Study on the dose profile in CT-fluoroscopy.

This work aims to contribute to the description of the dose profile in Computed Tomography Fluoroscopy (CTF). Our approach uses a function model to fit the single slice dose profiles (SSDP) for any point inside the gantry of the CT unit, with special attention to points off the rotation axis. The function model was successfully tested with measurements performed using GafChromic film. The parameters of the SSDP at the rotation axis (isocenter) and at 8 cm and 16 cm off the isocenter were determined. The model allows an estimation of the slice thickness at the isocenter and for points at 8 cm and 16 cm off the isocenter. The differences between the slice thicknesses results in overestimation of the Computed Tomography Dose Index, CTDI, by values as high as 20% if the nominal slice thickness instead of the model estimated value is used. The results obtained in this work provided a good description of the dose profiles, which can be used in further studies such as comparisons with measurements performed with phantoms and patients.