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Normal tissue exposure and second malignancy risk in vertebral-body-sparing craniospinal irradiation. Med Dosim 2022; 47:142-145. [PMID: 34996678 DOI: 10.1016/j.meddos.2021.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 11/22/2021] [Accepted: 12/01/2021] [Indexed: 11/20/2022]
Abstract
The purpose of this study was to compare dose to anterior organs at risk (OARs) and quantify the risk of developing secondary malignancy (SMN) in pediatric patients treated with vertebral-body-sparing (VBS) vs vertebral body (VB) pencil beam scanning proton craniospinal irradiation (CSI). Comparative plans of VBS and VB CSI were created for 10 previously treated patients. Dose-volume histograms were used to evaluate dose to OARs. Absolute excess risk of SMN was calculated according to the organ-specific, radiation-induced cancer incidence based on the organ equivalent dose. OAR dosimetric parameters and absolute excess risk of SMN were compared for VBS and VB plans using the Kruskal-Wallis H test (α = 0.05). VBS CSI leads to significantly lower radiation dose to the heart, esophagus, kidney, liver and bowel. Excluding the vertebral body also significantly decreases the absolute excess risk of SMN for liver, esophagus and bowel. For these reasons, implementation of VBS pencil beam scanning proton CSI should be considered.
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Clausen M, Khachonkham S, Gruber S, Kuess P, Seemann R, Knäusl B, Mara E, Palmans H, Dörr W, Georg D. Phantom design and dosimetric characterization for multiple simultaneous cell irradiations with active pencil beam scanning. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2019; 58:563-573. [PMID: 31541343 PMCID: PMC6768893 DOI: 10.1007/s00411-019-00813-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 09/09/2019] [Indexed: 05/04/2023]
Abstract
A new phantom was designed for in vitro studies on cell lines in horizontal particle beams. The phantom enables simultaneous irradiation at multiple positions along the beam path. The main purpose of this study was the detailed dosimetric characterization of the phantom which consists of various heterogeneous structures. The dosimetric measurements described here were performed under non-reference conditions. The experiment involved a CT scan of the phantom, dose calculations performed with the treatment planning system (TPS) RayStation employing both the Pencil Beam (PB) and Monte Carlo (MC) algorithms, and proton beam delivery. Two treatment plans reflecting the typical target location for head and neck cancer and prostate cancer treatment were created. Absorbed dose to water and dose homogeneity were experimentally assessed within the phantom along the Bragg curve with ionization chambers (ICs) and EBT3 films. LETd distributions were obtained from the TPS. Measured depth dose distributions were in good agreement with the Monte Carlo-based TPS data. Absorbed dose calculated with the PB algorithm was 4% higher than the absorbed dose measured with ICs at the deepest measurement point along the spread-out Bragg peak. Results of experiments using melanoma (SKMel) cell line are also presented. The study suggested a pronounced correlation between the relative biological effectiveness (RBE) and LETd, where higher LETd leads to elevated cell death and cell inactivation. Obtained RBE values ranged from 1.4 to 1.8 at the survival level of 10% (RBE10). It is concluded that dosimetric characterization of a phantom before its use for RBE experiments is essential, since a high dosimetric accuracy contributes to reliable RBE data and allows for a clearer differentiation between physical and biological uncertainties.
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Affiliation(s)
- Monika Clausen
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria.
| | - Suphalak Khachonkham
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Division of Radiation Therapy, Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Sylvia Gruber
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Peter Kuess
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- EBG MedAustron GmbH, Wiener Neustadt, Austria
| | | | - Barbara Knäusl
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- EBG MedAustron GmbH, Wiener Neustadt, Austria
| | - Elisabeth Mara
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- University of Applied Science, Wiener Neustadt, Austria
| | - Hugo Palmans
- EBG MedAustron GmbH, Wiener Neustadt, Austria
- National Physical Laboratory, Teddington, UK
| | - Wolfgang Dörr
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- EBG MedAustron GmbH, Wiener Neustadt, Austria
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