High-intensity focused ultrasound treatment of liver tumours: post-treatment MRI correlates well with intra-operative estimates of treatment volume

Abstract

Objectives: To assess the safety and feasibility of high-intensity focused ultrasound (HIFU) ablation of liver tumours and to determine whether post-operative MRI correlates with intra-operative imaging.

Methods: 31 patients were recruited into two ethically approved clinical trials (median age 64; mean BMI 26 kg m(-2)). Patients with liver tumours (primary or metastatic) underwent a single HIFU treatment monitored using intra-operative B-mode ultrasound. Follow-up consisted of radiology and histology (surgical trial) or radiology alone (radiology trial). Radiological follow-up was digital subtraction contrast-enhanced MRI.

Results: Treatment according to protocol was possible in 30 of 31 patients. One treatment was abandoned because of equipment failure. Transient pain and superficial skin burns were seen in 81% (25/31) and 39% (12/31) of patients, respectively. One moderate skin burn occurred. One patient died prior to radiological follow-up. Radiological evidence of ablation was seen in 93% (27/29) of patients. Ablation accuracy was good in 89% (24/27) of patients. In three patients the zone of ablation lay ≤2 mm outside the tumour. The median cross-sectional area (CSA) of the zone of ablation was 5.0 and 5.1 cm(2) using intra-operative and post-operative imaging, respectively. The mean MRI:B-mode CSA ratio was 1.57 [95% confidence interval (CI)=0.57-2.71]. There was positive correlation between MRI and B-mode CSA (Spearman's r=0.48; 95% CI 0.11-0.73; p=0.011) and the slope of linear regression was significantly non-zero (1.23; 95% CI=0.68-1.77; p<0.0001).

Conclusions: HIFU ablation of liver tumours is safe and feasible. HIFU treatment is accurate, and intra-operative assessment of treatment provides an accurate measure of the zone of ablation and correlates well with MRI follow-up.

Figure 1

Patient under general anaesthesia positioned prone on high-intensity focused ultrasound treatment table. The therapeutic head is below the table. Padded slings are used to suspend the patient over the water reservoir.

Figure 2

Scatter plot of estimated cross-sectional area (CSA) of ablation zone against MRI-calculated CSA of ablation zone (Spearman's coefficient=0.48; slope of linear regression 1.27, 95% confidence interval 0.68–1.77).

Figure 3

Axial T₁ weighted contrast-enhanced MRI scans taken 1 min after intravenous infusion of gadolinium-containing contrast medium. Metastatic carcinoma of the lung to the right lobe of the liver (a) before high-intensity focused ultrasound (HIFU) and (b) 12 days after HIFU, showing lack of contrast uptake within the targeted tumour (arrow) at the site of ablation

Figure 4

Metastatic carcinoma of the pancreas to the right lobe of the liver (segment V) (a) before high-intensity focused ultrasound (HIFU) and (b) 12 days after HIFU. Scanning protocol as in Figure 3.

Figure 5

Hepatocellular carcinoma within the right lobe of the liver (a) before high-intensity focused ultrasound (HIFV) treatment and (b) 12 days after HIFV. Arrow demonstrates the zone of ablation on MRI.

Figure 6

Positive technical success of high-intensity focused ultrasound (HIFU) liver treatment indicated by comparison between (a) pre-HIFU and (b) immediately post-HIFU microbubble contrast-enhanced ultrasound showing area of ablated tumour.