Intraductal Tissue Sampling Device Designed for the Biliary Tract

Abstract

Clinical sampling of tissue that is read by a pathologist is currently the gold standard for making a disease diagnosis, but the few minimally invasive techniques available for small duct biopsies have low sensitivity, increasing the likelihood of false negative diagnoses. We propose a novel biopsy device designed to accurately sample tissue in a biliary stricture under fluoroscopy or endoscopic guidance. The device consists of thin blades organized around the circumference of a cylinder that are deployed into a cutting annulus capable of comprehensively sampling tissue from a stricture. A parametric study of the device performance was done using finite element analysis; this includes the blade deployment under combined axial compression and torsion followed by an axial `cutting' step. The clinical feasibility of the device is determined by considering maximum deployment forces, the radial expansion achieved and the cutting stiffness. We find practical parameters for the device operation to be an overall length of 10 mm and a diameter of 3.5 mm for a 50 μm blade thickness, which allow the device to be safely deployed with a force of 10N and achieve an expansion over 3x its original diameter. A model device was fabricated with these parameters and a 75 μm thickness out of a NiTi superalloy and tested to validate the performance. The device showed strong agreement with an equivalent numerical model, reaching a peak force within 2% of that predicted numerically and fully recovering after compression to 20% of its length.

Keywords

• Biliary biopsy
• endoscopic biopsy device
• finite element analysis
• helical buckling
• NiTi
• superelastic alloy