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T. Schmoll, C. Kolbitsch, C. Ahlers, U. Schmidt-Erfurth, R. A. Leitgeb; Structural and Functional Ultra-High Speed Retinal Tomography at 200.000 Hz. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1655.
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To image with good resolution and without motion artifacts small retinal details as the retinal capillary bed and photoreceptors without adaptive optics or active retinal tracking. The ultra-high imaging speed offers a completely new perspective for 4D flow imaging. It allows visualizing flow within the retinal capillary network in the foveal region as well as visualizing pulsation of larger retinal vessels in the optic nerve head region.
New CMOS technology brought a large improvement in imaging speed reaching 200.000 A-scans/sec with still very good axial resolution (5µm in tissue). At these scan rates the time to acquire a 500x200x576 volume is reduced to 0.5 sec, which minimizes transverse motion blurring and yields high transversal resolution up to the limits originating from ocular aberrations. However the recording time for one volume has to be further decreased in order to observe dynamic perfusion changes within consecutive volumes. To achieve a volume rate of 13 per second we diminished lateral sampling to 150x100 points. This rate is sufficient to resolve the heart cycle and to visualize flow within the retinal capillary network. To study the dynamics of retinal arterial occlusions, first a Doppler FDOCT (D-FDOCT) volume of a larger area is recorded to identify the occlusion within the patient’s retina, following circular D-FDOCT B-scans as a function of time surrounding the occlusion. To compare pulsation within retinal vessels to the systemic circulation the instrument is equipped with a pulse oximeter for continuous SpO2 monitoring, parallel to the D-FDOCT measurements.
The high transversal resolution capability of ultra-high speed retinal tomography has been demonstrated. 4D FDOCT capillary flow movies of healthy and diseased eyes have been acquired. Furthermore first D-FDOCT patient studies have been performed. The capillary network of patients with ocular occlusions has been imaged to visualize functional pathologies on the level on perfusion.
The performance of structural and functional FDOCT imaging at ultra-high speed has been demonstrated. First patient studies investigating retinal blood flow of diseased eyes have been performed. We believe that the unique capability to study retinal blood flow dynamics volumetrically in-vivo will lead ultimately to a better understanding of major retinal diseases.
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