Long-term movement analysis of cervical vertebrae with normalized cross-correlation and subsample estimation

Cervical spine pathoanatomy is typically evaluated by static radiographs, CT or MRI; however, these modalities are unable to directly measure the dynamic performance of the spine that account for its functionality. We have developed an ultrasound based technique that provides a non-invasive, realtime, quantitative, textitin-vivo image of the C-spine that allows for assessment of the dynamic motion of contiguous functional spinal units. The purpose of this work was to develop a multiframe method that enables accurate tracking of the motion of vertebra from ultrasound radio-frequency data. The tracking method was validated using a vertebra phantom and 6 human cadaveric specimens subjected to cyclic displacement. Ultrasound was capable of accurately tracking vertebral motion when using the multi-frame method compared to the traditional frame-by-frame, or multi-compression methods.