研發超音波系統以測量心輸出量之研究

A study on the development of an ultrasonic system to measure cardiac output

洪煥昇(Huan-Sheng Hung)

指導教授 ： 王士豪

中原大學/工學院/醫學工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400780

摘要

臨床上剛進行心臟手術後的病人經常發現的臨床問題是低血壓(心臟血液輸出量低於全身脈管阻力)，對於這些循環疾病高危險群的病人則必須更加詳細了解其血液循環的狀態。量測心臟血液輸出量(心輸出量)多以插入心導管的方式進行體內測量，而近年來大多學者開始研究以非侵入式的心輸出量測量方法，例如以指示劑稀釋法、超音波都卜勒法等測量方法。
有別於傳統超音波都卜勒測量流量方式，本論文以時域訊號測量流量，設計開發一套超音波量測血液流量系統；主要硬體電路包含5 MHz超音波激發接收電路、訊號數位化與介面傳輸電路等，軟體程式可進行訊號分析、即時顯示等。並且透過流管實驗驗證本系統之可行性與穩定性，並且使用不同血容比25 %至55 %在流量62 ml/min 至437 ml/min，探討血容比與流量的關係。
實驗結果中，本量測系統對於液體密度變化的靈敏度為5.38，具有0.99的線性相關係數，並和美國Stanford Research Systems公司出產的SR844 RF Lock-In Amplifier儀器測量之結果有相似的趨勢。動態實驗結果中，注射劑的體積和濃度正比動態曲線下的面積。血容比高所量測的流量會相對小於血容比低的流量值，因為血容比高表示紅血球的密度大，導致黏度增加流量降低。

關鍵字

血液流量 ； 超音波量測 ； 低血壓 ； 心輸出量

並列摘要

The patients after cardiac surgery often suffer from clinical problems associated with low blood pressure. The conditions of blood circulation for these patients having dangerous diseases relative to circulations should be thoroughly extracted and analyzed. In the past, the cardiac output was frequently measured by using the catheter inserted in a heart, and however, many researchers recently began to investigate the non-invasive approaches for the measurement of cardiac output, such as indicator dilution, Doppler ultrasound, and so forth.
Compared to the traditional method based on Doppler ultrasound, this study developed an ultrasonic system to measure the flow by using ultrasonic signals in time-domain. The system was consisted of a 5 MHz ultrasonic pulser/receiver, an analog-to-digital converter, and an interface circuits. A software corresponding to the system was capable of real-time signal analysis and display. The feasibility and stability of the system was evaluated using the experiments on flowing blood in a tube that the range for the hematocrit and the flow is from 25% to 55% and from 62 ml/min to 437 ml/min, respectively. The relationship between hematocrit and flow was also explored.
The results obtained from the flow experiments showed that the sensitivity of the measurement system to detect the variation of density was 5.38 corresponding to a correlation coefficient of 0.99 with those obtained from the measurement using the lock-in amplifier (SR844RF, Stanford Research Systems, USA). The experimental results also showed that both the volume and concentration of the indicator is proportional to the area of measurement of the curve. Moreover, the measured flow for higher hematocrits would be smaller than those from lower hematocrits. This is due to that the density of blood cell at high hematocrit is large, resulting in the increase of viscosity and the decrease of flow. This study concluded that this non-invasive ultrasonic measurement system has a high sensitivity to be helpful for the measurement of cardiac output in the clinical diagnosis.

並列關鍵字

Ultrasonic system ； Blood flow ； Cardiac output

參考文獻

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