Audio waves and its loss of energy in puncture needles

Abstract

The location of a puncture needle’s tip and the resistance of tissue against puncture are crucial information for clinicians during a percutaneous procedure. The tip location and needle alignment can be observed by image guidance. Tactile information caused by tissue resistance to rupture, allow clinicians the perception of structural changes during puncture. Nevertheless, this sense is individual and subjective. To improve percutaneous procedures, the implementation of transducers to enhance or complement the senses offer objective feedback to the user. Known approaches are e.g. based on integrated force sensors. However, this is connected to higher device costs, sterilization and certification issues. A recent publication shows the implementation of an audio transducer clipped at the proximal end of the needle. This sensor is capable of acquiring emitted sounds of the distal tiptissue interaction that are transmitted over the needle structure. The interpretation of the measured audio signals is highly depended on the transmission over the needle, the tissue and, the penetration depth. To evaluate the influence of these parameters, this work implements a simplified experimental setup in a controlled environment with a minimum of noise and without micro tremors induced by clinician’s hands. A steel rod simulating a needle is inserted into pork meat of different thickness. A controlled impact covering the needle’s tip mimics tissue contact. The resulting signals are recorded and analyzed for better understanding of the system.

Acoustic signal analysis of instrument–tissue interaction for minimally invasive interventions

“…They showed that the method allows to identify transitions between different types of tissues during needle insertion. This concept was applied in further research in an experimental setup to analyze the influence of different insertion depths and the interaction of the surrounding soft tissue with the needle surface to the resulting measurements [16]. Moreover, the tissue-layer crossing identification capabilities of the system were successfully tested with the application of Veress needle placement for minimally invasive interventions [28].…”