Image Analysis of Cardiovascular MR Data

1. Image Analysis of Cardiovascular MR Data Amir A. Amini, Ph.D. Endowed Chair in Bioimaging Professor of Electrical and Computer Engineering The University of Louisville Louisville, KY 40292 Amir Kabir University, April 24, 2006

2. Amir Amini amini@wustl.edu until July 15 shams1000@sbcglobal.net General information about ECE and forms http://www.ece.louisville.edu/gen_forms.html On-line application for doctoral degree http://graduate.louisville.edu/app/ Useful Links/Contact Information

3. ECE Dept. Highlights Paul B. Lutz Hall • 20-25 faculty covering all areas of research and teaching in ECE • Strong group in nanotechnology: including an $8.5M clean room • Strong group in signal and image processing including 3 faculty • with interests in computer vision, medical imaging, and neural networks

4. GPA > 80% GRE > 1800 TOEFL > 600 Students who have finished their M.S. are given preference. If GPA > 90%, GRE > 2000, and class rank in top 5 students will be considered for a prestigious university fellowship Minimum Admissions Requirements

5. Cardiovascular Innovations at UofL Univ. of Louisville surgeons Laman Gray and Robert Dowling performed the very first totally artificial heart implant in a human in the world in the late 1990’s with the AbioCor Implantable Replacement Heart

6. Cardiovascular Innovations Institute • Almost 400,000 people are diagnosed with heart failure in the US alone per year • Mission is to perform research in advanced technologies to help patients • So far $50 Million has been donated as initial budget for the institute • CII’s new 4 story building will open in December of 2006 • Cardiac Imaging and Image Processing is an important component of CII

7. Tagged MRI for assessment of cardiac function: Non-invasive measurement of 3-D myocardial strains, in-vivo Analysis of MRA data: Phase-Contrast MRI for non-invasive measurement of intravascular pressure distributions Overview of Projects

8. Myocardial Strains from Tagged MRI E. Zerhouni et al., ``Human Heart: Tagging with MR Imaging – A Method for Non-invasive Assessment of Myocardial Motion,’’ Radiology, Vol. 169, pp. 59-63, 1988.

9. Anatomic Orientation Yale Center for Advanced Instructional Media

10. Coronary Arteries Yale Center for Advanced Instructional Media

11. Lack of blood flow to the myocardium due to coronary artery disease leads progressively to ischemia, infarction, tissue necrosis, and tissue remodeling When blood flow is diminished to tissue, generally, its contractility is compromised Echocardiography is a very versatile imaging modality in measurement of LV contractility. But, it lacks methods for determining intramural deformations of the LV. The advantage of echocardiography however is that it is inexpensive. Motivation

12. Tagged MRI • Prior to conventional imaging, tissue magnetization is perturbed by application of RF and gradient pulses, resulting in saturation of signal from selected tissue locations • Tag lines appear as a dark grid on images of soft tissue • Data collection is synchronized with the ECG. • As standard in MRI, image slices are acquired at precise 3-D locations relative to the magnet’s fixed coordinate system

13. SPAMM Tagged MRI Sequence R a a -a RF Gz Gx Gy y x

14. Tagged MRI: Short-Axis • • • Patient with old healed inferior MI R R R 1000 0 32 64 96 128 160

15. Tagged MRI: Long-Axis • • • R R R 0 32 64 96 128 160 1000

16. • • • Acquisition of Short-Axis Slices

17. • • • Acquisition of Long-Axis Slices

19. B-Spline Models of Tag Planes

20. Periodic B-Splines Cubic polynomial in u • Locality: Since each basis function has local support, movement of any control point only affects a small portion of the curve • Continuity: Cubic B-spline curves are continuous everywhere

21. 4-D Cartesian B-Spline Model w u v Tustison and Amini, IEEE Trans. On Biomedical Engineering, 50(8), Aug. 2003

22. 4-D B-Spline Model • After 4-D B-Spline fitting to tag data, we can easily extract • Myocardial beads • 3-D Displacement fields • Myocardial strains

23. Myocardial Beads: Results

24. Displacement Fields To generate displacement field, we subtract the 3-D solid at t = 0from the 3-D solid at t = τ. Tustison and Amini, IEEE Trans. On Biomedical Engineering, (50)8, Aug. 2003

25. Myocardial Strain • Strain is a directionally dependent measure of percent change in length of a continuous deformable body • Positive strains correspond to elongation whereas negative strains correspond to compression.

26. Myocardial Strain

27. Myocardial Strain

28. Myocardial Strain

29. Differential Element of Length

30. Strain Calculation n=e1: radial n=e2:circumferential n=e3: longitudinal

31. Strain Calculation Motion field:

32. Displacement Fields

33. Radial Strain

34. Circumferential Strains

35. Longitudinal Strains

37. Torsion: k2

38. Radial Thickening: k1

39. Simulated Tagged MRI Movie

40. Circumferential Strains

41. Displacement Fields

42. Strain Results – k1 +0.30 0.0 -0.30 Radial Strain Circumferential Strain

43. Sixteen Segment Model

44. Average Normal Strains Diamonds: radial Circles: circumferential Squares: longitudinal

45. Average Normal Strains Diamonds: radial Circles: circumferential Squares: longitudinal

46. Normal Strain Plots for Patient with old MI Diamonds: radial Circles: circumferential Squares: longitudinal

47. Normal Strain Plots in Patient with old MI Diamonds: radial Circles: circumferential Squares: longitudinal

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49. Intravascular Pressures from Phase-Contrast MR Velocities

50. Percent diameter stenosis does not generally translate to a measure of a stenosis’ significance Knowledge of pressure drop across a stenosis is the gold standard but is currently obtained invasively with a pressure catheter under X-ray angiography MRI has the tools for potentially determining pressure drops across vascular stenoses, accurately, and non-invasively. Hemodynamic Significance of Arterial Stenoses