Imaging the biodistribution of single photon emitting radiotracers in small animals and in the breast with high resolution and high sensitivity is an important challenge. Recent work has shown that single photon emission computed tomography (SPECT) imaging of small objects with coded aperture collimators and iterative image reconstruction may provide an order of magnitude increase in sensitivity yet maintain high spatial resolution. We propose a new system design with compact detectors for single photon small animal and breast imaging. Key features are 1) mulitpinhole masks for improved sensitivity, 2) pixellated NaI(Tl) scintillator arrays with small crystals for high resolution and 3) flat panel or flangeless compact position sensitivie photomultiplier tubes. Analyses for a multipinhole small animal device with four 10 cm x 20 cm detectors and 1.5 mm detector resolution indicate that 0.9-1.3 mm resolution in image space could be achieved for 0.5-0.8 mm diameter pinholes with geometric sensitivity of 0.2-0.6%, where a point in the brain is imaged through 20 pinholes/mask. A design for a multipinhole breast imager incorporates 20 cm x 20 cm pixellated detectors and lower magnification. Predicted image resolution in the center of the field of view is 1.9 mm for 0.8 mm pinholes, with sensitivity of about 0.045% in the center of the field of view for breast tissue imaged through 20 pinholes/mask. Additional modeling, iterative image reconstruction, device component and phantom tests are desirable to optimize device specifications.

This work was supported by U.S. DOE under contract DE-AC05-84ER40150. Also supported by the Office of Biological and Environmental Research of the Office of Science of the U.S. Department of Energy.

Authors: Mark F. Smith, Stan Majewski, Steven R. Meikle, Andrew G. Weisenberger, Vladmimir Popov, Randolph F. Wojcik

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