Magnetic resonance fingerprinting in slices along a one-dimensional extension

Patent metadata

Field	Value
Publication number	US-10321845-B2
Application number	US-201515525145-A
Country	US
Kind code	B2
Filing date	Oct 30, 2015
Priority date	Nov 14, 2014
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

The invention provides for a magnetic resonance imaging system ( 100 ) which comprise a magnet ( 104 ) and a magnetic field gradient generator ( 110, 112 ) for generating a gradient magnetic field within an imaging zone ( 108 ). The gradient magnetic field is aligned with a predetermined direction. The magnetic resonance imaging system further comprise a memory ( 134, 136 ) for storing machine executable instructions ( 150, 152, 154 ), a pre-calculated magnetic resonance fingerprinting dictionary ( 144 ), and pulse sequence instructions ( 140 ). The pulse sequence instructions cause the magnetic resonance imaging system to acquire the magnetic resonance data according to a magnetic resonance fingerprinting technique. The magnetic resonance fingerprinting technique encodes the magnetic resonance data as slices ( 125 ). The pre-calculated magnetic resonance fingerprinting dictionary contains a listing of calculated magnetic resonance signals in response to execution of the pulse sequence instructions for a set of predetermined substances. Execution of the machine executable instructions causes a processor ( 130 ) controlling the magnetic resonance imaging system to: acquire ( 300 ) the magnetic resonance data by controlling the magnetic resonance imaging system with pulse sequence instructions; divide ( 302 ) the magnetic resonance data into a set of slices; calculate ( 304 ) the abundance of each of the set of predetermined substances within each of the set of slices by comparing the magnetic resonance data for each of the set of slices with the pre-calculated magnetic resonance fingerprinting dictionary; and calculate ( 306 ) a magnetic resonance fingerprint chart by plotting abundance of each of the set of predetermined substances within each of the set of slices as a function of position along the predetermined direction.

First claim

The invention claimed is:

1. A magnetic resonance imaging system for acquiring a magnetic resonance data from a subject within an imaging zone, wherein the magnetic resonance imaging system comprises:
a magnet for generating a main magnetic field within the imaging zone;
a magnetic field gradient generator for generating a gradient magnetic field within the imaging zone, wherein the gradient magnetic field is aligned with a predetermined direction;
a non-transitory computer readable memory for storing machine executable instructions, a pre-calculated magnetic resonance fingerprinting dictionary, and pulse sequence instructions, wherein the pulse sequence instructions cause the magnetic resonance imaging system to acquire the magnetic resonance data according to a magnetic resonance fingerprinting technique, wherein the magnetic resonance fingerprinting technique encodes the magnetic resonance data as slices, wherein the pre-calculated magnetic resonance fingerprinting dictionary contains a listing of calculated magnetic resonance signals in response to execution of the pulse sequence instructions for a set of predetermined substances;
a processor for controlling the magnetic resonance imaging system, wherein execution of the machine executable instructions causes the processor to:
acquire the magnetic resonance data by controlling the magnetic resonance imaging system with pulse sequence instructions;
divide the magnetic resonance data into a set of slices;
calculate the abundance of each of the set of predetermined substances within each of the set of slices by comparing the magnetic resonance data for each of the set of slices with the pre-calculated magnetic resonance fingerprinting dictionary; and
calculate a magnetic resonance fingerprint chart by plotting abundance of each of the set of predetermined substances within each of the set of slices as a function of position along the predetermined direction.

2. The magnetic resonance imaging system of claim 1 , wherein the pulse sequence comprises a train of pulse repetitions, wherein each pulse repetition of the train of pulse repetitions has a random duration, a preselected duration from distribution of durations, or a pseudorandom duration, wherein each pulse repetition comprises a radio frequency pulse chosen from a distribution of flip angles to rotate magnetic spins, and wherein each pulse repetition comprises a sampling event where the magnetic resonance signal is sampled for a predetermined duration at a predetermined time before the end of the repetition pulse, wherein the magnetic resonance data is acquired during the sampling event.

