Aim: Needle visibility is crucial for effective and safe ultrasound-guided interventional procedures. Several studies have investigated needle visibility in 2D ultrasound imaging, but less information is available for 3D ultrasound imaging, a modality that has great potential for image guidance interventions. We performed a prospective study, to quantitatively compare the echogenicity of various commercially available needles in 3D ultrasound images used in clinical practice under freehand needle introduction.
Materials and methods: A set of seven needles, containing biopsy needles, a TIPS needle, an ablation needle and a puncture needle, were included in the study. A liver-mimicking phantom and cow liver were punctured by each needle. 3D sweeps and real-time 3D data were acquired at three different angles (20°, 55° and 90°). Needle visibility was quantified by calculating contrast-to-noise ratio.
Results: In the liver-mimicking phantom, all needles showed better visibility than in the cow liver. At large angles, contrast-to-noise ratio and needle visibility were almost similar in both cases, but at lower angles differences in visibility were observed with different types of needles.
Conclusion: The contrast-to-noise ratio increased with the increase in angle of insonation. The difference in visibility of different needles is more pronounced at 20° angle. The echogenic properties of inhomogeneous cow liver tissues make the needles visibility worse as compared to a homogenous phantom. The needle visibility becomes worse in 3D real-time data as compared to 3D ultrasound sweeps.
Keywords: Contrast-to-noise-ratio (CNR); Image guidance; Needle tip; Ultrasound; Visibility.