ACCELERATION OF MRI EXAMINATIONS

Abstract

The disclosure relates to the acceleration of MRI examinations, particularly during the detection and differential diagnosis of focal liver lesions by way of dynamic contrast-enhanced magnetic resonance imaging (MRI). The disclosure also relates to a method, a system and a computer program product for generating MRI images, particularly of the liver.

Claims

1. A computer-implemented method comprising: receiving a first MRI image of an examination object, wherein the first MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent, receiving a second MRI image of the same examination object, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, generating a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first MRI picture compared to the second MRI image, and displaying and/or outputting the first MRI picture and/or storing the first MRI picture in a data storage medium and/or outputting the first MRI picture to a printer.

2. The method of claim 1, wherein the first MRI picture shows the same liver or the same part of the liver after the administration of the second contrast agent, wherein the contrast enhancement of healthy liver cells caused by the first contrast agent has been eliminated.

3. The method of claim 1, further comprising: receiving the first MRI image of the examination object, wherein the first MRI image shows the liver or the part of a liver of the examination object during a first hepatobiliary phase at the first time point after the administration of the first contrast agent, receiving the second MRI image of the same examination object, wherein the second MRI image shows the same liver or the same part of the liver during a second arterial phase at the second time point after the administration of the second contrast agent, optionally receiving a third MRI image of the same examination object, wherein the third MRI image shows the same liver or the same part of the liver during a second portal venous phase at a third time point after the administration of the second contrast agent, optionally receiving a fourth MRI image of the same examination object, wherein the fourth MRI image shows the same liver or the same part of the liver during a second late phase at a fourth time point after the administration of the second contrast agent, generating MRI pictures from the received MRI images, wherein the first MRI picture is calculated by subtraction of the first MRI image from the second MRI image, wherein optionally a second MRI picture is calculated by subtraction of the first MRI image from the third MRI image, wherein optionally a third MRI picture is calculated by subtraction of the first MRI image from the third MRI image, and displaying and/or outputting one or more of the generated MRI pictures and/or storing one or more of the generated MRI pictures in the data storage medium and/or outputting one or more of the generated MRI pictures to a printer.

4. The method of claim 1, further comprising: feeding the first MRI image and the second MRI image to an artificial neural network, wherein the artificial neural network has been trained in a supervised learning process to generate third reference MRI images from first reference MRI images and second reference MRI images, wherein each first reference MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first reference MRI image at the first time point as a consequence of the administration of the first contrast agent, wherein each second reference MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, and wherein each third reference MRI image shows the same liver or the same part of the liver at the second time point after the administration of the second contrast agent, wherein only blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, wherein healthy liver cells are not depicted with contrast enhancement.

5. The method of claim 1, wherein the first contrast agent is a hepatobiliary contrast agent, preferably a substance or a substance mixture having gadoxetic acid or a salt of gadoxetic acid as contrast-enhancing active substance, and the second contrast agent is either the same contrast agent as the first contrast agent or an extracellular contrast agent, preferably a substance or a substance mixture having gadobutrol, gadoteridol, gadoteric acid, gadopentetic acid or gadodiamide as contrast-enhancing active substance.

6. A system comprising: a receiving unit, a control and calculation unit and an output unit, wherein the control and calculation unit is configured to prompt the receiving unit to receive a first MRI image of an examination object, wherein the first Mill image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent, wherein the control and calculation unit is configured to prompt the receiving unit to receive a second Mill image of an examination object, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, wherein the control and calculation unit is configured to generate a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first MRI picture compared to the second MRI image, and wherein the control and calculation unit is configured to prompt the output unit to display the first MRI picture, to output it to a printer or to store it in a data storage medium.

