MAGNETIC RESONANCE FINGERPRINTING METHOD FOR RECORDINGS WITH A CONTRAST AGENT

Abstract

The present disclosure relates to the technical field of magnetic resonance tomography. The present disclosure relates to a method, a system and a computer program product for determining different states of a contrast agent in different types of tissue in a magnetic resonance fingerprinting method.

Claims

1. A method comprising the following steps: providing a magnetic resonance fingerprint database, wherein the magnetic resonance fingerprint database comprises database waveforms for a specific contrast agent in at least two different tissue types, a first tissue type and a second tissue type, wherein the contrast agent has a different state in the first tissue type than in the second tissue type, acquiring a magnetic resonance waveform for a volume element of an examination region via a magnetic resonance fingerprinting method using the contrast agent, comparing the magnetic resonance waveform with database waveforms, identifying a database waveform having a defined correspondence with the magnetic resonance waveform, determining the states of the contrast agent in the volume element, and outputting information on the states of the contrast agent in the volume element.

2. The method of claim 1, wherein the contrast agent has a different molar relaxivity in the first tissue type than in the second tissue type.

3. The method of claim 2, wherein the molar relaxivity in the first tissue type is at least 1.5 times greater than in the second tissue type.

4. The method of claim 3, wherein the molar relaxivity at a magnetic field strength of a basic magnetic field of at least 1.5 tesla, preferably of at least 2 tesla, even more preferably of at least 2.5 tesla, even more preferably of at least 3 tesla, most preferably at a magnetic field strength of 0.4 tesla to at least 3 tesla, is in the first tissue type at least 1.5 times greater, preferably at least 2 times greater, even more preferably at least 2.5 times greater, than in the second tissue type.

5. The method of claim 1, wherein the contrast agent has a higher molar T1 relaxivity in the first tissue type than in the second tissue type.

6. The method of claim 1, wherein the contrast agent comprises gadoxetic acid or a salt of gadoxetic acid as contrast-enhancing active substance.

7. The method of claim 1, wherein the contrast agent comprises Gd-EOB-DTP disodium.

8. The method of claim 1, wherein hepatocytes are the first tissue type.

9. The method of claim 1, wherein healthy liver tissue is the first tissue type and diseased liver tissue is the second tissue type.

10. A system comprising a receiving unit, a control unit, a signal comparison unit, and an output unit, wherein the control unit is configured to cause the receiving unit to receive a magnetic resonance waveform for at least one volume element of an examination region, the magnetic resonance waveform having been generated in a magnetic fingerprinting method using a contrast agent, wherein the control unit is configured to cause the receiving unit to receive a plurality of database waveforms from a magnetic resonance fingerprint database, each waveform being matched to at least two database values of two tissue parameters, a first tissue parameter and a second tissue parameter, wherein the first tissue parameters characterizes a first state of the contrast agent in a first tissue type and the second tissue parameter characterizes a second state of the contrast agent in a second tissue type, wherein the control unit is configured to cause the signal comparison unit to compare the magnetic resonance waveform with the database waveforms, to identify a database waveform having a defined correspondence, and to determine the at least two database values matched to the identified database waveform, and wherein the control unit is configured to cause the output unit to save and/or output the at least two database values or values derived from the at least two database values.

11. A non-transitory computer readable medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computer, cause the computer to: receive a magnetic resonance waveform for a volume element of an examination region from a magnetic resonance fingerprinting method using a contrast agent, receive database waveforms, each database waveform being matched to different states of the contrast agent in different tissue types, compare the magnetic resonance waveform with database waveforms, identify a database waveform having a defined correspondence with the magnetic resonance waveform, determine the different states of the contrast agent in the volume element, and output information on the different states of the contrast agent in the volume element.

12. A magnetic resonance fingerprinting method, comprising using a contrast agent, wherein the contrast agent has different states in at least two different tissue types, for determining the different states in an imaged volume element.

