4D Flow Imaging - NASCI Flow Imaging.pdf · 4D Flow Overview Visually appealing Single-acquisition...
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Transcript of 4D Flow Imaging - NASCI Flow Imaging.pdf · 4D Flow Overview Visually appealing Single-acquisition...
4D Flow Overview
Visually appealing
Single-acquisition
Hemodynamic parameters
But . . .
Long scans (tho improving)
Post-processing
Clinical Role?
1 MR Technique
2 4D Visualization
3 Secondary Vascular Parameters
4 Valve-Related Aortic Disease
Phase Contrast MRI Bipolar Gradient
Hope MD et al. Chpt 17. In Ho and Reddy (Eds), Cardiovasc Imaging, Elsevier Inc.
Phase Contrast MRI VENC
Hope MD et al. Chpt 17. In Ho and Reddy (Eds), Cardiovasc Imaging, Elsevier Inc.
Exploits motion induced phase shifts.
Need reference image:
- 1D Velocity: difference of 2 measurements.
- 3D Velocity 4 measurements.
Flow images Magnitude images
Phase Contrast MRI 2D Plane
Hope - UCSF 7/9/2007
vel X
vel Y
vel Z
1 MR Technique
2 4D Visualization
3 Secondary Vascular Parameters
4 Valve-Related Aortic Disease
4D Flow Data Visualization
Each voxel has 8+ components: – 3D Spatial Localization
– Magnitude
– 3D Velocity Data
– Segment of Cardiac Cycle
– (Position in Respiratory Cycle)
PV
SVC
IVC
RA
SVC
RA
IVC
4D Flow Vector Field
4D Flow Time-Resolved Vector Field
4D Flow Streamlines
4D Flow Streamlines
SVC
IVC
Mid diastole Late diastole
SVC SVC
RA RA
IVC IVC
RV
4D Flow Vessel Specific Streamlines
4D Flow Streamlines – 3D Animation
4D Flow Particle Trace
1 MR Technique
2 4D Visualization
3 Secondary Vascular Parameters
4 Valve-Related Aortic Disease
4D Flow Secondary Vascular Parameters
Pulse Wave Velocity
Turbulence
Relative Pressure Mapping
Wall Shear Stress
Actively influences vessel wall remodeling: • Increased shear increased vessel radius so shear returns to normal.
Malek AM et al. JAMA 1999
Secondary Vascular Parameters Wall Shear Stress
Dolan et al. Ann Biomed Eng 2011
Secondary Vascular Parameters Wall Shear Stress
Slager CJ et al. Nature Clinical Practice: CV Imaging 2005
Vectorial wall shear stress (vWSS)
for helical flow.
Stalder AF et al. MRM 2008
Secondary Vascular Parameters Wall Shear Stress
Can be calculated from near wall velocity
gradients provided by 4D Flow data.
Sigovan, Hope et al. in press JMRI 2011
Secondary Vascular Parameters Wall Shear Stress
Sigovan, Hope et al. in press JMRI 2011
Secondary Vascular Parameters Wall Shear Stress
1 MR Technique
2 4D Visualization
3 Secondary Vascular Parameters
4 Valve-Related Aortic Disease
4D Flow Cardiovascular Applications
What we do now: • Valvular regurgitation.
• Stenosis.
• Shunt quantification.
• Pulmonary flow.
What we would like to do: • Understand how abnormal flow promotes
and/or exacerbates cardiovascular disease.
Thoracic Aortic Aneurysm Aortic Dimensions
Elefteriades JA. Curr Probl Cardiol 2008
3 4 5 6 cm 3 4 5 6 cm
3 4 5 6 cm 3 4 5 6 cm
Pseudoaneurysm
Needs Intervention
Ascending Aneurysms Shape Matters
Degenerative Marfan
> 5 cm
Valve-Related
Thoracic Aorta Risk Stratification
Aortic Dimensions: • Location and Shape.
Status of Vessel Wall
Flow Analysis
Hope et al. JMRI 2010
4D Flow Normal Aorta – Streamlines
4D Flow Normal Aorta – Particle Trace
4D Flow Abnormal Flow – Coarct and BAV
1-2% population.
Valvular disease > half.
Aortic dilation > half:
- Intrinsic fragility favored over
flow related mechanism.
- Asymmetric AsAo aneurysm.
4D Flow Bicuspid Aortic Valve
4D Flow AsAo Flow with BAV
Hope et al. Radiology 2010
4D Flow AsAo Flow with BAV
4D Flow Eccentric Systolic Flow – Normal, Mild and Marked
Hope et al. JACC Imaging 2011
0.9 N/m2
1.4 N/m2
1.7 N/m2
4D Flow Valve-Related Aortic Disease
Della Corte et al. J Thorac CV Surg 2008
4D Flow Helical AsAo Flow with Stenotic TAV
4D Flow Valve-Related Aortic Disease
Normal
Stenotic TAV Dilated Aorta
Stenotic BAV Dilated Aorta
Hope et al. in press IJC 2011
4D Flow Valve-Related Aortic Disease
Stenotic TAV Normal Aorta
Stenotic BAV Normal Aorta
Nonstenotic BAV Dilated Aorta
Hope et al. in press IJC 2011
4D Flow Valve-Related Aortic Disease
Unique ability:
• Detailed evaluation of aortic flow.
• More eccentric flow higher shear stress.
• Elevated shear stress at site of aneurysm.
Risk-stratification for sizable populations:
• 1-2% overall with bicuspid valves.
• 2% of elderly with aortic stenosis.
Impact clinical management:
• Determine surveillance interval.
• β-blocker to reduce systolic impulse.
• Earlier intervention if high-risk group is found.
