Ultra-short T2 components imaging of the whole brain using 3D dual-echo UTE MRI with rosette k-space pattern

Purpose This study aimed to develop a new 3D dual-echo rosette k-space trajectory, specifically designed for UTE MRI applications. The imaging of the ultra-short transverse relaxation time (uT(2)) of brain was acquired to test the performance of the proposed UTE sequence. Theory and Methods The rosette trajectory was developed based on rotations of a "petal-like" pattern in the k(x)-k(y) plane, with oscillated extensions in the k(z)-direction for 3D coverage. Five healthy volunteers underwent 10 dual-echo 3D rosette UTE scans with various TEs. Dual-exponential complex model fitting was performed on the magnitude data to separate uT(2) signals, with the output of uT(2) fraction, uT(2) value, and long-T-2 value. Results The 3D rosette dual-echo UTE sequence showed better performance than a 3D radial UTE acquisition. More significant signal intensity decay in white matter than gray matter was observed along with the TEs. The white matter regions had higher uT(2) fraction values than gray matter (10.9% +/- 1.9% vs. 5.7% +/- 2.4%). The uT(2) value was approximately 0.10 ms in white matter . Conclusion The higher uT(2) fraction value in white matter compared to gray matter demonstrated the ability of the proposed sequence to capture rapidly decaying signals.