The long- and short-term variability of breathing induced tumor motion in lung and liver over the course of a radiotherapy treatment

Dhont, Jennifer; Vandemeulebroucke, Jef; Burghelea, M.; Poels, Kenneth; Depuydt, Tom; Begin, Robbe Van den; Jaudet, Cyril; Collen, Christine; Engels, Benedikt; Reynders, Truus; Boussaer, M.; Gevaert, Thierry; Ridder, Mark De; Verellen, Dirk

doi:10.1016/j.radonc.2017.09.001

Cited by 104 publications

(124 citation statements)

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“…The variability of breathing induced motion has been reported to be significant . This is a critical issue in particle therapy, as it introduces uncertainty in target localization and tissue density within the beam path with respect to the planning scenario.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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Purpose In particle therapy, conventional treatment planning systems rely on an imaging representation of the irradiated region to compute the dose. For irregular breathing, when an imaging dataset describing the actual motion is not available, a different approach for dose estimation is needed. To this aim, we validate a method for the estimation of physical dose variations in gated carbon ion treatments, providing also a demonstration of the feasibility of physical dose metrics to assess the method performance. Finally, we describe a sample use case, in which this method is used to assess plan robustness with respect to undetected irregular tumor motion. Methods The method entails the definition of a patient‐ and beam‐specific water equivalent depth (WED) space, the simulation of motion as a translation equal to tumor displacement, and the reconstruction of the altered dose. We validated the approach using four‐dimensional computed tomographies (4DCTs) and clinical plans in 12 patients, treated with respiratory gated carbon ion beams at the National Centre for Oncological Hadrontherapy (Pavia, Italy). Using the end‐exhale CT and dose distribution as a reference, the physical dose delivered at the end‐inhale tumor position was estimated and compared to the ground‐truth dose recalculation on the end‐inhale CT. Biologically effective and physical dose variations between the plan and the recalculation were compared as well. As a use case, we evaluated dose changes caused by simulated irregular tumor motion, that is, linear and nonlinear baseline shifts and/or amplitude variations with hysteresis. Results The ratio between biologically effective and physical equivalent uniform dose (EUD) variations due to end‐exhale to end‐inhale motion was less than one for 96% of investigated structures. In the validation study, we found a median error corresponding to a 14% EUD overestimation for the tumor and 4% EUD underestimation for a subgroup of organs at risk, together with a high EUD variation due to motion [median 352% EUD variation between end‐exhale and end‐inhale doses in the planning tumor volume (PTV)]. Considering relevant dose‐volume histogram (DVH) metrics, the median difference between estimated and ground truth doses was ≤ 4%. Gamma analysis between estimated and recalculated dose distributions resulted in a pass rate > 80% for 83% of the target volumes. For the two patients selected for the sample use case, a patient‐specific assessment of the method performance was performed on the 4DCT and it was possible to relate EUD variations of both tumor and organs at risk to the simulated target motion. Conclusions The physical dose distribution was found to be more sensitive to motion with respect to the biologically effective one, suggesting the suitability of the physical dose metrics for the WED‐space method validation. We showed that the method can compensate for intra‐fractional tumor motion with proper accuracy in the selected patient group, although its use is recommended when limited deformations are expected....

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Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…The main limitation of using 4DCT as imaging modality for treatment planning is that this technique depicts an “average” respiratory cycle, being representative of the imaged anatomy only within the time interval of the imaging acquisition. The limited representativeness of 4DCT of variable breathing patterns hinders to sample a sufficient level of information to grant robust treatment planning against intra‐ and interfraction tumor motion variability, which can have a significant impact on the treatment …”

Section: Introductionmentioning

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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“…Motion‐encompassing treatment techniques try to handle incompletely predictable processes. The tumor motion during treatment might differ substantially from the motion during the treatment planning phase, which could lead to partial target miss. In addition, temporal interplay between the momentary tumor position and the beam delivery of modulated fields may affect the dose delivered to the tumor .…”

Section: Introductionmentioning

confidence: 99%

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

et al. 2019

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Purpose Real‐time motion‐adaptive radiotherapy of intrahepatic tumors needs to account for motion and deformations of the liver and the target location within. Phantoms representative of anatomical deformations are required to investigate and improve dynamic treatments. A deformable phantom capable of testing motion detection and motion mitigation techniques is presented here. Methods The dynamically dEformable Liver PHAntom (ELPHA) was designed to fulfill three main constraints: First, a reproducibly deformable anatomy is required. Second, the phantom should provide multimodality imaging contrast for motion detection. Third, a time‐resolved dosimetry system to measure temporal effects should be provided. An artificial liver with vasculature was casted from soft silicone mixtures. The silicones allow for deformation and radiographic image contrast, while added cellulose provides ultrasonic contrast. An actuator was used for compressing the liver in the inferior direction according to a prescribed respiratory motion trace. Electromagnetic (EM) transponders integrated in ELPHA help provide ground truth motion traces. They were used to quantify the motion reproducibility of the phantom and to validate motion detection based on ultrasound imaging. A two‐dimensional ultrasound probe was used to follow the position of the vessels with a template‐matching algorithm. This detected vessel motion was compared to the EM transponder signal by calculating the root‐mean‐square error (RMSE). ELPHA was then used to investigate the dose deposition of dynamic treatment deliveries. Two dosimetry systems, radio‐chromic film and plastic scintillation dosimeters (PSD), were integrated in ELPHA. The PSD allow for time‐resolved measurement of the delivered dose, which was compared to a time‐resolved dose of the treatment planning system. Film and PSD were used to investigate dose delivery to the deforming phantom without motion compensation and with treatment‐couch tracking for motion compensation. Results ELPHA showed densities of 66 and 45 HU in the liver and the surrounding tissues. A high motion reproducibility with a submillimeter RMSE (<0.32 mm) was measured. The motion of the vasculature detected with ultrasound agreed well with the EM transponder position (RMSE < 1 mm). A time‐resolved dosimetry system with a 1 Hz time resolution was achieved with the PSD. The agreement of the planned and measured dose to the PSD decreased with increasing motion amplitude: A dosimetric RMSE of 1.2, 2.1, and 2.7 cGy/s was measured for motion amplitudes of 8, 16, and 24 mm, respectively. With couch tracking as motion compensation, these values decreased to 1.1, 1.4, and 1.4 cGy/s. This is closer to the static situation with 0.7 cGy/s. Film measurements showed that couch tracking was able to compensate for motion with a mean target dose within 5% of the static situation (−5% to +1%), which was higher than in the uncompensated cases (−41% to −1%). Conclusions ELPHA is a deformable liver phantom with high motion reproducibility. It was demonstrated t...

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The long- and short-term variability of breathing induced tumor motion in lung and liver over the course of a radiotherapy treatment

Cited by 104 publications

References 49 publications

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

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

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

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

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