Self-gated 4D-MRI of the liver: Initial clinical results of continuous multiphase imaging of hepatic enhancement.

Purpose: To evaluate the feasibility of a self-gated free-breathing volume-interpolated breath-hold examination (VIBE) sequence using compressed sensing (CS) for contrast-enhanced multiphase liver MRI. Materials and Methods: We identified 23 patients who underwent multiphase gadobutrol-enhanced liver magnetic resonance imaging (MRI) using 1) a prototype free-breathing VIBE sequence with respiratory self-gating and CS (VIBECS), and 2) a standard breath-hold VIBE (VIBESTD) on the same 1.5T scanner at two timepoints. VIBECS was continuously acquired for 128 seconds and a time-series of 16 timepoints was jointly reconstructed from the dataset. The unenhanced, arterial, portal-venous, and venous timepoints with the best image quality were selected and compared to the corresponding VIBESTD series serving as reference. Image quality was assessed qualitatively (image quality, sharpness, lesion conspicuity, vessel contrast, noise, motion/other artifacts; two readers independently; 5-point Likert scale; 5 = excellent) and quantitatively (vessel contrast [VC], coefficient-of-variation [CV]) Statistics were performed using Wilcoxon-sign-rank (ordinal) and paired t-test (continuous variables). Results: Image quality and lesion conspicuity revealed no significant differences between the sequences (P >= 0.3). VIBESTD showed a tendency to higher motion artifacts (P >= 0.07). Image sharpness significantly increased in VIBECS as compared to VIBESTD (P <= 0.03). Arterial phase vessel contrast appeared significantly lower in VIBECS than in VIBESTD (P = 0.04). VIBECS showed reconstruction artifacts not present in VIBESTD (P = 0.001). Image noise was significantly lower in VIBECS than in VIBESTD (P <= 0.004). Arterial phase VC was significantly lower in VIBECS than in VIBESTD (P = 0.01). CV revealed no differences between sequences (P = 0.7). Conclusion: VIBECS is feasible for continuous free-breathing contrast-enhanced multiphase liver MRI, providing similar image quality and lesion conspicuity as VIBESTD.