Biomedical Engineering

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Browsing Biomedical Engineering by Author "Abraham, Habtamu"

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    Modeling Simulating and Quantification of Optical Images at Ultrasound Contrast Bubbles
    (Addis Ababa University, 2017-07) Abraham, Habtamu; Assefa, Dawit (PhD.)
    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.