Medical devices
SPECT system for boron neutron capture therapy (BNCT-SPECT) for real-timemeasurement of therapeutic effectPrincipal
Investigator

Division of Sustainable Energy and Environmental Engineering,
Graduate School of Engineering, Osaka University
Professor Isao MURATA

Project Outline

Boron Neutron Capture Therapy(BNCT) is a promising and quite new cancer therapy. However, the therapeu�ceﬀect cannot be known easily during the treatment (neutron irradia�on). The basic technique for that is to measure promptlyemi�ed 478 keV gamma-rays from boron neutron capture (BNC) reac�on with a SPECT system. However, it is known to be very
diﬃcult. This is due to the fact that BNCT is a treatment, not a diagnosis such as MRI and CT. More prac�cally, ①Primary radia�onfor BNCT is neutron, however, the SPECT measures secondary radia�on of extremely weak 478 keV gamma-rays. In addi�on, ②The SPECT system cannot move 360 deg. like X-ray CT due to various constraints, e.g., a pa�ent should contact the neutron exit
wall. As the result, it is known that the technical diﬃculty is cri�cally serious, and it is thus very hard to obtain accurate images.
Now, Japan lead BNCT in the world and Japan has ﬁrst started an accelerator based BNCT in a hospital. Considering this situa�on,we should put the SPECT system for BNCT (BNCT-SPECT) into prac�cal use in BNCT treatment as soon as possible.
Present status for diﬃcul�es ① and ②①Examina�on carried out under the support by thefollowing two JSPS KAKENHI. The tables below show thedesign result which meets requirements of BNCT clinicaldoctors (spa�al resolu�on of 5 mm and accuracy of 5 %)ﬁrst in the world.
・Grant-in-Aid for Scien�ﬁc Research (B), Grant Number 22360405(2010～2014), I. Murata
・Grant-in-Aid for Scien�ﬁc Research (B), Grant Number 15H04242(2015～2019), I. Murata②Supported by 「Masason Founda�on」, reconstruc�onof image was successfully performed even in case oflimited projec�on angles of 180 deg. with Bayesianes�ma�on. (H. Inamoto et al., “A New Image Reconstruc�onTechnique with Limited View-angle Projec�on Data for BNCTSPECT”, 2020 IEEE NSS MIC, Boston, USA, M-08-149 (2020).)③For further improvement of the accuracy, weemployed coincidence, an�-coincidence and vetodetector simultaneously to increase S/N ra�o, (Patentpending, 2022-210091, “SPECT system for real-�memeasurement of local boron dose for BNCT”)④Under the support of METI, Japan, the prototype
SPECT system is being developed now. In parallel, theimage reconstruc�on system was inves�gated toreproduce images with prac�cally measured data.

BNCT 10B is accumulated only in tumor cells by administering boron
drug, BPA and/or BSH. Then neutrons are irradiated to induce theneutron-10B reac�on above to emit α and 7Li par�cles, which kill thetumor cells selec�vely, because ranges of the emi�ed par�cles are aslong as cell size. It means, if 10B is accumulated only in tumor cells, only
the tumor cells are killed making adjacent normal cells survive. BNCT isthus a sharper therapy than other radiotherapies, i.e., called the only
tumor-cell selec�ve therapy.
BNCT-SPECT Emi�ed 7Li is in its excited state and immediately

decays crea�ng a 478 keV gamma-ray promptly. By measuring thegamma-ray with a SPECT system to es�mate the three dimensional
distribu�on (image) of the number of above reac�ons, that is, thetherapeu�c eﬀect of BNCT.

←Design andperformance of BNCTSPECT, cited from thepaper:
I. Murata et al.,“Design of SPECT for
BNCT to measure local
boron dose withGAGG scin�llator“,Applied Radia�on andIsotopes, 181, 110056(2022).

↑Cited from design criteria of BNCT compiled by IAEA (2021).
We aim to spread BNCT by employing an accelerator based neutron source instead of nuclear reactor. Japan is leading in BNCT andﬁve projects are underway in Japan, including our group. Accelerator based BNCT system is small and cheap compared toconven�onal nuclear reactor based BNCT, and thus one machine in one prefecture is aimed. It means, 50 BNCT-SPECT machines
are required inside Japan and ten to hundred �mes are required commercially in the world. We completed the basic performance
characteriza�on of the machine and now making the prototype machine to verify the real performance. Then we are aiming at
producing the real machine with a partner company.

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