SHAPE Society

1. IN VIVO MRI OF THROMBI IN
ADVANCED ATHEROSCLEROTIC
CAROTID ARTERY
Vincent Cappendijk1
Kitty Cleutjens1
Sylvia Heeneman1
Geert Willem Schurink1
Rob Welten2
Fons Kessels1
Mat Daemen1
Jos van Engelshoven1
Eline Kooi1
1
University Hospital of Maastricht, Cardiovascular Research
Institute Maastricht (CARIM), 2
Atrium Hospital Heerlen,
Netherlands

2. Background (1)
• Atherosclerosis is a major source of morbidity
and mortality
-61,800,000 Americans have one or more types of
cardiovascular disease (CVD)
-Mortality CVD: 958,775 yearly
-Costs: 329.2 billion Dollar
Source: American Heart Association Website

3. Background
(2)• Plaque composition rather than plaque size
(degree of stenosis) is the predictor of risk on
thrombo-embolic events
• High-resolution multi-contrast MRI can
subjectively detect atherosclerotic plaque
components in vivo1,2
• Thrombus, a component in advanced (high-risk)
lesions is still difficult to detect
1
Yuan et al. Radiology 2001; 221: 285
2
Fayad et al. Circulation Research 2001; 89: 305

4. From low-risk to high-risk
plaque
From fatty streak to ruptured lesion
Berliner et al. Circulation. 1995;91:2488-2496

5. Thrombus detection with MRI
PDw
FSE
T2w
FSE
T1w
FSE
MPRAG
E
Calcified low low low -
Lipid normal /
high
low low -
Fibrous normal /
high
high normal
/high
-
Thrombus normal /
high
variable high high
Yuan et al, Fayad et al, Zhao et al, von Ingersleben et al, Shinnar et al, Moody et al.

6. Aim of the present study
• Identification of thrombus in the carotid artery with
high-resolution MRI and T1w Turbo Field Echo
technique (T1w TFE or MPRAGE)
• Compare this technique with T1w Fast Spin Echo
(FSE)
• Determine the performance and agreement
of two observers for both techniques

7. Subjects & Methods (1)
• 11 symptomatic patients with a carotid stenosis
of more than 70%
• Pre-operative MRI scan (mean 5 +/- 4 days)
• Pathology is gold standard
• High MR signal relative to muscle tissue
= positive test result

8. Subjects & Methods (2)
• MRI slices were matched with the corresponding
histological slices by Reader 1 (bifurcation, ink,
gross morphological features)
╸
╹

9. Subjects & Methods (3)
• Reader 2 scored the same by Reader 1 marked
locations
(unaware of the results of Reader 1)
Histology:
• Gross assignment of major plaque components
(fibrous tissue, lipid core, calcification,
thrombus)
• Only areas with pre-dominantly one of these
tissue types were marked

10. MRI Protocol (1)
Hardware: 1.5 T Philips Intera whole body scanner
(Gyroscan NT, release 8.1)
Small diameter receiver surface coil (47 mm)

11. MRI Protocol (2)
Technique turbo field echo fast spin echo
TR / TE 10.3 / 4.0 ms 570 / 14 ms
(double inversion pulse)
FA 15º 90º
TI 900 ms 255 ms
In-plane resolution 0.39x0.39 mm 0.39x0.39 mm
Acquisitions 6 2
Slices 3 mm 3 mm
Scan time (9 slices) 3 minutes 7 minutes
T1w 3D TFE T1w 2D FSE

12. Results (1)
Detection rate of thrombus T1w TFE
Histology Thrombus + Thrombus –
MRI Reader 1 Reader 2 Reader 1 Reader 2
Thrombus + 40 35 8 4
Thrombus - 3 8 43 47
43 51

13. Results (2)
Detection rate of thrombus T1w FSE
Histology Thrombus + Thrombus –
MRI Reader 1 Reader 2 Reader 1 Reader 2
Thrombus + 34 31 22 18
Thrombus - 9 12 29 33
43 51

14. Results (3)
Detection rate of thrombus
T1w TFE T1w FSE
Reader 1 93% (95% C.I.: 81-99%) 79% (95% C.I.: 64-90%)
Reader 2 82% (95% C.I.: 67-92%) 72% (95% C.I.: 56-85%)
Kappa 0.73 0.29

15. Results (4)
False positive results
•FSE had far more false positive results than TFE (32 vs 9;
i.e. the different false positives for both readers together)
•The 9 false positives of TFE were all fibrous tissue,
located within the thickened vessel wall but outside the
main plaque area
•Most areas with fibrous tissue were scored correctly
in TFE (20/29)

16. Example of a true positive result
T1w 3D TFE
T1w FSE
Histology: Internal carotid
artery containing thrombus

17. Example of false positive T1w FSE
Carotid bifurcation; The arrows indicate two areas of
histological proved fibrous tissue in the internal and
external carotid artery. These areas have high signal
intensity in FSE, but not in TFE
T1w 3D TFET1w FSE

18. Discussion
• FSE has far more false positive results than TFE
-this might be due to a T2* effect
• The 9 false positives in TFE were all located within
the thickened vessel wall but outside the main
plaque area. However, most areas with histological
tissue were scored correctly in TFE (20/29)
-possibly not only high signal intensity but also
its location determines if its thrombus

19. Conclusions
• Thrombus can be accurately detected with T1w TFE
high-resolution MRI
• FSE performed significantly worse
• Two readers could detect more than 80% of histological
proven thrombi using T1w TFE (Kappa=0.73)