As the demand for radiation therapy increases, an appropriate breathing training has been becoming a vital element to improve the accuracy and efficiency of radiation therapy. It is important for patients to maintain the
constant respiratory cycle due to difficulties of identifying exact treatment site of respiratory organs, which move with every breath of patients (e.g. part of thorax or abdomen). In order to train the patient's periodic
breathing and evaluate patient’s respiratory cycle quantitatively, we have developed magnetometer based respiratory training system. Before subject experiment, mechanical simulation was performed to evaluate stability
of the developed devices. The correlation between sensor module and subjects’ respiratory motion was confirmed in the mechanical simulation, and then the possibility of measuring respiratory cycle of patients by
using the magnetometer was verified through subject experiment. So, it is found that the developed device improves efficiency of breath training based on visual bio-feedback, and then general use in clinical practice is
expected.