Estimation of linear energy transfer distribution for broad-beam carbon-ion radiotherapy at the National Institute of Radiological Sciences, Japan
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A treatment of carbon-ion radiotherapy (CIRT) is generally evaluated using the dose weighted by relative biological effectiveness (RBE) while ignoring the radiation quality varying in the patient. In this study, we have developed a method of estimating linear energy transfer (LET) from the RBE in an archived treatment plan to represent the radiation quality of the treatment. The LET in a beam database was associated with the RBE by two fitting functions per energy, one for the spread-out Bragg peak (SOBP) and the other for shallower depths, to be differentiated by RBE per energy per modulation. The estimated LET was generally consistent with the original calculation within a few keV/μm, except for the overkill region near the distal end of SOBP. The knowledge of experimental radiobiology can thereby be associated with CIRT treatments through LET, which will potentially contribute to deeper understanding of clinical radiobiology and further optimization of CIRT.
KeywordsRelative biological effectiveness Linear energy transfer Carbon-ion radiotherapy Treatment planning Retrospective analysis
The authors are deeply indebted to all the researchers, medical staff, and technical staff of NIRS who prepared, performed, or supported the extensive clinical studies on carbon-ion radiotherapy over many years.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
No ethical approval was required for this article, because it does not contain any studies performed with human subjects or animals.
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