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
Ludwig Wilhelm Sachs "Geheimen Medizinalrat" (private medical advisor). Ludwig Wilhelm Sachs Ludwig Wilhelm Sachs (29 December 1787 in Groß-Glogau – 17 June 1848 in Königsberg) was a German physician. From 1807 studied medicine at the universities of Königsberg, Berlin and Göttingen, receiving his doctorate at the latter institution with the dissertation-thesis ""De Humorum corporis animalis vi vitali"" (1812). He later served as a physician in war-time hospitals in Königsberg, and in 1816 obtained his habilitation. In 1818 he became an associate professor at Königsberg, followed by a full professorship in 1826. In 1832 he was named director of the medical clinic, then in