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Introduction to Radixact TomoTherapy
In Japan, the current standard for radiotherapy is three-dimensional conformal radiotherapy, in which radiation is administered based on the shape of the lesion, using three-dimensional CT, MRI, or FDG-PET/CT imaging for reference. However, in some cases, a sufficient dose of radiation cannot be delivered to the lesion, because of the danger posed to other organs nearby that should not be exposed to too much radiation. Intensity-modulated radiation therapy (IMRT) is a treatment method in which the shape of the radiation beam and the radiation dose can be varied, to concentrate the radiation on the lesion while minimizing radiation exposure to organs that would be at risk of harm.
In 2018, we introduced a leading-edge Radixact TomoTherapy machine, which performs IMRT. What makes the TomoTherapy machine unique is the miniaturized irradiator that moves 360° around the body like a CT scanner as the patient’s bed moves; this allows for a great deal of freedom in selecting irradiation angle and dose, and enables continuous irradiation of sites spread across a large area. It is also possible to take verification images using the machine and superimpose them on the plan images, for accuracy down to the millimeter level. In addition, the Radixact can increase irradiation speed to shorten treatment time and correct for bed position error, for more efficient, more precise treatment.
IMRT is becoming more and more common as a treatment for prostate cancer, head and neck cancer, and brain tumors, and its use is now being expanded to include localized malignant tumors. Although prostate cancer is the cancer we most commonly treat at our hospital, we can now also treat chest and pelvis tumors, and small numbers of metastatic brain tumors and lymph node metastases; IMRT can also be used for whole neuro-axis irradiation and total body irradiation. Administering IMRT requires several specialists with sufficient radiotherapy experience; as a result, there are few facilities in Toyama Prefecture able to offer IMRT. We will continue to build more experience in this technique, in order to provide this high-precision radiotherapy to more patients, for more types of cancer.
