MR Imaging with Optimized Imaging Workflow

Abstract

An MR imaging method with an imaging workflow is provided. Within the scope of the MR imaging method, at least one breath-holding command is output to a patient. An MR imaging is performed with an MR imaging method that may be used with free breathing. A breathing movement of the patient is detected based on measured data acquired when performing the MR imaging method. A time relationship is determined between the breathing movement of the patient and the breath-holding command. The imaging workflow is modified as a function of the determined time relationship. A breathing monitoring device and a magnetic resonance imaging system are also provided.

Claims

1. A magnetic resonance (MR) imaging method with an imaging workflow, the method comprising: outputting at least one breath-holding command to a patient; performing an MR imaging with an MR imaging method that is usable with free breathing; detecting a breathing movement of the patient based on measured data acquired when performing the MR imaging method; determining a time relationship between the breathing movement of the patient and the breath-holding command; and modifying the imaging workflow as a function of the determined time relationship.

2. The MR imaging method of claim 1, wherein determining the time relationship comprises determining the time relationship as to whether the patient has actually realized the breath-holding command; and wherein modifying the imaging workflow comprises deciding whether the breath-holding command is to be entirely omitted.

3. The MR imaging method of claim 1, wherein determining the time relationship comprises determining with which time difference the breath holding command was performed by the patient, and wherein modifying the imaging workflow comprises deciding whether and how a time instant of the breath-holding command is to be modified, whether and how a start time instant of the MR imaging is to be modified, or a combination thereof.

4. The MR imaging method of claim 3, wherein the determining of the time difference takes place in advance in a test run, and the subsequent MR imaging is performed by taking the determined time difference into account.

5. The MR imaging method of claim 4, wherein the MR imaging method is performed in a contrast-agent supported manner, wherein the method further comprises: acquiring a test bolus; determining a time instant of arrival of the test bolus in an area to be examined, and wherein the MR imaging method is performed by also taking the determined time instant of the arrival of the test bolus into account.

6. The MR imaging method of claim 5, wherein in the MR imaging method, a time instant of outputting the breath holding command is selected such that an expected time instant of the patient holding the breath coincides with a time instant of arrival of a contrast agent bolus.

7. The MR imaging method of claim 1, wherein an imaging method with an iterative reconstruction technique is used as the MR imaging method.

8. The MR imaging method of claim 7, wherein the MR imaging method includes radial scanning.

9. The MR imaging method of claim 8, wherein the MR imaging method comprises an iGRASP imaging method.

10. The MR imaging method of claim 1, wherein detecting the breathing movement of the patient takes place based on raw data resulting from acquired MR signals.

11. The MR imaging method of claim 1, wherein the imaging workflow is a clocked workflow.

12. A breathing monitoring device comprising: a command output unit configured to output a breath-holding command to a patient to hold breath; a start command output unit configured to start a magnetic resonance (MR) imaging with an MR imaging method that is usable with free breathing; a breathing movement detection unit configured to detect a breathing movement of the patient based on measured data acquired when performing the MR imaging method; a time relationship determination unit configured to determine a time relationship between the breathing movement of the patient and the breath-holding command; and a modification unit configured to modify the imaging workflow as a function of the determined time relationship.

13. A magnetic resonance imaging system comprising: a radio-frequency transmit system; a gradient system; and a controller configured, in order to perform a desired measurement based on a predetermined pulse sequence, to actuate the radio-frequency transmit system and the gradient system; and a breathing monitoring device comprising: a command output unit configured to output a breath-holding command to a patient to hold breath; a start command output unit configured to start a magnetic resonance (MR) imaging with an MR imaging method that is usable with free breathing; a breathing movement detection unit configured to detect a breathing movement of the patient based on measured data acquired when performing the MR imaging method; a time relationship determination unit configured to determine a time relationship between the breathing movement of the patient and the breath-holding command; and a modification unit configured to modify the imaging workflow as a function of the determined time relationship.

14. A computer program product comprising a non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium storing instructions executable by a computer of a magnetic resonance imaging system for a magnetic resonance (MR) imaging with an imaging workflow, the instructions comprising: outputting at least one breath-holding command to a patient; performing an MR imaging with an MR imaging method that is usable with free breathing; detecting a breathing movement of the patient based on measured data acquired when performing the MR imaging method; determining a time relationship between the breathing movement of the patient and the breath-holding command; and modifying the imaging workflow as a function of the determined time relationship.

