- Positron Emission Tomography (PET) is a sophisticated nuclear imaging technique that provides functional information about biological processes in the body, unlike conventional imaging methods that primarily show anatomical structures. By visualizing the metabolic activity of tissues and organs in real time, PET is especially valuable in the diagnosis, staging, and monitoring of diseases, particularly in oncology, neurology, and cardiology. It is often used in conjunction with CT (PET/CT) or MRI (PET/MRI) to correlate metabolic data with precise anatomical detail.
- PET imaging works by introducing radioactive tracers, known as radiopharmaceuticals, into the body—most commonly fluorodeoxyglucose (FDG), a glucose analog labeled with the positron-emitting isotope fluorine-18 (¹⁸F). Because many diseases—especially cancers—display increased metabolic activity, FDG accumulates more in affected tissues. As the radioactive tracer decays, it emits positrons that collide with electrons in the body, producing gamma rays that are detected by the PET scanner. This data is used to reconstruct detailed images of metabolic activity across different tissues.
- In oncology, PET scans are widely used to detect, stage, and monitor cancers by identifying areas of increased glucose metabolism. This helps differentiate between benign and malignant tumors, assess treatment response, and detect metastasis or recurrence. For example, PET is integral in managing lymphomas, lung cancer, colorectal cancer, and melanoma.
- In neurology, PET is used to study the brain’s metabolic patterns and neurotransmitter systems. It aids in the diagnosis and understanding of neurodegenerative diseases like Alzheimer’s disease, where decreased glucose uptake in specific brain regions can be visualized. It is also used to investigate epileptic foci, Parkinson’s disease, and various psychiatric disorders, providing insight into the functional changes that accompany these conditions.
- In cardiology, PET imaging evaluates myocardial perfusion and viability, helping distinguish between damaged but viable heart tissue and irreversibly scarred tissue in patients with coronary artery disease. This is critical in determining whether revascularization procedures, such as bypass surgery or angioplasty, will be beneficial.
- PET imaging has expanded to include a wide range of radiotracers that target specific biological pathways. For instance, choline PET is used for prostate cancer, amyloid and tau PET for Alzheimer’s research, and dopamine PET for studying movement disorders. The development of new tracers continues to broaden PET’s clinical and research applications.
- While PET scans are extremely informative, they have some limitations. They involve exposure to ionizing radiation, though typically at safe levels, and are more expensive and less widely available than other imaging modalities. Additionally, the short half-lives of many PET tracers require onsite or nearby cyclotrons and radiopharmacies, making the technology resource-intensive. The procedure also requires the patient to remain still for a period of time, and fasting is often necessary prior to the scan to optimize tracer uptake.
