RESUMEN
Background.Donated blood is routinely preserved for about six weeks. After that, a considerable amount of unused blood is discarded for safety. We carried out sequential measurements of the ultrasonic parameters (Velocity of propagation of ultrasound, its attenuation, and relative nonlinearity coefficient B/A) for red blood cells (RBCs) bags in their physiological preserving conditions in the blood bank, in a given experimental setup, to investigate the gradual deteriorations in the biomechanical properties of RBCs.Materials and Methods. We discuss our primary findings, which indicate the applicability of ultrasound techniques as a quantitative quick, non-invasive routine check for the validity of sealed blood bags. The technique can be applied during and beyond the regular preservation period, thus enabling deciding for each bag to either further preserve or withdraw.Results and Discussion. Considerable increases in the velocity of propagation (ΔV = 966 m s-1) and ultrasound attenuation (Δα= 0.81 dB C-1m-1) were detected to take place during the preservation time. Likewise, the relative nonlinearity coefficient showed a generally rising trend during the preservation period (Δ(B/A) = 0.0129). At the same time, a distinctive feature characteristic of a specific blood group type is realized in all cases. Due to the complex stress-strain relations and their reflection on the hydrodynamics and flow rate of non-Newtonian fluids, the increased viscosity of long-preserved blood may justify the known post-transfusion flow complications.
Asunto(s)
Eritrocitos , Ultrasonido , UltrasonografíaRESUMEN
Scanning acoustic microscopy (SAM) is used to characterize welds in a thermoplastic polymer (ABS) manufactured by injection-molding, particularly at the locations of weld-lines known to form as unavoidable significant defects. Acoustic micrographs obtained at 420 MHz clearly resolve the weld lines with morphological deformations and microelastic heterogenity. This is also where terahertz (THz) measurements, carried out in support of the SAM study, reveal enhanced birefringence corresponding to the location of these lines enabling verification of the SAM results. Rayleigh surface acoustic waves (RSAW), quantified by V(z) curves (with defocusing distance of 85 µm), are found to propagate slower in regions close to the weld lines than in regions distant from these lines. The discrepancy of about 100 m/s in the velocity of RSAW indicates a large variation in the micro-elastic properties between areas close to and distant from the weld lines. The spatial variations in velocity (VR) of RSAWs indicate anisotropic propagation of the differently polarized ultrasonic waves.
RESUMEN
Purpose: To describe the application of scanning acoustic microscopy in the GHz-range (GHz-SAM) for qualitative imaging and quantitative characterization of the micromechanical properties of the Descemet's membrane and endothelial cells of cornea tissue. Methods: Investigated were samples of a normal tissue and a tissue with Fuchs' endothelial dystrophy (FECD, cornea Guttata). Descemet's membranes were fixed on glass substrates and imaged utilizing a focused acoustic lens operating at a center frequency of 1 GHz. Results: GHz-SAM data, based on the well-established V(z) technique, revealed discrepancies in the velocity of the propagation of Rayleigh surface acoustic waves (RSAW). RSAW were found to be slower in glass substrates with FECD samples than in the same glass substrates (soda-lime) with normal Descemet membrane, which indicates lower shear and bulk moduli of elasticity in tissues affected by FECD. Conclusions: Noninvasive/nondestructive GHz-SAM, is utilized in this study for the imaging and characterization of Descemet membranes, fixated on glass substrates. V(z) signatures containing sufficient oscillations were obtained for the system of Descemet membranes on glass substrates. The observed variation in the microelastic properties indicates potential for further investigations with GHz-SAM based on the V(z) technique.
