gammacameras

A gamma camera, also known as a scintillation camera, is a nuclear medicine imaging device used to visualize the distribution of gamma-emitting radiopharmaceuticals within a patient. It detects gamma photons emitted by a radiotracer injected or ingested by the patient and converts those photons into images that reflect physiological and biochemical processes.

The core components are a large sodium iodide crystal doped with thallium (NaI(Tl)), a set of photomultiplier tubes or solid-state photodetectors that convert scintillation light into electrical signals, and electronics for signal processing. A collimator of lead or tungsten shapes the direction of incoming photons, enabling spatial localization but reducing sensitivity. The camera produces planar images and, with multiple detectors or rotating configurations, can perform single-photon emission computed tomography (SPECT) to create three-dimensional reconstructions.

Common radiopharmaceuticals include Technetium-99m compounds (the most widely used due to favorable half-life and gamma energy, typically around 140 keV), Iodine-123, Thallium-201, Indium-111, and Gallium-67. Planar imaging provides static or dynamic images, while SPECT adds tomographic detail for more precise localization.

Historically developed in the 1950s by Hal Anger, gamma cameras revolutionized diagnostic nuclear medicine and remain a standard tool for bone, cardiac, renal, thyroid, and oncologic imaging. Modern systems may feature multiple detectors and advanced electronics; newer solid-state detectors (e.g., CZT) are increasingly used. Gamma cameras are distinct from PET scanners, which detect coincidence photons from positron annihilation and operate at higher energies.