# US 12,000,917 B2 · Methods for producing magnetic resonance images with sub-millisecond temporal resolution

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- Number: US 12,000,917 B2
- Document ID: US12000917B2
- Status: Granted
- Kind: B2
- Application number: 17/423,729
- Filed: 2020-01-21
- Published: 2022-03-03
- Granted: 2024-06-04
- Earliest claimed: 2019-01-18
- Assignees: The Board of Trustees of the University of Illinois
- Applicants: The Board of Trustees of the University of Illinois
- Inventors: Xiaohong Joe Zhou; Zheng Zhong; Meryem Muge Karaman
- Web page: https://patentgrep.com/patent/US12000917B2

## CPC

- G01R 33/243: {Spatial mapping of the polarizing magnetic field}
- G01R 33/4824: {using a non-Cartesian trajectory}
- G01R 33/56: Image enhancement or correction, e.g. subtraction or averaging techniques {, e.g. improvement of signal-to-noise ratio and resolution}
- G01R 33/5608: {Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T)}
- G01R 33/561: by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
- G01R 33/5611: {Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE (structural details of arrays of sub-coils G01R33/3415)}
- G01R 33/5616: {using gradient refocusing, e.g. EPI}
- G01R 33/56325: {Cine imaging}
- 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}
- G06F 7/588: {Random number generators, i.e. based on natural stochastic processes}
- H04L 9/0662: {with particular pseudorandom sequence generator}
- H04L 9/3239: {involving non-keyed hash functions, e.g. modification detection codes [MDCs], MD5, SHA or RIPEMD}
- H04L 9/3247: {involving digital signatures}
- H04L 9/50: {using hash chains, e.g. blockchains or hash trees}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A system and method for producing a series of time-resolved magnetic resonance (MR) images is set forth. The system can perform method steps of encoding spatial information into an MRI signal by manipulating a phase of the MRI signal within an MRI system, generating and outputting a phase-encoded MRI signal over time by digitizing a plurality of time points in the MRI signal, repeating the generating and outputting step for a plurality of phase-encoded signals, each phase-encoded signal in synchrony with a trigger, producing a plurality of digitized time points, and reconstructing a series of time resolved MR images, each image of the series of MR images at one specific time point selected from the plurality of digitized time points for each phase-encoded step. Each image in the series of time-resolved MR images corresponding to a specific time point in a cyclic event.

## Claims

### Claim 1

A method for acquiring a magnetic resonance imaging (MRI) signal of a cyclic event and for reconstructing a magnetic resonance (MR) image of the cyclic event with high temporal resolution, the method comprising:
phase encoding spatial information into an MRI signal to produce a phase-encoded MRI signal by manipulating a phase of the MRI signal within an MRI system;
performing a data acquisition process in the MRI system that samples the phase-encoded MRI signal at N instants in time in each of M data acquisition windows to generate N matrices, each matrix comprising a phase-encoded raw data set that corresponds to a respective point in time on the MRI signal, each phase-encoded raw data set comprising L raw data set points, where M, N and L are positive integers that are greater than or equal to two, each data acquisition window being synchronized to the cyclic event; and
processing each of the N phase-encoded raw data sets to produce a series of N reconstructed MR images of the cyclic event.

### Claim 2

A method for producing a series of time-resolved magnetic resonance (MR) images comprising:
encoding spatial information into a magnetic resonance imaging (MRI) signal by manipulating a phase of the MRI signal within an MRI system;
generating and outputting a phase-encoded MRI signal over time by digitizing a plurality of time points in the MRI signal;
using the MRI system, repeating the generating and outputting step for a plurality of phase-encoded signals, each phase-encoded signal in synchrony with a trigger and each phase-encoded signal incorporating a distinctive or identical phase-encoding value and producing a plurality of digitized time points; and
reconstructing a series of time-resolved MR images, each image of the series of time-resolved MR images at one specific time point selected from the plurality of digitized time points for each phase-encoded signal, by utilizing phase-encoded data acquired from the output of the plurality of phase-encoded signals, each image in the series of time-resolved MR images corresponding to a specific time point in the cyclic event.

### Claim 3

A system for reconstructing a magnetic resonance (MR) image of a cyclic event with high temporal resolution, the system comprising:
a phase encoder configured to phase encode spatial information into a magnetic resonance imaging (MRI) signal to produce a phase-encoded MRI signal by manipulating a phase of the MRI signal;
a data acquisition system that performs a data acquisition process that samples the phase-encoded MRI signal at N instants in time in each of M data acquisition windows to generate N matrices, each matrix comprising a phase-encoded raw data set that corresponds to a respective point in time on the MRI signal, where M and N are positive integers that are greater than or equal to two, each data acquisition window being synchronized to the cyclic event; and
a processor configured to process the phase-encoded raw data set to produce a reconstructed MR image of the cyclic event.

