The Influence of Motion on the Delivery Accuracy When Comparing Actively Scanned Carbon Ions versus Protons at a Synchrotron-Based Radiotherapy Facility

Lebbink, Franciska; Georg, Dietmar; Knäusl, B.

doi:10.3390/cancers14071788

Cited by 10 publications

(11 citation statements)

References 37 publications

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“…As all our 4D dose comparisons, however, relied on the same data sets we believe our findings would also be transferable to real 4D patient data. Further, a dosimetric study in an anthropomorphic thorax phantom with a moving target did not show any significant difference with and without moving ribs (Lebbink et al 2022).…”

Section: Discussionmentioning

confidence: 80%

Limitations of phase-sorting based pencil beam scanned 4D proton dose calculations under irregular motion

et al. 2022

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Objective. 4D dose calculation (4DDC) for pencil beam scanned (PBS) proton therapy is typically based on phase-sorting of individual pencil beams onto phases of a single breathing cycle 4DCT. Understanding the dosimetric limitations and uncertainties of this approach is essential, especially for the realistic treatment scenario with irregular free breathing motion. Approach. For three liver and three lung cancer patient CTs, the deformable multicycle motion from 4DMRIs was used to generate six synthetic 4DCT(MRI)s, providing irregular motion (11/15 cycles for liver/lung; tumor amplitudes ∼4-18 mm). 4DDCs for two-field plans were performed, with the temporal resolution of the pencil beam delivery (4-200 ms) or with 8 phases per breathing cycle (500-1000 ms). For the phase sorting approach, the tumor center motion was used to determine the phase assignment of each spot. The dose was calculated either using the full free breathing motion or individually repeating each single cycle. Additionally, the use of an irregular surrogate signal prior to 4DDC on a repeated cycle was simulated. The CTV volume with absolute dose differences > 5% (Vdosediff>5%) and differences in CTV V95% and D5%-D95% compared to the free breathing scenario were evaluated. Main results. Compared to 4DDC considering the full free breathing motion with finer spot-wise temporal resolution, 4DDC based on a repeated single 4DCT resulted in Vdosediff>5% of on average 34%, which resulted in an overestimation of V95% up to 24%. However, surrogate based phase-sorting prior to 4DDC on a single cycle 4DCT, reduced the average Vdosediff>5% to 16% (overestimation V95% up to 19%). The 4DDC results were greatly influenced by the choice of reference cycle (Vdosediff>5% up to 55%) and differences due to temporal resolution were much smaller (Vdosediff>5% up to 10%). Significance. It is important to properly consider motion irregularity in 4D dosimetric evaluations of PBS proton treatments, as 4DDC based on a single 4DCT can lead to an underestimation of motion effects.

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Section: Discussionmentioning

confidence: 80%

Limitations of phase-sorting based pencil beam scanned 4D proton dose calculations under irregular motion

et al. 2022

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“…The observed difference can have several reasons, one of them being related to the size of the target volume making the ionization chamber partially move out of the beam, especially for the largest input breathing amplitude used. In addition, a larger dispersion in these measurements was obtained, probably caused by dose rate changes, directly influencing the accuracy of the chamber measurements, as reported by Lebbink et al (2022) for carbon ion irradiation during motion. Furthermore, the breathing motion in PPIeT was not synchronized with the beam delivery leading to a possible interplay effect between each single beam spot position and the chamber position (Bert et al 2008, Bert and Durante 2011, Dolde et al 2019b.…”

Section: Carbon Ion Treatment Of Ppietmentioning

confidence: 84%

“…To cover this wide range of pancreatic movement observed in patients, breathinginduced motion from 3.98 to 18.19 mm was studied with PPIeT. Smaller displacements were not studied since their influence on dose delivery is expected to be mostly neglectable (Lebbink et al 2022). Since it was possible to linearly correlate the fixed input displacement to the displacement of each organ, any desired organ motion can be achieved.…”

Section: Phantom Motionmentioning

confidence: 99%

“…Other authors presented a Magnetic Resonance Image-Guided Radiotherapy dynamic lung motion thorax anthropomorphic QA phantom (Steinmann et al 2019) as well as an anthropomorphic phantom developed for deformable lung and liver studies, which (Colvill et al 2020) have tackled the increasing need for MRI-compatible phantoms (Colvill et al 2020). One other phantom to be named is the Advanced Radiation DOSimetry phantom (ARDOS) which incorporates a moving rigid ribcage and can be used to measure dose during ion beam therapy (Kostiukhina et al 2017, Kostiukhina et al 2020, Lebbink et al 2022. Additionally, an anthropomorphic thorax breathing phantom was developed specifically for pencil beam scanning proton therapy (Perrin et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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A phantom to simulate organ motion and its effect on dose distribution in carbon ion therapy for pancreatic cancer

Stengl,

Panow,

Arbes

et al. 2023

Phys. Med. Biol.

