Perfusion Estimation in Volumetric Imaging of Ultrasound Contrast Agents.

Perfusion;Ultrasound;Contrast Agent;Engineering;Health Sciences;Biomedical Engineering

Chen, Nelson G.Rubin, Jonathan M. ;

University of Michigan

关键词: Perfusion;    Ultrasound;    Contrast Agent;    Engineering;    Health Sciences;    Biomedical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62377/ngchen_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This dissertation presents research involving the investigation of perfusion measured using volumetric imaging of ultrasound contrast agents. Ultrasound contrast agents are micrometer-sized gas bubbles that track the blood circulation. They strongly reflect ultrasound; therefore, a small quantity of agent produces strong echoes, enabling the examination of microcirculation.The development of three-dimensional ultrasound has led to entire tissue volumes being imaged. Such imaging, now even being performed with two-dimensional arrays, provides more information for diagnostic purposes. Therefore, exploration of contrast imaging in three-dimensions is needed to determine potential benefits in clinical use.The study of blood flow using contrast agent has been dominated by the imaging of contrast refill into a volume previously cleared of contrast. First, a mechanical method of performing contrast clearance/refill in a three-dimensional volume using two one-dimensional arrays is introduced. The method generated expected volumetric contrastimages in a perfused tube phantom, based on the well-known parabolic velocity profiles of laminar flow. This consistency showed that the mechanical method properly images the refill into a volume at every time after contrast clearance.Second, the apparatus was applied to a perfused kidney phantom. Refill curves were obtained for the kidney cortex throughout the volume. Refill curves were also obtained using a modified interval imaging technique for comparison. A normalization scheme, which uses the renal artery as a measure of the instantaneous contrast signal intensity, was used to correct for contrast degradation, and to make absolute perfusion estimates. No significant difference was observed between the volumetric perfusion measurements and those obtained from the modified interval imaging, suggesting the independence of refill curves from contrast clearance volume.Finally, a general form of the normalization scheme was developed that permits normalization from a generic large vessel. The model was tested by imaging different-sized tubes at two orientations, and examining the normalization factor derived. Comparisons were made to values obtained using simpler approaches (global mean and attenuation only models). Values obtained using the model were similar across tube sizes, and were generally larger than those obtained otherwise. Both partial voluming and contrast attenuation are shown to play substantial roles in proper normalization.