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Title: Calculation method using Clarkson integration for the physical dose at the center of the spread-out Bragg peak in carbon-ion radiotherapy

Purpose: In broad-beam carbon-ion radiotherapy performed using the heavy-ion medical accelerator in Chiba, the number of monitor units is determined by measuring the physical dose at the center of the spread-out Bragg peak (SOBP) for the treatment beam. The total measurement time increases as the number of treatment beams increases, which hinders the treatment of an increased number of patients. Hence, Kusano et al.[Jpn. J. Med. Phys. 23(Suppl. 2), 65-68 (2003)] proposed a method to calculate the physical dose at the center of the SOBP for a treatment beam. Based on a recent study, the authors here propose a more accurate calculation method.Methods: The authors measured the physical dose at the center of the SOBP while varying the circular field size and range-shifter thickness. The authors obtained the physical dose at the center of the SOBP for an irregularly shaped beam using Clarkson integration based on these measurements.Results: The difference between the calculated and measured physical doses at the center of the SOBP varied with a change in the central angle of the sector segment. The differences between the calculated and measured physical doses at the center of the SOBP were within {+-}1% for all irregularly shaped beams that weremore » used to validate the calculation method.Conclusions: The accuracy of the proposed method depends on both the number of angular intervals used for Clarkson integration and the fineness of the basic data used for calculations: sampling numbers for the field size and thickness of the range shifter. If those parameters are properly chosen, the authors can obtain a calculated monitor unit number with high accuracy sufficient for clinical applications.« less
Authors:
; ; ; ; ;  [1] ; ;  [2]
  1. Department of Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)
  2. Department of Medical Physics, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)
Publication Date:
OSTI Identifier:
22121627
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 40; Journal Issue: 7; Other Information: (c) 2013 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; 61 RADIATION PROTECTION AND DOSIMETRY; 60 APPLIED LIFE SCIENCES; ACCELERATORS; ACCURACY; BEAMS; BRAGG CURVE; CALCULATION METHODS; CARBON IONS; DOSIMETRY; HEAVY IONS; MONITORS; PATIENTS; RADIATION DOSES; RADIOTHERAPY