Compliant joint echogenicity in ultrasound images: towards highly visible steerable needles

Radio frequency ablation is commonly used in the treatment of hepatocellular carcinoma. Clinicians rely on imaging techniques, such as medical ultrasound, to confirm an accurate needle placement. This accuracy may improve by means of active needle steering techniques, which are currently in development. Needle steering will likely increase the clinician’s reliance on imaging techniques. This has motivated the study of the echogenicity of steerable needle joint structures. Two needles were manufactured with arrays of kerfs, similar to the compliant joint structures found in steerable needles. The needle visibility was compared to a smooth surface needle and a commercially available RFA needle. The visibility was quantified for both the shaft and tip, by means of a contrast-to-noise ratio (CNR). CNR data were obtained for three insertion angles. The results show that the CNRs of the compliant joint structures were consistently higher than those of the smooth surface needle, whereas they were either higher than or comparable to those of the RFA needle. For acute insertion angles, the bevel tip of the RFA needle had a higher CNR than the conical tip of the kerfed needles, motivating the extension of this visibility study to the full needle design.