Premium
Field‐size dependence of doses of therapeutic carbon beams
Author(s) -
Kusano Yohsuke,
Kanai Tatsuaki,
Yonai Shunsuke,
Komori Masataka,
Ikeda Noritoshi,
Tachikawa Yuji,
Ito Atsushi,
Uchida Hirohisa
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2779126
Subject(s) - sobp , imaging phantom , percentage depth dose curve , beam (structure) , bragg peak , dosimetry , field size , scattering , dose profile , materials science , optics , physics , nuclear medicine , ionization chamber , medicine , ion , quantum mechanics , ionization
To estimate the physical dose at the center of spread‐out Bragg peaks (SOBP) for various conditions of the irradiation system, a semiempirical approach was applied. The dose at the center of the SOBP depends on the field size because of large‐angle scattering particles in the water phantom. For a small field of 5 × 5cm 2 , the dose was reduced to 99.2%, 97.5%, and 96.5% of the dose used for the open field in the case of 290, 350, and 400 MeV ∕ n carbon beams, respectively. Based on the three‐Gaussian form of the lateral dose distributions of the carbon pencil beam, which has previously been shown to be effective for describing scattered carbon beams, we reconstructed the dose distributions of the SOBP beam. The reconstructed lateral dose distribution reproduced the measured lateral dose distributions very well. The field‐size dependencies calculated using the reconstructed lateral dose distribution of the therapeutic carbon beam agreed with the measured dose dependency very well. The reconstructed beam was also used for irregularly shaped fields. The resultant dose distribution agreed with the measured dose distribution. The reconstructed beams were found to be applicable to the treatment‐planning system.