Effect of the error of CT-electron density conversion curve on IMRT dose calculation(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2020年第7期
- Page:
- 816-821
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effect of the error of CT-electron density conversion curve on IMRT dose calculation
- Author(s):
- ZHU Fengying1; MA Yanning1; LUO Jinsheng1; PAN Hongwei1; WANG Yuanyuan3; LAN Maoying2
- 1. Department of Radiation Oncology, Shunde Hospital of Southern Medical University, Foshan 528300, China 2.Varian Medical Systems, Inc., Beijing 100176, China 3. Department of Radiation Oncology, Hefei Ion Medical Center, Hefei 230000, China
- Keywords:
- Keywords: CT-electron density conversion curve error intensity-modulated radiotherapy dose calculation
- PACS:
- R312；R811.1
- DOI:
- DOI:10.3969/j.issn.1005-202X.2020.07.004
- Abstract:
-
Abstract: Objective To investigate the effect of the error of CT-electron density conversion curve on the calculation of dose distribution of intensity-modulated radiotherapy (IMRT) plan. Methods Ten patients undergoing IMRT for cervical cancer in Shunde Hospital of Southern Medical University were enrolled. Different CT-electron density conversion curve errors (±0.5%, ±1.0%, ±1.5%, ±2.0% and ±3.0%) were introduced into IMRT plans in Eclipse treatment planning system for recalculating dose distribution and obtaining 10 new plans for every patient which were then compared with the original plan without conversion curve errors. The effect of conversion curve errors on the dose calculation was discussed by analyzing the related dosimetric parameters, conformity index, homogeneity index of target areas, and the volume-dose parameters of organs-at-risk such as spinal cord, kidney, small intestine, bladder, rectum and so on. The relationships between different conversion curve errors and the deviation value of each dosimetric parameter were analyzed. Results The dosimetric parameters were decreased when positive errors were introduced into IMRT plan while increased when negative errors were introduced. The greater the conversion curve error was, the greater the effects on dosimetric parameters were. When the conversion curve error was 1.5%, the average target coverage was 94.73%+1.86% and the dosimetric effect coming from larger conversion curve errors (higher than 1.5%) was out of the acceptable range in clinic. No statistical difference was found among plans with different conversion curve errors in conformity index and homogeneity index (P>0.05). There were significant negative correlations between conversion curve errors and the deviation values of different dosimetric parameters (all P<0.001), and the corresponding correlation formulas were obtained by Matlab software. Conclusion With conversion curve error higher than 1.5%, the dosimetric deviation is out of the acceptable range and the dose distribution cannot meet the clinical requirements. An accurate CT-electron density conversion curve should be created when building treatment model by planning system, and the quality assurance of CT-sim should be performed regularly, thereby ensuring the accurate calculation of dose calculation of treatment plan.
Last Update: 2020-07-28