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Objective: Carbon ion radiotherapy is a promising radiation technique for malignancies like pancreatic cancer. However, organs’ motion imposes challenges for achieving homogeneous dose delivery. In this study, an anthropomorphic Pancreas Phantom for Ion-beam Therapy (PPIeT) was developed to simulate breathing and gastrointestinal motion during radiotherapy.Approach: The developed phantom contains a pancreas, two kidneys, a duodenum, a spine and a spinal cord. The shell of the organs was 3D printed and filled with agarose-based mixtures. Hounsfield Units (HU) of PPIeTs’ organs were measured by CT. The pancreas motion amplitude in cranial-caudal (CC) direction was evaluated from patients’ 4D CT data. Motions within the obtained range were simulated and analyzed in PPIeT using MRI. Additionally, GI motion was mimicked by changing the volume of the duodenum and quantified by MRI. A patient-like treatment plan was calculated for carbon ions, and the phantom was irradiated in a static and moving condition. Dose measurements in the organs were performed using an ionization chamber and dosimetric films.Main results: PPIeT presented tissue equivalent HU and reproducible breathing-induced CC displacements of the pancreas between (3.98±0.36) mm and a maximum of (18.19±0.44) mm. The observed maximum change in distance of (14.28±0.12) mm between pancreas and duodenum was consistent with findings in patients. Carbon ion irradiation revealed homogenous coverage of the virtual tumor at the pancreas in static condition with a 1 % deviation from the treatment plan. Instead, the dose delivery during motion with the maximum amplitude yielded an underdosage of 21 % at the target and an increased uncertainty by two orders of magnitude. Significance: A dedicated phantom was designed and developed for breathing motion assessment of dose deposition during carbon ion radiotherapy. PPIeT is a unique tool for dose verification in the pancreas and its organs at risk during end-to-end tests.

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“…Especially for pencil beam scanned (PBS) proton therapy, the interplay between the patient's motion and the dynamic beam delivery can result in complex dose degradation with dose inhomogeneities occurring within the target (Phillips et al 1992, Bert et al 2008. Using 4D dose calculations (4DDC), the dosimetric effects of motion on the planned dose distributions have been comprehensively investigated in various simulation studies (Bert et al 2008, Seco et al 2009, Zhang et al 2012, Grassberger et al 2013, Ammazzalorso and Jelen 2014, Zou et al 2014, Batista et al 2018, Dolde et al 2019, Meijers et al 2020, Steinsberger et al 2021, Lebbink et al 2022. The effectiveness of different motion mitigation techniques, such as breath hold, beam gating, rescanning and tracking, have also been analyzed extensively (Li et al 2006, Bert and Rietzel 2007, Knopf et al 2011, Grassberger et al 2015, Zhang et al 2015, Gorgisyan et al 2017, Ishihara et al 2017, Engwall et al 2018, Dolde et al 2019, Gorgisyan et al 2019.…”

Section: Introductionmentioning

confidence: 99%

A motion model-guided 4D dose reconstruction for pencil beam scanned proton therapy

et al. 2023

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Objective. 4D dose reconstruction in proton therapy with pencil beam scanning (PBS) typically relies on a single pre-treatment 4DCT (p4DCT). However, breathing motion during fractionated treatment can vary considerably in both amplitude and frequency. We present a novel 4D dose reconstruction method combining delivery log-files with patient-specific motion models, to account for the dosimetric effects of intra- and inter-fractional breathing variability.Approach. Correlation between an external breathing surrogate and anatomical deformations of the p4DCT is established using principal component analysis. Using motion trajectories of a surface marker acquired during dose delivery by an optical tracking system, deformable motion fields are retrospectively reconstructed and used to generate time-resolved synthetic 4DCTs (’5DCTs’) by warping a reference CT. For three abdominal/thoracic patients, treated with respiratory gating and rescanning, example fraction doses were reconstructed using the resulting 5DCTs and delivery log files. The motion model was validated beforehand using leave-one-out cross-validation (LOOCV) with subsequent 4D dose evaluations. Moreover, besides fractional motion,fractional anatomical changes were incorporated as proof of concept. Main results. For motion model validation, the comparison of 4D dose distributions for the original 4DCT and predicted LOOCV resulted in 3%/3 mm gamma pass rates above 96.2%. Prospective gating simulations on the p4DCT can overestimate the target dose coverage V95% by up to 2.1% compared to 4D dose reconstruction based on observed surrogate trajectories. Nevertheless, for the studied clinical cases treated with respiratory-gating and rescanning, an acceptable target coverage was maintained with V95% remaining above 98.8% for all studied fractions. For these gated treatments, larger dosimetric differences occurred due to CT changes than due to breathing variations.Significance. To gain a better estimate of the delivered dose, a retrospective 4D dose reconstruction workflow based on motion data acquired during PBS proton treatments was implemented and validated, thus considering both intra- and inter-fractional motion and anatomy changes.

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The Influence of Motion on the Delivery Accuracy When Comparing Actively Scanned Carbon Ions versus Protons at a Synchrotron-Based Radiotherapy Facility

Cited by 10 publications

References 37 publications

Limitations of phase-sorting based pencil beam scanned 4D proton dose calculations under irregular motion

Limitations of phase-sorting based pencil beam scanned 4D proton dose calculations under irregular motion

A phantom to simulate organ motion and its effect on dose distribution in carbon ion therapy for pancreatic cancer

A motion model-guided 4D dose reconstruction for pencil beam scanned proton therapy

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