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Session: Treatment Planning [Return to Session]

Validation of the Monte Carlo Algorithm in RadianceTM Treatment Planning System Based On the BEAMnrc/ EGSnrc Built Model of the Mobetron Intraoperative Linear Accelerator

Division of Medical Physics, Department of Radiation Oncology, University Medical Center Freiburg, Freiburg, Germany German Cancer consortium (DKTK), Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg , Germany


MO-E115-IePD-F7-1 (Monday, 7/11/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: To validate the Monte Carlo (MC) dose calculation algorithm as implemented in Radiance™, version 4.0.8, a dedicated TPS for electron dose calculations in IOERT with a Mobetron intraoperative linear accelerator (linac) by comparing to BEAMnrc built model.

Methods: The MC models were generated using water relative dose measurements. Electron beams of Mobetron linac were collimated by plastic, X-ray imaging compatible, applicators of diameter sizes from 5cm to 9cm. Depth dose curves and dose profiles were compared with 1D gamma analysis in various set-ups of virtual water phantoms with air and bone heterogeneities. 3D image volumes of an anthropomorphic pelvic phantom acquired with a CT scanner (Philips Big Bore CT) and an Imaging Ring CBCT system (medPhoton, Austria) for dose calculations with identical treatment parameters in the two MC systems. A C# script was written to import the EGSnrc output files into Eclipse™ v15.6 TPS and convert them into RT dose files, so that 3D gamma analysis was enabled with the PTW VeriSoft Software v8. 2%/2mm and 3%/3mm gamma criteria with global normalization, were applied for the commissioning of the two beam models and their comparisons respectively.

Results: Commissioning of the BEAMnrc model required optimization of the thickness of the secondary scattering foil. Radiance™ model showed discrepancies with the measured data in surface doses and in the umbra region. Radiance™ underestimated the dose at the field edges of the 6MeV dose profiles with bone inhomogeneity. In air inserts, the computational noise increased, while calculation uncertainties were lower than 1%. In 3D dose comparisons, higher than 90% gamma passing rates were achieved for both imaging systems demonstrating that differences observed in 1D comparisons have no clinical significance.

Conclusion: Radiance™ TPS has a reliable implemented MC algorithm for clinical use in IOERT in the framework of image based treatment planning and delivery.


Electron Therapy, Image-guided Therapy, IORT


TH- External Beam- Electrons: intraoperative

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