Imaging characteristics of a high resolution cone beam collimator

Single-photon-emission computed tomography (SPECT) using cone-beam geometry requires accurately built collimators and an appropriate reconstruction algorithm. The authors have investigated the imaging characteristics of a cast, high-resolution, cone-beam collimator and have compared its measured sensitivity and resolution with analytically predicted values. Using a filtered back-projection algorithm, they have measured point-spread functions at several locations within the field of view. Measurements have been made both with the collimator surface parallel to the axis-of-rotation (AOR) and with the surface tilted at an angle of 20 degrees with respect to the AOR. Although the SPECT point-spread response is not completely shift-invariant, high-quality cone-beam images of a brain phantom have been obtained. The measured performance of the collimator agrees well with analytically derived results.<>