Frequency compounded imaging with a high-frequency dual element transducer |
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| Authors: | Jin Ho Chang Hyung Ham Kim Jungwoo Lee K Kirk Shung |
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| Institution: | 1. Department of Chemistry, Physics and Environment, Dunarea de Jos University of Galati, 111 Domneasca Street, 800201 Galati, Romania;2. Department of Mathematical Sciences, Delaware State University, Dover, DE 19901-2277, USA;3. Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia;1. Department of Mechanical & Aerospace Engineering, The North Carolina State University, Raleigh, NC 27695, USA;2. Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA;1. Department of Mechanical Engineering, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea;2. School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China;1. Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;2. Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;3. Information Materials and Devices Research Center, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai, China;1. The Department of Mechanical and Aerospace Engineering at North Carolina State University, Raleigh, NC 27695, USA;2. The Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC 27599, USA |
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| Abstract: | This paper proposes a frequency compounding method to reduce speckle interferences, where a concentric annular type high-frequency dual element transducer is used to broaden the bandwidth of an imaging system. In frequency compounding methods, frequency division is carried out to obtain sub-band images containing uncorrelated speckles, which sacrifices axial resolution. Therefore, frequency compounding often deteriorates the target-detecting capability, quantified by the total signal-to-noise ratio (SNR), when the speckle’s SNR (SSNR) is not improved as much as the degraded axial resolution. However, this could be avoided if the effective bandwidth required for frequency compounding is increased. The primary goal of the proposed approach, hence, is to improve SSNR by a factor of two under the condition where axial resolution is degraded by a factor of less than two, which indicates the total SNR improvement to higher than 40% compared to that of an original image. Since the method here employs a dual element transducer operating at 20 and 40 MHz, the effective bandwidth necessary for frequency compounding becomes broadened. By dividing each spectrum of RF samples from both elements into two sub-bands, this method eventually enables four sets of the sub-band samples to contain uncorrelated speckles. This causes the axial resolution to be reduced by a factor of as low as 1.85, which means that this method would improve total SNR by at least 47%. An in vitro experiment on an excised pig eye was performed to validate the proposed approach, and the results showed that the SSNR was improved from 2.081 ± 0.365 in the original image to 4.206 ± 0.635 in the final compounding image. |
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