In Vitro Simulation of the First Technique for Non-invasive Measurement of Volumetric Ophthalmic Artery Blood Flow in Humans

BACKGROUND AND OBJECTIVE: To evaluate the accuracy, reproducibility, and variability of volumetric flow measurements taken by color Doppler imaging ultrasound, using an in vitro phantom model to simulate the ophthalmic artery. MATERIALS AND METHODS: An agar flow phantom with two wall-less lumens was constructed to simulate the ophthalmic artery. Velocity and volumetric flow measurements were taken for various flow rates and ultrasound probe positions. The measurements were analyzed for accuracy, reproducibility, and variability. RESULTS: Velocity measurements were more accurate than flow measurements (8 of 24 vs 3 of 24 accurate trials). The average coefficient of variation for volumetric blood flow was 11.4% (n = 120). Volumetric flow significantly correlated with velocity (R-2 = 0.408, n = 600, P < .001). The highest correlation was achieved using the large lumen with the probe held at 750, offset to the flow (R-2 = 0.862, n = 75). CONCLUSION: Based on an in vitro model, non-invasive color Doppler imaging recordings of volumetric flow measurements in the ophthalmic artery significantly correlated with velocity and higher correlations were found using the larger lumens, although the data showed a lack of high accuracy in measurements of flow and velocity.