Flow Quantification in a Wall-Less Multiple Flow Phantom Using Ultrasound Plane Wave Doppler Imaging

Blood flow is a direct indicator of the spinal cord condition after an injury. Ultrasonic Doppler imaging is a portable, real-time modality which may be used to determine the spinal cord blood flow during surgery. Spinal cord blood flow may represent a particularly useful source of information for surgeons, it can be used to establish a diagnosis or to adapt the surgical procedure to be carried out. In this work, the flows measured respectively with a conventional focused algorithm generally included in clinical devices and from a plane wave sequence are compared. The properties of the imaging are based on an equivalent sampling frequency applied to a spinal cord vascularization phantom with a 10 MHz signal. The region of interest is calculated from the maximum value pixel in power Doppler images and used to determine the vessel diameters. The blood-mimicking fluid velocities are calculated using autocorrelation. A primary controlled flow was divided into several vessels inside wall-less phantoms. Three different configurations of vessels were studied. The vessel diameter was overestimated in all cases when using the focused algorithm, and as a result, the associated flow was almost twice as high as the actual values. The discrepancies in the flow division calculations were less than 5% with images reconstructed with plane waves. The results suggest that the blood flow inside small vessels can be more precisely estimated with ultrasound Doppler imaging using the plane wave algorithm. The distribution of the flow inside the vessels was also accurately estimated. This may allow the assessment of neurological functions following an injury and provide useful informations in other clinical issues such as cancer.