Program Information
Comprehensive Analysis of Proton Range Uncertainties Related to Stopping-Power-Ratio Estimation Using Dual-Energy CT Imaging
B Li1,2* , X Duan1 , C Shen1 , X Jia1 , M Yang1, (1) University of Texas Southwestern Medical Center, Dallas, TX, USA (2) Southern Medical University, Guangzhou, Guangdong, China
Presentations
SU-K-108-5 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 108
Purpose: The dual-energy CT-based (DECT) approach is promising in reducing the overall uncertainty in proton stopping-power-ratio (SPR) estimation compared to the conventional stoichiometric calibration approach. The objective of this study is to analyze the uncertainty contributing factors in the SPR estimation using the DECT-based approach and derive a comprehensive estimate of the range uncertainty associated with the SPR estimation in treatment planning.
Methods: Two state-of-the-art DECT-based methods were selected and implemented on a Siemens SOMATOM Force DECT scanner. The uncertainties in the DECT calculation of SPR were divided into three major independent categories: 1) the DECT imaging uncertainty, 2) the DECT modeling uncertainty, and 3) the DECT inherent uncertainty. In DECT imaging uncertainty study, we considered three major factors: patient size, location in the scan, and random HU variation scanned at different times. DECT modeling uncertainty was estimated based on the Gammex tissue equivalent material inserts used in the calibration process. DECT inherent uncertainty was estimated by comparing the variation between theoretical calculation and DECT-based estimation for various human tissues. Two additional DECT irrelevant uncertainties were also considered. One single composite uncertainty estimate was eventually determined for three tumor sites (lung, prostate and head-and-neck).
Results: The uncertainties associated with the two selected DECT methods were found to be similar. Total SPR prediction uncertainties (1σ) were 3.8%, 1.2%, and 2.0% for lung, soft tissues, and bone tissues, respectively. The dominant uncertainty contributing factor in the DECT approach was the DECT imaging uncertainties. For three different treatment sites, the range uncertainty (2σ) determined by the DECT-based approach was about 2.2%, compared to that of 3.5% by conventional stoichiometric calibration method.
Conclusion: We performed a comprehensive study on SPR estimation uncertainties using the DECT-based approach. Our study showed that the DECT-based approach can reduce uncertainty down to 2.2% in clinical scenarios.
Funding Support, Disclosures, and Conflict of Interest: This work was in part supported by the Cancer Prevention and Research Institute of Texas grant (RP160661), National Natural Science Foundation of China (No. 81571771), and Ministry of Science and Technology of China (No. 2015BAI01B10).
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