TY - JOUR T1 - Calibration and image reconstruction techniques dedicated to ultra-high resolution SiliSPECT JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2003 LP - 2003 VL - 52 IS - supplement 1 AU - Sepideh Shokouhi AU - Ben McDonald AU - Scott Metzler AU - Todd Peterson Y1 - 2011/05/01 UR - http://jnm.snmjournals.org/content/52/supplement_1/2003.abstract N2 - 2003 Objectives SiliSPECT is a dual-headed, stationary SPECT for mouse brain imaging. Two silicon double-sided strip detectors (DSSDs) are stacked in each camera head to enable dual projection magnification and image reconstruction despite multiplexing of pinhole projections. We previously verified the potential of this synthetic collimation using simulated data. The experimental implementation requires dedicated calibration for stacked detector geometry and should be less sensitive to abrupt changes in the detector response that occur in semiconductor detectors. Methods The calibration phantom consists of a translating/rotating I-125 brachytherapy seed. The calibration parameters consist of the pinhole acquisition geometry for front and back detectors, the phantom position and the axis of rotation, which simulates an orthogonal view of the object. The use of an extended source results in pinhole projections of greater spatial extent than a point source. An algorithm was devised to identify the cluster of pixels comprising a pinhole projection and assign the centroid based on its spatial extent instead of the distribution of counts, reducing sensitivity to noise and variations in detector response. Analytical expressions for the projection centroids of the calibration phantom were used to calculate linear systems and estimate the calibration parameters using the Nelder-Mead downhill simplex. The calibration parameters for front and back detectors are estimated both simultaneously and separately. Results We evaluated the effect of the calibration setup, estimation method and detector non-uniformities on the estimation accuracy using both simulated and experimental data. Conclusions Joint estimation of front and back detectors provides additional constraints on common parameters and resulted in improved convergence. In particular, the front detector benefit from it, since the projection image is acquired at low magnification. Research Support NIH/NIBIB R33 EB000776,US DOE DE-SC000243 ER -