ONE-DIMENSIONAL NMR THERMAL MAPPING OF FOCUSED ULTRASOUND SURGERY

Objective: The aim of this study was to evaluate a technique for real- time monitoring of tissue temperature and tracking of the heat source during minimally invasive thermal interventions such as focused ultras ound surgery. Materials and Methods: A temperature-sensitive NMR line scan pulse sequence was directed interactively from a workstation duri ng the application of focused ultrasound to samples of excised bovine skeletal muscle. The NMR signal along a sensitive line was monitored d uring and after heating by means of a scrolling display on the worksta tion. Results: The temperature sensitivity was found to be similar to 2 degrees C with a time resolution of 300 ms along a line intersecting the ultrasonic focal point. Experimental temperature rises determined from the NMR signal showed close agreement with theoretical temperatu re behavior derived from the heat equation. Temperature quantitation c apabilities were lost upon onset of thermal denaturation and coagulati on. Conclusion: This technique could serve as a noninvasive guide in t racking the heat source and in monitoring thermal dose during focused ultrasound surgery and other minimally invasive thermal interventions.