What imaging method uses radioactive agents to visualize biological processes in vivo?

Positron emission tomography (PET) is an imaging method that utilizes radioactive agents, known as radiotracers, to visualize biological processes within a living organism. This technique is distinct because it detects gamma rays emitted indirectly by the radiotracers as they accumulate in areas of high metabolic activity, which is commonly found in various tissues, including tumors.

The design of PET allows for dynamic imaging of physiological functions, such as blood flow, oxygen intake, and glucose metabolism, making it particularly valuable in oncology, cardiology, and neurobiology. The ability to assess these metabolic functions is what sets PET apart from other imaging techniques, as it offers insights into not just the morphology of tissues, but also their functional status.

In contrast, X-ray imaging primarily captures structural information about bones and certain fluids, magnetic resonance imaging provides detailed images of soft tissues based on magnetic properties, and computed tomography combines X-ray technology with computer processing to create cross-sectional images. None of these methods utilize radioactive agents in the same manner as PET does to visualize biological processes in vivo.