| Many studies have correlated red blood cell (RBC) hyperaggregation with circulatory pathologies such as diabetes mellitus. However, none of these studies have measured quantitative values of RBC aggregation in situ in relation to vascular diseases.;This study characterized RBC aggregation in situ and in vivo with high frequency ultrasound at 25 MHz and 35 MHz. Backscattered signals from veins of the upper and lower limbs were measured in 10 normal subjects and 10 patients with type 2 diabetes affected by lower limb arterial disease.;The hypotheses of this project were that RBC aggregation is higher in the diabetic group than in the control group, and that high frequency ultrasound could quantify RBC aggregation in situ.;Two in vivo aggregation parameters D.gamma and W.gamma (with D and W being computed with the structure factor size and attenuation estimator, and gamma with hemodynamic measurements) were determined for each subject. D represents the mean size of aggregates, W the packing factor describing the spatial organization of these aggregates, and gamma the shear rate of flowing blood. Moreover, biochemical data, the ankle-brachial index and in vitro aggregation indices obtained with laser backscattering were also measured to validate the in vivo parameters.;Our results show that D.gamma and W.gamma are higher in diabetic patients than in control subjects at 25 MHz and 35 MHz. This reveals that the RBC aggregability is more elevated in the pathological group, which is consistent with the in vitro aggregation indices also measured. However, no significant difference was found between the in vivo results over the arm vein and the foot vein. This suggests that hyperaggregation in diabetic patients with lower limb arterial disease is not localised in the foot, where severe symptoms often occur, but is generalized in the systemic circulation. RBC hyperaggregation, arterial and venous hemodynamic disorders, and a high level of inflammation are phenomena that have been observed in diabetic patients in this study. In conclusion, this project that used high frequency ultrasound shows that this method opens the field to a better understanding of the in vivo impact of RBC aggregation on vascular diseases.;Key words. Red blood cell aggregation, ultrasound backscattering, in vivo assessment, diabetes, lower limb arteriopathy. |
