SPECT (Single-Photon Emission Computed Tomography) is a nuclear medicine imaging technique which belongs to the branch of emission tomography. The non-invasive nature of the study is classified as functional method. In the process, the organs are labelled with radiopharmacon tracer substance. The substance is marked with a single-photon emitter, a radioisotope that emits one gamma photon with each radioactive decay event. The imaging hardware (Anger or gamma camera) begins detecting and recording gamma photons emitted by the radiopharmaceutical as a product of this radioactive decay. A gamma camera consists of a collimator, a flat scintillation crystal and an array of photomultiplier tubes. Gamma photons that successfully traverses the collimator are absorbed in the scintillator crystal and optical photons are produced. Then the optical photons are collected by the photomultiplier tubes (PMTs). A PMT can produce a cascade of electrons, which yields a measurable electrical current. Using image reconstruction techniques, the radioactive distribution in the organ under investigation will be created. Gamma photon attenuation and detector blurring results in serious distortions in the reconstructed images that should be corrected for.
The main goal of this work is to create an image reconstruction algorithm that corrects the geometrical distortions caused by the fanbeam collimator’s magnifying effect. The reconstruction algorithm has been extended with a PSF model for detector blurring compensation and with the effect of gamma photon attenuation for attenuation correction. The algorithm has been tested with GATE simulation of a mathematical phantom. The forward projection operator with detector blurring compensation of the fanbeam reconstruction algorithm has been implemented on GPU.