In Japan, 900,000 people are diagnosed with cancer every year, and more than 350,000 die from it.
Advances in medicine have led to the development of treatments for various diseases and reduced mortality rates, but no fundamental and decisive treatment for cancer has yet been found.
BNCT, a type of radiation therapy that uses neutrons, has the potential to enable radical treatment.
Focusing on this, we are proceeding with development so that BNCT, which previously required large-scale facilities, can be installed in many hospitals.
BNCT (Boron Neutron Capture Therapy) is a radiation cancer therapy that combines neutron beams and boron preparations.
When a drug combined with boron is administered to a patient and irradiated with a neutron beam, the boron and the neutron beam cause a nuclear reaction, producing a powerful particle beam (alpha beam, 7Li particles).
This particle beam destroys cells within a radius of about 10 microns. The major feature of this method is that it destroys only cancer cells and has very little effect on healthy cells.
History of BNCT
Clinical studies on BNCT have been conducted since the 1960s, and Japan has conducted the most clinical studies. More than 500 clinical cases have been reported at Kyoto University alone, mainly using neutrons generated in an experimental reactor at Kyoto University, and its effectiveness has been confirmed. However, because it requires a nuclear reactor to generate neutrons, it has only been clinically studied and has not been widely applied to treatment.
Therefore, in recent years, attempts have been made to perform BNCT treatment with neutron beams generated from neutron sources using large accelerators such as cyclotrons and RFQ (Radio Frequency Quadrupoles) linacs, instead of nuclear reactors.
However, both of these accelerators are large facilities with acceleration tubes about 10m long, and the high cost of installation, such as the need for a dedicated shielding building, was an issue.
We have succeeded in significantly miniaturizing the accelerator for generating neutrons.
Conventional large accelerator neutron sources generate neutrons by irradiating metals such as Li and Be with ions accelerated at extremely high voltages of several MV to several tens of MV. A large accelerator was required.
In contrast, our accelerator generates neutrons by bombarding deuterium (D) with deuterium ions accelerated at a relatively low voltage of 100-400 kV to cause a nuclear fusion reaction (DD reaction). increase.
Neutrons can be generated with a very small electrostatic accelerator (about 70 cm in length) because the acceleration voltage is about 1/100 that of the conventional method.
The DD reaction is a well-known reaction, but in order to generate the neutron dose required for BNCT treatment, this reaction requires a very large number of ion bombardments, voltages and currents of 100-400 kV and 100-500 mA. A power supply capable of generating such a voltage and current has not been put into practical use until now. We succeeded in generating a sufficient amount of neutrons with this compact accelerator by commercializing this high-voltage, high-current power supply.
In addition, the self-shielding of the device has been realized by low acceleration voltage and miniaturization.
Multi-field irradiation technology
Since the accelerator is small, it is possible to realize a device that irradiates neutrons from multiple directions. This is called multi-gate irradiation.
Conventional BNCT irradiates neutrons from only one direction, but with this method, a sufficient amount of neutrons for treatment can only be irradiated to a depth of about 5 cm from the body surface.
On the other hand, in multi-gate irradiation, it is possible to irradiate a sufficient amount of neutrons to the deep part of the body by irradiating neutrons from 3 to 10 neutron sources (directions) at once.
For example, when irradiating from one direction using a neutron source that can irradiate neutrons with an intensity of 10 at the body surface and attenuating to an intensity of 1 deep inside the body, it is possible to irradiate from n directions at the same time. , theoretically, it is possible to irradiate the deep part of the body with n times stronger neutrons.
By using this multi-gate irradiation technology, it is possible to irradiate a sufficient amount of neutrons to a depth of about 25 cm from the body surface.
Below are images of the accelerator installed in six directions and a photograph of the DD accelerator.
Kyoto Prefectural University of Medicine Project
On November 22, 2016, four companies, Kyoto Prefecture, ROHM Co., Ltd., Kyoto Prefectural University of Medicine, and Fukushima SiC Applied Giken Co., Ltd., made press announcements.
Kyoto Prefectural University of Medicine and Fukushima SiC Applied Giken Co., Ltd. will conduct research and development of treatment equipment (SiC-BNCT equipment) necessary for BNCT using ROHM Co., Ltd.'s SiC, with the aim of developing cutting-edge cancer treatment. implement.
Based on the results of research and development, ROHM Co., Ltd. will donate SiC-BNCT equipment and buildings to Kyoto Prefecture so that cutting-edge cancer treatment can be performed.
We announced that we have reached a basic agreement on two points: the implementation of research and development of therapeutic equipment required for BNCT, and the donation of SiC-BNCT equipment and buildings by ROHM Co., Ltd. to Kyoto Prefecture.
Based on this agreement, we delivered a BNCT clinical trial machine to Kyoto Prefectural University of Medicine in July 2021.