Roentgen (unit) absorbed dose in a wide range of matter. When measuring absorbed dose in a human due to external exposure, the SI unit the gray, or the related non-SI rad are used. From these can be developed the dose equivalents to consider biological effects from differing radiation types and target materials. These are equivalent dose, and effective dose for which the SI unit sievert or the non-SI rem are used. The following table shows radiation quantities in SI and non-SI units: Roentgen (unit) The roentgen or röntgen () (symbol R) is a legacy unit of measurement for the exposure of X-rays
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