Design of a motion simulation system to assist respiratory gating for radiation therapy.

Unlabelled: Stereotactic ablative radiotherapy (SABR) aims to deliver high doses of radiation to kill cancer cells and shrink tumors in less than or equal to 6 fractions. However, organ motion during treatment is a challenging issue for this kind of technique. We develop a control system via Bluetooth technology to simulate and correct body motion during SABR.

Methods: Radiation doses were analyzed, and the radiation damage protection capability was checked by external beam therapy 3 (EBT3) films irradiated by a linear accelerator. A wireless signal test was also performed. A validation was performed with 8 previously treated patient respiratory pattern records and 8 healthy volunteers.

Results: The homemade simulation system consisted of 2 linear actuators, one movable stage with a maximal moving distance of 6.5 cm × 12.5 cm × 5 cm to simulate the respiratory pattern of 8 patients precisely with a median error of 0.36 mm and a maximal motion difference of 1.17 mm, and 3.17 and chipset transited signals to display them as a waveform. From the test with 8 volunteers, the chip could detect deep respiratory movement up to 3 cm. The effect of the chip on a radiation dose of 400 monitor units (MUs) by 6 MV photons and 200 MUs by 10 MV photons showed high penetration rates of 98.8% and 98.6%, respectively.

Conclusions: We invented a tubeless and wireless respiratory gating detection chip. The chip has minimal interference with the treatment angles, good noise immunity and the capability to easily penetrate a variety of materials. The simulation system consisting of linear actuators also successfully simulates the respiratory pattern of real patients.