Dosimetric impact of CT-to-ED curves on prosthesis irradiations and high atomic number heterogeneities

In Radiotherapy treatment, patients with prostheses have a limitation in planning and inaccuracies in dose calculation. Although precise algorithms in heterogeneities corrections exist, the primal difficulty lies on the establishment of CT-to-ED correction curves to high values of HU. On 12 bits CT scans, the saturation occurs around 3070 HU; however, 16 bits CT scans that don't saturate with high Atomic Numbers (Z) are already implemented. The objective of the present work is to evaluate the dosimetric gain in irradiations of heterogeneities of high Z when correction curves with high HU units are used. The results indicates a significant dependence of the curves of high HU with the evaluated tomograph, directly impacting the correction of heterogeneities and causing deviations up to 11.3% in terms of attenuation. (author)