Optimising the HEXITEC-GigE detector system for use in intraoperative multi-isotope imaging

Dual-isotope 99mTc/123I parathyroid scintigraphy is a promising candidate technique for intraoperative multi-isotope imaging, but cannot be performed by the current generation of intraoperative gamma cameras. A new gamma camera based on a High-Flux CdZnTe detector and the HEXITEC-GigE module detector system would provide the necessary combination of high spatial and energy resolution for this challenging application.The requirements of an effective intraoperative scintigraphy tool were established by reviewing the development, design and performance of 17 intraoperative gamma cameras over the past decade. No existing system was found to be suitable for dual-isotope intraoperative scintigraphy. The most promising candidate devices were found to limited by charge sharing within semiconductor detectors. To understand current state-of-the-art performance, Seracam - a small field of view, small footprint, hybrid gamma-optical camera - was characterised. Seracam displayed best-in-class spatial resolution of 4.6-26.0 mm at 5 cm, with image quality dominated by spatial resolution rather than sensitivity. Seracam clinical simulation imaging demonstrated portable gamma cameras may be capable of visualising low-count parathyroid uptake.A novel processing pipeline was developed for HEXITEC data, combining an adaptive threshold method with a new multi-pixel event classification algorithm. The dynamic-snap method is a combination of these elements and offers long-duration stable imaging with average threshold values of 1.63±0.44 keV. All multi-pixel events up to four pixels in size are characterised by size and event shape; encompassing 99.996% of events at 141 keV and offering 35-38% improved performance compared to pre-existing algorithms. All high-likelihood multi-pixel events at 141 keV were investigated and the charge sharing mechanism responsible for each event shape was identified. A prospective multi-pixel event reconstruction algorithm has been proposed for the full recovery of >99.996% of events at 141 keV.A HEXITEC imaging system was developed and an anthropomorphic parathyroid phantom imaged using clinically-realistic imaging durations and 99mTc/123I activities. Matched imaging was performed on a clinical SPECT/CT camera. Comparable dual-isotope subtraction image quality was achieved. Time-sliced images approximated intraoperative imaging durations and activities; with the parathyroid clearly resolved within HEXITEC imaging. This demonstrates that the HEXITEC imaging system is suitable for multi-isotope imaging and has the potential to be a highly promising intraoperative device with further optimisation.