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Terschelling

Imaging

Ultrasound Bubbles Imaging Brandaris

To study the dynamics of the bubble upon insonification optically, e.g. under a microscope, it is necessary to use a high-speed camera. As the ultrasound frequencies used in medical diagnostic imaging are in the range of 1 to 10 MHz, a high-speed camera with a frame rate of 10 million frames per seconds (Mfps) or even faster is required. 

Cameras that record at these high speeds exist, however their recording capability is limited to a total number of 8 frames only. The ultrasound typically lasts for 10 cycles during which the response of the microbubbles can be highly non-linear. The number of frames should be sufficient to record the whole process, therefore, more than 100 frames are desirable. 

Rotating mirror cameras produce frame records at up to 25 million frames per second. They record up to 130 frames on a negative film track expose to the image which is relayed to the film by associated lenses and a fast rotating mirror (1.2 million rpm). The most important disadvantage of using negative film is its poor light sensitivity which is limited to 3200 ASA, highly insufficient for the short exposure times in our microscopic application.  

By replacing the negative film track by a set of very light sensitive CCD detectors we have now constructed a digital ultra high-speed camera system which records a full sequence of 128 digital images at a frame rate of 25 Mfps.