Cardiac synchronization magnetic resonance imaging

• US 5,000,182 A
• Filed: 08/11/1989
• Issued: 03/19/1991
• Est. Priority Date: 08/11/1989
• Status: Expired due to Term

• Current Assignee: Picker International, Inc. (Marconi Holdings Company Limited)
• Original Assignee: Picker International, Inc. (Marconi Holdings Company Limited)
• Inventors: Hinks, Richard S.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Zele, John D.
• Application Number:
  US07/392,441
• Time in Patent Office: 585 Days
• Field of Search: 128/696, 128/653 A, 128/653, 128/708, 324/306
• US Class Current: 600/413
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7292 Prospective gating, i.e. predicting the occurrence of a physiological event for use as a synchronisation signal
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Abstract

A cardiac monitor (62, 64) monitors the cardiac cycles of a patient in an examination region (10). Each cardiac cycle includes an R-wave (40) at the beginning of the end-diastole. A conditioning pulse trigger (74) enables a preconditioning pulse control (34) to generate a conditioning pulse (42) at a time selected in accordance with the R-wave (40_n-1) of one cardiac cycle. More specifically, an R-wave predictor (72) predicts when the next R-wave (40_n) will occur and the conditioning pulse trigger enables the application of the conditioning pulse (42_n) a selected duration before the next predicted R-wave (40_n). An imaging sequence trigger (78) enables an image sequence controller (24) to start an imaging sequence in an imaging window (44_n) in conjunction with the R-wave (40_n). Preferably, the imaging sequence starts immediately with the R-wave (40_n) such that the end-diastole stage of the heart is imaged. In this manner, a conditioning pulse, such as an inversion pulse or a saturation pulse, is applied in one cardiac cycle to affect the imaging sequence in the next cardiac cycle. The application of the preconditioning pulse is timed such that the longitudinal magnetization of the blood (54) is near zero (56) during the imaging sequence while the transverse magnetization of cardiac tissue (52) has substantially recovered by the imaging sequence.

Claims

1. A method of magnetic resonance cardiac imaging comprising:

generating a main magnetic field through an image region;

monitoring a plurality of cardiac cycles of a patient at least partially disposed in the image region, each of the plurality of cardiac cycles having at least one preselected identifiable point;

projecting a time of occurrence of the preselected identifiable point in a subsequent cycle;

applying an inversion pulse a preselected duration before the projected preselected identifiable point of the subsequent cardiac cycle, the inversion pulse inverting the longitudinal magnetization of blood and cardiac tissue recovering at different rates;

conducting a magnetic resonance imaging sequence in coordination with the preselected identifiable point in the subsequent cycle to induce magnetic resonance signals to be emitted from blood and cardiac tissue in the image region;

acquiring and reconstructing the magnetic resonance signals into an image representation.

2. The method as set forth in claim 1 wherein the imaging sequence suppresses flow related spin dephasing artifacts.

3. The method as set forth in claim 1 wherein the inversion pulse inverts magnetization outside of the image region such that blood with inverted longitudinal magnetization flows into the image region.

4. A method of magnetic resonance imaging of a cyclically moving organ comprising:

generating a main magnetic field through an image region;

monitoring a plurality of cycles of the cyclically moving organ of a patient at least partially in the image region, each of the plurality of cycles having at least one preselected identifiable point;

projecting a time of occurrence of the preselected identifiable point in a subsequent cycle;

applying a preconditioning radio frequency pulse a preselected duration before the projected preselected identifiable point of the subsequent cycle;

conducting a magnetic resonance imaging sequence in coordination with the preselected identifiable point of the subsequent cycle;

acquiring magnetic resonance signals induced by the imaging sequence;

reconstructing an image representation from the acquired magnetic resonance signals.

5. The method as set forth in claim 4 wherein the preconditioning radio frequency pulse rotates longitudinal magnetization of nuclei of the patient that are induced to resonate by the imaging sequence.

