A “Variable Flip Angle” Radial Steady-State Free Precession Technique with Slice Profile Correction

Introduction: Steady-state free precession (SSFP) techniques have drawn significant attention due to their speed, good tissue contrast and spatial resolution. Recently, it was demonstrated that SSFP methods can be used to estimate MR-dependent tissue parameters [1,2,3]. In [1], it was shown that a “variable flip angle” radial steady-state free precession (RAD-SSFP) method can be used for the discrimination of malignant from benign lesions using a parameter called the R-factor. The advantage of the technique is that high resolution R-factor maps can be obtained from data acquired in a very short period of time (~ 3-4 s per slice) which makes the technique attractive for tissue characterization in regions of the body where fast imaging is needed. The R-factor, however, has a complex relationship to T1 and T2. In this work, we demonstrate the capability of using the “variable flip angle” RAD-SSFP for the direct and fast estimation of the T1/T2 ratio. The T1/T2 ratio is a parameter that is more intuitively related to the tissue characteristics. As shown in Table 1, different tissues and pathologies have distinct T1/T2 ratios, thus the parameter can be used for tissue characterization.