Intrafraction variations in linac-based image-guided radiosurgery of intracranial lesions

Badakhshi, Harun; Barelkowski, Tomasz; Wust, Peter; Budach, Volker; Boehmer, Dirk; Graf, R.

doi:10.1016/j.canrad.2013.05.011

Cited by 14 publications

(13 citation statements)

References 15 publications

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“…Seravalli et al performed post treatmentCBCTs for 59 treatments and found an average translation magnitude of 0.6 mm 22. Badakhshi et al found an average translational intrafraction deviation of 1 mm using kV imaging with BrianLAB for 190 patients over 269 treatments 7. While both measured offsets larger than those reported in this study, the average timescale was reported to be 15 min in both studies versus 4.84 min in this study.Overall, OSMS was capable of recording submillimeter deviations from the patient's initial reference surface from beginning to end of treatment.While the magnitude of motion recorded by OSMS at the end of treatment was consistent with previous studies, larger than expected RTDs were observed during treatment, particularly at non-zero couch angles.…”

contrasting

confidence: 37%

“…[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. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for intrafraction motion. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for intrafraction motion.…”

Section: Introductionmentioning

confidence: 99%

“…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. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for 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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contrasting

confidence: 37%

Section: Introductionmentioning

confidence: 99%

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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“…In theory, the procedure can be applied to other modalities such as linear accelerator (LINAC)-based radiosurgical treatments, where residual target shifts have been studied for both intracranial and extracranial sites. 1,4,5,9,14 Since LINAC-based treatments tend to employ one or few isocenters, while GKRS employs a high number of isocenters (> 10), especially for treating a large target, the dose-averaging effect across different isocenters can be significantly different between GKRS and LINAC-based treatments. Future studies are therefore needed to quantify such differences and general applicability of the procedure.…”

Section: Discussionmentioning

confidence: 99%

A robustness check procedure for hypofractionated Gamma Knife radiosurgery

Chiu

Braunstein²,

Nakamura³

et al. 2018

Journal of Neurosurgery

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OBJECTIVEInterfractional residual patient shifts are often observed during the delivery of hypofractionated brain radiosurgery. In this study, the authors developed a robustness treatment planning check procedure to assess the dosimetric effects of residual target shifts on hypofractionated Gamma Knife radiosurgery (GKRS).METHODSThe residual patient shifts were determined during the simulation process immediately after patient immobilization. To mimic incorporation of residual target shifts during treatment delivery, a quality assurance procedure was developed to sample and shift individual shots according to the residual uncertainties in the prescribed treatment plan. This procedure was tested and demonstrated for 10 hypofractionated GKRS cases.RESULTSThe maximum residual target shifts were less than 1 mm for the studied cases. When incorporating such shifts, the target coverage varied by 1.9% ± 2.2% (range 0.0%–7.1%) and selectivity varied by 3.6% ± 2.5% (range 1.1%–9.3%). Furthermore, when incorporating extra random shifts on the order of 0.5 mm, the target coverage decreased by as much as 7%, and nonisocentric variation in the dose distributions was noted for the studied cases.CONCLUSIONSA pretreatment robustness check procedure was developed and demonstrated for hypofractionated GKRS. Further studies are underway to implement this procedure to assess maximum tolerance levels for individual patient cases.

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“…11 In another series, 12% of intrafraction values in the three dimensions were above 1 mm (range: À 5 mm to þ 5 mm). 12 Positional uncertainty in frameless radiosurgery can alter outcomes. Planning target volume (PTV) margins could be used in frameless SRS to minimize undertreatment.…”

Section: Discussionmentioning

confidence: 99%

Large In-mask Motion during Frameless Radiosurgery of a Brain Metastasis

Harat¹,

Furtak

2018

J Neurol Surg A Cent Eur Neurosurg

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Frameless radiosurgery is now a common alternative to traditional in-frame treatment. Several dosimetric studies have reported small in-mask positioning inaccuracies during frameless radiosurgery. We present a case of an uncommonly large deviation in in-mask motion detected offline in a patient undergoing linear accelerator-based frameless radiosurgery. Our case illustrates how the use of a thermoplastic mask can lead to unacceptable setup errors for passive image-guided radiosurgery. The case underlines the need for correct patient preparation, adequate time between mask molding and computed tomography, and routine intrafraction imaging. Image-guided positioning is recommended to achieve clinically acceptable setup accuracy (< 1 mm) for stereotactic radiosurgery.

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Intrafraction variations in linac-based image-guided radiosurgery of intracranial lesions

Cited by 14 publications

References 15 publications

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

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

A robustness check procedure for hypofractionated Gamma Knife radiosurgery

Large In-mask Motion during Frameless Radiosurgery of a Brain Metastasis

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