Simulation of dicentric formation due to exposure to gamma radiation

Since the mid-1960s, the science of biodosimetry has developed and become an advanced tool in research and in radiation exposure investigations. Assessing exposures due to radiation accidents has an important role in medical treatment and in understanding exposure scenarios, especially large scale incidents.. Biodosimetry includes methods to measure physical and biological exposure parameters, such as teeth, hair and nails by electron spin resonance (ESR) or by optically stimulated luminescence (OSL) to determine gene activation, evidence of repair mechanisms and production of unusual metabolic products .Ionizing radiation produces radiolysis and formation of free radicals in the fluid inside cells. The energy to form an ion pair during radiolysis of water is about 20 eV. Every normal cell has 23 x 2 chromosomes and the free radicals induced by radiation inside the cells cause a wide range of damage to the chromosomes. Cytogenetic biodosimetry is based on the dicentric chromosomal aberrations assay (DCA). This is the "gold standard" biotechnology technique for estimating medically relevant radiation doses. When the energy associated with ionizing radiation is transferred to molecules in cells, the DNA that is embedded in the genetic material is damaged in proportion to the type and amount of energy that is absorbed. In human lymphocytes, this leads to the appearance of structurally abnormal chromosomes when cells attempt to divide following radiation exposure. The number of dicentrics is quantified and compared to a calibration dose-response curve, established in vitro to derive an estimate of the dose received.An important question in dosimetry is whether the individual received whole or partial body radiation exposure or a non-uniform dose. A single TLD badge cannot answer this question. However, biodosimetry can provide additional information. By assessing the ratio of dicentric to normal chromosomes and excluding other factors, a specific individual dose response curve can be created. In case of partial or non-uniform exposure, the lymphocytes in different parts of the body will respond differently. Within one day or less, the exposed lymphocytes will fully mix with the unexposed, normal lymphocytes through blood circulation to get a uniform mixture. The range of absorbed doses inside the exposed parts of the body and the extent of partial/full exposure will cause a spatial dicentric distribution profile in the blood sample. The Dolphin and Qdr biological methods are useful for determining whole or partial body exposures. However, this study used simple dosimetry to demonstrate the feasibility of a simulation method that will predict the extent of dicentric chromosome formation based on partial, full and non-uniform exposures with selected types of photon beams