Implementation and evaluation of a transit dosimetry system for treatment verification

Ricketts, K; Navarro, C.; Lane, Katherine A.; Moran, Meena S.; Blowfield, Claire; Kaur, U.; Cotten, Gary; Tomala, Dee; Lord, Christine; Jones, Joanne; Adeyemi, Abiodun

doi:10.1016/j.ejmp.2016.04.010

Cited by 12 publications

(4 citation statements)

References 19 publications

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“…Clinical experience with EPIgray has been described for both Elekta 124,127 and Varian equipment. 126 In the study by Ricketts et al, 124 measured EPID dose maps of 58 patients were back projected using planning CT images to calculate dose at prespecified points within the patient and compared with TPS dose using point dose differences.…”

Section: Clinical Resultsmentioning

confidence: 99%

AAPM Task Group Report 307: Use of EPIDs for Patient‐Specific IMRT and VMAT QA

et al. 2023

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PurposeElectronic portal imaging devices (EPIDs) have been widely utilized for patient‐specific quality assurance (PSQA) and their use for transit dosimetry applications is emerging. Yet there are no specific guidelines on the potential uses, limitations, and correct utilization of EPIDs for these purposes. The American Association of Physicists in Medicine (AAPM) Task Group 307 (TG‐307) provides a comprehensive review of the physics, modeling, algorithms and clinical experience with EPID‐based pre‐treatment and transit dosimetry techniques. This review also includes the limitations and challenges in the clinical implementation of EPIDs, including recommendations for commissioning, calibration and validation, routine QA, tolerance levels for gamma analysis and risk‐based analysis.MethodsCharacteristics of the currently available EPID systems and EPID‐based PSQA techniques are reviewed. The details of the physics, modeling, and algorithms for both pre‐treatment and transit dosimetry methods are discussed, including clinical experience with different EPID dosimetry systems. Commissioning, calibration, and validation, tolerance levels and recommended tests, are reviewed, and analyzed. Risk‐based analysis for EPID dosimetry is also addressed.ResultsClinical experience, commissioning methods and tolerances for EPID‐based PSQA system are described for pre‐treatment and transit dosimetry applications. The sensitivity, specificity, and clinical results for EPID dosimetry techniques are presented as well as examples of patient‐related and machine‐related error detection by these dosimetry solutions. Limitations and challenges in clinical implementation of EPIDs for dosimetric purposes are discussed and acceptance and rejection criteria are outlined. Potential causes of and evaluations of pre‐treatment and transit dosimetry failures are discussed. Guidelines and recommendations developed in this report are based on the extensive published data on EPID QA along with the clinical experience of the TG‐307 members.ConclusionTG‐307 focused on the commercially available EPID‐based dosimetric tools and provides guidance for medical physicists in the clinical implementation of EPID‐based patient‐specific pre‐treatment and transit dosimetry QA solutions including intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatments.

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Section: Clinical Resultsmentioning

confidence: 99%

AAPM Task Group Report 307: Use of EPIDs for Patient‐Specific IMRT and VMAT QA

et al. 2023

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“…EPIgray uses the finite tissue maximum ratio fTMR, which is the ratio between two doses measured in a phantom at depth D max . One dose is measured under the presence of an absorber (here: solid water) with finite dimensions inside the beam path between the source and the detector, while the other is measured under the same conditions but without the absorber [ 16 ]. This formalism allows reconstructing the dose in the patient from the dose measured at EPID level in transit conditions.…”

Section: Methodsmentioning

confidence: 99%

Commissioning and Evaluation of an Electronic Portal Imaging Device-Based In-Vivo Dosimetry Software

