Assessment of Total- and Partial-Body Irradiation in a Baboon Model

Abstract

This biodosimetry study used irradiated baboons to investigate the efficacy of a kinetic multiparameter (clinical, physical, and biological) approach for discriminating partial-body irradiation (PBI) and total-body irradiation (TBI). Animals were unilaterally (front) exposed to 60Co gamma rays (8 to 32 cGy min) using either TBI or vertical left hemi-body irradiation (HBI), as follows: 2.5 Gy TBI (n = 2), 5 Gy TBI (n = 2), 5 Gy HBI (n = 2), and 10 Gy HBI (n = 2). Midline tissue doses were measured at the anterior iliac crest level with an ionization chamber, and body dosimetry was performed using thermoluminescent dosimeters. Blood samples were collected before exposure and from 1 h until 200 d after irradiation. Clinical status, complete blood cell count, biochemical parameters, and cytogenetic analysis were evaluated. The partial least square discriminant analysis chosen for statistical analysis showed that the four groups of irradiated baboons were clearly separated. However, the dicentric chromosome assay may not distinguish HBI from TBI in confounding situations where equivalent whole-body doses are similar and the time of exposure is sufficient for peripheral blood lymphocyte homogenization. Interestingly, as bone marrow shielding in HBI animals prevented aplasia from happening, hematologic parameters such as the platelet count and Flt-3 ligand level helped to distinguish HBI and TBI. Moreover, the ratio of neutrophil to lymphocyte counts, creatine kinase, and citrulline levels may be discriminating biomarkers of dose or injury. Both early and delayed clinical signs and bioindicators appear to be useful for assessment of heterogeneous irradiation.