Liver MRI with amide proton transfer imaging: feasibility and accuracy for the characterization of focal liver lesions

Abstract

Objective: To investigate the feasibility of using amide proton transfer (APT) magnetic resonance imaging (MRI) in the liver and to evaluate its ability to characterize focal liver lesions (FLLs).

Methods: A total of 203 patients with suspected FLLs who underwent APT imaging at 3T were included. APT imaging was obtained using a single-slice turbo spin-echo sequence to include FLLs through five breath-holds, and its acquisition time was approximately 1 min. APT signals in the background liver and FLL were measured with magnetization transfer ratio asymmetry (MTRasym) at 3.5 ppm. The technical success rate of APT imaging and the reasons for failure to obtain meaningful MTRasym values were assessed. The Mann Whitney U test was used to compare MTRasym values between different FLLs.

Results: The technical success rate of APT imaging in the liver was 62.1% (126/203). The reasons for failure were a too large B0 inhomogeneity (n = 43), significant respiratory motion (n = 12), and these two factors together (n = 22), respectively. Among 59 FLLs with analyzable APT images, MTRasym values were compared between 27 patients with liver metastases and 23 patients with hepatocellular carcinomas (HCCs). The MTRasym values of metastases were significantly higher than those of HCC (0.13 ± 2.15% vs. - 1.41 ± 3.68%, p = 0.027).

Conclusions: APT imaging could be an imaging biomarker for the differentiation of FLLs. However, further technical improvement is required before APT imaging can be clinically applied to liver MRI.

Key points: • Liver APT imaging was technically feasible, but with a relatively low success rate (62.1%). • Liver metastases showed higher APT values than hepatocellular carcinomas.