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103 in vivo mri of thrombi

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103 in vivo mri of thrombi

  1. 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. 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. 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. 4. From low-risk to high-risk plaque From fatty streak to ruptured lesion Berliner et al. Circulation. 1995;91:2488-2496
  5. 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. 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. 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. 8. Subjects & Methods (2) • MRI slices were matched with the corresponding histological slices by Reader 1 (bifurcation, ink, gross morphological features) ╸ ╹
  9. 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. 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. 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. 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. 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. 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. 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. 16. Example of a true positive result T1w 3D TFE T1w FSE Histology: Internal carotid artery containing thrombus
  17. 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. 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. 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)

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