UNI AND BI-DIMENSIONAL CONTINUOUS WAVE FREE PRECESSION (CWFP) METHODS: A GENERAL APPROACH AND APPLICATION

Carr-Purcell-Meiboom-Gill (CPMG) and Inversion Recovery (IR) are conventional methods used to measure the longitudinal (T1) and transverse (T2) relaxation times. Nevertheless, some fast method has been proposed to measure T1 and T2 in a single experiment in the last decades. Continuous Wave Free Precession condition (CWFP) sequences are one of those methods. CWFP is a special regime resulted from a train of radiofrequency (rf) pulses θ separated by a time interval shorter than the effective transverse relaxation time (T2*). Using θ equal to 90º on CWFP and CP-CWFP (Carr-Purcell-CWFP) methods, with or without phase alternation between the θ pulses, is possible to determine T1 and T2 simultaneously in a single experiment [1]. CWFP method also has been used as a single shot experiment to measure T1 using a low flip angle (θ ~5º), which was named CWFP-T1 sequence [2]. Besides that, CWFP-T1 was employed on 2D pulse sequences to obtain T1–T2 and diffusion-T1 correlation maps [3]. The application of Uni and bi-dimensional CWFP sequences have been demonstrating that those ones can be widely employed to determine fat/oil content and water compartmentalization in vegetal and animal tissues. This short talk will focus on a general approach to CWFP methods and some applications of these.