- 學位論文
研製超音波都卜勒系統與其應用於 血液動力之初步研究
Development of an ultrasound Doppler system and its application in preliminary hemodynamics study
摘要
現今臨床診斷血液中栓子(Emboli)的形成多數是使用超音波影像，當栓子尺寸小於超音波波長時，栓子產生的散射訊號不易被偵測，而失去早期發現栓子形成的契機。若能量化微小血塊的逆散射訊號以早期偵測血塊的形成，將為心臟血管疾病的診斷提供莫大幫助。 本研究嘗試用超音波都卜勒功率(Doppler power)來預測血塊形成，且初步探討血液動力之研究。首先自製10MHz脈衝式都卜勒超音波系統，主要線路是使用高頻與高速電子元件，包括超音波換能器激發接收、解調、濾波與取樣保持等功能，類比都卜勒訊號經數位轉換後由個人電腦分析計算。透過軟體模擬與假體實驗量測不同粒子大小之液體的都卜勒功率與流速，驗證本系統之可行性與穩定度。探討血液之流速與都卜勒功率等特性，使用不同血容比3至40%的紅血球懸浮液與全血在四種不同流速12.7至30.9cm/s。同時在血容比為25至55%的全血中加入CaCl2使血液凝固形成血塊，連續偵測其都卜勒功率60分鐘。 假體實驗結果顯示粒子大小與濃度較大之液體其都卜勒功率較強且流速較低。血液實驗結果顯示在四種流速下紅血球懸浮液其都卜勒功率隨血容比之增加產生先上升後下降之現象，峰值出現在9%血容比。全血部分，峰值則出現在15%。可能是因黏度的改變，全血流速隨血容比的增加而下降。硬體系統與軟體模擬獲得一致的結果。血液凝固實驗結果顯示，加入CaCl2時，使都卜勒功率下降約2dB，當血塊形成時都卜勒功率則上升約5dB，且其上升斜率與血容比增加成反比。由上述結果顯示都卜勒超音波可敏感的偵測血塊形成，提供早期診斷栓子形成的依據。
並列摘要
To data, the formation of emboli in the blood was diagnosed clinically applying the ultrasound image. As the emboli size small than ultrasonic wavelength, the scattering signals corresponding to the emboli are not easily to be detected. As a result, it is going to loss a chance of early detection for the emboli formation. Therefore, it might provide a significant help in the diagnosis of cardiovascular diseases if the backscattered signals associated with those small clots could be quantified. This study attempted to detect the clot formation and to preliminarily explore the hemodynamics using the ultrasound Doppler power. A 10MHz pulsed Doppler ultrasound system was developed, in which those primary circuits using high frequency and high speed electronic devices include functions for excitation and reception the ultrasonic transducer, demodulation, filtering, and sample-and-hold. The analog Doppler signals were digitized and transferred into a personal computer for further analysis and calculation. The feasibility and stability of the developed system was validated by software simulation and experimental measurements of Doppler power and flow velocity from fluidic phantoms of different particle sizes. To explore the properties of blood at different flow velocities and Doppler powers, we utilize red cell suspensions and whole blood at different hematocrits ranged from 3 to 40% under four different flow velocities ranged form 12.7 to 30.9cm/s. Moreover, whole blood of different hematocrits ranged from 25 to 55% was added with a certain amount of calcium chloride (CaCl2) to induce the formation of clot. The process of clot formation was monitored by continuously measurements of Doppler power for 60 minutes. The experimental results of phantoms demonstrated that the fluid of larger size and concentration of particles tended to have higher Doppler power and slower flow. Results obtained from red cell suspensions under four different flow velocities showed that as hematocrits were progressively increased the corresponding Doppler power tended to increase first and then to decrease with the peak Doppler power at 9% hematocrit. Similar results were found for the whole blood except that the peak Doppler power was at around 15% hematocrit. Moreover, it could be due to changes of viscosity in the whole blood, the blood flow was decreased associated with the increase of hematocits. Consistent results were obtained from both measurements by the hardware system and the flow software simulation. Results of blood coagulation experiments demonstrated that the Doppler power tended to decrease to 2 dB as calcium chloride was initially added. The Doppler power was increased to approximately 5 dB as the clot was formed, in which its increasing slope was inversely proportional to the increase of hematocrits. All these above results showed that Doppler ultrasound could be a sensitive modality to detect the clot formation for early diagnosing the formation of emboli.