Spinal surgery is particularly challenging for surgeons, requiring a high level of expertise and precision
without being able to see beyond the surface of the bone. Accurate insertion of pedicle screws is critical
considering perforation of the pedicle can result in profound clinical consequences including spinal cord,
nerve root, arterial injury, neurological deficits, chronic pain, and/or failed back syndrome.
Various navigation systems have been designed to guide pedicle screw fixation. Computed tomography
(CT)-based image guided navigation systems increase the accuracy of screw placement allowing for 3-
dimensional visualization of the spinal anatomy. Current localization techniques require extensive
preparation and introduce spatial deviations. Use of near infrared (NIR) optical tracking allows for realtime
navigation of the surgery by utilizing spectral domain multiplexing of light, greatly enhancing the
surgeon’s situation awareness in the operating room. While the incidence of pedicle screw perforation and
complications have been significantly reduced with the introduction of modern navigational technologies,
some error exists. Several parameters have been suggested including fiducial localization and registration
error, target registration error, and angular deviation. However, many of these techniques quantify error
using the pre-operative CT and an intra-operative screenshot without assessing the true screw trajectory.
In this study we quantified in-vivo error by comparing the true screw trajectory to the intra-operative
trajectory. Pre- and post- operative CT as well as intra-operative screenshots were obtained for a cohort of
patients undergoing spinal surgery. We quantified entry point error and angular deviation in the axial and
Carotid atherosclerosis is a critical medical concern that can lead to ischemic stroke. Local hemodynamic patterns
have also been associated with the development of atherosclerosis, particularly in regions with disturbed flow
patterns such as bifurcations. Traditionally, this disease was treated using carotid endarterectomy, however
recently there is an increasing trend of carotid artery stenting due to its minimally invasive nature. It is well
known that this interventional technique creates changes in vasculature geometry and hemodynamic patterns
due to the interaction of stent struts with arterial lumen, and is associated with complications such as distal
emboli and restenosis. Currently, there is no standard imaging technique to evaluate regional hemodynamic
patterns found in stented vessels.
Doppler optical coherence tomography (DOCT) provides an opportunity to identify in vivo hemodynamic
changes in vasculature using high-resolution imaging. In this study, blood flow profiles were examined at the
bifurcation junction in the internal carotid artery (ICA) in a porcine model following stent deployment. Doppler
imaging was further conducted using pulsatile flow in a phantom model, and then compared to computational
fluid dynamics (CFD) simulation of a virtual bifurcation to assist with the interpretation of emphin vivo results.