The introduction of Cesium-131 represents the culmination of decades of work and millions of dollars of investment. Top medical centers, hospitals and clinics across the United States are now offering this breakthrough treatment for cancer patients. The word brachytherapy derives from the Greek prefix brachy, meaning “short” or “close,” because the titanium capsules containing the radioisotope are implanted directly into the cancerous prostate gland. Treatment of cancer using low dose radiation or “seed” brachytherapy was pioneered in the 1960’s as an effective alternative to radical prostatectomy. Pioneers in brachytherapy research initially theorized about the use of Cesium-131 in a titanium capsule, however scientific and economic limitations at the time prevented its development and Iodine-125 emerged as an alternative. Beginning in 1967, Iodine-125 became the first radioisotope manufactured in a titanium capsule, or seed. While its use continues to this day, many patients and doctors in recent years have chosen Palladium-103, a faster-acting, shorter half-life isotope than Iodine-125. In order to obtain the clinical benefits of Palladium’s short half-life, patients and clinicians were forced to settle for lower energy or tissue penetrating power. A team of scientists continued to believe the physical characteristics of Cesium-131* could potentially provide superior clinical benefits for seed brachytherapy patients. The team developed the patented process for economically separating and purifying Cesium-131 and in 1998 Isoray was founded to manufacture and commercialize Cesium-131 brachytherapy seeds to treat cancers.