# US 11,079,448 B2 · System and method for proton density mapping and receiver bias correction using magnetic resonance fingerprinting (MRF)

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- Number: US 11,079,448 B2
- Document ID: US11079448B2
- Status: Granted
- Kind: B2
- Application number: 16/461,549
- Filed: 2017-11-15
- Published: 2019-11-21
- Granted: 2021-08-03
- Earliest claimed: 2016-11-16
- Assignees: Case Western Reserve University
- Applicants: Case Western Reserve University
- Inventors: Mark A. Griswold; Anagha Deshmane
- Web page: https://patentgrep.com/patent/US11079448B2

## CPC

- G01R 33/246: {Spatial mapping of the RF magnetic field B1}
- A61B 5/0042: {for the brain}
- A61B 5/055: involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
- G01R 33/4828: {Resolving the MR signals of different chemical species, e.g. water-fat imaging}
- G01R 33/50: based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences}
- G01R 33/561: by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
- G01R 33/565: Correction of image distortions, e.g. due to magnetic field inhomogeneities
- G01R 33/5659: {caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence)}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A system and method is provided for correcting receiver bias during quantitative proton density mapping with magnetic resonance fingerprinting (MRF). The method comprises acquiring MRF data from a region of interest in a subject by performing a pulse sequence using a series of varied sequence blocks to elicit a series of signal evolutions. The method further comprises comparing the MRF data to a MRF dictionary to simultaneously map proton density and another tissue property from the region of interest, the proton density map having a proton density signal and a receiver sensitivity profile signal. The method also includes quantifying the proton density signal and the receiver sensitivity profile signal using parameters provided by the proton density map and the tissue property map, and generating a quantitative map from the region of interest based on the proton density signal.

## Claims

### Claim 1

A method for correcting receiver bias during quantitative proton density mapping with magnetic resonance fingerprinting (MRF), the method comprising:
acquiring MRF data from a region of interest in a subject by performing a pulse sequence using a series of varied sequence blocks to elicit a series of signal evolutions;
comparing the MRF data to a MRF dictionary to generate a proton density map and another tissue property map from the region of interest, the proton density map having a proton density signal and a receiver sensitivity profile signal;
generating an estimated proton density signal using parameters from the tissue property map;
generating an estimated receiver sensitivity profile signal using the estimated proton density signal;
generating a fitted receiver profile signal using the estimated receiver sensitivity profile signal, and a fitted proton density signal using the fitted receiver profile signal; and
generating a quantitative map from the region of interest based at least in part on the fitted proton density signal and the fitted receiver profile signal.

### Claim 2 (depends on 1)

The method of claim 1 wherein the tissue property map comprises a relaxation parameter.

### Claim 3 (depends on 2)

The method of claim 2 wherein the relaxation parameter includes T1.

### Claim 4 (depends on 1)

The method of claim 1, wherein the quantitative map comprises an absolute tissue fraction from the region of interest.

### Claim 5

A method for correcting receiver bias during quantitative proton density mapping with magnetic resonance fingerprinting (MRF), the method comprising:
acquiring MRF data from a region of interest in a subject by performing a pulse sequence using a series of varied sequence blocks to elicit a series of signal evolutions;
comparing the MRF data to a MRF dictionary to map proton density and another tissue property from the region of interest, the proton density map having a proton density signal and a receiver sensitivity profile signal;
quantifying the proton density signal and the receiver sensitivity profile signal using parameters provided by the proton density map and the tissue property map; and
generating a quantitative map from the region of interest based on the proton density signal,
wherein the quantitative map comprises an absolute tissue fraction from the region of interest.

### Claim 6 (depends on 5)

The method of claim 5 wherein the absolute tissue fraction is determined from a voxelwise multiplication of the proton density signal and a relative tissue fraction map.

### Claim 7 (depends on 6)

The method of claim 6 wherein comparing the MRF data to the MRF dictionary further comprises simultaneously mapping the relative tissue fraction map from the region of interest.

### Claim 8

A method for correcting receiver bias during quantitative proton density mapping with magnetic resonance fingerprinting (MRF), the method comprising:
acquiring MRF data from a region of interest in a subject by performing a pulse sequence using a series of varied sequence blocks to elicit a series of signal evolutions;
comparing the MRF data to a MRF dictionary to map proton density and another tissue property from the region of interest, the proton density map having a proton density signal and a receiver sensitivity profile signal;
quantifying the proton density signal and the receiver sensitivity profile signal using parameters provided by the proton density map and the tissue property map; and
generating a quantitative map from the region of interest based on the proton density signal,
wherein determining the proton density signal and the receiver sensitivity profile signal includes using a fitting method, the fitting method comprising a set of expressions described at least by:
M
0
=
(
PD
)
⁢
(
RP
)
;
1
PD
≈
A
+
(
1
T
1
)
⁢
B
;
and
where:
M0 is the proton density map;
PD is the proton density signal;
RP is the receiver profile signal; and
A and B are constants.

### Claim 9 (depends on 8)

The method of claim 8 wherein determining the proton density signal and the receiver sensitivity profile signal includes normalizing the proton density map to a material in the region of interest.

### Claim 10 (depends on 9)

The method of claim 9 wherein the material is selected from within the brain and includes white matter, gray matter, or cerebrospinal fluid, or is selected from outside the brain includes a desired tissue.

### Claim 11 (depends on 8)

The method of claim 8 wherein the fitting method includes providing an initial value for the A and B constants to solve for an estimated proton density signal and an estimated receiver sensitivity profile signal.

### Claim 12 (depends on 11)

The method of claim 11 wherein the fitting method further includes applying a smoothing filter prior to solving for the estimated receiver sensitivity profile signal.

### Claim 13 (depends on 12)

The method of claim 12 wherein the estimated receiver sensitivity profile signal is fit to a polynomial and extrapolated across the region of interest to solve for a fitted proton density signal.

### Claim 14 (depends on 13)

The method of claim 13 wherein the A and B constants are recalculated using the fitted proton density signal, and the fitting method is repeated until the A and B constants reach a steady-state value, the steady-state value being approximately constant within a specified tolerance.

### Claim 15

A system comprising:
a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject;
a magnetic gradient system including a plurality of magnetic gradient coils configured to apply at least one magnetic gradient field to the polarizing magnetic field;
a radio frequency (RF) system configured to apply an RF field to the subject and to receive magnetic resonance signals from the subject using a coil array;
a computer system programmed to:
control the magnetic gradient system and the RF system to acquire MRF data from a region of interest in a subject by performing a pulse sequence using a series of varied sequence blocks to elicit a series of signal evolutions;
compare the MRF data to a MRF dictionary to generate a proton density map and a tissue property map from the region of interest, the proton density map having a proton density signal and a receiver sensitivity profile signal;
generate an estimated proton density signal using parameters from the tissue property map;
generate an estimated receiver sensitivity profile signal using the estimated proton density signal;
generate a fitted receiver profile signal using the estimated receiver sensitivity profile signal, and a fitted proton density signal using the fitted receiver profile signal; and
generate a quantitative map from the region of interest based at least in part on the fitted proton density signal and the fitted receiver profile signal.

### Claim 16 (depends on 15)

The system of claim 15 wherein the quantitative comprises an absolute tissue fraction from the region of interest.