Precision of T1-relaxation time measurements in the hepatic portal vein: influence of measurement technique and sequence parameters

Objective To investigate the effects of a range of parameter settings on T 1 measurement stability in the portal vein using the T1-mapping sequences Look-Locker (LL) and Modified Look-Locker inversion recovery (MOLLI). Materials and methods Ten different versions of LL and MOLLI sequences were tested and compared to a reference sequence provided by the MR manufacturer. Ten healthy volunteers were imaged multiple times on two separate scan days at 3T. The mean T 1 values and coefficient of variation (CoV) were calculated for each of the ten sequences and compared to the reference sequence. Results Six of the tested sequences had T 1 values close to the reference sequence; among those, three sequences achieved lower CoV than the reference sequence. Lowest CoV was achieved using a non-triggered LL sequence with 5 beat readout and a 45 o flip angle (mean T 1 1733 ms ± 89 ms, CoV 1.3% ± 0.58%). Conclusion T 1 -measurements in the hepatic portal vein can be performed with high precision using either MOLLI or LL sequences provided that LL sampling duration is sufficiently long and flip angle sufficiently high. The advantage of constant timing outweighed the advantage of ECG-triggering.