Geometric accuracy of a real-time target tracking system with dynamic multileaf collimator tracking system

Keall, P.; Cattell, H.; Pokhrel, Damodar; Dieterich, Sonja; Wong, Kenneth H.; Murphy, Martin J.; Vedam, Sastry; Wijesooriya, K.; Mohan, Radhe

doi:10.1016/j.ijrobp.2006.04.038

Cited by 156 publications

(131 citation statements)

References 23 publications

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“…[2][3][4][5][6][7] Dynamic multileaf collimator (DMLC) tracking is a method to compensate for intrafraction target motion by real-time adaption of the MLC aperture to the targets movement. [8][9][10][11][12][13][14][15][16][17] Other methods of motion compensation, not covered in this study, include beam gating, moving the source, and couch tracking. The accuracy of DMLC tracking depends on the alignment between the leaves and the target motion, with motion perpendicular to the leaf travel being more challenging.…”

Section: Introductionmentioning

confidence: 99%

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

et al. 2013

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Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments. Methods: Prostate IMAT plans were delivered with either a high-definition MLC (HDMLC) or a Millennium MLC (M-MLC) (0.25 and 0.50 cm central leaf width, respectively), with and without DMLC tracking, to a dosimetric phantom that reproduced four prostate motion traces. The plan complexity was varied by applying leaf position constraints during plan optimization. A subset of the M-MLC plans was converted for delivery with the HDMLC, isolating the effect of the different leaf widths. The gamma index was used for evaluation. Tracking errors caused by target localization, leaf fitting, and leaf adjustment were analyzed. Results: The gamma pass rate was significantly improved with DMLC tracking compared to no tracking (p < 0.001). With DMLC tracking, the average gamma index pass rate was 98.6% (range 94.8%-100%) with the HDMLC and 98.1% (range 95.4%-99.7%) with the M-MLC, using 3%, 3 mm criteria and the planned dose as reference. The corresponding pass rates without tracking were 87.6% (range 76.2%-94.7%) and 91.1% (range 81.4%-97.6%), respectively. Decreased plan complexity improved the pass rate when static target measurements were used as reference, but not with the planned dose as reference. The main cause of tracking errors was leaf fitting errors, which were decreased by 42% by halving the leaf width. Conclusions: DMLC tracking successfully compensated for the prostate motion. The finer leaf width of the HDMLC improved the tracking accuracy compared to the M-MLC. The tracking improvement with limited plan complexity was small and not discernible when using the planned dose as reference.

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Section: Introductionmentioning

confidence: 99%

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

et al. 2013

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“…1). This measurement technique was first adopted by Keall et al21 and Sawant et al10 to evaluate the geometric accuracy of a DMLC tracking system. To facilitate the subsequent image processing, a green plate with a cross‐mark was placed under the aperture (see Fig.…”

Section: Methodsmentioning

confidence: 99%

Development and performance evaluation of a high‐speed multileaf collimator

Zhang

2016

J Applied Clin Med Phys

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Multileaf collimator (MLC) tracking represents a promising technique for motion management in radiotherapy. However, the conflict between limited leaf speed/acceleration and the demand for tracking fast target motion is now a prominent issue. Conventional MLCs typically have a maximum leaf speed of 3–4 cm/s and a maximum leaf acceleration of 50–70 cm/s2, which are inadequate to track fast target motion. To cope with this problem, we have recently developed a high‐speed multileaf collimator (HS‐MLC) prototype, which employs linear motors instead of rotary motors to drive leaves. Consequently, it inherits various benefits of linear motors, including direct drive and high dynamics. The primary aim of this paper was to introduce the development and performance evaluation of the HS‐MLC. The evaluation includes Monte Carlo simulations of the basic dosimetric properties, camera‐based measurements of the mechanical properties and tracking experiments for 25 sets of patient‐measured motion data. The Monte Carlo simulation results show that the maximum leakage at 6MV is 1.29% and the average is 0.61%. The end‐to‐end leakage is 3.96% for 5 cm offset and is 1.75% for 10 cm offset. The penumbra for a standard 10 × 10 cm2 field ranges from 4.8 mm to 5.4 mm across the full range of leaf motion. The mechanical property measurements demonstrate that the maximum leaf speed is 40 cm/s, the maximum leaf acceleration is 1000 cm/s2, and the geometric accuracy can be kept within 0.5 mm. Regarding the tracking experiments for a wide range of motion patterns (fast breathing, irregular breathing, etc.), a root‐mean‐square error (RMSE) of less than 0.19 mm was achieved. In conclusion, the HS‐MLC is able to well track fast target motion that is beyond the capability of conventional MLCs due to its superior mechanical properties. The new MLC design provides a feasible solution to make high‐accuracy and high‐efficiency motion management possible.

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“…Another approach, to be discussed now, is tracking the tumour during irradiation and correcting for it in real-time (Keall et al, 2001;Murphy, 2004). Corrections for tumour motion can be applied by either dynamically adjusting the aperture of the radiation beam shaping device (Keall et al, 2006), the multi-leaf collimator (MLC), or by moving the patient relative to the stationary radiation beam (D'Souza et al, 2005). The latter can be achieved by means of the HexaPOD treatment table and will be discussed henceforth.…”

Section: Dynamic Compensation For Intra-fractional Tumour Movementmentioning

confidence: 99%

On the Use of a Hexapod Table to Improve Tumour Targeting in Radiation Therapy

Meyer¹,

Gückenberger²,

Wilbert³

et al. 2007

Bioinspiration and Robotics Walking and Climbing Robots

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Geometric accuracy of a real-time target tracking system with dynamic multileaf collimator tracking system

Cited by 156 publications

References 23 publications

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

Development and performance evaluation of a high‐speed multileaf collimator

On the Use of a Hexapod Table to Improve Tumour Targeting in Radiation Therapy

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