15. In a non-transitory computer-readable storage medium that stores instructions executable by a computer of a magnetic resonance imaging system for a magnetic resonance (MR) imaging with an imaging workflow, the instructions comprising: outputting at least one breath-holding command to a patient; performing an MR imaging with an MR imaging method that is usable with free breathing; detecting a breathing movement of the patient based on measured data acquired when performing the MR imaging method; determining a time relationship between the breathing movement of the patient and the breath-holding command; and modifying the imaging workflow as a function of the determined time relationship.

16. The non-transitory computer-readable storage medium of claim 15, wherein determining the time relationship comprises determining the time relationship as to whether the patient has actually realized the breath-holding command; and wherein modifying the imaging workflow comprises deciding whether the breath-holding command is to be entirely omitted.

17. The non-transitory computer-readable storage medium of claim 15, wherein determining the time relationship comprises determining with which time difference the breath holding command was performed by the patient, and wherein modifying the imaging workflow comprises deciding whether and how a time instant of the breath-holding command is to be modified, whether and how a start time instant of the MR imaging is to be modified, or a combination thereof.

18. The non-transitory computer-readable storage medium of claim 17, wherein the determining of the time difference takes place in advance in a test run, and the subsequent MR imaging is performed by taking the determined time difference into account.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows a flow diagram that illustrates a contrast-enhanced MR imaging method according to an exemplary embodiment;

[0029] FIG. 2 shows a flow diagram that illustrates a contrast-enhanced MR imaging method according to a second exemplary embodiment;

[0030] FIG. 3 shows a block diagram that illustrates a breathing monitoring device according to an exemplary embodiment; and

[0031] FIG. 4 shows a magnetic resonance imaging system according to an exemplary embodiment.

DETAILED DESCRIPTION

[0032] FIG. 1 shows a flow diagram 100 that illustrates a contrast-enhanced magnetic resonance (MR) imaging method according to an exemplary embodiment. In act 1.I, an acoustic command AAH(t.sub.AAH) to the patient to hold his/her breathing movement is issued firstly automatically at a time instant t.sub.AAH. In this exemplary embodiment, this occurs within the scope of a clocked workflow. In act 1.II, a contrast-enhanced MR imaging BG(t.sub.MR) that also delivers an acceptable image quality with free breathing is then started at a time instant t.sub.MR. A contrast agent was provided in advance for the contrast-enhanced imaging. An iGRASP method may be used as an imaging method, for example. In act 1.III, it is determined whether the breath-holding command AAH is actually realized. This may take place based on measurement data acquired with the aid of the iGRASP method. For example, the raw data of the k-space center acquired with the MR image recording is used as a breathing signal (e.g., as proof as to whether or not a breathing movement has taken place). In the case that there has been absolutely no holding of breath, which is indicated in FIG. 1 with “n”, a move is made to act 1.IV. In act 1.IV, the MR imaging is then continued entirely without the breath-holding command AAH and finally terminated. Since an iGRASP method that is particularly robust with regard to a breathing movement of a patient is used for the MR imaging, despite omitting the breath-holding commands conventional for the clocked workflow, an acceptable image quality is achieved.

[0033] If it was detected that breath was being held, which is identified in FIG. 1 with “y”, a move is made to act 1.I, in which the time instant t.sub.u at which the breath-holding command AAH was realized by the patient is determined. Then in act 1.VI, a time instant t.sub.AAH of a breath-holding command AAH is adjusted to the reaction time t.sub.u of the patient, whereby the following applies

t.sub.AAH=t.sub.MR−t.sub.u.  (1)

[0034] A check is carried out in act 1.VII to determine whether the imaging is to be terminated, for example, because sufficient measurement data was already acquired. If this is the case, which is indicated in FIG. 1 with “y”, the imaging is terminated in act 1.VIII. If the imaging has still not come to an end, which is indicated in FIG. 1 with “n”, a move back to act 1.I is made, and a breath-holding command is output at the new time instant t.sub.AAH(t.sub.u), etc.

