Validation of a model for physical dose variations in irregularly moving targets treated with carbon ion beams

Meschini, Giorgia; Seregni, Matteo; Molinelli, S.; Vai, A.; Phillips, J.; Sharp, G; Pella, Andrea; Valvo, Francesca; Ciocca, Mario; Riboldi, Marco; Paganetti, Harald; Baroni, Guido

doi:10.1002/mp.13662

Cited by 10 publications

(19 citation statements)

References 37 publications

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“…The applied method, which does not need time-resolved imaging, being based on reference 3D CT and dose distribution, allowed us to estimate with appropriate accuracy the 4D RWD. Indeed, for all simulations the median estimation error on D 5% and D 95% was ≤5%, obtaining results comparable to Meschini et al 18 In the patient study, a clinically acceptable plan was optimized, with a robust beam configuration 44 and proper tumor margins. 21,24 Simulations entailed irradiation during free breathing in order to evaluate the bioWED method in unfavorable conditions, although in carbon ion therapy pancreatic patients are usually treated with the gating technique combined with other motion mitigation strategies.…”

Section: Discussionsupporting

confidence: 78%

“…For each considered respiratory phase

φ

, the

{d_{p, φ}|}_{EE}

{α_{p, φ}|}_{EE}

, and

{β_{p, φ}|}_{EE}

maps were used to estimate with the bioWED method the

d_{p, φ}

α_{p, φ}

, and

β_{p, φ}

needed for

italicRBE

estimation, as previously done for physical dose estimations 17,18 . Specifically, both the planning end‐exhale CT and the maps were transformed in the beam‐ and patient‐specific WED‐space and translated according to tumor motion.…”

Section: Methodsmentioning

confidence: 99%

“…The mean RWD difference over the whole volume was computed as well, considering only nonzero dose voxels. Table I lists DEUD GT;PLAN and DEUD GT;WED for both the gross target volume (GTV) and the ITV: in the small gating window simulation, the motion impact was null and the corresponding median estimation error, which was due to the information loss during interpolation in the WED-space, 17,18 was lower that 1%; in the large gating window and the free breathing simulation, the estimation error was smaller than the motion effect. The 4D dose computation (GT) presented an increasing degradation of the static plan from the small gating window to the free breathing irradiation simulation (DVH in Fig.…”

Section: E3 Evaluated Metricsmentioning

confidence: 99%

“…Currently, it is not possible to evaluate the treatment plan robustness for RBE‐weighted dose distributions in the presence of irregular breathing motion, when proper imaging data are not available for dose computation. In this study, we significantly extend the method described by Meschini et al 18 for application in carbon ion therapy of abdominal lesions. This is achieved by integrating: (a) the modeling of RBE‐weighted dose variations based on breathing motion simulation in the WED‐space with embedded radiobiological models (referred to as bioWED method); (b) the application to pencil beam scanned (PBS) carbon ion therapy with 4D dynamic dose delivery, thus studying the capability of the bioWED method to estimate complex dose distribution including the interplay effect; (c) an approach based on image‐based respiratory motion modeling 15,20 to simulate irregular breathing motion, thus extending patient data variability.…”

Section: Introductionmentioning

confidence: 97%

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Modeling RBE‐weighted dose variations in irregularly moving abdominal targets treated with carbon ion beams

et al. 2020

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To model four-dimensional (4D) relative biological effectiveness (RBE)-weighted dose variations in abdominal lesions treated with scanned carbon ion beam in case of irregular breathing motion. Methods: The proposed method, referred to as bioWED method, combines the simulation of tumor motion in a patient-and beam-specific water equivalent depth (WED)-space with RBE modeling, aiming at the estimation of RBE-weighted dose changes due to respiratory motion. The method was validated on a phantom, simulating gated and free breathing dose delivery, and on a patient case, for which free breathing irradiation was assumed and both amplitude and baseline breathing irregularities were simulated through a respiratory motion model. We quantified (a) the effect of motion on the equivalent uniform dose (EUD) and the RBE-weighted dose-volume histograms (DVH), by comparing the planned dose distribution with "ground truth" 4D RBE-weighted doses computed using 4D computed tomography data, and (ii) the estimation error, by comparing the doses estimated with the bioWED method to "ground truth" 4D RBE-weighted doses. Results: In the phantom validation, the estimation error on the EUD was limited with respect to the motion effect and the median estimation error on relevant RBE-weighted DVH metrics remained within 5%. In the patient study, the estimation error as computed on the EUD was smaller than the corresponding motion effect, exhibiting the largest values in the baseline irregularity simulation. However, the median estimation error over all simulations was below 3.2% considering relevant DVH metrics. Conclusions: In the evaluated cases, the bioWED method showed proper accuracy when compared to deformable image registration-based 4D dose calculation. Therefore, it can be seen as a tool to test treatment plan robustness against irregular breathing motion, although its accuracy decreases as a function of increasing soft tissue deformation and should be evaluated on a larger patient dataset.

