臺灣博碩士論文加值系統

背景及目的：缺血性腦中風(Ischemic Stroke)是台灣常見的腦血管疾病，而電腦斷層灌注成像(Computed Tomography Perfusion, CTP)是評估腦血流灌注狀況的重要工具。然而，傳統CTP掃描輻射劑量高，長期累積可能增加患者罹患癌症的風險。本研究旨在通過降低管電流（mAs）並使用先進的影像重建技術，探討低劑量電腦斷層腦血流灌注造影（Low-Dose computed tomography perfusion, LDCTP）在缺血性腦中風診斷中的應用及其對影像品質的影響。

材料與方法：本研究共納入30名缺血性腦中風患者，使用Canon Aquilion ONE 640 CT掃描儀進行CTP掃描。將管電流從標準的100mA降低至50mA，有效mAs設定為37mAs。比較降低劑量前後CTP的電腦斷層劑量指標(CT Dose Index Volume, CTDIvol)和劑量長度乘積(Dose Length Product, DLP)值，並使用AIDR 3D (Adaptive Iterative Dose Reduction 3D)、AiCE(Advanced Intelligent Clear-IQ Engine)和FIRST(Forward projected model-based Iterative Reconstruction SoluTion)三種技術對影像進行重建。評估不同影像重建技術對LDCTP影像的對比雜訊比(Contrast-to-Noise Ratio, CNR)和訊雜比(Signal-to-Noise Ratio, SNR)的影響。

結果：降低管電流後，CTP的CTDIvol和DLP值分別降低了70%，顯示出明顯的輻射劑量減少。在影像品質方面，使用AiCE影像重建技術的LDCTP影像在CNR和SNR上均顯著優於使用AIDR 3D和FIRST的影像。此外，AiCE重建的影像在保留診斷細節的同時，有效降低了影像雜訊，並且提供最快速的診斷效率。

結論：本研究證實，降低管電流配合先進的影像重建技術，能夠在顯著降低輻射劑量的同時保持CTP影像的診斷品質。AiCE影像重建技術在低劑量CTP影像重建中表現出較佳的影像品質且快速的影像重建效率，為缺血性腦中風的診斷提供了一種更安全、有效的影像評估方法。

關鍵詞：缺血性腦中風、CT灌注成像、影像重建技術、AIDR 3D、AiCE、FIRST、對比雜訊比、訊雜比、輻射劑量、電腦斷層劑量指標、劑量長度乘積

Background and Purpose: Ischemic stroke is a common cerebrovascular disease in Taiwan, and computed tomography perfusion (CTP) imaging is a vital tool for assessing cerebral blood flow. However, traditional CTP scans involve high radiation doses, which may increase the risk of cancer with long-term accumulation. This study aims to explore the application of low-dose computed tomography perfusion (LDCTP) in the diagnosis of ischemic stroke and its impact on image quality by reducing the tube current (mAs) and utilizing advanced image Reconstruction techniques.

Materials and Methods: This study included 30 patients with ischemic stroke who underwent CTP scans using the Canon Aquilion ONE 640 CT scanner. The tube current was reduced from the standard 100mA to 50mA, with an effective mAs of 37mAs. We compared the CT dose index volume (CTDIvol) and dose-length product (DLP) values before and after dose reduction. The CT images were reconstructed using three reconstruction techniques: AIDR 3D (Adaptive Iterative Dose Reduction 3D), AiCE (Advanced Intelligent Clear-IQ Engine), and FIRST (Forward projected model-based Iterative Reconstruction SoluTion). The effects of different reconstruction techniques on the contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of LDCTP images were assessed.

Results: After reducing the tube current, CTP's CTDIvol and DLP values decreased by 40%, indicating a significant reduction in radiation dose. In terms of image quality, LDCTP images reconstructed with the AiCE technique showed significantly better CNR and SNR compared to those with AIDR 3D and FIRST. Furthermore, images reconstructed with AiCE effectively reduced image noise while retaining diagnostic details.
Conclusion: The study confirms that reducing the tube current in conjunction with advanced image reconstruction techniques can significantly lower radiation dose while maintaining the diagnostic quality of CTP images. The AiCE technology demonstrates superior image quality in low-dose CTP image reconstruction, offering a safer and more effective imaging assessment method for the diagnosis of ischemic stroke.

Keywords: Ischemic Stroke, CT Perfusion Imaging, Image Reconstruction Techniques, AIDR 3D, AiCE, FIRST, Contrast-to-Noise Ratio, Signal-to-Noise Ratio, Radiation Dose, CT Dose Index Volume, Dose Length Product.

