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Development of techniques for verification of advanced radiotherapy by portal dosimetry

Md Radzi, Yasmin 2018. Development of techniques for verification of advanced radiotherapy by portal dosimetry. PhD Thesis, Cardiff University.
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This research work is related to the development of an enhanced method for the treatment verification of Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). Such advanced treatment techniques require accurate verification procedures to ensure treatments are delivered as correctly as possible. This work focused on the use of the Varian aS1000 Electronic Portal Imaging Device (EPID) with Dosimetry Check software-based verification system. This EPID-based patient dose verification had been widely discussed and proposed as a way to achieve treatment delivery accuracy and patient safety, and as an ‘in vivo’ verification technique that helps to avoid or minimise dosimetric errors. In this work, a novel matrix-based software method to correct for backscatter effects from the Varian aS1000 EPID support arm has been developed. The methodology allows a reliable quantification of the backscatter effect to be applied directly to the Dosimetry Check calibration and verification system. This process includes the use of a clinical treatment planning system (Oncentra MasterPlan, Nucletron) to calculate predicted dose distribution within a phantom or patient, which may be compared to the dose reconstructed by Dosimetry Check. It has been demonstrated that the developed method can be applied to both ‘pre-treatment’ and ‘on treatment’ portal dosimetry for IMRT Head-and-Neck. The Gamma Index Method confirmed excellent validation rates of 97% (3%/3mm) and 95% (5%/3mm) for the ‘pre-treatment’ and ‘on treatment’ approach respectively. Pre-treatment verification of VMAT Head-and Neck treatment also reported excellent validation rates of 96% (3%/5mm). In addition, a convenient way to use the developed methodology within Dosimetry Check software was also piloted and tested. This presents an opportunity of future clinical implementation of the techniques developed in this investigation.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: EPID portal dosimetry; In vivo dose verification; AdABS.
Date of First Compliant Deposit: 4 October 2018
Last Modified: 04 Oct 2021 08:24

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