title: Early clinical experience utilizing scintillator with optical fiber (SOF) detector in clinical boron neutron capture therapy: its issues and solutions.
abstract: BACKGROUND
  Real-time measurement of thermal neutrons in the tumor region is essential for proper evaluation of the absorbed dose in boron neutron capture therapy (BNCT) treatment. The gold wire activation method has been routinely used to measure the neutron flux distribution in BNCT irradiation, but a real-time measurement using gold wire is not possible. To overcome this issue, the scintillator with optical fiber (SOF) detector has been developed. The purpose of this study is to demonstrate the feasibility of the SOF detector as a real-time thermal neutron monitor in clinical BNCT treatment and also to report issues in the use of SOF detectors in clinical practice and their solutions.
  
  
  METHODS
  Clinical measurements using the SOF detector were carried out in 16 BNCT clinical trial patients from December 2002 until end of 2006 at the Japanese Atomic Energy Agency (JAEA) and Kyoto University Research Reactor Institute (KURRI).
  
  
  RESULTS
  The SOF detector worked effectively as a real-time thermal neutron monitor. The neutron fluence obtained by the gold wire activation method was found to differ from that obtained by the SOF detector. The neutron fluence obtained by the SOF detector was in better agreement with the expected fluence than with gold wire activation. The estimation error for the SOF detector was small in comparison to the gold wire measurement. In addition, real-time monitoring suggested that the neutron flux distribution and intensity at the region of interest (ROI) may vary due to the reactor condition, patient motion and dislocation of the SOF detector.
  
  
  CONCLUSIONS
  Clinical measurements using the SOF detector to measure thermal neutron flux during BNCT confirmed that SOF detectors are effective as a real-time thermal neutron monitor. To minimize the estimation error due to the displacement of the SOF probe during treatment, a loop-type SOF probe was developed.
authors: Department of Biomedical Science and Engineering, Graduate School of Health Science, Hokkaido University, N-12 W-5 Kita-ku, Sapporo, Hokkaido, 060-0812, Japan. masayori@med.hokudai.ac.jp.
authors: Masayori
authors: M
authors: Ishikawa
authors: Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan.
authors: Tetsuya
authors: T
authors: Yamamoto
authors: Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan.
authors: Akira
authors: A
authors: Matsumura
authors: Department of Radiation Oncology, Kawasaki Medical School, Okayama, 701-0192, Japan.
authors: Junichi
authors: J
authors: Hiratsuka
authors: Department of Neurosurgery, Osaka Medical College, Osaka, 569-0084, Japan.
authors: Shin-Ichi
authors: S
authors: Miyatake
authors: Graduate School of Dentistry, Osaka University, Osaka, 565-0871, Japan.
authors: Itsuro
authors: I
authors: Kato
authors: Research Reactor Institute, Kyoto University, Osaka, 590-0494, Japan.
authors: Yoshinori
authors: Y
authors: Sakurai
authors: Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan.
authors: Hiroaki
authors: H
authors: Kumada
authors: Department of Biomedical Science and Engineering, Graduate School of Health Science, Hokkaido University, N-12 W-5 Kita-ku, Sapporo, Hokkaido, 060-0812, Japan.
authors: Shubhechha J
authors: SJ
authors: Shrestha
authors: Research Reactor Institute, Kyoto University, Osaka, 590-0494, Japan.
authors: Koji
authors: K
authors: Ono
mesh_terms: D016754:Boron Neutron Capture Therapy / Q000379:methods*; D002138:Calibration; D003199:Computer Systems; D005336:Fiber Optic Technology / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D055100:Optical Fibers; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*
keywords: Clinical trial BNCT; SOF detector; Thermal neutron monitor; Ultra-miniature detector