A Novel Biopsy Needle with Double Concave-Curved Cutting Edges

Background: Vacuum-assisted biopsy is a minimally invasive sampling technique that relies on rotational cutting as a major tissue retrieving method. A precise diagnosis of the disease requires large, uncrushed samples, which are impacted by the cutting force of the biopsy needle. Objectives: This study proposes a novel needle design with double-concave-curved cutting edges, which is more suited for rotational needle cutting. We aimed to optimize the design so that large, undamaged samples could be extracted with minimal cutting force. Materials and Methods: Five-factor experiments were designed using the Taguchi method. Experiments involving rotational needle insertion and tissue sampling were conducted to examine the effects of these variables on the cutting force and sampling quality, respectively. The relationship between the cutting force and sampling quality was analyzed. Results: For needle insertion, the optimal design within the design space demonstrated a marked improvement in cutting force from 1.2107 to 0.1888 N. Furthermore, the optimized double concave-curved needle outperformed the blunt needle under the same needle speeds, showing a 24.4% reduction in cutting force (0.1888 vs. 0.2496 N). Increasing rotation-translation ratio or insertion speed would allow for extracting a larger sample (increased up to 21.95% in weight and 17.21% in total length) but may also increase the rotation speed, resulting in sample fragmentation. To simultaneously improve sampling quality and cutting force, a higher K value, larger rotation-translation ratio, and slower insertion speed are suggested. Based on the conditions examined in this study, the optimal needle configuration should include a sharpened cutting edge with a K value of 0.2, a rotation-translation ratio of 8, and an insertion speed of 1 mm/s.