Tissue Cutting in Needle Biopsy.

Abstract

This research advances knowledge in needle cutting of tissue leading to the invention and validation of the enhanced cutting edge (ECE) biopsy needle. Biopsy needle tip cutting edge geometry is defined using analytical models. With these geometrical definitions a mechanistic force model is developed to predict the needle insertion force for a given needle geometry. The force model then leads to the development of the improved ECE needle tip geometry.

Needle biopsy is one of the most common medical procedures to cut and remove tissue for pathological diagnosis. Currently little study has focused on hollow needle tissue cutting. This lack of knowledge has led to the use of biopsy needles and devices that are inefficient at cutting tissue, thereby hindering the accuracy of the diagnosis, increasing the discomfort to the patient, and lengthening the procedure time. This dissertation directly fills this void in hollow needle tissue cutting knowledge to improve the yield of biopsy and advance the understanding of hollow needle tissue cutting in biopsy.

This study is conducted in four topics that build on each other to reach the ultimate goal of developing the novel ECE biopsy needle. First, analytical models of needle geometry are developed for identification of inclination angle, normal rake angle, needle tip insertion length, and needle tip area on a variety of flat plane and curved needle tips. Second, oblique tissue cutting is studied through blade and needle tissue cutting experiments and three analytical models are developed to describe tissue flow angle and needle contact length. Third, a general hollow needle insertion force model is developed to predict needle insertion force. Fourth, a novel ECE needle tip is developed based on positive geometrical characteristics discovered by the force model for cutting tissue. This ECE needle is validated against a regular style needle and shown to produce longer biopsy sample lengths.

This research aims to improve the procedure of needle biopsy through increasing fundamental knowledge in needle cutting mechanics and developing the improved needle geometry of the ECE needle. This research can lead to more accurate biopsy diagnosis, lower patient discomfort, and shorter procedure time.