Comparison of detector performance in small 6 MV and 6 MV FFF beams using a Versa HD accelerator

Denia, P. Monasor; Garcia, M.; García, Carla Manjón; Higueras, J.D. Quiros; Blancas, N. De Marco; Alandí, Jorge Bonaque; Senabre, X.J. Juan; Serra, A. Santos; López-Tarjuelo, Juan

doi:10.1371/journal.pone.0213253

Cited by 11 publications

(5 citation statements)

References 37 publications

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“…This study found that ion chambers overestimated the measured penumbra, while EDGE and EBT3 accurately estimated penumbra. These results are in agreement with the data obtained from other published studies [28,[33][34][35][36][37]. The enlarged penumbra observed with ionization chambers was due to a higher range of secondary electrons being present in air than in water and the volume averaging effect.…”

Section: Discussionsupporting

confidence: 92%

Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors

Dwivedi

Kansal

Dangwal

et al. 2021

Biomed. Phys. Eng. Express

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The present study aimed to dosimetrically evaluate the small-fields of a 6 MV flattening filter-free (FFF) photon beam using different detectors.The 6 MV FFF photon beam was used for measurement of output factor, depth dose, and beam profile of small-fields of sizes 0.6 cm × 0.6 cm to 6.0 cm × 6.0 cm. The five detectors used were SNC125c, PinPoint, EDGE, EBT3, and TLD-100. All measurements were performed as per the International Atomic Energy Agency TRS 483 protocol. Output factors measured using different detectors as direct reading ratios showed significant variation for the smallest fields, whereas after correcting them according to TRS 483, all sets of output factors were nearly compatible with each other when measurement uncertainty was also considered. The beam profile measured using SNC125c showed the largest penumbra for all field sizes, whereas the smallest was recorded with EDGE. Compared with that of EBT3, the surface dose was found to be much higher for all the other detectors. PinPoint, EBT3, TLD-100, and EDGE were found to be the detector of choice for small-field output factor measurements; however, PinPoint needs special attention when used for the smallest field size (0.6 cm × 0.6 cm). EDGE and EBT3 are optimal for measuring beam profiles. EBT3, PinPoint, and EDGE can be selected for depth dose measurements, and EBT3 is suitable for surface dose estimation.

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Section: Discussionsupporting

confidence: 92%

Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors

Dwivedi

Kansal

Dangwal

et al. 2021

Biomed. Phys. Eng. Express

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“…in 2019 contains OFs for microDiamond measured in a 6 MV beam under equivalent conditions to our measurements, with OFs of 0.518 for the 0.6 cm × 0.6 cm field and 0.794 for 1 cm × 1 cm field. [ 22 ] Our measurements are in agreement with these values. As per TRS-483, the Razor ionization chamber requires larger field output correction factors due to volume averaging as the detector is large relative to field size.…”

Section: Discussionsupporting

confidence: 90%

Comparison and validation of multiple detectors against monte carlo simulation for the use of small-field dosimetry

et al. 2022

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Aim: The aim of this study was to compare the Exradin W2 scintillator, PTW microDiamond, IBA Razor Nano, and IBA Razor chamber detectors for small-field dose measurements and validate the measured data against the EGSnrc user code and observe the variation between daisy-chained and direct measurement methods for the above detectors. Materials and Methods: The W2 scintillator, microDiamond, Razor Nano, and Razor chamber detectors were used to measure the in-plane and cross-plane profiles and the output factors (OFs) at 10 cm depth, and 90 source-to-surface distance for 6MV X-rays (Elekta Versa HD). The field sizes ranged from 0.5 cm × 0.5 cm to 5 cm × 5 cm. The BEAMnrc/DOSXYZnrc user codes (EGSnrc) were used to simulate the reference profiles. Gamma analysis was performed to compare the measured and simulated dose distributions. Results: The OFs measured with the W2 scintillator, microDiamond, Razor Nano chamber, Razor chamber, and the calculated Monte Carlo (MC) showed agreement to within 1% for the 3 cm × 3 cm field size. The uncertainty in the MC simulation was observed to be 0.4%. The percent difference in OFs measured using daisy-chained and direct measurement methods was within 0.15%, 0.4%, 1.4%, and 2.4% for microDiamond, W2 scintillator, Nano, and Razor chamber detectors, respectively. Conclusion: The lateral beam profiles and OFs of W2 scintillator, microDiamond, Razor Nano, and Razor chambers exhibit good agreement with the MC simulation within the nominal field sizes. Our results demonstrate that we can achieve considerable time-saving by directly measuring small-field OFs without daisy-chained methods using microDiamond and W2 scintillator. In terms of ease of use, sensitivity, reproducibility, and from a practical standpoint, we recommend microDiamond for small-field dosimetry.

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“…Lechner et al generated stereotactic 3Dconformal plans for brain metastases, as well as VMAT plans for head and neck and prostate cancer patients, and looked at the dosimetric effects of output factor inaccuracies [39]. Monasor Denia et al compared the detector performance in a Versa HD accelerator [40]. Mamballikalam et al evaluated the dosimetric efficacy of VMAT compared to dynamic conformal arc therapy and 3D conformal radiotherapy for very small (<1 cm 3 ) and small (<3 cm 3 ) volume tumours [41].…”

Section: Discussionmentioning

confidence: 99%

Effect of inaccurate small field output factors on brain SRS plans

Dobberthien¹,

Cao²,

Zhao³

et al. 2022

Biomed. Phys. Eng. Express

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External beam radiotherapy often includes the use of field sizes 3 × 3 cm2 or less, which can be defined as small fields. Dosimetry is a difficult, yet important part of the radiotherapy process. The dosimetry of small fields has additional challenges, which can lead to treatment inconsistencies if not done properly. Most important is the use of an appropriate detector, as well as the application of the necessary corrections. The International Atomic Energy Agency and the American Association of Physicists in Medicine provide the International Code of Practice (CoP) TRS-483 for the dosimetry of small static fields used in external MV photon beams. It gives guidelines on how to apply small-field correction factors for small field dosimetry. The purpose of this study was to evaluate the impact of inaccurate small-field output factors on clinical brain stereotactic radiosurgery plans with and without applying the small-field correction factors as suggested in the CoP. Small-field correction factors for a Varian TrueBeam linear accelerator were applied to uncorrected relative dose factors. Uncorrected and corrected clinical plans were created with two different beam configurations, 6 MV with a flattening filter (6 WFF) and 6 MV without a flattening filter (6 FFF). For the corrected plans, the planning target volume mean dose was 1.6 ± 0.9% lower with p < 0.001 for 6 WFF and 1.8 ± 1.5% lower with p < 0.001 for 6 FFF. For brainstem, a major organ at risk, the corrected plans had a dose that was 1.6 ± 0.9% lower with p = 0.03 for 6 WFF and 1.8 ± 1.5% lower with p = 0.10 for 6 FFF. This represents a systematic error that should and can be corrected.

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Comparison of detector performance in small 6 MV and 6 MV FFF beams using a Versa HD accelerator

Cited by 11 publications

References 37 publications

Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors

Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors

Comparison and validation of multiple detectors against monte carlo simulation for the use of small-field dosimetry

Effect of inaccurate small field output factors on brain SRS plans

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