projection radiography external source ultrasound reflection, refraction endoscopy photography videography drawing

Figure 1. The wide spectrum of macroscopic medical imaging techniques (courtesy of Prof. F. Deconinck, Vrije University, Belgium).

for detecting emitted annihilation photons. Consequently, the sensitivity of PET per disintegration, with comparable axial fields of view, is two orders of magnitude greater than that of SPECT. PET also benefits by detecting radiopharmaceuticals that have short physical half-lives and high specific activities, which enable clinical and research studies to be performed at low radiation doses and with low molecular concentrations of the tracer.

Both the academic community and the nuclear medicine industry maintain a continuous learning cycle and assessment of products quality to advance the technology and the operational capabilities of both SPECT and PET cameras. As PET has become integrated into clinical practice, several design trends have developed; with systems now available with a spectrum of features, from those designed for "low cost'' clinical applications to others designed specifically for very high-resolution research applications. There also is a continual upward revision and refinement in both hardware and software components for all of these systems. The development of dual-modality imaging systems is an emerging research field (see chapter 2) and now offers unique capabilities for the medical imaging community and biomedical researchers. In this chapter, the physical principles, basic features and performance parameters of nuclear medicine instrumentation are outlined, and some of the practical issues involved in optimizing the design aspects discussed.

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