Hepatocellular carcinoma (HCC) is the sixth most common malignancy and the fourth leading cause of cancer-related deaths worldwide [1]. Although surgical resection remains the reference curative therapy, ultrasound-guided microwave ablation (MWA) yields comparable oncologic outcomes [2,3] and is endorsed as a first-line option in several national and international guidelines. A sufficient ablative ablation margins (AM) is pivotal for preventing local tumour progression (LTP) [4,5].

According to current consensus, technical success is judged one month after ablation using contrast-enhanced CT (CE-CT) or MRI (CE-MRI) together with long-term follow-up [6,7]. Yet, inflammatory changes within the ablation zone peak during the first few days, delaying reliable evaluation, increasing patient anxiety, and often necessitating multiple imaging sessions.In recent years, various fusion imaging methods have been used to assess AM after ablation in HCC patients, including CT-CT image fusion [8, 9], MR-MR image fusion [10, 11], and contrast-enhanced ultrasound (CEUS)-CT/MR image fusion [12, 13]. However, fusion imaging techniques require high-quality preoperative images, and post-operative liver displacement and deformation due to tumour removal can make image registration difficult.

Contrast-enhanced ultrasound (CEUS) is widely used in clinical practice due to its economic simplicity, lack of radiation, and ability to display lesion areas in real time [14-16]. Recently, fusion imaging based on 3D CEUS has been reported to show good accuracy in AM evaluation [17-19], but the assessment of AM for multiple ablations of multiple tumours remains uncertain.Therefore, the potential of CEUS for early assessment of AM should be further developed. Simultaneous-screen comparison contrast-enhanced ultrasound (SBS-CEUS) refers to the simultaneous comparison of arterial phase images before and after tumour ablation under the same settings of the ultrasound diagnostic instrument.Studies have shown [20] that SBS-CEUS has significant value in displaying liver lesions in difficult-to-visualise areas, but to date, no studies have systematically compared SBS-CEUS with CEUS in the assessment of AM.

This retrospective study therefore compared the diagnostic accuracy of SBS-CEUS versus CEUS for early (1-3 days) assessment of the AM after MWA in patients with HCC.

Inclusion Criteria:

a) HCC diagnosed according to EASL guidelines and confirmed by pathology and/or typical imaging features on CE-CT, CE-MRI, or CEUS;b) ≤3 lesions, each ≤5 cm, without vascular/bile-duct invasion or distant metastasis;c) CE-MRI performed at our centre ≤1 month before and ≤1 month after ablation (CE-CT for MRI-contraindicated patients) to serve as the reference standard;d)Baseline CEUS ≤7 days before MWA and follow-up CEUS 1-3 days after MWA .

Exclusion Criteria:

a) Severe comorbid disease;b) Missing mandatory imaging;c) Any condition judged by the investigators to preclude reliable data acquisition.