A solid state detector for intraoperative imaging

A beta detecting probe for intraoperative tumour imaging and localisation has been developed. The probe is based on a charge coupled device which detects the particles directly in its sensitive volume. The active area of the device is encapsulated within a carbon-fibre loaded plastic housing of 75 μm in thickness. Images are displayed in real time on a computer screen with a readout frequency of 1 MHz. A study of the effect of dark current on image formation at body temperature has demonstrated a reduction in the signal of ~55%. The advantage of this device for intraoperative tumour imaging is its minimal sensitivity to the background gamma radiation. This was confirmed using a ¹⁸F source separated by the CCD with a 2 cm perspex block to absorb the positrons. The linearity of the probe was also tested over an activity range of 1-100 μCi. Although the intrinsic resolution of the CCD was measured to be equal to 66 μm, the image resolution of the device was <200 μm. The sensitivity of the CCD at body temperature was 1120 counts/sec/μCi