Testing of a sag of a dosimetry system rotating with a gantry using the interplay effect between detector motion and MLC motion

• Autorzy: Morawska-Kaczyńska M. , Dąbrowski R. , Drozdyk I. , Kukołowicz P.

Identyfikatory

DOI

10.1515/pjmpe-2017-0005

• Języki publikacji: EN

Abstrakty

EN

Purpose: An interplay between detector motion and MLC motion is a source of measurement error, when dose for dynamic arc is measured using a dosimetry system moving relative to the beam central axis during its rotation with a gantry. The purpose of this study is to develop and to evaluate a method of quantitative testing of a sag/flex of such dosimetry systems. Methods: The method is based on evaluation of relative differences between signals measured for two single arc beams, where a narrow slit field is sliding during gantry movement in opposite directions. The component of a measurement error related to the interplay effect was first assessed based on theoretical computer simulations and then on measurements for four dosimetry systems. The sag pattern of EPID and 2D array was extracted from the measurement results. Results: The simulations showed a 4 mm difference in field width and 3.3% difference in relative signals at beam axis between test beams where the slit field swept over 19 cm in opposite directions ( sinusoidal sag pattern with amplitude of 1 mm was assumed). The signal differences exceeding 4% and 5% were measured for EPID and 2D array, respectively. Conclusions: Even relatively small detector sag (less than 1 mm) can produce significant measurement error; therefore, the detector sag test should be an obligatory component of a validation of rotating dosimetry systems used for QA of dynamic arcs.

Słowa kluczowe

EN

QA; IMAT; dosimetry; interplay

• Wydawca: Polskie Towarzystwo Fizyki Medycznej ; De Gruyter
• Czasopismo: Polish Journal of Medical Physics and Engineering
• Rocznik: 2017
• Tom: Vol. 23, Iss. 2
• Strony: 21--28
• Opis fizyczny: Bibliogr. 14 poz., rys., tab.

Twórcy

autor

Morawska-Kaczyńska M.

• Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, ul. Wawelska 15, 02-034 Warsaw, Poland

autor

Dąbrowski R.

• Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, ul. Wawelska 15, 02-034 Warsaw, Poland

autor

Drozdyk I.

• Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, ul. Wawelska 15, 02-034 Warsaw, Poland

autor

Kukołowicz P.

• Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, ul. Wawelska 15, 02-034 Warsaw, Poland

Bibliografia

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