國立臺灣大學電機工程學系暨研究所李百祺2006-08-232018-07-062006-08-232018-07-061999-07-31http://ntur.lib.ntu.edu.tw//handle/246246/29472由有限振幅失真所產生之第二諧波訊 號以水聽筒測量並發現其聲場強度之分布 與探頭大小及聚焦深度有直接的關係。仿 體影像及電腦模擬亦顯示，動態發射聚焦 可以在不顯著影響影像對比之情形下大幅 提高第二諧波訊號之靈敏度。Generation of the second harmonic signal was studied for finite amplitude distortion based second harmonic imaging. Acoustic field amplitudes of a fixed focus transducer along the range axis were measured using a PVDF needle hydrophone. Results indicated that on-axis amplitudes strongly depended on the f-number at both the fundamental and the second harmonic frequencies. A two-focus transducer was also used. Gray scale imaging, hydrophone measurement and simulations were performed. Results of the study using the two-focus transducers can be generalized to imaging systems with full dynamic transmit focusing capabilities. It is expected that dynamic transmit focusing can improve the SNR of finite amplitude distortion based second harmonic imaging while improving the contrast resolution over fundamental imaging.application/pdf279399 bytesapplication/pdfzh-TW國立臺灣大學電機工程學系暨研究所超音波非線性影像多重聚焦UltrasoundNonlinear ImagingMultiple Zone Focusingreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/29472/1/882314B002216M08.pdf