Pre-treatment verification of lung SBRT VMAT plans with delivery errors: Toward a better understanding of the gamma index analysis

Alharthi, Thahabah; Pogson, Elise M; Arumugam, Sankar; Holloway, Lois; Thwaites, David

doi:10.1016/j.ejmp.2018.04.005

Cited by 20 publications

(27 citation statements)

References 41 publications

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“…The γ analysis has been used throughout IMRT dose verification. The commonly recommended γ analysis standards are 3.0mm, 3.0%, and 10% threshold [11,12], but studies have shown that, depending on the technology and the disease, we should adopt stricter standards or other supplement analysis to analyze errors [13,14]. This article was to investigate errors among planned dose caused by DCGS with dose distribution calculated by DCGS=2.0mm as RDS and the dose distribution calculated by DCGS=3.0mm, 4.0mm, 5.0mm as MDS, respectively.…”

Section: Dvh-γstandard and Passing Ratementioning

confidence: 99%

Study on the effect of DCGS on planned dose with 3DVH-γ analysis and bio-mathematical model for cervical cancer

Bai¹,

Zhu²,

Wu³

et al. 2020

Preprint

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Objective: The 3DVH-γ analysis and bio-mathematical model were used to analyze the effect of the dose calculation grid size (DCGS) on the planned dose (PD) for cervical cancer to explore the efficacy and sensitivity of the two methods in detecting dose changes.Methods：17 patients’ plans for cervical cancer were enrolled（Pinnacle TPS，VMAT）, and the DCGS was changed from 2.0mm to 5.0mm to calculate the planned dose respectively. The dose distribution calculated by DCGS = 2.0mm as the “ reference ” data set (RDS) , the dose distribution calculated by the rest DCGS as the“measurement”data set (MDS), the 3DVH-γ passing rates and the (N)TCPs of the all structures under different DCGS were abtained , and then analyze the influences of DCGS on the γ passing rate and (N)TCPs and the relationship between their changes.Results: The effect of DCGS on planned dose was obvious. When the γ-standard was 1.0mm, 1.0% and 10.0%, the difference of the results of the DCGS on dose effect could be detected by 3DVH-γ analysis (ps<0.05). With the decline of the standard, 3DVH-γ analysis’ ability to detect this difference was also declining. When the standard was 1.0mm, 3.0% and 10.0%, the p value of >0.05 accounted for the majority. With DCGS=2.0mm being RDS, ∆γ-passing-rate presented the same trend with ∆(N)TCPs of all structures except for the femurs only when the 1.0mm, 1.0% and 10.0% standards were adopted for the 3DVH-γ analysis.Conclusions: The 3DVH-γ analysis and bio-mathematical model can be used to analyze the effect of DCGS on the planned dose, and the former’s detection ability has a lot to do with the designed standard, and the latter’s capability is related to the parameters and calculated accuracy of the latter.

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Section: Dvh-γstandard and Passing Ratementioning

confidence: 99%

Study on the effect of DCGS on planned dose with 3DVH-γ analysis and bio-mathematical model for cervical cancer

Bai¹,

Zhu²,

Wu³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…The gamma analysis has been used throughout IMRT dose veri cation. The commonly recommended gamma analysis standards are 3.0mm, 3.0% [14,15], but studies have shown that, depending on the technology and the disease, we should adopt stricter standards or other supplement analysis to analyze errors [26,27].…”

Section: D Gamma Standard and Passing Ratementioning

confidence: 99%

Study on the ability of 3D gamma analysis and bio-mathematical model in detecting dose changes caused by dose-calculation-grid-size (DCGS)

Bai¹,

Zhu²,

Wu³

et al. 2020

Preprint

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Objective: To explore the efficacy and sensitivity of 3D gamma analysis and bio-mathematical model for cervical cancer in detecting dose changes caused by dose-calculation-grid-size (DCGS).Methods：17 patients’ plans for cervical cancer were enrolled (Pinnacle TPS，VMAT), and the DCGS was changed from 2.0mm to 5.0mm to calculate the planned dose respectively. The dose distribution calculated by DCGS = 2.0mm as the “reference” data set (RDS), the dose distribution calculated by the rest DCGS as the“measurement”data set (MDS), the 3D gamma passing rates and the (N)TCPs of the all structures under different DCGS were obtained, and then analyze the ability of 3D gamma analysis and (N)TCP model in detecting dose changes and what factors affect this ability.Results: The effect of DCGS on planned dose was obvious. When the gamma standard was 1.0mm, 1.0% and 10.0%, the difference of the results of the DCGS on dose-effect could be detected by 3D gamma analysis (all p value < 0.05). With the decline of the standard, 3D gamma analysis’ ability to detect this difference shows weaker. When the standard was 1.0mm, 3.0% and 10.0%, the p value of > 0.05 accounted for the majority. With DCGS=2.0mm being RDS, ∆gamma-passing-rate presented the same trend with ∆(N)TCPs of all structures except for the femurs only when the 1.0mm, 1.0% and 10.0% standards were adopted for the 3D gamma analysis.Conclusions: The 3D gamma analysis and bio-mathematical model can be used to analyze the effect of DCGS on the planned dose. For comparison, the former’s detection ability has a lot to do with the designed standard, and the latter’s capability is related to the parameters and calculated accuracy instrinsically.

