Feasibility of Implementing the PILATUS CdTe 300k Detector as a Real Time Gamma Camera in Intraoperative Medical Imaging

Abstract: The full-width-at-half-maximum of the point spread functions for a pixellated cadmium telluride detector exposed to gammas from a 140.5 keV Tc-99m source are modelled in GATE, at a detector-collimator distance of 5 cm, and collimator-source distances of 5 cm and 10 cm, with lead pinholes of diameter 1.0 mm, 1.5 mm, 2.0 mm and 5.0 mm acting as collimators. The PILATUS3 X CdTe 300k detector from Dectris was then used to image a custom phantom with the same set up as in simulations at the Austin hospital in Melbourne, Australia. The exposure time was also varied, with the aim to establish if the detector could be repurposed for applications within medical imaging, more specifically as a gamma camera in guided sentinel lymph node biopsy. Moreover, the quantum efficiency of the detector, hitherto unknown, was calculated. Results found that the 2.0 mm and 5.0 mm would be particularly suited for real time imaging and intraoperative use, with exposure times of 30 s and 5 s resolving 3.0 mm and 8.5 mm respectively. The smaller pinhole sizes achieved resolutions of down to 1 mm with longer exposures of 120 s and 300 s, showing promise for application in single photon emission computed tomography. For both a detector-collimator and collimator-source distance of 5 cm, the simulated spatial resolution was in agreement with the experimental results, validating the use of simulations to model such situations. The CdTe sensor was found to have an intrinsic quantum efficiency of 20.8%, confirming its superiority over other semiconductor counterparts such as silicon.