Roentgen (unit) this derivative quantity the roentgen equivalent physical (rep) to distinguish it from the ICR roentgen. The introduction of the roentgen measurement unit, which relied upon measuring the ionisation of air, replaced earlier less accurate practices that relied on timed exposure, film exposure, or fluorescence. This led the way to setting exposure limits,and the National Council on Radiation Protection and Measurements of the United States established the first formal dose limit in 1931 as 0.1 roentgen per day. The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection (ICRP) soon followed with a limit of
Wilhelm Alexander Freund Wilhelm Alexander Freund Wilhelm Alexander Freund (August 26, 1833 - December 24, 1917) was a German gynecologist who was a native of Krappitz, Silesia. Born into a Jewish family, in 1855 he earned his medical degree at the University of Breslau, afterwards practicing gynecology in the same city. In 1874 he became an associate professor at Breslau. In 1879 he relocated to Strasbourg, where he served as a professor of gynecology and obstetrics. He died in Berlin. In January 1878, Freund performed the first abdominal extirpation of a cancerous uterus. Twenty years later in 1898, Austrian gynecologist Ernst Wertheim (1864-1920)