Dynamic Contrast-Enhanced MR Imaging Evaluation of Perfusional Changes and Ablation Zone Size after Combination Embolization and Ablation Therapy.

PURPOSE: The objectives of this study were to assess the utility of dynamic contrast-enhanced magnetic resonance (MR) imaging in quantifying parenchymal perfusional changes after embolization and to characterize the association between pharmacokinetic (PK) parameters and final microwave ablation volume. MATERIALS AND METHODS: PK parameters from dynamic contrast-enhanced MR imaging were used to quantify perfusional changes in the liver after transarterial embolization of the right or left lobe in a swine liver model (n = 5). Each animal subject subsequently underwent microwave ablation (60 W for 5 minutes) of the embolized and nonembolized liver lobes. Changes in PK parameters from dynamic contrast-enhanced MR imaging were correlated with their respective final microwave ablation volumes in each liver lobe. RESULTS: Microwave ablation volumes of embolized liver lobes were significantly larger than those of nonembolized liver lobes (28.0 mL ± 6.2 vs 15.1 mL ± 5.2, P < .001). PK perfusion parameters were significantly lower in embolized liver lobes than in nonembolized liver lobes (Ktrans = 0.69 min-1 ± 0.15 vs 1.52 min-1 ± 0.37, P < .001; kep = 0.69 min-1 ± 0.19 vs 1.54 min-1 ± 0.42, P < .001). There was a moderate but significant correlation between normalized kep and ablation volume, with each unit increase in normalized kep corresponding to a 9.8-mL decrease in ablation volume (P = .035). CONCLUSIONS: PK-derived parameters from dynamic contrast-enhanced MR imaging can be used to quantify perfusional changes after transarterial embolization and are directly inversely correlated with final ablation volume.

4D Flow MR Imaging to Improve Microwave Ablation Prediction Models: A Feasibility Study in an In Vivo Porcine Liver.

PURPOSE: To characterize the effect of hepatic vessel flow using 4-dimensional (4D) flow magnetic resonance (MR) imaging and correlate their effect on microwave ablation volumes in an in vivo non-cirrhotic porcine liver model. MATERIALS AND METHODS: Microwave ablation antennas were placed under ultrasound guidance in each liver lobe of swine (n = 3 in each animal) for a total of 9 ablations. Pre- and post-ablation 4D flow MR imaging was acquired to quantify flow changes in the hepatic vasculature. Flow measurements, along with encompassed vessel size and vessel-antenna spacing, were then correlated with final ablation volume from segmented MR images. RESULTS: The linear regression model demonstrated that the preablation measurement of encompassed hepatic vein size (ß = -0.80 ± 0.25, 95% confidence interval [CI] -1.15 to -0.22; P = .02) was significantly correlated to final ablation zone volume. The addition of hepatic vein flow rate found via 4D flow MRI (ß = -0.83 ± 0.65, 95% CI -2.50 to 0.84; P = .26), and distance from antenna to hepatic vein (ß = 0.26 ± 0.26, 95% CI -0.40 to 0.92; P = .36) improved the model accuracy but not significantly so (multivariate adjusted R2 = 0.70 vs univariate (vessel size) adjusted R2 = 0.63, P = .24). CONCLUSIONS: Hepatic vein size in an encompassed ablation zone was found to be significantly correlated with final ablation zone volume. Although the univariate 4D flow MR imaging-acquired measurements alone were not found to be statistically significant, its addition to hepatic vein size improved the accuracy of the ablation volume regression model. Pre-ablation 4D flow MR imaging of the liver may assist in prospectively optimizing thermal ablation treatment.

Microwaves create larger ablations than radiofrequency when controlled for power in ex vivo tissue.

