A compact packaging technique for the integration of ultrasound probes in surgical needles

State-of-the-art neurosurgery intervention relies heavily on tissue imaging information taken at a pre-operative stage. The data retrieved prior to performing an opening in the patient's skull, however, may present inconsistencies with respect to the tissue position observed by the surgeon during intervention, due to both the pulsing activity of the brain and possible displacements caused by movement of the patient and the pressure difference between the external and internal environment. The consequent uncertainty during the insertion of surgical tools into the treated tissue gives rise to great interest in real-time guidance techniques. In that respect, ultrasound imaging during neurosurgery is a promising method for imaging the tissue while inserting surgical tools, as it provides high lateral resolution images. While microelectromechanical systems (MEMS) manufacturing techniques have enabled the miniaturisation of ultrasound array devices to fit needle gauges down to 2 mm inner diameter, the challenge in scaling the probes for their integration in surgical needles lies in the development of adequate interconnection techniques to interface the microscale transducer at the tip of the needle with the macroscale driving electronic circuitry. This paper presents progress towards a novel packaging scheme that involves a thin flexible printed circuit interconnection wound inside a surgical needle and connected to the probe at the tip by means of a magnetically aligned anisotropic conductive paste. This bonding technology offers higher compactness compared to conventional wire bonding, as the individual electrical connections are isolated from one another within the volume of the paste line.