Calorimetric Measurement of the Energy Fluence of Diagnostic X-Ray Beams

A method for measurement of the energy fluence of diagnostic X-ray beams is described, using total absorption calorimetry. Optimization of the absorbing element is discussed quantitatively, and it is shown that a lead plate of 1 mm is as sensitive as gold or platinum absorbers. Using Styrofoam insulation, semiadiabatic conditions pertain during the measurement time of 2-6 s. Use of the method is illustrated in measurement of energy fluence corresponding to tube voltages of 55-115 kVp. The results are in good agreement with those obtained from X-ray energy spectrum data.