Dose reconstruction including dynamic six-degree of freedom motion during prostate radiotherapy

Muurholm, C.G.; Ravkilde, T.; Skouboe, Simon; Eade, Thomas; Nguyen, Diep N.; Booth, Jeremy; Keall, P.; Poulsen, Per Rugaard

doi:10.1088/1742-6596/1305/1/012053

Cited by 6 publications

(15 citation statements)

References 10 publications

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“…Dose reconstructions assuming constant rotations deviated largely from film doses, showing that such an assumption may be inadequate for dynamic treatments such as VMAT. This is in alignment with a preliminary study that also performed dose reconstruction with dynamic rotations 27 using a home‐made dose reconstruction method without experimental validation.…”

Section: Discussionsupporting

confidence: 81%

“…Still, the approach may be used to evaluate treatments with known prostate rotations under the assumption that interplay effects are negligible 25 . Dose reconstruction considering dynamic prostate rotations has been conducted in a single study that demonstrated large prostate dose distortions owing to interplay effects 27 . However, the study only included one case, it used in‐house developed dose calculations rather than a commercial TPS, and it was not experimentally validated.…”

Section: Introductionmentioning

confidence: 99%

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Six degrees of freedom dynamic motion‐including dose reconstruction in a commercial treatment planning system

et al. 2021

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Purpose Intrafractional motion during radiotherapy delivery can deteriorate the delivered dose. Dynamic rotational motion of up to 38 degrees has been reported during prostate cancer radiotherapy, but methods to determine the dosimetric consequences of such rotations are lacking. Here, we create and experimentally validate a dose reconstruction method that accounts for dynamic rotations and translations in a commercial treatment planning system (TPS). Interplay effects are quantified by comparing dose reconstructions with dynamic and constant rotations. Methods The dose reconstruction accumulates the dose in points of interest while the points are moved in six degrees of freedom (6DoF) in a precalculated time‐resolved four‐dimensional (4D) dose matrix to emulate dynamic motion in a patient. The required 4D dose matrix was generated by splitting the original treatment plan into multiple sub‐beams, each representing 0.4 s dose delivery, and recalculating the dose of the split plan in the TPS (Eclipse). The dose accumulation was performed via TPS scripting by querying the dose of each sub‐beam in dynamically moving points, allowing dose reconstruction with any dynamic motion. The dose reconstruction was validated with film dosimetry for two prostate dual arc VMAT plans with intra‐prostatic lesion boosts. The plans were delivered to a pelvis phantom with internal dynamic rotational motion of a film stack (21 films with 2.5 mm separation). Each plan was delivered without motion and with three prostate motion traces. Motion‐including dose reconstruction was performed for each motion experiment using the actual dynamic rotation as well as a constant rotation equal to the mean rotation during the experiment. For each experiment, the 3%/2 mm γ failure rate of the TPS dose reconstruction was calculated with the film measurement being the reference. For each motion experiment, the motion‐induced 3%/2 mm γ failure rate was calculated using the static delivery as the reference and compared between film measurements and TPS dose reconstruction. DVH metrics for RT structures fully contained in the film volume were also compared between film and TPS. Results The mean γ failure rate of the TPS dose reconstructions when compared to film doses was 0.8% (two static experiments) and 1.7% (six dynamic experiments). The mean (range) of the motion‐induced γ failure rate in film measurements was 35.4% (21.3–59.2%). The TPS dose reconstruction agreed with these experimental γ failure rates with root‐mean‐square errors of 2.1% (dynamic rotation dose reconstruction) and 17.1% (dose reconstruction assuming constant rotation). By DVH metrics, the mean (range) difference between dose reconstructions with dynamic and constant rotation was 4.3% (−0.3–10.6%) (urethra D2%), −0.6% (−5.6%–2.5%) (urethra D99%), 1.1% (−7.1–7.7%) (GTV D2%), −1.4% (−17.4–7.1%) (GTV D95%), −1.2% (−17.1–5.7%) (GTV D99%), and −0.1% (−3.2–7.6%) (GTV mean dose). Dose reconstructions with dynamic motion revealed large interplay effects (cold and hot spots). Conclusions A meth...

