Physical dosimetry of volumetric modulated arc therapy (VMAT) using EPID and 2D array for quality assurance

Mohamed, Ismail E.; Ibrahim, Ayman G.; Zidan, H. M.; El-Bahkiry, Hesham S.; El-sahragti, Adel Y.

doi:10.1016/j.ejrnm.2018.02.003

Cited by 3 publications

(4 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Currently, there are many types of dosimeters for radiotherapy, including the ionisation chamber, films, the thermoluminescent dosimeter (TLD), and the array dosimeter [ 16 , 21 , 22 , 23 ]. The ionisation chamber is a gas-filled ionisation chamber, which comprises an electrode surrounded by a conductive wall that collects the charges generated from radiation interaction in the gas [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

et al. 2022

View full text Add to dashboard Cite

Recent advances in radiotherapy technology and techniques have allowed a highly conformal radiation to be delivered to the tumour target inside the body for cancer treatment. A three-dimensional (3D) dosimetry system is required to verify the accuracy of the complex treatment delivery. A 3D dosimeter based on the radiochromic response of a polymer towards ionising radiation has been introduced as the PRESAGE dosimeter. The polyurethane dosimeter matrix is combined with a leuco-dye and a free radical initiator, whose colour changes in proportion to the radiation dose. In the previous decade, PRESAGE gained improvement and enhancement as a 3D dosimeter. Notably, PRESAGE overcomes the limitations of its predecessors, the Fricke gel and the polymer gel dosimeters, which are challenging to fabricate and read out, sensitive to oxygen, and sensitive to diffusion. This article aims to review the characteristics of the radiochromic dosimeter and its clinical applications. The formulation of PRESAGE shows a delicate balance between the number of radical initiators, metal compounds, and catalysts to achieve stability, optimal sensitivity, and water equivalency. The applications of PRESAGE in advanced radiotherapy treatment verifications are also discussed.

show abstract

Section: Introductionmentioning

confidence: 99%

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

et al. 2022

View full text Add to dashboard Cite

show abstract

“…22,[30][31][32][33][34][35] In recent years, the use of the electronic portal imaging device (EPID) for pre-treatment patient-specific treatment plan verification has gained increased interest due to its simplicity. 22,23,[26][27][28][29][35][36][37][38][39] The Varian EPID has been shown to be capable of producing high-resolution measured dose digital images which can be compared with predicted portal dose images calculated by the Eclipse TM Treatment Planning System (TPS) based on the actual fluence distribution for every patient treatment plan fields. 22,23,[28][29][30]36,40,41 Various methods including the dose difference (DD), distance-to-agreement (DTA) and the gamma (γ) index have been used to compare the measured and predicted dose images.…”

Section: Introductionmentioning

confidence: 99%

“…22,23,[28][29][30]36,40,41 Various methods including the dose difference (DD), distance-to-agreement (DTA) and the gamma (γ) index have been used to compare the measured and predicted dose images. [22][23][24][26][27][28][29][30][35][36][37][38][39][42][43][44] The DD is the difference in dose at a specified point in each of the predicted and measured dose distributions, and it is reflected as a percentage of the maximum dose, whereas the DTA represents the nearest distance between two points of equal dose on the predicted and measured dose images when superimposed. 22,23,30,42,43,45 According to Low et al 42 and Low & Dempsey, 43 the DD method is very sensitive in areas of high-dose gradient and a small spatial misalignment will cause a large DD between the measured and the calculated dose distributions, whereas the DTA method is sensitive in areas of low-dose gradient and a small DD in low-dose area could result in large DTA values.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, it is a common practice to compare the predicted and measured dose distributions using the gamma (γ) index technique which takes both the DD and DTA into consideration. [22][23][24][26][27][28][29][30][35][36][37][38][39][42][43][44] This evaluation method indicates a satisfactory agreement between a specific dose point in the predicted and measured dose images when the dimensionless quantity γ is ≤1, otherwise the dose point is considered to fail. 22,24,30,42,43 The overall agreement of a set of predicted and measured dose distributions is characterised by the percentage of dose points that fulfil passing criteria, known as the gamma passing rate (%GP).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Retrospective analysis of portal dosimetry pre-treatment quality assurance of intracranial SRS/SRT VMAT treatment plans

