Um método de correção e calibração de densidades determinadas em tomografia computadorizada

Abstract

There is currently an increase in the use of computer programs to determine the density of human tissues, with the purpose of aiding in diagnosis. One of these tools is the Synedra program, which must be calibrated in order to know the real values ​​of tissue densities. The objective of this study is to indicate correction values ​​for this quantity, read in a system for viewing DICOM images produced by Computed Tomography. In this study, a PMMA phantom was used to generate DICOM images, to know the densities determined by Synedra and to compare them with the data indicated by the phantom manufacturer. To generate the DICOM images, a 64-channel Aquilion CT scanner from Toshiba® was used, whose protocol establishes the following parameters: 120 kV, tube rotation time of 0.5 s, pitch of 0.828 and current of 500 mA. To check the calibration of the tomograph and the machine's own management program in order to obtain the linearity line between them, the Catphan simulator object was used. The densities were associated and determined for each structure of interest: lung, bone and soft tissue. The density found for PMMA was 123.5 HU. The density values ​​determined by Synedra were (125.9 ± 119.1) HU, (127.9 ± 116.2) HU and (123.2 ± 15.0) HU, thus the correction values ​​are -1.94%, -3.56% and +0.24% for the tissues: lung, bone and soft tissue. The procedure performed was able to confirm that corrections should be made in the computer programs to adjust the true density values ​​in human tissues. This method can be used in other programs that have tools for reading density. When using the Synedra program to analyze tissue densities, the suggested correction values ​​must be applied.