Which device located, measures, and amplifies gamma rays emitted from patients?

• A. SPECT cameras
• B. Gamma cameras
• C. PET scanners
• D. MRI machines

Answer: (B)

A gamma camera is the instrument designed to locate, measure, and amplify gamma rays emitted by radiopharmaceuticals in the patient. It sits near the patient and uses a large scintillation crystal (usually NaI(Tl)) to absorb incoming gamma photons and convert that energy into visible light. This light is then detected by an array of photomultiplier tubes that amplify the signal and convert it into electrical pulses, which are processed to form an image of where the radiotracer is distributed in the body. When the system rotates around the patient, this same detector setup becomes a SPECT camera, enabling 3D imaging, but the fundamental detection and amplification of gamma rays come from the gamma camera itself. PET scanners, MRI machines, and other modalities involve different principles (PET detects 511 keV photons in coincidence, MRI uses magnetic fields and does not detect gamma rays).