Fast MR Thermometry Using Phase Referenced Asymmetric Spin-Echo EPI for High Field

Markus Nikola Streicher¹, Andreas Schfer¹, Dimo Ivanov¹, Laurentius Huber¹, Bibek Dhital¹, Enrico Reimer¹, Dirk Mller¹, Andre Pampel¹, Robert Trampel¹, Robert Turner¹

The proton resonance frequency shift MR-thermometry method is inherently very sensitive to magnetic field perturbations in time. We show an improved referenced spin-echo EPI sequence which enables paired water and fat image acquisition in 100 ms, and allows correction for almost all causes of in-vivo field drift, such as breathing. Frequency-selectivity of the spin-echo sequence is achieved by using reversed gradient amplitudes for excitation and refocusing. With an appropriate choice of parameters, the technique provides not only fat and water separation, but immediate acquisition of the reference map at the same slice position and with maximum signal amplitude.