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<div><p>Purpose</p><p>To assess the efficacy of contrast vector imaging (CVI) in detecting tumoral vascular structures and flow characteristics of focal liver lesions (FLLs) for differential diagnosis.</p><p>Materials and methods</p><p>In this prospective study, 65 participants with FLLs underwent CEUS using SonoVue with high-frame-rate imaging technique between July 2019 and October 2020. CVI was obtained by post-processing arterial cine imaging of CEUS. Tumoral vascular structures, velocity histogram, and mean velocities were compared among hepatocellular carcinoma (HCC), non-HCC malignancies, and benign tumors using the Chi-square and Kruskal-Wallis tests, respectively. The areas under the receiver operating characteristic curve (AUC) of CEUS in determining HCC probability was compared to that of CEUS with CVI using a z-test.</p><p>Results</p><p>CVI was technically successful in 52 of 65 (80%) participants (19 HCCs, 13 non-HCC malignancies, and 20 benign tumors). The detectability of tumoral vascular structures was significantly higher in CEUS with CVI, compared to CEUS alone (46.2% [24/52] vs. 100.0% [52/52], p<0.001). On CEUS with CVI, complex intratumoral and peripheral vessels were frequent in HCCs (100% of HCCs, 46.2% of non-HCC malignancies, and 70.0% of benign tumors), while detour vessels were frequent in non-HCC malignancies (none of HCCs, 53.8% of non-HCC malignancies, and 10.0% of benign tumors) (p<0.001). The mean velocity of HCC (26.3 mm/s) was the highest, while that of non-HCC malignancy (20.6 mm/s) was the lowest (p<0.001). CEUS with CVI showed higher AUC, compared to CEUS in both reviewers (0.851 vs. 0.963, p = 0.005 for reviewer 1; 0.853 vs. 0.982, p = 0.023 for reviewer 2).</p><p>Conclusion</p><p>CEUS with CVI better visualized vascular structures and flow characteristics of FLLs, and showed better diagnostic performance in determining HCC probability than CEUS.</p></div>