Development and Clinical Application of a New Two-Dimensional in vivo Dosimetry by Electronic Portal Imaging

atmire.migration.oldid5302
dc.contributor.advisorSmith, Wendy
dc.contributor.advisorBrown, Derek
dc.contributor.authorPeca, Stefano
dc.contributor.committeememberAnsbacher, Will
dc.contributor.committeememberHahn, Leszek
dc.contributor.committeememberKurien, Elizabeth
dc.contributor.committeememberPloquin, Nicolas
dc.date.accessioned2017-02-13T18:42:04Z
dc.date.available2017-02-13T18:42:04Z
dc.date.issued2017
dc.date.submitted2017en
dc.description.abstractIn vivo dosimetry (IVD) in radiotherapy refers to direct measurement of dose deposited in the patient during treatment. IVD can be of great use in early detection of harmful errors, for assessment of patient setup and anatomy changes, and to guide adaptive radiotherapy. Routine IVD is hindered by the costs and complexities associated with most systems, and thus has not obtained widespread application. In this thesis I describe a novel method of using the electronic portal imaging device (EPID) for IVD. Images are measured through phantoms/patients making use of treatment beams. From these, 2D dose maps at isocentre depth are calculated from signal-to-dose correlation ratios. Convolution by optimized multi-Gaussian kernels, specific to direction (cross-plane, in-plane), field size, and attenuator thickness, allows dose modelling in the whole plane. The EPID-calculated dose map is compared to that predicted by the treatment planning system (TPS) by pixel-wise comparison, gamma analysis, and a novel approach of morphological connected component analysis. Tests with off-reference values of phantom thickness, field size, and monitor units showed good agreement, with the great majority of points within ±3% of TPS dose. The method was evaluated on 20 patients, spanning multiple body sites and treatment techniques (334 fields). Excluding lung treatments, the mean dose difference at isocentre had good accuracy at 1.5±6.6 %. The large standard deviation is due to both algorithm limitations and true differences, mainly anatomical changes and setup variability. In the isocentre plane, the median area that passed 10% / 3 mm gamma analysis was 96.1%. In three of ten rectal cancer patients, soft tissue differences resulting from suboptimal setup and immobilization devices caused up to 2% overdose to the small bowel. Results suggest that connected component analysis may be as good or superior to gamma analysis for detection of specific dose differences. Further work is necessary before clinical implementation, but EPID IVD by correlation ratios has enormous potential for error detection, process quality assurance, and adaptive treatment guidance, thus increasing safety and quality of radiotherapy.en_US
dc.identifier.citationPeca, S. (2017). Development and Clinical Application of a New Two-Dimensional in vivo Dosimetry by Electronic Portal Imaging (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25639en_US
dc.identifier.doihttp://dx.doi.org/10.11575/PRISM/25639
dc.identifier.urihttp://hdl.handle.net/11023/3648
dc.language.isoeng
dc.publisher.facultyGraduate Studies
dc.publisher.institutionUniversity of Calgaryen
dc.publisher.placeCalgaryen
dc.rightsUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subjectOncology
dc.subjectPhysics--Radiation
dc.subjectEngineering--Biomedical
dc.subject.otherRadiation Therapy
dc.subject.otherIn vivo dosimetry
dc.subject.otherPortal dosimetry
dc.titleDevelopment and Clinical Application of a New Two-Dimensional in vivo Dosimetry by Electronic Portal Imaging
dc.typedoctoral thesis
thesis.degree.disciplinePhysics and Astronomy
thesis.degree.grantorUniversity of Calgary
thesis.degree.nameDoctor of Philosophy (PhD)
ucalgary.item.requestcopytrue
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