RBE-weighted dose conversions for carbon ionradiotherapy between microdosimetric kinetic model and local effect model for the targets and organs at risk in prostate carcinoma. (March 2020)

• Record Type: Journal Article
• Authors: Wang, Weiwei; Huang, Zhijie; Sheng, Yinxiangzi; Zhao, Jingfang; Shahnazi, Kambiz; Zhang, Qing; Jiang, Guoliang
• Is Part Of: Radiotherapy and oncology. Volume 144(2020)
• Page Start: 30
• Page End: 36
• Publication Date: 2020-03
• Subjects: Carbon ion radiotherapy -- Treatment planning -- RBE-weighted dose -- MKM -- LEM; 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.2019.10.005
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: A RBE-weighted dose conversion curve was established for targets and OARs. Matched with the conversion studies focusing on the targets when MKM dose >1.00 GyE. MKM doses in targets or outside targets could be converted to LEM doses. Abstract: Background and purpose: The aim of this study was to establish curves for the conversion of RBE-weighted doses for targets and organs at risk (OARs) from the microdosimetric kinetic model (MKM) calculation to that of the local effect model I (LEM) for carbon ion radiotherapy (CIRT) for prostate carcinoma (PCA). Materials and methods: This study was performed in the experimental treatment planning system (eTPS, V8A, Raystation, Sweden), which incorporates both MKM and LEM. CIRT plans from 10 PCA patients were collected. There were 5 steps to establish the curves: (1) design MKM plans in eTPS; (2) recalculate the physical doses from MKM to LEM and create a LEM plan in eTPS; (3) plot the RBE-weighted MKM to LEM conversion curves; (4) convert the MKM rectum constraint dose volume histogram (DVH) from NIRS to a LEM DVH; and (5) compare patients' rectum DVHs and follow-up with the converted constraint DVH. Results: The conversion factors for MKM doses of 0.18 Gy (RBE) to 4.55 Gy (RBE) per fraction to LEM doses were 2.72–1.06. For fraction sizes of >1 Gy (RBE), the conversion factors matched Fossati's curve and for fraction sizes of <1.00 Gy (RBE) the values were on the extrapolated Fossati's curve. A LEM rectum constraint DVH was established. Ten patients' rectum DVHs were all lower than LEM constraint DVHs. No complications were reported clinically. Conclusion: For PCA receiving CIRT, the RBE-weighted doses using MKM for targets and OARs could be converted to LEM doses using conversion curves.