What is a PET scan primarily used for in medical examinations?

A PET scan, or Positron Emission Tomography scan, is primarily utilized to assess cellular activity and metabolic processes in various tissues throughout the body. This imaging technique allows healthcare providers to observe how well certain cells are functioning by measuring their ability to absorb a radioactive tracer that is injected into the body. This process highlights specific body parts where metabolic activity is occurring, enabling the detection of diseases such as cancer, as tumors often show increased cellular uptake compared to normal tissues.

This capability makes PET scans particularly valuable in diagnosing and monitoring conditions, rather than just visualizing structural anomalies or measuring physiological parameters. Other imaging modalities, such as X-rays or MRIs, are more focused on visualizing organ structures or assessing sizes, while techniques like pulmonary function tests are used for measuring lung capacity. Therefore, while other choices describe important medical assessments, they do not capture the primary purpose of a PET scan as effectively as determining cellular uptake in specific body regions.