[Development of a respiratory monitoring device for truncal stereotactic radiotherapy using an abdominal pressure-detecting system with Stereotactic Body Frame].

The Stereotactic Body Frame, which was devised as a fastening unit for the irradiation of various truncal lesions, has obtained a good reputation for its high-precision reproductivity. This device is accessorized with 'Diaphragm Control', which can reduce the respiratory movement of intra-thoracic organs. In this study, to investigate the possibility of a respiratory monitor using our device, we try to clarify the relationship between the pressure against the abdominal board of 'Diaphragm Control' and each constrained tidal respiratory movement. Our original software was programmed to detect and analyze these data with our personal computer from some ready-made highly sensitive pressure detectors. In any fundamental performance of this system, response time is less than 1 msec at 115,200 bps, minimum detectable weight is 420 g, linearity correlation between loading weight and pressure index value is seen from 1000 g to 6000 g loading, and reproducibility of measurement is evaluated by coefficient of variation (CV=0.95% at 3000 g loading). It has sufficient capability to be used as a respiratory monitoring device during radiation therapy. In an experiment with three volunteers, the results revealed a positive correlation between pressure index value and ventilation air volume by spirometer. The decision coefficients (R(2)) were 0.7717, 0.7995, and, 0.8684, respectively. Our original respiratory monitoring device can be used for quantitative respiratory suppression and unexpected breathing detection without loading additional stress on the patient.