Percutaneous Radiofrequency Ablation of Small (1–2 cm) Hepatocellular Carcinomas Inconspicuous on B-Mode Ultrasonographic Imaging: Usefulness of Combined Fusion Imaging with MRI and Contrast-Enhanced Ultrasonography

Figure 4

Images from a 65-year-old man with a recurrent HCC and hepatitis B virus-related liver cirrhosis who had previously undergone chemoembolization for HCC.

(a) Delayed-phase MRI obtained three minutes after contrast injection showing a 1.1-cm hypointense nodule (arrow) with peripheral rim enhancement in segment 6. Note that the tumor abuts the liver capsule and is located close to the right rib

(b) On planning US with fusion imaging, a subtle hypoechoic lesion (arrow) was identified at a similar location (arrow) on fused MRI; the lesion was given a conspicuity score of 3 as it was nearly isoechoic to the surrounding liver and less than 50% of the tumor had a well-defined margin

(c) On arterial-phase CEUS, the lesion identified on the previous fusion images did not show arterial enhancement. When the patient breathed in slightly, the liver moved somewhat downwards and the true enhanced lesion (arrow), which was initially located below the right rib, appeared. Note that a portal vein branch (arrowheads) is not seen on US in (b), indicating that the image plane is different from that of (b) even though the US image was obtained at the same intercostal space

(d) The lesion was seen as a defect (arrow) on the post-vascular phase and the tumor was given a conspicuity score of 1 on CEUS-added fusion imaging

(e) An RF electrode (arrowheads) was positioned in the index tumor (arrow) with confidence under CEUS-added fusion imaging guidance, after which RF energy was applied

(f) Arterial-phase image of post-RFA CT revealed complete ablation of the tumor with sufficient ablative margins (arrowheads)