Developments in Biodosimetry Methods for Triage with a Focus on X-band Electron Paramagnetic Resonance In Vivo Fingernail Dosimetry

摘要

Instrumentation and application methodologies for rapidly and accurately estimating individual ionizing radiation dose are needed for on-site triage in a radiologicaluclear event. One such methodology is an in vivo X-band electron paramagnetic resonance (EPR) physically-based dosimetry method to directly measure the radiation-induced signal (RIS) in fingernails. The primary components under development are key instrument features, such as resonators with unique geometries that allow for large sampling volumes but limit RIS measurements to the nail plate, and methodological approaches for addressing interfering signals in the nail and calibration of dose from RIS measurements. One resonator development highlighted here is a Surface Array Resonator (SRA) designed to reduce signal detection losses due to the soft tissues underlying the nail plate. Several SRA geometries, along with ergonomic features to stabilize fingernail placement, have been tested in tissue-equivalent nail models and in vivo nail measurements of healthy volunteers, using simulated RIS in their fingernails. These studies demonstrated RIS detection sensitivities and quantitation limits approaching the clinically relevant range of ≤10 Gy. Studies of the capabilities of the current instrument suggest that a reduction in the variability in RIS measurements can be obtained with refinements to the SRA and ergonomic features of the human interface to the instrument. Additional studies are required before the quantitative limits of the assay can be determined for triage decisions in a field application of dosimetry. These include expanded in vivo nail studies and associated ex vivo nail studies to provide informed approaches to accommodate for a potential interfering native signal in the nails when calculating the RIS from the nail plate spectral measurements, and to provide a method for calibrating dose estimates from the RIS measurements based on quantifying experiments in patients undergoing TBI or total skin electron therapy.