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Updated: May 31, 2025
Radiotracer Administration for High Temporal Resolution Positron Emission Tomography of the Human Brain: Application to FDG-fPET
Published on: October 22, 2019
Validation of a Monte Carlo-based dose calculation engine including the 1.5 T magnetic field for independent
Ruggero Ruggieri1, Nicola Bianchi1, Davide Gurrera1
1Department of Radiation Oncology, IRCCS Sacro Cuore Don Calabria Hospital, Via Don A. Sempreboni 5, 37024 Negrar di Valpolicella, VR, Italy.
Purpose:
Adaptive MRgRT by 1.5 T MR-linac requires independent verification of the plan-of-the-day by the primary TPS (MonacoTM) (M). Here we validated a Monte Carlo-based dose-check including the magnetostatic field, SciMoCaTM (S).
Methods:
M and S were validated first in water, by comparison with commissioning-dosimetry. PDD(2x2cm2) through a lung(air)-equivalent virtual-slab was then calculated. Clinical validation retrospectively included 161 SBRT plans, from five patients per-site: Pelvic-Nodes, Prostate, Liver, Pancreas, and Lungs. S-minus-M percentage differences (Δ%) were computed for target- and OARs-related dose-volume metrics. In-phantom dose verification per-patient was performed.
Results:
γ(2 %,1mm)-passing-rates (PR%) of in-water-computed PDD and transverse-dose-profiles vs. commissioning-dosimetry were (99.1 ± 2.0)% for M, and (99.3 ± 1.5)% for S. Calculated output-factors (OF) were typically within 1 % from measurements, except for OF(1x1cm2) which was misestimated by -4.4 % and + 2.2 %, by M and S respectively. Dose spikes (valleys) on the PDD(2x2cm2) by S across the lung-equivalent virtual-slab were slightly reduced with respect to M. In clinical plans, S computed higher V95% (p <0.05*, for pancreas and lung) and D2% (p <0.05*, for all sites) for the target, while D%>2% resulted for duodenal D(1cm3), in Pancreas-SBRT, and for mean-lung-dose, in Lung-SBRT. All mostly due to the underestimated OF(1x1cm2) by M. In-phantom dose verifications showed an average 1% increase in PR% by S vs. M.
Conclusions:
Beam-model quality in S resulted equivalent to M, thus making S useful both for an independent validation of the same beam-model in M, and for a daily validation of the M-based online approval decisions, without significantly delaying the clinical workflow (2-3 min).
