Which imaging modality uses gamma rays emitted by Tc-99m?

• A. X-Ray Imaging
• B. CT Scanning
• C. PET Scanning
• D. SPECT Imaging

Answer: (D)

The correct answer is SPECT Imaging because this modality specifically utilizes gamma rays emitted from radiopharmaceuticals like Technetium-99m (Tc-99m) to create images of the body's internal structures. Tc-99m is a widely used radioactive isotope in nuclear medicine due to its ideal physical properties, including a half-life of approximately six hours and the emission of gamma rays that are suitable for detecting with gamma cameras.

In SPECT (Single Photon Emission Computed Tomography), a gamma camera captures the gamma rays emitted from Tc-99m after it has been administered to the patient. The data collected forms three-dimensional images of the distribution of the radioactivity within the body, allowing for functional imaging of organs and tissues, particularly beneficial in assessing conditions such as heart disease and cancer.

In contrast, X-ray Imaging and CT Scanning rely on X-rays, not gamma rays, for creating images, while PET Scanning utilizes positron emission rather than gamma ray emission from Tc-99m. Therefore, SPECT Imaging is uniquely designed to take advantage of the properties of gamma rays from isotopes like Tc-99m, making it the correct choice in this context.