• A Jonathan McLeod, John S H Baxter, Golafsoun Ameri, Sugantha Ganapathy, Terry M Peters, and Elvis C S Chen.
• Robarts Research Institute, Western University, London, ON, Canada, jmcleod@robarts.ca.
• Int J Comput Assist Radiol Surg. 2015 Jun 1;10(6):947-58.

PurposeEpidural and spinal anesthesia are common procedures that require a needle to be inserted into the patient's spine to deliver an anesthetic. Traditionally, these procedures were performed without image guidance, using only palpation to identify the correct vertebral interspace. More recently, ultrasound has seen widespread use in guiding spinal needle interventions. Dural pulsation is a valuable cue for finding a path through the vertebral interspace and for determining needle insertion depth. However, dural pulsation is challenging to detect and not perceptible in many cases. Here, a method for automatically detecting very subtle dural pulsation from live ultrasound video is presented.MethodsA periodic model is fit to the B-mode intenstity values through extended Kalman filtering. The fitted frequencies and amplitudes are used to detect and visualize dural pulsation. The method is validated retrospectively on synthetic and human video and used in real time on an interventional spinal phantom.ResultsThis method was capable of quickly identifying subtle dural pulsation and was robust to background noise and motion. The pulsation visualization reduced both the normalized path length and number of attempts required in a mock epidural procedure.ConclusionThis technique is able to localize the dura and help find a clear needle trajectory to the epidural space. It can be run in real time on commercial ultrasound systems and has the potential to improve ultrasound guidance of spine needle interventions.

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