超音波技術探討血液濃度、血流、與血栓形成的關係

Studies on the relationship between blood concentration, blood flow, and formation of thrombus using ultrasonic techniques

黃群昇(Chun-Sheng Huang(aman))

指導教授 ： 王士豪

中原大學/工學院/醫學工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200071

摘要

血液在低流速或靜止時紅血球會產生聚集（Aggregation）現象，這個現象主要是因血漿中的大分子，如纖維蛋白（Fibrinogen）等所引起的。紅血球的聚集效應越強促使血液的黏度越大，血液流動也較易受到阻礙，可能導致血管栓塞病變的發生，所以關於血液聚集方面的特性一直被研究著。當血液在直且長的流管中流動，其流場會呈線流（Laminar flow）的流動形式，剪速率（shear rate）在管子中央最小，導致紅血球可能聚集在管子中央部分，這種現象可由文獻中所發現，管子中間部分的超音波散射訊號較兩邊還要強而得到驗證。
本研究將血液置入流管中流動一段時間後把馬達關閉，此時紅血球會因為剪速率消失而慢慢的聚集起來最後形成錢串（rouleau）的結構。使用超音波訊號來偵測此流體動力變化，結果顯示血液停止後超音波衰減係數變大、聲速變快和散射訊號的強度變大。實驗也發現當血液之血容比越小，則衰減係數的變化越大、聲速的變化也越大，而散射的變化則越小。若血流的流速越快則衰減係數和聲速的斜率皆越大。第二個研究是應用超音波散射、衰減和聲速這三種參數來偵測動、靜態血液之血栓形成。靜態血液的結果顯示血栓形成時會促使超音波衰減、聲速和散射增大。而動態血液中，血栓形成時超音波衰減、聲速和散射均同時發變化，且血液在流動的狀態下所形成的血栓體積比靜態血液中大，在血液凝固實驗中血容比越大則形成血栓時黏度變化越大。本研究結果顯示超音波可敏感的被用來偵測血液動力之變化。

關鍵字

血液 ； 超音波 ； 紅血球聚集 ； 血栓

並列摘要

The aggregation of red cells is formed when the blood flow is low or stopped. This phenomenon is primarily due to those large molecules, such as fibrinogen, in the plasma. The larger aggregation effect for red cells tends to increase higher viscosity of blood. Under such circumference, the blood flow would be hindered. Thus, it could finally lead to the formation of vascular embolism. For these reasons, the characteristics of red cells aggregation are still investigated to date. The laminar flow in a flow field might be found as the blood is flowing in a straight and long tube. The red cells aggregation will be distributed near the center stream of a tube due to that the corresponding location has the lowest shear rate. The phenomenon was validated from larger ultrasonic scattering signals in the centerline in a tube than those near the wall of a tube.
In this study, the blood was circulated in a flowing tube for a certain time and then the driven pump was turn off. The red cells were gradually aggregated and finally formed a rouleau structure. This flow variation was monitored by ultrasonic signals. Results showed that ultrasonic attenuation, sound velocity, and backscattered signals were increased after the stoppage of the blood flow. Experimental results also found that larger variations for attenuation and sound velocity were obtained associated with the decrease of blood hematocrit. However, the relation between hematocrit and backscattering was different. The rate of attenuation coefficient and sound velocity increased corresponding to higher blood flow.
The second study is on the application of ultrasonic backscattering, attenuation, and sound velocity to detect the formation of clot from blood under static and dynamic conditions. Results from both the static and dynamic blood demonstrated that three ultrasonic parameters were increased as the clot was formed. The volume of the clot is larger in the flowing blood than that in the static condition. The increasing variation of viscosity was found corresponding to the higher hematocrit. These results validated that ultrasound could be sensitively used to detect the variation of hemodynamic properties for a blood flow.

並列關鍵字

blood ； Ultrasound ； red cells aggregation ； clot

參考文獻

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