Calibration and correction of a modular cylindrical SPECT system (McSPECT-II)

The authors have developed a multi-crystal SPECT (McSPECT-II) system for clinical brain imaging. This system features a stationary cylindrical detector and a rotating collimator. The cylindrical detector is comprised of 120 NaI(Tl) crystal bars coupled to 24 columns ×3 rows of PMTs. Each PMT output is digitized by an ADC. Position calculations, and the associated calibrations and corrections are performed using software and look-up-tables on a Pentium-based PC. The collimator has four quadrants, each consists of a parallel array of collimator units. The four corner wedges between adjacent quadrants are utilized to accommodate line sources for system calibrations. The authors report the calibration and correction procedures developed for the McSPECT-II system. These procedures are: (1) azimuthal bar identification, (2) floating energy windows, (3) axial linearity correction and (4) uniformity correction. Results of these calibrations and corrections are also reported