Silicon detector for a Compton camera in nuclear medical imaging

Electronically collimated gamma cameras based on Compton scattering in silicon pad sensors may improve imaging in nuclear medicine and biomedical research. The work described concentrates on the silicon pad detector for a prototype Compton camera. The silicon pad sensors are read out using low noise very large scale integration (VLSI) CMOS chips and novel fast triggering chips. Depending on the application, a lightweight and dense packaging of sensors and its readout electronics on a hybrid is required. We describe the silicon pad sensor and their readout on the newly designed hybrid. We also present a modular and low-cost data acquisition system (CCDAQ) based on a digital signal processor which is interfaced to the EPP port of widely available personal computers. Using the CCDAQ and the hybrids energy spectra of gamma-ray photons from technetium (₄₃^99mTc) and americium (₉₅²⁴¹Am) were acquired with an energy resolution of 2.45 keV full-width at half-maximum (FWHM) for the 140.5-keV photo-absorption line of ₄₃^99mTc. For all pads, the discrimination threshold in the trigger chip was between 15 and 25 keV.