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Report No. 136 – Evaluation of the Linear-Nonthreshold Dose-Response Model for Ionizing Radiation

Report 135

There are two methods in which IRT (Imaging Radiation Treatment) can be used to evaluate the linear-nonthreshold dose-response curve for Ions, Neutrons and Radon. These methods are referred to as the linearity and dose-effect relations. The first method is more suitable for assessing the Ions, Neutrons and Radon doses in the laboratory settings. In this method, the exposed subjects (Linear dose-resistant subject) are exposed to the measured amounts of Ionizing Radiation (Ions, Neutrons and Radon). The measurement of the concentration of Ions in the blood, or in a tissue, after the completion of a particular exposure period is called the Non-reactive Curcibility Index (NCI).

The second method for evaluation of the linear-nonthreshold dose-response curve for Ions, Neutron and Radon is called the dose-effect relation for Ions, Neutron and Radon. In this method, the exposed subjects (Linear dose-resistant subject) are exposed to measured amounts of Ionizing Radiation (Ions, Neutron and Radon). The measured results are compared with the corresponding experimental curves in the model. If the experimental results are significantly different from the corresponding model curves, the difference may indicate a significant protection of the subject from Ionizing Radiation. In this type of model, the time constant K d is used. The term “time” is used here because it has been observed that prolonged application of a protected device will not alter the effect of the measured dose on the subject, provided that no change in the model parameters is brought about by those parameters.

A third and similar method is employed in the measurement of the dose effectiveness of Ions, Neutron and Radon against gamma-ray beams. This method is also called the dose-effectiveness model for Ions, Neutron and Radon. This method was invented by Dr. Bernard Spilsbury and implemented in the US Environmental Protection Agency’s (EPA’s) Office of Environmental Health Hazards. The method is applicable to Ions, Neutron and Radon, but not to gamma rays.

There are various factors which influence the application of the above-mentioned method for the measurement of the effects of Ionizing Radiation on biological structures. The most important of these factors is the thickness of the structure, which determines the effectiveness of the protection offered. Other factors included in the model are the area of application and the nature of the measured parameters.

The other factors included in the models are the spatial resolution of the model and the number of input parameters. The output of the model is then compared with the known data set of natural background radiation. If the output matches with the known background, then the model is accepted as accurate. The model is then evaluated against a control set of controls, which were performed at a specific time interval to evaluate the effect of the increasing level of radiation.

The above-mentioned examples are just an example of how such models are applied in practice. Others include the geomagnetic model, the electrical model and the hydrodynamic models. These four types of models are used for evaluating the effect of electromagnetic fields on biological structures. It should be noted that the use of the above examples is meant only to give a clear idea of how these models are applied. They are not meant to serve as an example for the modeling of biological issues.