Author's personal copy Chapter 24 Radiation Dose Assessment by Using Lymphocyte Counts Shaowen Hu, William Blakely, and Francis Cucinotta Abstract Peripheral blood cell counts are important biomarkers of radiation exposure. With the successful application of a simplified compartmental modeling approach to simulate the perturbation of hematopoiesis system in humans after radiation exposure, we recently developed a HemoDose software program to estimate absorbed dose based on multi-type blood cell counts. Testing with patient data in some historical accidents indicates that either single or serial granulocyte, lymphocyte, leukocyte, or platelet counts after exposure can be robust indicators of the absorbed doses. In this work, the first week lymphocyte counts of five patients in the 2011 Bulgaria radiation accident are used to do serial points and single point calculations with HemoDose. Overall, the estimated doses are in good agreement with those evaluated with cytogenetic analysis in two independent laboratories. The program also confirms that calculation with individual reference counts can significantly increase the accuracy of this simple dose estimation algorithm. These results indicate that HemoDose can be employed as an easy-to-use and deployable biodosimetry tool for predicting the clinical severity, treatment, and survivability of exposed individuals and triaging those with minimum or no exposure, especially in a large-scale nuclear/radiological disaster scenario involving mass casualties. 24.1 Introduction The United States must be prepared for radiological accidents and terrorist activities that may involve large number of irradiated personnel [1]. Researchers have put much effort to develop various physical and biological dosimeters to rapidly S. Hu () Wyle Science, Technology and Engineering, Houston, TX, USA e-mail: shaowen.hu-1@nasa.gov W. Blakely Radiation Biodosimetry Research Program, Uniformed Services University of the Health Sciences, Armed Forces Radiobiology Research Institute, Bethesda, MD, USA F. Cucinotta School of Allied Health Sciences, University of Nevada, Las Vegas, NV, USA © Springer Science+Business Media Dordrecht 2015 S. Apikyan, D. Diamond (eds.), Nuclear Terrorism and National Preparedness, NATO Science for Peace and Security Series B: Physics and Biophysics, DOI 10.1007/978-94-017-9891-4_24 253