A CAPACITIVE MONITORING SYSTEM FOR STEREOTACTIC RADIOSURGERY: DETECTOR DESIGN

Abstract

In this thesis, a novel capacitive detector allowing near real-time monitoring of the cranium during stereotactic radiosurgery (SRS) is developed and evaluated. The variation in sensitivity (signal change per mm) was investigated with regard to: (i) the material of the capacitive plate, (ii) the shape of the plate and (iii) the area and thickness of the plate. This was carried out using a parallel plate setup. Several designs were investigated in a limited volunteer study with the detector proximal to the cranium. The proposed capacitive detectors demonstrated acceptable sensitivity for guidance of SRS, up to 41 %/mm, and could be read out at 200 Hz with coefficient of variation of 0.14 %. The detectors investigated here provide a range of 15 mm and are able to detect sub-millimetre patient motions. The detectors are sensitive to the position of the cranium inside a patient’s thermoplastic mask, but offer the advantage of being comparatively insensitive to the mask itself.