Dosimetric comparison between cone/Iris‐based and InCise MLC‐based CyberKnife plans for single and multiple brain metastases

Jang, Seonghoe; Lalonde, R.J.; Ozhasoglu, Cihat; Burton, Steven A.; Heron, Dwight E.; Huq, M. Saiful

doi:10.1120/jacmp.v17i5.6260

Cited by 42 publications

(36 citation statements)

References 30 publications

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“…The findings considering plan quality and delivery efficiency are in accordance with [7], where treatment plans for a cohort of very diverse brain metastases in size, number of targets per plan and fractionation scheme were optimized with the InCise1, the previous version, which differs mainly in leaf width and had only a few installations. One major difference is the much better conformity in the optimized plans here, both for MLC and circular fields, which perhaps is an effect of prescribing to the 80% isodose in [7] instead of the 70%.…”

Section: Discussionsupporting

confidence: 51%

“…One major difference is the much better conformity in the optimized plans here, both for MLC and circular fields, which perhaps is an effect of prescribing to the 80% isodose in [7] instead of the 70%. As the number of nodes and segments/beams is less for the MLC and the penumbra shows no substantial differences to the IRIS, the reason for the steeper high-dose gradient in MLC plans might be in the segment placing algorithm and optimization process not controllable by the user.…”

Section: Discussionmentioning

confidence: 99%

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Treatment planning for MLC based robotic radiosurgery for brain metastases: plan comparison with circular fields and suggestions for planning strategies

Schmitt

Shafie

Klüter

et al. 2017

Current Directions in Biomedical Engineering

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Abstract:To evaluate the possible range of application of the new InCise2 MLC for the CyberKnife M6 system in brain radiosurgery, a plan comparison was made for 10 brain metastases sized between 1.5 and 9cm 3 in 10 patients treated in a single fraction each. The target volumes consist of a PTV derived by expanding the GTV by 1mm and were chosen to have diversity in the cohort regarding regularity of shape, location and the structures needed to be blocked for beam transmission in the vicinity. For each case, two treatment plans were optimized: one using the MLC and one using the IRIS-collimator providing variable circular fields. Plan requirements were: dose prescription to the 70% isodose line (18 or 20Gy), 100% GTV coverage, ≥98% PTV coverage, undisturbed central high dose region (95% of maximum dose) and a conformity index as low as possible.

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Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

Treatment planning for MLC based robotic radiosurgery for brain metastases: plan comparison with circular fields and suggestions for planning strategies

Schmitt

Shafie

Klüter

et al. 2017

Current Directions in Biomedical Engineering

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“…Since 2015, in addition to the conventional fixed and variable‐aperture (Iris) collimators, the InCise2‐multileaf collimator (MLC) has been implemented in the CK M6 system, which consists of 26 leaf pairs with each leaf projecting a width of 3.85 at 800 mm source‐to‐axis distance. The InCise2‐MLC has been reported to have advantages such as reducing the treatment duration by reducing the total number of beams and monitor unit (MU) values . In addition, tumor‐tracking radiotherapy can be used to treat tumors in the organs that are affected by respiratory motions, such as the lung and liver .…”

Section: Introductionmentioning

confidence: 99%

“…The InCise2-MLC has been reported to have advantages such as reducing the treatment duration by reducing the total number of beams and monitor unit (MU) values. [4][5][6] In addition, tumor-tracking radiotherapy can be used to treat tumors in the organs that are affected by respiratory motions, such as the lung and liver. 7 However, in the previous TPS for CK (MultiPlan; Accuray Inc., Sunnyvale, CA, USA), MLC-based CK treatment plans could be created only by using the finite-size pencil beam (FSPB) algorithm.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

