An integrated quality assurance phantom for frameless single-isocenter multitarget stereotactic radiosurgery

Capaldi, Dante P. I.; Skinner, Lawrie; Dubrowski, Piotr; Yu, Amy S.

doi:10.1088/1361-6560/ab8534

Cited by 17 publications

(13 citation statements)

References 42 publications

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“…15 In many cases, these phantoms cannot be irradiated from certain angles since the electronics are sensitive to radiation. 15,19,22 This limits their ability to measure true composite plans for patient-specific QA as recommended by the AAPM report TG-218. These phantoms also typically suffer from artifacts when scanned with a CT scanner so they must be virtually modeled in the treatment planning system until the results agree with measurements.…”

Section: C Electronic Phantomsmentioning

confidence: 99%

“…Various attempts have been made utilizing different commercial and non-commercial system to varying degrees of success. [10][11][12][13][14][15][16][17][18][19][20][21][22] Some of the more common and current methods and their limitations will be briefly discussed (Figs. 1-7).…”

Section: Introductionmentioning

confidence: 99%

“…Also, these detectors often suffer an angular dependence 3–5,15,21 that necessitates further application of correction factors 15 . In many cases, these phantoms cannot be irradiated from certain angles since the electronics are sensitive to radiation 15,19,22 . This limits their ability to measure true composite plans for patient‐specific QA as recommended by the AAPM report TG‐218.…”

Section: Introductionmentioning

confidence: 99%

“…Many of the currently available phantom systems have limited capacity to measure small and arbitrarily placed target volumes. Various attempts have been made utilizing different commercial and non‐commercial system to varying degrees of success 10–22 . Some of the more common and current methods and their limitations will be briefly discussed (Figs.…”

Section: Introductionmentioning

confidence: 99%

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The development and testing of a novel spherical radiotherapy phantom system for the commissioning and patient‐specific quality assurance of mono‐isocentric multiple mets SRS plans

McKenna

2020

Medical Physics

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Purpose To develop a single radiotherapy phantom system capable of performing both patient‐specific quality assurance (QA) measurements and commissioning measurements for mono‐isocentric LinAc‐based stereotactic radiosurgery (“mLSRS”) treatment plans. Methods DesignA 20‐cm diameter spherical phantom was designed which contained within it a film cartridge. The surface of the sphere was machined to display a set of angular markings at both the equator and the meridian representing a spherical coordinate system. A stand was designed which allows for free rotation about any vector passing through the center of the sphere. A program was created using Python 3 to: (a) Compute the measurement setup necessary to intersect exactly one film plane with three user specified dicom points contained within the QA plan; (b) Extract the intersection dose plane from the three dimensional DICOM dose file and; (c) Generate a synthetic computed tomography (CT) in the exact measurement geometry which is subsequently used for phantom positioning during the QA measurement. Testing To assess the functionality of the phantom system dynamic conformal arc mLSRS plans that were generated by a clinically commissioned multiple metastasis treatment planning system (BrainLab Elements version 2.0) using patient‐specific data. A total of seven patient plans were created that contained a total of 31 targets { = (0.382 ± 0.534) cc: Range [0.051, 2.05] cc, = (30 ± 16) mm: Range[0, 55] mm} 27 of which were directly measured with film and analyzed. Each planned isocenter was mapped to the phantom’s center and the dose was recomputed. From the phantom dose distribution dicom points of interest were selected in sets of three and input into the provided software. The software computed the plane that intersects with the entered three points and instructed the user on the setup geometry to place the film in the intersecting plane. The software then generated a synthetic CT scan with embedded fiducial markers rotated into the setup orientation. This CT was then used as the setup reference image in ExacTrac image guidance system (tolerance 0.7 mm & 0.5deg). All plans were delivered on a Varian Truebeam linear accelerator with HDMLC, Exactrac and a 6 degree of freedom couch. After delivery of each test plan a 10 × 10 reference field was delivered to a known dose approximately equal to the maximum dose contained within the plan for film calibration. The test film was scanned simultaneously with the 10 × 10 reference film and a film that received zero dose using an Epson 10000XL flatbed scanner after waiting 24 hours. The test film was scaled according to the reference film and analyzed via the gamma analysis (3%, 1 mm, 10%) implemented in Ashland Film QA Pro software. Results The spherical phantom system was able to perform validation measurements on a variety of patient‐specific plan geometries. The average gamma pass‐rate γ(3%, 1 mm,10%) for all measurements was 96.7% (σ = 3.6%). Conclusions A novel spherical radiotherapy phantom s...

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Section: C Electronic Phantomsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The development and testing of a novel spherical radiotherapy phantom system for the commissioning and patient‐specific quality assurance of mono‐isocentric multiple mets SRS plans

McKenna

2020

Medical Physics

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“…However, some QA programs are tedious and timeconsuming to complete with repeated phantom displacements and manual measurements. To enhance the QA efficiency for machine performance, streamlined QA is clinically essential and various methods have been proposed (7)(8)(9)(10). For instance, Varian has released a commercial module named Machine Performance Check (MPC) (Varian, CA, USA) for its high-end LINAC systems.…”

Section: Introductionmentioning

confidence: 99%

Development and Longitudinal Analysis of Plan-Based Streamlined Quality Assurance on Multiple Positioning Guidance Systems With Single Phantom Setup

Zhou

et al. 2021

Front. Oncol.

