[Invention and Evaluation of a Novel Air Leak Check System for Vacuum-type Patient Immobilization Device]

We developed a novel system to measure air leakage in vacuum cushions, which are used in high-precision radiation therapy. The purpose of this study was to verify the usefulness of this system by evaluating the accuracy and the capability for detecting air leakage.

The novel system was used to measure pressure in the cushion using a manometer. The advantage of this system was that we can measure the pressure without deformation of the cushion and check the pressure immediately. We confirmed that the pressure measured using this system is proportional to the reading in the reference manometer by the coefficient of 1.0. This system had a higher capability in the leak detection than the capability by checking softness in our sense of touch. We checked the leakage using this system against 18 cushions without air leakage (NL group) and 7 cushions that had problems regarding usage in patients due to the leakage (CW group). Average pressure variations in the NL group and the CW group were 22 kPa and 46 kPa, respectively. This was a significant difference in both groups. We could decide the criteria of pressure in the cushions that may cause troubles in the future use.

We concluded that this system can detect air leakage in the cushions with a higher detectivity than our tactile sense.