Microwave ablation in primary and secondary liver tumours: technical and clinical approaches

Abstract

Thermal ablation is increasingly being utilised in the treatment of primary and metastatic liver tumours, both as curative therapy and as a bridge to transplantation. Recent advances in high-powered microwave ablation systems have allowed physicians to realise the theoretical heating advantages of microwave energy compared to other ablation modalities. As a result there is a growing body of literature detailing the effects of microwave energy on tissue heating, as well as its effect on clinical outcomes. This article will discuss the relevant physics, review current clinical outcomes and then describe the current techniques used to optimise patient care when using microwave ablation systems.

Keywords: Hepatocellular carcinoma; hydrodissection; liver metastasis; microwave ablation; percutaneous microwave ablation; thermal ablation.

Figure 1

84-year old female with a history of cirrhosis and hepatitis C. A) Contrast-enhanced computed tomography (CECT) image demonstrates an arterial-enhanced lesion in segment IV measuring 4.0 cm (arrow). B) Lesion was treated with the placement of a single cooled microwave antenna at 40 W for 15 minutes. C) 24-hour post-procedural CECT demonstrates the presence of a thick hypervascular peri-ablation halo (triangles). This finding can be seen from the hyperemic reaction that regularly develops around an ablation zone. D) Four-year follow-up of an arterial-phase (left) and portal-venous phase (right) CECT demonstrates contraction of the ablation zone (arrow) with no evidence of enhancement.

Figure 1

84-year old female with a history of cirrhosis and hepatitis C. A) Contrast-enhanced computed tomography (CECT) image demonstrates an arterial-enhanced lesion in segment IV measuring 4.0 cm (arrow). B) Lesion was treated with the placement of a single cooled microwave antenna at 40 W for 15 minutes. C) 24-hour post-procedural CECT demonstrates the presence of a thick hypervascular peri-ablation halo (triangles). This finding can be seen from the hyperemic reaction that regularly develops around an ablation zone. D) Four-year follow-up of an arterial-phase (left) and portal-venous phase (right) CECT demonstrates contraction of the ablation zone (arrow) with no evidence of enhancement.

Figure 1

84-year old female with a history of cirrhosis and hepatitis C. A) Contrast-enhanced computed tomography (CECT) image demonstrates an arterial-enhanced lesion in segment IV measuring 4.0 cm (arrow). B) Lesion was treated with the placement of a single cooled microwave antenna at 40 W for 15 minutes. C) 24-hour post-procedural CECT demonstrates the presence of a thick hypervascular peri-ablation halo (triangles). This finding can be seen from the hyperemic reaction that regularly develops around an ablation zone. D) Four-year follow-up of an arterial-phase (left) and portal-venous phase (right) CECT demonstrates contraction of the ablation zone (arrow) with no evidence of enhancement.

Figure 1

84-year old female with a history of cirrhosis and hepatitis C. A) Contrast-enhanced computed tomography (CECT) image demonstrates an arterial-enhanced lesion in segment IV measuring 4.0 cm (arrow). B) Lesion was treated with the placement of a single cooled microwave antenna at 40 W for 15 minutes. C) 24-hour post-procedural CECT demonstrates the presence of a thick hypervascular peri-ablation halo (triangles). This finding can be seen from the hyperemic reaction that regularly develops around an ablation zone. D) Four-year follow-up of an arterial-phase (left) and portal-venous phase (right) CECT demonstrates contraction of the ablation zone (arrow) with no evidence of enhancement.

Figure 2

67-year old female with liver metastasis from colorectal cancer. A) Pre-ablation magnetic resonance (MR) imaging (left) of liver lesion (arrow) and CEUS (right) confirming presence of 13 by 14 mm liver lesion (arrow) B) The lesion was treated with a single water-cooled antenna at 50 W for 6 minutes (left). Post-ablation image demonstrating hyper-echoic region measuring 34 mm by 37 mm, representing the ablation zone (right). The goal is to create ablation margins > 1 cm beyond tumor boundary. C) Post-ablation B-mode ultrasound (left) and CEUS (right) showing the ablation zone (anechoic) with the presence of the hypervascular peri-lesional halo. D) CECT (left) and CEUS (right) demonstrating ablation zones that encompass the entire lesion measuring 32 by 42 mm.

Figure 2

67-year old female with liver metastasis from colorectal cancer. A) Pre-ablation magnetic resonance (MR) imaging (left) of liver lesion (arrow) and CEUS (right) confirming presence of 13 by 14 mm liver lesion (arrow) B) The lesion was treated with a single water-cooled antenna at 50 W for 6 minutes (left). Post-ablation image demonstrating hyper-echoic region measuring 34 mm by 37 mm, representing the ablation zone (right). The goal is to create ablation margins > 1 cm beyond tumor boundary. C) Post-ablation B-mode ultrasound (left) and CEUS (right) showing the ablation zone (anechoic) with the presence of the hypervascular peri-lesional halo. D) CECT (left) and CEUS (right) demonstrating ablation zones that encompass the entire lesion measuring 32 by 42 mm.

