Self-Contained Blood Irradiator using Flat Panel X-ray Source

The National Academy of Sciences issued a report in February 2008 detailing isotope replacement priorities in the interests of national security [National Research Council, 2008] . 137Cs used in “self-contained” irradiators was identified as the single most dangerous isotope in the inventory, owing to its long half life (30+ years) and production as cesium chloride salt, which means it can be easily dispersed in a radioactive dispersal device (RDD). Of the 1,350 Cs irradiators in the U.S., approximately 650 are used for irradiating transfusion blood bags to inactivate leukocytes and thereby prevent transfusion-associated graft versus host disease (TA-GVHD), a gruesome condition in which active donor leukocytes attack the internal organs of immuno-suppressed patients, with fatality rates of over 90%. Replacement of blood irradiators with 60Co sources has been attempted, but has been unsuccessful. X-rays are the obvious alternative to isotopes. Previous attempts at using x-rays for blood irradiation, however, have been unsuccessful due to their reliance on inappropriate sources. Point-source X-ray tubes are not meant to be operated for several minutes, the time need to deliver the FDA-recommended dose of 25 Gy (min 15 Gy, max 50 Gy) to the blood bags. Stellarray proposes the development and deployment of a new type of self-contained blood irradiator (SCBI) to replace isotope irradiators. The heart of the SCBI is Stellarray’s patented flat panel x-ray source (FPXS), which is designed for continuous operation and is ideally suited for blood and other irradiation systems. In the FPXS, arrays of cathodes below a top exit window emit e-beam showers at high voltage to a large metal anode target assembly. This anode, the top window and side walls form the vacuum enclosure of the source. SCBI will be about the size of a microwave oven, compared to the refrigerator-sized irradiators now available, weigh between 200 and 500 lbs. (as opposed to 1.5 – 2 tons), be operable with 110 AC power for the small and medium sized models and with 220 single phase for the large conveyor model; require no external cooling, and be extremely reliable. Stellarray will develop and offer SCBI in three sizes: small (for two 400 ml bags or similar volumes), medium (four 400 ml bag equivalent), and large (three pairs of panels, with either tray or conveyor belt operation). Multiple interlocks, self shielding of the sources, and lead wall linings ensure safe operation. All three models will have dose rates > 8 Gy/min; closed loop oil heat exchangers; less than 10% dose variation in x, y or z directions; operation up to 160 kV; >4,000 hours lifetime; and full compliance with radiation safety standards. Commercial Applications and Other Benefits: SCBI can become a substantial business since it has been designed with user needs clearly in mind. It is well-suited for use in crowded blood banks and hospitals and requires no special security measures or changes to room utilities. It will be priced attractively, for a substantially lower cost of ownership compared to the alternatives. The use of the right source will make it highly reliable, so it can displace isotope irradiators.