What is a gamma camera ?
An imaging apparatus used to visualize the distribution of radionuclides within the body. The majority of gamma cameras in clinical use operate on the principle devised originally by H.O. Anger at the Donner Laboratory in Berkeley in 1956. Radiation emanating from the patient is detected by a single, large, circular NaI (Tl) scintillation crystal. An array of (37, 61 or 91) photomultiplier tubes detects the light quanta emitted by the crystal and converts their energies into electrical pulses. Associated electronic circuitry determines the x, y coordinates of each scintillation event, the outputs of all the tubes being summed to provide a z pulse, the amplitude of which corresponds to the total energy of the scintillation event. The distribution of radioactivity is usually displayed on an oscilloscope. For quantitative analysis, the gamma camera is connected to a dedicated microcomputer, radioactive distributions being displayed either on a monochrome TC monitor as a gray scale range o
