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MRI and MRA of the Carotid Arteries

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Presentation on theme: "MRI and MRA of the Carotid Arteries"— Presentation transcript:

1 MRI and MRA of the Carotid Arteries
Robert L. Greenman Department of Radiology Beth Israel Deaconess Medical Center

Review Pathogenesis/Progression Intima-Media Thickness (IMT) Studies Plaque Constituents Morphology Stable vs Unstable (Vulnerable) Survey of Methods and Results Most Published Results - 1.5T Recent 3T Carotid MRI Studies

Stroke (1999 Statistics) Worldwide 4.4 Million Deaths/Year 5,000 Disabilities/Million Persons United States 750,000 Strokes/Year 1/3 Stroke Patients Die 1/2 of Survivors are Disabled Gorelick, PB, et al Statement from National Stroke Assoc. JAMA 1999; 281:

Acute Ischemic Attack Disruption of Atherosclerotic Plaques Cause of many Embolic Strokes

5 ATHEROSCLEROSIS Intimal Disease Inflammatory Disease
Response of the Intima to Injury Ross, R. “Atherosclerosis - An Inflammatory Disease”. N Engl J Med 1999; 340: Davies, MJ, Woolf, N. “Atherosclerosis: what it is and why does it occur?. Br Heart J; 1993: 69;S 3-11

Major Components Lipids Lipid-Containing “Foam Cells” (Macrophages) Macrophages Connective Tissue Matrix Proteins - Collagen Strengthens, Holds Plaque Together Other Components Calcification

7 ATHEROGENESIS Endothelial Injury/Dysfunction
Lipids are a Major Cause of Injury Adhesion and Migration of Luekocytes Immune/Inflammatory Response Migration of Lipids (Normal and Oxidized) Uptake of Lipid by Macrophages Smooth Muscle Proliferation

8 ATHEROGENESIS Endothelial Injury/Dysfunction
Causes Elevated and Modified LDL Free Radicals Cigarette Smoking Hypertension Diabetes Genetic Alterations Infectious Microorganisms

9 ATHEROGENESIS Endothelial Injury/Dysfunction
Immune/Inflammatory Response Increased Adhesiveness Increased Permeability Procoagulant Properties Release of Growth Factors Thickening of Artery Wall and “Remodeling”

10 ATHEROGENESIS Plaque Formation
Modified Lipids Migrate Into Intima Ingested by Macrophages Uptake is Unregulated “Foam Cells” Smooth Muscle Proliferation and Migration Release of Growth Factors

11 ATHEROGENESIS Plaque Formation
Foam Cells Burst - Necrotic Lipid Core Smooth Muscle Proliferation Release of Growth Factors

12 ATHEROGENESIS Unstable (Vulnerable) Plaque
Necrotic Lipid Core Grows Large Fibrous Cap Wears Thin - Ruptures Thrombus

13 CAROTID PLAQUES Unstable (Vulnerable) Plaque
Large Core Necrotic Lipid Intraplaque Hemorrage Unstable Fibrous Cap

Modality of Choice: 2D Ultrasound B-mode Ultrasound Noninvasive Safe Inexpensive Measurements Intima-Media Thickness (IMT) Vessel Geometry Lumen Diameter Distensibility

15 CAROTID IMT MRI vs US Difficulties with Carotid US
Relative position of jawbone WRT bifurcation Vessel tortuosity Calcification Large Intra- and Interobserver Variability

Little MRA - Mostly MRI Soft Tissue Contrast Lipid, Smooth Muscle, Fibrous Tissue MR Signal Independent of Angle Flow Sensitive Simultaneous Information on: Vessel Lumen Vessel Wall

17 FSE Black Blood Imaging

18 T2-W FSE (Dark Blood)

Longitudinal Studies Study Progression of Atherosclerosis Risk Factor for Stroke ?? Risk Factor for Cardiovascular Disease ??

