A simplified and effective off‐axis Winston–Lutz for single‐isocenter multi‐target SRS

Eagle, A.; Tallhamer, Mike; Keener, Justin; Geneser, Sarah

doi:10.1002/acm2.13816

Cited by 6 publications

(4 citation statements)

References 9 publications

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“…It might be attribute to a chance as this is only a single measurement at each iso‐to‐target center distance without uncertainty analysis. Clearly, this unexpectedly improved target accuracy is not significant, it is lying within the system uncertainty from Winston‐Lutz test 22 data (Figure 3 ) for the cube phantom at the Isocenter (0.69 ± 0.38 mm) and off‐Isocenter position (1.01 ± 0.19 mm). The targeting accuracy for 0 and 0.5 degrees was almost constant as a function of the distance between the isocenter and the target.…”

Section: Resultssupporting

confidence: 55%

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Li,

Mail,

Stefania diMayorca

et al. 2023

J Applied Clin Med Phys

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Purpose/objectives(A) To examine the alignment accuracy of CBCT guidance for brain metastases with off centered isocenters, (B) to test dose delivery and targeting accuracy for single isocenter treatments with multiple brain metastases. We report the results of the end‐to‐end test for Truebeam stereotactic radiosurgery (SRS).Materials/methodsAn anthropomorphic CT head phantom was drilled with five MOSFET inserts and two PTW Pinpoint chamber inserts. The phantom was simulated, planned, and delivered. For the purpose of comparing the accuracy of alignment, CBCTs were acquired with the isocenter centered and offset superiorly 8 cm, inferiorly 8 cm, anteriorly 7 cm, posteriorly 7 cm, and right 5 cm. There were six degrees of freedom corrections applied to the plans, as well as intentional rotational and translational errors for dose comparisons. Dose accuracy checks were performed with MOSFET and PTW Pinpoint chamber, and targeting accuracy was assessed with GafChromic films.Result(A) Compared to centered CBCT, off‐centered CBCT scan showed some alignment errors, with a maximum difference of 0.6‐degree pitch and 0.9 mm translation when the phantom was placed 8 cm inferior off center. (B) For the single isocenter plan, measured doses of the five MOSFET were 95%–100% of the planned dose, whereas the multiple isocenter plans were 96%–100%. With intentional setup errors of 1‐degree pitch, doses were 97.1%–100.4% compared to the perfect setup. The same was found for the two pinpoint chamber readings with 1‐degree rotation and 1 mm translation. (C) Targeting accuracy for targets at the isocenter is 0.67 mm, within the machine specification of 0.75 mm. Targeting accuracy for isocenters 6–12 cm away from the target is in the range 0.67–1.18 mm.Conclusion(A) Single isocenter HyperArc treatments for multiple brain metastases are feasible and targeting accuracy is clinically acceptable. (B) The vertex in a cranial scan is very important for proper alignment.

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Section: Resultssupporting

confidence: 55%

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Li,

Mail,

Stefania diMayorca

et al. 2023

J Applied Clin Med Phys

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“…Eagle et al [31] investigated the outcomes of off-axis Winston-Lutz tests, utilizing DoseLab Pro (Version 6.7) and an EPID on a TrueBeam system. In single-isocenter multitarget SRS, a significant challenge arises from the potential inaccuracy in targeting off-axis targets, which can be attributed to the decrease in accuracy with increasing off-axis distance.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, verifying the precision of off-axis isocenter positioning becomes critical for safely treating multiple off-axis targets. Eagle et al [31] introduced a method for conducting off-axis Winston-Lutz tests to assess SRS delivery accuracy at various off-axis distances. However, the MPC test cannot provide data regarding the off-axis isocenter.…”

Section: Discussionmentioning

confidence: 99%

Evaluating the Efficacy of Machine Performance Checks as an Alternative to Winston–Lutz Quality Assurance Testing in the TrueBeam Linear Accelerator with HyperArc

