IsoRay, through its subsidiary, IsoRay Medical, produces Proxcelan Cesium-131 brachytherapy seeds. IsoRay Medical, founded in 1998, develops, manufactures and markets isotopes for the medical treatment of various malignant diseases. The company provides brachytherapy seeds that are used for the treatment of prostate cancer. It uses Cesium-131, which is an isotope that offers benefits for breast, lung, liver, brain and pancreatic cancer.