Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-05-14
2002-03-05
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C324S307000, C324S309000
Reexamination Certificate
active
06353752
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic resonance imaging (MRI), and more particularly the invention relates to imaging a dynamic object in which a field of view includes both a dynamic portion and a static portion during a motion cycle. The invention and background will be described with reference to publications listed in the attached appendix.
Several MRI applications involve imaging a dynamic object to resolve its temporal behavior [1-8]. In such applications, it is often difficult to achieve the desired temporal resolution while maintaining the required spatial resolution and field-of-view (FOV). Methods have been developed to increase the temporal resolution in the special case where only a fraction of the FOV undergoes fully dynamic changes [9, 12], the rest of the FOV being considered fully static [9, 11], undergoing a cyclic motion [10], or just being ‘less dynamic’ than the fully dynamic part [12]. Although cardiac imaging is an important example of an imaging application where motion is concentrated into only a part of the FOV, the reduced-FOV (rFOV) methods mentioned above are not compatible with one of the most common cardiac sequences, so-called ‘retrospective’ cine imaging [1, 2]. Because of the time interpolation involved in cine reconstruction, one cannot change the sampling function from time frame to time frame as is done in [11, 12], or acquire only one or a few full FOV images as is done in [9, 10].
The present invention is a rFOV method designed to be compatible with cine imaging, providing an increase by a factor n in temporal resolution (or a decrease by a factor n in scan time) if only 1
th
of the FOV is dynamic, the rest being considered static.
SUMMARY OF THE INVENTION
With the present method, only a fraction of all the k-space ‘portions’ (e.g. lines) need to be acquired multiple times over a full cardiac cycle (instead of all the k-space ‘portions’, as in normal CINE imaging). It is shown that if only one n
th
of the FOV is dynamic, only one n
th
of the k-space ‘portions’ need to be acquired multiple times. The remaining fraction ((n−1)
) of the k-space ‘portions’ can be acquired only once, leading to an increase by about a factor n in temporal resolution or a decrease by about n in scan time. Using the data acquired multiple times, along with the assumption that only one n
th
of the FOV is dynamic, it is shown that values for the ‘portions’ acquired only once can be calculated for any cardiac phase. Accordingly, there is no need to acquire this data at multiple cardiac phases. Avoiding the acquisition of such unnecessary data leads to the stated increase in temporal resolution, or decrease in scan time.
The invention and objects and features thereof will be more readily apparent from the following description and appended claims when taken with the drawings.
REFERENCES:
patent: 4710717 (1987-12-01), Pele et al.
patent: 5615677 (1997-04-01), Pele et al.
patent: 5653233 (1997-08-01), Pele et al.
patent: 5697370 (1997-12-01), Pele et al.
patent: 5873825 (1999-02-01), Mistretta et al.
Xiaoping Hu, Todd Parish, “Reduction of Field of View for Dynamic Imaging”, MRM 31:691-694 (1994).
Jill O. Fredrickson, Norbert J. Pelc, “Temporal Resolution Improvement in Dynamic Imaging”, MRM 35:621-625 (1996).
Bruno Madore, Gary H. Glover and Norbert J. Pelc, “UNaliasing by Fourier-encoding the Overlaps using the temporaL Dimension (UNFOLD), applied to cardiac imaging and fMRI”, MRM 1-62 (Spring 1999).
Gerald w. Lenz, E. Mark Haacke, and Richard D. White, “Retrospective Cardiac Gating: A Review of Technical Aspects and Future Directions”, MRM vol. 7, No. 5 445-455 (1989).
Madore Bruno
Pelc Norbert J.
Board of Trustees of the Leland Standford Junior University
James Talaya
Lateef Marvin M.
Townsend and Townsend / and Crew LLP
Woodward Henry K.
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