Evaluation of semiempirical VMAT dose reconstruction on a patient dataset based on biplanar diode array measurements

Stambaugh, Cassandra; Opp, Daniel; Wasserman, Stuart; Zhang, Geoffrey; Feygelman, Vladimir

doi:10.1120/jacmp.v15i2.4705

Cited by 8 publications

(8 citation statements)

References 30 publications

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“…These studies suggest the importance of not only evaluating dose verification in 3D over a clinically relevant anatomic field but also of predicting dose distributions on the basis of QA results, (23,24) or measurement‐guided dose reconstruction (MGDR) (25) . The measured data are usually derived from 2D or 3D detector arrays and include EPID dosimetry (26) . A few studies have used measured fluence data (27,28) and required dose calculation engines, such as pencil beam convolution algorithms, to reconstruct the 3D dose distributions.…”

Section: Introductionmentioning

confidence: 99%

Intensity‐modulated radiation therapy dose verification using fluence and portal imaging device

Sumida

Yamaguchi

Das

et al. 2016

J Applied Clin Med Phys

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Patient‐specific quality assurance for intensity‐modulated radiation therapy (IMRT) dose verification is essential. The aim of this study is to provide a new method based on the relative error distribution by comparing the fluence map from the treatment planning system (TPS) and the incident fluence deconvolved from the electronic portal imaging device (EPID) images. This method is validated for 10 head and neck IMRT cases. The fluence map of each beam was exported from the TPS and EPID images of the treatment beams were acquired. Measured EPID images were deconvolved to the incident fluence with proper corrections. The relative error distribution between the TPS fluence map and the incident fluence from the EPID was created. This was also created for a 2D diode array detector. The absolute point dose was measured with an ionization chamber, and the dose distribution was measured by a radiochromic film. In three cases, MLC leaf positions were intentionally changed to create the dose error as much as 5% against the planned dose and our fluence‐based method was tested using gamma index. Absolute errors between the predicted dose of 2D diode detector and of our method and measurements were 1.26%±0.65% and 0.78%±0.81% respectively. The gamma passing rate (3% global / 3 mm) of the TPS was higher than that of the 2D diode detector (p<0.02), and lower than that of the EPID (p<0.04). The gamma passing rate (2% global / 2 mm) of the TPS was higher than that of the 2D diode detector, while the gamma passing rate of the TPS was lower than that of EPID (p<0.02). For three modified plans, the predicted dose errors against the measured dose were 1.10%, 2.14%, and −0.87%. The predicted dose distributions from the EPID were well matched to the measurements. Our fluence‐based method provides very accurate dosimetry for IMRT patients. The method is simple and can be adapted to any clinic for complex cases.PACS numbers: 87.55.D‐, 87.55.km, 87.55.Qr, 87.57.uq

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Section: Introductionmentioning

confidence: 99%

Intensity‐modulated radiation therapy dose verification using fluence and portal imaging device

Sumida

Yamaguchi

Das

et al. 2016

J Applied Clin Med Phys

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“…CT image sets were not required for the 3DVH calculation, and a relative 3D dose grid for each subbeam was independently calculated by convolving a 3D impulse TERMA function throughout the phantom volume with the 3D scatter depth kernels in 3DVH (10) . Thus, the presence of heterogeneity would introduce errors.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of patient DVH‐based QA metrics for prostate VMAT: correlation between accuracy of estimated 3D patient dose and magnitude of MLC misalignment

