Abstract
OBJECTIVES: To identify characteristic vascular features of focal nodular hyperplasia (FNH) on microvascular flow imaging (MVFI) and assess the utility of MVFI in FNH diagnosis. METHODS: This retrospective study included B-mode ultrasound (US) and MVFI scans of 41 FNHs, 21 hepatocellular carcinomas (HCCs), 20 metastases (METs), 10 hepatocellular adenomas (HCAs), and eight hemangiomas (HEMs) from 80 patients. Diagnoses were confirmed by contrast-enhanced imaging or histology. Two independent observers evaluated vascular patterns on MVFI. Interobserver agreement was calculated, and logistic regression models using either B-mode or MVFI features were developed to differentiate FNH from other focal liver lesions (FLLs). RESULTS: Interobserver agreement for MVFI patterns was substantial (κ = 0.641, p < 0.001). The spoke-wheel pattern (OR = 51.53 and 35.28) and central artery (OR = 4.96 and 1.95) were strongly associated with FNH. However, the spoke-wheel pattern also appeared in subsets of HCAs (20%-30%), HCCs (14%-19%), and METs (5%-15%). Rim vascularity was common but nonspecific. The MVFI-based model (AUC = 0.891, p < 0.001) outperformed the B-mode model (AUC = 0.814) in distinguishing FNH. For lesions ≥3 cm, MVFI accuracy was even higher (AUC = 0.944, p < 0.001). CONCLUSION: MVFI enhances the diagnostic confidence of US for FNH, particularly in asymptomatic patients at low risk for malignancy. However, given the potential overlap with certain malignant FLLs, MVFI findings should be interpreted with caution.