IMT and Brain Infarction Touboul, et al. Circulation 102: , 2000

IMT of Common Carotid Artery Some Studies Suggest IMT Related to Cardiovascular Risk Factors Prevalence of Atherosclerosis of Peripheral Coronary Femoral

Increased IMT Associated with Age Howard, et al Hypertension Zanchetti, et al Diabetes Kawamori, et al Hyperlipidemia Poli, et al Increased IMT Associated with CAD Crouse, et al. Circulation: 92: , 1995

Study: Risk Factors that Predict Stroke/MI Iglesias, et al. (Subset “Rotterdam Study”) 374 Subjects - Stroke or MI 1496 Controls Mean Follow-up: 4.2 years Results/Conclusions Significant association between Carotid IMT and Stroke and MI Predictive Value Low When Combined With Other Clinical Observations Iglesias, et al. Stroke: 32: , 2001

24 CAROTID IMT MRI vs US MRI Studies of IMT Measurement Results
Crowe, et al. JMRI: 21: , 2005 2D US vs 3D MRI (Black-Blood TSE) 10 Healthy Subjects, 5 Hypertensive Patients Results Bland-Altman Analysis Mean Diff. MRI & US - 1.2% Significant Difference in IMT (P<0.05) Between Hypertensive &Non-Hypertensive for Both Methods

25 CAROTID IMT MRI vs US Wall Thickness Measurements
3D-TSE MRI vs US Crowe, et al, 2005 JMRI;21:

26 CAROTID IMT MRI vs US Crowe, et al, 2005 JMRI;21:282-289
Wall Thickness Measurements 3D-TSE MRI vs US Crowe, et al, 2005 JMRI;21:

27 CAROTID IMT MRI vs US Correlation Study DIR Black Blood MRI vs US
17 Patients Intermediate/High Framingham Cardiovascular Risk Score Results Significant Correlation R = 0.72, p < 0.05 Mani, et al. J Cardiovasc Magn R 8:

28 CAROTID CE-MRA Identifies Luminal Narrowing Not Plaque Size
100% Sensitivity 92% Specificity Compare to Conventional MRA Wutke, et al. Stroke 33: Not Plaque Size Vessel May Remodel Can Overestimate Extent of Stenosis

29 Image of the entire vascular region from the aortic arch to the intracranial vessels
Wutke, R. et al. Stroke 2002;33: Copyright ©2002 American Heart Association

30 MRI of CAROTID PLAQUES Non-Invasive MRI Signal Intensities
Based on Tissue Biochemical Environment Soft Tissue Contrast Lipid vs Smooth Muscle, Fibrous Tissue Vessel wall/Lumen Contrast Flexibility in Achieving Desired Contrast

31 MRI of CAROTID PLAQUES Dark Blood Sequences Bright Blood Sequences
T2-Weighted T1-Weighted PD- Weighting (Proton Density) Bright Blood Sequences 2D and 3D Time-of-Flight (TOF) Others Magnetization Transfer (MT) Diffusion Sensitive

32 MRI of CAROTID PLAQUES MRI Contrast of Atherosclerotic Plaque
Yuan, C, et al. Radiology 2001; 221:

33 MRI of CAROTID PLAQUES MRI Contrast Mechanisms Identification of:
Lipid Core Calcium Deposits Fibrous Connective Tissue Intraplaque Hemorrhage

34 1.5T MRI STUDIES Multiple Weightings – T2W, T1W, PDW
Shinnar, et al. Arterioscler Thromb Vasc Biol 1999;19: Yuan, et al. Radiology 2001; 221: Fibrous Cap Thickness Measurement Hatsukami, et al. Circulation 2000;102: Contrast Enhanced Yuan, et al. J Magn Reson Imaging 2002; 15:62-67

