Self-adaptive tracking and phase encoding during data collection for contrast-enhanced MRA and dynamic agent uptake studies

• US 6,597,937 B2
• Filed: 02/05/2001
• Issued: 07/22/2003
• Est. Priority Date: 02/05/2001
• Status: Expired due to Fees

• Current Assignee: Marconi Medical Systems, Inc. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Cull, Thomas S., Suri, Jasjit S., Liu, Kecheng
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US09/776,964
• Publication Number:
  US 20020107438A1
• Time in Patent Office: 897 Days
• Field of Search: 600/420, 600/410, 600/407, 600/419, 600/425, 600/416-418, 382/128-132, 128/916-923, 324/306, 324/307
• US Class Current: 600/420
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: G01R 33/5601 involving use of a contrast agent for contrast manipulation, e.g. a paramagnetic, super-paramagnetic, ferromagnetic or hyperpolarised contrast agent
• CPC Class Codes: G01R 33/56308 Characterization of motion or flow; Dynamic imaging

Abstract

A magnetic resonance imaging method includes acquiring a baseline magnetic resonance image of a region of interest in the absence of a contrast agent and simulating an increase in image intensity of a subregion of interest within the region of interest which is subject to increased image intensity in the presence of a contrast agent. The magnetic resonance k-space signal intensity is correlated with contrast agent concentration in the subregion and a contrast agent is administered to the subject. As k-space data for the region of interest is acquired, the signal intensity is monitored to derive contrast agent concentration information. When the peak contrast agent concentration is detected from the monitored k-space data signal intensity, the phase encoding is adjusted so that k-space data with zero phase encoding is acquired. In a further aspect, a magnetic resonance imaging apparatus is also provided.

Claims

1. A method of magnetic resonance imaging, comprising:

acquiring a baseline magnetic resonance image of a region of interest in the absence of a contrast agent;

simulating an increase in image intensity of a subregion of interest within the region of interest, the subregion being subject to increased image intensity in the presence of a contrast agent;

correlating magnetic resonance k-space signal intensity with contrast agent concentration in the subregion;

administering a contrast agent to the subject;

acquiring k-space data for the region of interest;

monitoring the k-space data signal intensity to derive contrast agent concentration information;

detecting a peak contrast agent concentration from the monitored k-space data signal intensity;

after the peak contrast agent concentration is detected, immediately adjusting the phase encoding so that k-space data with zero phase encoding is acquired.

2. The method of claim 1, wherein the subregion is a blood vessel and further wherein the contrast agent is injected into the subject.

3. The method of claim 1, further including:

converting the k-space data into an image representation.

4. The method of claim 2, wherein the step of correlating magnetic resonance k-space signal intensity with contrast agent concentration includes:

segmenting the blood vessel;

simulating intensity changes for the vessel due to the presence of a contrast agent at a plurality of concentrations;

computing a simulated frequency domain spectrum for the vessel for each of the plurality of concentrations.

5. The method of claim 4, wherein the frequency domain spectra are calculated by:

generating images having artificially increased pixel intensities at spatial locations corresponding to the vessel;

Fourier transforming each of the baseline image and said generated images from the image domain to the frequency domain; and

in the frequency domain, subtracting the baseline image from each of said generated images.

6. The method of claim 5, wherein the step of monitoring the k-space signal intensity includes one or both of:

comparing the acquired k-space data with the simulated frequency domain spectra; and

comparing the acquired k-space data with previously acquired k-space data to detect a change in the rate of change of k-space signal intensity as a function of time.

7. The method of claim 2, wherein the baseline image representation is generated with one of a time-of-flight magnetic resonance angiographic technique and a phase contrast magnetic resonance angiographic technique.

8. The method of claim 1, further including:

during the acquisition of the k-space data from the region of interest, controlling acquisition of data from the volume of interest in accordance with a monitored physiological movement.

9. The method of claim 2, further including:

during the acquisition of the k-space data from the region of interest, controlling acquisition of data from the volume of interest in accordance with a cardiac cycle.