Saito

Ogasawara

Fujita

et al. 2015

J Applied Clin Med Phys

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The purpose of this study was to evaluate the accuracy of commercially available software, using patient DVH‐based QA metrics, by investigating the correlation between estimated 3D patient dose and magnitude of MLC misalignments. We tested 3DVH software with an ArcCHECK. Two different calculating modes of ArcCHECK Planned Dose Perturbation (ACPDP) were used: “Normal Sensitivity” and “High Sensitivity”. Ten prostate cancer patients treated with hypofractionated VMAT (67.6 Gy/26 Fr) in our hospital were studied. For the baseline plan, we induced MLC errors (−0.75,−0.5,−0.25,0.25,0.5, and 0.75 mm for each single bank). We calculated the dose differences between the ACPDP dose with error and TPS dose with error using gamma passing rates and using DVH‐based QA metrics. The correlations between dose estimation error and MLC position error varied with each structure and metric. A comparison using 1normal%/1 mm gamma index showed that the larger was the MLC error‐induced, the worse were the gamma passing rates. Slopes of linear fit to dose estimation error versus MLC position error for mean dose and D95 to the PTV were 1.76 and 1.40normal% mm−1, respectively, for “Normal Sensitivity”, and −0.53 and 0.88normal% mm−1, respectively, for “High Sensitivity”, showing better accuracy for “High Sensitivity” than “Normal Sensitivity”. On the other hand, the slopes for mean dose to the rectum and bladder, V35 to the rectum and bladder and V55 to the rectum and bladder, were −1.00,−0.55,−2.56,−1.25,−3.53, and 1.85normal% mm−1, respectively, for “Normal Sensitivity”, and −2.89,−2.39,−4.54,−3.12,−6.24, and −4.11normal% mm−1, respectively, for “High Sensitivity”, showing significant better accuracy for “Normal Sensitivity” than “High Sensitivity”. Our results showed that 3DVH had some residual error for both sensitivities. Furthermore, we found that “Normal Sensitivity” might have better accuracy for the DVH metric for the PTV and that “High Sensitivity” might have better accuracy for DVH metrics for the rectum and bladder. We must be willing to tolerate this residual error in clinical care.PACS number: 87.55Qr

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“…Wang et al [4] looked at detecting MLC positioning errors by inspecting ratios of the signal measured on the individual detectors of ArcCHECK. Stambaugh et al [5] examined measured 3D dose distributions in selected clinical plans.…”

Section: Introductionmentioning

confidence: 99%

“…Examples of the gamma passing rates in clinical scenarios have been published e.g. by Létourneau et al 2009 [15] and Stambaugh et al [5], with the passing rates being reported for selected gamma acceptance criteria. García-Vicente et al [16] studied the influence of the error in gantry rotation and leaf-positioning on the passing rates and on the DVH in selected sites (prostate and head & neck IMRT).…”

Section: Introductionmentioning

confidence: 99%

Gamma-Index Passing Rates in Baseline Plans Measured with a Detector Array

Szpala¹,

Kohli²

2015

IJMPCERO

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Purpose: This study provides a simple protocol for validation of the gamma passing rates and to identify the optimum values of % dose and mm criteria for dose distributions measured with a detector array. Methods: We chose ArcCHECK detector array to illustrate the concepts. We used plans with uniform or quasi-uniform dose distributions along the detector array for testing in the presence of dose errors. For testing sensitivity to spatial shift we employed a plan with approximately constant dose gradient along the axis of the instrument. Results: We identified a representative set of parameters which describe performance of a detector array. We determined the minimum gamma-index acceptance criteria allowing the passing rates to reach 100% in the absence of errors, and identified the minimum fully detectable errors for such criteria. For our baseline plans delivered to ArcCHECK, 100% passing rates were obtained for 1.5% dose criterion together with ±3% minimum error detectable at 100% rate, and for 1.5 mm criterion together with the minimum fully detectable error of ±3 mm. We inspected the impact of selected program options on the passing rates. Conclusions: The protocol we developed provides a simple method of commissioning-style analysis of a detector array without a need for analysis of a large number of clinical plans.

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Evaluation of semiempirical VMAT dose reconstruction on a patient dataset based on biplanar diode array measurements

Cited by 8 publications

References 30 publications

Intensity‐modulated radiation therapy dose verification using fluence and portal imaging device

Intensity‐modulated radiation therapy dose verification using fluence and portal imaging device

Evaluation of patient DVH‐based QA metrics for prostate VMAT: correlation between accuracy of estimated 3D patient dose and magnitude of MLC misalignment

Gamma-Index Passing Rates in Baseline Plans Measured with a Detector Array

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