Challenges for neutron imaging toward low-dose particle therapy

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H06298
• Research Category: Grant-in-Aid for Challenging Research (Pioneering)
• Allocation Type: Single-year Grants
• Research Field: Biomedical engineering and related fields
• Research Institution: Waseda University
• Principal Investigator: Kataoka Jun 早稲田大学, 理工学術院, 教授 (90334507)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: 中性子イメージング / 粒子線治療 / 2次被ばく / TOF弁別 / PSD弁別

Outline of Final Research Achievements

The problem of "secondary exposure" is becoming more serious in proton beam therapy for cancer treatment. The proton beam reacts with the metal collimator when it is focused, and it also produces a large amount of fast neutrons in the patient's body. These incidental doses cannot be accurately evaluated by the current treatment system and cannot be reflected in the treatment plan. In this research, we developed an innovative imaging method for fast neutrons, and succeeded in imaging with a proton beam that mimic the actual treatment site. Specifically, we fabricated an array type detector consisting of two layers of waveform discrimination type plastic scintillator, and estimated the neutron arrival direction from the kinematics of elastic scattering. We tried to estimate the dose equivalent using the G(E) function method from the acquired neutron images. We conclude that about 1/100 of the the primary proton dose is given by fast neutrons during the proton therapy.

Free Research Field

放射線計測、医学物理学、高エネルギー宇宙物理学

Academic Significance and Societal Importance of the Research Achievements

陽子線治療は先進医療の代表であり、抗がん剤や手術よりQOL(Quality of Life)が高く社会復帰の早い治療法として近年ますます需要が高まっている。一方で、放射線治療はその性質上、正確な線量評価が不可欠である。本研究で開発した中性子可視化技術は「2次被ばく」の評価を初めて可能にし、今後の高精度治療へ向けた大きな足掛かりとなる。さらに、次世代治療として注目を集めるホウ素中性子捕獲療法(BNCT)、原発内部のエリアモニタやテロ対策に至るまで、多くの分野で迅速に中性子場を可視化するカメラの開発が切望されており、本研究の技術が確実に生かされると期待される。