Being able to see inside a living human body has always been a holy grail for medical diagnosis. But X-ray photographs and fluoroscopes had their limitations, so Dr. Benedict Cassen (1902–1972) invented the scintillation scanner, or "scintiscanner" in 1951. This imaging device was based on plotting radioisotopes introduced into the patient. Dr. Cassen's work with UCLA's Laboratory of Nuclear Medicine and Radiation Biology launched the field of nuclear medicine that has become important throughout the world for medical diagnosis.
The scintiscanner produced a crude picture by moving a scintillation detector over the area to be scanned and recording the intensity levels with a dot-producing mechanism. It was first used to image the thyroid gland after the administration of radioiodine. With the development of organ-specific radiopharmaceuticals, the scanner was widely used during the late 1950s until the early 1970s.