METHOD FOR ACQUIRING A MAGNETIC RESONANCE IMAGE DATASET OF A SUBJECT AND MAGNETIC RESONANCE IMAGING SYSTEM

Abstract

The invention relates to a method for acquiring a magnetic resonance image dataset of a subject, a magnetic resonance imaging system and a non-transitory computer-readable medium. The method comprises the steps: (a) determining scan conditions relating to an imaging protocol which is to be carried out on the subject; (b) based on the scan conditions and/or on predetermined reference parameters, determining whether at least one imaging preparation procedure may be omitted or accelerated to have a shortened duration; (c) depending on the determination of step (b), omitting or carrying out the least one imaging preparation procedure at the standard or at the shortened duration; (d) carrying out the imaging protocol in order to acquire the magnetic resonance image dataset.

Claims

1. A method for acquiring a magnetic resonance image dataset of a subject with a magnetic resonance imaging system, comprising: determining scan conditions relating to an imaging protocol that is to be carried out on the subject; based on the scan conditions and/or predetermined reference parameters, performing a determination of whether an imaging preparation procedure may be omitted or accelerated to have a shortened duration, the imaging preparation procedure comprising (i) a scanner adjustment procedure that comprises an adjustment of a center RF frequency, an estimation of an RF transmitter reference voltage, a B1 field shimming, a receive coil sensitivity mapping, and/or a B0 field shimming, and/or tin a preparatory scan; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure may be omitted, omitting the imaging preparation procedure; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure may be accelerated, executing the imaging preparation procedure at a standard duration or at the shortened duration that is less than the standard duration; and executing the imaging protocol to acquire the magnetic resonance image dataset, wherein (i) when the center RF frequency adjustment is to be omitted, setting the center RF frequency to a value determined in a previous center RF frequency adjustment, and/or (ii) when the B0 field shimming is to be omitted, using default shim settings.

2.-3. (canceled)

4. The method according to claim 1, wherein the preparatory scan comprises one or more dummy scans to establish a steady slate of magnetization and/or auto-calibration scans to estimate coil sensitivity maps.

5. The method according to claim 4, wherein, if the auto-calibration scans are to be omitted, coil sensitivity profiles are estimated from other sources, which include an adjustment scan; and/or wherein, if the auto-calibration scans are to be accelerated, the duration of the autocalibration scans is adjusted to be shorter by reducing a resolution of the auto-calibration scans.

6. The method according to claim 1, wherein the scan conditions comprise a duration of the imaging protocol, a scan-related option set by a user, a purpose of a scan of the imaging protocol, and/or a type of a scan mode of the imaging protocol.

7. The method according to claim 6, wherein the predetermined reference parameters are one or more of: a predetermined upper threshold of an imaging protocol duration, a databank of predetermined possible user input commands relating to scan conditions, a databank of purposes for different imaging protocols, and/or a databank of predetermined types of different scan modes.

8. The method according to claim 1, wherein the scan conditions comprise a duration of the imaging protocol, and further comprising: calculating a ratio of the duration of the imaging protocol to the standard duration of the imaging preparation procedure; comparing the ratio to a ratio threshold value; and determining, when the ratio is below the ratio threshold value, that the imaging preparation procedure is to be omitted or a duration of the imaging preparation procedure is to be shortened to a predetermined duration that is less than the standard duration.

9. The method according to claim 1, further comprising: comparing the determined scan conditions with the predetermined reference parameters; and determining whether the imaging preparation procedure is to be omitted and/or the imaging preparation procedure is to be accelerated using a database of comparison rules.

10. The method according to claim 1, wherein a user is enabled to input a speed-up request via a “Fast Scan” button, when or before selecting the imaging protocol, and wherein an input speed-up request is treated as scan condition.

11. The method according to claim 10, wherein the input speed-up request is treated as scan condition that requires the imaging preparation procedure to be omitted and/or accelerated.

12. The method according to claim 1, wherein the imaging protocol comprises one or more of parallel imaging techniques, a single shot, a multi-shot echo-planar imaging scan, a Half-Fourier-Acquired Single-shot Turbo spin Echo (HASTE) scan, and a Fast Low-Angle Shot (FLASH) acquisition.

