What type of radiation is primarily used during diagnostic imaging?

Diagnostic imaging primarily utilizes ionizing radiation, which encompasses a range of radiation types, including X-rays and gamma rays. Ionizing radiation possesses enough energy to remove tightly bound electrons from atoms, thus creating ions. This property makes it particularly effective in medical imaging because it can penetrate body tissues and produce images of internal structures such as bones and organs.

While gamma radiation, which is a type of ionizing radiation, is indeed used in some imaging modalities (like nuclear medicine), the term "ionizing radiation" encompasses a broader category that includes both X-rays and gamma rays. X-rays are the main form of ionizing radiation used in common diagnostic procedures such as X-ray imaging and CT scans. By recognizing that ionizing radiation is the overarching term that includes these techniques, it becomes clear why this would be the correct answer.