Purpose: Respiratory training to patients has been recommended to deliver planned radiation accurately to tumors that are moved by respiration in the thorax and abdomen. However, it is difficult to provide respiratory training to all patients because it requires additional space, time, and professional human resources. We developed portable self-respiratory training system that is based on patch type magnetic sensor; and evaluated the system for basic performance and clinical applicability.
Methods: The system, which is used with a sensor attached to the chest and a magnet to the back, is designed to monitor the patient's respiration by measuring changes of magnetic field strength according to movements of the chest surface. It consists of a micro-electro-mechanical-system (MEMS) based patch type magnetic sensor capable of wireless communication, magnet for measurement, and mobile application. To evaluate the performance of the system, we measured the level of systemic noise, the precision of a sensor for various breathing patterns, signals change for varying distances, and effects of the presence or absence of intermediate substances between the sensor and the magnet. Various respiration patterns were produced by the QUASAR respiratory motion phantom, and the data were analyzed by fitting method and peak value method.
Results: The sensor had a noise ratio <0.54% of the signal; average errors of signal amplitude and period for breathing patterns were 78.87 um and 72 ms, respectively. The signal could be measured consistently when the sensor-magnet distance was 15-20 cm. The signal difference was 1.89% for the presence or absence of a material, indicating that its influence on the measurement signal is relatively small.
Conclusion: The potential of the respiratory self-training system was confirmed by performance tests and clinical usability evaluation. In the future, we believe that the system could provide precise respiratory training to various patients through clinical trials.