Abstract: Objective The aim of this study was to explore the diagnostic performance of contrast-enhanced magnetic resonance imaging (MRI) and intravoxel incoherent motion-diffusion weighted imaging (IVIM-DWI) in patients with small hepatocellular carcinoma (sHCC). Methods 73 patients with focal nodular hyperplasia (FNH ) were enrolled in our hospital between May 2020 and May 2023, and all patients underwent contrast-enhanced MRI and IVIM-DWI, recording the pseudo diffusion coefficient (D^*), true diffusion coefficient (D) and perfusion fraction (f). The fine needle aspiration biopsies or postoperative histopathology were performed for golden diagnosis. The diagnostic efficacy of contrast-enhanced MRI and IVIM-DWI was evaluated by receiver operating characteristic (ROC) curves. Results Among the 73 patients with FNH, the histopathology examination showed sHCC in 49 cases (67.1%) and the dysplastic nodules (DN) in 24 cases(32.9%); the percentages of low signals on T1WI, high signals on T2WI, arterial phase enhancement and low signals during hepatobiliary phase in HCC lesions were 61.2%, 83.7%, 59.2% and 89.8%, all significantly higher than 20.8%, 33.3%, 25.0% and 29.2%(P＜0.05) in DN lesions; the D^* and D in HCC lesions were (50.9±11.6)×10^-3mm²/s and (0.8±0.2)×10^-3mm²/s, both significantly less than [(78.4±15.8)×10^-3mm²/s and (1.2±0.3)×10^-3mm²/s, P＜0.05] in DN lesions, while there was no significant difference as respect to f between the two lesions [(45.6±8.7)% vs.(43.9±9.5)%, P＞0.5]; the ROC analysis showed the AUC was 0.968, with the sensitivity of 100.0% and the specificity of 86.0%, when the T1WI and T2WI signals, arterial phase enhancement, hepatobiliary phase signal, D^* and D was combined for the diagnosis of sHCC. Conclusion The contrast-enhanced MRI and IVIM-DWI are efficacious in the diagnosis of patients with sHCC, which might provide the clinicians a reliably tool for early differentiation of patients with FNH.

Key words: Hepatoma, Dysplastic nodules, Contrast-enhanced magnetic resonance imaging, Intravoxel incoherent motion-diffusion weighted imaging, Diagnosis