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“…1,2 The only types of dosimeters currently capable of measuring full-3D dose distributions are polymer gel dosimeters and radiochromic detectors. [7][8][9][10][11][12][13][14][15] Although initially developed for patient setup verification, Electronic Portal Imaging Devices (EPIDs) also have useful dosimetric characteristics as summarized in review articles. Commercially available detector arrays, such as Arc-CHECK (Sun Nuclear Corp., Melbourne, FL), Octavius 4D (PTW, Freiburg, Germany), and Delta4 (Scandidos AB, Upsala, Sweden), compare measured to planned 3D dose distributions.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have already investigated the dosimetric characteristics and performance of these devices. [7][8][9][10][11][12][13][14][15] Although initially developed for patient setup verification, Electronic Portal Imaging Devices (EPIDs) also have useful dosimetric characteristics as summarized in review articles. 16,17 Some EPID-based approaches already allow for patient specific QA by reconstructing 3D dose distributions within the patient or phantom anatomy.…”

Section: Introductionmentioning

confidence: 99%

Transit and non‐transit 3D EPID dosimetry versus detector arrays for patient specific QA

Olaciregui-Ruiz

Vivas-Maiques

Kaas

et al. 2019

J Applied Clin Med Phys

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Purpose Despite their availability and simplicity of use, Electronic Portal Imaging Devices (EPIDs) have not yet replaced detector arrays for patient specific QA in 3D. The purpose of this study is to perform a large scale dosimetric evaluation of transit and non‐transit EPID dosimetry against absolute dose measurements in 3D. Methods After evaluating basic dosimetric characteristics of the EPID and two detector arrays (Octavius 1500 and Octavius 1000SRS), 3D dose distributions for 68 VMAT arcs, and 10 IMRT plans were reconstructed within the same phantom geometry using transit EPID dosimetry, non‐transit EPID dosimetry, and the Octavius 4D system. The reconstructed 3D dose distributions were directly compared by γ‐analysis (2L2 = 2% local/2 mm and 3G2 = 3% global/2 mm, 50% isodose) and by the percentage difference in median dose to the high dose volume (%∆HDVD50). Results Regarding dose rate dependency, dose linearity, and field size dependence, the agreement between EPID dosimetry and the two detector arrays was found to be within 1.0%. In the 2L2 γ‐comparison with Octavius 4D dose distributions, the average γ‐pass rate value was 92.2 ± 5.2%(1SD) and 94.1 ± 4.3%(1SD) for transit and non‐transit EPID dosimetry, respectively. 3G2 γ‐pass rate values were higher than 95% in 150/156 cases. %∆HDVD50 values were within 2% in 134/156 cases and within 3% in 155/156 cases. With regard to the clinical classification of alerts, 97.5% of the treatments were equally classified by EPID dosimetry and Octavius 4D. Conclusion Transit and non‐transit EPID dosimetry are equivalent in dosimetric terms to conventional detector arrays for patient specific QA. Non‐transit 3D EPID dosimetry can be readily used for pre‐treatment patient specific QA of IMRT and VMAT, eliminating the need of phantom positioning.

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Pre-treatment verification of lung SBRT VMAT plans with delivery errors: Toward a better understanding of the gamma index analysis

Cited by 20 publications

References 41 publications

Study on the effect of DCGS on planned dose with 3DVH-γ analysis and bio-mathematical model for cervical cancer

Study on the effect of DCGS on planned dose with 3DVH-γ analysis and bio-mathematical model for cervical cancer

Study on the ability of 3D gamma analysis and bio-mathematical model in detecting dose changes caused by dose-calculation-grid-size (DCGS)

Transit and non‐transit 3D EPID dosimetry versus detector arrays for patient specific QA

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