Date of Award

6-18-2021

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Electrical and Computer Engineering

Supervisor

Sazzadur Chowdhury

Rights

info:eu-repo/semantics/openAccess

Abstract

Proper diagnosis of liver disease at an early stage is very crucial for its effective treatment. Chronic liver disease if not treated can often lead to cirrhosis. At present, liver biopsy is the main diagnostic procedure. A non-destructive, patient friendly diagnostic imaging technology is necessary. Piezoelectric transducer used for High Intensity Focused Ultrasound (HIFU) has a narrower bandwidth, thus a single transducer cannot be used for both imaging and HIFU operation. But capacitive micromachined ultrasonic tranducers (CMUTs) can be used for both HIFU and imaging. In this thesis work, a unique design has been proposed where a first attempt has been made to design a 2D CMUT array for dual mode operation to detect liver cancer. First is the HIFU mode, where the device transmits a focused ultrasound to the target region in the liver just to momentarily deform (Strain) the liver tissue. Then the same device is switched to second mode which is an imaging mode. In this mode the ultrasonic image is captured using elastography process. Analytical and 3D finite element analysis has been carried out in MATLAB and Intellisuite software, respectively. Bisbenzocyclobutene (BCB), a low K polymer is used as a primary structural material for the CMUT membrane and also for the structure of the CMUT. Gold is used as a top conductor placed on top of the diaphragm. Analytical calculations have been done on several CMUT cells in an array while designing the final array. Elements ranging from 8x8, 16x16, 32x32, and 64x64 have been analyzed. Finally, 64x64 array have been used for best results with a center frequency of 7.5 MHz which are in great agreement with FEA analysis done using Intellisuite software.

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