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.
PET images (MIP 0-60 min) of three Cynomolgus monkeys. Strong signals are detected at the sites where inserted catheters had roughened surfaces. Almost no other background signal is visible. Only accumulation in the gallbladder becomes visible at the bottom of the image. Credit: Piramal Imaging GmbH, Berlin Germany.
Note the high uptake of Ga-68-pentixafor on multi-planar reconstructions in the organs expressing CXCR4 such as the spleen (red arrows) and adrenal glands (yellow arrows), which was nearly completely blocked by the pre-injection of AMD 3100, a potent CXCR4 inhibitor. Strong accumulation of Ga-68-pentixafor was also found in the kidneys (asterisks) reflecting the renal clearance of the tracer. In addition, high, focal activities were detected in the abdominal aorta (red arrowheads) and right carotid artery (orange arrowheads) of atherosclerotic rabbits, whereas no significant signal could be detected in the non-injured left carotid artery (white arrowheads) of atherosclerotic and control rabbits, as well as in the abdominal aorta and right carotid artery of control rabbits. Furthermore, focal activities detected with PET in atherosclerotic plaques of the abdominal aorta and the right carotid artery decreased significantly when the same rabbit was re-imaged after blocking CXCR4 receptors. Image courtesy of Fabien Hyafil, M.D., Ph.D., Department of Nuclear Medicine, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany
Application of dual-modality optical and PET/CT activity-based probe in experimental carotid inflammation model. Coronal noninvasive PET/CT scans of (A) healthy and (B) diseased mice with and without ligated carotid arteries respectively. Inset images show optical ex vivo florescence imagining of (A) healthy and (B) diseased carotid arteries. PET/CT and optical images courtesy of Xiaowei Ma, Toshinobu Saito and Nimali Withana.