13. The method of claim 12, wherein the contrast agent comprises gadoxetic acid or a salt of gadoxetic acid.

14. The method of claim 12, wherein hepatocytes are the first tissue type.

15. A magnetic resonance fingerprinting method, comprising using a contrast agent, wherein the contrast agent has different states in at least two different tissue types, the different states in an imaged volume element being recorded simultaneously in one measurement.

16. The method of claim 15, wherein the contrast agent comprises gadoxetic acid or a salt of gadoxetic acid.

17. The method of claim 15, wherein hepatocytes are the first tissue type.

18. The method of claim 2, wherein the molar relaxivity in the first tissue type is at least 2 times greater than in the second tissue type.

19. The method of claim 2, wherein the molar relaxivity in the first tissue type is at least at least 2.5 times greater than in the second tissue type.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] The invention is elucidated in detail herein below with reference to figures, without any intention to restrict the invention to the features or combinations of features shown in the figures.

[0093] In the figures below:

[0094] FIG. 1 shows an exemplary flowchart describing a method according to some embodiments in the form of a sequence of successive steps;

[0095] FIG. 2 shows an exemplary schematic representation of a preferred embodiment for the acquisition of a magnetic resonance waveform by means of a magnetic resonance fingerprinting method;

[0096] FIG. 3 shows an exemplary schematic representation of the relationship between measured data sets and image data sets over time, according to some embodiments;

[0097] FIG. 4 shows an exemplary schematic representation of the comparison of magnetic resonance waveforms with database waveforms, according to some embodiments;

[0098] FIG. 5 shows an exemplary schematic representation of the identification of a database waveform having a defined correspondence with the magnetic resonance waveform, according to some embodiments;

[0099] FIG. 6 shows an exemplary schematic representation of the determination of the states of the contrast agent for the volume element imaged in the respective voxel-time series, according to some embodiments; and

[0100] FIG. 7 shows an exemplary schematic representation of one embodiment of the system according to the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0101] FIG. 1 shows an exemplary schematic representation of the course of the method according to some embodiments of the invention in the form of a sequence of successive steps. The sequence comprises the steps of [0102] providing a magnetic resonance fingerprint database (10) [0103] acquiring a magnetic resonance waveform for a volume element of an examination region by means of a magnetic resonance fingerprinting method using a contrast agent (20) [0104] comparing the magnetic resonance waveform with database waveforms (30) [0105] identifying a database waveform having a defined correspondence with the magnetic resonance waveform (40) [0106] determining the states of the contrast agent in the volume element (50) [0107] outputting information on the states of the contrast agent in the volume element (60).

[0108] FIG. 2 shows an exemplary schematic representation of a preferred embodiment for the acquisition of a magnetic resonance waveform by means of a magnetic resonance fingerprinting method (Step 20 in FIG. 1).

[0109] A pulse sequence is chosen in the normal manner, for example in accordance with a desired contrast or other desired properties of the measured data that can be read with the pulse sequence (21).

[0110] The pulse sequence is executed with a first set (i=1) of acquisition parameters P.sub.i, wherein measured data are to be scanned along a first k-space trajectory T.sub.i (P, T).sub.i. A k-space trajectory along which measured data are measured in a repetition can scan the k-space in a Cartesian, spiral or radial scan mode, or in a combination of said scan modes, or along a freely constructed trajectory.

[0111] In accordance with the pulse sequence, HF pulses are radiated into the examination region, gradients are switched, and the echo signals generated by the radiated HF pulses and the switched gradients are read (22). After excitation with a HF excitation pulse, measured data are acquired along the k-space trajectory T.sub.i and saved in a measured data set MDS.sub.i.

[0112] Each measured data set MDS.sub.i is used to reconstruct an image data set IDS.sub.i (25); it is also possible to use only some of the measured data contained in the measured data set MDS.sub.i for the reconstruction. This results in one image data set IDS.sub.i per repetition i, i.e. a total of N image data sets IDS.sub.i.

[0113] A prompt (23) asks the operator whether all N desired repetitions have been executed and the corresponding N measured data sets MDS.sub.i have been saved. If this is not the case (“n”), a k-space trajectory for the next repetition is selected and the parameters of the pulse sequence are appropriately modified and optionally additionally varied (24). A selected further k-space trajectory T.sub.i+1 will generally differ from a previous k-space trajectory T.sub.i.

