In scintigraphy, which detector is used to detect radioactivity?

• A. Gamma camera
• B. Ultrasound transducer
• C. X-ray detector
• D. MRI coil

Answer: (A)

In scintigraphy, detecting the emitted radioactivity requires a detector that can pick up gamma rays from the radiopharmaceutical. A gamma camera is used for this purpose. It has a scintillation crystal (typically sodium iodide) that converts incoming gamma photons into light, and photomultiplier tubes that turn that light into electrical signals to create an image of tracer distribution. A collimator in front of the crystal helps determine the direction of the gamma rays, giving spatial information about where the tracer is concentrated. Common radiotracers, like technetium-99m compounds, emit gamma rays suitable for this detection. Ultrasound transducers detect sound waves, not radioactivity; X-ray detectors are for X-rays rather than gamma rays; MRI coils are used in magnetic resonance imaging.