MR temperature imaging using PRF phase difference and a geometric model-based fat suppression method.

BACKGROUND Because protons in fat do not exhibit a temperature-dependent frequency shift, proton resonance frequency shift (PRFS)-based MR thermometry always suffers from disturbances due to the presence of fats or lipids. OBJECTIVE A new fat suppression method for PRFS-based MR thermometry is proposed to obtain accurate variation of phase angle. METHODS Similar to the approach of separating fat and water with the two-point Dixon technique, we first scan a complex MR image for reference and then scan another complex image varying with temperature at the same TE point. Based on the conventional PRFS method, we use geometric relationships to remove the effect of fat on the variation of the phase angle. RESULTS Two phantoms with different water-to-fat ratios are involved in the temperature mapping test. Experimental results show that the temperature images of two phantoms are approximated under the same conditions. CONCLUSIONS The proposed fat suppression method is simple and effective for PRFS-based MR thermometry.