[0114] With the next parameter P.sub.i+1 obtained in this way and the selected further k-space trajectory T.sub.i+1 ((P, T).sub.i+1), the pulse sequence is repeated and thus a new measurement (22) is performed, such that in successive repetitions data are measured along the selected k-space trajectories T.sub.i, T.sub.i+1. As regards the selection of trajectories, reference can be made to the extensive literature on magnetic resonance fingerprinting methods; an example is the published specification DE102016217675A1, the content of which is fully incorporated into this description by reference.

[0115] When all N desired repetitions have been executed and the corresponding N measured data sets MDS.sub.i have been saved (“y”), no further measurements are performed (“stop”) and a voxel-time series (x,y,z)(i) is formed for at least one voxel (x,y,z) in the reconstructed image data sets IDS.sub.i, this being a reflection of signal intensity of the voxel (x,y,z) over the course of the acquisition times (and thus over the course of the successively executed repetitions (i) of the measured data sets MDS.sub.i). Such a voxel-time series (x,y,z)(i) is usually executed for all voxels (x,y,z) that lie within the examination region of interest. The voxel-time series (x,y,z)(i) formed are saved.

[0116] FIG. 3 shows an exemplary schematic representation of the relationship between measured data sets MDS.sub.i and image data sets IDS, over time, i.e. over the course of i.

[0117] The top line shows the measured data sets MDS.sub.i in the order in which they were acquired in the repetitions TRi, the repetitions i=1, i=2, i=3, i=4, and i=N being explicitly shown by way of example. The second line shows in the same way the image data sets IDS, reconstructed from the measured data sets MDS.sub.i, with a voxel (x,y,z) marked in the image data sets IDS.sub.i by way of example. Taking this voxel (x,y,z) by way of example, the respective intensity of the voxel (x,y,z) at the times T1 corresponding to the repetitions T1 can be plotted against time as a voxel-time series. A voxel-time series (x,y,z)(i) is a magnetic resonance waveform for a volume element of the examination region.

[0118] FIG. 4 shows an exemplary schematic representation of the comparison of magnetic resonance waveforms with database waveforms (Step 30 in FIG. 1).

[0119] Each saved voxel-time series (x,y,z)(i) from FIG. 2 is compared with a plurality of database waveforms CDS.sub.1 to CDS.sub.j saved in a magnetic resonance fingerprinting database (DB) (30). The result of each comparison can be a similarity value R that indicates how similar a voxel-time series (x,y,z)(i) is to a database waveform.

[0120] FIG. 5 shows an exemplary schematic representation of the identification of a database waveform having a defined correspondence with the magnetic resonance waveform (Step 40 in FIG. 1).

[0121] Each voxel-time series (x,y,z)(i) is normally matched to a database waveform CDS.sub.k, which is normally the database waveform that shows the greatest correspondence with the voxel-time series (x,y,z)(i) (maximum R value).

[0122] FIG. 6 shows an exemplary schematic representation of the determination of the states of the contrast agent for the volume element imaged in the respective voxel-time series (x,y,z)(i) (Step 50 in FIG. 1). The states of the contrast agent are characterized by specific values of two tissue parameters TP1 and TP2. These values (database values) arise from the database waveform CDS.sub.k identified in Step 50. They are usually saved with the database waveform CDS.sub.k in the magnetic resonance fingerprinting database and can be read after CDS.sub.k has been identified.

[0123] FIG. 7 shows an exemplary schematic representation of one embodiment of the system according to the invention. The system comprises a receiving unit (1), a control unit (2), a signal comparison unit (3), and an output unit (4). The units mentioned are components of a computer system (CS). The receiving unit (1) is configured to receive magnetic resonance waveforms from a magnetic resonance system (MS) and database waveforms from a magnetic resonance fingerprinting database (DB). Reception can take place over a network (shown by dashed lines).