Determining radiation exposures across a geographic region from a small number of individuals

Protocol for Geostatistical Determination of Radiation Dosimetry Maps of Population-Scale Exposures

Accurate radiation dose estimates are critical for determining eligibility for therapies by timely triaging of exposed individuals after large-scale radiation events. However, the universal assessment of a large population subjected to a nuclear spill incident or detonation is not feasible. Even with high-throughput dosimetry analysis, test volumes far exceed the capacities of first responders to measure radiation exposures directly, or to acquire and process samples for follow-on biodosimetry testing. We aimed to design a protocol which can significantly reduce data acquisition and processing requirements for timely treatment of eligible, affected individuals in population-scale radiation exposures. Method in Brief: The spatial boundaries of graduated radiation exposures were determined by targeted, multistep geostatistical analysis of small population samples. Physical radiation plumes modelled nuclear detonation scenarios of simulated exposures at 22 US locations. Models assumed only location of the epicenter and historical, prevailing wind directions/speeds. Initially, locations proximate to these sites were randomly sampled (0.1% of population). Empirical Bayesian kriging established radiation dose contour levels circumscribing these sites. Densification of each plume identified critical locations for additional sampling. After repeated kriging and densification, overlapping grids between each pair of contours of successive plumes were compared based on their diagonal Bray-Curtis distances and root-mean-square deviations, which provided criteria (<10% difference) to discontinue sampling.