gammacamera

A gamma camera, also known as a scintillation camera, is a device used in nuclear medicine to image the spatial distribution of gamma-emitting radiopharmaceuticals within a patient's body. It detects gamma photons emitted by administered radiotracers and forms two-dimensional images that reflect physiological processes such as metabolism, perfusion, or receptor binding.

Most gamma cameras employ a large thallium-doped sodium iodide NaI(Tl) scintillation crystal coupled to an array of photomultiplier tubes or, in modern systems, solid-state photodetectors. When a gamma photon interacts in the crystal, it produces a brief flash of visible light. The light is collected and converted into electrical signals, whose amplitudes indicate energy and whose relative distribution is used to estimate the photon’s incidence position. A collimator, typically parallel-hole or pinhole, restricts detected photons to those traveling in preferred directions, trading off resolution and sensitivity.

Data from many detected events are processed to form an image. The Anger camera is a common design that uses the light distribution seen by the PMT array to estimate event position. Planar gamma cameras acquire two-dimensional images, while rotating gamma cameras or multiple detectors enable single-photon emission computed tomography (SPECT) for three-dimensional reconstruction. Energy discrimination helps reduce scatter by accepting photons within a selected energy window.

Clinical use centers on imaging with radiopharmaceuticals such as Technetium-99m compounds, Iodine-123 or Iodine-131, Thallium-201, and others for applications including bone, myocardial perfusion, thyroid, and whole-body scans.

The gamma camera was developed in the late 1950s by Hal O. Anger, whose design laid the foundation for modern nuclear medicine imaging and remains foundational, though advanced detectors and SPECT/CT integrations have expanded capabilities.