First Imaging Data with C-SPECT: A Dedicated Human Cardiac SPECT Imager

C-SPECT is a human cardiac SPECT system designed to acquire all necessary views for imaging simultaneously. The system uses slit-slat collimation focused on a cylindrical region with the capability of identifying the heart either through a scout or transmission image and then re-positioning the patient so the heart is in the common field of view (FOV) of all active slits. The system is adaptive in that the (i) slats used for axial collimation have two modes, high resolution (HR) and high sensitivity (HS), with actuators to control switching while imaging; and (ii) slits move on a track in front of a fixed detector system to exchange different combinations of resolution, sensitivity, and FOV. With the simultaneous acquisition of all needed views, the system is capable of dynamic cardiac imaging. The system has been under development for several years, first at Rush University and now at the University of Pennsylvania. We have recently reached several key milestones in the project: (i) completion of the detector system; (ii) design and fabrication of the conveyor that serves as the system gantry and exchanges slits; (iii) completion and installation of the adaptive slat stacks; and (iv) acquisition of the first sets of imaging data. The detector modules use 2.5 x 3.0 mm (transverse x axial) pixelated NaI(Tl) crystals (10 mm deep). Pixel ID for the 14 modules has been successfully implemented with typical energy resolution of about 11% at 140 keV. Initial sensitivity measurements are consistent with expectations, which vary from 5x10-4 to 20x10-4, depending on configuration. Similarly, resolution also depends on the configuration. We have measured FWHM axial resolution of 24 mm at the center, consistent with expectations of 28 mm in HS mode and supporting the predicted 14 mm resolution in HR mode. Transverse resolutions depend on the minification for slit-slat collimation. The complete initial imaging performance will be presented in comparison with design expectations.