Image Contrast Enhancement using Poly Vinyl Alcohol Microbubble Response to High MI Ultrasound

Abstract: The induced rupturing of Poly Vinyl Alcohol (PVA) microbubbles with high mechanical index (MI)ultrasound beam is used in multiple medical application such as drug delivery, image contrastenhancement and perfusion imaging.In this work, Triggered imaging technique with subtraction algorithm is used to enhance themicrobubble’s (MB) contrast over tissue (CTR). The technique is performed by rupturing MBwith one destruction wave sequence followed by 100 B-mode imaging pulse sequences. Theimages obtained are then subtracted by a base image that is selected after the destruction pulse[1].The result of this technique depends mainly on the effectiveness of destruction pulse inrupturing highest number of MB. This has been tested through tissue mimicking phantomwithout replenishing the MB. The evaluation of the methods is done through the CTR and CNRcalculation for each of the 100 frames.The contrast enhancement technique used has also been tested with similar setup but withcontinuous replenishment of MB. The evaluation is done by comparing CNR and CTR results forthe 100 frames obtained by B-mode imaging with the ones resulted from the subtractionalgorithm.The contrast values obtained from both experiments are used in driving the characterization ofPVA response to high MI.The result for the destruction pulse effectiveness shows that the pulse indeed managed toreduce number of MB, but not to the lowest. This is because of leaked gas from cracked shell,the shell acoustic enhancement effect, and large bubbles which managed to survive.The Triggered imaging has shown large improvement in CTR value with use of the subtractionalgorithm when compared to B-mode results. In addition, it has provided an experimental wayfor perfusion imaging and quantification by monitoring CTR value after the destructive pulse[2]. This sets the bases for experimental research relevant to tissue perfusion at ultrasound labof KTH.