Adaptive ultrasound imaging of the lumbar spine for guidance of epidural anesthesia

Ultrasound imaging can help in choosing the needle trajectory for epidural anesthesia but anatomical features are not always clear. Spatial compounding can emphasize structures; however, features in the beam-steered images are not aligned due to varying speeds of sound. A non-rigid registration method, called warping, shifts pixels of the beam-steered images to best match the reference image. Linear prediction is used to find the warping vectors and decrease computational cost. An adaptive median-based combination technique for compounding is also investigated. The algorithms are tested on a spine phantom and human subjects. The results show a significant improvement in quality when using warping with adaptive median-based compounding.