Steerable needles for radio-frequency ablation in cirrhotic livers

Abstract

Accurate needle placement in deep-seated liver tumours can be difficult. In this work, we disclose two new manually controlled steerable needles for 17G radio-frequency ablation probe placement. The needles contain stylets with embedded compliant joints for active tip articulations, and concentric tubes for (curved-path) guidance. Needle steering was evaluated sequentially by intended users and in intended-use tissue types. Six interventional radiologists evaluated the needle in repeated ultrasound-guided steering tasks in liver-mimicking phantoms. Targets were located at a 100 mm depth and 20 mm lateral offset from the initial insertion line. The resulting mean absolute tip placement error was 1.0 ± 1.0 mm. Subsequently, steering-induced tissue damage was evaluated in fresh cirrhotic human liver explants. The surface area of puncture holes was estimated in scanned histology slides, using a connected-components analysis. The mean surface area was 0.26 ± 0.16 mm2 after steering with a median radius of curvature of 0.7 × 103 mm, versus 0.35 ± 0.15 mm2 after straight-path insertions with the steerable needle and 0.15 ± 0.09 mm2 after straight-path RFA probe insertions. The steering mechanisms proposed enable clinically relevant path corrections for 17G needles. Radiologists were quickly adept in curved-path RFA probe placement and the evaluation of histological tissue damage demonstrated a potentially safe use during liver interventions.

Axially rigid steerable needle with compliant active tip control

“…A reduction in flexural and axial rigidity of 11.8% and 20.8% is observed respectively compared to a rigid inner needle. However, the flexural rigidity of the proposed design is much higher than for the designs reported in literature [ 42 , 46 ]. Moreover, no buckling was observed in our prostate tissue mimicking and ex-vivo experiments, suggesting that the design has sufficient axial rigidity for placement of HDR BT catheters.…”

Block‐matching‐based registration to evaluate ultrasound visibility of percutaneous needles in liver‐mimicking phantoms

“…Two needles contain kerfed EDM patterns resembling compliant joints in steerable needle designs. 26 , 27 Both kerf types were of equal size (width = 0.1 mm, depth = 0.5 mm), but the second had additional beveled edges (45° × 0.2 mm), which may increase the specular reflections for a specific insertion angle range. All custom‐made needles were constructed from stainless steel (Steel), except for one, which was made from super‐elastic nitinol (Nitinol).…”

“…Three factors that are considered important determinants for needle visibility are the needle material, the surface condition,and the needle diameter.Nine needles with different characteristics (Table 1) were included in this study (Figure 1). 26,27 Both kerf types were of equal size (width = 0.1 mm, depth = 0.5 mm), but the second had additional beveled edges (45 • × 0.2 mm), which may increase the specular reflections for a specific insertion angle range. All custom-made needles were constructed from stainless steel (Steel), except for one, which was made from super-elastic nitinol (Nitinol).…”