In Vivo Monitoring of HIFU Induced Temperature Rise in Porcine Liver Using Magnetic Resonance Thermometry

摘要

High intensity focused ultrasound (HIFU) is a noninvasive medical procedure during which a large amount of energy is deposited in a short duration, which causes sudden localized rise in tissue temperature, and ultimately, cell necrosis. In the preclinical characterization of thermal fields generated by HIFU systems, the temperature rise in an ex vivo or an in vivo tissue must be accurately measured. The temperature rise can be measured using thin wire thermocouples or magnetic resonance (MR) thermometry. Among the two methods, thermocouples can be embedded invasively in the animal tissue, and HIFU induced temperature rise can be measured by focusing the beam on the thermocouple junction for the desired sonication time. However, the temperature rise measured using thermocouples is subject to several significant sources of error. One source of error associated with direct HIFU sonication of thermocouples is viscous-heating artifact [1]. Positioning errors represent another challenge in measuring temperature by locating beam atop a thermocouple [2]. Consequently, it has been difficult to accept that the temperature recorded by the thermocouple is the actual temperature at the focus of the HIFU beam. Therefore, there is a need for a method that can address these limitations.