Kim,

Park

et al. 2024

Diagnostics

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HyperArc is a preferred technique for treating brain metastases, employing a single isocenter for multiple lesions. Geometrical isocentricity in the TrueBeam linear accelerator with HyperArc is crucial. We evaluated machine performance checks (MPCs) as an alternative to the Winston–Lutz (WL) test to verify the treatment isocenter. Between January and July 2023, we assessed 53 data points using MPC and Winston–Lutz tests. The isocenter size obtained from the MPC and its sum, including the rotation-induced couch shift, were compared with the maximum total delta value from the Winston–Lutz test. The maximum total delta was 0.68 ± 0.10 mm, while the isocenter size was 0.28 ± 0.02 mm. The sum of the isocenter size and rotation-induced couch shift measured by MPC was 0.61 ± 0.03 mm. During the Winston–Lutz test (without couch rotation), the maximum total delta value was 0.56 ± 0.13 mm. A t-test analysis revealed a significant difference in the isocenter size averages between the Winston–Lutz and MPC outcomes, whereas the Pearson’s correlation coefficient yielded no correlation. Our study highlights the necessity for separate MPC and Winston–Lutz tests for isocenter verification. Therefore, the Winston–Lutz test should precede stereotactic radiosurgery for isocenter verification.

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“…15,16 Many efforts have recently been made to evaluate the off-axis accuracy of the WL test by phantoms in linacs. 1,7,17,18 One of the most important features to consider is the use of image-guided radiotherapy (IGRT) like cone-beam computed tomography (CBCT) or stereoscopic X-ray imaging, for example ExacTrac ™ system (Brainlab AG, Munich, Germany). ExacTrac ™ provides faster imaging, 19 lower dose exposure 20 and image guidance for non-coplanar treatments.…”

Section: Introductionmentioning

confidence: 99%

Experimental determination of set-up displacements in anthropomorphic phantom in single-isocentre radiosurgery for multiple brain metastases by off-axis Winston–Lutz test: ExacTrac^TM v.6 versus Dynamic^TM

Rojas-López

Chesta

Venencia³

2023

J Radiother Pract

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Purpose: We compare the accuracy of the off-axis Winston–Lutz (WL) test in two versions of ExacTracTM: version 6.0 (ETv6) and Dynamic (ETD) in the same linac (TrueBeam STx®). Materials and methods: An upgraded of the ExacTracTM system was done in our institution. It was designed as an off-axis WL test before the update for comparison purposes. A head 3D-printed phantom based on a patient’s computed tomography images was used. Nine metallic fiducials were inserted and distributed on the phantom. Each target (fiducial) was designed an off-axis WL test with eight different gantry/collimator/table combinations. The phantom was placed using two different ETv6 and ETD in the same linac, and cone-beam computed tomography and electronic portal imaging device (EPID) images were acquired. The 2D deviation between the centre of the fiducial and the radiation field was found and compared with the original digital reconstructed radiography (DRR) by the profiles. Results: The phantom allows the definition of a procedure to determine off-axis deviations in radiosurgery treatments. The displacements calculated from the WL test showed acceptable values for both versions taking into account 3D displacement tolerances of 1 mm. These values were reached with rigorous quality assurance (QA) linac tests performed routinely that include mechanical, MV/kV and image-guided radiotherapy (IGRT) tests. However, ETD indicated more accurate values for all the targets no matter the distance to the isocentre (3D displacements < 0·5 mm). Conclusion: In terms of the IGRT correction without set-up displacements, ETD is up to twice as accurate as the ETv6, showing 3D displacements up to 0·5 mm in all targets.

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A simplified and effective off‐axis Winston–Lutz for single‐isocenter multi‐target SRS

Cited by 6 publications

References 9 publications

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Evaluating the Efficacy of Machine Performance Checks as an Alternative to Winston–Lutz Quality Assurance Testing in the TrueBeam Linear Accelerator with HyperArc

Experimental determination of set-up displacements in anthropomorphic phantom in single-isocentre radiosurgery for multiple brain metastases by off-axis Winston–Lutz test: ExacTrac^TM v.6 versus Dynamic^TM

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A simplified and effective off‐axis Winston–Lutz for single‐isocenter multi‐target SRS

Cited by 6 publications

References 9 publications

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Evaluating the Efficacy of Machine Performance Checks as an Alternative to Winston–Lutz Quality Assurance Testing in the TrueBeam Linear Accelerator with HyperArc

Experimental determination of set-up displacements in anthropomorphic phantom in single-isocentre radiosurgery for multiple brain metastases by off-axis Winston–Lutz test: ExacTracTM v.6 versus DynamicTM

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Experimental determination of set-up displacements in anthropomorphic phantom in single-isocentre radiosurgery for multiple brain metastases by off-axis Winston–Lutz test: ExacTrac^TM v.6 versus Dynamic^TM