Nuclear medicine at the crossroads.

Many nuclear medicine procedures, originally developed more than 20 years ago, are now performed with new radiopharmaceuticals or instruments; it is therefore apposite to reappraise what we are doing and why we are doing it. The clinical utility of nuclear medicine is discussed with reference, by way of example, to gated blood pools scans and myocardial perfusion imaging; the importance of the referred population for the outcome of studies is stressed. Attention is drawn to the likelihood that the detection of ischemia would be enhanced by the administration of nitroglycerin prior to rest thallium injection. Emphasis is also placed on the increasing acceptance of dual-tracer studies. The significance of expression of p-glycoprotein by some tumors for sestamibi imaging is discussed, and advances in respect of fluorodeoxyglucose imaging are reviewed. The final section covers issues relating to the development of new procedures, such as the value of nuclear medicine in the detection and characterization of tissue oxygen levels and the possible future role of nuclear medicine in the management of sleeping and eating disorders.