DOSE PROFILE AND DOSE INDEX ANALYSIS IN COMPUTED-TOMOGRAPHY

A function to describe the dose profile in Computed Tomography (CT) be ams is presented. To measure the dose profile free-in-air a set of 20 thermoluminescence dosemeters was used. The symmetry or asymmetry, lef t and right penumbrae, length of the plateau and full width at half ma ximum (FWHM) are function parameters, determined with the fit to the T LD data, allowing a thorough characterisation of the beam. A new CTDI (designated CTDI) is defined using the FWHM instead of the nominal sl ice thickness, which is physically the correct normalising factor, pro ducing a more precise figure for the dose evaluation. In addition, a p lateau dose is defined, and these two dose descriptors are discussed a nd compared.