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Session: Soft Tissue & Abdominal Organs
Session starts: Thursday 24 January, 13:30
Presentation starts: 14:00
Room: Lecture room 559

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Tonke L. de Jong ()
Sander van der Velden ()
Jenny Dankelman ()
John J. van den Dobbelsteen ()

Abstract:
Introduction: Data on needle-tissue interaction in human specimens are scarce. For example, the forces that are involved upon puncturing hepatic vessel walls are unknown. More knowledge about these forces is needed to develop high fidelity liver phantoms, which can be used in testing novel needle designs, validating robotic systems and training of medical residents. Therefore, the goal of the current study is to give insight into the needle tip forces upon insertion through hepatic vascular walls, and to provide a phantom material that mimics these forces. Methods: Small pieces of liver tissue and blood vessels, i.e. arteries, portal veins and hepatic veins, were extracted from three fresh-frozen human cadavers. In addition, four different specimens of silicone (Smooth-Sil 950) were fabricated, ranging from 0.6-1.2mm thickness, with or without a mesh fabric attached, which allows for fastening silicone with other tissue mimicking materials, such as Polyvinyl Alcohol (PVA). An 18 Gauge trocar needle was inserted through the specimens under a constant velocity (5mm/s) by means of a linear stage. Insertion forces were captured, after which the peak forces and force-position profiles were compared among the different tissue and phantom specimens. Results: A total of 231 needle force measurements were done in liver specimens. Puncturing hepatic veins (median: 2.2N, IQ range: 1.5N – 3.7N, n = 173) resulted in the highest needle forces, followed by hepatic arteries (median: 1.3N, IQ range: 1.2N – 1.8N, n = 11), and surrounding liver tissue (median: 0.4N, IQ range: 0.3N – 0.5N, n = 47). Concerning the silicone vessel specimens without the mesh fabric; a minimum thickness of 0.9 mm was needed to mimic the needle insertion forces. A thickness from 0.6mm was appropriate for the silicone specimens with mesh. Force profiles were comparable. Conclusion: Needle insertion forces into hepatic vessel walls are higher than insertions into surrounding liver tissue. This study showed that silicone blood vessel specimens with a mesh fabric attached are suitable to mimic these forces. Therefore, they can be added to current state-of-the-art liver phantoms. Furthermore, the needle force data collected in this study can have broader applicability, for instance to develop needle path planners and to design novel needles.