3. The magnetic resonance imaging system of claim 2 , wherein each pulse repetition of the pulse sequence comprises a first 180 degree RF pulse performed at a first temporal midpoint between the radio frequency pulse and the sampling event to refocus the magnetic resonance signal, and wherein each pulse repetition of the pulse sequence comprises a second 180 degree RF pulse performed at a second temporal midpoint between the sampling event and the start of the next pulse repetition in order to reduce the dependency of the signal on inhomogeneities in the main magnetic field within the imaging zone.

4. The magnetic resonance imaging system of claim 1 , wherein the calculation of the abundance of each of the predetermined tissue types within each of the set of slices by comparing the magnetic resonance data for each of the set of slices with the pre-calculated magnetic resonance fingerprinting dictionary is performed by:
expressing each magnetic resonance signal of the magnetic resonance data as a linear combination of the signal from each of the set of predetermined substances, and
determining the abundance of each of the set of predetermined substances by solving the linear combination using a minimization technique.

5. The magnetic resonance imaging system of claim 1 , wherein execution of the instructions further causes the processor to render the magnetic resonance fingerprint chart on a display medium.

6. The magnetic resonance imaging system of claim 5 , wherein execution of the instructions further causes the processor to superimpose a representation of a subject onto the rendering of the magnetic resonance fingerprint chart.

7. The magnetic resonance imaging system of claim 6 , wherein execution of the instructions further causes the processor to align the representation of the subject in the rendering of the magnetic resonance fingerprint chart using any one of the following: use a pre-defined relationship between the representation and a location along the predetermined direction, and match the abundance of at least one of the set of predetermined substances with an anatomical location indicated by the representation of the subject.

8. The magnetic resonance imaging system of claim 1 , wherein the magnetic resonance imaging system further comprises a subject support operable for stepwise moving of the subject through the imaging zone along the predetermined direction, wherein execution of the instructions further causes the processor to:
control the subject support to move the subject through the imaging zone along the predetermined direction during acquisition of the magnetic resonance data, wherein the division of the magnetic resonance data into the set of slices is at least partially determined by the position of the subject support during the acquisition of the magnetic resonance data.

9. The magnetic resonance imaging system of claim 8 , wherein the magnetic resonance imaging system further comprises a radio frequency system for acquiring the magnetic resonance data, wherein the radio frequency system comprises a radio frequency antenna for receiving magnetic resonance signals from the subject within the imaging zone, wherein the radio frequency antenna is a surface coil.

10. The magnetic resonance imaging system of claim 1 , wherein execution of the instructions further causes the processor to repeat measurement of the magnetic resonance data of at least one calibration phantom, wherein each of the at least one calibration phantom has a calibration axis, wherein the at least one calibration phantom comprises a known volume of at least one of the set of predetermined substances when the calibration axis is aligned with the predetermined direction.

11. The magnetic resonance imaging system of claim 1 , wherein the magnetic field gradient generator comprises a single gradient coil for generating the gradient magnetic field.

12. The magnetic resonance imaging system of claim 1 , wherein the magnetic field gradient generator comprises variations of winding within the main magnet to generate the gradient magnetic field.

13. A method of operating a magnetic resonance imaging system for acquiring magnetic resonance data from a subject within an imaging zone, wherein the magnetic resonance imaging system comprises:
a magnet for generating a main magnetic field within the imaging zone;
a magnetic field gradient generator for generating a gradient magnetic field within the imaging zone, wherein the gradient magnetic field is aligned with a predetermined direction; and
a memory for storing machine executable instructions, a pre-calculated magnetic resonance fingerprinting dictionary, and pulse sequence instructions, wherein the pulse sequence instructions cause the magnetic resonance imaging system to acquire the magnetic resonance data according to a magnetic resonance fingerprinting technique, wherein the magnetic resonance fingerprinting technique encodes the magnetic resonance data as slices, wherein the pre-calculated magnetic resonance fingerprinting dictiona

Assignees

• Koninklijke Philips Nv

Inventors

• Amthor Thomas Erik
• Doneva Mariya Ivanova
• Koken Peter
• Keupp Jochen
• Boernert Peter

Classifications

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/50

  based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences} · CPC title

• G01R33/4828

  Resolving the MR signals of different chemical species, e.g. water-fat imaging · CPC title

• A61B5/4872 Primary

  Body fat · CPC title

• G01R33/4835

  of multiple slices · CPC title