EPID sensitivity to delivery errors for pre-treatment verification of lung SBRT VMAT plans

Alharthi, Thahabah; Arumugam, Sankar; Vial, P; Holloway, Lois; Thwaites, David

doi:10.1016/j.ejmp.2019.02.007

Cited by 11 publications

(17 citation statements)

References 47 publications

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“…More reliable results could be produced by calculating a full 3D gamma distribution instead of 2D or 2.5D [19,48]. But even in datasets free of noise, gamma could accept points with larger mismatches than the nominal values of the criteria under some combinations of DD, DTA and acceptance passing rate limits [36,49,50].…”

Section: Discussionmentioning

confidence: 99%

Treatment plan verification: A review on the comparison of dose distributions

et al. 2019

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The aim of this review article is to provide a useful reference for dose comparison techniques within the frame of treatment plan verification. Each technique is presented with a general description given along with advantages and disadvantage and the rationale for its development. Methods: The review was conducted in PubMed from 1993 to 2019 including articles referring to the methodology of dose comparison for treatment plan verification. Results: The search identified thirty-one dose comparison methods that were categorized according to the number of physical parameters that take into account for dose comparison. Conclusions: Among the available methods for the comparison of two dose distributions, the γ-analysis (gamma analysis) has been widely adopted as the gold standard in verification procedures. However, due to various intrinsic limitations of gamma index, the development of a better metric taking into account both statistical and in clinical parameters is required.

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Section: Discussionmentioning

confidence: 99%

Treatment plan verification: A review on the comparison of dose distributions

et al. 2019

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“…All lung SBRT VMAT baseline (NE) plans and the plans with introduced variations were exported to the Elekta Synergy Linac using the Mosaiq system (Elekta, Crawley, UK) for delivery. All measurements were those previously performed to test overall system sensitivity (measured doses vs expected/planned (TPS) doses) 17,18 …”

Section: Methodsmentioning

confidence: 99%

“…The measured EPID images were converted into dose matrices using a calibration procedure and an existing methodology primarily developed by Lee et al, 24,25 and Matlab computer code outlined elsewhere 26 . (more details can be found in our previous EPID experimental study) 18 …”

Section: Methodsmentioning

confidence: 99%

“…This study was based on the data taken in our previous published work using an ArcCHECK detector 17 with a plan‐based approach (composite arcs/whole plan measurements) and using an EPID 18 with a field (arc)‐based approach. In each case these approaches were followed, as those common in clinical practice for these devices.…”

Section: Methodsmentioning

confidence: 99%

“…Specifically, for lung VMAT SBRT plans there have been only limited studies in the literature. Hence, in our previous work we evaluated the sensitivity of both the ArcCHECK detector, 17 and an EPID (Elekta iView GT), 18 to a range of introduced delivery errors, using a conventional approach to test overall system sensitivity. That is, we used the standard procedure used for clinical QA, that is, in each case we compared measured doses, with and without errors, to the predicted values from the baseline (no error, NE) treatment plan.…”

Section: Introductionmentioning

confidence: 99%

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Intrinsic detector sensitivity analysis as a tool to characterize ArcCHECK and EPID sensitivity to variations in delivery for lung SBRT VMAT plans

Alharthi

Vial

Holloway

et al. 2021

J Applied Clin Med Phys

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Purpose To investigate intrinsic sensitivity of an electronic portal imaging device (EPID) and the ArcCHECK detector and to use this in assessing their performance in detecting delivery variations for lung SBRT VMAT. The effect of detector spatial resolution and dose matrix interpolation on the gamma pass rate was also considered. Materials and methods Fifteen patients’ lung SBRT VMAT plans were used. Delivery variations (errors) were introduced by modifying collimator angles, multi‐leaf collimator (MLC) field sizes and MLC field shifts by ±5, ±2, and ±1 degrees or mm (investigating 103 plans in total). EPID and ArcCHECK measured signals with introduced variations were compared to measured signals without variations (baseline), using OmniPro‐I'mRT software and gamma criteria of 3%/3 mm, 2%/2 mm, 2%/1 mm, and 1%/1 mm, to test each system's basic performance. The measurement sampling resolution for each was also changed to 1 mm and results compared to those with the default detector system resolution. Results Intrinsic detector sensitivity analysis, that is, comparing measurement to baseline measurement, rather than measurement to plan, demonstrated the intrinsic constraints of each detector and indicated the limiting performance that users might expect. Changes in the gamma pass rates for ArcCHECK, for a given introduced error, were affected only by dose difference (DD %) criteria. However, the EPID showed only slight changes when changing DD%, but greater effects when changing distance‐to‐agreement criteria. This is pertinent for lung SBRT where the minimum dose to the target will drop dramatically with geometric errors. Detector resolution and dose matrix interpolation have an impact on the gamma results for these SBRT plans and can lead to false positives or negatives in error detection if not understood. Conclusion The intrinsic sensitivity approach may help in the selection of more meaningful gamma criteria and the choice of optimal QA device for site‐specific dose verification.

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A hybrid method to improve efficiency of patient specific SRS and SBRT QA using 3D secondary dose verification

Baltz

Manigold

Seier

et al. 2022

J Applied Clin Med Phys

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Purpose Patient Specific QA (PSQA) by direct phantom measurement for all intensity modulated radiation therapy (IMRT) cases is labor intensive and an inefficient use of the Medical Physicist's time. The purpose of this work was to develop a hybrid quality assurance (QA) technique utilizing 3D dose verification as a screening tool to determine if a measurement is necessary. Methods This study utilized Sun Nuclear DoseCHECK (DC), a 3D secondary verification software, and Fraction 0, a trajectory log IMRT QA software. Twenty‐two Lung stereotactic body radiation therapy (SBRT) and thirty single isocentre multi‐lesion SRS (MLSRS) plans were retrospectively analysed in DC. Agreement of DC and the TPS dose for selected dosimetric criteria was recorded. Calculated 95% confidence limits (CL) were used to establish action limits. All cases were delivered and measured using the Sun Nuclear stereotactic radiosurgery (SRS) MapCheck. Trajectory logs of the delivery were used to calculate Fraction 0 results for the same criteria calculated by DC. Correlation of DC and Fraction 0 results were calculated. Phantom measured QA was compared to Fraction 0 QA results for the cases which had DC criteria action limits exceeded. Results Correlation of DC and Fraction 0 results were excellent, demonstrating the same action limits could be used for both and DC can predict Fraction 0 results. Based on the calculated action limits, zero lung SBRT cases and six MLSRS cases were identified as requiring a measurement. All plans that passed the DC screening had a passing measurement based PSQA and agreed with Fraction 0 results. Conclusion Using 95% CL action limits of dosimetric criteria, a 3D secondary dose verification can be used to determine if a measurement is required for PSQA. This method is efficient for it is part of the normal clinical workflow when verifying any clinical treatment. In addition, it can drastically reduce the number of measurements needed for PSQA.

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EPID sensitivity to delivery errors for pre-treatment verification of lung SBRT VMAT plans

Cited by 11 publications

References 47 publications

Treatment plan verification: A review on the comparison of dose distributions

Treatment plan verification: A review on the comparison of dose distributions

Intrinsic detector sensitivity analysis as a tool to characterize ArcCHECK and EPID sensitivity to variations in delivery for lung SBRT VMAT plans

A hybrid method to improve efficiency of patient specific SRS and SBRT QA using 3D secondary dose verification

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