Three‐dimensional strain‐rate imaging

Strain‐rate imaging uses large velocity encoding gradients to obtain measurements of velocity that are extremely insensitive to the effects of random noise. The spatial differential of velocity yields the velocity gradient from which the strain‐rate and twist‐rate tensors can be determined. These tensors represent the distortion of the material and are of interest in the analysis of the dynamic behavior of living tissue (e.g., that of the myocardium). This work presents a new technique that uses the magnitude of the signal in the velocity encoded data to measure through‐plane velocity variations at the resolution of the voxel size. The magnitude of the MR signal contains information about the range of phases present within a voxel. When the phase is dependent on the velocity (as in phase velocity imaging), the magnitude contains information about the range of velocities within a voxel. The method presented in this work uses unbalanced slice‐refocusing gradients to sample the magnitude variation introduced by the interaction of velocity encoding gradients with spatially dependent velocities. The previously developed in‐plane velocity gradient methods can be easily integrated with this new through‐plane measurement to characterize the deformation of the myocardium in three spatial dimensions with high accuracy. The applicability of these methods is demonstrated theoretically, in phantoms and in vivo.

[1]  D N Firmin,et al.  Blood flow imaging by cine magnetic resonance. , 1986, Journal of computer assisted tomography.

[2]  R M Weisskoff,et al.  MRI signal void due to in‐plane motion is all‐or‐none , 1994, Magnetic resonance in medicine.

[3]  G. Glover,et al.  Encoding strategies for three‐direction phase‐contrast MR imaging of flow , 1991, Journal of magnetic resonance imaging : JMRI.

[4]  R. Herfkens,et al.  Fluid shear and spin‐echo images , 1989, Magnetic resonance in medicine.

[5]  E Tomei,et al.  Normal left ventricular dimensions and function: interstudy reproducibility of measurements with cine MR imaging. , 1990, Radiology.

[6]  L. Axel,et al.  MR imaging of motion with spatial modulation of magnetization. , 1989, Radiology.

[7]  B R Rosen,et al.  Motionless Movies of Myocardial Strain‐Rates using Stimulated Echoes , 1995, Magnetic resonance in medicine.

[8]  R. Ordidge,et al.  Assessment of relative brain iron concentrations using T2‐weighted and T2*‐weighted MRI at 3 Tesla , 1994, Magnetic resonance in medicine.

[9]  V. Wedeen Magnetic resonance imaging of myocardial kinematics. technique to detect, localize, and quantify the strain rates of the active human myocardium , 1992, Magnetic resonance in medicine.

[10]  W. Hundley,et al.  Measurement of absolute epicardial coronary artery flow and flow reserve with breath-hold cine phase-contrast magnetic resonance imaging. , 1995, Circulation.

[11]  P. V. van Dijkman,et al.  Acute, subacute, and chronic myocardial infarction: quantitative analysis of gadolinium-enhanced MR images. , 1991, Radiology.

[12]  R T Constable,et al.  Functional MR imaging using gradient‐echo echo‐planar imaging in the presence of large static field inhomogeneities , 1995, Journal of magnetic resonance imaging : JMRI.

[13]  R R Edelman,et al.  In vivo measurement of water diffusion in the human heart , 1994, Magnetic resonance in medicine.

[14]  J. Frahm,et al.  Direct FLASH MR imaging of magnetic field inhomogeneities by gradient compensation , 1988, Magnetic resonance in medicine.

[15]  G Osakada,et al.  Effect of Exercise on the Relationship between Myocardial Blood Flow and Systolic Wall Thickening in Dogs with Acute Coronary Stenosis , 1983, Circulation research.

[16]  P. Dijk Direct cardiac NMR imaging of heart wall and blood flow velocity. , 1984 .

[17]  Adrian T. Lee,et al.  Three‐Point Phase‐Contrast Velocity Measurements with Increased Velocity‐to‐Noise Ratio , 1995, Magnetic resonance in medicine.

[18]  A. Young,et al.  Three-dimensional motion and deformation of the heart wall: estimation with spatial modulation of magnetization--a model-based approach. , 1992, Radiology.

[19]  Y. Fung,et al.  Transmural Myocardial Deformation in the Canine Left Ventricle: Normal in Vivo Three‐Dimensional Finite Strains , 1985, Circulation research.

[20]  W. O'Dell,et al.  Three-dimensional myocardial deformations: calculation with displacement field fitting to tagged MR images. , 1995, Radiology.