PURPOSE: To compare ablation zones created with equal amounts of 2.45 GHz microwave and 480 kHz radiofrequency (RF) energy in ex vivo liver and lung. METHODS: A total of 38 ablations were performed in ex vivo liver and lung for 10 min each. Nineteen RF ablations (nine liver, ten lung) were performed with a 480 kHz system (200 W max, impedance-based pulsing) and cooled electrode while measuring the average RF power applied. Nineteen microwave ablations (nine liver, ten lung) were then created using a cooled triaxial antenna to deliver 2.45 GHz at the same power level as in RF experiments. Ablation zones were then sectioned and measured for minimum, maximum and mean diameters, and circularity. Measurements were compared using t-tests, with P < 0.05 indicating statistical significance. RESULTS: Mean diameters of microwave ablations were greater than RF ablations in both liver and lung (4.4 +/- 0.3 vs 3.3 +/- 0.2 cm in liver; 2.45 +/- 0.3 vs 1.6 +/- 0.5 cm in lungs; P < 0.0005 all comparisons). There was no significant difference in the mean power applied during microwave or RF ablations in either organ (54.44 +/- 1.71 W vs 56.4 +/- 6.7 W in liver, P > 0.05; 40 +/- 0.95 W vs 44.9 +/- 7.1 W in lung, P > 0.05). CONCLUSIONS: Using a single cooled applicator, microwave energy at 2.45 GHz produces larger ablations than an equivalent amount of 480 kHz RF energy in normal liver and lung. This was more apparent in lung, likely due to the high baseline impedance which limits RF, but not microwave power delivery.

Colonic perforation and abscess following radiofrequency ablation treatment of hepatoma.

OBJECTIVE: Radiofrequency (RF) has been demonstrated as a relatively safe procedure in the treatment of hepatocellular carcinoma (HCC). METHODS: A 60-year-old man with liver cirrhosis presented with a large, infiltrating HCC close to the right colon. The patient was treated with internally cooled RF. RESULTS: On the 8th day post-ablation, a complication of right colon perforation was diagnosed. CONCLUSION: RF can induce untoward thermal damage, and may not be indicated in large infiltrating lesions abutting the gastrointestinal tract.

Treatment of focal liver tumors with percutaneous radio-frequency ablation: complications encountered in a multicenter study.

PURPOSE: To report complications encountered by members of a collaborative group who performed radio-frequency (RF) ablation in patients with focal liver cancer. MATERIALS AND METHODS: Members of 41 Italian centers that were part of a collaborative group used a percutaneous internally cooled RF ablation technique and a standardized protocol for follow-up. They completed a questionnaire regarding number of deaths, presumed cause of death, and likelihood of its relationship to the RF procedure; number and types of major complications; and types of minor complications and side effects. Enrollment included 2,320 patients with 3,554 lesions (size, 3.1 cm +/- 1.1 [SD] in diameter): 1,610 had hepatocellular carcinoma with chronic liver disease; 693 had metastases, predominantly from colorectal cancer (n = 501); and 17 had cholangiocellular carcinoma. Number and characteristics of complications (ie, deaths and major and minor complications) attributed to the procedure were reported. Data were subsequently analyzed with analysis of variance to determine whether the major complication rate was related to tumor size, number of ablation sessions, or electrode type (single or cluster). RESULTS: In total, 3,554 lesions were treated. Six deaths (0.3%) were noted, including two caused by multiorgan failure following intestinal perforation; one case each of septic shock following Staphylococcus aureus-caused peritonitis, massive hemorrhage following tumor rupture, liver failure following stenosis of right bile duct; and one case of sudden death of unknown cause 3 days after the procedure. Fifty (2.2%) patients had additional major complications. The most frequent of these were peritoneal hemorrhage, neoplastic seeding, intrahepatic abscesses, and intestinal perforation. An increased number of RF sessions were related to a higher rate of major complications (P <.01), whereas the number of complications was not significantly different when tumor size or electrode type were compared. Minor complications were observed in less than 5% of patients. CONCLUSION: Results of this study confirm that RF ablation is a relatively low-risk procedure for the treatment of focal liver tumors.