Abstract
Purpose :
Doppler OCT technology can be used to measure flow velocity in retinal blood vessels. However, how different vessel-related parameters affect the flow measurements remains unclear. The study aims to investigate the impact of estimation error in vessel diameter, vessel center dislocation, and Doppler angle on blood flow measurement.
Methods :
Doppler OCT measurements were acquired for retinal blood vessels from a pilot study including 15 eyes with glaucoma using a Doppler OCT. For each A-scan, phase difference was obtained at each depth location. The target blood vessel region was manually identified from the combined B-scan, and Doppler angle was measured between up- & down-stream flow locations. The flow of the blood vessel was calculated based on phase difference obtained inside the identified vessel region. Only 9 measurements were selected for analysis after excluding measurements with eye motion, bad waveforms, and unclear vessel regions in targeted, up- or down-stream locations.
Results :
A 2-second flow measurement was obtained for each eye. The timepoint with max. flow within the 2s measurement was extracted for investigation of flow measurement error. Effect of estimation error in vessel diameter was tested with -20% to 20% variation of the size of manually identified vessel region at an interval of 4%. The flow measurement error due to variation in vessel size was 18.00 (95%CI: 10.44-25.56) mm/s. Effect of estimation error in vessel center location was tested by shifting the center horizontally and vertically respectively with -20% to +20% of the identified vessel diameter at 4% interval. The flow measurement error due to variation in vessel center dislocation was 9.33 (95% C.I.: 5.43-13.24) mm/s in horizontal direction and 9.44 (95%CI: 5.62-13.27) mm/s in vertical direction. Effect of estimation error in Doppler angle was tested with -20% to 20% variation of the measured Doppler angle at 4% interval. The flow measurement error due to variation in Doppler angle was 826.44 (95%CI: -80.77 to 1733.66) mm/s.
Conclusions :
Among the studied vessel-related parameters, variation in Doppler angle showed the largest flow measurement error. Cautions should be taken for reliable measurement of Doppler angle.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.