Gamma-ray imaging using a CdZnTe pixel array and a high-resolution, parallel-hole collimator

The poor performance of current parallel-hole collimators is an impediment to planar high-resolution gamma-ray imaging, even when high-resolution semiconductor detector arrays are available. High-resolution parallel-hole collimators are possible but have not been fabricated because conventional collimator construction techniques severely limit achievable bore size and septal thickness. We describe development and testing of a high-resolution collimator with 4096 260-μm square bores and 380 μ-m pitch, matched to our existing 2.5 cm×2.5 cm hybrid 64×64 CdZnTe arrays with multiplexer readout. The collimator is a laminar composite of about 100 layers of W sheets produced by photolithography and has an efficiency of 5×10 ^-5. We have demonstrated sub-millimeter spatial resolution at 140 keV in both phantom and animal imaging using this system. We present images of resolved individual vertebrae in the spine of a mouse and lymphatic channels and nodes in a rat. The collimator and semiconductor array could form a compact module for use in a wide variety of gamma-ray imaging systems