Development of a chest phantom for testing in Computed Tomography scans

To optimize the process of Computed Tomography (CT) scans, it is important to know the dose distribution in order to vary the acquisition parameters. The aim of this study is to evaluate the variation of CT Dose Index (CTDI) in chest scans, by using two chest phantoms. In this study it was used a cylindrical chest phantom made in polymethylmethacrylate (PMMA) and a second phantom was developed in PMMA with the same volume and an oblong shape, based on the dimensions of an adult human chest. The two phantoms have five openings, one central and four peripheral out of phase 90 degrees, which allow placing a pencil ionizing chamber in five positions. In a CT scanner GE, Discovery model with 64 channels, the central slice of the two phantoms were irradiated successively to obtain air kerma in PMMA measurements using the pencil chamber. From the measurements obtained in these five positions in the phantoms, it was possible to obtain the volumetric CTDI for both chest phantoms. By comparison of the results, it was demonstrated that the oblong phantom, with a similar human chest shape, have received higher doses, mainly in the anterior, posterior and central region. The volumetric CTDI indicates a value 5.1% higher for the oblong phantom.