The effect of bulk electron density on the dose accuracy of treatment planning for postoperative cervical cancer
10.3760/cma.j.issn.0254-5098.2021.02.011
- VernacularTitle:体电子密度对术后宫颈癌放射治疗计划剂量精确度的影响研究
- Author:
Sheng HAN
;
Xiaodong PENG
;
Ke YUAN
;
Rutie YIN
;
Xiongfei LIAO
;
Xianliang WANG
;
Lei ZHANG
;
Min LIU
;
Bin BI
;
Yazheng CHEN
- From:
Chinese Journal of Radiological Medicine and Protection
2021;41(2):140-145
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To study the impact on dose accuracy for the treatment planning by manually assigning accurate electron density for CT image-based tumor tissues and organs at risk.Methods:Twenty cases of retrospective postoperative cervical cancer radiotherapy plans were selected. The body electron density of the corresponding organs was derived from the ICRU 46 report and assigned in the treatment planning system (Monaco5.11, Sweden), including the bladder, rectum, intestine, kidney, spinal cord, femoral head, and ilium. The original plans were double-arc volumetric modulated arc therapy plan (360° VMAT), using Monte Carlo algorithm, the calculation grid was 0.3 cm × 0.3 cm × 0.3 cm, and the minimum subfield width was 0.6 cm. Keep the original plan fluence unchanged and recalculate the dose to generate a new plan. The two-dimensional dose distribution and dose-volume histogram (DVH) were used to compare the differences between the two plans. The difference was compared between the two group plans by using the dosimetry parameters and DVH two dimension curve.Results:For the planning of assigning bulk electron density (Plan RED), the deviation of the patient′s target dose parameters and the original plan (Plan ref) was <2%, and the average deviation of all target regions D2, D98, Dmean was < 0.7%, only 2 of the 180 data were between 2% and 3%. The average deviation of V20, V30, D1 cm 3, Dmean of the bladder, rectum, and small intestine, the original Plan ref was less than 0.6%, and 4 out of 240 data had values > 2%. Plan RED′s average hop count was 0.9% higher than Plan ref, and the total number of subfields remains unchanged. The planned dose generated by manually assigning the electron density in Plan RED was higher than that in Plan ref, but met the clinical requirements. The two-dimensional curves of the DVH diagram for targets and OARs almost completely overlapped, and there was no obvious difference in the dose distribution diagram of the same cross section. The statistical result of all parameters showed that the difference in planned dose parameters between the two groups was not statistically significant( P>0.05). Conclusions:The overall deviation of dose accuracy between Plan RED and Plan ref is <2%, which meets the clinical requirements and provides a reference for realizing MRI-only treatment planning.
