Radiation Biodosimetry: The ABCs of Responding to a Radiological Event (GS Paper 3, Science & Technology)
Introduction
- Radiological events, such as an Improvised Nuclear Device detonation or a reactor accident, necessitate the rapid identification of individuals exposed to significant radiation doses.
- This identification is crucial for administering recently approved drugs for treating radiation sickness.
- Radiation biodosimetry is pivotal in this context, offering a means to determine radiation exposure levels in individuals.
What is Biodosimetry?
- Biodosimetry is a scientific method that quantifies radiation exposure based on biological changes in blood, urine, or hair.
- This technique is especially useful when individuals lack personal radiation monitoring devices.
- The gold standard assay in biodosimetry is the measurement of chromosome aberrations in white blood cells.
- When DNA in these cells is irradiated, it can break and incorrectly repair, forming Dicentric Chromosomes (DC) - a specific marker of radiation exposure.
- To measure DC, lymphocytes from exposed individuals are cultured, and their chromosomes are spread on a slide and stained.
- The DCs are then counted using microscopy, a process that takes about 2-3 days.
- Despite its precision, this Dicentric Chromosome Assay (DCA) is labor-intensive and impractical for large-scale events due to its limited throughput.
Alternative Assays
- The Cytokinesis Block Micronucleus Assay (CBMN) is a simpler alternative to DCA.
- This assay involves inducing cell division in white blood cells, arresting the process to form binucleated cells, and identifying micronuclei that indicate DNA damage.
- Though slightly easier to perform, the CBMN assay requires about three days for results due to extended cell culturing.
- A more rapid assay is the gamma-H2AX assay, which measures the phosphorylated form of a specific histone protein, indicative of radiation exposure.
- This test can distinguish between exposed and unexposed individuals and differentiate low from high-dose exposures within 6-8 hours.
- However, it must be conducted within 24 hours of exposure due to the kinetics of histone phosphorylation.
Increasing Throughput
- Traditional methods to increase biodosimetry assay throughput involve lab networks sharing samples globally.
- However, this approach is inadequate for large-scale radiological events.
- The Center for Radiological Research at Columbia University has developed automatable versions of major biodosimetry assays using 96-well plates.
- The Rapid Automated Biodosimetry Tool (RABiT) and its second iteration (RABiT-II) utilize custom robotics and High Throughput Screening (HTS) platforms to perform assays with significantly higher throughput.
- These systems, widely used in the pharmaceutical industry and academia, allow for the rapid analysis of thousands of samples per day per machine.
Benefits of High Throughput Screening Platforms
HTS platforms offer several advantages, including:
- Increased Throughput: Capable of analyzing thousands of samples per day, essential for large-scale radiological events.
- Reliability: Rigorous quality control and continuous operation ensure system reliability during crises.
- Trained Personnel: A broad base of trained users and maintenance personnel ensures efficient operation.
Conclusion
- High throughput automated biodosimetry provides a crucial capability for dose assessment in large-scale radiological or nuclear incidents.
- It complements existing triage systems by categorizing exposed individuals for appropriate treatment and facilitating long-term epidemiological follow-up.
- This technology represents a significant advancement in the ability to respond effectively to radiological emergencies.
