Articles producció científica> Ciències Mèdiques Bàsiques

Dosimetric leaf gap and leaf trailing effect in a double-stacked multileaf collimator

  • Datos identificativos

    Identificador: imarina:9334293
    Autores:
    Hernandez, VSaez, JAngerud, ACayez, RKhamphan, CNguyen, DVieillevigne, LFeygelman, V
    Resumen:
    Purpose To investigate (i) the dosimetric leaf gap (DLG) and the effect of the "trailing distance" between leaves from different multileaf collimator (MLC) layers in Halcyon systems and (ii) the ability of the currently available treatment planning systems (TPSs) to approximate this effect.Methods DICOM plans with transmission beams and sweeping gap tests were created in Python for measuring the DLG for each MLC layer independently and for both layers combined. In clinical Halcyon plans both MLC layers are interchangeably used and leaves from different layers are offset, thus forming a trailing pattern. To characterize the impact of such configuration, new tests called "trailing sweeping gaps" were designed and created where the leaves from one layer follow the leaves from the other layer at a fixed "trailing distance" t between the tips. Measurements were carried out on five Halcyons SX2 from different institutions and calculations from both the Eclipse and RayStation TPSs were compared with measurements.Results The dose accumulated during a sweeping gap delivery progressively increased with the trailing distance t. We call this "the trailing effect." It is most pronounced for t between 0 and 5 mm, although some changes were obtained up to 20 mm. The dose variation was independent of the gap size. The measured DLG values also increased with t up to 20 mm, again with the steepest variation between 0 and 5 mm. Measured DLG values were negative at t = 0 (the leaves from both layers at the same position) but changed sign for t >= 1 mm, in line with the positive DLG sign usually observed with single-layer rounded-end MLCs. The Eclipse TPS does not explicitly model the leaf tip and, as a consequence, could not predict the dose reduction due to the trailing effect. This resul
  • Otros:

    Autor según el artículo: Hernandez, V; Saez, J; Angerud, A; Cayez, R; Khamphan, C; Nguyen, D; Vieillevigne, L; Feygelman, V
    Departamento: Ciències Mèdiques Bàsiques
    Autor/es de la URV: Hernandez Masgrau, Victor
    Palabras clave: Transmission Trailing effect System Stacked mlc Radiotherapy, intensity-modulated Radiotherapy planning, computer-assisted Radiotherapy dosage Radiometry Plant leaves Mlc model Halcyon Dosimetric leaf gap
    Resumen: Purpose To investigate (i) the dosimetric leaf gap (DLG) and the effect of the "trailing distance" between leaves from different multileaf collimator (MLC) layers in Halcyon systems and (ii) the ability of the currently available treatment planning systems (TPSs) to approximate this effect.Methods DICOM plans with transmission beams and sweeping gap tests were created in Python for measuring the DLG for each MLC layer independently and for both layers combined. In clinical Halcyon plans both MLC layers are interchangeably used and leaves from different layers are offset, thus forming a trailing pattern. To characterize the impact of such configuration, new tests called "trailing sweeping gaps" were designed and created where the leaves from one layer follow the leaves from the other layer at a fixed "trailing distance" t between the tips. Measurements were carried out on five Halcyons SX2 from different institutions and calculations from both the Eclipse and RayStation TPSs were compared with measurements.Results The dose accumulated during a sweeping gap delivery progressively increased with the trailing distance t. We call this "the trailing effect." It is most pronounced for t between 0 and 5 mm, although some changes were obtained up to 20 mm. The dose variation was independent of the gap size. The measured DLG values also increased with t up to 20 mm, again with the steepest variation between 0 and 5 mm. Measured DLG values were negative at t = 0 (the leaves from both layers at the same position) but changed sign for t >= 1 mm, in line with the positive DLG sign usually observed with single-layer rounded-end MLCs. The Eclipse TPS does not explicitly model the leaf tip and, as a consequence, could not predict the dose reduction due to the trailing effect. This resulted in dose discrepancies up to +10% and -8% for the 5 mm sweeping gap and up to +/- 5% for the 10 mm one depending on the distance t. RayStation implements a simple model of the leaf tip that was able to approximate the trailing effect and improved the agreement with measured doses. In particular, with a prototype version of RayStation that assigned a higher transmission at the leaf tip the agreement with measured doses was within +/- 3% even for the 5 mm gap. The five Halcyon systems behaved very similarly but differences in the DLG around 0.2 mm were found across different treatment units and between MLC layers from the same system. The DLG for the proximal layer was consistently higher than for the distal layer, with differences ranging between 0.10 mm and 0.24 mm.Conclusions The trailing distance between the leaves from different layers substantially affected the doses delivered by sweeping gaps and the measured DLG values. Stacked MLCs introduce a new level of complexity in TPSs, which ideally need to implement an explicit model of the leaf tip in order to reproduce the trailing effect. Dynamic tests called "trailing sweeping gaps" were designed that are useful for characterizing and commissioning dual-layer MLC systems.
    Áreas temáticas: Radiology, nuclear medicine and imaging Radiology, nuclear medicine & medical imaging Medicine (miscellaneous) Medicina ii Medicina i Interdisciplinar General medicine Engenharias iv Engenharias ii Ciências biológicas iii Ciências biológicas ii Ciências biológicas i Ciência da computação Biotecnología Biophysics Astronomia / física Antropologia / arqueologia
    Acceso a la licencia de uso: https://creativecommons.org/licenses/by/3.0/es/
    Direcció de correo del autor: victor.hernandez@urv.cat
    Identificador del autor: 0000-0003-3770-8486
    Fecha de alta del registro: 2024-07-27
    Versión del articulo depositado: info:eu-repo/semantics/acceptedVersion
    Enlace a la fuente original: https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/mp.14914
    URL Documento de licencia: https://repositori.urv.cat/ca/proteccio-de-dades/
    Referencia al articulo segun fuente origial: Medical Physics. 48 (7): 3413-3424
    Referencia de l'ítem segons les normes APA: Hernandez, V; Saez, J; Angerud, A; Cayez, R; Khamphan, C; Nguyen, D; Vieillevigne, L; Feygelman, V (2021). Dosimetric leaf gap and leaf trailing effect in a double-stacked multileaf collimator. Medical Physics, 48(7), 3413-3424. DOI: 10.1002/mp.14914
    DOI del artículo: 10.1002/mp.14914
    Entidad: Universitat Rovira i Virgili
    Año de publicación de la revista: 2021
    Tipo de publicación: Journal Publications
  • Palabras clave:

    Biophysics,Medicine (Miscellaneous),Radiology, Nuclear Medicine & Medical Imaging,Radiology, Nuclear Medicine and Imaging
    Transmission
    Trailing effect
    System
    Stacked mlc
    Radiotherapy, intensity-modulated
    Radiotherapy planning, computer-assisted
    Radiotherapy dosage
    Radiometry
    Plant leaves
    Mlc model
    Halcyon
    Dosimetric leaf gap
    Radiology, nuclear medicine and imaging
    Radiology, nuclear medicine & medical imaging
    Medicine (miscellaneous)
    Medicina ii
    Medicina i
    Interdisciplinar
    General medicine
    Engenharias iv
    Engenharias ii
    Ciências biológicas iii
    Ciências biológicas ii
    Ciências biológicas i
    Ciência da computação
    Biotecnología
    Biophysics
    Astronomia / física
    Antropologia / arqueologia
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