Adaptation of a Brain-Dedicated Multipinhole SPECT System for Imaging Higher-Energy Photons of Theranostic Agents—A Simulation Study

Abstract

Multipinhole single-photon emission computed tomography (SPECT) of the brain is capable of producing high-resolution images. However, pinhole imaging of high-energy photons remains challenging due to the tradeoff of greatly sacrificing sensitivity to limit penetration through the edges of the pinholes and system shielding. The impact of photon penetration on spatial resolution, image contrast, and lesion signal-to-noise was assessed through simulation for the brain-dedicated multipinhole system AdaptiSPECT-C. In addition, minor changes to the system design to reduce penetration were considered; these were updating the materials of the pinhole aperture edges and shutters to a higher-density tungsten alloy and including platinum in the shielding around the pinhole apertures. A significant degradation in spatial resolution, image contrast, and signal-to-noise above approximately 200 keV was found with the current system design. It was shown that adapting the pinhole and shutter material to a higher-density tungsten alloy would greatly reduce this degradation and permit multipinhole imaging with 177Lu and 111In in the human brain. Incorporating a small amount of platinum around each aperture further improved the system point-spread function. However, results indicate high-resolution imaging of 131I would require a larger modification to the system design.