13. A magnetic resonance imaging system for acquiring a magnetic resonance image dataset of a subject, the magnetic resonance system comprising a processor configured to execute instructions to cause the magnetic resonance imaging system to: determine scan conditions relating to an imaging protocol that is to be carried out on the subject; based on the scan conditions and/or on predetermined reference parameters, perform a determination of whether an imaging preparation procedure may be omitted or accelerated to have a shortened duration, the imaging preparation procedure comprising (i) a scanner adjustment procedure that comprises an adjustment of a center RF frequency, an estimation of an RF transmitter reference voltage, a B1 field shimming, a receive coil sensitivity mapping, and/or a B0 field shimming, and/or (ii) a preparatory scan; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure may be omitted, omit the imaging preparation procedure; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure, may be accelerated, execute the imaging preparation procedure at a standard duration or at the shortened duration that is less than the standard duration; and execute the imaging protocol to acquire the magnetic resonance image dataset, wherein when the center RF frequency adjustment is to be omitted, set the center RP frequency to a value determined in a previous center RF frequency adjustment, and/or (ii) when the B0 field shimming is to be omitted, use default shim settings.

14.-15. (canceled)

16. The magnetic resonance imaging system according to claim 13, wherein the preparatory scan comprises one or more dummy scans to establish a steady slate of a magnetization and/or auto-calibration scans to estimate coil sensitivity maps.

17. The magnetic resonance imaging system according to claim 16, wherein the processor is further configured to execute the instructions to cause the magnetic resonance imaging system to: if the auto-calibration scans are to be omitted, estimate coil sensitivity profiles estimated from other sources, including an adjustment scan; and/or if the auto-calibration scans are to be accelerated, adjusting a duration of the auto-calibration scans to be shorter by reducing a resolution of the auto-calibration scans.

18. The magnetic resonance imaging system according to claim 13, wherein the scan conditions comprise the duration of the imaging protocol, a purpose of a scan of the imaging protocol, and/or a type of a scan mode of the imaging protocol.

19. The magnetic resonance imaging system according to claim 18, wherein the predetermined reference parameters comprise one or more of: a predetermined upper threshold of an imaging protocol duration, a databank of predetermined possible user input commands relating to scan conditions, a databank of purposes for different imaging protocols, and/or a databank of predetermined types of different scan modes.

20. A non-transitory computer-readable medium having stored thereon a computer program which, when executed by a processor of a magnetic resonance imaging system for acquiring a magnetic resonance image dataset of a subject, causes the magnetic resonance imaging system to: determine scan conditions relating to an imaging protocol that is to be carried out on the subject; determine, based on the scan conditions and/or on predetermined reference parameters, whether an imaging preparation procedure may be omitted or accelerated to have a shortened duration, the imaging preparation procedure comprising (i) a scanner adjustment procedure that comprises an adjustment of a center RF frequency, an estimation of an RF transmitter reference voltage, a B1 field shimming, a receive coil sensitivity mapping, and/or a B0 field shimming, and/or (ii) a preparatory scan; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure may be omitted, omit the imaging preparation procedure; when the determination of whether the imaging preparation procedure may be omitted or accelerated indicates that the imaging preparation procedure may be accelerated execute the imaging preparation procedure at a standard duration or at the shortened duration that is less than the standard duration; and execute the imaging protocol to acquire the magnetic resonance image dataset, wherein (i) when the center RF frequency adjustment is to be omitted, set the center RF frequency to a value determined in a previous center RF frequency adjustment, and/or (ii) when the B0 field shimming is to be omitted, use default shim settings.

21. The method according to claim 1, wherein the scan conditions comprise an image quality associated with executing the imaging preparation procedure, and wherein the determining of whether the imaging preparation procedure may be omitted or accelerated is based upon the execution of the imaging protocol to acquire the magnetic resonance image dataset to provide images that meet a predefined threshold image quality that represents a reduction in image quality associated with executing the imaging preparation procedure at the standard duration.

22. The method according to claim 1, wherein the scan conditions comprise a duration of the imaging protocol, and wherein the determining of whether the imaging preparation procedure may be omitted or accelerated is based upon a proportion of the duration of the imaging protocol that is required to execute the imaging preparation procedure at the standard duration.

