Characteristics and performance of the first commercial multileaf collimator for a robotic radiosurgery system

Fürweger, Christoph; Prins, P.R.; Coskan, Harun; Heijmen, B.

doi:10.1118/1.4944740

Cited by 28 publications

(30 citation statements)

References 24 publications

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“…On the other hand, the penumbrae formed by the leaf sides (along the Y ‐axis) were wider on the +Y sides of the leaves than they were on the −Y sides. This asymmetry was regarded as resulting from the leaf bank tilt 24. These penumbra width results are similar to those reported by Fürweger et al24 Furthermore, although the discrepancies between the measured and calculated widths of the X ‐axis penumbrae were relatively small (maximum, 0.3 mm), those between the measured and calculated widths of the Y ‐axis penumbrae were large (maximum, 0.7 mm) when the MLC was used.…”

Section: Discussionsupporting

confidence: 88%

“…This asymmetry was regarded as resulting from the leaf bank tilt 24. These penumbra width results are similar to those reported by Fürweger et al24 Furthermore, although the discrepancies between the measured and calculated widths of the X ‐axis penumbrae were relatively small (maximum, 0.3 mm), those between the measured and calculated widths of the Y ‐axis penumbrae were large (maximum, 0.7 mm) when the MLC was used. On the other hand, the discrepancies resulting from using the fixed and variable collimators were within 0.1 mm.…”

Section: Discussionsupporting

confidence: 88%

“…On the other hand, the rectum dose did not differ significantly between the different collimator types, as was found previously 8, 9. The CyberKnife workspace extends from lateral to anterior, to accommodate patients in supine positions, and the ability to arrange beams below the couch is limited 24. Therefore, we assumed that the doses received by the bladder, which is located ventral to the prostate anatomically, could be reduced in the MLC plans relative to those in the circular collimator plans because of the MU reduction and the ability to fit the radiation fields to irregular PTV shapes.…”

Section: Discussionsupporting

confidence: 75%

“…Concerning the collimator position reproducibility, a variable collimator is designed to achieve an aperture reproducibility of ≤0.2 mm at a SAD of 800 mm 25. Meanwhile, Fürweger et al demonstrated using Bayouth tests that the average leaf position offset resulting from using a Cyberknife M6 with an InCise MLC was ≤0.5 mm 24. Regarding the second factor affecting the DQA results, the beam modeling accuracy in the MLC beams was found to be inferior to those in the beams based on the other collimators, since the beam commissioning results revealed dose discrepancies of greater than 3% between the measured and calculated doses in the MLC beams.…”

Section: Discussionmentioning

confidence: 99%

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Clinical usefulness of MLCs in robotic radiosurgery systems for prostate SBRT

Tomida

Kamomae

Suzuki

et al. 2017

J Applied Clin Med Phys

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Stereotactic body radiation therapy (SBRT) using recently introduced multileaf collimators (MLC) is preferred over circular collimators in the treatment of localized prostate cancer. The objective of this study was to assess the clinical usefulness of MLCs in prostate SBRT by comparing the effectiveness of treatment plans using fixed collimators, variable collimators, and MLCs and by ensuring delivery quality assurance (DQA) for each. For each patient who underwent conventional radiation therapy for localized prostate cancer, mock SBRT plans were created using a fixed collimator, a variable collimator, and an MLC. The total MUs, treatment times, and dose–volume histograms of the planning target volumes and organs at risk for each treatment plan were compared. For DQA, a phantom with a radiochromic film or an ionization chamber was irradiated in each plan. We performed gamma‐index analysis to evaluate the consistency between the measured and calculated doses. The MLC‐based plans had an ~27% lower average total MU than the plans involving other collimators. Moreover, the average estimated treatment time for the MLC plan was 31% and 20% shorter than that for the fixed and variable collimator plans respectively. The gamma‐index passing rate in the DQA using film measurements was slightly lower for the MLC than for the other collimators. The DQA results acquired using the ionization chamber showed that the discrepancies between the measured and calculated doses were within 3% in all cases. The results reinforce the usefulness of MLCs in robotic radiosurgery for prostrate SBRT treatment planning; most notably, the total MU and treatment time were both reduced compared to the cases using other types of collimators. Moreover, although the DQA results based on film dosimetry yielded a slightly lower gamma‐index passing rate for the MLC than for the other collimators, the MLC accuracy was determined to be sufficient for clinical use.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Clinical usefulness of MLCs in robotic radiosurgery systems for prostate SBRT

Tomida

Kamomae

Suzuki

et al. 2017

J Applied Clin Med Phys

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“…The recently released CyberKnife® M6™ system is now equipped with multi-leaf collimator (InCise 2™) [15-16], which is reported to be more efficient in treating larger targets with fewer monitor units and less treatment time [17-19]. Linac-based SABR with gated VMAT delivery and a very high dose rate (flattening filter free) has also been implemented in the past several years.…”

Section: Introductionmentioning

confidence: 99%

Stereotactic Arrhythmia Radioablation (STAR) of Ventricular Tachycardia: A Treatment Planning Study