Held

Cheung

Andujar

et al. 2018

Cureus

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This study reports on our experience with the in-vivo dose verification software, EPIgray® (DOSIsoft, Cachan, France). After the initial commissioning process, clinical experiments on phantom treatments were evaluated to assess the level of accuracy of the electronic portal imaging device (EPID) based in-vivo dose verification.EPIgray was commissioned based on the company’s instructions. This involved ion chamber measurements and portal imaging of solid water blocks of various thicknesses between 5 and 35 cm. Field sizes varied between 2 x 2 cm2 and 20 x 20 cm2. The determined conversion factors were adjusted through an additional iterative process using treatment planning system calculations. Subsequently, evaluation was performed using treatment plans of single and opposed beams, as well as intensity modulated radiotherapy (IMRT) plans, based on recommendations from the task group report TG-119 to test for dose reconstruction accuracy. All tests were performed using blocks of solid water slabs as a phantom.For single square fields, the dose at isocenter was reconstructed within 3% accuracy in EPIgray compared to the treatment planning system dose. Similarly, the relative deviation of the total dose was accurately reconstructed within 3% for all IMRT plans with points placed inside a high-dose region near the isocenter. Predictions became less accurate than < 5% when the evaluation point was outside the treatment target. Dose at points 5 cm or more away from the isocenter or within an avoidance structure was reconstructed less reliably.EPIgray formalism accuracy is adequate for an efficient error detection system with verifications performed in high-dose volumes. It provides immediate intra-fractional feedback on the delivery of treatment plans without affecting the treatment beam. Besides the EPID, no additional hardware is required. The software evaluates local point dose measurements to verify treatment plan delivery and patient positioning within 5% accuracy, depending on the placement of evaluation points.

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“…It is widely used in Europe but quite seldom in Malaysia. [8][9][10][11][12] Hence, this study aims to report on the initial performance of the first installed EPID-based software verification in Malaysia. Specifically, it will highlight its feasibility for treatment plan verification.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a commercial EPID-based in-vivo dosimetry and its feasibility and implementation for treatment verification in Malaysia

Radzi

Rahman

Rizan³

et al. 2022

Polish Journal of Medical Physics and Engineering

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Introduction: In vivo dosimetry verification is currently a necessity in radiotherapy centres in Europe countries as one of the tools for patient-specific QA, and now its demand is currently rising in developed countries, such as Malaysia. The aim of this study is to characterize commercial EPID-based dosimetry and its implementation for radiotherapy treatment verification in Malaysia. Materials and Methods: In this work, the sensitivity and performance of a commercially available in vivo dosimetry system, EPIgray® (DOSIsoft, Cachan, France), were qualitatively evaluated prior to its use at our centre. EPIgray response to dose linearity, field size, off-axis, position, and angle dependency tests were performed against TPS calculated dose for 6 MV and 10 MV photon beams. Relative deviations of the total dose were evaluated at isocentre and different depths in the water. EPIgray measured dose was validated by using IMRT and VMAT prostate plan. All calculation points were at the beam isocentre and at points suggested by TG-119 with accepted tolerance of ±10% dose threshold. Results: EPIgray reported good agreement for linearity, field size, off-axis, and position dependency with TPS dose, being within 5% tolerance for both energy ranges. The average deviation was less than ±2% and ±7% in 6 MV and 10 MV photon beams, respectively, for the angle dependency test. A clinical evaluation performed for the IMRT prostate plan gave average agreement within ±3% at the plan isocentre for both energies. While for the VMAT plan, 95% and 100% of all points created lie below ±5% for 6 MV and 10 MV photon beam energy, respectively. Conclusion: In summary, based on the results of preliminary characterization, EPID-based dosimetry is believed as an important tool and beneficial to be implemented for IMRT/VMAT plans verification in Malaysia, especially for in vivo verification, alongside existing pre-treatment verification.

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Implementation and evaluation of a transit dosimetry system for treatment verification

Cited by 12 publications

References 19 publications

AAPM Task Group Report 307: Use of EPIDs for Patient‐Specific IMRT and VMAT QA

AAPM Task Group Report 307: Use of EPIDs for Patient‐Specific IMRT and VMAT QA

Commissioning and Evaluation of an Electronic Portal Imaging Device-Based In-Vivo Dosimetry Software

Characterization of a commercial EPID-based in-vivo dosimetry and its feasibility and implementation for treatment verification in Malaysia

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