In-situ characterization of red blood cell aggregation measured with high frequency ultrasound in type 2 diabetic patients

The present study investigates in-vivo and in-situ red blood cell (RBC) aggregation in both upper and lower limbs with high frequency ultrasound in diabetic patients presenting lower limb ischemia. Ultrasonic radio-frequency images were acquired at 25 MHz from both cephalic (CEP) and great saphenous (GSV) veins in 10 healthy subjects (CONT group), 6 diabetic patients presenting intermittent claudication (Grade I group, i.e. Rutherford classification), and 4 diabetic patients affected by chronic critical ischemia (Grade II/III group). In addition to hemodynamic parameters (i.e. vessel diameters, blood flow velocities and shear rates), the mean fractal size of RBC aggregates (D) was estimated with the Structure Factor Size and Attenuation Estimator. In the Grade I group, D tended to be higher than CONT for the GSV only. Moreover, D values were significantly higher in GSV versus CEP in the Grade I group. Surprisingly, we also observed significantly lower D values in Grade II/III patients compared to Grade I for the GSV. This could be due to arteriovenous communications (and the concomitant increase in blood velocity) occurring in patients with chronic critical ischemia. In summary, we have been able to observe local differences in RBC aggregation in the lower limb with ultrasound. Rheological disorders are likely involved in the progression of lower limb ischemic phenomena. The proposed quantitative cellular imaging method could become an additional tool for the management of diabetic patients presenting lower limb ischemia.