7. The computer system of claim 6, wherein the control and calculation unit is configured to prompt the receiving unit to receive a first MRI image, a second MRI image, a third MRI image and a fourth MRI image, wherein the first MRI image shows the liver or the part of the liver of the examination object during a first hepatobiliary phase at the first time point after the administration of the first contrast agent, wherein the second MRI image shows the same liver or the same part of the liver during a second arterial phase at the second time point after the administration of the second contrast agent, wherein the third MRI image shows the same liver or the same part of the liver during a second portal venous phase at a third time point after the administration of the second contrast agent, wherein the fourth MRI image shows the same liver or the same part of the liver during a second late phase at a fourth time point after the administration of the second contrast agent, wherein the control and calculation unit is configured to generate MRI pictures from the received MRI images, wherein a first generated MRI picture is calculated by subtraction of the first MRI image from the second MRI image, wherein a second generated MRI picture is calculated by subtraction of the first MRI image from the third MRI image, wherein a third generated MRI picture is calculated by subtraction of the first MRI image from the third MRI image, and wherein the control and calculation unit is configured to prompt the output unit to display one or more of the generated MRI pictures and/or to output them to a printer and/or to store them in the data storage medium.

8. A computer program product comprising a computer program which can be loaded into a memory of a computer system, where it prompts the computer system to execute the following: receiving a first MRI image of an examination object, wherein the first MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent, receiving a second MRI image, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, generating a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first MRI picture compared to the second MRI image, and displaying the first MRI picture and/or storing the first MRI picture in a data storage medium and/or outputting the first MRI picture to a printer.

9. The computer program product of claim 8, further comprising: receiving the first MRI image of the examination object, wherein the first MRI image shows the liver or the part of the liver of the examination object during a first hepatobiliary phase at the first time point after the administration of the first contrast agent, receiving the second MRI image, wherein the second MRI image shows the same liver or the same part of the liver during a second arterial phase at the second time point after the administration of the second contrast agent, receiving a third MRI image, wherein the third MRI image shows the same liver or the same part of the liver during a second portal venous phase at a third time point after the administration of the second contrast agent, receiving a fourth MRI image, wherein the fourth MRI image shows the same liver or the same part of the liver during a second late phase at a fourth time point after the administration of the second contrast agent, generating MRI pictures from the received MRI images, wherein the first generated MRI picture is calculated by subtraction of the first MRI image from the second MRI image, wherein a second generated MRI picture is calculated by subtraction of the first MRI image from the third MRI image, wherein a third generated MRI picture is calculated by subtraction of the first MRI image from the third MRI image, and displaying one or more of the generated MRI pictures and/or storing one or more of the generated MRI pictures in the data storage medium and/or outputting one or more of the generated MRI pictures to a printer.

10. The computer program product of claim 9, further comprising feeding the first MRI image and the second MRI image to an artificial neural network, wherein the artificial neural network has been trained in a supervised learning process to generate third reference MRI images from first reference MRI images and second reference MRI images, wherein each first reference MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first reference MRI image at the first time point as a consequence of the administration of the first contrast agent, wherein each second reference MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, and wherein each third reference MRI image shows the same liver or the same part of the liver at the second time point after the administration of the second contrast agent, wherein only blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, wherein healthy liver cells are not depicted with contrast enhancement.

11. Use of a first and a second contrast agent in an MRI method, wherein the MRI method comprises: administering the first contrast agent, receiving a first MRI image, wherein the first MRI image shows a liver or part of a liver at a first time point after the administration of the first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent, administering the second contrast agent at a second time point after the first MRI image is received, receiving a second MRI image, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after the administration of the second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent, generating a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first Mill picture compared to the second MRI image, and displaying one or more of the generated MRI pictures and/or storing one or more of the generated MRI pictures in a data storage medium and/or outputting one or more of the generated MRI pictures to a printer.

