Reports the first diagnostic procedure, done in 1925, using radioactive indicators on humans. "Less well recognized is the fact that Blumgart and his coworker Otto C. Yens, then a medical student, developed the first instrumentation used in a diagnostic procedure involving radioactive indicators. The instrumentation, a modified Wilson cloud chamber, turned out to be the detector most suitable for their purpose. Blumgart also showed remarkable foresight in outlining the requirements both for a satisfactory indicator (tracer) and for a satisfactory detector--requirements that still hold true today. The Blumgart-Yens modified cloud chamber was the birth of nuclear medicine instrumentation" (Patton, Dennis D., "The birth of nuclear medicine instrumentation: Blumgart and Yens, 1925," Journal of Nuclear Medicine, 44, No. 8 [2003] 1362-1365).  Digital facsimile from PubMedCentral at this link.