Consensus Report of the Third International Forum for Liver Magnetic Resonance Imaging:

Sirlin C, Song B, Taouli B, Yoshimitsu K, Koh DM. Consensus report from the 8th International Forum for Liver Magnetic Resonance Imaging

OBJECTIVES

The 8th International Forum for Liver Magnetic Resonance Imaging (MRI), held in Basel, Switzerland, in October 2017, brought together clinical and academic radiologists from around the world to discuss developments in and reach consensus on key issues in the field of gadoxetic acid-enhanced liver MRI since the previous Forum held in 2013.

METHODS

Two main themes in liver MRI were considered in detail at the Forum: the use of gadoxetic acid for contrast-enhanced MRI in patients with liver cirrhosis and the technical performance of gadoxetic acid-enhanced liver MRI, both opportunities and challenges. This article summarises the expert presentations and the delegate voting on consensus statements discussed at the Forum.

RESULTS AND CONCLUSIONS

It was concluded that gadoxetic acid-enhanced MRI has higher sensitivity for the diagnosis of hepatocellular carcinoma (HCC), when compared with multidetector CT, by utilising features of hyperenhancement in the arterial phase and hypointensity in the hepatobiliary phase (HBP). Recent HCC management guidelines recognise an increasing role for gadoxetic acid-enhanced MRI in early diagnosis and monitoring post-resection. Additional research is needed to define the role of HBP in predicting microvascular invasion, to better define washout during the transitional phase in gadoxetic acid-enhanced MRI for HCC diagnosis, and to reduce the artefacts encountered in the arterial phase. Technical developments are being directed to shortening the MRI protocol for reducing time and patient discomfort and toward utilising faster imaging and non-Cartesian free-breathing approaches that have the potential to improve multiphasic dynamic imaging.

KEY POINTS

• Gadoxetic acid-enhanced MRI provides higher diagnostic sensitivity than CT for diagnosing HCC. • Gadoxetic acid-enhanced MRI has roles in early-HCC diagnosis and monitoring post-resection response. • Faster imaging and free-breathing approaches have potential to improve multiphasic dynamic imaging.

Hepatocellular carcinoma 20 mm or smaller in cirrhosis patients: early magnetic resonance enhancement by gadoxetic acid compared with gadopentetate dimeglumine

PURPOSE

To evaluate the differences in enhancement pattern of hepatocellular carcinoma (HCC) 20 mm or smaller and enhancement effects of hepatic vessels on early dynamic contrast-enhanced magnetic resonance imaging (MRI) obtained with gadoxetic acid and gadopentetate dimeglumine in the same patients with cirrhosis.

METHODS

We reviewed MR images using gadoxetic acid and gadopentetate dimeglumine in the same 34 patients with 42 histologically confirmed HCCs (median diameter, 14.5 mm). The percentage enhancements (PEs) of HCC, the hepatic artery and portal vein and relative contrasts (RCs) between HCC and the liver were calculated and analyzed statistically.

RESULTS

The PEs of HCC, the hepatic artery and portal vein were significantly lower for gadoxetic acid in comparison with gadopentetate dimeglumine in the arterial phase (p = 0.0256 for HCC, p < 0.0001 for hepatic artery) and portal phase (p < 0.0001 for HCC, portal vein). The RC between HCC and the liver was significantly lower for gadoxetic acid in comparison with gadopentetate dimeglumine in the arterial phase (p = 0.0422), but was not significantly different in the portal phase (p = 0.1133). Forty-one of the 42 (97.62 %) nodules showed arterial hypervascularization. Of these, 31 (75.61 %) nodules were hypointense in the portal phase for gadoxetic acid, and 22 (53.66 %) were hypointense for gadopentetate dimeglumine (p = 0.038).

CONCLUSIONS

Compared with gadopentetate dimeglumine, gadoxetic acid-enhanced MRI demonstrated a different enhancement pattern of inferior arterial enhancement and was more rapidly hypointense in the portal phase for HCC. It showed markedly lower enhancement for hepatic artery and portal vein in the patients with cirrhosis.

Histological characteristics of small hepatocellular carcinomas showing atypical enhancement patterns on gadoxetic acid-enhanced MR imaging

PURPOSE

To define the histological characteristics of hepatocellular carcinomas (HCCs) showing atypical dynamic enhancement patterns on gadoxetic acid-enhanced dynamic magnetic resonance imaging (EOB-MRI).

MATERIALS AND METHODS

We evaluated a total of 130 small (≤ 3 cm) HCCs from 114 patients that were surgically removed after EOB-MRI. Two radiologists blinded to the histological findings retrospectively classified the HCCs into typical or atypical lesions. Gross morphology, nuclear histological grade, presence of vascular invasion, and capsule formation and infiltration were compared between the two groups using Chi-square or Fisher tests.

RESULTS

Atypical dynamic enhancement patterns were seen in 23 HCCs (17.7%). None of the atypical HCC showed vascular invasion (P < 0.001). Atypical HCCs also showed more frequently smaller size (1.6 ± 0.6 cm versus 2.1 ± 0.6 cm, P = 0.001) with 86.9% (n = 20) of which 2 cm or less in diameter (P = 0.001), vaguely nodular appearance (56.5% vs 3.7%, P < 0.001), and nuclear grade I (69.6% versus 6.5%, P < 0.001), while less frequently showed capsule formation (26.1% versus 77.6%, P < 0.001) or capsular infiltration (16.7% versus 77.1%, P = 0.005).

CONCLUSION

Atypical HCCs on EOB-MRI may be characterized by the absence of vascular invasion, smaller (< 2 cm or less) size, vaguely nodular appearance, and well differentiation, and infrequent capsule formation or capsular infiltration.