Monitoring of high-intensity focused ultrasound-induced temperature changes in vitro using an interleaved spiral acquisition

An interleaved, spoiled gradient-echo spiral acquisition technique was implemented to monitor high-intensity focused ultrasound heating of porcine kidney ex vivo by measuring temperature induced phase shifts in the detected MR signal. Echo time, flip angle, repetition time, number of interleaves, and readout time were varied to observes effects on temperature sensitivity and phase-difference noise. The temperature response of the interleaved spiral acquisition was found to be comparable to a spoiled fast gradient-echo sequence of comparable in-plane spatial resolution. However, when imaging- with an optimal echo time, spiral acquisition offers dramatically increased temporal resolution for comparable spatial resolution. (C) 2000 Wiley-Liss, Inc.