et al. 2020

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Purpose In the previous treatment planning system (TPS) for CyberKnife (CK), multileaf collimator (MLC)‐based treatment plans could be created only by using the finite‐size pencil beam (FSPB) algorithm. Recently, a new TPS, including the FSPB with lateral scaling option (FSPB+) and Monte Carlo (MC) algorithms, was developed. In this study, we performed basic and clinical end‐to‐end evaluations for MLC‐based CK tumor‐tracking radiotherapy using the MC, FSPB+, and FSPB. Methods Water‐ and lung‐equivalent slab phantoms were combined to obtain the percentage depth dose (PDD) and off‐center ratio (OCR). The CK M6 system and Precision TPS were employed, and PDDs and OCRs calculated by the MC, FSPB+, and FSPB were compared with the measured doses obtained for 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields. A lung motion phantom was used for clinical evaluation and MLC‐based treatment plans were created using the MC. The doses were subsequently recalculated using the FSPB+ and FSPB, while maintaining the irradiation parameters. The calculated doses were compared with the doses measured using a microchamber (for target doses) or a radiochromic film (for dose profiles). The dose volume histogram (DVH) indices were compared for all plans. Results In homogeneous and inhomogeneous phantom geometries, the PDDs calculated by the MC and FSPB+ agreed with the measurements within ±2.0% for the region between the surface and a depth of 250 mm, whereas the doses calculated by the FSPB in the lung‐equivalent phantom region were noticeably higher than the measurements, and the maximum dose differences were 6.1% and 4.4% for the 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields, respectively. The maximum distance to agreement values of the MC, FSPB+, and FSPB at the penumbra regions of OCRs were 1.0, 0.6, and 1.1 mm, respectively, but the best agreement was obtained between the MC‐calculated curve and measurements at the boundary of the water‐ and lung‐equivalent slabs, compared with those of the FSPB+ and FSPB. For clinical evaluations using the lung motion phantom, under the static motion condition, the dose errors measured by the microchamber were −1.0%, −1.9%, and 8.8% for MC, FSPB+, and FSPB, respectively; their gamma pass rates for the 3%/2 mm criterion comparing to film measurement were 98.4%, 87.6%, and 31.4% respectively. Under respiratory motion conditions, there was no noticeable decline in the gamma pass rates. In the DVH indices, for most of the gross tumor volume and planning target volume, significant differences were observed between the MC and FSPB, and between the FSPB+ and FSPB. Furthermore, significant differences were observed for lung Dmean, V15 Gy, and V20 Gy between the MC, FSPB+, and FSPB. Conclusions The results indicate that the doses calculated using the MC and FSPB+ differed remarkably in inhomogeneous regions, compared with the FSPB. Because the MC was the most consistent with the measurements, it is recommended for final dose calculations in inhomogeneous regions such as the lung. Furthermore, the sufficient accurac...

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“…MLC can be considered for multiple brain tumors because fields are shaped to match the tumor closely and the delivery time is reduced. However, due to a limit of leaf width (3.85 mm), it is hard to cover the small size tumor and small 2,3) For target coverage, the fixed collimator can be a useful modality but it is challenging when patientspecific quality assurance (PSQA) is performed because of lateral electronic disequilibrium, steep dose gradients, and complex dose distribution generated by multi-directional beams. 4,5) To overcome these issues, we focus on PSQA for multiple brain tumors with small circular photon beams of diameter 5 to 25 mm in CyberKnife with a fixed collimator.…”

Section: Introductionmentioning

confidence: 99%

Practical Implementation of Patient-Specific Quality Assurance for Small and Multiple Brain Tumors in CyberKnife with Fixed Collimators

et al. 2018

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This paper evaluates patient-specific quality assurance (PSQA) in the treatment of small and multiple tumors by the CyberKnife system with fixed collimators, using an ion chamber and EBT3 films. We selected 49 patients with single or multiple brain tumors, and the treatment plans include one to four targets with total volumes ranging from 0.12 cc to 3.74 cc. All PSQA deliveries were performed with a stereotactic dose verification phantom. The A16 microchamber (Standard Imaging, WI, USA) and Gafchromic EBT3 film (Ashland ISP Advanced Materials, NJ, USA) were inserted into the phantom to measure the point dose of the target and the dose distribution, respectively. The film was scanned 1 hr after irradiation by a film digitizer scanner and analyzed using RIT software (Radiological Imaging Technology, CO, USA). The acceptance criteria was <5% for the point dose measurement and >90% gamma passing rate using 3%/3 mm and relative dose difference, respectively. The point dose errors between the calculated and measured dose by the ion chamber were in the range of −17.5% to 8.03%. The mean point dose differences for 5 mm, 7.5 mm, and 10 mm fixed cone size was −11.1%, −4.1%, and −1.5%, respectively. The mean gamma passing rates for all cases was 96.1%. Although the maximum dose distribution of multiple targets was not shown in the film, gamma distribution showed that dose verification for multiple tumors can be performed. The use of the microchamber and EBT3 film made it possible to verify the dosimetric and mechanical accuracy of small and multiple targets. In particular, the correction factors should be applied to small fixed collimators less than 10 mm.

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Dosimetric comparison between cone/Iris‐based and InCise MLC‐based CyberKnife plans for single and multiple brain metastases

Cited by 42 publications

References 30 publications

Treatment planning for MLC based robotic radiosurgery for brain metastases: plan comparison with circular fields and suggestions for planning strategies

Treatment planning for MLC based robotic radiosurgery for brain metastases: plan comparison with circular fields and suggestions for planning strategies

Evaluation of newly implemented dose calculation algorithms for multileaf collimator‐based CyberKnife tumor‐tracking radiotherapy

Practical Implementation of Patient-Specific Quality Assurance for Small and Multiple Brain Tumors in CyberKnife with Fixed Collimators

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