2021

View full text Add to dashboard Cite

Background: The complexity associated with the treatment planning and delivery of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) volumetric modulated arc therapy (VMAT) plans which employs continuous dynamic modulation of dose rate, field aperture and gantry speed necessitates diligent pre-treatment patient-specific quality assurance (QA). Numerous techniques for pre-treatment VMAT treatment plans QA are currently available with the aid of several different devices including the electronic portal imager (EPID). Although several studies have provided recommendations for gamma criteria for VMAT pre-treatment QA, there are no specifics for SRS/SRT VMAT QA. Thus, we conducted a study to evaluate intracranial SRS/SRT VMAT QA to determine clinical action levels for gamma criteria based on the institutional estimated means and standard deviations. Materials and methods: We conducted a retrospective analysis of 118 EPID patient-specific pre-treatment QA dosimetric measurements of 47 brain SRS/SRT VMAT treatment plans using the integrated Varian solution (RapidArcTM planning, EPID and Portal dosimetry system) for planning, delivery and EPID QA analysis. We evaluated the maximum gamma (γmax), average gamma (γave) and percentage gamma passing rate (%GP) for different distance-to-agreement/dose difference (DTA/DD) criteria and low-dose thresholds. Results: The gamma index analysis shows that for patient-specific SRS/SRT VMAT QA with the portal dosimetry, the mean %GP is ≥98% for 2–3 mm/1–3% and Field+0%, +5% and +10% low-dose thresholds. When applying stricter spatial criteria of 1 mm, the mean %GP is >90% for DD of 2–3% and ≥88% for DD of 1%. The mean γmax ranges: 1·32 ± 1·33–2·63 ± 2·35 for 3 mm/1–3%, 1·57 ± 1·36–2·87 ± 2·29 for 2 mm/1–3% and 2·36 ± 1·83–3·58 ± 2·23 for 1 mm/1–3%. Similarly the mean γave ranges: 0·16 ± 0·06–0·19 ± 0·07 for 3 mm/1–3%, 0·21 ± 0·08–0·27 ± 0·10 for 2 mm/1–3% and 0·34 ± 0·14–0·49 ± 0·17 for 1 mm/1–3%. The mean γmax and mean γave increase with increased DTA and increased DD for all low-dose thresholds. Conclusions: The establishment of gamma criteria local action levels for SRS/SRT VMAT pre-treatment QA based on institutional resources is imperative as a useful tool for standardising the evaluation of EPID-based patient-specific SRS/SRT VMAT QA. Our data suggest that for intracranial SRS/SRT VMAT QA measured with the EPID, a stricter gamma criterion of 1 mm/2% or 1 mm/3% with ≥90% %GP could be used while still maintaining an in-control QA process with no extra burden on resources and time constraints.

show abstract

Comparison of gamma analysis with using different dosimetric systems for pre-treatment verification of intensity-modulated radiation therapy

Inan

Gül

2021

Can. J. Phys.

View full text Add to dashboard Cite

Purpose: The evaluation of the agreement between calculated and measured dose plays an essential role in the quality assurance (QA) procedures of intensity-modulated radiation therapy (IMRT). This study aimed to compare gamma analysis using Portal Dosimetry (PD), Epiqa, and 2D array detector for dose verification of radiotherapy treatment plans. Materials and Methods: Five fields step-and-shoot IMRT plan was used to performed for 20 prostate IMRT patients using the dual-energy DHX linear accelerator (Varian Medical System, Palo Alto, CA, USA). The treatment plans were created using Varian DHX Eclipse treatment planning system (TPS) version 15.1. All measurements were performed by aS500 EPID integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (1%/1 mm, 2%/2 mm 3%/2 mm and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann Whitney Test and Kruskal-Wallis Test, and p-value of p <0.01 was considered to be significant. Results: The average pass rate for 20 IMRT plans was above 95% for all devices with 2%/2 mm, 3%/2 mm and 3%/3 mm. The mean and standard deviation passing rates (γ ≤1) were found to be 99.80±0.19, 99.35±0.34 and 97.53±0.71 for PD, Epiqa and 2D array respectively. All IMRT plans passed 2%/2 mm, 3%/2 mm and 3%/3 mm gamma by more than 95% of three dosimetric systems. They are all in good agreement with the literature. Conclusion: All three devices are acceptable for quality control of IMRT. Due to the simplicity and fast evaluation process, PD can be preferred for quality control.

show abstract

Physical dosimetry of volumetric modulated arc therapy (VMAT) using EPID and 2D array for quality assurance

Cited by 3 publications

References 15 publications

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

Retrospective analysis of portal dosimetry pre-treatment quality assurance of intracranial SRS/SRT VMAT treatment plans

Comparison of gamma analysis with using different dosimetric systems for pre-treatment verification of intensity-modulated radiation therapy

Contact Info

Product

Resources

About