QST and Sumitomo Heavy Industries develop multi-ion source, leading one step closer to implementing a quantum scalpel

Since 2016, the National Institutes for Quantum Science and Technology (QST) and Sumitomo Heavy Industries have been involved in the technological development of the components of a quantum scalpel, a next-generation device for heavy ion radiotherapy. Now, for the first time in the world, these two organizations have succeeded in advancing current heavy ion radiotherapy, which conventionally utilizes carbon-ion beams, by developing a multi-ECR ion source (multi-ion source) that will make it possible to achieve multi-ion treatments with ions such as neon, oxygen and helium.

Conventionally, only carbon-ion beams are used in heavy ion radiotherapy devices, but the quantum scalpel introduces multi-ion treatments that use an optimal combination of different ion beams in accordance with the malignancy of the tumor, so as to further improve its effectiveness in killing cells while reducing side effects. QST and Sumitomo Heavy Industries have developed a multi-ion source that serves as the injector of the quantum scalpel and installed this in QST's Heavy-Ion Medical Accelerator in Chiba (HIMAC). This ion source emits numerous multiply charged ions, from helium to neon, and can rapidly change the ion species in under a minute. Moreover, in preparation for future widespread use, it has been made maintenance-free and its size has been reduced to up to one fifth of the size of previous generations of the device to enable its installment in hospitals. This has been achieved by utilizing a permanent magnet and a semiconductor microwave amplifier.

Toshiyuki Shirai, Project Manager of the Quantum Scalpel Project, a QST Innovative Project, commented, "We expect to start building a dedicated structure for this in FY2023, with the aim of quickly putting the quantum scalpel into practice. The multi-ion source is the first device completed for this quantum scalpel, and we want to take the opportunity presented by this development success to aim for the rapid spread of heavy ion radiotherapy using a quantum scalpel."

■ Heavy ion radiotherapy: A treatment method that kills cancer cells by irradiating carbon-ion beams (that are accelerated to a speed of up to 70% the speed of light) into tumors with pinpoint accuracy from outside the body. Its advantages include the fact that it is a highly effective treatment method, even for cancers that are resistant to radiotherapy, with little cost to the patient, and that treatment can be given in a short space of time.

■ ECR ion source: Currently used in the ion-generation part of heavy ion radiotherapy devices, this device ionizes neutral atoms by using a strong magnetic field to confine high-energy electrons obtained through a phenomenon known as electron cyclotron resonance (ECR) and making repeated use of this.