Monte Carlo based beam model using a photon MLC for modulated electron radiotherapy

Abstract

The results of the dose comparisons suggest that the developed beam model is suitable to accurately reconstruct photon MLC shaped electron beams for a Clinac 23EX and a TrueBeam linac. Hence, in future work the beam model will be utilized to investigate the possibilities of MERT using the photon MLC to shape electron beams.

Part 2: Dynamic mixed beam radiotherapy (DYMBER): Photon dynamic trajectories combined with modulated electron beams

“…The resulting SSD is typically in the range of 70–82.5 cm. The opening of the secondary collimator jaws is set fixed to 15 × 35 cm 2 for each electron field as required by the utilized beam model for dose calculation . In this work, the gantry angles are chosen such that each part of the PTV could be covered by at least one electron field with a perpendicular incidence angle.…”

“…The final and beamlet dose distributions are calculated using SMCP integrated beam models and dose calculation algorithms VMC++ (photon beams) and macro MC (electron beams). Measured and calculated dose distributions of single fields generally agree within 2% dose difference (global) or 1 mm distance to agreement for photon beams and 3% dose difference (global) or 2 mm distance to agreement for electron beams .…”

“…The opening of the secondary collimator jaws is set fixed to 15 9 35 cm 2 for each electron field as required by the utilized beam model for dose calculation. 36 In this work, the gantry angles are chosen such that each part of the PTV could be covered by at least one electron field with a perpendicular incidence angle. However, the maximal number of electron beam directions is currently limited to three such that delivery time is not inappropriately prolonged due to the corresponding isocenter changes.…”

Beamlet based direct aperture optimization for MERT using a photon MLC

“…Basically, there is either the possibility of using a dedicated electron collimation device [electron multileaf collimator (eMLC), [16][17][18] few leaf electron collimator (FLEC) 19 ] or using the photon multileaf collimator (pMLC). 7,8,20,21 In contrast to the dedicated devices which have to be mounted and dismounted and maintained, which needs additional effort, the pMLC is already part of most linear accelerators and using it for electrons would only require minor additional work in clinical routine. However, no matter which collimation device is used, MERT requires dedicated machine QA and a patient specific pretreatment QA procedure.…”

Forward treatment planning for modulated electron radiotherapy (MERT) employing Monte Carlo methods

“…As currently no commercially available treatment planning system (TPS) incorporates the possibility to calculate electron fields shaped by a pMLC, a MC based beam model 22 was developed that accurately reconstructs the pMLC collimated electron beam. However, in order to apply the forward planning process on a large scale, the MC part of this beam model had to be made more efficient by substantially improving the transport of electrons through the pMLC, which is the main factor regarding the computation time of the beam model.…”