Ultrasound characterization of red blood cell aggregation with intervening attenuating tissue-mimicking phantoms

Abstract

The analysis of the ultrasonic frequency-dependent backscatter coefficient of aggregating red blood cells reveals information about blood structural properties. The difficulty in applying this technique in vivo is due to the frequency-dependent attenuation caused by intervening tissue layers that distorts the spectral content of signals backscattered by blood. An optimization method is proposed to simultaneously estimate tissue attenuation and blood structure properties, and was termed the structure factor size and attenuation estimator ͑SFSAE͒. An ultrasound scanner equipped with a wide-band 25 MHz probe was used to insonify porcine blood sheared in both Couette and tubular flow devices. Since skin is one of the most attenuating tissue layers during in vivo scanning, four skin-mimicking phantoms with different attenuation coefficients were introduced between the transducer and the blood flow. The SFSAE gave estimates with relative errors below 25% for attenuations between 0.115 and 0.411 dB/ MHz and kR Ͻ 2.08 ͑k being the wave number and R the aggregate radius͒. The SFSAE can be useful to examine in vivo and in situ abnormal blood conditions suspected to promote pathophysiological cardiovascular consequences.

Predicting human blood viscosity in silico

“…The accurate prediction of the non-Newtonian behavior from simulations of cell suspensions suggests a new paradigm for rheology of cell suspensions and blood in particular. As an example, an abnormal increase in RBC aggregation is a pathological state associated with many diseases, such as deep venous thrombosis, atherosclerosis, AIDS, myeloma, and diabetes mellitus, which may afflict many different sites of the human arterial tree (37)(38)(39)(40). However, such correlations have had few theoretical guidelines for their interpretation.…”

“…However, such correlations have had few theoretical guidelines for their interpretation. The modeling of cells whose parameters are determined from experiments on single cells (41) can be extended to abnormal and diseased cells, and in combination with the aggregation model, their suspensions can be simulated to allow quantitative comparison with rheological measurements and to guide in vivo ultrasonic measurements to yield a more precise diagnosis of the aforementioned diseases (40). The predictive capability of accurate modeling of cell and capsule suspensions can be readily extended to a variety of engineering and material science applications.…”

Experimental assessment of four ultrasound scattering models for characterizing concentrated tissue-mimicking phantoms

“…To our knowledge, neither the PM nor the SFM have been tested so far in blood characterization studies as means of predicting the scatterer concentration because the hematocrit is assumed to be known a priori. 26 However, our study showed that the estimation of the scatterer concentration is not straightforward using the PM or the SFM. The following discussion intends to explain why the concentration estimates cannot be obtained directly using standard minimization procedures in the 6-22 MHz frequency bandwidth studied here.…”

“…(7) in Ref. 26). In the present study, the reference scattering medium used was a suspension of polyamide microspheres with a radius of 2.5 µm (orgasol 2001 UD NAT1, Arkema, France) present at a low concentration of 0.5% and gently stirred in water.…”

“…In the case of blood ultrasound characterization, the reference scattering medium is generally a low 6% hematocrit red blood cell suspension. 25,26 Since the radius of one red blood cell sphere-shaped model is around 2.75 µm, the corresponding theoretical BSC is given by the classical version of the PM written for an ensemble of identical Rayleigh scatterers (see Eq. (7) in Ref.…”