Analysis of dose comparison techniques for patient‐specific quality assurance in radiation therapy

Yu, Liting; Tang, Timothy L. S.; Cassim, Naasiha; Livingstone, A. G.; Cassidy, Darren; Kairn, Tanya; Crowe, Scott

doi:10.1002/acm2.12726

Cited by 13 publications

(4 citation statements)

References 31 publications

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“…As the criteria are not as stringent, this difference decreases, 9.4% (LDT of 5%) and 7.3% (LDT of 10%) for the 5%/3 mm criteria. The differences found in the behavior of the local and global gamma index shown in this study coincide with the reports by Yu L. et al and Stasi M. et al [14,15], which report that the two forms of normalization exhibit specific and sensitive variations to dose administration errors.…”

Section: Resultssupporting

confidence: 91%

Evaluation of the impact of parameters on the gamma index for breast cancer treatments

Garcia

Solis

Salazar³

et al. 2021

Rev. Mex. Fís.

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Volumetric modulated arc radiotherapy treatments (VMAT) can achieve highly conformed dose distributions, however, due to the complexity of the technique, there may have differences between the planned and administered dose distributions, generated by the precision in the dose calculation of the treatment planning system (TPS) or by the errors associated with it. One way to quantify the difference between both dose distributions is by using the gamma index; however, there is no accord regarding the parameters that should be used in its analysis. On the other hand, this gamma index may depend on the pathology and the area to be treated. For this reason, the present work aims to evaluate different parameters of the analysis of the gamma index for breast cancer treatments, these are local and global normalization, the analysis criteria (1%/1 mm, 2%/2 mm, 3%/2 mm, 2%/3 mm, 3%/3 mm and 5%/3 mm) and the low dose threshold (LDT) of 5% and 10%. For this, 30 treatment plans performed with VMAT technique in a 6 MV Infinity linear accelerator (Elekta, Stockholm, Sweden) were analyzed, calculated with the TPS Monaco V.5.11.03 (Elekta, Stockholm, Sweden) and measured with the Octavius 4D system (PTW, Freiburg, Germany). The results of the analysis of the global gamma index were of a gamma passing rate (%GP) greater than 95% for analysis criteria of 3%/3 mm and 5%/3 mm, however, for these same parameters in the local gamma index analysis the results are 85.8% and 91.1% respectively. In addition, from the LDT evaluation, it is observed that there is a mean increase of %GP for the local gamma index analysis and a mean decrease of %GP for the global gamma index analysis, for the LDT from 5% to 10%. On the other hand, the standard deviation is lower in the global gamma index analysis than in the local one, and it decreases when the analysis criteria are less strict. It is concluded that there is not a great difference in choosing the LDT of 5% or 10%. When the gamma analysis criteria are less strict, the %GP increases both for the analysis of the local and global gamma index, taking this into account, each parameter should be used carefully according to the treatment plan to be analyzed, taking into account the advantages and disadvantages of each parameter.

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Section: Resultssupporting

confidence: 91%

Evaluation of the impact of parameters on the gamma index for breast cancer treatments

Garcia

Solis

Salazar³

et al. 2021

Rev. Mex. Fís.

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“…( 15 ) and Yu et al. ( 6 , 16 ) have proposed the divide and conquer (D&C) gamma method. In this method, the dose distribution is divided into distinct regions: i) a high-dose (HD) region within the 90% isodose, ii) a high-gradient (HG) region with doses ranging from 50% to 90% isodose, iii) a medium-dose (MD) region with doses ranging from 20% to 50% isodose, and iv) a low-dose (LD) region with doses ranging from 10% to 20% isodose.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the Region for Evaluation of Global Gamma Analysis for Nasopharyngeal Cancer (NPC) Pretreatment IMRT QA by COMPASS: A Retrospective Study

Liu

Huang

et al. 2022

Front. Oncol.

