Radiological Physics and Technology

, Volume 11, Issue 2, pp 242–247 | Cite as

Estimation of linear energy transfer distribution for broad-beam carbon-ion radiotherapy at the National Institute of Radiological Sciences, Japan

  • Nobuyuki Kanematsu
  • Naruhiro Matsufuji
  • Taku Inaniwa


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.


Relative 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.

Ethical approval

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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Copyright information

© Japanese Society of Radiological Technology and Japan Society of Medical Physics 2018
corrected publication April 2018

Authors and Affiliations

  1. 1.Medical Physics SectionNational Institute of Radiological Sciences HospitalChibaJapan
  2. 2.Department of Accelerator and Medical PhysicsNational Institute of Radiological SciencesChibaJapan

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