Dose‐response curve of EBT, EBT2, and EBT3 radiochromic films to synchrotron‐produced monochromatic x‐ray beams

Brown, Thomas A. D.; Hogstrom, Kenneth R.; Alvarez, Diane; Matthews, K.; Ham, Kyungmin; Dugas, Joseph P.

doi:10.1118/1.4767770

Cited by 122 publications

(101 citation statements)

References 18 publications

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“…Brown et al 31 reported small energy dependence in low-energy monoenergetic photon beams (25-35 keV), whereas by contrast, Villarreal-Barajas and Khan 32 reported under-response of Figure 4. Set-up for the measurement of profiles and inspection of field sizes.…”

Section: Relative Dosimetry: Depth Dosesmentioning

confidence: 94%

Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit

Aspradakis¹,

Zucchetti²

2015

BJR

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Objective: The objective of this work was to characterize the performance of the WOmed T-200-kilovoltage (kV) therapy machine. Methods: Mechanical functionality, radiation leakage, alignment and interlocks were investigated. Half-value layers (HVLs) (first and second HVLs) from X-ray beams generated from tube potentials between 30 and 200 kV were measured. Reference dose was determined in water. Beam start-up characteristics, dose linearity and reproducibility, beam flatness, and uniformity as well as deviations from inverse square law were assessed. Relative depth doses (RDDs) were determined in water and water-equivalent plastic. The quality assurance program included a dosimetry audit with thermoluminescent dosemeters. Results: All checks on machine performance were satisfactory. HVLs ranged between 0.45-4.52 mmAl and 0.69-1.78 mmCu. Dose rates varied between 0.2 and 3 Gy min 21 with negligible time-end errors. There were differences in measured RDDs from published data. Beam outputs were confirmed with the dosimetry audit. The use of published backscatter factors was implemented to account for changes in phantom scatter for treatments with irregularly shaped fields. Conclusion: Guidance on the determination of HVL and RDD in kV beams can be contradictory. RDDs were determined through measurement and curve fitting. These differed from published RDD data, and the differences observed were larger in the low-kV energy range. Advances in knowledge: This article reports on the comprehensive and novel approach to the acceptance, commissioning and clinical use of a modern kV therapy machine. The challenges in the dosimetry of kV beams faced by the medical physicist in the clinic are highlighted.

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Section: Relative Dosimetry: Depth Dosesmentioning

confidence: 94%

Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit

Aspradakis¹,

Zucchetti²

2015

BJR

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“…found an underresponse of relative sensitivity (defined as netOD xxkV /netOD 4MV ) ranging from 0.97 to 0.99 for monochromatic x rays of 25, 30, and 35 kV at varying dose levels (50–200 cGy) in a PMMA phantom 21. Masillon et al.…”

Section: Discussionmentioning

confidence: 99%

Investigation of a source model for a new electronic brachytherapy tandem by film measurement

Martin

Sowards

Wang

2018

J Applied Clin Med Phys

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PurposeTo investigate the accuracy of a vendor‐supplied source model for a new Xoft Axxent 0‐degree titanium tandem by film measurement.MethodsWe measured the anisotropy factors at varying distances and angles from the tandem in water using radiochromic film (Gafchromic EBT3) and an Epson Perfection v750 desktop flatbed scanner (US Epson, Long Beach, CA). A 0‐degree tandem was placed vertically in a water phantom. Four pieces of film, each at varying depths, were positioned orthogonal to the longitudinal axis of the tandem for azimuthal anisotropy measurements. Polar anisotropy measurements were taken with the film aligned parallel to the tandem. An absolute dose calibration for the film was verified with a PTW 34013 Soft X‐Ray Chamber. The film measurements were analyzed using different color channels. The measured polar anisotropy for varying source positions was compared to the vendor's data. Azimuthal anisotropy was measured as a function of the radius and angle, and normalized to the mean value over all angles at the specified radius.ResultsThe azimuthal anisotropy of the tandem and source was found to be consistent for different positions along the tandem's longitudinal axis and at varying distances from the tandem. Absolute dose using a calibrated parallel plate chamber showed agreement to within 2% of expected TPS values. The custom tandem, which has a thicker tip than the wall, was attenuating the 50 kV photons more than expected, at the angles where the photons had more wall material to traverse. This discrepancy was verified at different distances from the tandem and with different measurement techniques. As distance increased, anisotropy values had better agreement.ConclusionsWe quantified the agreement between the measured and provided anisotropy factors for a new Xoft Axxent 0‐degree titanium tandem. Radiochromic film response at low kV energy was also investigated. Our results showed that vendor‐supplied TG‐43 values were appropriate for clinical use at majority of the angles. A rigorous quality assurance method for new electronic brachytherapy sources and applicators, along with complete knowledge of all dosimetric measuring tools, should be implemented for all parts of the verification and commissioning process.

