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Bubbles

Ultrasound Bubbles Imaging Brandaris

An ultrasound contrast agent is made of tiny microbubbles, which scatter ultrasound very effectively. The bubbles consist of air or an inert gas and they are coated with a protein, lipid or polymer layer. This prevents the bubbles to either dissolve in the blood or to coalesce to form larger bubbles. The contrast agents are injected in the patient's arm and they are so small that they are transported into the smallest capillaries. Using contrast enhanced echocardiography the cardiologist can see which part of the heart muscle is poorly perfused.         

The interaction of contrast agent bubbles and ultrasound is currently subject to many studies. The ultrasound consists of oscillations of high and low pressure and a microbubble subjected to ultrasound will grow and shrink accordingly, it will start to oscillate at the frequency of the ultrasound. At higher ultrasound intensity the oscillations become more extreme and the non-linear behavior will start to appear. The bubble will produce higher harmonics e.g. at twice or three times the fundamental frequency). It could also become instable and could violently collapse. These interesting effects are tested and implemented in new diagnostic and therapeutic ultrasound applications.     


Image: Michiel Postema, Erasmus MC Rotterdam