Figure 2
From: Steerable needles for radio-frequency ablation in cirrhotic livers
Image of the experimental platform (A), showing the interventional radiologist (1), RFA probe (2), steerable needle v1 (3), and PVA phantom (4), with a trocar bridge to control the insertion location, needle alignment and steering task. The ultrasound probe (5) is manually controlled to visualise insertions on-screen (6). Typically, radiologists pressed the probe to the side of the PVA specimens, yielding an orthogonal view (B). Ultrasound images were stored and processed, using a region of interest (ROI) and Hough transforms to estimate target, needle and tip locations (C). Tip placement errors for straight and curved paths are shown by boxplots and individual data points (D). The asterisk indicates a Wilcoxon rank sum test difference (α = 0.05). Errors after manual path correction steps are visualised in orange. The red line indicates an acceptance threshold error of 2.7 mm, which was the mean position error accepted by a group of 125 interventional radiologist4.
