Abstract
The aim was the validation of a platform for internal dosimetry, named MCID, based on patient-specific images and direct Monte Carlo (MC) simulations, for radioembolization of liver tumors with 90Y-labeled microspheres. CT of real patients were used to create voxelized phantoms with different density and activity maps. SPECT acquisitions were simulated by the SIMIND MC code. Input macros for the GATE/Geant4 code were generated by MCID, loading coregistered morphological and functional images and performing image segmentation. The dosimetric results obtained from the direct MC simulations and from conventional MIRD approach at both organ and voxel level, in condition of homogeneous tissues, were compared, obtaining differences of about 0.3% and within 3%, respectively, whereas differences increased (up to 14%) introducing tissue heterogeneities in phantoms. Mean absorbed dose for spherical regions of different sizes (10 mm ≤ r ≤ 30 mm) from MC code and from OLINDA/EXM were also compared obtaining differences varying in the range 7–69%, which decreased to 2–9% after correcting for partial volume effects (PVEs) from imaging, confirming that differences were mostly due to PVEs, even though a still high difference for the smallest sphere suggested possible source description mismatching. This study validated the MCID platform, which allows the fast implementation of a patient-specific GATE simulation, avoiding complex and time-consuming manual coding. It also points out the relevance of personalized dosimetry, accounting for inhomogeneities, in order to avoid absorbed dose misestimations.
Highlights
Radioembolization (RE) is a clinical therapy for the treatment of primary or secondary hepatic tumors
We developed this scenario in order to compare the average absorbed dose for each sphere obtained from the GATE output with that obtained from OLINDA-EXM [39] S-factor for 90Y and spheres of soft tissues with unit density
The drastic impact of partial volume effects (PVEs) is evidenced by the results obtained without the SIMIND simulation: for the BS and the MS, relative difference (RD) reduced to 2% and 3%, respectively, while for the SS, RD reduced to 9%
Summary
Radioembolization (RE) is a clinical therapy for the treatment of primary or secondary hepatic tumors. Empirical and dosimetric, have been proposed to establish the activity to be administered [2]. Due to their simplicity, empirical models have been applied for several years, but at present they are not considered as adequate for patient-specific treatments. The clinical benefit evidence of dosimetry-based approaches [3,4,5,6,7,8,9,10] has led the scientific community to recognize the importance of accurate absorbed dose evaluation and to focus on the absorbed dose–biological effectiveness relationship
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
