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 backprojection algorithm, the authors 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 also 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