PO-0879: Dosimetric fluence correction in non-rigid IMRT adaptation: preserving the penumbra margin

Results: Figure 1 shows a boxplot diagram of the 2% 2mm gamma pass rate (GPR) within the PTV, averaged over all 20 patients for each CT based pCT. The dosimetric accuracy of the pCT increases when additional bulk densities are utilized for the pCT. However, the dosimetric accuracy of even the most complex bulk density pCT was clinically unacceptable (Fat Density, 78% average GPR). However, the pCT combined with the CT electron density information of the affected vertebral body did deliver clinically acceptable results (99% average GPR). The black triangles in Figure 1 shows the GPR result of the MR based pCT’s of one patient.Conclusions: In bone metastases, the MR-only bulk density approach is not able to yield clinical acceptable results. We have shown however, it is possible to use a MRI-CT fusion technique if information on the electron density within the vertebral body is available to generate …