Positron emission tomography (PET) is a nuclear imaging technology (also referred to as molecular imaging) that enables visualization of metabolic processes in the body. The basics of PET imaging is that the technique detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (also called radiopharmaceuticals, radionuclides or radiotracer). The tracer is injected into a vein on a biologically active molecule, usually a sugar that is used for cellular energy. PET systems have sensitive detector panels to capture gamma ray emissions from inside the body and use software to plot to triangulate the source of the emissions, creating 3-D computed tomography images of the tracer concentrations within the body.
A PET-CT head and neck cancer scan showing various image reconstructions. The top left image is the separate CT scan showing the anatomy. The top right scan shows the fused PET and CT scans with false color added to help interpret the image. The bottom left scan is an initial FDG PET image showing tracer hot spots in the neck and a lymph node in the right jaw due to cancer. The right bottom image is a delayed enhancement scan showing tracer uptake over time, with normal hot spots in the bladder, kidneys, testicles and brain, which normally have higher metabolic activity. The low-grade gray shading of the anatomy is due to the normal cellular metabolism uptake of the FDG throughout the body.
This figure shows brain glucose metabolism as evidenced by positron emission tomography with [18F]-fluorodeoxyglucose (PET-FDG) at rest in patients with chronic disorders of consciousness (vegetative state and minimally conscious patients) and fully conscious control subjects. Please notice the dramatic drop in brain glucose metabolism from full consciousness to the minimal conscious and persistent vegetative states. Image courtesy of Stender et al.
A study using a new PET imaging agent shows that measures of tau protein in the brain more closely track cognitive decline due to Alzheimer's disease compared with long-studied measures of amyloid beta. More red color indicates more tau protein. The image on the left shows the average tau accumulation in the brains of cognitively normal people, averaged over many individuals. The image on the right shows the average amount of tau buildup in the brains of multiple people with mild Alzheimer's symptoms. Scanning multiple individuals shows that the intensity of tau deposits correlates with the severity of cognitive dysfunction. Image courtesy of Matthew R. Brier.
Early detection of cancer lesions with the latest generation of PET/CT scanners supports improved patient management. Yet much of PET’s potential, particularly for following patients and as a component in PET/MR, remains unrealized. (Image courtesy of Siemens Healthcare and the University of Tennessee, Knoxville)