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Computation of energy imparted in diagnostic radiology
Author(s) -
Gkanatsios Nikolaos A.,
Huda Walter
Publication year - 1997
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 - 10.1118/1.597939
Subject(s) - imaging phantom , monte carlo method , materials science , beam (structure) , voltage , waveform , nuclear medicine , physics , optics , biomedical engineering , medicine , mathematics , statistics , quantum mechanics
Energy imparted is a measure of the total ionizing energy deposited in the patient during a radiologic examination and may be used to quantify the patient dose in diagnostic radiology. Values of the energy imparted per unit exposure‐area product, ω ( z ) , absorbed by a semi‐infinite water phantom with a thickness z , were computed for x‐ray spectra with peak x‐ray tube voltages ranging from 50–140 kV and with added filtration, ranging from 1–6 mm aluminum. For a given phantom thickness and peak x‐ray tube voltage, the energy imparted was found to be directly proportional to the x‐ray beam half‐value layer (HVL) expressed in millimeters of aluminum. Values of ω ( z ) were generated for constant waveform x‐ray tube voltages and an anode angle of 12°, and were fitted to the expression ω ( z ) = α × HVL + β . Fitted a and β parameters are provided that permit the energy imparted to be determined for any combination of tube voltage, half‐value layer, and phantom thickness from the product of the entrance skin exposure (free‐in‐air) and the corresponding x‐ray beam area. The results obtained using our method for calculating energy imparted were compared with values of energy imparted determined using Monte Carlo techniques and anthropomorphic phantoms for a range of diagnostic examinations. At 60, 80, and 120 kV, absolute values of energy imparted obtained using our method differed by 8%, 10%, and 12%, respectively, from the corresponding results of Monte Carlo computations obtained for an anthropomorphic phantom. The method described in this paper permits a simple determination of energy imparted for any type of diagnostic x‐ray examination which may be used to compare the radiologic risks from differing types of x‐ray examinations, optimize imaging techniques with respect to the patient dose, or estimate the patient effective dose equivalent.