Non-contact ultrasonic inspection of medical catheters for polymeric bond defects

A non-contact, laser-optic based laser ultrasonic technique referred to as the thermo-acousto-photonic non-destructive evaluation (TAP-NDE) was employed to investigate bond integrity and localized stiffening due to an attached wire stent on small diameter polymeric catheters. Laser-generated interrogating ultrasonic dispersive waves in the catheter were acquired using a fiber-tip interferometer (FTI) running on a HeNe laser. The basic notions of zero-crossing rate and artificial neural network (ANN) were applied to digitized tubular guided-waves to uniquely identify each of the following three bond defects: tensile pull, needle puncture, and crease. These induced flaws represent possible manufacturing defects such as de-bond, potential leak sources, and geometry irregularities. Zero-crossing rates were also found to uniquely identify localized stiffening due to an attached wire stent proving that this technique can unambiguously identify propagation modes from among non-propagation modes or vibrations. The 100% success rate reported in the paper renders the utility of TAP-NDE, along with ANN based classification scheme using zero-crossing rates, a viable quantitative measure for inspecting small-diameter polymeric medical tubing for sub-mm defects in real-time.