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BackgroundThe global gamma passing rate is the most commonly used metric for patient-specific pretreatment quality assurance in radiation therapy. However, the optimal region for evaluation and specific action limits (ALs) need to be explored. Therefore, this study was carried out to explore the optimal region for evaluation of the global gamma passing rate and define ALs by using the COMPASS software.MethodsA total of 93 intensity-modulated radiation therapy (IMRT) plans for nasopharyngeal cancer (NPC) patients, including 61 original plans and 32 multileaf collimator (MLC) error-introduced test plans, were selected for retrospective analysis. Firstly, the dose distribution was divided into six isodose regions (“≥10%”, “≥20%”, “≥30%”, “≥40%”, “≥50%”, and “≥60%”) based on the prescribed dose and one clinically oriented region for evaluation (“whole”) to perform the three-dimensional (3D) global gamma reanalysis. Meanwhile, the percentage gamma passing rate (%GP), mean gamma index (μGI) based on 3%/2 mm criteria, and percentage dose error (%DE) of the dose–volume histogram (DVH) metrics were recorded by COMPASS application. Secondly, the Pearson’s correlation coefficient was used to analyze the correlation between %GP and %DE and between μGI and %DE in different regions. Additionally, receiver operating characteristic (ROC) methodology was applied to quantify the fraction of patient-specific plans evaluated as “fail” and “pass”. In order to improve the correlation between gamma analysis result and clinical criteria, ROC analysis was carried out in accordance with hybridization analysis criteria (%DE ≤3%, %GP ≥90% and %DE ≤3%, μGI ≤0.6). ROC was performed for two purposes: 1) to analyze the sensitivity and specificity of %GP and μGI in different regions for evaluation and 2) to define the ALs of %GP and μGI in the optimal region for evaluation. Finally, the plans introduced with MLC errors were prepared for validation. Moreover, we also compared the positive rate of ALs of both %GP and μGI in detecting MLC error-introduced plans in different regions.Results1) In our study, a number of DVH-based metrics were found to be correlated with the evaluation parameters. The corresponding number was 4, 2, 1, 1, 1, 1, and 3 in γwhole, γ10%, γ20%, γ30%, γ40%, γ50%, and γ60%, respectively, and 5, 3, 0, 1, 1, 4, and 2 in μGIwhole, μGI10%, μGI20%, μGI30%, μGI40%, μGI50%, and μGI60%, respectively. The results by COMPASS have revealed that the %DE of specific structures has a slightly higher correlation with both %GP and μGI of the “whole” region compared with that of any other region. However, it is a moderate correlation (0.5 ≤ |r| < 0.8). 2) The areas under the curves (AUCs) of γwhole, μGIwhole, μGI40%, μGI50%, and μGI60% were >0.7 based on 3%/2 mm criteria. According to the Youden coefficient, we defined the ALs of γwhole ≥92%, μGIwhole ≤0.36, μGI40% ≤0.43, and μGI60% ≤0.40 based on 3%/2 mm criteria. 3) In the validation, for original plans, the accuracy of ALγwhole, ALγ10%, ALμGIwhole, ALμGI40%, ALμGI50%, and ALμGI60% was 23%, 9.8%, 90%, 80.3%, 9.8%, and 88.5%, respectively. For test plans with systematic MLC errors smaller than 0.8 mm, the positive rates of ALγwhole, ALγ10%, ALμGIwhole, ALμGI40%, ALμGI50%, and ALμGI60% were 25%, 58%, 92%, 92%, 42%, and 100%, respectively. For the plans with systematic MLC errors higher than 0.8 mm, the positive rates of all AL%GP and ALμGI were 100%. From the COMPASS validation results, the accuracy of γwhole, μGIwhole, μGI40%, and μGI60% was higher than that of the conventional γ10% and commonly used μGI50%.ConclusionsCompared with the traditional evaluation region (i.e., the criteria with a threshold of 10% or a threshold of 50%, it was the same with the isodose regions of “≥10%”, “≥50%” based on the prescribed dose in our study), the “whole” region is more meaningful to the clinic by COMPASS. The accuracy of μGIwhole is higher than that of the conventional γ10% and the commonly used μGI50%.