12. The use of the first and second contrast agent of claim 11, wherein the first MRI image shows the liver or the part of the liver of the examination object during a first hepatobiliary phase at the first time point after the administration of the first contrast agent, wherein the second MRI image shows the same liver or the same part of the liver during a second arterial phase at the second time point after the administration of the second contrast agent, further comprising: receiving a third MRI image, wherein the third MRI image shows the same liver or the same part of the liver during a second portal venous phase at a third time point after the administration of the second contrast agent, receiving a fourth MRI image, wherein the fourth MRI image shows the same liver or the same part of the liver during a second late phase at a fourth time point after the administration of the second contrast agent, generating MRI pictures from the received MRI images, wherein the first MRI picture is calculated by subtraction of the first MRI image from the second MRI image, wherein a second MRI picture is calculated by subtraction of the first MRI image from the third MRI image, wherein a third MRI picture is calculated by subtraction of the first MRI image from the third MRI image, and displaying one or more of the generated MRI pictures and/or storing one or more of the generated MRI pictures in the data storage medium and/or outputting one or more of the generated MRI pictures to a printer.

13. (canceled)

14. The use of the first and second contrast agent of claim 11, wherein the first contrast agent is a hepatobiliary contrast agent, preferably a substance or a substance mixture having gadoxetic acid or a salt of gadoxetic acid as contrast-enhancing active substance, and the second contrast agent is either the same contrast agent as the first contrast agent or an extracellular contrast agent, preferably a substance or a substance mixture having gadobutrol, gadoteridol, gadoteric acid, gadopentetic acid or gadodiamide as contrast-enhancing active substance.

15. A kit comprising one or more contrast agents according to claim 11 and a computer program product according to claim 8.

16. The use of the first and second contrast agent of claim 12, wherein the first contrast agent is a hepatobiliary contrast agent, preferably a substance or a substance mixture having gadoxetic acid or a salt of gadoxetic acid as contrast-enhancing active substance, and the second contrast agent is either the same contrast agent as the first contrast agent or an extracellular contrast agent, preferably a substance or a substance mixture having gadobutrol, gadoteridol, gadoteric acid, gadopentetic acid or gadodiamide as contrast-enhancing active substance.

Description

[0210] The disclosure is elucidated in detail hereinbelow with reference to figures, without any intention to restrict the disclosure to the features or combinations of features shown in the figures.

[0211] In the figures:

[0212] FIG. 1 shows schematically the temporal profile of the concentrations of contrast agent in the liver arteries (A), the liver veins (P) and the liver cells (L). The concentrations are depicted in the form of the signal intensities I in the stated areas (liver arteries, liver veins, liver cells) in the magnetic resonance measurement as a function of the time t. Upon an intravenous bolus injection, the concentration of the contrast agent rises in the liver arteries (A) first of all (dashed curve). The concentration passes through a maximum and then drops. The concentration in the liver veins (P) rises more slowly than in the liver arteries and reaches its maximum later (dotted curve). The concentration of the contrast agent in the liver cells rises slowly (solid curve) and reaches its maximum only at a very much later time point (not depicted in FIG. 1). A few characteristic time points can be defined: At time point TP0, contrast agent is administered intravenously as a bolus. At time point TP1, the concentration (the signal intensity) of the contrast agent in the liver arteries reaches its maximum. At time point TP2, the curves of the signal intensities for the liver arteries and the liver veins intersect. At time point TP3, the concentration (the signal intensity) of the contrast agent in the liver veins passes through its maximum. At time point TP4, the curves of the signal intensities for the liver arteries and the liver cells intersect. At time point T5, the concentrations in the liver arteries and the liver veins have dropped to a level at which they no longer cause a measurable contrast enhancement.

[0213] According to the disclosure, contrast agent is administered in the form of two boluses. A first bolus containing a first contrast agent is administered at time point TP0, and a second bolus containing a second contrast agent is administered at a time point after time point TP3, preferably after time point TP4, even more preferably after time point TP5. A first MRI image is preferably generated after time point TP4, even more preferably after time point TP5. After the administration of the second contrast agent, at least the arterial phase and the portal venous phase are passed through a second time. These phases are characterized by an analogous concentration profile of contrast agent in the arteries and the liver veins, i.e. the time points TP1 (maximum contrast enhancement of the arteries), TP2 (equal contrast enhancement of arteries and veins) and TP3 (maximum contrast enhancement of the veins) occur a second time; they can be referred to as time points TP1′, TP2′ and TP3′. Preferably, a second MRI image and possibly a third MRI image and possibly further MRI images are generated within a time span between the time point of administration of the second contrast agent and time point TP3′.