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Six degrees of freedom dynamic motion‐including dose reconstruction in a commercial treatment planning system

et al. 2021

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“…While several methods for dose reconstruction are described in literature, popular approaches are based on combining the simulated or delivered beams with the prostate intrafraction motion, obtained by tracking implanted fiducial markers with kilovoltage (kV) imaging [10] , megavoltage (MV) imaging [5] or using magnetic implanted markers with the Calypso system [6] . Although these methods can provide a fair estimation of the delivered dose to the prostate, they lack soft tissue intrafraction information of surrounding OAR [2] and can therefore not be used to accurately reconstruct the delivered dose in the OARs.…”

Section: Introductionmentioning

confidence: 99%

Delivered dose quantification in prostate radiotherapy using online 3D cine imaging and treatment log files on a combined 1.5T magnetic resonance imaging and linear accelerator system

Kontaxis

Keizer

Kerkmeijer

et al. 2020

Physics and Imaging in Radiation Oncology

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Background and purpose: Monitoring the intrafraction motion and its impact on the planned dose distribution is of crucial importance in radiotherapy. In this work we quantify the delivered dose for the first prostate patients treated on a combined 1.5T Magnetic Resonance Imaging (MRI) and linear accelerator system in our clinic based on online 3D cine-MR and treatment log files. Materials and methods: A prostate intrafraction motion trace was obtained with a soft-tissue based rigid registration method with six degrees of freedom from 3D cine-MR dynamics with a temporal resolution of 8.5-16.9 s. For each fraction, all dynamics were also registered to the daily MR image used during the online treatment planning, enabling the mapping to this reference point. Moreover, each fraction's treatment log file was used to extract the timestamped machine parameters during delivery and assign it to the appropriate dynamic volume. These partial plans to dynamic volume combinations were calculated and summed to yield the delivered fraction dose. The planned and delivered dose distributions were compared among all patients for a total of 100 fractions. Results: The clinical target volume underwent on average a decrease of 2.2% ± 2.9% in terms of D99% coverage while bladder V62Gy was increased by 1.6% ± 2.3% and rectum V62Gy decreased by 0.2% ± 2.2%. Conclusions: The first MR-linac dose reconstruction results based on prostate tracking from intrafraction 3D cine-MR and treatment log files are presented. Such a pipeline is essential for online adaptation especially as we progress to MRI-guided extremely hypofractionated treatments.

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“…Although dose-guidance was superior to geometry guidance in all the studied cases, it will be more important for more complex cases that are not easily understood from geometry alone. One example is when dose deficits caused by rotational motion [20,21] are to be compensated by translational couch corrections. Another example is when conflicting dosimetric requirements arise because several targets or OARs move relative to each other.…”

Section: Discussionmentioning

confidence: 99%

Real-time dose-guidance in radiotherapy: Proof of principle

Muurholm

Ravkilde

Skouboe

et al. 2021

Radiotherapy and Oncology

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The outcome of radiotherapy is a direct consequence of the dose delivered to the patient. Yet image-guidance and motion management to date focus on geometrical considerations as a practical surrogate for dose. Here, we propose real-time dose-guidance realized through continuous motion-including dose reconstructions and demonstrate this new concept in simulated liver stereotactic body radiotherapy (SBRT) delivery. Materials and methods: During simulated liver SBRT delivery, in-house developed software performed real-time motion-including reconstruction of the tumor dose delivered so far and continuously predicted the remaining fraction tumor dose. The total fraction dose was estimated as the sum of the delivered and predicted doses, both with and without the emulated couch correction that maximized the predicted final CTV D95% (minimum dose to 95% of the clinical target volume).Dose-guided treatments were simulated for 15 liver SBRT patients previously treated with tumor motion monitoring, using both sinusoidal tumor motion and the actual patient-measured motion. A dose-guided couch correction was triggered if it improved the predicted final CTV D95% with 3, 4 or 5 %-points. The final CTV D95% of the dose-guidance strategy was compared with simulated treatments using geometry guided couch corrections (Wilcoxon signed-rank test). Results: Compared to geometry guidance, dose-guided couch corrections improved the median CTV D95% with 0.5-1.5 %-points (p < 0.01) for sinusoidal motions and with 0.9 %-points (p < 0.01, 3 %-points trigger threshold), 0.5 %-points (p = 0.03, 4 %-points threshold) and 1.2 %-points (p = 0.09, 5 %-points threshold) for patient-measured tumor motion. Conclusion: Real-time dose-guidance was proposed and demonstrated to be superior to geometrical adaptation in liver SBRT simulations.

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Dose reconstruction including dynamic six-degree of freedom motion during prostate radiotherapy

Cited by 6 publications

References 10 publications

Six degrees of freedom dynamic motion‐including dose reconstruction in a commercial treatment planning system

Six degrees of freedom dynamic motion‐including dose reconstruction in a commercial treatment planning system

Delivered dose quantification in prostate radiotherapy using online 3D cine imaging and treatment log files on a combined 1.5T magnetic resonance imaging and linear accelerator system

Real-time dose-guidance in radiotherapy: Proof of principle

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