Contrast enhancement of speckle patterns from blood in synchrotron X-ray imaging

Hemodynamics has been a very important factor in understanding and diagnosing various vascular diseases. Recently, the X-ray particle image velocimetry (X-ray PIV) method using speckle patterns of blood has been introduced as a new quantitative visualization method for blood flows without any seeding tracer or contrast agents. In this study, the peculiar optical characteristics of blood on the synchrotron X-ray imaging method, which were not presented in previous studies, were investigated in depth and systematically. The experimental conditions required for X-ray PIV application were found to be the distance between the sample and the scintillator (∼40 cm), the thickening of the blood sample (>0.3 mm), and hematocrit (20.0–80.0%). In addition, we verified that the X-ray PIV method is reliable as an advanced flow velocimetry by comparing the flow rate evaluated from the X-ray PIV result and the input flow rate supplied from a syringe pump with an error of less than 1%. Through this study, based on the understanding of contrast enhancement mechanisms of speckle patterns from blood, we could establish a trustworthy flow visualization method that can be used effectively in hemodynamic studies.