9
Gamma Cameras
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The principles of nuclear medicine studies are based on the assessment of
radionuclidic distribution in different parts of a given organ after in vivo
administration of a radiopharmaceutical to distinguish between the normal
and abnormal tissues. Such assessment of radionuclide distribution is per-
formed by gamma cameras that primarily comprise NaI(Tl) detectors and
the associated electronics described in the previous chapter. The gamma
cameras permit the dynamic acquisition of the images with better spatial
resolution, and can be oriented in any direction around the patient. Various
aspects of gamma cameras are discussed below.
Gamma Cameras
The gamma or scintillation camera is an imaging device that is most com-
monly used in nuclear medicine. It is also called the Anger camera in honor
of Hal O. Anger, who invented it in the late 1950s. Gamma cameras detect
radiation from the entire field of view simultaneously and therefore are
capable of recording dynamic as well as static images of the area of inter-
est in the patient. Various designs of gamma cameras have been proposed
and made available, but the Anger camera with a single crystal is by far the
most widely used. Although many sophisticated improvements have been
made on the gamma cameras over the years, the basic principles of the oper-
ation have essentially remained the same.
Principles of Operation
The gamma camera usually consists of several components: a detector, a
collimator, PM tubes, a preamplifier, an amplifier, a pulsed-height analyzer
(PHA), an X-,Y-positioning circuit, and a display or recording device. A
schematic diagram of a gamma camera is illustrated in Figure 9.1, and a
commercial gamma camera is shown in Figure 9.2. The detector, PM tubes,
and amplifiers are housed in a unit called the detector head, which is