Radiation Dosimetry
The optimal gamma passing rate thresholds of IMRT dosimetric verification in the treatment of esophageal cancer
Lidong Liu, Zhen Yang, Xiaoping Qiu, Yuqian Zhao, Mingjun Lei, Ying Cao, Xiaoyu Yang, Du Tang, Hanyu Wang, Yuhao Zuo
Published 2018-04-25
Cite as Chin J Radiol Med Prot, 2018, 38(4): 297-301. DOI: 10.3760/cma.j.issn.0254-5098.2018.04.010
Abstract
ObjectiveTo investigate the optimal gamma passing rate of intensity-modulated radiotherapy (IMRT) dosimetric verification in the treatment of esophageal cancer using a three-dimensional dose verification system EDose™.
MethodsTwenty five esophageal cancer patients treated by 7-field IMRT were retrospectively reviewed. Measured dose distribution were reconstructed on CT image and evaluated by gamma analysis and DVH metrics using the EDose™ system. Plans with DVH metrics dose difference<5% or with gamma passing > 90% under 3%/3 mm criteria were accepted. The optimal gamma passing rate for criteria of 5%/3 mm, 3%/3 mm, 2%/2 mm were investigated by drawing the receiver operating characteristic(ROC) curves and calculating the Youden Index. The sensitivity and specificity of the these optimal thresholds in the plan verification were also analyzed.
ResultsThe optimal thresholds for global gamma indices with 5%/3 mm, 3%/3 mm, 2%/2 mm were 98.66%, 94.84%, 78.56%, respectively. In the 90% common threshold, The sensitivity and specificity for common 90% threshold and optimal threshold under 3%/3 mm criteria were 0.17 vs. 0.85 and t 0.84 vs. 0.27, respectively. The sensitivity and specificity were 0.89, 0.65 and 0.23, 0.47 for optimal thresholds under 5%/3 mm and 2%/2 mm criteria, respectively.
ConclusionsThe sensitivity of optimal threshold gamma passing rate improved significantly compared with the common threshold (90%) at 3%/3 mm criteria., The sensitivity and the specificity were more balanced at the 2%/2 mm criteria compared with those at 3%/3 mm criteria.
Key words:
Intensity-modulated radiotherapy; Receiver operating characteristic curve; Optimal thresholds; Dose volume histogram
Contributor Information
Lidong Liu
College of Nuclear Science and Technology, University of South China, Hengyang 421001, China
Zhen Yang
Department of Oncology, Xiangya Hospital to Central South University, Changsha 410008, China
Xiaoping Qiu
College of Nuclear Science and Technology, University of South China, Hengyang 421001, China
Yuqian Zhao
College of Information Science and Engineering, Central South University, Changsha 410083, China
Mingjun Lei
Department of Oncology, Xiangya Hospital to Central South University, Changsha 410008, China
Ying Cao
Department of Oncology, Xiangya Hospital to Central South University, Changsha 410008, China
Xiaoyu Yang
Department of Oncology, Xiangya Hospital to Central South University, Changsha 410008, China
Du Tang
Department of Oncology, Xiangya Hospital to Central South University, Changsha 410008, China
Hanyu Wang
College of Nuclear Science and Technology, University of South China, Hengyang 421001, China
Yuhao Zuo
College of Nuclear Science and Technology, University of South China, Hengyang 421001, China (Present unit: Department of Oncology, Xiangya Hospital to Central South University)
