Clinical implementation of combined modulated electron and photon beams with conventional MLC for accelerated partial breast irradiation

Míguez, Carlos; Jiménez-Ortega, Elisa; Palma, Bianey; Miras, Héctor; Ureba, Ana; Arráns, R.; Carrasco-Peña, Francisco; Illescas-Vacas, A.; Leal, Antonio

doi:10.1016/j.radonc.2017.06.011

Cited by 14 publications

(17 citation statements)

References 23 publications

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“…It has been shown that using the conventional photon multileaf collimator (pMLC) for clinical electron beams at reduced source to surface distances (SSD) can replace treatment plans using cumbersome and inefficient cut-out collimation with similar plan quality for today's standard electron treatments [12]. Alongside advantages in efficiency and quality assurance, using the pMLC for electron beam collimation also allows for advanced treatment techniques like modulated electron radiotherapy (MERT) [13][14][15][16], or the combination of photon and electron beams in mixed beam radiotherapy (MBRT) [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Towards MR-guided electron therapy: Measurement and simulation of clinical electron beams in magnetic fields

et al. 2020

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In the current era of MRI-linac radiotherapy, dose optimization with arbitrary dose distributions is a reality. For the first time, we present new and targeted experiments and modeling to aid in evaluating the potential dose improvements offered with an electron beam mode during MRI-linac radiotherapy. Methods: Small collimated (1 cm diameter and 1.5 × 1.5 cm 2 square) electron beams (6, 12 and 20 MeV) from a clinical linear accelerator (Varian Clinac 2100C) are incident perpendicular and parallel to the strong and localized magnetic fields (0-0.7 T) generated by a permanent magnet device. Gafchromic EBT3 film is placed inside a slab phantom to measure two-dimensional dose distributions. A benchmarked and comprehensive Monte Carlo model (Geant4) is established to directly compare with experiments. Results: With perpendicular fields a 5% narrowing of the beam FWHM and a 10 mm reduction in the 15% isodose penetration is seen for the 20 MeV beam. In the inline setup the penumbral width is reduced by up to 20%, and a local central dose enhancement of 100% is observed. Monte Carlo simulations are in agreement with the measured dose distributions (2% or 2 mm). Conclusion: A new range of experiments have been performed to offer insight into how an electron beam mode could offer additional choices in MRI-linac radiotherapy. The work extends on historic studies to bring a successful unified experimental and Monte Carlo modeling approach for studying small field electron beam dosimetry inside magnetic fields. The results suggest further work, particularly on the inline magnetic field scenario.

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Section: Introductionmentioning

confidence: 99%

Towards MR-guided electron therapy: Measurement and simulation of clinical electron beams in magnetic fields

et al. 2020

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“…By delivering MERT plans with a standard photon MLC, the potential arises for seamless mixed electron–photon delivery without interrupting treatment delivery between modality changes. Indeed, mixed‐beam electron–photon radiotherapy (MBRT) plans have been shown to offer additional degrees of freedom to influence the trade‐off between normal tissue dose and target coverage …”

Section: Introductionmentioning

confidence: 99%

Robust mixed electron–photon radiation therapy optimization

2019

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Purpose Mixed beam electron–photon radiation therapy (MBRT) is an emerging technique that has the potential to reduce dose to normal tissue while improving target coverage for cancer sites with superficial tumors. Advances in optimization algorithms and robotic linear accelerators have made the creation and delivery of complex MBRT plans realistic without the need for special additional collimators, devices, or resetup of the patient. However, no study has been performed on the robustness of MBRT dose distributions to patient setup errors. Intensity‐modulated delivery of other charged particles such as protons have been shown to require robust planning techniques to maintain adequate target coverage under positioning errors. We therefore assess the sensitivity of MBRT treatment plans to positioning uncertainties when created under the traditional planning target volume (PTV)‐based planning paradigm and present a novel optimization model for the creation of robust MBRT plans. Methods The column generation method was applied to robust MBRT treatment planning by deriving the pricing problem for stochastic and “worst case” minimax optimization models, two common formulations of robustness. Robust treatment plans were created for two patient cases representative of the cancer sites which stand to benefit from MBRT: soft tissue sarcoma (STS) irradiation and chest wall irradiation with deep‐seated internal mammary, axillary, and supraclavicular nodes (CW‐N). For both patient cases, beamlet dose distributions for electrons and photons were generated for positioning shifts in six directions, ±5mm(xfalse^,yfalse^,zfalse^) in addition to a nominal unshifted scenario, for a total of seven sets of beamlets. Robust plans were created by specifying dose coverage constraints to the clinical target volume (CTV), as opposed to the PTV. Comparisons were performed against traditional PTV‐based plans created with a single set of unshifted beamlets. Results The dose distributions of traditional PTV‐based MBRT plans showed significant degradation in target coverage homogeneity when patient positioning errors were considered. For both cancer sites, cold spots below 95% and hot spots above 108% of the prescription dose appeared within the CTV when shifting the patient by 5 mm, corresponding to the margin added to the CTV to form the PTV. In contrast, CTV‐based robust plans created with the new optimization model maintained target coverage within the 95%–108% limits, for all positioning errors. Conclusion The quality of MBRT treatment plans created using a traditional PTV‐based optimization model was highly sensitive to patient positioning errors. For both patient cases, positioning errors resulted in perturbations to the nominal dose distributions which would have rendered PTV‐based plans clinically unacceptable. In contrast, CTV‐based robust plans were able to maintain adequate target coverage under all positioning error scenarios considered. We therefore conclude that to ensure the fidelity of the dose distribution delivered to the pat...

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“…Superficial targets up to a depth of 5 cm could be treated with a homogeneous dose coverage. If photon beams are added to electron beams, called mixed beam radiotherapy (MBRT), 16,[23][24][25][26][27][28][29][30][31][32][33] then this restriction in the target depth is removed. It was shown for targets with at least some superficial part that treatment plan quality of coplanar step and shoot MBRT plans with simultaneously optimized photon and electron beams is substantially improved compared to IMRT and VMAT plans, because of the additional DoF of two different particle types.…”

Section: Introductionmentioning

confidence: 99%

“…M ıguez et al demonstrated this for accelerated partial breast irradiations with promising clinical results. 31 In the research field of MBRT, photon beams are neither applied with any dynamic gantry, table, or collimator rotations nor in a noncoplanar field setup. Thus, there is still unexplored potential to improve treatment plan quality and efficiency of MBRT.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Clinical implementation of combined modulated electron and photon beams with conventional MLC for accelerated partial breast irradiation

Abstract: Results showed that MERT+IMRT with the MLC is a feasible and secure technique, and easy to be extended to other centers with the implementation of the adequate software for planning.

Cited by 14 publications

References 23 publications

Towards MR-guided electron therapy: Measurement and simulation of clinical electron beams in magnetic fields

Towards MR-guided electron therapy: Measurement and simulation of clinical electron beams in magnetic fields

Robust mixed electron–photon radiation therapy optimization

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

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