Cytogenetic Biodosimetry for Radiation Disasters: Recent Advances (2005)

Potential scenarios of radiation exposure resulting in mass casualties require individual, early, and definitive diagnostic radiation dose assessment to help provide medical aid within days of the occurrence of a catastrophe. The long-range goal of the Armed Forces Radiobiology Research Institute (AFRRI) Biological Dosimetry Team is to identify, develop, and optimize broad dose-range biodosimetry methods, using in vitro models, and to validate those methods, using suitable in vivo models. Of these methods, the cytological biodosimetry methods are capable of assessing radiation dose both in whole-body and partial-body radiation exposure scenarios. Chromosome-aberration analysis in exposed individual’s peripheral blood lymphocytes is an internationally accepted “gold standard” cytogenetic biodosimetry method that can be used to assess dose to help develop a treatment strategy within days of a radiation catastrophe. We have established the conventional lymphocyte metaphase-spread dicentric assay, in accordance with international harmonized protocols, and have used the assay to estimate radiation doses in several accidents. Current efforts focus on increasing sample throughput via automation. We systematically addressed the development of an automated cytogenetic laboratory that can triage by exposure group (not life-threatening, potentially life-threatening, and significantly life-threatening) and thereby efficiently differentiate radiation-exposed individuals from the “concerned public” following a disaster. Our studies included concept feasibility, workflow analysis, possible process reengineering, bottleneck elimination in manual processing, and proof-in-principle experiments. With automation, up to 500 samples per week can be analyzed in triage mode in which chromosome aberration analysis is restricted to 20 to 50 metaphase spreads per sample compared with the conventional approach of 500 to 1000 spreads. In another effort, we are developing and validating a novel cytogenetic bioassay, the rapid interphase chromosome aberration (RICA) assay, using suitable in vivo models. In this innovative method, radiation-induced chromosome aberrations in specific chromosomes are studied directly and rapidly in resting peripheral blood lymphocytes after inducing premature chromosome condensation either by fluorescence in situ hybridization or by immuno-enzymatic detection based on bright-field microscopy. The latter method is amenable to automation using image analysis. We used an accidentally radiation-exposed cohort, in Thailand in Feb. 2000, to determine the ability of the RICA assay to assess whole-body equivalent dose; our results indicated that the RICA assay can be used to assess radiation-induced damage to a specific chromosome in interphase cells. We are using a rodent model to determine the persistency of radiation-induced damage and the influence of sampling delay on dose estimation. These studies, in general, will contribute to an improved diagnostic response to a mass-casualty situation and will improve protection and survivability in adverse ionizing radiation environments.