Background & Aims: Measurements of α-fetoprotein (AFP) detect hepatocellular carcinoma (HCC) with low levels of sensitivity and specificity, and are therefore not recommended for use in liver cancer surveillance. However, AFP levels might accurately detect HCC in subgroups of patients. We performed a retrospective case–control study to identify features of patients with cirrhosis in whom levels of AFP correlated with HCC. Methods: We collected data from patients with cirrhosis, with HCC (n=452) or without (n=676), diagnosed at Parkland Hospital in Dallas, Texas from January 2005 through June 2012. We determined sensitivities and specificities with which different levels of AFP identified those with HCC; multivariate logistic regression was used to associate accurate identification of HCC with patient features (age, sex, race/ethnicity, alcohol intake, smoking, etiology of cirrhosis, presence of decompensation, and laboratory test results). We assessed overall accuracy of these factors in detecting HCC using receiver operator characteristic (ROC) curve analysis and the Delong method. We calculated levels of AFP that detect HCC with the highest levels of sensitivity and specificity in subgroups using ROC analysis. Results: The most common etiologies of cirrhosis hepatitis C virus (HCV) infection (60%) and alcohol induced (22%). Nearly 11% of patients were HIV-positive. Levels of AFP >20 ng/mL detected HCC with 70.1% sensitivity and 89.8% specificity. This AFP level identified patients with HCC with a c-statistic of 0.87 (95% confidence interval, 0.85–0.89); it was significantly more accurate in HCV-negative patients than HCV-positive patients (c-statistic 0.89 vs 0.83; P=.007). AFP levels ≥59 ng/mL most accurately detected HCC in patients with HCV-associated cirrhosis; levels of AFP ≥11 ng/mL accurately identified HCC in HCV-negative patients. Level of AFP identified early-stage HCC with a c-statistic of 0.62 (95% confidence interval, 0.58–0.66), and had a significantly higher level of accuracy for HIV-positive patients than HIV-negative patients (c-statistic 0.81 vs 0.59; P<.001). Conclusion: Based on retrospective analysis of data from patients with cirrhosis, with or without HCC, level of AFP most accurately detects HCC in patients without HCV infection. It detects HCC with a high level of accuracy in patients with cirrhosis and HIV infection.

Thermal ablation is increasingly utilized in the treatment of primary and metastatic liver tumors, both as curative therapy and as a bridge to transplantation. Recent advances in high-powered microwave ablation systems have allowed physicians to realize 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 optimize patient care when using microwave ablation systems.

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Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

Purpose:To characterize vessel occlusion rates and their role in local tumor progression in patients with hepatocellular carcinoma (HCC) who underwent microwave tumor ablation. Materials and Methods:This Results:Occlusion was identified in 39.7% of portal veins (29 of 73), 15.0% of hepatic veins (six of 40), and 14.2% of hepatic arteries (10 of 70) encompassed within the ablation zone. Hepatic vein occlusion was significantly correlated with a smaller vessel size (P = .036) and vessel-antenna spacing (P = .006). Portal vein occlusion was only significantly correlated with a smaller vessel size (P = .001), particularly in vessels that were less than 3 mm in diameter. Local tumor progression rates were significantly correlated with patent hepatic arteries within the ablation zone (P = .02) but not with patent hepatic (P = .57) or portal (P = .14) veins. Conclusion:During microwave ablation of HCC, hepatic veins and arteries were resistant to vessel occlusion compared with portal veins, and only arterial patency within an ablation zone was related to local tumor progression.q RSNA, 2016

Purpose: The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models. Methods: A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5-20 mm from the ablation antenna, with values over 60• C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post-hoc pairwise tests. Results: No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm 3 ). At 25 W average, pulsed-power ablation volumes were larger than continuous-power ablations (67.4 ± 34.5 cm 3 versus 23.6 ± 26.5 cm 3 , P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and pulsed ablations were again slightly more circular. Conclusions: Pulsed energy delivery created larger ablation zones at low average power compared to continuous energy delivery in the presence of blood perfusion. Shorter duty cycles appear to provide greater benefit when pulsing. C

Purpose:To compare the performance of a microwave antenna design with two annular slots to that of a monopole antenna design in creating a more spherical ablation zone. Materials and Methods:Animal care and use committee approval was obtained before in vivo experiments were performed. Microwave ablation zones were created by using dual-slot and monopole control antennas for 2, 5, and 10 minutes at 50 and 100 W in ex vivo bovine livers. Dual-slot and monopole antennas were then used to create ablation zones at 100 W for 5 minutes in in vivo porcine livers, which also underwent intraprocedural imaging. Ablation diameter, length, and aspect ratio (diameter 4 length) were measured at gross pathologic examination and compared at each combination of power and time by using the paired Student t test. A P value less than .05 was considered to indicate a significant difference. Aspect ratios closer to 1 reflected a more spherical ablation zone. Results:The dual-slot antenna created ablation zones with a higher aspect ratio at 50 W for 2 minutes (0.75 vs 0.53, P = .003) and 5 minutes (0.82 vs 0.63, P = .053) than did the monopole antenna in ex vivo liver tissue, although the difference was only significant at 2 minutes. At 100 W, the dual-slot antenna had a significantly higher aspect ratio at 2 minutes (0.52 vs 0.42, P = .002). In vivo studies showed significantly higher aspect ratios at 100 W for 5 minutes (0.63 vs 0.53, respectively, P = .029). Intraprocedural imaging confirmed this characterization, showing higher rates of ablation zone growth and heating primarily at the early stages of the ablation procedure when the dual-slot antenna was used. Conclusion:The dual-slot microwave antenna created a more spherical ablation zone than did the monopole antenna both in vivo and ex vivo liver tissue. Greater control over power delivery can potentially extend the advantages of the dualslot antenna design to higher power and longer treatment times.q RSNA, 2013 1

The indications for CEUS-guided biopsy for LTLs are limited, but CEUS can be useful in challenging clinical scenarios, e. g. poorly visualized or invisible lesions or sampling of non-necrotic areas in the target lesions. There is also a potential advantage in using CEUS to guide repeat biopsies after unsuccessful sampling performed using the standard ultrasound technique.