CT进行形...

Feasibility of application of deformable image registration to the dosimetry assessment of fractionated brachytherapy for cervical cancer

Objective To study the differences in the cumulative dose between deformable image registration (DIR) and simple dose-volume histogram (DVH) summation in the fractionated brachytherapy of cervical cancer, and to analyze the feasibility of the application of DIR in the dosimetry assessment of targets and organs-at-risk (OARs) in the brachytherapy. Methods A retrospective analysis was conducted for 13 cases with primary cervical cancer treated with four fractions of interstitial brachytherapy guided by CT images. The four CT images of each cases were registered using an intensity-based DIR. Then, the cumulative doses (the D_{2 cm}³, D_{1 cm}³, and D_{0.1 cm}³ of the bladder, rectum, intestine, and colon and the D₉₀for targets) after DIR were calculated and compared to those obtained using simple DVH summation. Afterward, the correlation between the dose difference and dice similarity coefficient (DSC) was analyzed. With the dose difference (the remaining dose of OARs caused by the DIR) as limits, a new plan was made for the latest CT to calculate the dose increase to targets. Results Compared to simple DVH summation, DIR allowed the cumulative doses of the D_{2 cm}³ and D_{1 cm}³ of bladder to be decreased by (2.47±1.92) and (2.82±2.73) Gy, respectively on average (t=-3.65, -2.93, P<0.05), those of the D_{2 cm}³, D_{1 cm}³, and D_{0.1 cm}³ of rectum to be decreased by (2.05±1.61) Gy, (1.51±1.58), and (3.21±2.50) Gy, respectively on average (t=-4.02, -3.02, -4.06, P<0.05), and those of the D_{2 cm}³, D_{1 cm}³, and D_{0.1 cm}³ to be decreased by (1.42±0.99), (1.55±1.28) Gy, and (2.43±1.95) Gy, respectively on average (t=-3.52, -2.96, -3.06, P<0.05). There was no significant statistical difference in the D₉₀ of targets, the D_{0.1 cm}³ of the bladder, and the D_{2 cm}³, D_{1 cm}³, D_{0.1 cm}³ of the colon (P>0.05) between both methods, and there was no distinct correlation between DSC and dose difference (P>0.05). The DIR increased the dose to targets, with a median value of 150 cGy. However, the accuracy of the DIR should be improved. In clinical practice of multiple fractions of brachytherapy for cervical cancer, it''s still recommended to adopt the simple dose summation method to assess the doses to targets and OARs.