A feasibility study of the application of structural similarity index to the assessment of radiotherapy plan quality
10.3760/cma.j.issn.0254-5098.2021.11.005
- VernacularTitle:基于结构相似性指数评估放疗计划质量的可行性研究
- Author:
Qingying WANG
1
;
Jiacheng LIU
;
Hanlin WANG
;
Kaining YAO
;
Jing YOU
;
Xiaofan LI
;
Ruoxi WANG
;
Chaoqiong MA
;
Hao WU
Author Information
1. 北京大学医学部医学技术研究院 100191
- Keywords:
Radiotherapy plan assessment;
Structural similarity;
Dose distribution
- From:
Chinese Journal of Radiological Medicine and Protection
2021;41(11):824-829
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To assess the three-dimensional dose distribution in radiotherapy plans using the structural similarity index(SSIM), compare the performance of SSIM with commonly used quality assessment indices, and develop a SSIM-based quality assessment method of multiple prescribed doses.Methods:The SSIM was introduced to providea quality score of various voxels by comparing actual and ideal three-dimensional dose data and combining the spatial location information of the voxels. Then the average value in a region of interest (ROI) was calculated as the quality score of the region. Fifty-three cases of cervical cancer were selected to analyze the correlation of the SSIM with the uniformity index (HI), conformity index (CI) of the dose distribution in various ROIs and to explore the capability of the SSIM to reflect the uniformity and conformity of dose distribution.Two types of quality defects were individually introduced into two of 53 radiotherapy plans. Then the two plans were compared with normal plans to characterize the response of the SSIM.Results:There was no correlation between HI and SSIM in positive lymph nodes(PGTVnd) due to the decrease in the HI sensitivity, while there was a significant negative correlation between them in regions where PGTVnd was removed from the planning target volume(PTV, R=-0.86, P<0.01). Meanwhile, there was a significant positive correlation between CI and SSIM in PGTVnd ( R=0.83, P<0.01). Therefore, the SSIM can be used to identify the artificial design defects in plans by determining abnormal dose gradients. Conclusions:Apart from reducing the defects of previous assessment parameters, the SSIM has the capability to assess the quality of radiotherapy plans by combining the uniformity and conformity of dose distribution and can provide accurate feedback on the spatial locations of quality defects.
