Defense Date


Document Type


Degree Name

Master of Science


Biomedical Engineering

First Advisor

Dorin Todor

Second Advisor

Ding-Yu Fei


A number of QA procedures have been developed for Breast Brachytherapy treatments, yet none guarantee accurate dose delivery or allow conformation of the actual source position leading to errors sometimes going unnoticed. The objective of this study is to track the exact path the HDR source would follow in real time. The exit radiation of the HDR source was used to image a well defined matrix of markers. The images were acquired using FPD and were processed to obtain projection coordinates while an x-ray calibration image was processed to obtain marker coordinates. Each marker along with its projection represents a line in 3D. A mathematical solution for the ‘near-intersection’ of two 3D lines was implemented and used to determine the ‘true’ 3D source position. A matrix with N markers will produce N*(N-1)/2 points of intersection and their mean will result in a more accurate source position. This study has proved that the accuracy of source position detection using a FPD is sub-millimeter.


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Date of Submission

August 2010