A rotary trans-osseous ultrasound blood flow detection method for endoscopic application

Due to the small size and proximity to the spinal cord and vertebral artery, the cervical pedicle screw fixation procedure remains to be challenging in clinical practice. The screw misplacement has a high probability of occurrence of severe complications. How to prevent direct injury to the vertebral artery is a vital study focus in cervical spine surgery. In this work, a trans-osseous ultrasound Doppler method is proposed to explore the possibility of detecting blood flow through thin cortical bone. A miniature single-element prototype probe with a center frequency of 2.5 MHz is prepared. With the classical pulse-echo acquisition, a Spectral Power Index (SPI) algorithm based on Spectral Doppler and sliding window traversal is designed to enhance the Doppler signal intensity. In vitro and in vivo experiments were conducted to investigate the feasibility of this method. The results of in vitro experiments suggest that the anticoagulated bovine blood flowing at a mean velocity of 15 cm/s to 80 cm/s is detectable when the thickness of cortical bone is 0.7 +/- 0.1 mm. The in vivo experiment showed that the large blood vessel with a diameter of about 3 mm (radial artery) can be detected through thin cortical bone (thickness of 0.7 +/- 0.1 mm). The proposed trans-osseous Doppler method achieves artery detection through thin cortical bone, which has demonstrated the possibility of intraoperative vessel pre-warning. The present study poses a promising strategy to reduce the risk of vertebral artery injury and misalignment rate in the cervical pedicle screw insertion procedure.