Wang¹,

Fahimian²,

Soltys³

et al. 2016

Cureus

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PurposeThe first stereotactic arrhythmia radioablation (STAR) of ventricular tachycardia (VT) was delivered at Stanford on a robotic radiosurgery system (CyberKnife® G4) in 2012. The results warranted further investigation of this treatment. Here we compare dosimetrically three possible treatment delivery platforms for STAR.MethodsThe anatomy and target volume of the first treated patient were used for this study. A dose of 25 Gy in one fraction was prescribed to the planning target volume (PTV). Treatment plans were created on three treatment platforms: CyberKnife® G4 system with Iris collimator (Multiplan, V. 4.6)(Plan #1), CyberKnife® M6 system with InCise 2TM multileaf collimator (Multiplan V. 5.3)(Plan #2) and Varian TrueBeamTM STx with HD 120TM MLC and 10MV flattening filter free (FFF) beam (Eclipse planning system, V.11) (Plan #3 coplanar and #4 noncoplanar VMAT plans). The four plans were compared by prescription isodose line, plan conformity index, dose gradient, as well as dose to the nearby critical structures. To assess the delivery efficiency, planned monitor units (MU) and estimated treatment time were evaluated.ResultsPlans #1-4 delivered 25 Gy to the PTV to the 75.0%, 83.0%, 84.3%, and 84.9% isodose lines and with conformity indices of 1.19, 1.16, 1.05, and 1.05, respectively. The dose gradients for plans #1-4 were 3.62, 3.42, 3.93, and 3.73 with the CyberKnife® MLC plan (Plan #2) the best, and the TrueBeamTM STx co-planar plan (Plan #3) the worst. The dose to nearby critical structures (lung, stomach, bowel, and esophagus) were all well within tolerance. The MUs for plans #1-4 were 27671, 16522, 6275, and 6004 for an estimated total-treatment-time/beam-delivery-time of 99/69, 65/35, 37/7, and 56/6 minutes, respectively, under the assumption of 30 minutes pretreatment setup time. For VMAT gated delivery, a 40% duty cycle, 2400MU/minute dose rate, and an extra 10 minutes per extra arc were assumed.ConclusionClinically acceptable plans were created with all three platforms. Plans with MLC were considerably more efficient in MU. CyberKnife® M6 with InCise 2TM collimator provided the most conformal plan (steepest dose drop-off) with significantly reduced MU and treatment time. VMAT plans were most efficient in MU and delivery time. Fluoroscopic image guidance removes the need for additional fiducial marker placement; however, benefits may be moderated by worse dose gradient and more operator-dependent motion management by gated delivery.

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Steeper dose gradients resulting from reduced source to target distance—a planning system independent study

Bratengeier

Holubyev

Wegener

2018

J Applied Clin Med Phys

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PurposeTo quantify the contribution of penumbra in the improvement of healthy tissue sparing at reduced source‐to‐axis distance (SAD) for simple spherical target and different prescription isodoses (PI).MethodA TPS‐independent method was used to estimate three‐dimensional (3D) dose distribution for stereotactic treatment of spherical targets of 0.5 cm radius based on single beam two‐dimensional (2D) film dosimetry measurements. 1 cm target constitutes the worst case for the conformation with standard Multi‐Leaf Collimator (MLC) with 0.5 cm leaf width. The measured 2D transverse dose cross‐sections and the profiles in leaf and jaw directions were used to calculate radial dose distribution from isotropic beam arrangement, for both quadratic and circular beam openings, respectively. The results were compared for standard (100 cm) and reduced SAD 70 and 55 cm for different PI.ResultsFor practical reduction of SAD using quadratic openings, the improvement of healthy tissue sparing (HTS) at distances up to 3 times the PTV radius was at least 6%–12%; gradient indices (GI) were reduced by 3–39% for PI between 40% and 90%. Except for PI of 80% and 90%, quadratic apertures at SAD 70 cm improved the HTS by up to 20% compared to circular openings at 100 cm or were at least equivalent; GI were 3%–33% lower for reduced SAD in the PI range 40%–70%. For PI = 80% and 90% the results depend on the circular collimator model.ConclusionStereotactic treatments of spherical targets delivered at reduced SAD of 70 or 55 cm using MLC spare healthy tissue around the target at least as good as treatments at SAD 100 cm using circular collimators. The steeper beam penumbra at reduced SAD seems to be as important as perfect target conformity. The authors argue therefore that the beam penumbra width should be addressed in the stereotactic studies.

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Characteristics and performance of the first commercial multileaf collimator for a robotic radiosurgery system

Abstract: The InCise™ MLC for CyberKnife showed high accuracy and adequate characteristics for SRS/SBRT applications. MLC performance after exercise demands specific quality assurance measures.

Cited by 28 publications

References 24 publications

Clinical usefulness of MLCs in robotic radiosurgery systems for prostate SBRT

Clinical usefulness of MLCs in robotic radiosurgery systems for prostate SBRT

Stereotactic Arrhythmia Radioablation (STAR) of Ventricular Tachycardia: A Treatment Planning Study

Steeper dose gradients resulting from reduced source to target distance—a planning system independent study

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