Magnetic resonance imaging (MRI) is a diagnostic imaging modality that offers exceptional anatomical detail in standard applications such as studies in the central nervous system. More recently, it has been instrumental in the development of image-guided thermal ablation as a practical “surgical” alternative to tumor resection, owing to its multi-capability in image guidance, temperature monitoring, and assessment. However, more effective methods to control and monitor heating effects, and more accurate means to assess damage post-ablation, must be firmly established before its widespread adoption in the clinic becomes a reality.

This thesis addresses the problems of 1) good control of heat delivery and 2) accurate assessment of tissue damage post-ablation. In the first part of the thesis, determination of tissue thermal properties at the site of interest is proposed for more accurate control of the power required to achieve a desired temperature. A non-invasive method based on MRI-monitoring of thermal decay following a short focused ultrasound (FUS) pulse is described for the separate determination of thermal conductivity and perfusion. In the second part of the thesis, a new application of contrast kinetics is considered for improved assessment through the discrimination of subtle FUS-induced tissue changes. The method was evaluated in rabbits in a series of acute, sub-acute, and chronic studies. The feasibility of more accurate determination of the boundary of necrosis and better differentiation of tissue changes not visible on conventional MRI, was demonstrated.

These results have provided solutions to a few key practicality issues of image-guided thermal ablation. Further development of the concepts and methods proposed in this thesis hopefully will facilitate the widespread adoption of thermal ablation in the clinical setting.