What is the primary imaging principle behind SPECT?

• A. It uses X-rays to create images
• B. It detects sound waves for imaging
• C. It detects gamma radiation from radioactive tracers
• D. It generates images based on magnetic resonance

Answer: (C)

The primary imaging principle behind SPECT (Single Photon Emission Computed Tomography) relies on detecting gamma radiation emitted by radioactive tracers administered to a patient. In SPECT, radiopharmaceuticals labeled with isotopes such as Technetium-99m emit gamma rays as they decay. A gamma camera captures these emissions from multiple angles to reconstruct cross-sectional images of the organ or tissue being assessed.

This technique provides invaluable functional information about the biological processes occurring within the body. By mapping the distribution of the radiotracer, SPECT allows physicians to evaluate various conditions, such as heart disease or cancer, by rendering images that reflect physiological activity rather than just structural anatomy.

The other imaging principles mentioned, like using X-rays or sound waves, pertain to different imaging modalities such as CT or ultrasound. Magnetic resonance imaging (MRI) is a separate technology that focuses on magnetic fields and radio waves, which operate on entirely different principles than the gamma radiation used in SPECT.