Abstract
The dosimetric measurement quantities currently adopted by national regulation or to standardization of dosimetric models adopted by CT equipment manufacturers are based in a metric, introduced around thirty years ago: the Computed Tomography Dose Index (CTDI). This quantity, apart from its variations on definition, represents the absorbed dose along the longitudinal axis of an acrylic phantom with well-defined and known dimensions.Since the introduction of CTDI as an adequate metric to determination of dosimetric characteristics from tomographic procedures, and since its acceptance among the scientific community and equipment manufacturers, the technology significantly changed the architecture of these systems, as well as the clinical conducts for its using. The introduction of cone-beam, together with the enlargement of the dimensions from the radiation beam to accommodate, in a few number ofrevolutions, a bigger region of interest, brought significant clinical advantages. However, this enlargement in the X-ray beams used in tomographic exams and the use of helical techniques made, also, less appropriate or impractical the methodologies for measuring this metric.Hence, many research groups all over the world proposed new metrics that can deal with technological progress from nowadays and predictable in a near future and even provide representative values of doses in patients. The mathematical formulation for this metrics will be used as conceptual foundation for implementation of part of the present project.This master-project work proposal consists in estimating the normalized radiation dose in organs under tomographic exams using adult and pediatric simulation objects, together with a group ofseventeen tomographic equipment of clinical use, installed at Complexo do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo.The student shall calculate the values of CTDIVol,Regional and associate these to the applied current in each part of the phantom`s body. She shall also calculate the effective diameter of each part of the phantom`s body from direct measurements in the pieces that compose these objects. At the end, with these values, se shall determine the Normalizes Organ Dose (NOD).
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