Recent advances in emission computed tomography

Recent advances in emission computed tomography include those in position emission tomography (PET) and single-photon emission computed tomography (SPECT). Despite its high instrumentation costs, PET is unique among other modalities in its ability for metabolic and physiological imaging. After more than two decades of intensive instrumentation development and application, PET is entering a new era with an increased number of commercial systems and hospital-based cyclotrons being installed in clinical departments. Future research is directed towards high resolution PET imaging systems, pharmaceutical development and exploration of new areas of clinical applications. Due to lower instrumentation costs, SPECT systems are much more widely available than PET. On the other hand, SPECT's limitations include lower sensitivity, difficulties in attenuation and scatter compensation, and availability of truly metabolic and physiological agents. However, in the last few years we have witnessed tremendous advances made in SPECT imaging. In particular, SPECT systems with multiple detectors are now commercially available, offering much better sensitivity and spatial resolution compared to older generation systems and the potential of simultaneous transmission-emission computed tomography. Image processing and reconstruction methods are being developed to provide better image quality and quantitative accuracy. New SPECT radiopharmaceuticals for metabolic and physiological studies are under investigation. These advances will provide an alternative to metabolic and physiological imaging at much lower costs. The paper highlights recent advances in both PET and SPECT and their effects on the future of medical imaging.