Scintillating materials are used in a variety of medical imaging devices. This paper presents a description of four medical imaging modalities that make extensive use of scintillators: planar x-ray imaging, x-ray computed tomography (x-ray CT), SPECT (single photon emission computed tomography) and PET (positron emission tomography). The discussion concentrates on a description of the underlying physical principles by which the four modalities operate. The scintillator requirements for these systems are enumerated and the compromises that are made in order to maximize imaging performance utilizing existing scintillating materials are discussed, as is the potential for improving imaging performance by improving scintillator properties.

PET scanners based on LSO have the potential for significantly better coincidence timing resolution than the 6 ns fwhm typically achieved with BGO. This study analyzes the performance enhancements made possible by improved timing as a function of the coincidence time resolution. If 500 ps fwhm coincidence timing resolution can be achieved in a complete PET camera, the following four benefits can be realized for whole-body FDG imaging: 1) The random event rate can be reduced by using a narrower coincidence timing window, increasing the peak NECR by ~;50 percent. 2) Using time-of-flight in the reconstruction algorithm will reduce the noise variance by a factor of 5. 3) Emission and transmission data can be acquired simultaneously, reducing the total scan time. 4) Axial blurring can be reduced by using time-of-flight to determine the correct axial plane that each event originated from. While time-of-flight was extensively studied in the 1980's, practical factors limited its effectiveness at that time and little attention has been paid to timing in PET since then. As these potential improvements are substantial and the advent of LSO PET cameras gives us the means to obtain them without other sacrifices, efforts to improve PET timing should resume after their long dormancy.

The instrumentation used for the nuclear medical imaging technique of Positron Emission Tomography (PET) shares many features with the instrumentation used for electromagnetic calorimetry. Both fields can certainly benefit from technical advances in many common areas, and this paper discusses both the commonalties and the differences between the instrumentation needs for the two fields. The overall aim is to identify where synergistic development opportunities exist. While such opportunities exist in inorganic scintillators, photodetectors, amplification and readout electronics, and high-speed computing, it is important to recognize that while the requirements of the two fields are similar, they are not identical, and so it is unlikely that advances specific to one field can be transferred without modification to the other.

We explore the causes of performance limitation in positron emission mammography cameras. We compare two basic camera geometries containing the same volume of 511 keV photon detectors, one with a parallel plane geometry and another with a rectangular geometry. We find that both geometries have similar performance for the phantom imaged (in Monte Carlo simulation), even though the solid angle coverage of the rectangular camera is about 50 percent higher than the parallel plane camera. The reconstruction algorithm used significantly affects the resulting image; iterative methods significantly outperform the commonly used focal plane tomography. Finally, the characteristics of the tumor itself, specifically the absolute amount of radiotracer taken up by the tumor, will significantly affect the imaging performance.