Lung Metastases Treated by CyberKnife® Image-Guided Robotic Stereotactic Radiosurgery at 41 Months

Brown, W. Ted; Wu, Xiaodong; Fowler, J. F.; García, Silvio; Fayad, Fahed; Amendola, Beatriz E.; Zerda, Alberto de la; Schwade, James G.

doi:10.1097/smj.0b013e318167ad8d

Cited by 50 publications

(32 citation statements)

References 32 publications

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“…Stereotactic radiosurgery (SRS), intensity‐modulated radiation therapy (IMRT), and volumetric‐modulated arc therapy (VMAT) can deliver high doses to targets while minimizing doses to nearby organs at risk (OAR) 1 , 2 , 3 . Owing to the complexity of these techniques and patient exposure to high doses, patient‐specific quality assurance (QA) for these treatment techniques is important for confirming the dose distribution, mainly in areas with high‐dose gradients near OARs.…”

Section: Introductionmentioning

confidence: 99%

Gafchromic EBT‐XD film: Dosimetry characterization in high‐dose, volumetric‐modulated arc therapy

Miura¹,

Ozawa

Hosono³

et al. 2016

J Applied Clin Med Phys

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Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT‐XD films have been designed for optimal performance in the 40–4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose‐response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high‐dose volumetric‐modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0–4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter‐free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose‐rate dependence. For clinical examinations, we compared the dose distribution measured with EBT‐XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT‐XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ∼3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ∼1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ∼1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film‐ measured and treatment planning system (TPS)‐calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%.PACS number(s): 87.56 Fc

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Section: Introductionmentioning

confidence: 99%

Gafchromic EBT‐XD film: Dosimetry characterization in high‐dose, volumetric‐modulated arc therapy

Miura¹,

Ozawa

Hosono³

et al. 2016

J Applied Clin Med Phys

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“…Small margins could result in underdosing, whereas large margins lead to more normal tissue than necessary being irradiated. A range of between 2 mm and 8 mm has been proposed and applied by different members of the CyberKnife community 13 , 14 , 15 , 16 , 17 . At our center, we generally use 5 mm for all three directions (superior/inferior (SI), anterior/posterior (AP), and lateral (LAT)), with manual modifications, depending on the proximity of the organ at risk.…”

Section: Introductionmentioning

confidence: 99%

Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors

Floriano

García²,

Moreno³

et al. 2014

J Applied Clin Med Phys

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The objectives of this study were to estimate global uncertainty for patients with thoracic tumors treated in our center using the CyberKnife VSI after placement of fiducial markers and to compare our findings with the standard CTV to PTV margins used to date. Datasets for 16 patients (54 fractions) treated with the CyberKnife and the Synchrony Respiratory Tracking System were analyzed retrospectively based on CT planning, tracking information, and movement data generated and saved in the logs files by the system. For each patient, we analyzed all the main uncertainty sources and assigned a value. We also calculated an expanded global uncertainty to ensure a robust estimation of global uncertainty and to enable us to determine the position of 95% of the CTV points with a 95% confidence level during treatment. Based on our estimation of global uncertainty and compared with our general margin criterion (5 mm in all three directions: superior/inferior [SI], anterior/posterior [AP], and lateral [LAT]), 100% were adequately covered in the LAT direction, as were 94% and 94% in the SI and AP directions. We retrospectively analyzed the main sources of uncertainty in the CyberKnife process patient by patient. This individualized approach enabled us to estimate margins for patients with thoracic tumors treated in our unit and compare the results with our standard 5 mm margin.PACS number: 87.55‐x

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“…6 For gantry based Stereotactic radiosurgery (SRS), margins can be as high as 2 cm in order to ensure adequate dosage to the tumor. 7,8 A reduction in margin can reduce lung toxicity, which has been reported with TD 5=5 limits of 15 Gy to 50% and 20 Gy to 35%. 9 Various clinical practices have been employed using image tracking to reduce the margin needed for effective radiation delivery.…”

Section: Introductionmentioning

confidence: 99%

“…6); common margins are 3-5 mm. 1,7,8 At CyberKnife of Indianapolis, 7 mm margins are used in the SI direction and 5 mm margins are used in the AP and LAT directions; for some patients with tumors in the lung apex, 5 mm margins are used in the SI direction as well.…”

Section: Introductionmentioning

confidence: 99%

Correlation and prediction uncertainties in the CyberKnife Synchrony respiratory tracking system

et al. 2011

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Purpose: The CyberKnife uses an online prediction model to improve radiation delivery when treating lung tumors. This study evaluates the prediction model used by the CyberKnife radiation therapy system in terms of treatment margins about the gross tumor volume (GTV). Methods: From the data log files produced by the CyberKnife synchrony model, the uncertainty in radiation delivery can be calculated. Modeler points indicate the tracked position of the tumor and Predictor points predict the position about 115 ms in the future. The discrepancy between Predictor points and their corresponding Modeler points was analyzed for 100 treatment model data sets from 23 de-identified lung patients. The treatment margins were determined in each anatomic direction to cover an arbitrary volume of the GTV, derived from the Modeler points, when the radiation is targeted at the Predictor points. Each treatment model had about 30 min of motion data, of which about 10 min constituted treatment time; only these 10 min were used in the analysis. The frequencies of margin sizes were analyzed and truncated Gaussian normal functions were fit to each direction's distribution. The standard deviation of each Gaussian distribution was then used to describe the necessary margin expansions in each signed dimension in order to achieve the desired coverage. In this study, 95% modeler point coverage was compared to 99% modeler coverage. Two other error sources were investigated: the correlation error and the targeting error. These were added to the prediction error to give an aggregate error for the CyberKnife during treatment of lung tumors. Results: Considering the magnitude of 2r from the mean of the Gaussian in each signed dimension, the margin expansions needed for 95% modeler point coverage were 1.2 mm in the lateral (LAT) direction and 1.7 mm in the anterior-posterior (AP) direction. For the superior-inferior (SI) direction, the fit was poor; but empirically, the expansions were 3.5 mm. For 99% modeler point coverage, the AP margin was 3.6 mm and the lateral margin was 2.9 mm. The SI margins for 99% modeler point coverage were highly variable. The aggregate error at 95% was 6.9 mm in the SI direction, 4.6 mm in the AP direction, and 3.5 in the lateral direction. Conclusions: The Predictor points follow the Modeler points closely. Margins were found in each clinical direction that would provide 95% modeler point coverage for 95% of the models reviewed in this study. Similar margins were found in two clinical directions for 99% modeler point coverage in 95% of models. These results can offer guidance in the selection of CTV margins for treatment with the CyberKnife.

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Lung Metastases Treated by CyberKnife® Image-Guided Robotic Stereotactic Radiosurgery at 41 Months

Cited by 50 publications

References 32 publications

Gafchromic EBT‐XD film: Dosimetry characterization in high‐dose, volumetric‐modulated arc therapy

Gafchromic EBT‐XD film: Dosimetry characterization in high‐dose, volumetric‐modulated arc therapy

Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors

Correlation and prediction uncertainties in the CyberKnife Synchrony respiratory tracking system

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