Iterative CT reconstruction using LabPET™ detector modules

A computed tomography (CT) simulator has been built using the LabPET™ detectors and front-end electronics. Acquisitions of energy-binned data sets were made using this low spatial resolution CT system in photon counting mode. To retrieve maximum accuracy out of these acquisitions, an iterative reconstruction library was developed and tested. Construction of the system matrix is based on a preliminary raster scan from which the experimental detector response is obtained. A meticulous description of the system geometry and misalignment corrections is imperative and must be incorporated into the matrix definition to achieve good image quality. Using this method, no sinogram pre-correction or interpolation is necessary and measured projections can be used as raw input data for the iterative reconstruction algorithm. CT and fused PET/CT images show that LabPET™ detectors can be successfully used as individual X-ray photon counting devices for low-dose CT imaging of the anatomy in a molecular PET imaging context.