Freund was a professor of radiology at the Medical University of Vienna and is considered the founder of medical radiology and radiotherapy. He is the first physician known to have used ionizing radiation for therapeutic purposes. In 1896, a year after the discovery of X-rays by Wilhelm Röntgen and in same year that Antoine Henri Becquerel discovered radioactivity, Freund successfully treated a five year old patient in Vienna suffering from hairy moles covering her whole back. The case was published by the girl's local physician, Schiff, in 1901. In 1903, he published the first textbook on radiation therapy.
Freund also published fundamental work on the treatment occupational diseases with light and on the use of X-rays for testing construction materials.
Freund, who was a Jew, emigrated in 1938 to Belgium, following the annexation of Austria by Nazi Germany.
- "Historical essentials influencing the development of radiooncology in the past 100 years", Cellular and Molecular Life Sciences, 51,7, p. 681 (1995)
- Grundriß der gesamten Radiotherapie für praktische Ärzte,Berlin, Urban & Schwarzenberg, 1903. 423 pages, with illustrations, 1 Table.
- Leopold Freund (in German), in: Judith Bauer-Merinsky: Die Auswirkungen der Annexion Österreichs durch das Deutsche Reich auf die medizinische Fakultät der Universität Wien im Jahre 1938: Biographien entlassener Professoren und Dozenten. Wien: Diss., 1980, S. 59-61b. PDF