Interventional radiology has changed the field of radiology over the last decade. Radiological guidance of instruments has resulted in increased efficiency and improved accuracy as a result of better visualization. Its use has also been expanded to procedures such as thermal therapy for treatment of solid tumors. However, one of the difficulties has been the lack of visualization of the progression of thermal damage. This dissertation describes the design, development and implementation of a system which utilizes temperature sensitive magnetic resonance imaging (MRI) techniques to guide and monitor interstitial thermal ablation procedures.; Calibration steps using T1 and diffusion weighted sequences showed to be effective in monitoring temperature changes for a low field 0.2 Tesla scanner. However, phase sensitive sequences, using the proton resonance dependence with temperature, showed increased sensitivity and accuracy compared to other techniques. A four-fold reduction of acquisition time for these phase sequences was accomplished through a keyholing technique.; The electronic noise from the radiofrequency generator has prohibited its use while monitoring with MRI. A passive electronic filter was effective in reducing this noise to a point where diagnostic thermal images could be acquired during the ablation process.; Maps representing tissue damage are more clinically relevant than temperature maps. An improved tissue damage model was developed based on MR temperature maps. A computer interface was developed to rapidly process and display the MR thermal images and color-coded damage maps to the physician.; Analysis of this system was performed using an in-vivo porcine model by applying laser and radiofrequency energy to the liver, muscle and brain. Histopathological analysis showed good correlation with the thermal damage maps. Postablation visualization of the lesions was improved by 5 to 7% by using a magnetization transfer technique.; Finally, the feasibility of a dedicated MR system was investigated for use in MR guided biopsies of breast lesions. Analysis on gelatin phantoms and cadaveric breast samples showed the efficacy of using this system in an open configuration MR magnet.; These developments establish the feasibility and utility of using novel MR imaging techniques for effective guidance of interventional instruments and monitoring of thermally ablated lesions.
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