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Section: Discussionsupporting

confidence: 78%

“…For each considered respiratory phase

φ

, the

{d_{p, φ}|}_{EE}

{α_{p, φ}|}_{EE}

, and

{β_{p, φ}|}_{EE}

maps were used to estimate with the bioWED method the

d_{p, φ}

α_{p, φ}

, and

β_{p, φ}

needed for

italicRBE

Section: Methodsmentioning

confidence: 99%

Section: E3 Evaluated Metricsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Modeling RBE‐weighted dose variations in irregularly moving abdominal targets treated with carbon ion beams

et al. 2020

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“…For the abdominal site, motion correlated treatment planning relies on a 4DCT with four respiratory phases: the endexhale, used for plan optimization; the 30%-exhale and 30%inhale, to test the plan against residual motion within the gating window; the end-inhale, to assess the total range of motion. 34,35 The MRI scan was performed on the same day of the 4DCT acquisition. For 4 of the eight patients, two 4DMRI were acquired within the same session.…”

Section: B Patient Datasetmentioning

confidence: 99%

Virtual 4DCT from 4DMRI for the management of respiratory motion in carbon ion therapy of abdominal tumors

et al. 2020

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Purpose To evaluate a method for generating virtual four‐dimensional computed tomography (4DCT) from four‐dimensional magnetic resonance imaging (4DMRI) data in carbon ion radiotherapy with pencil beam scanning for abdominal tumors. Methods Deformable image registration is used to: (a) register each respiratory phase of the 4DMRI to the end‐exhale MRI; (b) register the reference end‐exhale CT to the end‐exhale MRI volume; (c) generate the virtual 4DCT by warping the registered CT according to the obtained deformation fields. A respiratory‐gated carbon ion treatment plan is optimized on the planning 4DCT and the corresponding dose distribution is recalculated on the virtual 4DCT. The method was validated on a digital anthropomorphic phantom and tested on eight patients (18 acquisitions). For the phantom, a ground truth dataset was available to assess the method performances from the geometrical and dosimetric standpoints. For the patients, the virtual 4DCT was compared with the planning 4DCT. Results In the phantom, the method exhibits a geometrical accuracy within the voxel size and Dose Volume Histograms deviations up to 3.3% for target V95% (mean dose difference ≤ 0.2% of the prescription dose, gamma pass rate > 98%). For patients, the virtual and the planning 4DCTs show good agreement at end‐exhale (3% median D95% difference), whereas other respiratory phases exhibit moderate motion variability with consequent dose discrepancies, confirming the need for motion mitigation strategies during treatment. Conclusions The virtual 4DCT approach is feasible to evaluate treatment plan robustness against intra‐ and interfraction motion in carbon ion therapy delivered at the abdominal site.

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Impact of different respiratory gating methods on target delineation and a radiotherapy plan for solitary pulmonary tumors

Shang,

Duan,

Yin

et al. 2024

Cancer Medicine

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Background and PurposeRespiratory movement has an important impact on the radiotherapy for lung tumor. Respiratory gating technology is helpful to improve the accuracy of target delineation. This study investigated the value of prospective and retrospective respiratory gating simulations in target delineation and radiotherapy plan design for solitary pulmonary tumors (SPTs) in radiotherapy.MethodsThe enrolled patients underwent CT simulation with three‐dimensional (3D) CT non gating, prospective respiratory gating, and retrospective respiratory gating simulation. The target volumes were delineated on three sets of CT images, and radiotherapy plans were prepared accordingly. Tumor displacements and movement information obtained using the two respiratory gating approaches, as well as the target volumes and dosimetry parameters in the radiotherapy plan were compared.ResultsNo significant difference was observed in tumor displacement measured using the two gating methods (p > 0.05). However, the internal gross tumor volumes (IGTVs), internal target volumes (ITVs), and planning target volumes (PTVs) based on the retrospective respiratory gating simulation were larger than those obtained using prospective gating (group A: pIGTV = 0.041, pITV = 0.003, pPTV = 0.008; group B: pIGTV = 0.025, pITV = 0.039, pPTV = 0.004). The two‐gating PTVs were both smaller than those delineated on 3D non gating images (p < 0.001). V5Gy, V10Gy, V20Gy, V30Gy, and mean lung dose in the two gated radiotherapy plans were lower than those in the 3D non gating plan (p < 0.001); however, no significant difference was observed between the two gating plans (p > 0.05).ConclusionsThe application of respiratory gating could reduce the target volume and the radiation dose that the normal lung tissue received. Compared to prospective respiratory gating, the retrospective gating provides more information about tumor movement in PTV.

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Validation of a model for physical dose variations in irregularly moving targets treated with carbon ion beams

Cited by 10 publications

References 37 publications

Modeling RBE‐weighted dose variations in irregularly moving abdominal targets treated with carbon ion beams

Modeling RBE‐weighted dose variations in irregularly moving abdominal targets treated with carbon ion beams

Virtual 4DCT from 4DMRI for the management of respiratory motion in carbon ion therapy of abdominal tumors

Impact of different respiratory gating methods on target delineation and a radiotherapy plan for solitary pulmonary tumors

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