10. The method of claim 1, wherein the baseline images are segmented automatically.

11. The method of claim 1, wherein the baseline images are segmented manually.

12. The method of claim 1, wherein the step of acquiring k-space data includes:

acquiring k-space data with middle or low frequency phase encoding, including zero phase encoding, before the peak contrast agent concentration is detected; and

replacing the k-space data with zero phase encoding acquired before the peak contrast agent concentration is detected with said k-space data with zero phase encoding acquired after the peak contrast agent concentration is detected.

13. The method of claim 1, wherein the step of acquiring k-space data includes:

acquiring only data views selected from one or both of high frequency data lines and middle frequency data lines before the peak contrast agent concentration is detected.

14. A magnetic resonance imaging system having means for generating a magnetic field in an examination region, a radio frequency pulse controller and transmitter for inducing dipoles in the examination region to resonance such that radio frequency resonance signals are generated, gradient magnetic field coils and a gradient magnetic field controller for performing a pulse sequence including at least phase and read magnetic field gradient pulses in orthogonal directions across the examination region, a receiver for receiving and demodulating the radio frequency magnetic resonance signals, and an image processing system for reconstructing image representations, the image processing system including:

a memory for storing a baseline image representation of a region of interest in the absence of a contrast agent;

a first processor for identifying the spatial location of a subregion of interest within the region of interest, the subregion of interest being subject to increased image intensity in the presence of a contrast agent and for generating and storing simulated image representations of the region of interest in which the subregion is artificially increased;

a second image processor that calculates and stores frequency domain spectra for the subregion of interest based on differences between the baseline image and the simulated images;

a third processor that detects peak contrast agent concentration in the region of interest by monitoring k-space signal intensity received after a contrast agent is administered to a subject to be imaged;

the gradient magnetic field controller responds to detection of the peak contrast agent composition by dynamically adjusting the pulse sequence to collect k-space data lines with central phase encoding; and

a reconstruction processor that generates image representations from the magnetic resonance signals.

15. The imaging system of claim 14, wherein the peak contrast agent concentration is detected by one or both of:

comparing a received k-space signal intensity with said frequency domain spectra; and

monitoring a rate of change in received k-space signal intensity.

16. The imaging system of claim 14, further including:

a display apparatus that converts the image representations into a human-viewable images.

17. The imaging system according to claim 14, further comprising an electrocardiographic sensor.

18. The imaging system of claim 14, wherein the third image processor calculates the frequency domain spectra by:

Fourier transforming each of the baseline image representation and the simulated image representations from the image domain to the frequency domain; and

in the frequency domain, subtracting the baseline image from each of the simulated images.

19. The imaging system of claim 14, wherein the baseline image representation is generated with one of a time-of-flight magnetic resonance angiographic technique and a phase contrast magnetic resonance angiographic technique.

20. The imaging system of claim 14, further including:

the gradient magnetic field controller generates only data views selected from high and middle frequency data lines prior to detection of the peak contrast agent composition.

21. The imaging system of claim 14, further including:

the gradient magnetic field controller generates only data views selected from one or both of middle frequency data lines or low frequency data lines prior to detection of the peak contrast agent composition.

22. A method of magnetic resonance imaging comprising:

generating a plurality of data lines having high and middle frequency phase encoding;

comparing a frequency spectrum of each data line with a reference frequency spectrum indicative of a presence of contrast agent peak in a region of interest; and

in response to the comparing determining the presence of the contrast agent peak, generating centrally phase-encoded data lines.

23. The method of claim 22, further including generating the reference frequency spectrum by:

generating an image including the region of interest;

numerically simulating the presence of the contrast agent peak in at least one subregion of the region of interest; and

determining a frequency spectrum difference between the generated image and the image with the numerically simulated contrast agent peak.

24. The method of claim 23, wherein the determining step includes:

transforming at least corresponding portions of the generated image and the image with the numerically simulated contrast agent peak into frequency space; and

comparing the frequency spectra of the two images in frequency space.