6. The method as set forth in claim 5 wherein the preconditioning pulse rotates the longitudinal magnetization 90°

to 180°

.

7. The method as set forth in claim 5 wherein the preconditioning pulse is a saturation pulse.

8. A method of magnetic resonance cardiac imaging comprising:

(a) positioning a patient in an imaging region through which a strong magnetic field is generated;

(b) monitoring a cardiac cycle of the patient to determine the occurrence of an R-wave;

(c) projecting an occurrence of a next R-wave in a subsequent cardiac cycle;

(d) a preselected duration before the projected next R-wave, applying a radio frequency preconditioning pulse which rotates the longitudinal magnetization of selected nuclei to be imaged;

(e) conducting an imaging sequence in a coordinated time relationship with the next R-wave;

(f) acquiring magnetic resonance data induced by the imaging sequence;

(g) reconstructing an image representation from the acquired data.

9. The method as set forth in claim 8 further including repeating steps (b) to (f) for each of a plurality of cardiac cycles and reconstructing the image representation from the data collected from the plurality of imaging sequences.

10. The method as set forth in claim 9 wherein the preconditioning pulse includes a saturation pulse.

11. The method as set forth in claim 9 wherein the preconditioning pulse includes an inversion pulse which inverts the longitudinal magnetization of blood and cardiac tissue, the inversion pulse being applied to invert the longitudinal magnetization within the imaging region.

12. The method as set forth in claim 9 wherein the preconditioning pulse is an inversion pulse which is applied to invert the longitudinal magnetization of blood and cardiac tissue adjacent the imaging region such that cardiac tissue within the imaging region is unaffected and wherein the preselected duration is selected in accordance with a projected flow rate of blood tissue with inverted longitudinal magnetization into the imaging region.

13. A method of magnetic resonance imaging of a cyclically pulsating organ, the method comprising:

creating a static magnetic field through an image region that encompasses the pulsating organ;

conducting an imaging sequence in each of a plurality of contiguous organ cycles to cause magnetic resonance signals to be emitted from the image region;

acquiring the resonance signals and reconstructing an image representation therefrom;

projecting an occurrence of an identifiable point in a next organ cycle;

applying a preconditioning pulse following each imaging sequence and a preselected duration before the projected occurrence of the identifiable point in the next organ cycle such that the resonance signals acquired from the imaging sequence conducted in a next organ cycle are affected by the preconditioning pulse.

14. A magnetic resonance apparatus comprising:

means for creating a magnetic field through an image region in which a patient is at least partially disposed;

an imaging sequence means for applying an imaging sequence of radio frequency and gradient magnetic field pulses in the image region to generate magnetic resonance image data;

a preconditioning pulse means for applying a preconditioning radio frequency pulse in the image region, the radio frequency preconditioning pulse affecting a subsequent imaging sequence;

a cardiac monitor means for monitoring cardiac cycles of the patient;

a projecting means for projecting an occurrence of a preselected identifiable point in a next cardiac cycle, the projecting means being connected with the cardiac monitor means;

a first enabling means for enabling the preconditioning pulse means to apply the preconditioning pulse a preselected duration before the occurrence of the projected preselected identifiable point in the next cardiac cycle, the first enabling means being connected with the projecting means and the preconditioning pulse means;

a second enabling means for enabling the imaging sequence for applying the imaging sequence in coordination with the preselected identifiable point of the next cardiac cycle, the second enabling means being connected to the cardiac monitoring means and the imaging sequence means such that each imaging sequence is affected by the preconditioning pulse applied during a preceding cardiac cycle.

15. The apparatus as set forth in claim 14 wherein the cardiac monitor means monitors the cardiac cycles for at least the occurrence of an R-wave and wherein the projecting means projects the occurrence of the R-wave of the next cardiac cycle and the second enabling means enables the imaging sequence means in response to the monitored R-wave.