An Investigation to Design High Performance Multi-Pinhole Collimator

The aim of this study is to design a detector module employing multi-pinhole collimator which could be utilized in various SPECT systems. Monte Carlo simulations using Geant4 application for tomographic emission (GATE) were performed to estimate the performance of various multi-pinhole collimators and compared to that of low energy high resolution (LEHR) parallel-hole collimator. The simulated detector module was designed to have 100 mm times 100 mm field of view. In order to determine the optimal number of pinholes, the number of pinholes having 2 mm pinhole diameter and 50 mm focal length was varied from 1 to 225. Perpendicular lead septa were employed to acquire non-overlapping projections and to improve reconstructed image quality. The proposed multi-pinhole detector module was evaluated by the reconstructed images of simulated phantoms. Planar sensitivity and resolution obtained using 81-pinhole collimator were 1.9 cps/muCi and 8.7 mm FWHM at 225 mm distance. 81-pinhole configuration demonstrated better resolution and comparable sensitivity compared to LEHR parallel-hole collimator (2.0 cps/muCi and 10.9 mm FWHM). Multi-pinhole detector module could provide the reconstructed images of 120 mm diameter phantoms without truncation while LEHR parallel-hole detector provided the truncated images. The designed multi-pinhole detector module which could be extended to cover large FOV allows to achieve high quality images even with reduced projection data.