Preliminary Performance Evaluation of Adaptive Multi-Pinhole Collimators for SPECT

Abstract

Previously we optimized the multi-pinhole collimator designs for clinical brain, cardiac and preclinical imaging of rats based on a clinical single photon emission computed tomography (SPECT) scanner. The aim of this study is to evaluate the performance of these adaptive multi-pinhole (MPH) collimators with physical point source experiments. Three MPH collimators dedicated for small animal imaging with six-pinhole (6-PH), brain imaging with nine-pinhole (9-PH), and cardiac imaging with twelve-pinhole (12-PH) were tested in terms of sensitivity and spatial resolution. Collimators were mounted on a clinical SPECT scanner separately and projection data were collected using a 57Co point source of ~100 μCi placed in the field-of-view (FOV). For each experiment, projections were acquired for 5 mins and results of three acquisitions were averaged. Sensitivity measured as detected counts/emitted counts and system resolution measured as full-width-at-half-maximum of the point spread function at the center of the FOV (CFOV) were found as 0.012% and 1.7 mm, 0.037% and 11.6 mm, and 0.036% and 9.2 mm for 6-PH, 9-PH and 12-PH respectively. Results show that both sensitivity and resolution are in good agreement with the theoretical calculations. Adaptive MPH collimators provide better performance than conventional parallel hole collimator and can be used in preclinical and clinical studies with high performance, enhancing the general-purpose SPECT imaging platform for tasks with smaller FOV.