Radiation Biodosimetry: the ABCs of responding to a mass radiological event.

Sub: IR

Sec: Health

Context:

Radiation biodosimetry is extremely important in responding to a large-scale radiological event, such as an Improvised Nuclear Device or reactor accident.
It helps in the assessment of the level of radiation and the administration of drugs in accordance with the exposure levels.

What is biodosimetry?

Biodosimetry allows the measurement of the amount of radiation to which an individual was exposed based on changes in blood, urine, or hair.
It would be particularly useful in a radiological event where the exposed individuals do not carry any personal radiation monitoring devices.

Methods employed in biodosimetry:

The gold standard biodosimetry assay is measurement of chromosome aberrations, in white blood cells.
The International Commission on Radiation Units and Measurements and International Atomic Energy Agency have issued guidance on performing biodosimetry and interpreting data.
When irradiated, DNA in the blood cells gets broken and is repaired within a few hours.
In some cases, there is an incorrect repair, joining fragments from different chromosomes, forming a ‘DicentricChromosome (DC)’ – a chromosome with two centromeres.
DC can only be formed by radiation, measuring these chromosomes is a specific and sensitive indicator of past radiation exposure.
In order to measure DC, lymphocytes from the exposed individuals are cultured to begin division and then the chromosomes are spread on a slide and stained.
The Dicentric Chromosome Assay (DCA) has been successfully employed in many radiation accidents, where the number of exposed people is small.

In Cytokinesis Block Micronucleus Assay (CBMN), the white blood cells are made to divide, but arrested before division is complete.
This forms a cell with two nuclei.
Post exposure to radiation, some DNA is ejected during division forming a ‘micronucleus‘
This ‘micronucleus‘ helps in determining the exposure to radiation.
Measurement on the phosphorylated form of specific histone protein an inherent component of chromosomes known as the “gamma-H2AX’ assay has the potential to segregate the exposed from that of unexposed and those exposed to low dose versus high dose without culturing cells, within 6-8 hours of time.

About Rapid Automated Biodosimetry Tool (RABiT):

The Rapid Automated BIodosimetry Tool (RABIT) is designed to be a completely automated, ultra-high throughput robotically-based biodosimetry workstation.
It analyzes fingerstick-derived blood samples (30 μl, essentially a single drop of blood), either to estimate past radiation dose, or to identify individuals exposed above or below a cutoff dose.
The first iteration of the Rapid Automated Biodosimetry Tool (RABiT) used custom robotics to perform the CBMN assay with a target throughput of 6000 samples per day per machine.

About High-throughput screening:

HTS(High-throughput screening)systems use robotics, liquid handling devices and automated microscopes to quickly conduct millions of chemicals, genetic, or pharmacological tests.