Investigation of Designs for a Stationary Adaptive Multi-Pinhole Brain SPECT Employing Flat-Square Detector Modules

An adaptive-stationary-modular multi-pinhole (MPH) brain SPECT, AdaptiSPECT-C is being developed by the University of Arizona and University of Massachusetts Medical School to meet static and dynamic brain SPECT imaging needs. Salient features of the ASC include the use of adjustable pinhole apertures to dynamically adapt to imaging task needs, improved light measuring around the edge of the scintillator crystal, plus motion tracking and correction with attenuation correction enabled by usage of depth-sensing (DS)-cameras. For a target system spatial resolution of 8 mm at the focal point of the apertures, selected to enable comparison to current 2-headed commercial (2HC) SPECT imaging, we report investigation of aperture layout designs for a system with 3 rings of 18.4 cm flat square detector modules. We investigated sensitivity at the focal point in comparison to 2HC for usage of 1 versus 5 apertures per module, and variation in the extent of truncation and multiplexing of the irradiation fields by adjustment of the aperture location between the detector and focal point. For a system with one aperture per module and minor truncation we determined a sensitivity of 2.7x that of 2HC; whereas, with use of 4 oblique apertures with minor truncation and moderate multiplexing we determined the sensitivity was 4.6x, and with all 5 apertures resulting in significant multiplexing the sensitivity was 5.7x. We also determined through simulation better visualization of the rods of a Derenzo phantom, and perfusion distribution of XCAT brain phantom with the 5 pinhole design, using solely the 4 oblique pinholes. We thus believe that this design with 5 pinholes per detector module is an excellent candidate for use in construction of the AdaptiSPECT-C system.