Electricity: measuring and testing – Particle precession resonance – Determine fluid flow rate
Reexamination Certificate
2002-05-15
2004-06-22
Arana, Louis M. (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Determine fluid flow rate
C324S307000
Reexamination Certificate
active
06753683
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention is nuclear magnetic resonance imaging methods and systems. More particularly, the invention relates to the adaptive averaging of real-time velocity spectra using variable density trajectories.
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B
0
), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B
1
) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, M
z
, may be rotated, or “tipped”, into the x-y plane to produce a net transverse magnetic moment M
t
. A signal is emitted by the excited spins after the excitation signal B
1
is terminated, this signal may be received and processed to form an image.
When utilizing these signals to produce images, magnetic field gradients (G
x
G
y
and G
z
) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well known reconstruction techniques.
Cardiovascular diseases that restrict blood flow, such as valvular stenosis and aortic coarcation, can be assessed with measurements of the peak velocity of blood through the constriction. Real-time MR measurements of the velocity spectrum of blood are possible using two dimensional (“2D”) selective excitations with one dimensional (“1D”) Fourier velocity encoding (“FVE”). However, there is an inherent trade-off between the velocity resolution, aliasing velocity, and temporal resolution of such measurements. To improve the velocity resolution without changing the temporal resolution, variable-density (“VD”) trajectories can be used to sample edges of velocity k-space more coarsely than the center. A drawback of a VD approach is that it will introduce aliasing artifacts when the velocity spectrum contains significant high-frequency information (e.g., plug flow). To overcome this problem, an embodiment of the present invention provides for the adaptive averaging of real-time velocity spectra using variable density trajectories.
BRIEF SUMMARY OF THE INVENTION
A system and method for adaptive averaging of velocity spectra using variable density trajectories, comprising: acquiring at least one series of velocity spectra using interleaved variable density trajectories and sampling low k
v
data more often or more densely than high k
v
data, the series of velocity spectra further comprising at least one spectrum; identifying a series of velocity spectra that comprises at least one velocity spectrum as a template, aligning at least one of the acquired series of velocity spectra with the template using low k
v
data; and averaging the aligned spectra, the averaging further comprising averaging the low k
v
data of the aligned spectra, and combining the averaged low k
v
data with the high k
v
data of the aligned spectra, wherein the combination produces enhanced spectra.
REFERENCES:
patent: 5309099 (1994-05-01), Irarrazabal et al.
patent: 5650723 (1997-07-01), Meyer
patent: 5873825 (1999-02-01), Mistretta et al.
Bailes, D.R.; Gilderdale, D.J.; Bydder, G.M.; Collins, A.G.; Firmin, D.N.; “Respiratory Ordered Phase Encoding (ROPE): A Method for Reducing Respiratory Motion Artefacts in MR Imaging” Journal of Computer Assisted Tomography 1985; 9(4): 835-838, Jul./Aug.
Einthoven, W.; Fahr, G.; DeWaart, A.; “On the Direction and Manifest Size of the Variations of Potential in the Human Heart and on the Influence of the Position of the Heart on the Form of the Electrocardiogram” American Heart Journal, vol. 40, Aug. 1950, No. 2 p 163-211.
Frayne, Richard; Rutt, Brian K; “Frequency Response of Prospectively Gated Phase-Contrast MR Velocity Measurements” JMRI 1995, 5:65-73.
Hardy, Christopher J.; McKinnon Graeme C.; Saranthan, Manoj; “High-Resolution Coronary Artery Imaging by Adaptive Averaging” Proceeding of the International Society for Magnetic Resonance in Medicine 1999, p 231.
Hardy, Christopher J.; Curwen, Rupert W.; Darrow, Robert, D.; “Robust Coronary MRI by Spiral Fluoroscopy with Adaptive Averaging” ISMRM, 1998 p 22.
Hu, Bob S.; Pauly, John M.; Nishimura, Dwight G.; “Localized Real-Time Velocity Spectra Determination” Magn Reson Med 1993; 30:393-398.
Luk-Pat, G.T.; Sachs, T.S.; Fayad, Z.A.; Wang, Y.; “3 D Coronary- Artery Imaging with Two-Dimensional Images of the Artery as Navigators” ISMRM 2000; p 1627.
Sabataltis, J.C.; Luk-Pat, G.T; Hu, B.S.; Nishimura, D.G.; “One-Shot Fourier Velocity-Encoding Using a Variable-Density-Trajectory” Proceedings of the ISMRM, 2001 p 372.
Spraggins, Thomas “Wireless Restrospective Gating: Application to Cine Cardiac Imaging” Magnetic Resonance Imaging 1990 p 675-681.
Sussman, M.S.; Wright, G.A.; “Non-ECG-Triggered, High Resolution, Coronary Artery Imaging using Adaptive Averaging with Real-Time Variable-Density Spirals” Proceedings of the ISMRM 2001 p 175.
Sussman, M.S.; Wright, G.A.; “The Correlation Coefficient Technique for Pattern Matching” Proceedings of the ISMRM 1999 p 2003.
Wang, Yi; Ehman, Richard L.; “Retrospective Adaptive Motion Correction for Navigator-Gated 3D Coronary MR Angiography” Journal of Magnetic Resonance Imaging 2000; 11:208-214.
MacGowan Christopher Keith
Sussman Marshall Stephen
Wright Graham Arnold
Arana Louis M.
Cantor & Colburn LLP
GE Medical Systems Global Technology Company LLC
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