[0035] A flow diagram 200 is shown in FIG. 2, which illustrates a contrast-enhanced MR imaging method according to a second exemplary embodiment. In this variant, a type of upstream test run is used to determine both the reaction time t.sub.u of the patient and also the bolus time t.sub.B during which a contrast agent bolus arrives at an area to be examined. The time instant of starting the imaging t.sub.MR and the time instant t.sub.AAH of outputting the breath-holding command may thus be attuned to the determined times t.sub.u, t.sub.B. Before starting the method, a test bolus is given to the patient. In other words, a small quantity of contrast agent is injected into the patient in advance. In act 2.I, a breath-holding command AAH is given to the patient. Then an MR test imaging MR-TBG is started in act 2.II at a test start time instant t.sub.MR. A reaction time t.sub.u of the patient to the breath-holding command AAH is determined in act 2.III based on the recorded test images. A time t.sub.B is determined in act 2.IV based on the measurement data recorded in the test imaging MR-TBG, at which the test bolus has arrived at an area to be examined. In act 2.V, the actual contrast-enhanced imaging MR-BG takes place with a breath-holding command, which is attuned to the determined times t.sub.B, t.sub.u. For example, the time instant of starting the imaging t.sub.MR and the time instant t.sub.AAH of outputting the breath-holding command are thus attuned to the determined times t.sub.u, t.sub.B. The subsequent MR image recording is then started at time instant t.sub.MR if the contrast agent bolus has arrived at an area to be examined. The following thus applies:

t.sub.MR=t.sub.B.  (2)

[0036] Together with the equation 1, the following results for the time instant t.sub.AAH of the breath-holding command:

t.sub.AAH=t.sub.B−t.sub.u.  (3)

[0037] In this way, the arrival of the contrast agent bolus in the area to be examined and the image recording and the resting breathing state of the patient are synchronized so that a good image quality is to be expected with an increased contrast.

[0038] A breathing monitoring device 30 according to an exemplary embodiment is shown schematically in FIG. 3. The breathing monitoring device 30 may be, for example, part of a control device of a magnetic resonance imaging system (see FIG. 4). The breathing monitoring device 30 includes a data acquisition unit 31 that receives raw data RD or also image data BD of an area to be examined, for example, acquired or reconstructed within the scope of an MR imaging method. The data RD, BD is transferred to a breathing movement detection unit 32. The breathing movement detection unit 32 evaluates the acquired data RD, BD in order to determine whether and at which time instant a breath-holding command was performed by a patient. For example, a k-space center signal (e.g., raw data) acquired from the k-space center with the aid of the magnetic resonance imaging method may be evaluated herefor.

[0039] The breathing movement detection unit 32 includes a time relationship determination unit 33 for determining a time relationship between the breathing movement of the patient and the breath-holding command AAH. For this purpose, the time relationship determination unit 33 determines a time instant at the start of a resting breathing state based on the acquired raw data RD or image data BD. The time relationship determination unit 33 determines a time difference to between the time instant t.sub.AAH of outputting the breath-holding command AAH and the reaction of the patient. The breathing movement detection unit 32 includes a modification unit 34 for modifying the imaging workflow as a function of the determined time relationship. In other words, the modification unit 34 determines correction parameters based on the time difference t.sub.u. Correction parameters may have, for example, a modified start time t.sub.MR of an MR imaging or a modified time instant t.sub.AAH of outputting a breath-holding command AAH.

[0040] After evaluating the acquired data RD, BD, the breathing movement detection unit 32 outputs information relating to a modified time instant t.sub.AAH of outputting a breath-holding command AAH to a command output unit 35 or alternatively also a command in order to set the output of breath-holding commands AAH entirely. The breathing movement detection unit 32 is also connected to a start command output unit 36. The start command output unit 36 outputs a command SB to start an MR imaging with an MR imaging method that may be used with free breathing. The time instant t.sub.MR for outputting the start command SB is, as already explained, likewise determined by the breathing movement detection unit 32 and transferred to the start command output unit 36.

[0041] As already mentioned, the time instant t.sub.MR for outputting the start command SB and thus the start time instant t.sub.MR of the imaging may be associated with the time instant t.sub.B of the arrival of a contrast agent bolus. For example, the time instant t.sub.B of the arrival of the contrast agent may be determined by an MR test imaging MR-TBG performed in advance (e.g., prior to the actual contrast agent imaging). The breathing monitoring device 30 also includes an output interface 37 for outputting received image data BD or received raw data RD, which includes breathing movement data that is forwarded to a display unit (not shown), for example, for graphical representation or to another processing unit for further processing.

