Evaluation of variable flip angle, MOLLI, SASHA, and IR-SNAPSHOT pulse sequences for T1 relaxometry and extracellular volume imaging of the pancreas and liver.

Abstract

Compare fourT1-mapping pulse sequences for T1 relaxometry and extracellular volume (ECV) fraction of the pancreas and liver MATERIALS AND METHODS: In vitro phase of this prospective study was performed on a T1 phantom, followed by imaging 22 patients. Variable flip angle (VFA), modified Look-Locker inversion recovery (MOLLI), prototype saturation recovery single-shot acquisition (SASHA), and prototype inversion recovery (IR-SNAPSHOT) pulse sequences were used to obtain T1 and ECV maps on the same 1.5T MR scanner using the same imaging protocol. In vitro tests showed almost perfect precision of MOLLI (ρc = 0.9998), SASHA (ρc = 0.9985), and IR-SNAPSHOT (ρc = 0.9976), while VFA showed relatively less, however, substantial precision (ρc = 0.9862). Results of patient scans showed similar ECV fraction of the liver (p = 0.08), pancreas (p = 0.43), and T1 of the liver (p = 0.08) with all pulse sequences. T1 of the pancreas with MOLLI, SASHA, and IR-SNAPSHOT was statistically similar (p > 0.05). MOLLI, SASHA, and IR-SNAPSHOT provided almost perfect in vitro precision and similar T1 during in vivo scans. Similar ECV fractions of the liver and pancreas were obtained with all sequences. More refinement of pulse sequences to provide sufficient spatial coverage in one breath hold together with high precision would be desirable in abdominal imaging.