Dual-energy CT significantly improved the conspicuity of the ischemic bowel compared with conventional CT by increasing attenuation differences between ischemic and perfused segments on low-kiloelectron volt and iodine material density images.
Purpose
The goal of this study was to evaluate and model the risk of in-vivo thrombosis in each hepatic vessel type during hepatic microwave ablation as a function of vessel diameter, velocity and vessel-antenna spacing.
Materials and Methods
A single microwave ablation antenna was inserted into a single porcine lobe (n=15 total) adjacent to a hepatic artery, hepatic vein, or portal vein branch. Conventional and Doppler ultrasound were used to measure the vessel diameter, blood flow velocity, and vessel-antenna spacing. A microwave ablation zone was then created at 100 W for 5 minutes. Thrombus formation was evaluated on immediate post-procedure ultrasound imaging. Logistic regression was used to evaluate the predictive value of vessel diameter, blood flow velocity and vessel-antenna spacing on vascular thrombosis.
Results
Thrombosis was identified in 53% of portal veins, 13% of hepatic veins and 0% of the hepatic arteries. The average peak blood flow rate of the hepatic artery was significantly greater than that of the hepatic vein and portal vein. Peak blood flow velocities less than 12.45 cm/sec, vessel diameters less than 5.10 mm and vessel-antenna spacings less than 3.75 mm were strong predictors of hepatic vein thrombosis. However, these individual factors were not predictive of the more common portal vein thrombosis.
Conclusions
Hepatic arteries do not appear to be at risk for thrombosis during microwave ablation procedures. Portal vein thrombosis was more common than hepatic vein thrombosis during microwave ablation treatments, but was not as predictable based upon vessel diameter, flow velocities, or vessel-antenna spacing alone.
Purpose: The goal of this study was to compare intra-procedural radiofrequency (RF) and microwave ablation appearance on non-contrast CT (NCCT) and ultrasound to the zone of pathologic necrosis. Materials and methods: Twenty-one 5-min ablations were performed in vivo in swine liver with (1) microwave at 140 W, (2) microwave at 70 W, or (3) RF at 200 W (n ¼ 7 each). CT and US images were obtained simultaneously at 1, 3, and 5 min during ablation and 2, 5, and 10 min post-ablation. Each ablation was sectioned in the plane of the ultrasound image and underwent vital staining to delineate cellular necrosis. CT was reformatted to the same plane as the ultrasound transducer and transverse diameters of gas and hypoechoic/hypoattenuating zones at each time point were measured. CT, ultrasound and gross pathologic diameter measurements were compared using Student's t-tests and linear regression. Results: Visible gas and the hypoechoic zone on US images were more predictive of the pathologic ablation zone than on NCCT images (p < 0.05). The zone of necrosis was larger than the zone of visible gas on US (mean 3.2 mm for microwave, 6.4 mm for RF) and NCCT (7.6 mm microwave, 13.9 mm RF) images (p < 0.05). The zone of visible gas and hypoechoic zone on US are more predictive of pathology with microwave ablations when compared with RF ablations (p < 0.05). Conclusion: When evaluating images during energy delivery, US is more accurate than CT and microwave-more predictable than RF-ablation based on correlation with in-plane pathology.
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