Colorectal liver metastases on gadoxetic acid-enhanced MRI: Typical characteristics decrease after chemotherapy

Purpose: To determine to what extent colorectal liver metastases (CRLM) display typical imaging characteristics on gadoxetic acid-enhanced magnetic resonance imaging (MRI) and what changes after chemotherapy. Methods: We retrospectively identified 258 patients with a gadoxetic acid-enhanced MRI between 2015 and 2021 and pathologically proven non-mucinous adenocarcinoma CRLM. 722 unique CRLMs were analyzed: 378 CRLM in only the chemotherapy-naïve analysis; 217 in post-chemotherapy analysis; and 127 CRLM were analyzed both pre- and post-chemotherapy. The following six characteristics were defined as typical; “hypovascular”, “unenhanced T1-weighted (UE-T1W) hypointensity”, “arterial rim enhancement”, “non-enhancing during hepatobiliary phase”, “T2-weighted (T2W) mild hyperintensity”, and “diffusion restriction”. Results: All six typical characteristics were found in 249/505 chemotherapy-naïve CRLM (49 %) and 87/344 post-chemotherapy CRLM (25 %). The occurrence of some typical characteristics decreased post-chemotherapy: UE-T1W hypointensity 485/505 (96 %) versus 311/336 (93 %), arterial rim enhancement 291/498 (58 %) versus 154/301 (51 %), T2W mild hyperintensity 478/505 (95 %) versus 269/338 (79 %), and diffusion restriction 435/497 (87 %) versus 200/306 (65 %). Almost all metastases showed a hypovascular appearance, both in the chemotherapy-naïve (495/504, 98 %) and post-chemotherapy group (330/331, 100 %). Additionally, all CRLM appeared non-enhancing compared to the liver in the hepatobiliary phase (100 %). Conclusion: Most CRLM show various combinations of at least five typical characteristics on gadoxetic acid-enhanced MRI. Arterial rim enhancement is the least prevalent characteristic both in chemotherapy-naïve and post-chemotherapy patients. Post-chemotherapy the occurrence of typical MRI characteristics decreases, especially mild T2W hyperintensity and the presence of diffusion restriction.