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PurposeThis study was to propose and validate an efficient and streamlined quality assurance (QA) method with a single phantom setup to check performances of patient positioning guidance systems including six-degree-of-freedom (6DoF) couch, X-ray modalities (kV–kV, MV–MV and CBCT), optical surface imaging system (AlignRT), lasers and optical distance indicator (ODI).Methods and MaterialsThe QA method was based on a pseudo-patient treatment plan using the AlignRT cube phantom. The cube was first randomly set up on the couch, and the initial position offsets were acquired by AlignRT and CBCT. The cube was restored to its reference position by 6DoF couch shift, during which the couch motion accuracy and tracking performances of AlignRT and CBCT were derived. After that, the residual offsets were acquired by kV–kV, MV–MV and AlignRT to derive the isocenter discrepancies. Finally, the laser alignment and ODI values were visually inspected. The QA procedure had been internally approved as a standard weekly QA test, and the results over 50 weeks were longitudinally analyzed for clinical validation.ResultsThe 6DoF couch motion errors as well as the tracking errors of AlignRT were sub-millimeter and sub-degree, and no deviation over 1 mm or 1 deg was identified. The ROI mode of isocenter (ISO) in AlignRT exhibited more consistent results than the centroid (CEN). While the isocenter discrepancy between CBCT and kV–kV was negligible, the maximal discrepancies between CBCT and MV–MV were 0.4 mm in LNG and 0.3 deg in PITCH. The isocenter discrepancies between CBCT and AlignRT were <0.5 mm in translation and <0.3 deg in rotation. For AlignRT, the isocenter discrepancies between the DICOM and SGRT references were about 0.6 mm in VRT, 0.5 mm in LNG and 0.2 deg in PITCH. As the therapists became familiar with the workflow, the average time to complete the whole procedure was around 23 min.ConclusionsThe streamlined QA exhibits desirable practicality as an efficient multipurpose performance check on positioning guidance systems. The stability, tracking performance and isocenter congruence of the positioning guidance systems have been fully validated for all clinical image guidance RT application, even SRS/SBRT, which requires the strictest tolerance.

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Detection of rotational errors in single‐isocenter multiple‐target radiosurgery: Is a routine off‐axis Winston–Lutz test necessary?

Pudsey

Biasi

Ralston

et al. 2022

J Applied Clin Med Phys

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Purpose: Recently the use of linear accelerator (linac)-based stereotactic radiosurgery (SRS) has increased, including single-isocenter multiple-target SRS. The workload of medical physicists has grown as a result and so has the necessity of maximizing the efficiency of quality assurance (QA). This study aimed to determine if measurement-based patient-specific QA with a highspatial-resolution dosimeter is sensitive to rotational errors, potentially reducing the need for routine off -axis Winston-Lutz (WL) testing. Methods: The impact of rotational errors along gantry, couch, and collimator axes on dose coverage of the gross tumor volume (GTV) and planning target volume (PTV) was determined with a 1-mm GTV/PTV expansion margin. Two techniques, the off -axis WL test using the StereoPHAN MultiMet-WL Cube (Sun Nuclear Corporation, Melbourne, Florida, USA) and patient-specific QA using the SRS MapCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA), were assessed on their ability to detect introduced errors before target coverage was compromised. These findings were also considered in the context of routine machine QA of rotational axis calibrations. Results: Rotational errors significantly impacted PTV dose coverage,especially in the couch angle. GTV dose coverage remained unaffected except for with large couch angle errors (≥1.5 • ).The off -axis WL test was shown to be sensitive to rotational errors with results consistently exceeding tolerance levels when or before coverage fell below departmentally accepted limits. Although patientspecific QA using the SRS MapCHECK was previously validated for SRS, this study showed inconsistency in detection of rotational errors. Conclusions: It is recommended that off -axis WL testing be conducted regularly to supplement routine monthly machine QA, as it is sensitive to errors that patient-specific QA may not detect. This frequency should be determined by individual departments, with consideration of GTV-PTV margins used, limitations on target off -axis distances, and routine mechanical QA results for particular linacs.

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An integrated quality assurance phantom for frameless single-isocenter multitarget stereotactic radiosurgery

Cited by 17 publications

References 42 publications

The development and testing of a novel spherical radiotherapy phantom system for the commissioning and patient‐specific quality assurance of mono‐isocentric multiple mets SRS plans

The development and testing of a novel spherical radiotherapy phantom system for the commissioning and patient‐specific quality assurance of mono‐isocentric multiple mets SRS plans

Development and Longitudinal Analysis of Plan-Based Streamlined Quality Assurance on Multiple Positioning Guidance Systems With Single Phantom Setup

Detection of rotational errors in single‐isocenter multiple‐target radiosurgery: Is a routine off‐axis Winston–Lutz test necessary?

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