To investigate the ability of real-time contrast-enhanced harmonic US (CEUS) in assessing therapeutic response of hepatocellular carcinoma (HCC) treated with laser thermal ablation (LTA).

Before and after percutaneous treatment with LTA 68 HCCs (1.0-7.0 cm in size; mean,3.2 ± 1.3 cm) in 60 patients (41 men,19 females; age range, 45-80 years; mean age, 69.1 ± 8.2 years) were scanned using a phase array probe working at 1.5-3.0 MHz in harmonic mode after a single bolus injection of 2.5 ml of SonoVue (Bracco, Genoa, Italy). CEUS examinations were performed with real-time continuous scanning using a Sequoia equipment (Siemens, Erlangen, Germany) with contrast pulse sequence(CPS)software that enables non-destructive imaging at low MI (0.04-0.2). Video clips were digitally recorded on compact disc(CD). Continuous scanning was performed on the area harbouring the lesions and the areas treated for 180 seconds. Contrast enhancement within or close to the treated lesion during arterial phase was considered as residual viable tissue. 4 radiologists reviewed all video clips played forward and backward. Findings at contrast US studies were correlated with those at multidetector spiral CT. Follow-up protocol included CEUS and CT examination performed at 24-48 hours, and 3 month interval.

All radiologists correctly located all residual vital tissue. In 53/68 (77.9%) there was a positive correlation between CEUS and CT examination performed at 24-48 hours after LTA. No correlation was found in the remaining 15 (22.1%) lesions. CEUS and CT findings at 3 months confirmed these results. All foci undetected at CEUS were 1 cm or less in greatest dimension and located in segments very difficult to see with US and/or more than 8-10 cm from the skin surface.

CEUS could be a useful tool in evaluating therapeutic response to LTA. The sensitivity of the method is affected by vital foci size and by lesion location within the liver parenchyma.