Improved visualization of Liver Metastases Adjacent to Vessels using Hepatobiliary Phase Gadoxetic-acid-enhanced Single Shot Inversion-Recovery Gradient-Echo (IRGRE) MR Imaging

Objectives: To quantitatively compare contrast differences between liver metastases and vessels on Hepatobiliary Phase (HP) gadoxetic-acid-enhanced 2-Dimensional (2D) single-shot Inversion Recovery Gradient-Echo (IRGRE) and 3D Fat Saturated GRE (FSGRE) magnetic resonance images.

Methods: The study included 55 consecutive patients who had HP FSGRE and IRGRE (39 at 1.5T, 16 at 3T) for liver metastases evaluation obtained 20 minutes after gadoxetic-acid administration. Thirty-eight patients had metastases (23 at 1.5T, 15 at 3T). Regions of interest were drawn measuring signal intensity (SI) of the largest lesion, normal liver, inferior vena cava, and background noise. Signal-to-noise (SNR) and contrast-to-noise ratio (CNR), respectively, were calculated as SI divided by standard deviation (SD) of background noise, and (S1-S2)/SD, where S1 and S2 represented SI for tissue 1 and tissue 2. Statistical analysis was via the Wilcoxon Sign Rank test.

Results: Median liver-SNR for all 55 cases was greater for FSGRE than for IRGRE, as was lesion-SNR in the 38 with lesions (p<0.05). Vessel-SNR was greater for IRGRE than for FSGRE at 3T (p<0.05), with no difference between techniques at 1.5T (p>0.05). Median lesion/vessel contrast and CNR for the 38 cases with metastases at 1.5T and the 15 at 3T were, in absolute value, greater for IRGRE than for FSGRE (p<0.05). While both techniques yielded high lesion-liver contrast and CNR, only IRGRE provided consistently high lesion-vessel contrast and CNR (p<0.05).

Conclusion: Hepatobiliary-phase contrast difference between liver metastases and vessels was significantly and substantially greater for IRGRE than for FSGRE, potentially facilitating improved lesion detection using IRGRE.