Determination and dosimetric evaluation of the calibration curves of HU in extended acquisition mode for the algorithm Acuros XB

The dose calculation algorithms used in radiotherapy use a calibration curve to convert HU to mass density or electronic density, making it possible to differentiate the dose absorptions of different tissues. The present study aimed to determine the calibration curve of HU for non-extended and extended CT image acquisition modes, in addition to its dosimetric evaluation. CT images of simulating objects of different materials was acquired, varying parameters such as beam energy, current, resolution, FOV and image analysis software to evaluate the influences in the measured HU. The results did not show variations of HU for different resolutions, currents and software. For different energies and FOV, the HU of the structures varied about 35% and 10%, respectively. The extended HU calibration curve was very close to the non-extended acquisition for low-density materials, becoming different only for high densities, finding results consistent with presented in the literature. There was considerable variation over the standard Acuros XB calibration curve. (author)