Rapid field-cycling MRI using fast spin-echo.

PURPOSE Fast field-cycling MRI (FFC-MRI) is a technique that promises to expand upon the diagnostic capabilities of conventional MRI by allowing the main field, B0 , to be varied during a pulse sequence, thus allowing access to new types of endogenous contrast. However, this necessitates longer scan times, which can limit the technique's application to clinical research. In this paper, an adaptation of the fast spin-echo (FSE) pulse sequence for use with FFC-MRI is presented, known as field-cycling fast spin-echo (FC-FSE). This technique allows much faster image acquisition, thus shortening scan times significantly. METHODS Image quality and relaxometric accuracy were assessed by comparison of phantom images with data obtained using conventional techniques. As proof of principle, relaxometric images were obtained from the thighs of a human volunteer. RESULTS Image quality remains good for speedup factors of up to 4-fold. The accuracy of relaxometry data is in good agreement with conventional techniques. Results from a volunteer study were encouraging, demonstrating that the technique is sensitive enough to detect quadrupole peaks in vivo. CONCLUSION The technique has been demonstrated in phantom experiments with little loss of image quality or relaxometric accuracy. Initial in-vivo results pave the way for future clinical studies.