ESTIMATION OF AN X-RAY MACHINE’S WORKLOAD DURING ROUTINE RADIOLOGICAL EXAMINATIONS

Abstract

The X-ray machine workload (W) is defined as the integral of the anode current of the tube for a certain period of time. Information about the workload of an X-ray machine is needed in calculations of
the structural shielding in the X-ray rooms and in comparing the results of radiation monitoring, conducted in the X-ray rooms, with the permissible levels of doses to different categories of exposed persons. In the Russian Federation, the calculations of the structural shielding in the X-ray rooms are currently based on the conservative approach developed in the 1970s. This approach assumes that a very high value of workload, Wsum = 1000 mA×min×week-1, is used in the calculatons. Additionally to this conservative assumption, the maximum value of 100kV for the anode voltage is used. The aim of this study was to collect and analyze the information concerning real workload values of the X-ray machines placed in the routine rooms. The total values of the weekly workload and its distribution as a function of the tube voltage were registered. The average and maximum values of workload among surveyed X-ray units were about 2–4 times lower than the value of 1000 mA×min×week-1 specified in the National sanitary norms SanPin2.6.1.1192-03. Demo calculations show that if one uses the actual distribution of medical procedures depending on the tube voltage instead of the single value of 100kV specified in the SanPiN2.6.1.1192-03, then the required thickness of the shielding construction in the X-ray rooms can be reduced with a factor of two.