Figure 5:

US (top) vs. CT (bottom) intra-procedure images of RF ablation at each point of image recording in the experiment. Note how the zone of visible gas is most pronounced at 1 and 3 minutes (yellow arrow) with minimal visible gas 5 minutes into the ablation. Similarly, gas is most notable at 1 and 3 minutes on CT (red arrows) with more dissipated gas at 5 minutes. A hypoechoic zone is noted at 3 and 5 minutes on the ultrasound (blue arrows), while the hypodense zone at CT is difficult to visualize.