Spectral fat saturation and accuracy of proton-resonance frequency shift MR thermometry

Motivation: Monitoring thermal ablations with PRFS thermometry ensures therapy safety and efficiency. Spectral fat saturation cannot be 100% efficient: the remaining fat signal may affect PRFS temperature measurements. Goal(s): This work experimentally evaluates the residual signal after spectral fat saturation, and the error it causes in PRFS thermometry. Approach: The IDEAL algorithm is used to quantify fat signal after spectral fat saturation. The error in PRFS thermometry with spectral fat saturation is evaluated in fat-water phantoms. Results: The residual fat signal after spectral fat saturation leads to errors in PRFS thermometry, that increase with the fat content, and oscillate with TE and absolute temperature. Impact: This work demonstrates experimentally that PRFS temperature errors can be significant during hyperthermia despite fat suppression methods. Careful selection of the TE according to spectral fat saturation strategy can mitigate such errors and improve the accuracy of PRFS thermometry.