3D-Personalized Monte Carlo Dosimetry in 90Y-Microspheres Therapies of Primary and Secondary Hepatic Cancers: Absorbed Dose and Biological Effective Dose Considerations
A Petitguillaume1*, M Bernardini2, C Michel1, C de Labriolle-Vaylet3, D Franck1, A Desbree1, (1) Institut de Radioprotection et de Surete Nucleaire (IRSN), Fontenay-aux-roses, FRANCE, (2) Hopital Europeen Georges Pompidou (HEGP), Paris, FRANCE, (3) UPMC Paris 06 Biophysics, Paris, FRANCESU-E-T-500 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To develop and evaluate a 3D-Personalized Monte Carlo Dosimetry (PMCD) for treatment planning in 90Y-microspheres therapies of unresectable hepatic cancers.
Methods: The PMCD method was evaluated from the 99mTc-MAA distribution of 20 patients treated for hepatic metastases or hepatocellular carcinoma. Using the OEDIPE software, regions of interest outlines, drawn on CT images, were used to create patient-specific voxel phantoms and 99mTc-MAA SPECT data were used to generate 3D-matrices of cumulated activity. Absorbed doses and BED at the voxel scale were calculated using the MCNPX Monte Carlo transport code. OEDIPE was used to determine the maximum injectable activity (MIA) for tolerance criteria on organs at risk (OARs), i.e. the lungs and non tumoral liver (NTL). Tolerance criteria based on mean absorbed doses, mean BED (Biological Effective Dose), Dose-Volume Histograms (DVHs) or BED-Volume Histograms (BVHs) were considered. Those MIAs were compared to the ones recommended by conventional methods: the Body Surface Area (BSA) method and the Partition Model with tolerance criteria on mean absorbed doses.
Results: Compared to Partition Model recommendations, performing dosimetry using the PMCD method enables to increase the activity prescription while ensuring OARs radiation protection. Moreover, considering tolerance criteria based on DVHs further enhances treatment planning efficiency by taking advantage of the parallel characteristic of the liver and the lungs whose functions are not impaired if the level of irradiation to a fraction of the organ is kept sufficiently low. Finally, tolerance criteria on mean BED and BVHs further improve treatment planning by taking into account biological considerations such as cell repair, radiosensibility or dose-rate distribution.
Conclusion: Besides its feasibility and applicability in clinical routine, the interest of a personalized Monte Carlo dosimetry for treatment planning in 90Y-microspheres therapies was confirmed from those patient studies.