The measurement of energy imparted to patients during diagnostic x-ray examinations using the Diamentor exposure-area product meter

The mean energy imparted to the patient has been proposed as a practical quantity which may be useful for assessing somatic risk in x-ray diagnostic radiology. A technique is described for estimating energy imparted during most common x-ray examinations of the trunk or complete head from a measurement of exposure-area product conveniently provided by the Diamentor transmission ionisation chamber. The necessary energy imparted calibration for the Diamentor has been deduced from consideration of incident spectral energy fluence and Monte Carlo calculations of the fraction of total beam energy imparted to mathematical phantoms representing the patient. The relationship between energy imparted and exposure-area product depends primarily on the applied potential and total filtration of the x-ray beam, and to a lesser extent on voltage waveform and x-ray target angle. Direct measurements of energy imparted to an Alderson Rando phantom for a range of irradiation conditions provided an excellent verification of the technique developed. Using the energy imparted per exposure-area product factors presented, overall uncertainties of less than +or-15% and +or-20% should be possible for measurements of energy imparted during examinations of the trunk and head respectively using the Diamentor.