A closer look at the conventional Winston-Lutz test: Analysis in terms of dose

Calvo-Ortega, J.F.; Moragues-Femenía, S.; Laosa-Bello, C.; José-Maderuelo, Sol San; Casals-Farran, J.

doi:10.1016/j.rpor.2019.07.003

Cited by 16 publications

(9 citation statements)

References 12 publications

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“…In this way, VIPER is able to detect discrepancies between the planned and the actual beam delivery onto a virtual cylindrical water phantom, excluding the potential couch rotation inaccuracy. This issue has to be controlled using an additional check, as for instance the Winston-Lutz test that we perform in our clinical practice [39]; 3. Rodriguez et al defined a metric named dose-volume histogram (DVH) percentage of agreement (PA), and showed that it was more sensitive than GPR to detect dosimetric errors [40].…”

Section: Discussionmentioning

confidence: 99%

Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure

Calvo-Ortega

Greer

Moragues-Femenía

et al. 2022

Rep Pract Oncol Radiother.

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Background:The purpose of this study was to describe the use of the VIPER software for patient-specific quality assurance (PSQA) of single-isocenter multitarget (SIMT) stereotactic radiosurgery (SRS) plans. Materials and methods:Twenty clinical of intensity-modulated (IMRT) SIMT SRS plans were reviewed. A total of 88 brain metastases were included. Number of lesions per plan and their individual volumes ranged from 2 to 35 and from 0.03 to 32.8 cm 3 , respectively. Plans were designed with the Eclipse system, and delivered using a Varian CLINAC linac. SRS technique consisted of non-coplanar static-field sliding-window IMRT.Each plan was mapped onto a virtual cylindrical water phantom (VCP) in the Eclipse to calculate a 3D dose distribution (verification plan). The VIPER software reconstructed the 3D dose distribution inside the VCP from the acquired in-air electronic portal image device (EPID) images of the treatment fields.A 3D gamma analysis was used to compare the reconstructed doses to the Eclipse planned doses on the VCP. Gamma passing rates (GPRs) were calculated using 3% global/2 mm criteria and dose thresholds ranged from 10% to 90% of the maximum dose. Results:The averages (± 1 SD) of the 3D GPRs over the 20 SRS plans were: 99.9 ± 0.2%, 99.7 ± 0.3%, 99.6 ± 0.5%, 99.3 ± 0.9%,99.1 ± 1.6%, 99.0 ± 1.6%, and 98.5 ± 3.3%, for dose thresholds of 10%, 20%, 30%, 50%, 70%, 80% and 90% respectively. Conclusions:This work shows the feasibility of the VIPER software for PSQA of SIMT SRS plans, being a reliable alternative to commercially available 2D detector arrays.

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Section: Discussionmentioning

confidence: 99%

Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure

Calvo-Ortega

Greer

Moragues-Femenía

et al. 2022

Rep Pract Oncol Radiother.

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“…Delivery of HyperArc™ patient plans in this project consisted of four arcs with 3 couch-kicks ± 45° and 90° from the sagittal plane. The kV/MV isocenter coincidence was checked through the Winston-Lutz (WL) test [29] before HyperArc™ delivery. AAPM TG 142 [19] was referenced for the tolerances on the mechanical checks.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of HyperArc™ using film and portal dosimetry quality assurance

