SU-E-I-182: Slit-Slat Collimators in a Staggered Array for Dedicated Breast SPECT

Abstract

Purpose: To compare slit‐slat collimators in single‐layer and staggered arrays with standard parallel‐beam collimators in a dedicated breast SPECT system. Methods: A ring of slit‐slat collimators surrounds a cylindrical region of 20 cm diameter for SPECTimaging of a pendant breast. A second ring of cameras, viewing between cameras in the first ring, may be added to give a staggered array of cameras. Such arrays could be static or rotating; for now, we assume a rotating array, for a radially symmetric ray pattern. Slit width and slat design are specified to match the spatial resolution of a low‐energy all‐purpose parallel‐hole (LEAP) collimator at the axis of rotation. Sensitivity is calculated for arrays of slit‐slat and parallel‐hole collimated cameras, using the maximum number of cameras possible for each. Results: With focal length of 5.7 cm, detector width of 6.5 cm, and 15 cm radius of rotation (ROR), the slit‐slat array could contain twenty cameras for one ring, and forty cameras for two rings. A LEAP‐collimated system with 10 cm ROR could contain four cameras and would have a spatial resolution of 8.0 mm at the axis of rotation. To match this, the slit‐slat collimators would have slit widths of 2.2mm/1.8mm for first and second rows respectively, and slats designed for similar axial resolution. A single row of twenty slit‐slat collimated cameras would have a sensitivity of 8.66×10, −4photons transmitted per photon emitted, while a staggered array would have a sensitivity of 1.28×10, −3. The array of four LEAP‐collimated cameras would have a sensitivity of 6.48 ×10, −4. Conclusions: The single‐ ring configuration of cameras gives sensitivity 34% greater than the LEAP‐ collimated system, while the staggered array gives a 98% sensitivity increase. This doubling in sensitivity comes with a large increase in complexity. Further optimizations for the slit‐slat system are possible in both areas.