Biomedical Engineering Reference
In-Depth Information
cause a voltage drop,
V
. The amount of lost charge
Q
, which depends on the
energy absorbed, is directly proportional to the measured voltage change:
Q
=
CV
. Calibrated self-reading pocket ionization chambers, like that in Fig. 10.6, are
still in use.
Proportional counters can be used to detect different kinds of radiation and, un-
der suitable conditions, to measure radiation dose (Chapter 12). A variety of gases,
pressures, and tube configurations are employed, depending on the intended pur-
poses. The instrument shown in Fig. 10.7 uses a sealed gas proportional-counter
(a)
(b)
Fig. 10.6
(a) Direct-reading, condenser-type pocket ionization
chamber. Amount of exposure to X and gamma radiation can
be read on calibrated scale through eyepiece. (b) Charger uses
standard D battery. (Courtesy Arrow-Tech, Inc.)
Fig. 10.7
Proportional-counter monitor for measuring dose and
dose rate. See text. (Courtesy Berthold Technologies USA, LLC.)
