Method and apparatus for MR imaging
AssigneeNorth American Philips Corporation
InventorsJohannes M. Van Eggermond, Russell Whitman, II, Abraham Naparstek, Stamatis M. Rombotis
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Abstract
An MR imaging method and apparatus especially adapted for invivo cardiac MR imaging, rejects data acquired during periods of arrhythmia while maintaining the magnetic fields and pulsing of the RF coils during such periods. Data acquisition is resumed after M cycles of regular period, and after remeasuring the data acquired during N cycles prior to the occurrence of the arrhythmia, where M and N are integers preferably from 1 to 5. The average timing can periodically be recalculated in order to compensate for slow changes in cardiac rate.
Claims14
Apparatus for in vivo measurement of magnetic resonance characteristics of biological tissue which is subject to a cyclic physical variation comprising:
- means for sensing the cyclic variation and for producing control signals representative thereof;
- means responsive to the control signals which synchronize the application of magnetic resonance-exciting fields to the tissue with the cyclic variation;
- means for acquiring magnetic resonances data from the tissue in response to the resonance-exciting fields and for employing the data so acquired to calculate the magnetic resonance characteristic;
- means which respond to an irregularity in the period of the cyclic variation which cause the means for acquiring data to cease data acquisition during, and for a period of M cycles after the end of the irregularity while, at the same time, allowing the continued application of the resonance-exciting fields;
- and
- means which determine the end of the irregularity and the M following cycles and which cause the means for acquiring data to then reacquire any data which was actually acquired during a predetermined number, N, cycles prior to the start of said irregularity and to utilize said reacquired data in the calculation of said magnetic resonance characteristic.
The apparatus of claim l wherein the cyclic variation is the cardiac cycle and the means for sensing sense pressure.
A method for reducing blurring and artifacts in magnetic resonance images of living tissue which are caused by movement or other variations produced by the cardiac cycle, comprising the steps of:
- applying magnetic resonance-exciting fields to the tissue in synchronization with said cardiac cycle and acquiring magnetic resonance data produced thereby from the tissue;
- detecting the presence of an irregularity in the period of the cardiac cycle and suspending the acquisition of the data in response thereto;
- determining the end of the irregularity, waiting for a first predetermined number, M, of normal cardiac cycle periods after the end of the irregularity and then resuming the acquisition of the data;
- and
- then reacquiring any data which had previously been acquired during a second predetermined number, N, of cardiac cycles which immediately preceded the start of the irregularity;
- and
- continuing to apply the magnetic resonance-exciting signals throughout the irregularity and the M normal cycles which follow the irregularity;
- whereby magnetic resonance data which may be perturbed by cardiac arrhythmia is rejected while the steady state magnetic resonance relaxation characteristics of the tissue are maintained during the arrhythmia.
A method for in vivo measurement of a magnetic resonance characteristic of biologic tissue which is subject to a cyclic physical variation, comprising the steps of:
- sensing the cyclic variation and producing control signals representative thereof;
- employing the control signals to synchronize the application of periodic magnetic resonance-exciting fields to the tissue with the cyclic variation;
- acquiring magnetic resonance data from the tissue in response to the resonance-exciting fields and using the data so acquired for determining the characteristic, wherein as an improvement, the method further includes the steps of
- detecting the presence of an irregularity in the period of the cyclic variation;
- suspending acquisition of the resonance data upon detection of the irregularity while continuing to apply the resonance-exciting fields to the tissue;
- resuming acquisition of the resonance data after said irregularity has been absent for at least a predetermined number, M, of cycles of the cyclic variation;
- and then
- repeating acquisition of any magnetic resonance data which had been acquired during a second predetermined number, N, of cycles of the cyclic variation which immediately preceded the detection of the irregularity and utilizing the reacquired data in the determination of the characteristic.
Dependencies are inferred from the claim text.