Bevel angle study of flexible hollow needle insertion into biological mimetic soft-gel: Simulation and experimental validation

Background: A thorough understanding of cutting-edge geometry and cutting forces of hollow biopsy needles are required to optimise needle tip design to improve fine needle aspiration procedures. Objectives: To incorporate the dynamics of needle motion in a model for flexible hollow bevel tipped needle insertion into a biological mimetic soft-gel using parameters obtained from experimental work. Additionally, the models will be verified against corresponding needle insertion experiments. Methods: To verify simulation results, needle deflection and insertion forces were compared with corresponding experimental results acquired with an in-house developed needle insertion mechanical system. Additionally, contact stress distribution on needles from agar gel for various time scales were also studied. Results: For the 15°, 30°, 45°, 60° bevel angle needles, and 90° blunt needle, the percentage error in needle deflection of each needle compared to experiments, were 7.3%, 9.9%, 8.6%, 7.8%, and 9.7% respectively. Varying the bevel angle at the needle tip demonstrates that the needle with a lower bevel angle produces the largest deflection, although the insertion force does not vary too much among the tested bevel angles. Conclusion: This experimentally verified computer-based simulation model could be used as an alternative tool for better understanding the needle-tissue interaction to optimise needle tip design towards improved biopsy efficiency.