An investigation of coded aperture imaging for small animal SPECT

Coded apertures provide a substantial gain in detection efficiency compared with conventional collimation and are well suited to imaging small volumes . In this work, we investigated several aspects of coded aperture design fo r a small animal SPECT system, including aperture/detector configuration, s ampling requirements, and susceptibility to scatter. We simulated various s ource distributions and detection systems which included one, two, and four stationary detectors placed around the object, each with a pinhole array o r a Fresnel zone plate in front of the detector. Image volumes were reconst ructed using an iterative successive over-relaxation algorithm with a penal ized weighted least squares cost function. Multiple pinhole arrays performe d better than Fresnel zone plates in terms of reconstructed mean squared er ror and signal-to-noise. Our design goals of <2 mm spatial resolution (full width at half maximum) and >1% detection efficiency can be achieved with a four-detector system with arrays of 100 pinholes per detector and the scat ter fraction for a 2-cm diameter object is <5%. We conclude that a coded ap erture design shows great promise for small animal SPECT.