Abstract
X-ray PIV measurement is a noninvasive approach to measure opaque blood flows. However, it is not easy to measure real pulsatile blood flows in the blood vessels located at deep position of the body, because the surrounding tissues significantly attenuate the contrast of X-ray images. This study investigated the effect of surrounding tissues on X-ray beam attenuation by measuring the velocity fields of blood flows in deep vessels of a live rat. The decrease in image contrast was minimized by employing biocompatible CO2 microbubbles as tracer particles. The maximum measurable velocity of blood flows in the abdominal aorta of a rat model was found through comparative examination between the PIV measurement accuracy and the level of image contrast according to the input flow rate. Furthermore, the feasibility of using X-ray PIV to accurately measure in vivo blood flows was demonstrated by determining the velocity field of blood flows in the inferior vena cava of a rat. This study may serve as a reference in conducting in vivo X-ray PIV measurements of pulsatile blood flows in animal disease models and investigating hemodynamic characteristics and circulatory vascular diseases.
Highlights
X-ray PIV measurement is a noninvasive approach to measure opaque blood flows
We demonstrated the feasibility of the X-ray PIV technique combined with CO2 microbubbles to measure velocity field information of blood flows in the inferior vena cava (IVC) of a live rat model with surgical intervention
This study demonstrated the feasibility of CO2 microbubbles streaming in a live rat model with real surrounding structures after applying digital image processing by conducting a comparative examination between speckle contrast and speckle size
Summary
X-ray PIV measurement is a noninvasive approach to measure opaque blood flows. it is not easy to measure real pulsatile blood flows in the blood vessels located at deep position of the body, because the surrounding tissues significantly attenuate the contrast of X-ray images. This study investigated the effect of surrounding tissues on X-ray beam attenuation by measuring the velocity fields of blood flows in deep vessels of a live rat. Synchrotron X-ray PIV with high spatial resolution was developed[3,8] This technique[8,9] produces accurate measurement results on the velocity of blood flow in an artificial stenosed vessel model[10] and ex vivo carotid artery[11]. The range of measurable velocity for the present X-ray PIV system with CO2 microbubbles as tracer particles was determined in consideration of image contrast and measurement accuracy This information is meaningful for the practical application of the x-ray PIV technique to animal models. These results would be helpful to investigate the hemodynamic characteristics of rodent atherosclerosis models in vivo
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