Image reconstruction for PET/CT scanners: past achievements and future challenges

Shan Tong, Adam M Alessio, Paul E Kinahan
2010 Imaging in Medicine  
PET imaging can measure the spatial distribution of active functional processes, such as glucose metabolism, in living tissue. The physics of PET imaging are discussed in detail elsewhere [5]. Here we briefly explain the data acquisition process. A functional compound is first labeled with a positron-emitting radioisotope. Then the labeled compound, called the radiotracer, is injected into the living subject and preferentially accumulates where the compound is metabolized. As the radioisotope
more » ... cays to a stable state, the emitted positron travels a short distance (typically <1 mm) and undergoes an annihilation, producing two annihilation photons. The photons travel in opposite directions along an approximately straight line, and can be detected outside the body by the PET scanner. If two photons are detected in a short time window (the prompt window), the detection is called a coincidence event. The parallelepiped joining the two detector elements is called a tube of response (Figure 1 ). In the absence of several confounding physical effects such as attenuation, the total number of coincidence events detected by the two detector elements will be proportional to the total amount of tracer contained in the tube of response. This is the key to PET imaging. Based on this relation, one can process the co incidence events to reconstruct the distribution of the labeled compounds. PET is a medical imaging modality with proven clinical value for disease diagnosis and treatment monitoring. The integration of PET and CT on modern scanners provides a synergy of the two imaging modalities. Through different mathematical algorithms, PET data can be reconstructed into the spatial distribution of the injected radiotracer. With dynamic imaging, kinetic parameters of specific biological processes can also be determined. Numerous efforts have been devoted to the development of PET image reconstruction methods over the last four decades, encompassing analytic and iterative reconstruction methods. This article provides an overview of the commonly used methods. Current challenges in PET image reconstruction include more accurate quantitation, TOF imaging, system modeling, motion correction and dynamic reconstruction. Advances in these aspects could enhance the use of PET/CT imaging in patient care and in clinical research studies of pathophysiology and therapeutic interventions. kEywords: analytic reconstruction fully 3d imaging iterative reconstruction maximum-likelihood expectation-maximization method PET
doi:10.2217/iim.10.49 pmid:21339831 pmcid:PMC3039307 fatcat:vzerxjghungkfb4fiwidyij3la