23. The method according to claim 9, wherein the database of comparison rules comprises conditions that specify conditions per type of imaging protocol.

24. The method according to claim 1, wherein the executing the imaging protocol to acquire the magnetic resonance image dataset comprises executing a plurality of imaging protocols, and wherein the imaging preparation procedure is omitted by using only one imaging preparation procedure prior to executing each of the plurality of imaging protocols.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The accompanying drawings illustrate various example methods and other example embodiments of various aspects of the invention.

[0059] FIG. 1 is a flow diagram of a method according to an embodiment of the invention;

[0060] FIG. 2 is a flow diagram of a method according to another embodiment of the invention; and

[0061] FIG. 3 is a schematic illustration of a magnetic resonance imaging system according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS WITH REFERENCE TO THE DRAWINGS

[0062] Similar elements are designated with the same reference signs in the drawings.

[0063] FIG. 1 shows a flow diagram of a method according to an embodiment of the invention. In a first step 101, scan conditions 10 relating to an imaging protocol 40 are determined. The imaging protocol 40 relates to acquiring a magnetic resonance image dataset of a subject with a magnetic resonance imaging system 1. The scan conditions 10 comprise a duration 11 of the imaging protocol 40, a scan-related option set by a user 12, a purpose of the scan 13, and a type of scan mode 14. In an optional step 105, a user may be enabled to input a speed-up request 15 which may then also be treated as a scan condition 10.

[0064] In the following step 102 the scan conditions 10 are compared to predetermined reference parameters 20 in order to determine, whether one or several imaging preparation procedures 30 may be omitted or accelerated to have a shortened duration 301. The predetermined reference parameters 20 comprise a predetermined upper threshold of an imaging protocol duration 21, a databank of predetermined possible user input commands relating to scan conditions 22, a databank of purposes for different imaging protocols 23, and a databank of known types of different scan modes 24. Several predetermined reference parameters 20 and scan conditions 10 may be taken into combined consideration in order to determine, whether the imaging preparation procedures 30 are to be accelerated and/or omitted. The imaging preparation procedures 30 may comprise at least one scanner adjustment procedure 31 and/or at least one preparatory scan 32. The at least one scanner adjustment procedure 31 may comprise one or several of an adjustment of the center RF frequency 33, an estimation of an RF transmitter reference voltage 34, a B1 field shimming, a receive coil sensitivity mapping, and/or a B0 field shimming 35. The at least one preparatory scan 32 may comprise one or several of auto-calibration scans 36 to estimate coil sensitivity maps and/or dummy scans 37 to establish a steady state of the magnetization. In particular, a database of comparison rules is used to determine whether the imaging preparation procedures 30 are to be omitted 302 and/or whether the imaging preparation procedures 30 are to be accelerated 301. For example, the ratio of the duration 11 of the imaging protocol 40 to a standard duration 300 of at least one of the imaging preparation procedures 30 may be calculated. This ratio is compared to a ratio threshold value and, when the ratio is below the ratio threshold value, the at least one imaging preparation procedure 30 is determined to be omitted 302 or its duration to be shortened to a shortened duration 301 below the standard duration 300.

[0065] In the following step 103, depending on the determination of step 102, the imaging preparation procedures 30 are omitted 302 or carried out at the standard duration 300 or at the shortened duration 301. When an imaging preparation procedure 30 is omitted 302, it may either be completely omitted or replaced by an alternative measure. For example, when the center RF frequency adjustment 33 is to be omitted 302, the center RF frequency may be set to a value determined in a previous center RF frequency adjustment 332. When the B0 field shimming 35 is to be omitted 302, default shim settings may be used 352. When the auto-calibration scans 36 are to be omitted 302, coil sensitivity profiles may be estimated from other sources 362, in particular from an adjustment scan. Acceleration may generally be achieved by simply reducing the duration of the procedure and/or by reducing the resolution. For example, the B0 field shimming 35 may be accelerated by reducing the resolution of the shim adjustment scan 351. Furthermore, if the auto-calibration scans 36 are to be accelerated 301, the duration of the auto-calibration scans may be adjusted to be shorter by reducing the resolution of the auto-calibration scans 361.

