Weiwei Wang1, Zhijie Huang1, Yinxiangzi Sheng1, Jingfang Zhao2, Kambiz Shahnazi1, Qing Zhang3, Guoliang Jiang4. 1. Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, China. 2. Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, China; Department of Radiation Oncology, Fudan University Shanghai Cancer Center, China. 3. Department of Radiation Oncology, Shanghai Proton and Heavy Ion Center, Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, China. 4. Department of Radiation Oncology, Shanghai Proton and Heavy Ion Center, Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, China. Electronic address: guoliang.jiang@sphic.org.cn.
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.
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 PCApatients 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.
Authors: Edoardo Mastella; Silvia Molinelli; Giuseppe Magro; Stefania Russo; Maria Bonora; Sara Ronchi; Rossana Ingargiola; Alexandra D Jensen; Mario Ciocca; Barbara Vischioni; Ester Orlandi Journal: Front Oncol Date: 2021-12-13 Impact factor: 6.244