Volumetric blood flow measurement in the ophthalmic artery using colour Doppler

BACKGROUND: Herewith we present a new method for measurement of the volumetric blood flow in absolute units in the ophthalmic artery. PATIENTS AND METHODS: A Philips EnVisor HD ultrasound unit with a 12 - 3 MHz linear transducer was used to measure flow in the ophthalmic artery in 8 healthy young subjects. The transducer was mounted on a custom-made holder which enabled precise and reproducible positioning in 3 axes as well as in rotation angle. Blood flow velocity and vessel diameter were measured during 10 consecutive heartbeats. The measurements were ECG-gated. Blood vessel diameter and blood flow velocity were calculated in an average heartbeat cycle. Hence blood volume over time within a heartbeat cycle as well as blood flow in mL/min were determined. Simultaneously, cardiovascular parameters have been recorded by Finapres. Short time reproducibility (5 measurements on day 1) and long time reproducibility (5 days once daily) as well as interindividual coefficient of variation were evaluated. RESULTS: Average blood flow in the ophthalmic artery in all measurements was 39.7 mL/min. The short-term intraindividual coefficient of variation was 24.1 +/- 9.2 %, the long-term coefficient 32.0 +/- 13.8 %. Interindividual coefficient of variation was 32.8 %. CONCLUSIONS: Our method allows volumetric blood flow measurements in the ophthalmic artery in absolute units, reproducible to a limited extent.