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“…Wynikać to może z różnej serii zastosowanych filmów, skanera, jak i sposobu obróbki danych, zatem oparto się o rezultaty badań przeprowadzonych w tych samych warunkach. Według pracy Brown i Hongstrom [22] dla dawek do 3 Gy zdeponowanych przy użyciu promieniowania o energii 25keV -4MV film EBT wykazuje znaczną czułość na energię promieniowania, podczas gdy Chiu-Tsao [23] dla energii 21 keV -6 MV w zakresie dawek do 3 Gy wykazał, że odpowiedź filmów EBT jest niemalże niezależna od energii promieniowania, pogarszając się w zakresie bardzo niskich energii. Do podobnych wniosków dla zakresu energii 50 kVp -6 MV doszedł Butson [24].…”

Section: Kalibracja Filmów Dozymetrycznychunclassified

Zastosowanie filmów radiochromowych w weryfikacji rozkładów dawek w brachyterapii. Przygotowanie do wprowadzenia algorytmów zaproponowanych przez TG-186 AAPM.

Bielęda

2017

los

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StreszczenieWeryfikacja rozkładów dawki w brachyterapii stawia przed fizykami medycznymi wiele wyzwań. Ze względu na wysoki gradient dawki pomiary wymagają bardzo dużej higieny pracy oraz wysokiej dokładności. Do tej pory stosowane były algorytmy do obliczenia rozkładów dawek zaimplementowane w systemach planowania leczenia wprowadzone przez TG-43 AAPM (ang. Task Group 43 of American Association of Physicists in Medicine -Grupa Zadaniowa Amerykańskiego Towarzystwa Fizyki Medycznej). Charakteryzują się one przede wszystkim tym, że przyrównują współczynniki osłabienia promieniowania ośrodka, w którym rozchodzi się promieniowanie do współczynnika osłabienia promieniowania wody. Taka sama procedura jest zastosowana dla ośrodka, w którym obliczana jest dawka pochłonięta. Wprowadzenie przez grupę TG-186 AAPM nowych algorytmów obliczających rozkłady dawek, uwzględniających rzeczywiste współczynniki osłabienia i pochłaniania promieniowania wymagają bardziej szczegółowych i dokładnych procedur kontroli jakości przygotowanych planów leczenia w brachyterapii. W niniejszej pracy omówiono najnowsze doniesienia dotyczące weryfikacji rozkładów dawek w brachyterapii z uwzględnieniem doniesień przedstawionych w trakcie konferencji naukowej 3rd ESTRO Forum, która odbyła się w 2015 roku w Barcelonie. AbstractVerification of brachytherapy dose distributions is a challenging task for medical physicists. Due to a very steep dose gradient, measurements require a very high hygiene and accuracy. Until now, the algorithms introduced by the task group TG-43 of AAPM (American Association of Physicists in Medicine have been used to calculate the dose distributions implemented in the treatment planning systems). These algorithm Adres do korespondencji

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Dose‐response curve of EBT, EBT2, and EBT3 radiochromic films to synchrotron‐produced monochromatic x‐ray beams

Cited by 122 publications

References 18 publications

Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit

Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit

Investigation of a source model for a new electronic brachytherapy tandem by film measurement

Zastosowanie filmów radiochromowych w weryfikacji rozkładów dawek w brachyterapii. Przygotowanie do wprowadzenia algorytmów zaproponowanych przez TG-186 AAPM.

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