Pseudo three-dimensional vision-based nail-fold morphological and hemodynamic analysis

In this study, a Pseudo three-dimensional Vision-based Nail-fold Morphological and Hemodynamic Analysis (PTVNMHA) is proposed to automatically extract morphological/hemodynamic features from a microscopic nail-fold image sequence, reconstruct the corresponding pseudo three-dimensional microvascular models, and visualize the dynamic blood flow in the model constructed. The morphological features extracted include the number, width/height, density, arteriolar limb caliber, curved segment caliber, venular limb caliber, blood color, tortuosity, and width of the curved segment of capillaries. The hemodynamic features identified are blood flow velocity and blood flow rate. All are significant pathological indicators with a spatial precision up to 1.6 μm. The diameters of cross-sections along the centerlines of capillaries are identified and employed to reconstruct the pseudo three-dimensional microvascular surface meshes. The microscopic image sequence acquired is mapped to the corresponding microvascular model constructed to perform dynamic blood flow visualization. Compared with laser Doppler velocimetry, PTVNMHA can derive blood flow velocities for each capillary across the microscopic range separately in much higher precision and obtain diversified morphological and hemodynamic features of capillaries with a low-cost equipment setup. In addition to the blood flow velocity, blood flow rate, which keeps almost constant no matter where the measuring position is in a capillary, has also been measured and proposed as a useful feature to discriminate patients with hypertension from the normal with great significance (p<0.001). In the future, large scale experiments will be conducted to diagnose patients with anemia as well as patients with essential and secondary hypertension to verify effectiveness of the PTVNMHA system.