Development Of A Nonlinear Frequency Compounding Method With Applications In Ultrasound Imaging And Thermometry
thesisposted on 15.10.2021, 20:58 by Tyler Hornsby
Frequency compounding is an ultrasound imaging technique used to reduce artifacts and improve signal-to-noise-ratio (SNR). In this work a new nonlinear frequency compounding (NLFC) method was introduced, and its application in B-mode imaging and noninvasive thermometry was investigated. NLFC input frequencies were optimized to maximize speckle-signal-to-noise-ratio (SSNR) in a tissue mimicking phantom, and the method was then used to produce maps of the temperature sensitive change in backscattered energy of acoustic harmonics (hCBE) during heating of ex vivo porcine tissue with a focused ultrasound transducer. A hCBE-to-temperature calibration was also performed and temperature maps produced. Lastly, a comparative study of the NLFC and previously used nonlinear single frequency (NLSF) method was completed. By using the NLFC method it was concluded that SSNR of B-mode and backscattered energy images, SNR of hCBE maps, and temperature map agreement with a theoretical COMSOL based model were improved over the previously used NLSF method.