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Shear rate is known to be a determining factor for red blood cell (RBC) aggregation and thus has significant effects on ultrasound backscattered power from blood. But shear rate could not fully explain the cyclic variation of backscattered power from blood under pulsatile flow. The flow acceleration was suggested as another hemodynamic factor to enhance the RBC aggregation and thus backscattered power from blood. In this study, two RBCs were placed along a streamline during the deceleration phase of the pulsatile flow, and the time for two RBCs to form a rouleau was numerically simulated with depletion model. Furthermore, 393 RBCs were randomly placed under pulsatile flow and laminar flow, and the results were compared. Results reveal that flow acceleration would increase the RBC aggregation speed and mean aggregate size (MAS). [ABSTRACT FROM PUBLISHER]

For high-frequency applications, the mechanical scanning of a single element transducer has been mostly utilized. However, it requires space for the mechanical motion of the transducer for both linear and sector scanning. In this paper, an ultrasound biomicroscopy (UBM) system by rotational scanning of a high-frequency angled transducer is designed and implemented. And it is applied to obtain the posterior images of a porcine eye through a minimal incision hole of 1 mm in diameter for scanning space. The retina with the sclera was visualized in the relative angle range of 270° ∼ 330° and the distance range of 6∼7 mm. The retina and sclera layer seemed to be folded because the distance between the tip of the angled transducer and the layer was varied while the transducer was rotated. The rotation system should be improved for the higher accuracy and precision such as the optimal scanning angle, step angle and data length. Moreover, the focal length should be considered for the image quality. This implementation would be the first step of the rotational UBM system. [ABSTRACT FROM PUBLISHER]