[0214] FIG. 2 shows schematically an example of an MRI examination shortened according to the disclosure. Here, a first contrast agent is first administered in the form of a first bolus (1). The examination object is passed to MRI after a certain waiting period (2), for example 8 to 20 minutes. Thereafter, the MRI process is started and a first MRI image (3) showing the liver of the examination object or part of said liver in the hepatobiliary phase is generated. Thereafter, a second contrast agent is administered intravenously in the form of a bolus injection (4) to the examination object and subsequently one or more further MRI images of the liver or part of said liver in the dynamic phase are generated.

[0215] FIG. 3 shows schematically a preferred embodiment of the system according to the disclosure. The system (10) comprises a receiving unit (11), a control and calculation unit (12) and an output unit (13).

[0216] The control and calculation unit (12) is configured to prompt the receiving unit (11) to receive a first MRI image of an examination object, wherein the first MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent.

[0217] The control and calculation unit (12) is further configured to prompt the receiving unit (11) to receive a second MRI image of an examination object, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent.

[0218] The control and calculation unit (12) is further configured to generate a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first MRI picture compared to the second MRI image.

[0219] The control and calculation unit (12) is further configured to prompt the output unit (13) to display the first MRI picture, to output it or to store it in a data storage medium.

[0220] FIG. 4 shows schematically and exemplarily one embodiment of the method according to the disclosure. The method (100) comprises the steps of:

[0221] (110) receiving a first MRI image of an examination object, wherein the first MRI image shows a liver or part of a liver of the examination object at a first time point after an administration of a first contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the first MRI image at the first time point as a consequence of the administration of the first contrast agent,

[0222] (120) receiving a second MRI image of the same examination object, wherein the second MRI image shows the same liver or the same part of the liver at a second time point after an administration of a second contrast agent, wherein healthy liver cells are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the first contrast agent, and wherein blood vessels are depicted with contrast enhancement in the second MRI image at the second time point as a consequence of the administration of the second contrast agent,

[0223] (130) generating a first MRI picture from the first MRI image and the second MRI image, wherein the first MRI picture shows the same liver or the same part of the liver at the second time point, wherein the contrast between healthy liver cells and blood vessels is increased in the first MRI picture compared to the second MRI image,

[0224] (140) displaying and/or outputting the first MRI picture and/or storing the first MRI picture in a data storage medium.

[0225] FIG. 5 shows MRI images of a liver during the dynamic and the hepatobiliary phase. In FIGS. 5 (a), 5 (b), 5 (c), 5 (d), 5 (e) and 5 (f), the same cross section through the liver is always depicted at different time points. The reference signs entered in FIGS. 5 (a), 5 (b), 5 (d) and 5 (f) apply to all of FIGS. 5 (a), 5 (b), 5 (c), 5 (d), 5 (e) and 5 (f); they are each entered only once merely for the sake of clarity.

[0226] FIG. 5 (a) shows the cross section through the liver (L) before the intravenous administration of a (hepatobiliary) contrast agent. At a time point between the time points depicted by FIGS. 5 (a) and 5 (b), a hepatobiliary contrast agent was administered intravenously as a bolus. This reaches the liver via the liver artery (A) in FIG. 5 (b). Accordingly, the liver artery is depicted with signal enhancement (arterial phase). A tumor (T), which is supplied with blood mainly via arteries, likewise stands out from the liver-cell tissue as a lighter (signal-enhanced) region. At the time point depicted in FIG. 5 (c), the hepatobiliary contrast agent reaches the liver via the veins. In FIG. 5 (d), the venous blood vessels (V) stand out from the liver tissue as light (signal-enhanced) regions (portal venous phase). At the same time, the signal intensity in the healthy liver cells, which are supplied with contrast agent mainly via the veins, continuously rises (FIG. 5 (c).fwdarw.5 (d).fwdarw.5 (e).fwdarw.5 (f)). In the hepatobiliary phase depicted in FIG. 5 (f), the liver cells (P) are depicted with signal enhancement; the blood vessels and the tumor no longer have contrast agent and are accordingly depicted darkly.

