Methods for Assessing Organ Doses using Computational Models

Abstract

The radiation risk from ionising radiation in different organs and tissues of the human body may he quantified using equivalent dose. As organ doses usually cannot be measured directly in patients, it is necessary to establish suitable conversion coefficients between organ doses and measurable dose quantities. For this purpose, computer codes, often based on Monte Carlo techniques, simulating the radiation transport in material are commonly used together with computational models of the human body. Most computational body models in use are mathematical models, in which mathematical expressions representing simple geometrical bodies are used to describe idealised arrangements of body organs. Additionally, tomographic models were developed in recently ears which use computed tomographic data of real persons to provide three-dimensional representations of the body. Using these computational models, numerous studies concerning organ and tissue doses from diagnostic radiology were performed. Organ dose conversion coefficients from various types examinations are available in the literature. In some of these studies, the influence of single technical exposure conditions (e.g tube v oltage. filtration, field size and location and focus-to-skin distance) on organ and tissue doses was examined. Additionally, the tomographic models enable the assessment of the influence of moderate vanations of the patient size on organ doses. They, therefore, improve the applicability of data for deriving doses to individual patients.