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December 1934


Author Affiliations


From the Department of Dermatology and Syphilology, New York Post-Graduate Medical School and Hospital, Columbia University.

Arch Derm Syphilol. 1934;30(6):761-771. doi:10.1001/archderm.1934.01460180003001

The necessity for a unit of measurement of roentgen dosage was realized soon after roentgen rays were used therapeutically. The many methods and instruments that have been used for measuring the intensity and quality of radiation are well known. The most accurate method of measuring intensity is by the ionization of air, while spectrometry offers the most accurate means of measuring the quality of x-radiation.1

In 1908, Villard2 described a unit of x-radiation based on the ionization of air. Additional units of x-radiation based on ionization have been described by Friedrich and Kroenig,3 Duane,4 Behnken5 and Solomon.6 In 1928 the international unit of radiation, the roentgen (r), was defined by the International X-Ray Unit Committee7 and accepted by the International Congress of Radiology. The roentgen was defined as the quantity of x-radiation which when the secondary electrons are fully utilized and the wall