[0227] According to the disclosure, a first MRI image is generated at a first time point during the hepatobiliary phase. This can, for example, be the image shown in FIG. 5 (f).

[0228] FIG. 6 shows the same liver (L) already depicted in FIG. 5. The state shown in FIG. 6 (g) comes after the state shown in FIG. 5 (f). The liver is still depicted with signal enhancement as a consequence of the administration of the hepatobiliary contrast agent. At the time point shown in FIG. 6 (g), contrast agent is administered intravenously a second time in the form of a bolus. The phases already described in connection with FIG. 5 are passed through again: the arterial phase (FIG. 6 (h)), the portal venous phase (FIG. 6 (j)) and the late phase (FIG. 6 (k)). If the second contrast agent is likewise a hepatobiliary contrast agent, a second hepatobiliary phase is also passed through (FIG. 6 (l)), with the difference that the healthy liver cells still contain first contrast agent from the first administration and are depicted with signal enhancement over all phases. Accordingly, the contrast between blood vessels and the healthy liver cells is, especially in the images shown in FIG. 6 (i) and FIG. 6 (j), lower than in the images shown in FIG. 5 (c) and FIG. 5 (d).

[0229] To increase this contrast, MRI pictures are generated for one or more of the images shown in FIG. 6 (g), FIG. 6 (h), FIG. 6 (i), FIG. 6 (j) and FIG. 6 (k). This is depicted exemplarily in FIG. 7.

[0230] FIG. 7 shows schematically and exemplarily the generation of three MRI pictures 6 (h)′, 6 (i)′ and 6 (j)′. MRI picture 6 (h)′ is generated by subtraction of the MRI image from FIG. 5 (f) from the MRI image from FIG. 6 (h). MRI picture 6 (i)′ is generated by subtraction of the MRI image from FIG. 5 (f) from the MRI image from FIG. 6 (i). MRI picture 6 (j)′ is generated by subtraction of the MRI image from FIG. 5 (f) from the MRI image from FIG. 6 (j). The subtraction is, in each case, done for the tonal values of the individual picture elements of the MRI images. MRI picture 6 (h)′ corresponds to the MRI image shown in FIG. 5 (b); MRI picture 6 (i)′ corresponds to the MRI image shown in FIG. 5 (c); MRI picture 6 (j)′ corresponds to the MRI image shown in FIG. 5 (d).

[0231] FIG. 8 shows schematically and exemplarily, in the form of a flow chart, a preferred embodiment of the method according to the disclosure. The method (200) comprises the steps of:

[0232] (210) receiving a first MRI image of an examination object, wherein the first MRI image shows a liver or part of a liver of the examination object during a first hepatobiliary phase at a first time point after an administration of a first contrast agent,

[0233] (220) receiving a second MRI image of the same examination object, wherein the second MRI image shows the same liver or the same part of the liver during a second arterial phase at a second time point after an administration of a second contrast agent,

[0234] (230) receiving a third MRI image of the same examination object, wherein the third MRI image shows the same liver or the same part of the liver during a second portal venous phase at a third time point after the administration of the second contrast agent,

[0235] (240) receiving a fourth MRI image of the same examination object, wherein the fourth MRI image shows the same liver or the same part of the liver during a second late phase at a fourth time point after the administration of the second contrast agent,

[0236] (250) generating MRI pictures from the received MRI images, wherein a first MRI picture is calculated by subtraction of the first MRI image from the second MRI image, wherein a second MRI picture is calculated by subtraction of the first MRI image from the third MRI image, wherein a third MRI picture is calculated by subtraction of the first MRI image from the third MRI image,

[0237] (260) displaying and/or outputting one or more of the generated MRI pictures and/or storing one or more of the generated MRI pictures in a data storage medium.