Assessment of MLC tracking performance during hypofractionated prostate radiotherapy using real-time dose reconstruction

Fast, Martin F.; Kamerling, C P; Ziegenhein, Peter; Menten, Martin J.; Bedford, James L.; Nill, Simeon; Oelfke, Uwe

doi:10.1088/0031-9155/61/4/1546

Cited by 39 publications

(65 citation statements)

References 33 publications

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“…Therefore, at least 4D dose re‐calculations are desired after each treatment fraction. Examples for 4D dose reconstructions have already been reported for scanned carbon beam therapy and photon therapy using dynamic multi‐leaf collimator tracking . This study has shown that the model is able to predict CT images corresponding to respiratory states described by two parameters (phase and amplitude) combined with information on the inter‐fraction anatomical variations with respect to the planning CT.…”

Section: Discussionmentioning

confidence: 80%

Examination of a deformable motion model for respiratory movements and 4D dose calculations using different driving surrogates

et al. 2017

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Section: Discussionmentioning

confidence: 80%

Examination of a deformable motion model for respiratory movements and 4D dose calculations using different driving surrogates

et al. 2017

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“…Figure describes the actual online dose reconstruction step‐by‐step, in line with our previous work in Fast et al . DynaTrack sends actual MLC apertures and target positions to DynaPlan immediately after they are available.…”

Section: Methodsmentioning

confidence: 89%

“…Previously, DynaTrack was used for either conformal deliveries, S&S IMRT, or conformal VMAT . In this study, standard VMAT was supported for the first time.…”

Section: Methodsmentioning

confidence: 99%

Online dose reconstruction for tracked volumetric arc therapy: Real‐time implementation and offline quality assurance for prostate SBRT

et al. 2017

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Purpose: Firstly, this study provides a real-time implementation of online dose reconstruction for tracked volumetric arc therapy (VMAT). Secondly, this study describes a novel offline quality assurance tool, based on commercial dose calculation algorithms. Methods: Online dose reconstruction for VMAT is a computationally challenging task in terms of computer memory usage and calculation speed. To potentially reduce the amount of memory used, we analyzed the impact of beam angle sampling for dose calculation on the accuracy of the dose distribution. To establish the performance of the method, we planned two single-arc VMAT prostate stereotactic body radiation therapy cases for delivery with dynamic MLC tracking. For quality assurance of our online dose reconstruction method we have also developed a stand-alone offline dose reconstruction tool, which utilizes the RayStation treatment planning system to calculate dose. Results: For the online reconstructed dose distributions of the tracked deliveries, we could establish strong resemblance for 72 and 36 beam co-planar equidistant beam samples with less than 1.2% deviation for the assessed dose-volume indicators (clinical target volume D98 and D2, and rectum D2). We could achieve average runtimes of 28-31 ms per reported MLC aperture for both dose computation and accumulation, meeting our real-time requirement. To cross-validate the offline tool, we have compared the planned dose to the offline reconstructed dose for static deliveries and found excellent agreement (3%/3 mm global gamma passing rates of 99.8%-100%). Conclusion: Being able to reconstruct dose during delivery enables online quality assurance and online replanning strategies for VMAT. The offline quality assurance tool provides the means to validate novel online dose reconstruction applications using a commercial dose calculation engine.

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“…Several methods have been proposed to compute the delivered dose based on offline dose reconstruction 15 , 16 , 17 , 18 . Recently, we have presented an online dose reconstruction solution for assessment of prostate SBRT, 19 which calculates and accumulates dose in real‐time based on dose‐influence data, while accounting for the machine/target motion interplay. Dose‐influence data describe the influence of the fluence distribution on the patient dose.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, accumulating the dose onto a reference phase requires deformable image registration (DIR) and a real‐time dose mapping algorithm. We add to our previously presented online dose reconstruction platform 19 by providing implementations for each of these challenges.…”

Section: Introductionmentioning

confidence: 99%

Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT

et al. 2016

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PurposeThis study provides a proof of concept for real‐time 4D dose reconstruction for lung stereotactic body radiation therapy (SBRT) with multileaf collimator (MLC) tracking and assesses the impact of tumor tracking on the size of target margins.MethodsThe authors have implemented real‐time 4D dose reconstruction by connecting their tracking and delivery software to an Agility MLC at an Elekta Synergy linac and to their in‐house treatment planning software (TPS). Actual MLC apertures and (simulated) target positions are reported to the TPS every 40 ms. The dose is calculated in real‐time from 4DCT data directly after each reported aperture by utilization of precalculated dose‐influence data based on a Monte Carlo algorithm. The dose is accumulated onto the peak‐exhale (reference) phase using energy‐mass transfer mapping. To investigate the impact of a potentially reducible safety margin, the authors have created and delivered treatment plans designed for a conventional internal target volume (ITV) + 5 mm, a midventilation approach, and three tracking scenarios for four lung SBRT patients. For the tracking plans, a moving target volume (MTV) was established by delineating the gross target volume (GTV) on every 4DCT phase. These were rigidly aligned to the reference phase, resulting in a unified maximum GTV to which a 1, 3, or 5 mm isotropic margin was added. All scenarios were planned for 9‐beam step‐and‐shoot IMRT to meet the criteria of RTOG 1021 (3 × 18 Gy). The GTV 3D center‐of‐volume shift varied from 6 to 14 mm.ResultsReal‐time dose reconstruction at 25 Hz could be realized on a single workstation due to the highly efficient implementation of dose calculation and dose accumulation. Decreased PTV margins resulted in inadequate target coverage during untracked deliveries for patients with substantial tumor motion. MLC tracking could ensure the GTV target dose for these patients. Organ‐at‐risk (OAR) doses were consistently reduced by decreased PTV margins. The tracked MTV + 1 mm deliveries resulted in the following OAR dose reductions: lung V 20 up to 3.5%, spinal cord D 2 up to 0.9 Gy/Fx, and proximal airways D 2 up to 1.4 Gy/Fx.ConclusionsThe authors could show that for patient data at clinical resolution and realistic motion conditions, the delivered dose could be reconstructed in 4D for the whole lung volume in real‐time. The dose distributions show that reduced margins yield lower doses to healthy tissue, whilst target dose can be maintained using dynamic MLC tracking.

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Assessment of MLC tracking performance during hypofractionated prostate radiotherapy using real-time dose reconstruction

Cited by 39 publications

References 33 publications

Examination of a deformable motion model for respiratory movements and 4D dose calculations using different driving surrogates

Examination of a deformable motion model for respiratory movements and 4D dose calculations using different driving surrogates

Online dose reconstruction for tracked volumetric arc therapy: Real‐time implementation and offline quality assurance for prostate SBRT

Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT

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