Room: AAPM ePoster Library
Purpose: For many years, Yttrium-90 (Y-90) microsphere radio-embolization has been a standard of care for the treatment of liver metastasis and liver cancer. Several commercial software packages are now available that perform post-implant dosimetry. In order to fully rely on new software for dosimetry, it is necessary to do extensive benchmarking tests with established dose calculation algorithms. This work validates MIM-SurePlan software by comparing its results to a previously developed MonteCarlo derived voxel dose kernel calculation.
Methods: Ten patients who had lobar or whole liver treatments for metastatic liver cancer were analyzed. Contours were created on post Y90 treatment PET-CT images. We then performed dose calculations using two methods and compared the results. The first calculation convolves the activity density distribution from PET-CT images with a voxel dose kernel of a Y-90 source, generated by Fluka MonteCarlo simulation. The second method calculates the dose using MIM-SurePlan’s DPK (Dose Point Kernel) algorithm. 3D Gamma passing rates and several dosimetric parameters were investigated.
Results: 3%3mm 3D gamma passing rates averaged 96.4% (range 89.4-99.6%). The combined target GTV (the patients’ Boolean-algebra union of all lesions) V70Gy differences averaged 2.9% (range 0.1-7.2). The differences in normal whole liver or normal target lobe mean dose averaged 1.7% (range 0-4%). Larger differences were seen in GTV mean doses (mean 7.5%, range 0.8-16.4%) and Dmax (mean 7%, range 1.4-25.7%) likely due to large dose gradients in the treated regions combined with differences in the dose kernel scaling and dose grid differences between calculations.
Conclusion: The MIM-SurePlan algorithm agreed well with the MonteCarlo based calculation for patients treated with Y90 microspheres based on the gamma analysis and several dosimetric parameters. Larger dosimetric differences in lesion mean doses and D1% suggests that these metrics are less robust to changes in calculation grid location and size.