Figure 2

67-year old female with liver metastasis from colorectal cancer. A) Pre-ablation magnetic resonance (MR) imaging (left) of liver lesion (arrow) and CEUS (right) confirming presence of 13 by 14 mm liver lesion (arrow) B) The lesion was treated with a single water-cooled antenna at 50 W for 6 minutes (left). Post-ablation image demonstrating hyper-echoic region measuring 34 mm by 37 mm, representing the ablation zone (right). The goal is to create ablation margins > 1 cm beyond tumor boundary. C) Post-ablation B-mode ultrasound (left) and CEUS (right) showing the ablation zone (anechoic) with the presence of the hypervascular peri-lesional halo. D) CECT (left) and CEUS (right) demonstrating ablation zones that encompass the entire lesion measuring 32 by 42 mm.

Figure 2

67-year old female with liver metastasis from colorectal cancer. A) Pre-ablation magnetic resonance (MR) imaging (left) of liver lesion (arrow) and CEUS (right) confirming presence of 13 by 14 mm liver lesion (arrow) B) The lesion was treated with a single water-cooled antenna at 50 W for 6 minutes (left). Post-ablation image demonstrating hyper-echoic region measuring 34 mm by 37 mm, representing the ablation zone (right). The goal is to create ablation margins > 1 cm beyond tumor boundary. C) Post-ablation B-mode ultrasound (left) and CEUS (right) showing the ablation zone (anechoic) with the presence of the hypervascular peri-lesional halo. D) CECT (left) and CEUS (right) demonstrating ablation zones that encompass the entire lesion measuring 32 by 42 mm.

Figure 3

79-year old male with a history of cirrhosis and hepatitis C and prior treatment with surgery and radiofrequency ablation for HCC. A) CECT (left) and CEUS (right) image demonstrating an arterially-enhanced liver lesion (yellow arrows). B) Ultrasound image showing single gas cooled-antenna (arrowhead) being guided into the HCC (left) and after being treated at 50 W for 5 minutes (right). This ultrasound image shows progression of treatment via rapid generation of gas inside the liver tissue (arrow). C) On post-procedural B-mode (left) and CEUS (right) (24-hour post-ablation), the image shows presence of central hypo-echoic area corresponding to the lesion treated, surrounded by a hyper-echoic area which corresponds to the inflammatory region of the ablation zone. D) 24-hour post-ablation arterial phase CECT (left) and portal-venous phase CECT (right) showing ablation zone encompassing the lesion (arrows).

Figure 3

79-year old male with a history of cirrhosis and hepatitis C and prior treatment with surgery and radiofrequency ablation for HCC. A) CECT (left) and CEUS (right) image demonstrating an arterially-enhanced liver lesion (yellow arrows). B) Ultrasound image showing single gas cooled-antenna (arrowhead) being guided into the HCC (left) and after being treated at 50 W for 5 minutes (right). This ultrasound image shows progression of treatment via rapid generation of gas inside the liver tissue (arrow). C) On post-procedural B-mode (left) and CEUS (right) (24-hour post-ablation), the image shows presence of central hypo-echoic area corresponding to the lesion treated, surrounded by a hyper-echoic area which corresponds to the inflammatory region of the ablation zone. D) 24-hour post-ablation arterial phase CECT (left) and portal-venous phase CECT (right) showing ablation zone encompassing the lesion (arrows).

Figure 3

79-year old male with a history of cirrhosis and hepatitis C and prior treatment with surgery and radiofrequency ablation for HCC. A) CECT (left) and CEUS (right) image demonstrating an arterially-enhanced liver lesion (yellow arrows). B) Ultrasound image showing single gas cooled-antenna (arrowhead) being guided into the HCC (left) and after being treated at 50 W for 5 minutes (right). This ultrasound image shows progression of treatment via rapid generation of gas inside the liver tissue (arrow). C) On post-procedural B-mode (left) and CEUS (right) (24-hour post-ablation), the image shows presence of central hypo-echoic area corresponding to the lesion treated, surrounded by a hyper-echoic area which corresponds to the inflammatory region of the ablation zone. D) 24-hour post-ablation arterial phase CECT (left) and portal-venous phase CECT (right) showing ablation zone encompassing the lesion (arrows).

Figure 3

79-year old male with a history of cirrhosis and hepatitis C and prior treatment with surgery and radiofrequency ablation for HCC. A) CECT (left) and CEUS (right) image demonstrating an arterially-enhanced liver lesion (yellow arrows). B) Ultrasound image showing single gas cooled-antenna (arrowhead) being guided into the HCC (left) and after being treated at 50 W for 5 minutes (right). This ultrasound image shows progression of treatment via rapid generation of gas inside the liver tissue (arrow). C) On post-procedural B-mode (left) and CEUS (right) (24-hour post-ablation), the image shows presence of central hypo-echoic area corresponding to the lesion treated, surrounded by a hyper-echoic area which corresponds to the inflammatory region of the ablation zone. D) 24-hour post-ablation arterial phase CECT (left) and portal-venous phase CECT (right) showing ablation zone encompassing the lesion (arrows).