Dual-energy CT based proton range prediction in head and pelvic tumor patients. Issue 3 (December 2017)

• Record Type: Journal Article
• Authors: Wohlfahrt, Patrick; Möhler, Christian; Stützer, Kristin; Greilich, Steffen; Richter, Christian
• Is Part Of: Radiotherapy and oncology. Volume 125:Issue 3(2017:Dec.)
• Page Start: 526
• Page End: 533
• Publication Date: 2017-12
• Subjects: Dual-energy CT -- Range uncertainty -- Proton therapy; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2017.09.042
• Languages: English
• ISSNs: 0167-8140

Abstract

Abstract: Background and purpose: To reduce range uncertainty in particle therapy, an accurate computation of stopping-power ratios (SPRs) based on computed tomography (CT) is crucial. Here, we assess range differences between the state-of-the-art CT-number-to-SPR conversion using a generic Hounsfield look-up table (HLUT) and a direct patient-specific SPR prediction (RhoSigma) based on dual-energy CT (DECT) in 100 proton treatment fields. Material and methods: For 25 head-tumor and 25 prostate-cancer patients, the clinically applied treatment plan, optimized using a HLUT, was recalculated with RhoSigma as CT-number-to-SPR conversion. Depth–dose curves in beam direction were extracted for both dose distributions in a regular grid and range deviations were determined and correlated to SPR differences within the irradiated volume. Results: Absolute (relative) mean water-equivalent range shifts of 1.1 mm (1.2%) and 4.1 mm (1.7%) were observed in the head-tumor and prostate-cancer cohort, respectively. Due to the case dependency of a generic HLUT, range deviations within treatment fields strongly depend on the tissues traversed leading to a larger variation within one patient than between patients. Conclusions: The magnitude of patient-specific range deviations between HLUT and the more accurate DECT-based SPR prediction is clinically relevant. A clinical application of the latter seems feasible as demonstrated in this study using medically approved systems from CT acquisition to treatment planning.