Advances in SPECT and PET

The major developments in SPECT (single-photon-emission computed tomography) and PET (positron-emission tomography) are reviewed, and the near-term objectives for further developments are discussed. SPECT tomographs consisting of rotating Anger cameras are improved through the use of fan-beam, cone-beam, and astigmatic collimators. At the same time dedicated SPECT tomographs using cylindrical stationary-detector geometry are being developed as an alternative. Whether they will find widespread use is considered to depend largely on the clinical utility of SPECT imaging and on the development of radiopharmaceuticals. PET tomographs continue to improve in spatial resolution, aided by the use of detector encoding schemes that reduce the number of photomultipliers relative to the number of scintillation crystals. This improved resolution must be combined with higher sensitivity in order to take full advantage of the improved resolution. High sensitivity can be achieved by using a large axial acceptance angle. It is noted that similarities between the two modalities are increasing both in detector development (especially for stationary systems) and reconstruction algorithms (particularly in true three-dimensional reconstructions), suggesting that an awareness of both fields will be needed to enhance the development of each one.<>