研製寬頻醫用超音波脈波發射器

Development of Broadband Biomedical Ultrasonic Pulser

蔡志峰(Chih-Feng Tsai)

指導教授 ： 婁世亮

中原大學/工學院/生物醫學工程研究所/碩士(2011年)

https://doi.org/10.6840/cycu201101098

摘要

超音波因具有非侵入且無放射性的優點，深受臨床醫學之重用。脈波發射器是超音波系統至關重要的子系統，它的功能性愈強，其所整合的醫用超音波系統愈實用，本研究乃以研製寬頻超音波脈波發射器為目標。脈波發射器是以高速微處理器為控制核心，主要的硬體包括電源管理、基頻產生電路、脈衝重複週期(pulse repeat frequency, PRF)/Gate控制電路、正負高壓調控電路、超音波激發電路等，這些硬體之參數皆可數位調控。所完成之發射器分別接合5-和10-MHz之換能器進行咖啡粉及牛奶粉溶於水之假體測試。以變數如：粉粒大小、溶液濃度及流速探討發射器所接獲逆散射訊號之對應變化，藉此確認發射器之功能性。發射器可產生基頻脈波1~25 MHz，雙極脈衝2~250個和PRF頻率100 Hz~50 kHz；內建正負電壓系統可產生10~65 Vpp之脈衝振幅，足以驅動換能器。以5-MHz換能器測試時，咖啡及牛奶的逆散射訊號分別為35.8~39.7及33.6~37.4，在10-MHz測試得的結果則分別為28.8~34.9及27.6~33.1。流速測試則是在19.9, 46.0 和70.8 cm/s下進行，在使用5-及10-MHz換能器測試之時，逆散射訊號分別為18.8~15.2及10.3~7.4。以上結果與研究預期一致，當溶液所含之粒子大小愈大或濃度愈高，所偵測得的逆散射訊號即愈大；當溶液濃度和粒子大小固定，流速愈慢，逆散射訊號愈大。就以上之研究探討結果而論，本課題所研發完成之寬頻超音波脈波發射器都有達成預設功能目標，具有發展成為醫用超音波系統的潛能。

關鍵字

超音波 ； 脈波發射器 ； 寬頻 ； 逆散射訊號

並列摘要

Ultrasound technology featuring non-invasive and non-ionizing radiation has been widely accepted for clinical uses. In an ultrasound system pulser is a key component. The pulser’s functionality more powerful, the ultrasound system is more useful. This study, thus, aims to develop a broadband pulser to be integrated with ultrasound systems so that they can be more practical for medical applications.
The pulser developed in this work is a high speed pipelined microcontroller based system. It involves lots of circuit design and development such as a power manager, a base frequency generator, a PRF/Gate signal generator, a bipolar high voltage adjustable generator, an ultrasound transducer burst driver etc. All of the controlled parameters are digitally adjustable. To be a functional unit, the pulser was coupled with ultrasound transducers to perform the designed experiments. In this work, the transducers of 5- and 10-MHz were used. The feasibility and applicability of the developed pulser was validated by experimental measurements of backscattered signals with two fluidic phantoms: coffee and milk solutions. The experiments focused on the backscattered signal responses with respect to the variation of the powder size, the solution concentration and the flow velocity.
The system validation results indicated that the pulser can produce base frequency pulses of 1-25 MHz, bipolar pulses of 2-250 cycles, and pulse repeat frequency between 100 Hz and 50 kHz. The built-in bipolar voltage system is able to generate voltage amplitude in the range from 10 to 65 Vpp, which is sufficient to drive ultrasound transducers. When the transducer of 5-MHz was used, the detected backscattered signals of the coffee and the milk solutions, which were prepared with a fixed concentration, were 35.8~39.7 and 33.6~37.4, respectively. The same study was performed with the transducer of 10-MHz; and the backscattered signals reduced to 28.8~34.9 and 27.6~33.1 for the coffee and the milk solutions, respectively. For the flow velocity study, the backscattered signals detected by the pulser coupled with the 5- and the 10-MHz transducers were 18.8~15.2 and 10.3~7.4, respectively. The aforementioned results are coherent to the study expectance. The fluid containing larger and higher concentration particles tends to have higher backscattered signals. For the fluid having same particles at a fixed concentration, the slower flow velocity is the detected backscattered signals are more significant. In conclusion, the developed broadband pulser has a great potential to become a medical ultrasound system.

並列關鍵字

Backscattered signal ； Broadband ； Pulser ； Ultrasound

參考文獻

13.吳志仁 民國九十五年六月,利用超音波技術評估阿基里斯腱特性

18.黃執中 民國九十二年七月, 研製超音波都卜勒系統與其應用於血液動力之初步研究

4.Xiaochen Xu, Jesse T. yen and K.Kirk Shung, 〝A Low-Cost Bipolar Pulse Generator for High-Frequency Ultrasound Applications,〞IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 54, no. 2, pp.443-447, Feb. 2007.

3.Jeremy A. Brown and Geoffrey R. Lockwood, 〝A Low-Cost, High-Performance Pulse Generator for Ultrasound Imaging,〞IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 49, no. 6, pp.848-851, June 2002.

5.L. Serpe and J. Y. Rho, 〝The Nonlinear Transition Period of Broadband Ultrasound Attenuation as Bone Density Veries,〞J. Biomechanics, vol. 29, pp. 963-966, 1996.