35 MRI of CAROTID PLAQUES T2-Weighting Delineates Lipid Core and Thrombus
Yuan, C, et al. Radiology 2001; 221:

36 MRI of CAROTID PLAQUES Multiple-Weighting Study
Mitsumori, L, et al. JMRI :

37 MRI of CAROTID PLAQUES Multiple-Weighting Study Lipid Core/Fibrous Cap
Mitsumori, L, et al. JMRI :

38 MRI of CAROTID PLAQUES Multiple-Weighting Study
Pitfall of DIR-BB FSE studies Mitsumori, L, et al. JMRI :

39 MRI of CAROTID PLAQUES Multiple-Weighting Study Calcification
Mitsumori, L, et al. JMRI :

40 MRI of CAROTID PLAQUES 3D TOF (Bright Blood) Imaging Parameters:
Bright Lumen/Dark Fibrous Tissue Identify Unstable Fibrous Caps in vivo Imaging Parameters: TR = 23 ms TE = 3.8 ms 2 Signal Averages Scan Time = Min.

41 MRI of CAROTID PLAQUES 3D TOF (Bright Blood) Spatial Resolution
Slice Thickness = 2 mm Acquisition Matrix: Size = 256 x 256 Voxel Size = 0.5 x 0.5 x 2 mm Zero Filled: Matrix = 512 x 512 Zero Filled Voxel Size = 0.25 x 0.25 x 2 mm

42 MRI of CAROTID PLAQUES 3D TOF (Bright Blood)
Unstable Fibrous Cap Detection Yuan, C, et al. Radiology 2001; 221:

43 MRI of Neovasculature Neovasculature in Plaques Associated with
Infiltration of Inflammatory Cells Plaque Destabilization Involved In Recruitment of Leukocytes Inflammatory Cells Present at Rupture Sites Measurement of Neovasculature may Identify Vulnerable Plaques Contrast-Enhanced MRI

44 MRI of Neovasculature MRI of Neovasculature
Kerwin, et al. Circulation 107:

45 1.5T to 3.0T Comparisons All Studies Evaluated Black-Blood
Anumula, et al, Acad Radiol; : Compared Multi-coil Arrays Univ. Pennsylvania (FW Wehrli) Yarnykh, et al, JMRI; : Compared Multicontrast Univ. Washington (C. Yuan) Koktzoglou, et al,JMRI; : Compared Multi-slice Northwestern & Mt Sinai (L Debiao, ZA Fayad) Greenman, et al. MRI 2007 In Press Vessel Wall Sharpness with Field Strength and Spatial Resolution

46 1.5T to 3.0T Comparisons Conclusions of studies 3.0T Improves
SNR CNR SNR can be traded for higher spatial resolution

47 Purpose Apply Edge Detection to Evaluate effect of
Spatial Resolution Static Field Strength Carotid Imaging Methods: 2D-TOF (GRE) 2D Black-Blood (Double-IR FSE)

48 Edge Detection Have Been Used to Evaluate and Compare Vessel Edge Definition Coronary Arteries (Bright Blood) Compare Results of Acquisition Schemes Deriche Algorithm First-order derivative Create derivative or “edge” images Vessel sharpness: “The average edge value along the calculated vessel border” … “Higher edge values correspond to better vessel definition.” Botnar, et al, Circulation 1999;99: Weber, et al, JMRI 2004;20: Deriche, R, IEEE Trans PAMI. 1990;12:78-87 (“Fast algorithms for low-level vision”)

49 METHODS Compared Spatial Resolution/Field Strength:
0.27 mm X 0.27 mm X 2.0 mm 1.5T and 3.0T; n = 12 (1.5T-H, 3.0T-H) 0.55 mm x 0.55 mm x 2.0 mm (Zero-Filled 2X) 1.5T only; n= 5 (1.5T-L) 2D DIR Black Blood FSE 2D Gradient Echo Time-of-Flight

50 2D-TOF Results

51 DIR-BB Results

52 Gradient Value Comparison

53 Carotid Edge Values

54 MRI of CAROTID PLAQUES Identify Stable/Unstable Plaques
Follow Progression of Plaque Development Monitor Therapies

55 CONCLUSIONS 3.0 Tesla MRI Offers Improved Signal-to-Noise Ratio – Resolution IMT Measurements May Be Able To Identify Unstable Plaques Improved Accuracy: Measurement Cap Thickness May Improve Monitoring of Interventional Therapies

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