Volumetric flow rate of ophthalmic artery in healthy individuals using a new magnetic resonance imaging technique

Abstract

AbstractPurpose To measure the volume flow rate of the ophthalmic artery (OA). A phase contrast magnetic resonance imaging (PCMRI) protocol was developed to assess volume flow rate of OA in healthy young (HY) and elderly (HE).Methods The study was performed with a 3‐Tesla scanner on HY (n=51,28females,age=64‐80ys) and HE (n=51,28females,age=21‐30ys). The OA were localized by a 3D time of flight (3DTOF) sequence. To measure the volume flow rate, a 2D PCMRI sequence was optimized to reach a spatial resolution of 0.35mm/pixel. Based on 3DTOF data, the flow measurement was perpendicular to OA. Mean volume flow rate (Qmean), resistive index (RI), arterial volume change (ΔV) and symmetry index (SI) were computed from the volume flow rate curve. Accuracy of MRI measures was studied using a vessel‐phantom (Ø=1.4mm). Six constant flow rates (5.54‐34.41mL/min) were used as reference.Results Phantom investigation showed good agreement between the reference and MRI measurements with a percentage error <7%. The mean and SD of RI (HE:0.68±0.08; HY:0.63±0.09), ΔV (HE:26.35±14.03uL; HY:18.51±7.23uL) and SI (HE:0.58±0.03; HY:0.63±0.03) of OAs volume flow rate curve were significantly higher in the elderly group compared to the young group (RI,p<0.05; ΔV,p<0.001; SI:p<0.001). No statistical difference was found in Qmean between HE(10.91±5.44mL/min) and HY (10.27±4.46mL/min) individuals (p>0.05).Conclusion Volume flow rate measurement of OA vessels using PCMRI is possible. Contrary to color Doppler imaging, PCMRI technique does not alter IOP during the measurements. This method may provide a precise description of the dynamics of the volume flow rate of OA during the cardiac cycle.