A method for an accurate T1 relaxation-time measurement compensating B1 field inhomogeneity in magnetic-resonance imaging

Abstract

Two-point gradient echo methods are practical means for estimating T1 value in magnetic-resonance (MR) imaging. Meanwhile, the inhomogeneity of the transmitted B1 field and the imperfect slice profile severely distorts the estimated T1 value. We propose a method for an accurate T1 measurement compensating the inhomogeneity of the B1 field and the effects of the imperfect slice profile. Three MR images of a whole human brain were obtained by multisliced spoiled gradient echo sequences on a 1.5-T scanner with different repetition times and flip angles to calculate the quantitative T1 maps. The histograms of the T1 maps showed two distinguishable peaks of the white matter (672.9±15.5ms) and the gray matter (921.1±24.7ms) of the human brain. The results indicate that the T1 value was properly estimated compensating the B1 field inhomogeneity and the slice profile imperfection. The proposed method is applicable to images obtained on any scanners with different parameters, because the method needs neither the information of the flip angle calibrations nor the phantom data to compensate the B1 field inhomogeneity.