S1892
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Digital Poster 2652 Microbeam Radiotherapy on the road to clinical application – What to treat first? Kim Melanie Kraus 1,2 , Liam Day 1,2 , Stefan Bartzsch 1,2 , Jan Jakob Wilkens 1 , Stephanie Elisabeth Combs 1,2 1 Radiation Oncology, Technical University of Munich, Munich, Germany. 2 Institute of Radiation Medicine (IRM), Helmholtz Center Munich, Neuherberg, Germany Purpose/Objective: Microbeam Radiotherapy (MRT) is a novel radiation dose delivery technique with spatially fractionated beams on a micrometre scale moving forward towards clinical application. Preclinical results have proven remarkably improved sparing of healthy tissue without limiting tumor control. A first clinical phase 1 study needs to proof safe application of MRT, however, up to date it is unclear which targets to treat. This work aims to identify dosimetrically feasible and clinically relevant treatment cases. Material/Methods: Treatment plans were generated using an MRT dose calculation algorithm [1] with two treatment fields, implemented in a research version of Eclipse (Varian Medical Systems, Palo Alto, CA) [2]. Beam characteristics of a novel compact x-ray source [3] were used. A 300 kVp photon beam was collimated into 50 µm wide beamlets with 400 µm centre-to- centre distances and blocked by a target conforming digital mask for each of the two fields. An EUD of 3 Gy was prescribed so that 95% of the dose covers 95% of the CTV. DVHs and the peak-to-valley-dose-ratio (PVDR) were calculated for dosimetric evaluation. Nine patient cases were carefully selected considering the following criteria:Palliative radiotherapy treatment indication with potential benefit from MRTMeasurable and limited side effects from radiationNo potentially interfering therapyReproducible and safe patient positioningSuperficial target location Results:
The best combination of target coverage and dose sparing to surrounding OARs was achieved by two gluteal tumors (Table 1, Figure 1). Dose distributions were inhomogeneous. Target coverage in terms of D95% ranged from 95.4% to 105.8% of the prescribed dose. Minimum doses ranged between 0 and 1.9 Gy (cases of 0 Gy minimum dose were due to air within the target). Maximum doses exceeded 6 Gy for all cases, however, D2% was below 6 Gy for the majority of cases. For OARs and CTVs involving bone, maximum doses exceeded 6 Gy due to the interactions of kV radiation in high density tissue. Cumulative peak and valley doses ranged from 29.7 Gy – 71.3 Gy and 2.4 – 7.5 Gy, respectively. PVDRs in the isocenter were between 9.3 and 21.1. Exemplary dose distributions, EUD and PVDR depth curves are shown in Figure 1 for a gluteal DLBCL.. Conclusion: Microbeams can deliver dosimetrically safe and effective dose distributions to clinically relevant patient cases. For a first clinical safety trial, superficial targets without large tissue inhomogeneities might be a suitable target with regard to dosimetry.
References: [1]
M. Donzelli et al., Phys Med Biol 63, 045013
(2018).[2]
L. R. J. Day et al., Phys Med Biol 66,
055016 (2021).[3]
C. Matejcek et al., Phys Med 106,
102532 (2023). Keywords: SFRT, Microbeam Radiotherapy, Treatment Planning
Made with FlippingBook - Share PDF online