Nuclear Medicine
Nuclear medicine uses short-lived isotopes to image specific body systems. It is a very sensitive modality as most pathological processes will affect cell function before structural changes are evident. The dose received for most studies is similar to many CT procedures. A technique is available to image every organ system in the body (please refer to the appropriate imaging pathways). Most investigations require the injection of the radioisotope either in its free form (eg. pertechnetate for thyroid, salivary or Meckel's scans, Thallium for cardiac or tumour imaging, Gallium for infection, inflammation or tumour imaging) or bound to cells (eg red and white blood cells) or to a chemical ligand that determines the organ of uptake.
The majority of studies are performed using Technetium as the radioactive source. This agent has physical properties that are optimal for detection by a gamma camera, a short half life (6 hours) which reduces the dose received by the patient compared with longer lived agents and can be chemically bound to a wide range of substances. A functional image is created by the concentration and distribution of the radioactive tracer within the target organ. Tomographic images (SPECT) can assist localization of activity within an organ. The distribution of the activity passing through an organ with time can be analysed mathematically to derive functional data such as half-clearance times, ejection fractions, and relative perfusion.
Nuclear medicine demonstrates the in-situ biochemical or physiological disturbances of disease. Although some patterns of tracer distribution are characteristic for certain disease processes most studies have low specificity and spatial resolution and may require other anatomical imaging techniques for further evaluation.
Last reviewed in May 2011.