Technical Note: Evaluation of the systematic accuracy of a frameless, multiple image modality guided, linear accelerator based stereotactic radiosurgery system

Wen, Ning; Snyder, Karen; Scheib, Stefan; Schmelzer, P.; Qin, Y; Li, H.; Siddiqui, M. Salim; Chetty, Indrin J.

doi:10.1118/1.4947199

Cited by 20 publications

(22 citation statements)

References 42 publications

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“…On a Linac based SRS system, Kim et al showed that the localization accuracy was 1.2 ± 0.3 mm using the ExacTrac X-ray image guidance system on a NovalisTx™ Linac [10]. Previous work at our institution investigated the end-to-end localization accuracy of a cone beam CT-guided Linac system and showed an uncertainty of 0.5 ± 0.2 mm with a maximum deviation of 0.9 mm [26]. The overall accuracy of the MR-Linac is comparable to other frameless based SRS systems.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Wen

Kim

Doemer

et al. 2018

Radiotherapy and Oncology

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Introduction: The purpose of this study was to investigate the systematic localization accuracy, treatment planning capability, and delivery accuracy of an integrated magnetic resonance imaging guided Linear Accelerator (MR-Linac) platform for stereotactic radiosurgery. Materials and methods: The phantom for the end-to-end test comprises three different compartments: a rectangular MR/CT target phantom, a Winston–Lutz cube, and a rectangular MR/CT isocenter phantom. Hidden target tests were performed at gantry angles of 0, 90, 180, and 270 degrees to quantify the systematic accuracy. Five patient plans with a total of eleven lesions were used to evaluate the dosimetric accuracy. Single-isocenter IMRT treatment plans using 10–15 coplanar beams were generated to treat the multiple metastases. Results: The end-to-end localization accuracy of the system was 1.0 ± 0.1 mm. The conformity index, homogeneity index and gradient index of the plans were 1.26 ± 0.22, 1.22 ± 0.10, and 5.38 ± 1.44, respectively. The average absolute point dose difference between measured and calculated dose was 1.64 ± 1. 90%, and the mean percentage of points passing the 3%/1 mm gamma criteria was 96.87%. Conclusions: Our experience demonstrates that excellent plan quality and delivery accuracy was achievable on the MR-Linac for treating multiple brain metastases with a single isocenter.

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Section: Discussionmentioning

confidence: 99%

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Wen

Kim

Doemer

et al. 2018

Radiotherapy and Oncology

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“…1,[15][16][17][18][19][20] To characterize the accuracy of our system prior to ACO and CIB, we wanted to determine which portion of the RTDs seen at non-zero couch angles were due to couch walkout. 1,[15][16][17][18][19][20] To characterize the accuracy of our system prior to ACO and CIB, we wanted to determine which portion of the RTDs seen at non-zero couch angles were due to couch walkout.…”

Section: Methodsmentioning

confidence: 99%

“…Numerous phantom studies have been performed to assess the accuracy of OSMS. 1,[15][16][17][18][19][20] To characterize the accuracy of our system prior to ACO and CIB, we wanted to determine which portion of the RTDs seen at non-zero couch angles were due to couch walkout. OSMS report was taken.…”

Section: Intrafraction Tracking With Osms Requires the Use Of An Openmentioning

confidence: 99%

“…[1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases. [1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases.…”

Section: Introductionmentioning

confidence: 99%

“…Frameless radiosurgery has been used to improve patient comfort during treatment and has been shown to have the same level of positional accuracy as framed treatments. [1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases. 6 Due to the use of a headrest and mask in place of an invasive headframe, imaging during treatment via x-ray or optical guidance has been used to monitor intrafraction motion.…”

Section: Introductionmentioning

confidence: 99%

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Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy

Covington

Fiveash

et al. 2019

J Applied Clin Med Phys

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Purpose To evaluate the accuracy of monitoring intrafraction motion during stereotactic radiotherapy with the optical surface monitoring system. Prior studies showing a false increase in the magnitude of translational offsets at non‐coplanar couch positions prompted the vendor to implement software changes. This study evaluated two software improvements intended to address false offsets. Methods The vendor implemented two software improvements: a volumetric (ACO) rather than planar calibration and, approximately 6 months later, an improved calibration workflow (CIB) designed to better compensate for thermal drift. Offsets relative to the reference position, obtained at table angle 0 following image‐guided setup, were recorded before beam‐on at each table position and at the end of treatment the table returned to 0° for patients receiving SRT. Results Prior to ACO, between ACO and CIB, and after CIB, 223, 155, and 436 fractions were observed respectively. The median magnitude of translational offsets at the end of treatment was similar for all three intervals: 0.29, 0.33, and 0.27 mm. Prior to ACO, the offset magnitude for non‐zero table positions had a median of 0.79 mm and was found to increase with increasing distance from isocenter to the anterior patient surface. After ACO, the median magnitude was 0.74 mm, but the dependence on surface‐to‐isocenter distance was eliminated. After CIB, the median magnitude for non‐zero table positions was reduced to 0.57 mm. Conclusion Ongoing improvements in software and calibration procedures have decreased reporting of false offsets at non‐zero table angles. However, the median magnitude for non‐zero table angles is larger than that observed at the end of treatment, indicating that accuracy remains better when the table is not rotated.

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The spatial accuracy of two frameless, linear accelerator‐based systems for single‐isocenter, multitarget cranial radiosurgery

Ezzell

2017

J Applied Clin Med Phys

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Single‐isocenter, multitarget cranial stereotactic radiosurgery (SRS) is more efficient than using an isocenter for each target, but spatial positioning uncertainties can be magnified at locations away from the isocenter. This study reports on the spatial accuracy of two frameless, linac‐based SRS systems for multitarget, single‐isocenter SRS as a function of distance from the isocenter. One system uses the ExacTrac platform for image guidance and the other localizes with cone beam computed tomography (CBCT). For each platform, a phantom with 12 target BBs distributed up to 13.8 cm from the isocenter was aligned starting from five different initial offsets and then imaged with the treatment beam at seven different gantry and couch angles. The distribution of the resulting positioning errors demonstrated the value of adding a 1‐mm PTV margin for targets up to about 7–8 cm from the isocenter. For distances 10 cm or more, the CBCT‐based alignment remained within 1.1 mm while the ExacTrac‐based alignment differed by up to 2.2 mm.

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Technical Note: Evaluation of the systematic accuracy of a frameless, multiple image modality guided, linear accelerator based stereotactic radiosurgery system

Abstract: The authors' experience demonstrates that the localization accuracy of the frameless image-guided system is comparable to robotic or invasive frame based radiosurgery systems.

Cited by 20 publications

References 42 publications

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy

The spatial accuracy of two frameless, linear accelerator‐based systems for single‐isocenter, multitarget cranial radiosurgery

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