A method of dose reconstruction for moving targets compatible with dynamic treatments

Poulsen, Per Rugaard; Schmidt, Morten; Keall, Paul J.; Worm, E.; Fledelius, Walther; Hoffmann, Lone

doi:10.1118/1.4754297

Cited by 89 publications

(101 citation statements)

References 27 publications

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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.…”

Section: Introductionmentioning

confidence: 99%

“…Schmidt et al 20 have performed a dosimetric analysis for lung radiation therapy (33 fractions) utilizing 4D offline dose reconstruction and use isocenter shifts to model the motion 17 . We believe that although this method may be of value for treatment sites with homogeneous tissue and rigid motion (e.g., prostate), it is flawed by inaccuracies for large tissue inhomogeneities and deformations as found in the lung.…”

Section: Introductionmentioning

confidence: 99%

“…For hypofractionated treatments such as lung SBRT, however, intrafractional motion does not simply blur the delivered dose anymore and hence its accurate mitigation is of importance. The isocenter shift method from Poulsen et al 17 is not suitable for estimation of OAR dose when target motion is different from OAR motion (as is the case in the lung). Moreover, this method is based on 3D image data, although 4D image data are usually available.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…With this method, the sum of the arcs in the bins equal the angle spanned for the original treatment arcs. Further details on the dose reconstruction framework can be found in Poulsen et al [23]. For the evaluation of the dose distribution for static organs, tumour motion trajectory files were not used and a single treatment isocentre was used instead (using delivered MLC and no motion).…”

Section: Dose Reconstructionmentioning

confidence: 99%

MLC tracking for lung SABR reduces planning target volumes and dose to organs at risk

Caillet

Keall

Colvill

et al. 2017

Radiotherapy and Oncology

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“…The performance of KIM-guided gating to deliver the planned dose was measured using an isocenter shift dose reconstruction method [23]. The delivered dose was reconstructed on the planning CT using the intrafraction prostate motion trajectories and linac trajectory log files, and compared directly against the planned dose.…”

Section: Performance Analysesmentioning

confidence: 99%

The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM)

Nguyen

O’Brien

Kim

et al. 2017

Radiotherapy and Oncology

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Purpose: We present the first clinical implementation of a real-time six-degree of freedom (6DoF) Kilovoltage Intrafraction Monitoring (KIM) system which tracks the cancer target translational and rotational motions during treatment. The method was applied to measure and correct for target motion during stereotactic body radiotherapy (SBRT) for prostate cancer. The 6 DoF KIM system has sub-millimetre accuracy and precision in all three translational axes, and less than 1° accuracy and 4° precision in all three rotational axes.

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A method of dose reconstruction for moving targets compatible with dynamic treatments

Cited by 89 publications

References 27 publications

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

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

MLC tracking for lung SABR reduces planning target volumes and dose to organs at risk

The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM)

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