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Abstract: Currently, the Cross Cancer Institute uses CT imaging in conjunction with the traditional Manchester system, which prescribes dose to a defined point, for cervix cancer brachytherapy. To take advantage of MRI for enhanced definition of soft tissue including the cancerous tissue itself, this thesis focuses on a study of MR image-guided cervix brachytherapy. Firstly, the geometric distortions of an applicator in an MR image and the accuracy of CT-MRI registration were quantitatively evaluated with a custom-made phantom, which provides one measure of the MRI distortion and indicates a CT-MRI registration method for cervix brachytherapy. The remaining part of the thesis describes an optimization method - simulated annealing (SA) - for automatically determining the dwell time configuration based on a set of specified dose-volume constraints. Application to a computer simulation model showed that SA was effective when the model structure sizes and distances are in a normal range. The effects on the optimization of different initial dwell times and a different initial number of dwell positions were also investigated. In general, optimization conformed dose to the target and significantly reduced dose to surrounding normal tissue.