Morphology provides physicians with advanced analysis of TCD waveforms to enable faster and easier assessment of patients with suspected neurological conditions, including stroke. Waveforms are collected using the NovaGuideTM 2 Intelligent Ultrasound with post-exam analysis available in NovaGuide View. Morphology features include Velocity Curvature Index, Velocity Asymmetry Index, Systolic Slope, and P2Ratio.
Definition: VCI is a measure of the overall curvature of a TCD waveform. A lower value of VCI represents a more blunted waveform.
Physiologic Relevance: VCI is an objective method to quantify changes in the TCD waveform that can occur due to various stroke pathologies.1
Definition: Using the maximum velocity segments from each hemisphere, MVP-VCI looks at bilateral VCI values and reports the lower VCI number.
Physiologic Relevance: The extent to which the blood flow is disrupted and the resulting impact on the TCD waveform can be different on the left and right hemispheres of the brain. When bilateral measurements are available, MVP-VCI generally describes the waveform ipsilateral to the neurologic condition.1-3
Definition: MVP-VAI is the ratio of mean velocities from a set of bilateral TCD waveforms. The maximum velocity segment from each side is used to minimize the effect of the angle of insonation.
Physiologic Relevance: MVP-VAI represents the level of blood flow velocity disparity between cerebral hemispheres. Quantifying the degree of hemispherical asymmetry in blood flow velocity could provide information on the severity and location of a neurological condition.4,5
Definition: Systolic Slope is the average rate of change in velocity for the systolic upstroke phase of the cardiac cycle.
Physiologic Relevance: Systolic Slope has been reported to be inversely related to vascular resistance to blood flow. A low systolic slope could be indicative of obstruction to flow.6-8
Definition: P2Ratio is the ratio of the second peak to the first peak of the TCD waveform.
Physiologic Relevance: P2Ratio is hypothesized to be related to the distal vasculature’s compliance. An elevated P2Ratio could indicate decreased compliance in the distal vasculature.9
Download the Morphology Interpretation GuideDOWNLOAD THE GUIDE