Advanced Techniques in the Percutaneous Ablation of Liver Tumours

Abstract

Percutaneous ablation is an accepted treatment modality for primary hepatocellular carcinoma (HCC) and liver metastases. The goal of curative ablation is to cause the necrosis of all tumour cells with an adequate margin, akin to surgical resection, while minimising local damage to non-target tissue. Aside from the ablative modality, the proceduralist must decide the most appropriate imaging modality for visualising the tumour and monitoring the ablation zone. The proceduralist may also employ protective measures to minimise injury to non-target organs. This review article discusses the important considerations an interventionalist needs to consider when performing the percutaneous ablation of liver tumours. It covers the different ablative modalities, image guidance, and protective techniques, with an emphasis on new and advanced ablative modalities and adjunctive techniques to optimise results and achieve satisfactory ablation margins.

Keywords: hepatocellular carcinoma; liver metastases; percutaneous ablation.

Figure 1

Ablation of a large, centrally located tumour using irreversible electroporation (IRE) with documented abscopal effect in a 58-year-old male with known history of hepatitis B cirrhosis and multiple prior treatments for multi-focal hepatocellular carcinoma (HCC) including trans-arterial chemoembolization (TACE), Y-90 radioembolization (RE) and trial of oral Sorafenib. (A) Axial T1W contrast image in the delayed phase shows a 3.8 cm HCC (red circle) in segment 5 of the liver with viable tumour despite prior trans-arterial treatments. (B) A more superior axial image of the same study reveals another 4.9 cm central HCC (yellow circle) with viable tumour, in segment 4 of the liver compressing the biliary confluence and causing distal biliary obstruction. With the elevated bilirubin, patient was unable to continue with oral Sorafenib and with a palliative intent, IRE was offered for this particular tumour. (C) Axial contrast CT image taken in the portovenous phase on the day of the procedure demonstrating enhancing viable tumour (yellow star) within the segment 4 HCC. Note the traces of lipiodol (black arrowhead) within the other tumour in segment 4, distally treated previously with TACE. (D) 3D volume rendering technique (VRT) image of the 7 IRE electrodes placed in order for satisfactory tumour ablation. (E) Photograph of the IRE electrodes over the skin during the ablation procedure. (F) Post-contrast axial CT image immediate post-ablation show a satisfactory ablation zone; note a tiny pocket of gas within the ablation zone, which can be commonly seen post-IRE ablation. (G) Axial T1W post-contrast image in the delayed phase 6 weeks after the procedure showed a complete response in the segment 4 HCC with significant reduction in the size of the tumour. Unfortunately, the biliary dilatation persisted despite the ablation, and patient’s bilirubin levels remained elevated. (H) Interestingly, the segment 5 tumour had also shown a complete response with reduction in tumour size, demonstrating the abscopal effect which can be seen in IRE cases.

Figure 2

Magnetic resonance–ultrasound (MR–US)-guided fusion and contrast-enhanced ultrasound for targeting of a hepatic tumour in a 65-year-old male with known chronic hepatitis B. (A) Axial T1W contrast image in the arterial phase reveals a 1.4 cm, ovoid, arterially enhancing lesion compatible with HCC, in segment 8 of the liver. The lesion was radiologically occult on grey-scale ultrasound. (B) MR–US guided fusion performed with the patient in a slightly left lateral oblique position to improve the ultrasound acoustic window. The faint dotted oval marks the expected location of the lesion. (C) The lesion was not seen on grey-scale US; therefore, contrast-enhanced US was performed after administering a 2.4 mL IV bolus of Sonovue (GE Healthcare) contrast. This CEUS image captured in the arterial phase (15–45 s) reveals the enhancing lesion (white arrow) in close vicinity of the “fused” image as indicated by the faint dotted oval, thus confirming utility of the MR–US guided fusion software. (D,E) A 15 cm Emprint (Covidien) microwave antenna was placed through the expected location of the tumour (yellow arrowhead) with the tip approximately 0.5–1 cm beyond (white arrowhead). Ablation was performed in this location for 10 min at 100 W. (F) Axial T1W contrast image in the portovenous phase, 6 weeks later, shows a satisfactory ablation zone with no evidence of residual tumour.

Figure 3

Microwave ablation of a subcapsular tumour using the “no-touch” technique in a 71-year-old male with a known history of chronic hepatitis B. (A) Subtracted axial T1W contrast image in the arterial phase reveals a 1.5 cm, rounded, arterially enhancing lesion in an anterior subcapsular location in segment 3, compatible with HCC. (B) Transverse ultrasound image at the time of ablation shows a 14 cm Soler (AngioDynamics) microwave antenna placed in a lateral-to-medial fashion posterior and slightly away from the tumour (red star), with the tip just touching the falciform ligament (yellow arrow). The aim of this no-touch technique is to create a “wedge” ablation without the antenna traversing through tumorous tissue. (C) Ultrasound image taken during the ablation cycle shows the echogenic storm cloud representing the ablation zone covering the lesion (yellow star). (D) Post-contrast axial CT image immediately post-ablation shows a satisfactory ablation zone with good margins and no residual tumour enhancement.

