| Summary: | 碩士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 103 === High frequency ultrasound imaging, which provides higher spatial resolution and better sensitivity for detecting shear wave displacement, is suitable for pre-clinical small animal and 3-D cell culture system studies. In our previous study, we have implemented shear wave elasticity imaging (SWEI) on our high frequency single element system. However, due to attenuation and diffraction, the signal-to-noise ratio (SNR) and estimation accuracy decrease with distance. The measured speed map tends to be incorrect for large region of interest (ROI). In this research, we hypothesize that by adopting near field SWEI (i.e., push transducer and image transducer are kept close to each other) SWEI resolution and accuracy can be improved. Furthermore, we try to combine the near field SWEI and computed tomography, hoping to have an even higher resolution. Our results show that in phantom experiments, the contrast-to-noise ratio is 1.45 for the previous setup, and 2.00 for the near field setup; the shear wave velocity bias of inclusion is -19.04% for the previous setup, and 1.44% for the near field setup. We were also able to obtain a 2D elasticity map of a mouse tumor with better agreement with B-mode morphology compared to the conventional setup. Finally, large errors exist in the results from shear wave computed tomography. Possible sources of errors are discussed.
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