SIMULTANEOUS MAGNETIC-RESONANCE PHASE AND MAGNITUDE TEMPERATURE MAPS IN MUSCLE

Noninvasive magnetic resonance temperature maps that are used to monit or thermal ablation of tissue are described, In magnetic resonance ima ges, thermally induced proton nuclear magnetic resonance frequency shi fts, and changes in the longitudinal relaxation time produce both phas e and magnitude changes in the MR signal, Temperature maps with improv ed sensitivity are derived from the complex-difference nuclear magneti c resonance signal. Bovine muscle specimens were heated with focused u ltrasound to model thermal surgery and create a known thermal distribu tion to test the method, Resulting MR images acquired in 2 s produce t emperature maps with 1 mm resolution and 2 degrees C temperature sensi tivity. The temperature sensitivity was increased by extending the acq uisition to 5 s, by decreasing the receiver bandwidth, and increasing the echo time.