In 1997, IsoRay was founded in Richland as a spin-off from the Pacific Northwest National Laboratory (PNNL) to develop, manufacture, and market isotopes for use in the medical treatment of various malignant diseases.

IsoRay through its subsidiary, IsoRay Medical was the sole producer of Cesium-131 brachytherapy seeds, which are expanding brachytherapy options throughout the body. Isoray merged with Viewpoint Molecular in 2023 and changed its name to Perspective Therapeutics.