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The photometric studies of blood aggregation characteristics were started by the works of Dognon et.al. [1,2] who registered the deviation of the intensity of light scattered from a layer of blood under mixing and after its halt. They have shown the dependence ofthe signal (scattering intensity) on orientational aggregation ofthe erythrocytes. The detailed study of the intensity variation oflight passing through a blood layer in a rheoscope coneplate viscometer was carried out by H.SchmidSchonbein et.al. [3,4,5]. A simplified modification of the registration technique in case of light passing through a special couvette under lOOjn thick after the halt of stochastic mixing of blood, has been elaborated by R.Tukhvatulin (1986) [6]. Backscattering from a shear Couette flow was registered by S.Usami and S.Chien (1973) [7]. This registration mode allowed to considerably raise the probed volume of blood. Detailed analysis has shown that there exists a strong connection between the intensity of the transmitted or backscattered light with the aggregation characteristics ofthe erythrocytes suspension. This has made the technique a major one in clinical and experimental hemorheology (J.F.Stoltz, M.Donner, 1987) [8]. In accord with the primary experiments two approaches have been developed in the aggregometry. The first is based on the registration of light transmission through the StUdied thin (25pi) blood layer in a coneplate type viscometer [3,4,5]. Thesecond is based on the registration ofthe backscattered light from a blood layer in a Couette type viscometer [9, 1 0]. The corresponding commercial apparatuses most commonly used are: the Myrenne aggregometer and the Sefam erythroaggregometer. Anyhow the differences in geometry of the flow and in the detection modes of the outcome light yield different results in the study of the hyperaggregational syndrome even in the in vitro experiments [11]. Attempts of theoretical analysis of multiply scattered light from blood [12,13,14] have not yieldod any important results in the estimation of aggregates dimensions and morphology, and thus could not form the basis to substantiate the optimum construction of the aggregometer. Such optimization includes the optimal choice: of the shear blood layer thickness, ofthe registration mode of scattered light (transmitted or backscattered), of the scattering angle and detection aperture. The ideal design of aggregometer must give reliable information about the sizes of aggregates in each moment of the spontaneous aggregation of erythrocytes and enable to estimate the velocity of aggregation process and durability of aggregates. In this article we shall characterize each of these problems in more detail.
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