Needle Tip Visibility in 3D Ultrasound Images

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. 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 (20A degrees, 55A degrees and 90A degrees). Needle visibility was quantified by calculating contrast-to-noise ratio. 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. The contrast-to-noise ratio increased with the increase in angle of insonation. The difference in visibility of different needles is more pronounced at 20A degrees 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.