Roentgen (unit) One roentgen deposits of absorbed dose in dry air, or in soft tissue. One roentgen of X-rays may deposit anywhere from in bone depending on the beam energy. This tissue-dependent conversion from kerma to absorbed dose is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a reference medium, which is ambiguous in the latest NIST definition. The roentgen has its roots in the Villard unit defined in 1908 by the American Roentgen Ray Society as "the quantity of radiation which liberates by ionisation one esu of electricity per cm of air under normal conditions
Hugo Wilhelm von Ziemssen Hugo Wilhelm von Ziemssen Hugo (Wilhelm) von Ziemssen (13 December 1829 – 21 January 1902) was a German physician, born in Greifswald. He studied medicine at the universities of Greifswald, Berlin, and Würzburg. In 1863 he was called to the University of Erlangen as a professor of pathology and therapy as well as the director of the medical clinic. In 1874 he relocated to Munich as a professor and director of the general hospital. He made advances in electrotherapeutics, conducted research on cold-water treatment for typhoid fever and lung inflammation, and became an authority on diseases of the larynx and