Blade Oblique Cutting of Tissue for Investigation of Biopsy Needle Insertion

Needle biopsy is a common medical procedure where a needle is guided into the body and used to cut and remove tissue for evaluation. The geometry of needle tip and speed of insertion are important to the efficiency of tissue cutting. This study investigates the mathematical model on the needle tip cutting edge, which is divided into several elementary cutting tools (ECT). The cutting edge is modeled as ECTs with constant inclination angle (). A blade oblique cutting machine was developed to test the cutting of bovine liver and phantom gel work-materials by inserting a thin sharp blade at different inclination angles. Experimentations performed reveals phenomena associated with cutting of soft tissue and tissue-like materials. Increased speeds and decreased inclination angles lead to higher cutting forces. This study also reveals that it is challenging to determine the exact location for the inception of blade cutting of soft tissue due to the large workpiece deformation. INTRODUCTION Biopsy is a common medical procedure where tissue is cut and removed from a specific location so that a pathologist can make an examination to detect abnormalities, such as cancer. Needle biopsy is a specific biopsy procedure where a needle and stylet (inner part of needle), as shown in Figure 1, is used to perform the biopsy operation. Needle biopsy only requires a very small incision, making it a minimally invasive procedure and therefore preferred over other biopsy techniques. The emergence of early detection methods for cancer has increased the frequency of needle biopsy procedure. For example, in detecting prostate cancer, the most common cancer in men, the prostate specific antigen (PSA) level in the blood can be easily tested. If the PSA level is greater than 10 ng/ml, a needle biopsy is performed to confirm the presence of cancer. Efficient tissue cutting in biopsy greatly affects the accuracy of the diagnosis and comfort to the patients. Carl S. McGill Department of Biomedical Engineering University of Michigan Ann Arbor, Michigan