鼠腦中風模型磁敏感影像

Susceptibility Weighted Imaging in Rat Stroke Model

曾浚翔(Jiun-Siang Tzeng)

指導教授 ： 饒若琪

高雄醫學大學/健康科學院/醫學影像暨放射科學系碩士班/碩士(2015年)

摘要

腦中風為一種腦血管疾病，當腦動脈血管被阻斷，腦組織因缺乏氧氣與養分而導致腦功能的受損。全世界每年死於中風的患者有數百萬人。其中以缺血性腦中風患者占大多數，在台灣則為國人十大死因之一。因此，發展一可迅速檢測及診斷腦中風的技術是現代醫學上一個重要的課題。磁振造影(Magnetic resonance imaging, MRI)為一非侵入式且無游離輻射之影像檢查技術，常應用於臨床中風檢測，此技術對缺血性腦中風有很高的靈敏度及特異性。本研究建立之鼠腦缺血性腦中風模型係於SD大白鼠右側頸動脈進行栓塞，導致中大腦動脈之血流阻斷，隨後，藉由不同的磁振造影脈衝序列來觀察中風鼠腦隨時間之變化情形。研究使用三維飛越時間磁振血管造影(3D Time-of-flight magnetic resonance angiography, 3D TOF MRA)、T2快速自旋回訊(Turbo spin echo, TSE)與磁敏感加權影像(Susceptibility weighted imaging, SWI) 脈衝序列進行縱向評估鼠腦部結構變化及正常與中風區域訊號之差異。SWI為近年來新發展的磁振造影技術，其成像原理係使用不同組織間磁化率的差異來產生高對比影像。SWI對於靜脈血流、出血及鐵積蓄有很高的靈敏性，目前常用於檢測腫瘤、中風與出血等臨床診斷與研究。
研究結果顯示於3D TOF MRA影像上右側頸動脈無訊號呈現，證實栓塞手術成功阻斷血流;手術後一至三天中風區因水腫造成T2 TSE影像上呈現高訊號，與對側對應區域有顯著差異，而於SWI影像上則無明顯差異。於術後一星期，由於中風腦組織產生壞死，於SWI影像上可觀察到中風區域有明顯訊號下降，顯示SWI對於壞死腦組織的敏感度較高，且影像上壞死區域之輪廓較其它脈衝序列的影像清晰，隱含SWI具有檢測中風壞死時間點的潛力。本研究藉由使用不同磁振造影序列長期縱向觀察鼠腦中風後造成腦組織傷害之過程。

關鍵字

鼠腦中風模型 ； 磁振造影 ； 三維飛越時間磁振血管造影 ； 磁敏感加權影像

並列摘要

Stroke is a cerebrovascular disease. The brain malfunction may result from oxygen and nutrient deficiency when the cerebral blood flow of artery is blocked. Several million people die from stoke every year in the world. Stoke is one of leading cause of death in Taiwan, and the majority of stroke patients are ischemic stroke patients. Hence, to develop a strategy that can rapidly detect and diagnose stroke becomes an important issue in modern medicine. Magnetic resonance imaging (MRI) is a non-invasive and non-radioactive medical imaging technique, which is usually used to diagnose stroke in clinical examinations. MRI possesses high sensitivity and specificity in diagnosing stroke diseases. Rat brain ischemic stroke model with right carotid artery occlusion was proposed in this study, which resulted in occlusion of the middle cerebral artery. Afterwards, MRI was performed to longitudinally investigate the time-course brain structures and signal changes in rat brain by various pulse sequences.
Three dimensional time-of-flight magnetic resonance angiography (3D TOF MRA), T2 turbo spin echo (T2 TSE) and susceptibility weighted imaging (SWI) pulse sequences were used to evaluate the time-course brain structures and signal changes between stoke and control regions of rat brain longitudinally. SWI is a newly developed MRI technique, which can produce high contrast images based on the magnetic susceptibility differences among various tissues. SWI has high sensitivity to venous blood flow, hemorrhage and iron storage. It has been frequently applied to detect tumor, stroke and hemorrhage in clinical diagnosis and research.
The results showed that the right carotid artery had signal void on 3D TOF MRA image. It inferred that the blood flow was blocked after occlusion surgery. The signal intensity of the stoke region appeared to be significantly higher than that of contralateral region on T2 TSE images due to edema formation within the first to third days after surgery, however, there is no significant differences on bilateral brain of SWI images. The stoke region appears to have significant signal loss on SWI images at one week after surgery. It might suggest that necrosis was formed in stoke region. Among various MRI pulse sequences, SWI showed higher sensitivity to necrosis tissue and clearer necrosis boundary than the others. Therefore, SWI shows potential in detecting the time point when necrosis occurs. The purpose of this study is long-term longitudinal evaluation of the rat brain injury progression after stroke by using various MRI pulse sequences.

並列關鍵字

Rat Stroke Model ； MRI ； 3D TOF MRA ； Susceptibility Weighted Imaging

參考文獻

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2.腦血管疾病介紹。http://www.cch.org.tw/cchhec/knowledge_detail.aspx?oid=128

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