A laser-based monitoring system for a deep-inspiration breath-hold in radiation treatment of breast cancer: feasibility study

A deep-inspiration breath-hold (DIBH) is a useful technique that can reduce the risk of radiation-related toxicity to major organs during radiation treatment (RT) of breast cancer. A laser sensor-based position monitoring system was developed to measure the absolute position of the object and to realize high accuracy and reproducibility during DIBH. A laser distance sensor (LDS) was manufactured to be mounted on a commercial breast board and to measure the absolute distance between the sensor and the patient's sternum. The absolute distance measured by using the LDS was evaluated for the movement generated by the motorized jack system. The respiration of five volunteers was measured by using the LDS and commercial real-time position management (RPM) to evaluate the correlation of the signals. The data measured by using the LDS for the input to the motorized jack had a relative error of 0.2%. At DIBH, the average correlation coefficient between the LDS and RPM was 0.98, and at FB, it was 0.84. The LDS and RPM showed almost similar timings for the rising and the falling portions, but the magnitudes of amplitudes were slightly different from each other. The LDS proposed in this study can easily reproduce patient setup and monitor DIBH without any disturbance from the treatment beam. The measuring accuracy of the LDS for the quantitative motion of a motorized jack system was successfully verified. The performance of the LDS compared to RPM in the FB and the DIBH of five volunteers was also clinically acceptable.