A new method for evaluating the normal rake angle and inclination angle on medical needles

Area of Science:

• Biomedical Engineering
• Medical Device Design
• Geometric Analysis

Background:

• Hollow needles are essential medical tools, with their effectiveness depending on precise tip geometry.
• Accurate calculation of needle cutting angles, particularly on complex surfaces, presents a significant challenge in current designs.

Purpose of the Study:

• To propose and validate a new analytical method for biopsy needle tip geometry using non-Euclidean geometry.
• To simplify the calculation of cutting angles for various hollow needle designs.

Main Methods:

• Development of a novel method based on non-Euclidean geometry for analyzing needle tip geometry.
• Application of the method to calculate normal rake angle and inclination angle for four distinct needle types: bias bevel, cylinder surface, curved surface, and Cournand-type needles.

Main Results:

• The proposed non-Euclidean geometry method simplifies and enhances the convenience of calculating cutting angles, particularly for curved surface needles.
• Analysis of Cournand-type needles showed that a smaller bevel angle correlates with higher normal rake and inclination angles.
• The range of the normal rake angle initially increased and subsequently decreased as the bevel angle increased.

Conclusions:

• The non-Euclidean geometry approach offers a practical and efficient solution for analyzing biopsy needle tip geometry and cutting angles.
• This method provides valuable insights into the relationship between needle tip design parameters (e.g., bevel angle) and cutting angle characteristics, crucial for optimizing medical procedures.