The correlation of the epilation dose used in the treatment of tinea capitis with the roentgen as a unit has been under study for the past five years at the Massachusetts General Hospital. The term "roentgen," designated by "r," was adopted as the international unit of measurement of roentgen radiation at the Second International Congress of Radiology in 1928.1 The roentgen was defined as the quantity of roentgen radiation which when secondary electrons are fully utilized and the effect of the wall chamber is avoided produces in 1 cc. of air under normal conditions (at 0 C. and 76 cm. of mercury pressure) such a degree of conductivity that one electrostatic unit of charge is measured at saturation current.
The adoption of this unit marked the creation of a unit of measurement capable of demonstration by physical means. At the same time, sufficient data have accumulated to indicate that
LANE CG, CRAWFORD GM. MEASUREMENT OF ROENTGEN THERAPY FOR TINEA CAPITIS: CORRELATION OF THE EPILATION DOSE WITH THE ROENTGEN. Arch Derm Syphilol. 1938;37(1):62–69. doi:10.1001/archderm.1938.01480070065008
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