中文摘要 I
英文摘要 II
致謝 V

第一章 研究與背景 2
1-1 缺血性腦中風成因與現況 2
1-2 傳統的影像重建技術和發展限制 3
1-3 CT影像技術的進步：硬體設備提升和影像重建技術的演進 4
1-4 結合先進的影像重建技術，優化影像品質 4
1-5 本研究的目的 5

第二章 材料與方法 6
2-1資料收集 6
2-2 研究流程與掃描參數 6
2-3 傳統劑量與低劑量之比較 8
2-4 定量分析 9
2-5 定性分析 11
4.整體影像品質 11
2-6 統計分析 12
2-7 低劑量CTP檢查的優勢 12

第三章 結果 13
3-1 統計分析結果之定量分析 13
3-2 統計分析結果之定性分析 15
3-3 影像重建時間的比較 16

第四章 討論 17

第五章 結論 19

參考文獻 20

圖目錄
圖1：CTP掃描起點為顱底(skull base)至顱頂(vertex) 6
圖2：平均血管值測量位置示意圖 9
圖3：背景信號測量位置示意圖 10

表目錄
表1：傳統方式掃描劑量與低劑量對比條件參考表 8
表2：變異數同質性檢定(Levene’s test)與單因子變異數分析(ANOVA) 13
表3：依變數: CNR 14
表4：依變數: SNR 14
表5：定性比較三種 CT 影像的重建技術之影像品質 15
表6：觀察者間一致性和觀察者內一致性評分之結果 16

1.Bum J.K, et al. Ischemic Stroke Subtype Classification: An Asian Viewpoint. Journal of Stroke 2014; 16(1): 8-17
2.Chen YW, Sung SF, Hung C, et al. IntravenousThrombolysis Administration 3–4.5 h After Acute Ischemic Stroke: A Retrospective, Multicenter Study. Front Neurol, 2019; 10: 1038-1042
3.Matthew RB, Phil White, Peter Cowley, et al. Revolution in acute ischaemic stroke care: a practical guide to mechanical thrombectomy. Pract Neurol, 2017; 17: 252-265.
4.deLucas EM, Sanchez E, Gutierrez A, et al. CT protocol for acute stroke: tips and tricks for general radiologists. Radiographics, 2008; 28: 1673- 87
5.Neurological Disorders and Stroke rt-PA Stroke Study Group, Tissue plasminogen activator for acute ischemic stroke. The National Institute of. N Engl J Med, 1995; 333: 1581-1587
6.Dzialowski I, Hill MD, Coutts SB, et al. Extent of early ischemic changes on computed tomography (CT) before thrombolysis: prognostic value of the Alberta Stroke Program Early CT Score in ECASS II. Stroke, 2006; 37: 973-978
7.Furlan A, Higashida R, Wechsler L, et al. Intra-arterial prourokinase for acute ischemic stroke: the PROACT II study—a randomized controlled trial. Prolyse in Acute Cerebral Thromboembolism. JAMA 1999; 282: 2003-2011
8.Amanda M, Aaron S, Lee TY, et al. Low dose CT perfusion in acute ischemic stroke. Neuroradiology, 2014; 56: 1055-1062
9.Martin J.W, et al. The evolution of image reconstruction for CT—from filtered back projection to artificial intelligence. European Radiology 2019; 29(5): 2185–2195
10.Angélique B, et al. Deep learning reconstruction versus iterative reconstruction for cardiac CT angiography in a stroke imaging protocol: reduced radiation dose and improved image quality. Quant Imaging Med Surg 2021; 11(1): 392-401
11.Stephanie L, et al. Comparison of CT image quality between the AIDR 3D and FIRST iterative reconstruction algorithms: an assessment based on phantom measurements and clinical images. Phys Med Biol 2021 Jun 7; 66(12).
12.A.A. Konstas, et al. Theoretic Basis and Technical Implementations of CT Perfusion in Acute Ischemic Stroke, Part 2: Technical Implementations. American Journal of Neuroradiology May 2009, 30 (5) 885-892;
13.M. Wintermark, et al. FDA Investigates the Safety of Brain Perfusion CT. AJNR Am J Neuroradiol. 2010 Jan; 31(1): 2–3.
14.Xaoling W, et al. Ultra-low-dose multiphase CT angiography derived from CT perfusion data in patients with middle cerebral artery stenosis. Neuroradiology (2020) 62:167–174
15.Radiation dose reduction in perfusion CT imaging of the brain using a 256-slice CT 80 mAs versus 160 mAs
16.Isabelle R, Claus Z, Daniela P, et al. Radiation dose reduction in perfusion CT imaging of the brain using a 256-slice CT. Clinical Imaging, 2018; 50: 188-193
17.Amanda M, Aaron S, Lee TY, et al. Low dose CT perfusion in acute ischemic stroke. Neuroradiology, 2014; 56: 1055-1062
18.Brady L, et al. RAPID Automated CT Perfusion in Clinical Practice. NOVEMBER/DECEMBER 2019 PRACTICAL NEUROLOGY 39: 38-50
19.Ahmed EO, Carolin B, Zepa Y, et al. Effects of radiation dose reduction in Volume Perfusion CT imaging of acute ischemic stroke. European Radiology, 2015; 28: 3415- 3422
20.Lifeng Y. et al. Radiation dose reduction in computed tomography: techniques and future perspective, Imaging Med. 2009 Oct;1(1):65-84.