Needle-tip localization using an optical fibre hydrophone

Ultrasound imaging is frequently used for guiding needles during minimally invasive procedures, but accurate identification of the needle tips can be challenging, even for experienced practitioners. In this study, a novel method for tracking needles inside the human body was developed. This method, called ultrasonic device tracking (UDT), involved the detection of ultrasound pulses from the external imaging probe with an optical fibre hydrophone integrated into the needle cannula. Two methods for estimating the needle tip position that were based on the maximum and the centroid of the optical fibre hydrophone signal were tested. The variability of the position estimates is measured at different distances to the electronic focus. The maximum longitudinal variability was less than 80 μm for all distances. The lateral variability remains below 500 μm in a 20 mm region around the focus, but increases up to several mm away from the electronic focus. In the close proximity of the electronic focus, the lateral and longitudinal variability lower down to 22 μm and less. This study suggests that UDT allows for safer and more efficient procedures in a manner that is compatible with the current clinical workflow.