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“…This is achieved by a simultaneous dynamical modulation of the multileaf collimator (MLC), gantry rotation speed, and dose rate 4–6 . The use of such an elaborate dose distribution with steep and sharp gradients requires patient‐specific quality assurance (PSQA) in order to carefully verify the dose before treatment delivery 7,8 and ensure the accuracy and safety of the treatment process 9,10 It is therefore strongly recommended that PSQA is performed routinely 11,12 for VMAT treatment plans, in order to detect any potential error due for example to inaccurate calculation of the dose distribution by the treatment planning system (TPS) or failure of record‐and‐verify system, as well as to inaccurate MLC movements 13,14 . Typically, QA protocols compare the dose distribution planned by the TPS with the dose delivered to a homogeneous water‐equivalent phantom that contains detectors 10,15 .…”

Section: Introductionmentioning

confidence: 99%

“…the dose before treatment delivery 7,8 and ensure the accuracy and safety of the treatment process 9,10 It is therefore strongly recommended that PSQA is performed routinely 11,12 for VMAT treatment plans, in order to detect any potential error due for example to inaccurate calculation of the dose distribution by the treatment planning system (TPS) or failure of record-and-verify system, as well as to inaccurate MLC movements. 13,14 Typically, QA protocols compare the dose distribution planned by the TPS with the dose delivered to a homogeneous water-equivalent phantom that contains detectors.…”

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confidence: 99%

Validation of a secondary dose check tool against Monte Carlo and analytical clinical dose calculation algorithms in VMAT

Piffer

Casati

Marrazzo

et al. 2021

J Applied Clin Med Phys

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Purpose: Patient-specific quality assurance (QA) is very important in radiotherapy, especially for patients with highly conformed treatment plans like VMAT plans. Traditional QA protocols for these plans are time-consuming reducing considerably the time available for patient treatments. In this work, a new MC-based secondary dose check software (SciMoCa) is evaluated and benchmarked against well-established TPS (Monaco and Pinnacle 3) by means of treatment plans and dose measurements. Methods: Fifty VMAT plans have been computed using same calculation parameters with SciMoCa and the two primary TPSs. Plans were validated with measurements performed with a 3D diode detector (ArcCHECK) by translating patient plans to phantom geometry. Calculation accuracy was assessed by measuring point dose differences and gamma passing rates (GPR) from a 3D gamma analysis with 3%-2 mm criteria. Comparison between SciMoCa and primary TPS calculations was made using the same estimators and using both patient and phantom geometry plans. Results: TPS and SciMoCa calculations were found to be in very good agreement with validation measurements with average point dose differences of 0.7 AE 1.7% and −0.2 AE 1.6% for SciMoCa and two TPSs, respectively. Comparison between SciMoCa calculations and the two primary TPS plans did not show any statistically significant difference with average point dose differences compatible with zero within error for both patient and phantom geometry plans and GPR (98.0 AE 3.0% and 99.0 AE 3.0% respectively) well in excess of the typical 95%clinical tolerance threshold. Conclusion: This work presents results obtained with a significantly larger sample than other similar analyses and, to the authors' knowledge, compares SciMoCa with a MC-based TPS for the first time. Results show that a MC-based secondary patient-specific QA is a clinically viable, reliable, and promising technique, that potentially allows significant time saving that can be used for patient treatment and a per-plan basis QA that effectively complements traditional commissioning and calibration protocols.

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Analysis of dose comparison techniques for patient‐specific quality assurance in radiation therapy

Cited by 13 publications

References 31 publications

Evaluation of the impact of parameters on the gamma index for breast cancer treatments

Evaluation of the impact of parameters on the gamma index for breast cancer treatments

Optimizing the Region for Evaluation of Global Gamma Analysis for Nasopharyngeal Cancer (NPC) Pretreatment IMRT QA by COMPASS: A Retrospective Study

Validation of a secondary dose check tool against Monte Carlo and analytical clinical dose calculation algorithms in VMAT

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