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Two thermal methods to measure the energy fluence of a brief exposure of diagnostic x rays
Author(s) -
Carvalho A. A.,
Mascarenhas S.,
dePaula M. H.,
Cameron J. R.
Publication year - 1992
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596912
Subject(s) - fluence , dosimeter , detector , optics , ionization chamber , materials science , amplifier , beam (structure) , particle detector , radiation , physics , optoelectronics , ionization , laser , ion , cmos , quantum mechanics
This paper describes two simple thermal methods for measuring the energy fluence in J/cm 2 from a diagnostic x‐ray exposure. Both detectors absorb essentially 100% of the radiation and give a signal that is directly proportional to the energy fluence of the x‐ray beam. One detector measures the thermal effect when a pulse of x rays is totally absorbed in the pyroelectric detector of lead–zirconium–titanate (PZT). The other detector measures the expansion of a gas surrounding a lead disk detector in a photoacoustic chamber. The increased pressure of the gas is transmitted through a 1‐mm duct to a sensitive microphone. Both detectors have previously been used to measure the energy fluence rate of continuous x‐ray beams in the same energy region using a chopped beam and a lock‐in amplifier. Measurement of the energy fluence of a pulse of radiation eliminates the need for the beam chopper and lock‐in amplifier and results in a simple, rugged, and inexpensive dosimeter. Either method can be combined with the area of the beam to give an estimate of the imparted energy to the patient from a diagnostic x‐ray exposure.