Development of a miniaturized low-frequency transducer for accurate placement of screw implants in the spine

Many spinal fusion procedures require the insertion of screws through the pedicles into the vertebral bodies. The existing methods (C-arm fluoroscopy, CT imaging navigation, O-arm navigation) imaged the pedicle from the outside, which are always interfered by environmental and equipment factors. Ultrasound navigation in channel may be a potential method to avoid improper pedicle screw placement. It is reported in the literature that low-frequency (1-3MHz) ultrasound can achieve sufficient penetration depth and resolution in the bone, but the elements were too large to fit into the pedicle's bore hole. The purpose of the study was to develop a miniaturized low-frequency transducer for accurate placement of pedicle screws in the spine, and two designed methods for low frequency miniaturized transducer were modeled, fabricated, characterized and evaluated.