[0042] One embodiment of a magnetic resonance system 1 is shown roughly schematically in FIG. 4 (abbreviated below to “MR system”). The magnetic resonance system 1 includes the actual magnetic resonance scanner 2 with an examination space 3 or patient tunnel, into which an examination object O or a patient or test subject may be introduced on a couch 8. The examination object or the examination area (e.g., a specific organ) may be located in the patient or the test subject.

[0043] The magnetic resonance scanner 2 is equipped in the usual manner with a main field magnet system 4, a gradient system 6, and an RF transmitting antenna system 5 and an RF receiving antenna system 7. In the exemplary embodiment shown, the RF transmitting antenna system 5 is a whole body coil fixedly incorporated in the magnetic resonance scanner 2, whereas the RF receiving antenna system 7 consists of local coils to be arranged on the patient or test subject (in FIG. 4 symbolized only by a single local coil). The whole-body coil may be used as an RF receiving antenna system, and the local coils may be used as an RF transmitting antenna system. These coils may each be switched to different operating modes.

[0044] The MR system 1 also has a central control device 13 that is used for controlling the MR system 1. This central control device 13 includes a sequence control unit 14 for pulse sequence control. With this, the sequence of radio-frequency pulses (RF pulses) and gradient pulses may be controlled depending on a selected imaging sequence. Such an imaging sequence may be predefined, for example, within a measurement or control protocol. Normally, different control protocols are stored in a memory 19 for different measurements and may be selected by an operator (and where appropriate, altered if need be) and then used to perform the measurement.

[0045] For the output of the individual RF pulses, the central control device 13 has a radio-frequency transmitting device 15 that generates the RF pulses, amplifies the RF pulses, and feeds the RF pulses by a suitable interface (not shown in detail) to the RF transmitting antenna system 5. In order to control the gradient coils of the gradient system 6, the control device 13 has a gradient system interface 16. The sequence control unit 14 communicates in a suitable manner, for example, by transmission of sequence control data SD, with the radio-frequency transmitting device 15 and the gradient system interface 16 for transmission of the pulse sequence. The control device 13 also has a radio-frequency receiving device 17 (also communicating in a suitable manner with the sequence control unit 14) in order to acquire magnetic resonance signals (e.g., raw data) in a coordinated manner from the RF transmitting antenna system 7. A reconstruction unit 18 takes over the acquired raw data and reconstructs the MR image data therefrom. This image data may then be stored in a memory 19, for example. The acquired raw data RD or the reconstructed image data BD is further processed in a breathing monitoring device 30 to control and monitor an MR imaging. The breathing monitoring device 30 provides a control command SB to the sequence control unit 14, for example, to start an MR image recording sequence with the aid of the output of sequence control data SD. The breathing monitoring device 30 also includes a connection to an audio communication unit 11 on the magnetic resonance scanner 2 to transmit breath-holding instructions AAH to the patient O.

[0046] The central control device 13 may be operated via a terminal with an input unit 10 and a display unit 9, by which the whole MR system 1 may thus also be operated by an operating person. MR images may also be displayed on the display unit 9, and using the input unit 10, if appropriate in combination with the display unit 9, measurements may be planned and initiated, and for example, suitable control protocols with suitable measurement sequences as explained above may be selected and, if appropriate, modified.

[0047] The MR system 1 and the control device 13 may also include a plurality of other components that are not shown individually but are normally present in such systems (e.g., a network interface to link the whole system to a network, and to be able to exchange raw data and/or image data, as well as other data such as patient-related data or control protocols).

[0048] How suitable raw data may be acquired and MR images therefrom may be reconstructed through the irradiation of RF pulses and the generation of gradient fields is known to the person skilled in the art and will not be described in greater detail here. Similarly, a variety of measurement sequences, such as, for example, EPI measurement sequences or measurement sequences for generating diffusion-weighted images, are known to the person skilled in the art.

[0049] The methods and devices described above are merely exemplary embodiments, and the invention can be varied by a person skilled in the art without departing from the scope of the invention as defined by the claims. Therefore, the method and the breathing monitoring device 30 were primarily explained in conjunction with a contrast agent-supported recording of medical image data. The invention is, however, not restricted to an MR image recording combined with a contrast agent provided in advance. The invention may instead also essentially be applied to the recording of images without additional administration of contrast agents. For the sake of completeness, the use of the indefinite article “a” or “an” does not preclude the relevant feature from also being present plurally. Similarly, the expression “unit” does not preclude this consisting of a plurality of components that may also be spatially distributed.

[0050] The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

[0051] While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.