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Photon beam attenuation characteristics of three commercial radiation therapy treatment couch-tops

Published online by Cambridge University Press:  26 June 2018

Hamza Wajid ,
Andre Fleck ,
Johnson Darko  and
Ernest Osei
Hamza Wajid
Affiliation:
Department of Medical Physics, Grand River Regional Cancer Centre, Kitchener, ON, Canada Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada
Andre Fleck
Affiliation:
Department of Medical Physics, Grand River Regional Cancer Centre, Kitchener, ON, Canada Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Canada
Johnson Darko
Affiliation:
Department of Medical Physics, Grand River Regional Cancer Centre, Kitchener, ON, Canada Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Canada
Ernest Osei
Affiliation:
Department of Medical Physics, Grand River Regional Cancer Centre, Kitchener, ON, Canada Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Canada Department of Systems Design, University of Waterloo, Waterloo, ON, Canada
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Abstract

Aim

The purpose of the study was to investigate the detailed angularly dependent attenuation characteristics of three different commercial couch-tops: Varian IGRT, Qfix kVue Standard and Qfix kVue Dose Max couch-tops used in radiation therapy.

Materials and methods

The attenuation of photon beams by the treatment couch-tops was measured using a farmer chamber inserted at the centre of a 16 cm diameter cylindrical acrylic phantom for five different photon energies: 6 MV, 6FFF MV, 10 MV, 10FFF MV and 15 MV photon beams. The Varian IGRT couch-top has three different thicknesses thus attenuation measurements were done at the three different longitudinal locations. Measurements were made with the sliding support rails of the Qfix kVue Standard and Qfix kVue Dose Max couch-tops at both ‘rails-in’ and ‘rails-out’ positions. All measurements were taken for several projections through 360° movement of the gantry and for two different field sizes; 5×5 cm2 and 10×10 cm2.

Results and findings

The results indicate that the maximum attenuation of the Varian IGRT couch-top at the thin, medium and thick portions are 5·1, 5·7 and 8·9%, respectively, the Qfix kVue Standard couch with the rails-in and rails-out are 11·2 and 13·7%, respectively, and Qfix kVue Dose Max couch-top with rails-in and rails-out are 9·7 and 13·8%, respectively. The results from this study can be used to account for the couch-top attenuation during radiation treatment planning of patients treated with these couch-tops.

Keywords

photon beam attenuationvarian IGRT couch-topqfix kVue couch toptreatment couch toptreatment planning
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 17 , Issue 4 , December 2018 , pp. 377 - 383
Copyright
© Cambridge University Press 2018 

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