Letter from the editors

Article Outline

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THIS SECOND ISSUE of the Seminars devoted to positron emission tomography (PET) has a mixture of clinically approved and emerging areas of PET application. Lymphoma, head and neck cancer, gastrointestinal cancer, and breast cancer all are widely recognized and important applications of PET at this time. Thyroid disease has achieved limited approval by governmental insurance agencies for reimbursement, but its role is becoming increasingly clarified and the importance of PET more generally acknowledged.

It is interesting to note that among the entities included in this Issue, the only non-Medicare-approved indication is the use of PET in patients with dementia. It is remarkable that one of the earliest applications of PET and the one that has provided some of the most dramatic understanding of the functioning of the human body still is not recognized as a clinical modality. The approved use of PET for patients with intractable epilepsy is very limited. However, PET in dementia, if it were approved, would present a marked increase in the number of PET procedures performed. One can question whether the reason for delaying approval for this application is based on its potential economic impact or on a real concern about its value. There is no question that if PET in dementia is approved, there will be a need for firmly established guidelines to prevent its overuse. It certainly is possible that any middle-aged or elderly person who is beginning to notice a little bit of forgetfulness will be requesting a PET study to be sure they do not have Alzheimer’s. Fortunately, the majority of individuals who have a small decline in mental faculties do not end up with severe, progressive disease. Because of the lack of specificity of the symptomatology, it will be particularly important to have PET available when an adequate therapeutic regimen is introduced.

Another issue that may be appreciated from a careful reading of the articles included here is the role of computed tomography (CT) in PET imaging. There is no question that the clinical interpretation of PET images is greatly enhanced by correlative CT or magnetic resonance imaging. Co-registration (fusion) has a further value because it allows the interpreter to more accurately correlate abnormal areas of activity with anatomic landmarks. Many investigators, including several of the authors in this Issue, suggest that the diagnostic capability of PET is greatly enhanced by the use of a PET/CT machine where PET and CT are in a single device. Although there is an increasing body of evidence supporting this opinion, a carefully controlled prospective study is still needed to analyze the various approaches to correlating PET and CT images in a blinded fashion. The situation is further complicated by the fact that manufacturers are moving to faster and faster CT machines in these PET/CT devices with 16-slice CTs rapidly becoming the state of the art. New developments attempting to improve PET resolution are beginning to strain the limits imposed by the physics of positron emission. Just 1 year ago, in July of 2003, we devoted a full issue to image fusion. A review of that issue, in comparison with some of the current articles, shows the many changes that have already occurred. The field is progressing so rapidly that it is likely that we will need to revisit image fusion in the near future.

The potential of nuclear medicine for change and progress seems to be without limits. Each year we find ourselves doing something new. PET and PET-CT are simply the latest advances to test our adaptability and clinical acumen.