Physics and Radiobiology of Nuclear Medicine

Solid Scintillation Counters A basic solid scintillation counter consists of a scintillation detector, a PM tube, a preamplifier ...

The photocathode is usually an alloy of cesium and antimony that releases electrons after absorption of light photons. The PM tu ...

counting only those pulses falling within preselected voltage intervals or “channels” and rejects all others (see Fig. 8.1). Pul ...

Photopeak In an ideal situation, if the g-ray photon energy is absorbed by the photo- electric mechanism and each g-ray photon y ...

in pulse heights that are smaller than that of the photopeak. The Compton electrons, however, can have variable energies from ze ...

sition of electrons from the upper shells, mainly the Lshell, to the Kshell. The difference in binding energy between the K-shel ...

200 keV, the iodine escape peak would fall within the width of the photo- peak, because of the small differences between the two ...

detectors so that the likelihood of two photons striking the detector at the same time is reduced. In the case of high-activity ...

for counting. The primary fluors include 2,5-diphenyloxazole (PPO), 2,5- bis-2-(5-T-butyl-benzoxazolyl)-thiophene (BBOT), and p- ...

The readers are referred to reference physics books for details of these methods. A problem with liquid scintillation counting i ...

=8.3% The energy resolution depends on the photon energy. The higher the photon energy, the better the energy resolution (i.e., ...

from a radionuclide. Considering these factors, the overall counting effi- ciency of a counter for a radiation is given by the f ...

then only a fraction of all radiations emitted from the source will be detected by the detector. This fraction is determined by ...

When the source and the detector are in close contact, the fgtends to be about 50% (Fig. 8.9B). In the case of gamma well counte ...

Based on how successive pulses are processed owing to the dead time, the counting systems fall into two categories:paralyzablean ...

are paralyzable systems. Scintillation cameras have both paralyzable and nonparalyzable components of dead time. As can be seen ...

and 684 divisions, respectively, thus assigning the center of the photopeak at 662 divisions corresponding to the 662-keV g-ray. ...

absolute activity, the photopeak efficiency must be determined for each photon energy. When multiple g-rays, either from a singl ...

Well counters are available with automatic sample changers having pro- visions of counting as many as 500 samples. Most counters ...

brated for photon energies in the same manner as the well counter using the 662-keV g-ray energy of^137 Cs, and then discriminat ...