Topics and Speakers Ronald L. Van Heertum, MD
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Synopsis
In this lecture, Dr Ronald L. Van Heertum provides an in-depth examination of the past, present and future of PET [positron emission tomography] imaging–how it has evolved, what clinical applications PET offers today, and what future advances lie ahead.
The fundamental concept of PET scanning is to inject a tracer that will localize in a specific way in the body according to the physiologic characteristics of the tracer. Van Heertum focuses on one principal tracer, fluorine deoxyglucose, a sugar analog. The PET scanner is an apparatus with 12 rings and roughly 1,000 detectors which swing around the patient. Although PET imaging originally examined blood flow, functional MR has now gained dominance in that field. PET has increasingly focused on neural receptor activity. The key goal of these studies is to discern receptor activity and quantitate its change over time.
PET can be combined with MR and CT for a comprehensive evaluation of patients. Indeed, throughout his lecture, Dr Van Heertum asserts that there is a growing symbiosis between various imaging techniques, such as CT and MR. When employed in conjunction with PET, these imaging techniques offer an alternative vision of the brain that complements that of PET.
After reviewing the fundamentals of PET scanning, Dr Van Heertum turns to the clinical applications of this technology, noting that it is no longer simply a research tool. Rather, PET enables clinicians to diagnosis conditions such as dementia and brain tumors long before was previously possible.
Dementia can exist subclinically for more than 10 years. Given this long course, early diagnosis offers many benefits that go beyond simply offering patients the chance to receive treatment earlier. Early detection also helps to reduce anxiety for both patient and family and allow the patients to make plans while still cognitively intact. Such early detection and diagnosis extends the hope of developing preventive measures to forestall the development of dementias. Pharmaceutical companies developing treatments for dementia can use PET scanning to evaluate the effectiveness of new compounds by measuring their physiological effects.
One major clinical application of PET is differential diagnosis between types of dementias. Van Heertum discusses how to use PET to distinguish between dementias such as Alzheimer's disease, Parkinson's disease, frontotemporal dementia, Creutzfeldt-Jacob disease, and supranuclear palsy. Each of these dementias has signature patterns of anatomic and physiologic changes that PET, often combined with CT, can detect.
Brain tumors can also be studied with PET scanning. Recent studies have shown that glucose metabolism is a great predictor of the degree of brain tumor malignancy. The higher the malignant grade, the more glucose activity will be present. Therefore, analyzing glucose uptake with PET offers a better prognosis than offering simply a histologic grade of the tumor. PET aids in predicting progression to a higher grade of malignancy and for differentiating radiation necrosis from viable tumors.
