Precision of T_1-relaxation time measurements in the hepatic portal vein: influence of measurement technique and sequence parameters

摘要

Objective To investigate the effects of a range of parameter settings on T_1 measurement stability in the portal vein using the T_1-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 45o 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.