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Relative profile measurements in 1.5T MR-linacs: investigation of central axis deviations.
Episkopakis, Anastasios; Margaroni, Vasiliki; Karaiskos, Pantelis; Koutsouveli, Efi; Marinos, Nikolas; Pappas, Eleftherios P.
Afiliación
  • Episkopakis A; Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece.
  • Margaroni V; Global Clinical Operations, Elekta Ltd, Fleming Way, RH10 99RR Crawley, West Sussex, United Kingdom.
  • Karaiskos P; Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece.
  • Koutsouveli E; Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece.
  • Marinos N; Medical Physics Department, Hygeia Hospital, Kifisias Avenue and 4 Erythrou Stavrou, Marousi, 151 23 Athens, Greece.
  • Pappas EP; Global Clinical Operations, Elekta Ltd, Fleming Way, RH10 99RR Crawley, West Sussex, United Kingdom.
Phys Med Biol ; 69(17)2024 Aug 27.
Article en En | MEDLINE | ID: mdl-39137816
ABSTRACT
Objective. In 1.5 T MR-linacs, the absorbed dose central axis (CAX) deviates from the beam's CAX due to inherent profile asymmetry. In addition, a measured CAX deviation may be biased due to potential lateral (to the beam) effective point of measurement (EPOML) shifts of the detector employed. By investigating CAX deviations, the scope of this study is to determine a set ofEPOMLshifts for profile measurements in 1.5 T MR-linacs.Approach. The Semiflex 3D ion chamber and microDiamond detector (PTW, Germany) were considered in the experimental study while three more detectors were included in the Monte Carlo (MC) study. CAX deviations in the crossline and inline profiles were calculated based on inflection points of the 10×10 cm2field, at five centers. In MC simulations, the experimental setup was reproduced. A small water voxel was simulated to calculate CAX deviation without the impact of the detector-specificEPOMLshift.Main results. All measurements were consistent among the five centers. MC-based and experimental measurements were in agreement within uncertainties. Placing the microDiamond in the vertical orientation does not appear to affect the detector'sEPOML, which is on its central longitudinal axis. For the Semiflex 3D in the crossline direction, the CAX deviation was 2.3 mm, i.e. 1 mm larger than the ones measured using the microDiamond and simulated considering the ideal water detector. Thus, anEPOMLshift of 1 mm is recommended for crossline profile measurements under both Semiflex 3D orientations. For the inline profile, anEPOMLshift of -0.5 mm was determined only for the parallel configuration. In the MC study, CAX deviations were found detector- and orientation-dependent. The dead volume is responsible for theEPOMLshift only in the inline profile and under the parallel orientation.Significance. This work contributes to data availability on the correction or mitigation of the magnetic field-induced changes in the detectors' response.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Aceleradores de Partículas / Imagen por Resonancia Magnética / Método de Montecarlo Idioma: En Revista: Phys Med Biol Año: 2024 Tipo del documento: Article País de afiliación: Grecia Pais de publicación: Reino Unido
Texto completo
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Aceleradores de Partículas / Imagen por Resonancia Magnética / Método de Montecarlo Idioma: En Revista: Phys Med Biol Año: 2024 Tipo del documento: Article País de afiliación: Grecia Pais de publicación: Reino Unido