Control Method of Local Density in Fluid Microcapsules by Acoustic Standing Wave and its Monitoring

Abstract

We have developed control method of local density in fluid microcapsules to make use of ultrasound drug delivery system. It has been difficult to enhance the efficiency of medication because capsules solution diffuses after the injection, where motion of capsules in blood flow cannot be controlled. Then we have noticed that microcapsules are trapped by acoustic standing wave of ultrasound in water. We have applied this method to an artificial blood vessel and observed the variation of capsules density by using the software, which we have developed to detect local change of the brightness variation on echogram. The result indicated that capsules density increases in the upper course of the point where the standing wave is produced. We have also prepared another artificial blood vessel with bifurcation in it. We have recorded echogram of two lower courses after the bifurcation and evaluated the brightness average of the two regions in each course, when the standing wave is produced at a lower course near the bifurcation point. As the result, we confirmed that the density in microcapsules decreases when standing wave is put on the course, where the density increases on the other course. It shows a possibility to control microcapsules direction and to lead to an objective point in blood vessel.