A Calorimetric Method Used in the Dosimetry of X-Ray Beams from a 1 Million Volt Generator

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Abstract
Construction of lead calorimeters and associated apparatus used to measure the putput of X-rays from a 1 million volt generator are described. The calorimetric measurements were compared with ionization measurements in terms of roentgens. The value obtained for the filtered X-ray beam, as used clinically, was 2895 ergs/cm2 per roentgen. The X-ray spectrum of the beam was determined from measurements of transmission through various absorbers. This spectrum was used to calculate the expected value in ergs/cm2 per roentgen and this agreed reasonably well with the measured value. Finally, the energy absorption of an X-ray beam in water was followed by ionization measurements in a large water tank. From these a value of 94.9 [plus or minus] 3 ergs per g per roentgen was obtained.