Which of these procedures utilizes X-rays?

The procedure that utilizes X-rays is a CT scan. This imaging technique combines multiple X-ray images taken from different angles and uses computer processing to create cross-sectional images of bones, blood vessels, and soft tissues inside the body. CT scans are particularly useful in identifying conditions like tumors, internal injuries, and various diseases due to their ability to provide detailed images of internal structures.

In contrast, MRI uses strong magnetic fields and radio waves to produce detailed images, while ultrasound uses high-frequency sound waves to visualize soft tissues and organs. A PET scan involves the use of radioactive substances to observe metabolic processes in the body but does not rely on X-ray technology. Therefore, the CT scan is the correct choice as it explicitly employs X-ray technology in its imaging process.