Biomedical subjects

Ana F Maia

Publications and source records attributed to Ana F Maia.

3 recordsLinked to original sources

PubMed2006

A simple method for evaluation of half-value layer variation in CT equipment.

Tandem systems, each formed by a pencil ionization chamber with and without a specific covering, were developed and tested in standard radiation beams. These systems were designed to be used in computed tomography radiation beams, where the half-value layer (HVL) determination is not an easy task. The behaviour of the tandem systems in diagnostic radiology showed the possibility of their use to confirm HVL values previously determined by the conventional HVL measurement method in quality control programmes. These systems also have other advantages: low cost, easy application and quick measurement procedure.

Aluminum↗

PubMed2005

A new extended-length parallel-plate ionization chamber.

A special parallel-plate ionization chamber was developed. The motivation for the construction of this new chamber was mainly to fulfil the need of a reference system for computed tomography standard beams in the Calibration Laboratory of IPEN. However, the chamber was tested also in standard radiation beams of mammography and conventional diagnostic radiology. The chamber was manufactured at the institute workshop, as simply and cheaply as possible. Its design differs from the common ionization chambers used in dosimetric procedures of computed tomography equipment, because it is a parallel-plate chamber instead of a cylindrical chamber. However, its dimensions and sensitive volume are very similar to those of a commercial pencil ionization chamber. The new ionization chamber was submitted to several characterization and quality control tests, showing its very good performance.

Biophysics↗

PubMed2003

Performance of a pencil ionization chamber in various radiation beams.

Pencil ionization chambers were recommended for use exclusively in the computed tomography (CT) dosimetry, and, from the start, they were developed only with this application in view. In this work, we studied the behavior of a pencil ionization chamber in various radiation beams with the objective of extending its application. Stability tests were performed, and calibration coefficients were obtained for several standard radiation qualities of the therapeutical and diagnostic levels. The results show that the pencil ionization chamber can be used in several radiation beams other than those used in CT.

Calibration↗