The 1920s saw the discovery of positron, followed by the first cyclotron installed in the 50s that lead to the first Positron Emission Tomography (PET) scan being developed in the 70s. The development of radiopharmaceuticals and, in particular, the development of labelled 2-fluorodeoxy-D-glucose (2FDG) was a major factor in expanding the scope of PET imaging and first administered to two normal human volunteers in August 1976.
Then first single-plane PET scan was built in 1961. A design using two 2-dimensional arrays was the logical extension of positron instrumentation. PC-I was the first instrument using this concept and was designed in 1968,