Relative permittivity measurement during the thrombus formation process using the dielectric relaxation method for various hematocrit values

The relative permittivity ε ′ and the dielectric loss ε ″ for various hematocrit values H for static bovine blood condition have been measured using the dielectric relaxation method to detect thrombosis in real time. The suitable measurement frequency f m ranged within 60 kHz to 1 MHz, and the relaxation frequency of red blood cells (RBCs) f rc was observed to be 2 MHz. In the f m , the temporal change of normalized ε ′ exhibited a minimum (called as bottom point). The bottom point was observed to be exponentially shortened as H increased. This characteristic of the ε ′* minimum is discussed from three viewpoints: during fibrin formation, direct thrombus formation, and rouleaux formation processes. ε ′* during the fibrin formation process decreased over time, irrespective of f . However, ε ′* in f m during the direct thrombus formation process and during the aggregation formation process increased immediately and rapidly over time. Therefore, the ε ′* bottom point in f m might be the indication of micrometer-scale thrombus formation by RBC aggregation due to fibrin formation.