What is proton therapy?
Proton therapy is a type of radiotherapy that involves accelerating protons, which are atomic nuclei of hydrogen, and directing them toward tumors. It has been used as a cancer treatment method for more than 60 years, with a cumulative total of more than 400,000 treatments worldwide.
In conventional radiotherapy, X-rays are commonly used and have the characteristic of depositing their maximum dose around the surface of the body and gradually decreasing in dose as they travel through the body. Therefore, when X-rays are used to sufficiently damage a tumor deep inside the body, they can also cause significant damage to normal tissues on the body’s surface. Proton beams, in contrast, enter the body from the surface with a low radiation dose and then stop at a specific depth. It enables highly targeted irradiation of the tumor while minimizing damage to surrounding healthy tissues and reducing side effects.
However, there are only 106 proton therapy facilities in operation worldwide (as of 2023). This means that proton therapy reaches only a small percentage of the 10 million new cancer cases worldwide each year. The big reason that the spread of proton therapy is slow is the huge size of systems and the high costs of installation.
The two keys to achieve “ultra-compact” size
B dot Medical has taken a unique approach to this problem. Furukawa, president and CEO of B dot Medical, believes that a little downsizing would not be enough to spread the use of proton therapy, so he set his sights on a system about the same size as the LINAC (X-ray therapy system). The combination of two key technologies was necessary to achieve “ultra-compact.”
Left: Conventional proton irradiation system
Center: B dot Medical’s proton irradiation system
Right: LINAC (X-ray therapy system)
Unprecedented system design
In the process of designing the ultra-compact system, it was imperative to depart from the traditional structure. Typically, a rotating gantry structure is employed to achieve irradiation from multiple directions, necessitating a large-scale system that revolves magnets weighing tens of tons around the patient’s body in a complete 360-degree rotation.
Therefore, Furukawa has defied this conventional notion and introduced an entirely innovative structure known as the “magnetic gantry”. By optimizing the magnetic field, it bends the beam itself, eliminating the requirement for a sizable structure and enabling irradiation from any desired angle.
How did he come up with the idea of a magnetic gantry?
“We explored various designs, drawing from our experience of downsizing heavy-ion therapy systems at NIRS (National Institute of Radiological Sciences). However, we soon realized that continuing down that path was not feasible. We kept thinking of alternatives for irradiating proton beams without rotation, and one day, I had a breakthrough idea: we could split the machine in half and bend the proton beams,” explains Furukawa. Therefore, the birth of the magnetic gantry with unprecedented and revolutionary functions accelerated the development process.
Superconductivity technology adopted for further downsizing
Achieving the functionality of the magnetic gantry alone could be accomplished with conventional conductive electromagnets. However, bending proton beams requires generating a strong magnetic field, and the adoption of conventional conductive electromagnets would inevitably lead to a large-sized device. This would make it impossible to achieve the desired “down-sizing.” This is where superconducting electromagnets entered the picture.
Superconducting technology has gained attention in recent years, not only in applications such as maglev trains. When the coils made from superconducting materials are cooled to temperatures close to absolute zero (-273 degrees Celsius), they exhibit zero electrical resistance due to the phenomenon of superconductivity. As a result, superconducting electromagnets can generate much stronger magnetic fields than conventional electromagnets.
The winding process for the superconducting coils, which initially appeared mundane, played a vital role in supporting the core of the device. Reflecting on the situation at the time, Takeshita, the head of the technical development department and one of the founding members of B dot Medical, stated:
“At that time (2019), B dot Medical consisted of founding members from the National Institute of Radiological Sciences (NIRS) and several experienced technicians who had strong connections from our time at NIRS. We had countless discussions, scrutinizing the device design drawings. Those days were filled with joy and excitement. On the other hand, we faced numerous challenges in the realm of ‘manufacturing,’ something we had never experienced before. To determine how to create the core components of the device, we sought advice from various companies through our connections from NIRS. When we finally saw the possibility of in-house production, it was a relief.”
From drawing to real thing
In 2020, with the installation of a dedicated winding machine, B dot Medical commenced in-house production of the coils with the entire technical development department mobilized for the task. Nakayama, a member of the technical development department who played a key role in the forefront of the winding process, talks about his thoughts at the time:
“It was an exciting feeling to see something we had only seen in drawings and models finally enter the manufacturing phase and become a reality. We were creating electromagnets by winding superconducting wires around an iron core, but it was crucial to align the wires perfectly straight during the winding process. It sounds simple, but it was unexpectedly challenging. If even the slightest gap existed, the coil would move when energized. So, initially, we had to redo the winding multiple times. Being entrusted with the core part of the device, which would be used to treat many cancer patients, brought both significant pressure and a sense of fulfillment that I had never experienced before.”
To become the manufacturer hospitals demand
The superconducting electromagnets were completed in 2021 (press release). Subsequently, during a demonstration test conducted at Osaka University, they successfully cooled the electromagnets to -270 degrees Celsius and confirmed the attainment of the superconducting state (press release). This validated the concept of the ultra-compact proton therapy system. It is the crystallization of B dot Medical’s technological prowess, achieved through the relentless efforts of researchers.
Thanks to its size, B dot Medical’s proton therapy system can be installed without the need for large-scale facilities. The company strives to support hospitals considering its implementation and provide the best possible treatment for patients.