### Claim 4

A system for reconstructing a magnetic resonance (MR) image of a cyclic event with high temporal resolution, the system comprising:
a phase encoder configured to phase encode spatial information into a magnetic resonance imaging (MRI) signal to produce a phase-encoded MRI signal by manipulating a phase of the MRI signal, the MRI signal comprising a train of echoes of one of a free-induction decay (FID) signal, a gradient-echo signal, a spin-echo signal and a stimulated echo signal;
a data acquisition system that performs an echo-train-based data acquisition process that samples the train of echoes such that each echo in the train of echoes is positioned in a respective time-resolved two-dimensional (2-D) k-space matrix and such that all echoes of the train of echoes are spread across a series of the time-resolved 2-D k-space matrices, the echo-train-based data acquisition process being repeated with different phase-encoding values applied by the phase encoder to the MRI signal to produce the phase-encoded MRI signal until all of the time-resolved 2-D k-space matrices are adequately sampled; and
a processor configured to process the series of 2-D k-space matrices to produce a reconstructed MR image of the cyclic event with a temporal resolution determined by an inter-echo spacing between two adjacent echoes of the train of echoes.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
displaying a reconstructed MR image on a display device.

### Claim 6 (depends on 1)

The method of claim 1, wherein the series of N reconstructed MR images has a temporal resolution that is less than or equal to one millisecond.

### Claim 7 (depends on 6)

The method of claim 6, wherein each matrix is a k-space matrix comprising L k-space points.

### Claim 8 (depends on 1)

The method of claim 1, wherein the MRI signal is one of a free-induction decay (FID) signal, a spin-echo signal, a stimulated echo signal, a train of FID signals, a train of gradient-echo signals, a train of spin-echo signals and a train of stimulated echo signals.

### Claim 9 (depends on 8)

The method of claim 8, wherein the temporal resolution is based on a dwell time, Δt, of the data acquisition process, and wherein the dwell time is inversely related to a bandwidth, BW, of the MRI system as 1/BW.

### Claim 10 (depends on 1)

The method of claim 1, wherein the step of processing the phase-encoded raw data sets to produce a reconstructed MR image of the cyclic event includes performing a phase evolution algorithm that processes phase-encoded images to produce phase maps corresponding to respective phase-encoded raw data sets and takes differences between the phase maps to obtain a time-resolved phase evolution of the cyclic event.

### Claim 11 (depends on 1)

The method of claim 1, wherein the cyclic event is physical, chemical, biological, physiological, or metabolic in nature.

### Claim 12 (depends on 11)

The method of claim 11, wherein the cyclic event is an aortic valve opening and closing.

### Claim 13 (depends on 2)

The method of claim 2, wherein the series of time-resolved MR images span a fraction of a cycle, a full cycle or a plurality of cycles in the cyclic event.

### Claim 14 (depends on 2)

The method of claim 2, wherein the cyclic event is physical, chemical, biological, physiological, or metabolic in nature.

### Claim 15 (depends on 2)

The method of claim 2, wherein manipulation of the MRI signal phase is performed by a phase-encoding gradient pulse or a non-linear gradient applied prior to the acquisition of the MRI signal.

### Claim 16 (depends on 2)

The method of claim 2, wherein the image reconstruction is performed by using an inverse Fourier transform or other image reconstruction technique on the plurality of phase-encoded signals, all of which are acquired at the same digitized time point from within each phase-encoded MRI signal.

### Claim 17 (depends on 2)

The method of claim 2, wherein the plurality of phase-encoded signals are substantially reduced by utilizing parallel imaging reconstruction or compressive sensing image reconstruction.

### Claim 18 (depends on 2)

The method of claim 2, wherein the MRI signal is one of a free-induction decay (FID) signal, a spin-echo signal, a stimulated echo signal, a train of FID signals, a train of gradient-echo signals, a train of spin-echo signals and a train of stimulated echo signals.

### Claim 19 (depends on 3)

The system of claim 3, wherein the MRI signal is one of a free-induction decay (FID) signal, a spin-echo signal, a stimulated echo signal, a train of FID signals, a train of gradient-echo signals, a train of spin-echo signals and a train of stimulated echo signals.

### Claim 20 (depends on 19)

The system of claim 19, wherein the reconstructed MR image has a temporal resolution that is less than or equal to one millisecond.