Replacing Cesium-137 Irradiators: Alternative and Emerging Technology

Commercially Available X-ray Technology

In 2012, the U.S. Food and Drug Administration approved the use of non-radioactive x-ray devices for sterilizing blood that provide the same medical outcomes as cesium-137 blood irradiators. As of 2015, two types of these devices are available with a typical cost of approximately $270,000 per unit. The X-ray units require far less security and shielding, eliminate liability, and do not require expensive disposal at the end of the machine’s life-cycle.

X-ray irradiators deliver ionizing radiation of 25 gray or greater to the midpoint of the target product, meeting the same medical requirements as cesium irradiators for Transfusion-associated graft-versus-host disease (TA-GvHD) prevention. Although device configurations vary, x-ray irradiators typically use a conventional X-ray tube system enclosed in a lead-shielded container. To ensure a uniform radiation dose without target rotation, the device may use X-ray tubes, one on each side of the chamber in which the target container is placed. In one newer design, carousels turn to uniformly expose target blood to ionizing radiation generated by an X-ray tube in a 360-degree output around a cylindrical design. In general, electronic systems power the X-ray tubes and operate timers to control interlocks and exposure. X-ray devices typically weigh approximately 2,000 pounds, with dimensions similar to cesium-137 irradiators.

The reliability of X-ray devices has improved significantly since the machines were first introduced and X-ray irradiators now offer a direct replacement for cesium-137 irradiators. X-ray irradiators also have additional benefits and options not available with traditional cesium-137 irradiators. The unique design of the rotator typically allows users to increase their throughput and treat more blood products in less time (e.g. some models allow simultaneous irradiation of 6 blood products (i.e. whole blood, platelets, and loaded Syringes) in 5 minutes during a single cycle). Other models have self-contained cooling systems and wheels for easy transportation, making the irradiator more ergonomic and easy to use and maintain. Most importantly, all regulatory and security requirements needed for cesium-137 irradiators are eliminated – including license fees – with the transition to X-ray devices, as well as the need to perform additional monitoring for radiation exposure.

More technical comparisons and resources can be found in this detailed report from the University of California Systemwide Radioactive Source Replacement Workgroup. Additional literature reviews written by the Center for Nonproliferation Studies (CNS) on blood irradiation and research irradiators can be found here (.pdf) and here (.pdf) respectively. These are other helpful resources to review:

• A comparison chart of the available X-ray technologies for blood irradiation
• A comparison chart of the available X-ray technologies for research irradiation
• A list and map of commercially available X-ray technologies around the world

Interested in getting federal funding to make your switch?

The Cesium Irradiator Replacement Project offered by the National Nuclear Security Administration’s Office of Radiological Security provides incentives for qualified sites to make the switch. Learn more about this initiative and how to get federal funding for replacement here. This 24-minute presentation about alternative technologies and how to get funding for replacement of blood irradiators using cesium-137 technology also has some key information.

Emerging UV Pathogen Technology

Ultraviolet (UV) pathogen reduction technology has recently emerged as an alternative to blood irradiation. In 2014, the FDA approved two UV systems to treat plasma and platelets, respectively, for pathogen and bacterial reduction. The systems use the UVA wavelength range of illumination (320-400 nm) with the molecule amotosalen, which interacts with nucleic acid to inhibit pathogen and leukocyte replication. The treatment causes pathogen inactivation, meaning that harmful bacterial and other viral infections are eliminated from the blood components (e.g. hepatitis B and C, HIV, West Nile virus and bacteria, as well as emerging pathogens such as Chikungunya, malaria and dengue).

While UV systems are not yet FDA approved for TA-GvHD prevention, based on the level of T cell inactivation demonstrated, UV systems are labeled to indicate they potentially reduce the risk of TA-GvHD. The AABB modified its U.S. standards in 2016 to indicate that the use of licensed pathogen reduction systems meets the standard for prevention of TA-GvHD. However, a red cell and a whole blood system requires FDA approval in the United States for UV systems to replace cesium-137 or X-rays irradiators.

One leading company making UVA light blood irradiation is Cerus, using its INTERCEPT system for platelet and plasma treatment. The Intercept system works by introducing an Amotosalen into the blood bag, which targets certain nucleic acids. Another company that provides UV technology is Terumo BCT with their Mirasol system. They use a combination of riboflavin (vitamin B2), a non-toxic, naturally occurring compound, and a specific spectrum of ultraviolet (UV) light to inactivate viruses, bacteria, parasites and white blood cells that may be present in collected blood products.

Download this illustrative chart to see details of non-isotopic systems available for blood irradiation.

For a deeper dive into the details about alternative technologies, watch the presentations from the 2017 workshop hosted by the New York City Department of Health and Mental Hygiene in partnership with NTI and ORS, and the presentations from 2018 workshops hosted by the University of California, also in partnership with NTI and ORS. The University of California (UC) system collected a set of research papers and resources comparing cesium-137 to X-ray irradiators and made them available for review here.

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