Radiopharmaceuticals, also called medical isotopes, are specialized forms of medicine that help to diagnose and treat many challenging medical conditions including cancer. Their central advantage over other pharmaceuticals is that they emit radiation in the form of a photon of light that can be used to diagnose or identify specific conditions, or a charged particle of matter that can destroy diseased cells.
Targeted alpha therapy is an example of a technology that is used to kill dispersed cancers such as leukemia and lymphoma. A radioisotope that undergoes alpha decay is chemically bonded to an antibody and injected into the body. The antibody seeks out and binds to the desired cell, then after a certain time period, the attached radioisotope decays and the alpha particle emitted during the decay kills the targeted cell. Targeted alpha therapy has shown great promise but has been strongly limited by the supply of suitable radioisotopes. The most promising is bismuth-213, which has a half-life of 45 minutes and is formed from the decay of uranium-233.
Technetium-99m is an example of a radioisotope used for the detection of various medical conditions. Tc-99m is chemically bonded to a variety of different agents that target specific areas of the body, such as the heart, bones, liver, or gall bladder. As it undergoes radioactive decay, Tc-99m emits a high-energy photon of light, called a gamma ray, that can be detected by an external camera. This procedure, called single-photon emission computerized tomography (SPECT) allows doctors to image areas of concern within the body. Tc-99m has a half-life of only six hours, and is formed by the decay of molybdenum-99, which in turn is formed in a nuclear reactor from the fission of uranium. The medical molybdenum market accounts for the vast majority of yearly radiopharmaceutical use, approximately 30 million procedures a year, and is currently threatened by supply contractions.
Tc-99m (from Mo-99) and Bi-213 are both important medical isotopes that can be formed most efficiently in a liquid-fluoride thorium reactor (LFTR). Mo-99 is formed while the reactor operates and can be readily extracted during operation, purified, and shipped to hospitals for imaging use. This approach would be thousands of times more efficient for Mo-99 production than current techniques and would expand the Mo-99 supply sufficiently to allow for greater use in underdeveloped countries. Medical imaging using the SPECT technique can diagnose quickly and in a non-invasive manner, giving doctors more time to prepare treatments for dozens of different conditions.
Bi-213 is uniquely formed from the decay of the nuclear fuel in a LFTR, uranium-233, which is turn forms from neutron absorption on thorium. One of the precursors of Bi-213, thorium-229, would be chemically removed from the LFTR and purified. One of its daughter products, actinium-225, would then be shipped to hospitals on a regular basis and would provide a steady Bi-213 supply for patients afflicted with difficult dispersed cancers like lymphoma and leukemia. This would spare these patients from the suffering and danger of chemotherapy as a treatment option.
In order to move forward with LFTR development, investment is urgently needed to tackle key technology challenges, which could be solved within 24 months of initial funding.