Figure 4

Creation of iatrogenic pneumothorax for microwave ablation of hepatic dome lesion in a 76-year-old female with known cryptogenic liver cirrhosis, and previous ablation and TACE therapies for tumours elsewhere in the liver. (A) Axial T1W contrast image in the arterial phase reveals a 2.1 cm, oblong, arterially enhancing lesion (orange arrow) compatible with HCC, near the hepatic dome in segment 8 of the liver. The lesion is also medially abutting the right atrial appendage of the heart. (B) Contrast enhanced CT image taken in the arterial phase during the time of ablation under general anaesthesia, demonstrating the tumour. (C) Artificial pneumothorax (yellow star) created using an 18 G cannula under CT fluoroscopy followed by subsequent insertion of an 8 F pigtail drainage catheter into the pleural space using the Seldinger technique (black arrow). A 19 cm Solero (AngioDynamics) microwave antenna was advanced intermittently under CT fluoroscopy with the tip (white arrowhead) just penetrating the diaphragmatic margin. (D) Further advancement of the microwave antenna with the tip seen (black arrowhead) at the posterior margin of the tumour, using the right atrial appendage as a landmark. (E,F) Post-contrast axial and coronal reconstructed CT images immediately post-ablation show a satisfactory ablation zone with adequate margins. (G) After the ablation, the pneumothorax is aspirated via the chest drain (black arrow) with full re-expansion of the right lung. (H) Axial contrast CT image taken 6 months post-ablation show involution of the ablation zone with no enhancing recurrent tumour seen.

Figure 5

Microwave ablation of a juxta-cardiac tumour in an 80-year-old female with a known history of hepatitis B cirrhosis, Childs-Pugh A5, ECOG 0. (A) Post-contrast delayed coronal T1W image shows a 1.7 cm hepatocellular carcinoma (HCC) in segment 2 of the liver in a juxta-cardiac location. (B) Transverse-oblique ultrasound image at the time of ablation demonstrates the tumour to be well-visible, echogenic, and well-circumscribed in appearance (black arrowhead and white ‘+’). Immediately posterior to the tumour is the heart. RV, right ventricle; LV, left ventricle. (C) 20 cm Emprint (Covidien) microwave antenna placed under ultrasound in a sagittal orientation, with the tip guided to the centre of the tumour (yellow arrow). Antenna placement via this orientation is beneficial for 2 reasons; firstly, the heart is always visible (red star) during antenna placement to avoid inadvertent iatrogenic injury, and secondly, the ablation beyond the tip of the antenna is usually the “weakest” portion of the ablation zone, thus preventing inadvertent thermal injury to the myocardium. (D) Ultrasound image taken during the ablation cycle shows the echogenic storm cloud representing the ablation zone covering the lesion. (E,F) Post-contrast coronal and sagittal reconstructed CT images immediately post-ablation show a satisfactory ablation zone with no adjacent myocardial wall thickening or inadvertent iatrogenic cardiac injury.

Figure 6

Ultrasound-guided hydrodissection with “torque” technique in a 78-year-old male with a known history of hepatitis B cirrhosis, Childs-Pugh B7. (A) 20 min delayed axial T1W images with Primovist contrast show a 2.1 cm hepatocellular carcinoma (HCC) in segment 3 of the liver abutting the anterior wall of the antrum of the stomach. (B) Slightly superior but immediately adjacent to this is a separate 0.9 cm satellite nodule (yellow arrow), also compatible with HCC. (C) Sagittal oblique ultrasound image at the time of ablation shows the tumours (yellow ‘+’) to be adjacent to each other, well-circumscribed, and echogenic in appearance. S, stomach. (D) An 18 G Chiba needle is inserted along the plane between the inferior edge of the liver and the superior margin of the stomach (black arrow) until the tip is seen beyond the stomach wall (black arrow) under real-time US guidance. D5 solution is infused through the needle, which can be seen accumulating in this space (white arrow). As more fluid is instilled, gentle force is applied in a cranial fashion on the Chiba needle externally, “torquing/levering” the stomach further inferiorly away from the liver. (E) A 20 cm Neuwave (Johnson and Johnson) PR XT antenna is placed through the centre of both the tumours, with the tip of the antenna (black arrow head) seen beyond the satellite nodule. (F) More “levering” and fluid is instilled during the ablation cycle, which is seen by the echogenic storm cloud encompassing the tumours. (G,H) Post-contrast coronal and sagittal reconstructed CT images immediately post-ablation show a satisfactory ablation zone with no adjacent stomach wall thickening, stranding or free intraperitoneal gas.