以B-mode超音波影像序列和近似熵評估頸動脈彈性之研究

Assessment of Carotid Artery Distensibility Using Approximate Entropy and B-mode Ultrasound Image Series

黃俊傑(Chun-Chieh Huang)

指導教授 ： 劉偉名

國立中正大學/工學院/資訊工程學系/碩士(2014年)

摘要

世界衛生組織指出心血管疾病為目前全球頭號死因，且造成死亡的人數逐年攀升。而動脈硬化是導致許多心血管疾病的重要原因，臨床上越來越頻繁地使用動脈硬化程度做為心血管疾病的診斷指標。而頸動脈為提供大腦血液的主要通道，又是動脈硬化的好發部位，是臨床上預防中風的重點檢測部位。
頸動脈僅距離皮膚表面1~2公分，可透過超音波影像搭配操作者的經驗和技術檢查其管壁病變狀況。過去學者在發展局部性的評估動脈硬化上，大多僅考慮血管收縮和舒張時管腔截面積與血壓的瞬時變化，而這類方法因評估動脈硬化所使用的物理變化量會受諸多因素所影響，所以存在著根本性的問題而備受質疑。我們的目標是發展一套可供使用者方便取得血管長時間幾何資訊的影像處理工具，並以近似熵計算截面積在時間序列上的變化量，作為評估動脈彈性的指標。
實驗結果顯示，在擷取頸動脈連續影像截面積時，具有相當好的可靠性和一致性。在利用近似熵評估頸動脈彈性中，取樣頻率和資料量是必須固定的，而量測位置不影響估計結果。短時間的運動會造成動脈的彈性上升，其他學者使用主動脈脈波速度(APWV)時也發現了類似的現象。在量測可重複性實驗中，顯示有相當好的可重複性。在各項實驗中，我們與常用的統計測度 - 變異數相比較，結果顯示近似熵是更好且可靠的動脈彈性評估方法。

關鍵字

超音波影像 ； 彈性 ； 動脈硬化 ； 頸動脈 ； 近似熵

並列摘要

World Health Organization showed that cardiovascular disease is the main cause of death around the world, and the number of death is increasing every year. Atherosclerosis is an important factor that causes cardiovascular disease, and more and more clinical practices uses arterial stiffness to diagnose cardiovascular disease. The carotid artery is the main channel of blood supply to the brain, and also the predilection sites of atherosclerosis. Therefore it is an important diagnostic site to prevent stroke.
Carotid artery is only 1 to 2 cm below the skin surface, and the lesions on arterial wall can be assessed by ultrasound imaging plus the experience and skill of the operator. In the past the researchers only considered the instantaneous changes of lumen cross-section area and blood pressure between the systolic and diastolic period, which is fundamentally problematic and controversial because these changes are impressionable by many factors. Our objective is to develop an image processing tool that allows users to easily obtain the long term information of the arterial geometry, and quantify the temporal variation by approximate entropy in order to correlate with arterial distensibility.
Our experimental results show that the extracting cross-sectional area from carotid artery image series is reliable and consistent. The imaging rates and data length must be fixed when assessing arterial distensibility by approximate entropy. The site of imaging does not change the estimation results. The estimated arterial distensibility increased after short-term exercise. Other people showed the same phenomenon by using aortic pulse wave velocity (APWV). We also found such assessment is reproducible according to our repeated experiments. In all the experiments we compared approximate entropy with the common statistical measure, variance, and found approximate entropy is a better and convincing indicator for carotid atherosclerosis.

並列關鍵字

Ultrasound imaging ； Distensibility ； Arteriosclerosis ； Carotid artery ； Approximate entropy

參考文獻

[1] Damjanov, I. (2013). Pathology for the health professions, Elsevier Health Sciences.

[3] Epstein, F. H. and R. Ross (1999). "Atherosclerosis—an inflammatory disease." New England journal of medicine 340(2): 115-126.

[7] Mathers, C. D. and D. Loncar (2006). "Projections of global mortality and burden of disease from 2002 to 2030." PLoS medicine 3(11): e442.

[10] Laurent, S., J. Cockcroft, L. Van Bortel, P. Boutouyrie, C. Giannattasio, D. Hayoz, B. Pannier, C. Vlachopoulos, I. Wilkinson and H. Struijker-Boudier (2006). "Expert consensus document on arterial stiffness: methodological issues and clinical applications." European heart journal 27(21): 2588-2605.

[11] O’Rourke, M. F., J. A. Staessen, C. Vlachopoulos, D. Duprez and G. é. E. Plante (2002). "Clinical applications of arterial stiffness; definitions and reference values." American Journal of Hypertension 15(5): 426-444.