Patient specific conversion of CT number to effective density in proton therapy treatment planning

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K19215
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Medical Physics and Radiological Technology
• Research Institution: National Institutes for Quantum and Radiological Science and Technology
• Principal Investigator: Inaniwa Taku 国立研究開発法人量子科学技術研究開発機構, 放射線医学総合研究所 加速器工学部, チームリーダー(定常) (10446536)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 陽子線治療 / 阻止能比 / 線量計算 / 飛程誤差 / X線CT / X線の硬質化

Outline of Final Research Achievements

The purpose of this study is to increase the accuracy of patient stopping power ratio (SPR) estimation, and to decrease the proton range error in treatment planning. One of the uncertainty sources of proton range estimation in patients is the energy dependence of SPR not commonly accounted for by dose calculation algorithms. The range error due to this source can be minimized by assuming a suitable energy in SPR estimation in patients. We determined the effective energies for proton to be 70 MeV. Another uncertainty source is the insufficient correction of the beam-hardening effect arising from the mismatch between the size of the object and the calibration phantom used. The uncertainty would be minimized by selecting the suitable size of the x-ray calibration phantom in construction of the CT number-to-SPR conversion function. The size was 21.0 cm, which can be used for whole patient body in clinical practice.
Parts of this study have been published in PMB.

Free Research Field

医学物理学