[0066] Finally, after carrying out and/or omitting the imaging preparation procedures 30, the imaging protocol 40 is carried out in order to acquire the magnetic resonance image dataset in step 104. The imaging protocol 40 may be a fast imaging protocol, in particular the imaging protocol may use parallel imaging techniques and/or may comprise a multi-shot echoplanar imaging scan, a Fast Low-Angle Shot (FLASH) acquisition and/or a Half-Fourier-Acquired Single-shot Turbo spin Echo (HASTE) scan.

[0067] FIG. 2 shows a flow diagram of a method according to another embodiment of the invention. In this embodiment, there are four data acquisition cycles 201-204 that are carried out consecutively. The purpose of these cycles is a brain examination that consists of four imaging protocols 40 which may acquire different contrasts. The first cycle 201 comprises a multi-shot GRE-EPI (gradient echo—echoplanar imaging) scan 41 with inversion-recovery preparation for acquiring images with T1 contrast in about 25 seconds. Additionally and/or alternatively, the first cycle 201 may comprise a GRE (FLASH) acquisition. The second cycle 202 comprises a multi-shot-multi-echo GRE/SE-EPI (gradient echo/spin echo—echoplanar imaging) scan 42 for acquiring images with T2* and T2 contrast in about 25 seconds. The third cycle comprises a multishot SE-EPI (spin echo—echoplanar imaging) scan 43 with inversion-recovery preparation for acquiring images with T2-FLAIR (fluid attenuated inversion recovery) contrast in about 50 seconds. The fourth cycle comprises a single-shot DW-SE-EPI (diffusion weighted—spin echo—echoplanar imaging) scan 44 for acquiring images with diffusion contrast and ADC (apparent diffusion coefficient) maps in about 20 seconds. All scans 41-44 get acquired with parallel imaging techniques (e.g. GRAPPA) which require ACS (auto-calibration scans) lines. The user interface provides a corresponding element in step 105 which allows the user to select different ACS acquisition modes, including in this embodiment, demanding a speed-up request 15 or selecting a standard speed, i.e., no speed-up request 16. In step 101 the user request is treated as scan condition 10 and used in the following step 102 to determine whether imaging preparation procedures 30 are to be omitted or accelerated to have a shortened duration. For this purpose, predetermined reference parameters are the information that a speed-up request will lead to an acceleration 301 and/or omission 302 of at least one imaging preparation procedure 30, while no speed-up request will lead to applying the imaging preparation procedures 30 with a standard duration 300.

[0068] In step 103 of the cycles 201-204, if the user selects no speed-up request 16, ACS lines get acquired with high resolution (e.g., the number of columns matching that of the imaging scans) in order to obtain maximum quality at the expense of a longer scan duration. At the same time, imaging preparation procedures with a standard duration 300 which maximize image quality at the expense of a longer examination duration are used. For example, dummy scans 37 may get requested for a minimum of 4 seconds according to a standard duration 300, and the total duration is typically a multiple of the selected imaging TR.

[0069] If the user selects a speed-up request 15, ACS lines get acquired with reduced resolution 361 (e.g., just 24 columns) in order to reduce 301 the ACS acquisition time at the expense of a reduced unaliasing performance. Furthermore, enabling the speed-up request 16 will simultaneously trigger the following accompanying changes in order to speed up the total scan time. First, according to this embodiment, during acquisition cycles 202-204, the center frequency from the first acquisition cycle 201 will be used 332. The adjustment of the center RF frequency 33 is omitted 302 during the second to fourth cycle 202-204. Hence an adjustment of the center RF frequency 33 will only be carried out during step 103 of the first cycle 201. Rather than running a frequency adjustment 33 before each imaging protocol 40, a frequency adjustment 33 gets executed only once at the beginning. This may reduce the total examination time by 3 times the duration of the adjustment (e.g., ˜10 seconds). Second, during all cycles 201-204, the minimum dummy preparation scan duration will be reduced 371, e.g., to 2 seconds (rather than e.g., 4 sec).

[0070] FIG. 3 shows a schematic illustration of a magnetic resonance imaging system 1 according to an embodiment of the invention. The system 1 comprises a processing unit 2 configured to carry out operations according to the method described above. The operations are stored on a non-transitory computer-readable medium that is part of the processing unit 2.