1) High resolution MRI using carotid phased array coils can image fine structures like plaque caps and provide multi-contrast images of atherosclerotic carotid plaques. 2) Quantitative analysis of MRI images can measure morphological indexes like wall thickness and plaque volume with precision. MRI can also characterize plaque components like fibrous caps, lipid cores, calcium, and hemorrhage. 3) Thin or ruptured fibrous caps are associated with symptoms while thick caps confer less risk. Perfusion MRI with contrast agents can assess microvessels associated with plaque instability.

1. MR Imaging of Atherosclerosis:MR Imaging of Atherosclerosis:
The Seattle ExperienceThe Seattle Experience
University of Washington
Chun Yuan, Ph.D.
Thomas S. Hatsukami, M.D.

2. Human Carotid Plaque
The First High Resolution Carotid 1.5 T MRI by Yuan et al
June 1998

3. The First High Resolution CarotidThe First High Resolution Carotid
ImagingImaging by a 3T MRIby a 3T MRI
Fine structures like plaque cap now can be imaged.
May 2003

4. 1.5 T; 2 NEX; resolution 0.63x0.63 mm 3 T; 2 NEX; resolution 0.63x0.63 mm
3 T; 1 NEX; resolution 0.27x0.55 mm1.5 T; 1 NEX; resolution 0.27x0.55 mm
Comparing 1.5 and 3TComparing 1.5 and 3T
without Software Enhancementwithout Software Enhancement
GE 3T and 1.5T Scanners with Identical Phased-array Design

5. Carotid ArteryCarotid Artery
AtherosclerosisAtherosclerosis
• Stroke/TIA
• Location
• Carotid
endarterectomy (CEA)
• Access to plaque
specimen
• In vivo and Ex vivo studies
• Histology

6. Carotid MRICarotid MRI
HardwareHardware
Phased array coilsPhased array coils
• Designed / built in-house
• Flexible
• Bi-lateral
• Significant SNR improvement
Head holderHead holder
• Restricts motion
• Consistent positioning
• Patient comfort
- Hayes, et al., JMRI 6:109-112, 1996.
Pathway Medical Technologies, Redmond, WA

7. Imaging Protocol:Imaging Protocol:
Multi-Contrast WeightingMulti-Contrast Weighting
• DIR/MDIR technique
• Bright/black blood
• Spatial resolution
• 0.31 x 0.31 x 2 mm
• Total scan time
• 30 minutes
• Serial scan
capability
TOF T1W
PDW T2W

8. Quantitative AnalysisQuantitative Analysis
• Quantitative Vascular Analysis System (QVAS)
PD
T1
TOF
Fibrous cap
Lipid core
Calcium Media/adventitia
Lumen
Hemorrhage
Kerwin WS, et al. Proceedings of MICCAI 4th International Conference, 786-794, 2001.

9. QVAS: MorphologicalQVAS: Morphological
IndexesIndexes
• Vessel lumen and wall
area/volume
• Wall thickness
• Eccentricity and lesion
distribution
n C, et al. IEEE Transactions on Image Processing, 10(6): 865-873, 2001.

10. Inter-scan and Inter-raterInter-scan and Inter-rater
VariabilityVariability
V1
V2

11. Blood Vessel Volume MeasurementBlood Vessel Volume Measurement
• Precision of MRI
for Measuring
Plaque Volume
• 3.8 – 4.6% for T1W,
PDW, & T2W imaging
• Possible to detect a >
13% change in plaque
volume with 95%
confidence
• IQ – most important
factor

12. Hemorrhage -
Recent
(Type VI)
TOF T1WI
PDWI T2WI
Mallory’s Trichrome
MRI Based Lesion TypeMRI Based Lesion Type

13. MRI Based Lesion TypeMRI Based Lesion Type
TOF T1WI
PDWI T2WI
H&E
Type VIII: Fibrous Lesion

14. Fibrous Cap CharacteristicsFibrous Cap Characteristics
Gross
Specimen
Masson’s
Trichrome
In Vivo 3D-MOTSA Image
1 32
3
1 = Fibrous Cap Rupture
2 = Intraplaque Hemorrhage
3 = Thick Fibrous Cap
Thick fibrous cap appears as dark band
between lumen and plaque core.
Recent plaque hemorrhage appears
hyperintense.

15. Risk of Symptoms by Cap Status onRisk of Symptoms by Cap Status on
MRIMRI
95% CI
3, 210
1, 104
---
23
10
1
OR for Sx
70%
50%
9%
% w/ Sx
Ruptured Cap
Thin Cap
Thick Cap
Cap Status
p = 0.001 Mann-Whitney test for cap status vs. symptoms

16. DCE-MRI ProtocolDCE-MRI Protocol
• MRI: 2DSPGR (TR / TE = 100 / 3.5 msec)
• Contrast agent: 20 ml Omniscan (Gadolinium-based)
administered at 2ml/sec
time
~15 sec
Dynamic
MRI
Contrast injection
Pre-contrast
MRI
Post-contrast
MRI
t = 1 t = nt = 3t = 2
...

17. DCE- Kinetic Model ResultsDCE- Kinetic Model Results
0
5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3
fVA (%) by histology
fBV(%)byMRI
R = 0.80
p < 0.001

18. SummarySummary
• High resolution
MRI
• Carotid phased
array
• Black/bright blood
• Multi-contrast
weighting
• Contrast agent
application
• High resolution MRI
• Fibrous cap
• Microvessels
• Lipid core
• Ca
• Lumen surface
condition
• Matrix
• Volume

19. Grant support provided by: NIH
and AstraZeneca
Pharmaceuticals, Pfizer, and
Esperion Therapeutics
vil.rad.washington.edu
Department of Radiology
Niranjan Balu Tobias Saam
Baocheng Chu Dongxiang Xu
William S. Kerwin Annette Kampshulte
Zachary E. Miller Vasily Yarnykh
Department of Pathology
Russell Ross Steve Schwartz
Randy Small Marina S. Ferguson
Department of E. E.
Jenq Neng Hwang Ying Luo
Mountain Whisper Light
Nayak Polissar
C. Yuan, T.S. Hatsukami