Prof. Dr. Hans Holfelder was an internationally renowned radiologist and expert in radiotherapy. Even before 1933, he sympathized with the ideas of the National Socialists and expressed antisemitic views. In 1933, he joined the NSDAP and became a member of the SS. Up until Holfelder's death in October 1944, the SS-Röntgensturmbann (SS x-ray battalion), which he founded and commanded, examined hundreds of thousands of Germans and, once the war had started, forced laborers too for tuberculosis.
Holfelder introduced improved X-ray methods with the Röntgenreihenbildern (serial X-rays) – which enabled images of several people to be taken simultaneously – and the Schirmbildverfahren (screen image method) for single images. The X-rays made it possible to determine whether a person was suffering from tuberculosis. The words Geröntgt n[ach] Prof. Holfelder (x-rayed according to Prof. Holfelder) stamped on sick bay cards indicate that one of the two methods was evidently also used in concentration camps.