Biomedical Engineering Reference
In-Depth Information
However, in spite of this obvious shortcoming, this technique has proved to be of tremen-
dous clinical value.
The most commonly used stationary detector system is the scintillation camera or
gamma camera. This device views all parts of the radiation field continuously and is there-
fore capable of operating almost like a camera—building up an image quickly. Initially
developed by Hal Anger in the late 1950s, the first Anger camera reflected the convergence
of the disciplines of nuclear physics, electronics, optics, and data processing in a clinical
setting. Its ultimate acceptance and further development have had a profound impact not
only on the practice of clinical nuclear medicine but on the entire diagnostic process as well.
The initial concepts introduced by Anger became basic to the art of imaging specific physi-
ological processes.
15.3.2 The Gamma Camera
The operation of the basic gamma camera is shown in Figure 15.5. The detector of the
gamma camera is placed over the organ to be scanned. In order to localize the radiation
from a given point in the organ and send it to an equivalent point on the detector, a colli-
mator is placed over the base of the scintillation crystal. Since gamma rays cannot be
“bent,” another technique must be used to selectively block those gamma rays that, if
allowed to continue on their straight-line path, would strike the detector at sites completely
unrelated to their points of origin in the subject. This process of selective interference is
accomplished by the collimator. To prevent unwanted off-axis gamma rays from striking
the crystal, collimators usually contain a large number of narrow parallel apertures made
of heavy-metal absorbers.
FIGURE 15.5
Basic elements of a gamma curve.
