Modeling Simulating and Quantification of Optical Images at Ultrasound Contrast Bubbles
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Date
2017-07
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Addis Ababa University
Abstract
Microbubble based ultrasound contrast agents are being used in clinical settings to
Enhance backscattered ultrasound signal from blood pool during perfusion and blood flow
Measurements. Often individual bubbles are characterized optically by recording their
Vibrations with a fast framing camera and direct quantitative information on their dynamic
Behavior can be derived. Nonetheless, when a three-dimensional object, stack of infinitely thin
Two-dimensional layers, is imaged through a microscope, the image formed onto the charge
Coupled device element consists of contributions from all layers. If a bubble is larger than the
Depth of focus, the part of the bubble above the focal plane influences the image formation
And therefore the bubble size measured. Thus, this thesis presents a methodology to compute
Two-dimensional image formation from three-dimensional objects, hollow spheres and find
Under which circumstances the optical image formation leads to a significant deviation in
Measurement of the actual size. Two-dimension image formations of the three-dimensional
Object was computed by convolving the slices of an artificial object, hollow spheres with the
Respective weighted point spread function and summing all convolved slices. Finally, image
Processing was applied the optical image formed to quantify the object size and a systematic
Error was observed for objects in focus with radius 1:65mm. Also it was concluded that
Even though a three-dimensional object is in focus, there is discrepancy of up to 0.66% in size
Measurement. In addition, size measurement of an object for the same shift above the focus and
Below the focus could differ by up to 3.6%. Moreover, defocusing up to 90% could result up
To 64.7 mean percentage error. The results reveal that defocusing above 25% severely deviates
Size measurements. This thesis hopes to offer a standard for quantification of optical images of
Three-dimensional objects, and in the future actual size of an object could be measured from its
Defocused optical images.
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Biomedical ;Engineering