Soft Tissue Cutting in Core Biopsy

Giovannini, Marco

doi:https://doi.org/10.21985/n2-gw4k-0s51

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Soft Tissue Cutting in Core Biopsy

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Hollow biopsy needles are widely adopted medical devices for the removal of biological tissue to better identify a lesion or an abnormality observed through a physical exam or a radiology scan. These procedures can provide significantly more information than most medical tests, and they are usually performed on dermis layers, bone lesions, breast masses, lymph nodes, and the prostate. The quality of the samples mainly depends on the forces exerted by the needle during the cutting process. The reduction of these forces is critical to extract high-quality tissue samples. The most important factors that affect the cutting forces are the geometry of the needle tip and its motion while it is penetrating the tissue. However, optimal needle tip configurations and cutting parameters are not well established for biopsy procedures. This thesis, articulated in four topics, aims to investigate the geometry and cutting forces of biopsy needles. First, analytical models related to the cutting angles of several needle tip designs are presented and compared. Several needle tip geometries were ground and tested on different phantom tissues at different speeds. Second, novel three-dimensional (3D) needle geometries were conceived, and mathematical models were formulated to compute the cutting angles and tissue fracture forces. The proposed methodology was demonstrated on helical needles, which were then manufactured and tested on soft tissue. Third, the characterization of polyvinyl chloride (PVC) tissue, which is commonly used to mimic human skin, was performed by means of uniaxial tests. Data coming from tissue characterization were used to calibrate a 3D FEM model to predict the cutting force during the insertion of core biopsy needles. Fourth, the application of bio-inspired micro-serrated cutting edges on the cutting edge of hollow needles was considered. Micro-serrations were created by adopting laser micro-machining, and their effectiveness was verified through the development of analytical and computational models. The outcome of this study can benefit several clinical procedures, especially core and skin biopsy, in which a cannula device is adopted to cut and collect soft tissue samples.

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