Model-based correction of angle-dependencies in navigated 3-D flow imaging during neurosurgical interventions

In neurosurgery, information of blood flow is important to identify and avoid damage to important vessels. Three-dimensional intraoperative ultrasound color flow imaging has proven useful in this respect. However, due to Doppler angle-dependencies and the complexity of the vascular architecture, clinical valuable 3-D information of flow direction and velocity is currently not available. In this work we aim to utilize navigated ultrasound imaging to correct for angle-dependencies in 3-D using a model-based approach. By using a navigation system to register the position and the orientation of 2-D ultrasound images, we can construct a 3-D model of the neurovascular tree. The position data is used to angle-correct Doppler measurements automatically. In vitro experiments revealed a good accuracy for estimating the true direction of flow. Angle-correction velocities further resulted in a bias of 0.12-0.96 cm/s. The method also showed promising results in vivo, improving the visualization of the distal branches of an intracranial aneurysm.