A Portal imager-based patient dosimetry system

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dc.contributor.author Roberts, James M. D.
dc.date.accessioned 2013-06-25T22:30:15Z
dc.date.available 2013-06-25T22:30:15Z
dc.date.copyright 2013 en_US
dc.date.issued 2013-06-25
dc.identifier.uri http://hdl.handle.net/1828/4660
dc.description.abstract A technique for the in vivo dose verification of intensity modulated radiation therapy (IMRT) has been developed. An electronic portal image, calibrated in terms of absolute dose, is acquired for each radiation field following transmission through the patient at the time of treatment. For an IMRT field, the portal image signal is back-projected through a model of the patient in order to calculate the dose at the isocentric plane perpendicular to the beam central axis. The IMRT in vivo dose verification technique was adapted for volumetric modu- lated arc therapy (VMAT) treatments when a single dosimetric image is acquired over an arc. The patient dose along axis of gantry rotation can be directly related to the signal along the vertical axis of EPIs in integrated mode. In this novel VMAT in vivo dosimetry technique, the portal image signal is back-projected through a rotationally averaged model of the patient to calculate a 1D in vivo dose along the axis of gantry rotation. A research ethics board clinical study was approved and transmission portal images were acquired at regular intervals from human subjects. Portal image-derived isocenter point doses were in good agreement with treatment planning system (TPS) calculations for IMRT (mean difference δ=0.0%, standard deviation of the differences σ=4.3%) and VMAT (δ=1.1%, σ=1.7%). The one-dimensional (VMAT) and two-dimensional (IMRT) reconstructed doses were further analyzed by calculating mean dose differences and γ−evaluation pass-rates, which were also shown to be in good agreement with TPS calculations. The portal image-based in vivo dosimetry techniques were shown to be clinically feasible, with reconstruction times on the order of minutes for the first fraction and less than one minute for each fraction thereafter. en_US
dc.language English eng
dc.language.iso en en_US
dc.subject dosimetry en_US
dc.subject EPID en_US
dc.subject portal imaging en_US
dc.subject radiation therapy en_US
dc.subject VMAT en_US
dc.subject IMRT en_US
dc.subject medical physics en_US
dc.subject in vivo dosimetry en_US
dc.title A Portal imager-based patient dosimetry system en_US
dc.type Thesis en_US
dc.contributor.supervisor Ansbacher, William
dc.contributor.supervisor Jirasek, Andrew
dc.degree.department Dept. of Physics and Astronomy en_US
dc.degree.level Master of Science M.Sc. en_US
dc.rights.temp Available to the World Wide Web en_US
dc.description.scholarlevel Graduate en_US
dc.description.proquestcode 0760 en_US
dc.description.proquestcode 0574 en_US
dc.description.proquestcode 0760 en_US

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