Scintillation Proximity Assay is an established radioisotopic assay technique widely used in high throughput screening laboratories. The requirement for miniaturization of these arrays has led to the development of microplates containing 384, 864, 1536 or even higher numbers of wells. Imaging is the only practical detection method for quantifying the assays in such high density plates.
Robert A. Jessop,
"Imaging proximity assays", Proc. SPIE 3259, Systems and Technologies for Clinical Diagnostics and Drug Discovery, (10 April 1998); doi: 10.1117/12.307332; https://doi.org/10.1117/12.307332