Kamst

Desai

2022

Phys Eng Sci Med

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HyperArc ™ is a stereotactic radiotherapy modality designed for targeting multiple brain metastases using a single isocenter with multiple non-coplanar arcs. The purpose of this study was to assess the e cacy of two patient speci c quality assurance methods, lm and the Varian Portal Dosimetry System with Varian's HyperArc ™ technique and raise important considerations in the customisation of patient speci c quality assurance to accommodate HyperArc ™ delivery. Assessment criteria included gamma analysis and mean dose at full width half maximum. The minimum met size, maximum off-axis distance and suitable energy were identi ed and validated. Patient speci c quality assurance procedures were applied to a range of clinically relevant brain met plans. Initial investigation into energy selection showed no signi cant differences in gamma pass rates using 6MV, 6MV FFF or 10MV FFF for met sizes greater than 15 mm diameter at the isocenter. Gamma pass rates (2%/2mm) for 15 mm mets at the isocenter for all energies were greater than 96.0% for portal dosimetry and greater than 98.7% for lm. Fields of size 15 mm placed at various distances (10-70 mm) from the isocenter resulted in a maximum mean dose difference of 1.5% between lm and planned. Clinically relevant plans resulted in maximum mean dose difference for selected mets of 1.0% between lm and plan and maximum point dose difference of 2.9% between portal dose and plan. Portal dose image prediction was found to be a quick and convenient quality assurance tool for mets larger than 15 mm near the isocenter but provided diminished geometrical relevance for off-axis mets. Film QA required exacting procedures but offered the ability to assess the accuracy of geometrical targeting for off-axis mets and provided dosimetric accuracy for mets to well below 15 mm diameter.

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“…Prior to treatment with stereotactic conical collimator, a pre-treatment modified Winston-Lutz test (cardinal angles only) and ExacTrac verification test are performed [ 9 ]. The test is performed with a 7.5-mm conical collimator and a 5-mm radiopaque pointer.…”

Section: Methodsmentioning

confidence: 99%

Intra-Fraction Motion Management for Radiosurgical Treatments of Trigeminal Neuralgia: Clinical Experience, Imaging Frequency, and Motion Analysis

Agazaryan¹,

Tenn²,

Pouratian³

et al. 2021

Cureus

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The aim of this study is to evaluate the patient positioning and intra-fraction motion management performance of an image-guidance protocol established for radiosurgical treatments of trigeminal neuralgia patients. Specifically, it also aims to analyze patient motion data for the evaluation of current motion tolerance levels and imaging frequency utilized for repositioning patients. MethodsA linear accelerator equipped with ExacTrac is used for patient positioning with stereoscopic imaging and treatments. Treatments are delivered with 4-mm conical collimators using seven equally spaced arcs. Arcs are 20 degrees apart and span 100 arc degrees each. Following initial ExacTrac positioning, cone beam computed tomography (CBCT) is obtained for independent confirmation of patient position. Patients are then stereoscopically imaged prior to the delivery of each arc and repositioned when 0.5-mm translational tolerance in any direction is exceeded. After the patient has been repositioned, verification stereoscopic images are obtained. Data from 48 patients with 607 image pairs were analyzed for this study. ResultsOver the course of 48 patient treatments, the mean magnitude of mean 3D deviations was 0.64 mm ± 0.12 mm (range: 0.07-2.74 mm). With the current 0.50-mm tolerance level for repositioning, patients exceeded the tolerance 51.4% of the time considering only images following an arc segment. For those instances, patients were repositioned with a mean magnitude of 0.85 mm ± 0.15 mm (1 SD). For a 0.25-mm tolerance level, 86.1% of arc segments would have required repositioning following the delivery of an arc segment, with a mean magnitude of 0.68 mm ± 0.12 mm. Conversely, for 0.75-mm and 1.00-mm tolerance levels, the tolerance would have been exceeded only 21.5% and 6.6% of instances following the delivery of an arc segment, with a mean magnitude of 1.08 mm ± 0.21 mm and 1.34 mm ± 0.24 mm, respectively. Each repositioning adds approximately 2 minutes to treatment time, which accounts for parts of the variability in patient treatment times. Following the initial ExacTrac and CBCT, the mean treatment time from first arc to treatment end was 57 minutes (range: 33-63 minutes).

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A closer look at the conventional Winston-Lutz test: Analysis in terms of dose

Cited by 16 publications

References 12 publications

Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure

Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure

Evaluation of HyperArc™ using film and portal dosimetry quality assurance

Intra-Fraction Motion Management for Radiosurgical Treatments of Trigeminal Neuralgia: Clinical Experience, Imaging Frequency, and Motion Analysis

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