Disposable laser-diffraction ektacytometry to measure red blood cell deformability

The laser-diffraction technique has been applied to design a slit rheometer for measuring red blood cell deformability over a range of shear stress. A laser beam traverses a diluted blood suspension and is diffracted by RBCs in the volume. The diffraction patterns are captured by a CCD-video camera, linked to a frame grabber integrated with a computer. When deforming under decreasing shear stress, RBCs change gradually from the prolate ellipsoid towards a circular biconcave morphology. Both the laser-diffraction image and pressure were measured with respect to time. Which enable to determine the elongation index (EI) and the shear stress. The range of shear stress is 0similar to35 Pa and the measuring time is less than 2 min. The elongation index(EI) is determined from an isointensity curve in the diffraction pattern using an ellipse-fitting program. The key advantage of this design is the incorporation of a disposable element that holds the blood sample, which enables the present system to be easily used in a clinical setting.