Pilot clinical study of quantitative ultrasound spectroscopy measurements of erythrocyte aggregation within superficial veins

Abstract

BACKGROUND: An enhanced inflammatory response is a trigger to the production of blood macromolecules involved in abnormally high levels of erythrocyte aggregation. OBJECTIVE: This study aimed at demonstrating for the first time the clinical feasibility of a non-invasive ultrasound-based erythrocyte aggregation quantitative measurement method for potential application in critical care medicine. METHODS: Erythrocyte aggregation was evaluated using modeling of the backscatter coefficient with the Structure Factor Size and Attenuation Estimator (SFSAE). SFSAE spectral parameters W (packing factor) and D (mean aggregate diameter) were measured within the antebrachial vein of the forearm and tibial vein of the leg in 50 healthy participants at natural flow and reduced flow controlled by a pressurized bracelet. Blood samples were also collected to measure erythrocyte aggregation ex vivo with an erythroaggregometer (parameter S 10 ). RESULTS: W and D in vivo measurements were positively correlated with the ex vivo S 10 index for both measurement sites and shear rates (correlations between 0.35-0.81, p < 0.05). Measurement at low shear rate was found to increase the sensitivity and reliability of this non-invasive measurement method. CONCLUSIONS: We behold that the SFSAE method presents systemic measures of the erythrocyte aggregation level, since results on upper and lower limbs were highly correlated.

In vivo measurement of attenuation coefficient of blood in a dorsal hand vein in a frequency range of 10–45 MHz: A preliminary study

“…Here, d s was set at 8.7 mm around a focal depth of 8.75 mm. Seven power spectra P s (f, d i ) were averaged from 0 to 60 s for the control, and seven power spectra P s (f, d i ) were averaged from 130 to 190 s for the data acquired during avascularization because the aggregation state stabilized within 1 min after avascularization [30]. Figures 2A, B depict ultrasonic short-axis B-mode images of the vascular lumen in the dorsal hand vein at rest and during avascularization for subject A, respectively.…”

Estimation of aggregate size of red blood cell by introducing reference power spectrum measured for hemispherical ultrafine wire

“…The power spectra calculated by windowing the signals with a Hanning window 6) was multiplied by the power spectrum ( ) P f d , , s 0 and the size of the RBC aggregate was determined by fitting the corrected power spectrum and the reference scattering power spectra. Because the blood vessel moves significantly immediately after avascularization and the aggregation state is not stable owing to the influence of the shear rate immediately before the avascularization, 27) the estimated sizes at rest (0-60 s) and that at the latter 7 frames (130-190 s) during avascularization were compared.…”

“…This method has been applied for the analysis and classification of various tissues, such as, the liver, skin, lymph nodes, and blood. [18][19][20][21][22][23][24][25][26][27] Cloutier et al calculated the backscattering coefficient from the RF signal obtained from the vascular lumen and estimated the attenuation coefficient of tissues and the parameters indicating the structure of the RBC aggregates, [24][25][26] and showed the possibility of monitoring the systemic inflammatory state by in vivo measurements. 27) However, few studies using these methods have involved human subjects, and diagnosis using this method has not been clinically established.…”

Quantitative ultrasound imaging of soft biological tissues: a primer for radiologists and medical physicists

“…To avoid wave interference effects, a low 4–6% hematocrit suspension datasets are used and compared to the Percus–Yevick scattering model [ 80 , 81 ] to obtain the reference BSC(f). An advantage of this calibration process is to keep similar flow condition between calibration and clinical measurements [ 82 ], since it is affecting the BSC of blood .…”