Method for determining distortion-reduced magnetic resonance data and magnetic resonance system

1. A method for determining distortion-reduced magnetic resonance (MR) data for at least one layer of an object to be examined in a subarea of an MR system, the subarea being located along a radial direction of the MR system at an edge of a field of view of the MR system, the method comprising:

positioning the object to be examined at a first position along an axial direction of the MR system;

acquiring first MR data in the subarea for the at least one layer at the first position;

positioning the object to be examined at a second position along the axial direction of the MR system, the second position being different from the first position;

acquiring second MR data in the subarea for the at least one layer at the second position; and

determining the distortion-reduced MR data for the at least one layer based on the acquired first and second MR data.

2. The method of claim 1 , wherein at least one of:

a sign of inhomogeneities in a basic magnetic field at the first position and at the second position is different, and

a sign of non-linearities of gradient fields at at the first position and at the second position is different.

3. The method of claim 1 , wherein at least one of

an amount of inhomogeneities in a basic magnetic field is equal within a tolerance range at the first position and at second position; and

an amount of non-linearities of gradient fields is equal within a tolerance range at the first position and at second position.

4. The method of claim 2 , further comprising:

providing data which describes at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields within the subarea as a function of the position along the axial direction; and

determining the first position and the second position based on the provided data.

5. The method of claim 1 ,

wherein distortion behavior of the first MR data is substantially cancelled out by distortion behavior of the second MR data.

6. The method of claim 4 ,

wherein, at the first position and the second position, first and second MR data are respectively acquired for a number of layers with different spatially-encoding gradient fields.

7. The method of claim 6 , further comprising:

determining the number of layers based on a comparison of the provided data with a tolerance range of at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields for each layer of the respective number of layers.

8. The method of claim 1 , wherein determining the distortion-reduced MR data includes a weighted averaging of the first and second MR data.

9. A magnetic resonance system comprising:

a scanning controller, configured to determine distortion-reduced MR data for at least one layer of an object to be examined in a subarea of an MR system, the subarea being located along a radial direction of the MR system at an edge of a field of view of the MR system, the scanning controller being further configured to

position the object to be examined at a first position along an axial direction of the MR system,

acquire first MR data in the subarea for the at least one layer at the first position,

position the object to be examined at a second position along the axial direction of the MR system, the second position being different from the first position,

acquire second MR data in the subarea for the at least one layer at the second position, and

determine the distortion-reduced MR data for the at least one layer based on the first and second MR data.

10. The magnetic resonance system of claim 9 ,

wherein distortion behavior of the first MR data is substantially cancelled out by distortion behavior of the second MR data.

11. The method of claim 2 , wherein at least one of

and amount of inhomogeneities in a basic magnetic field is equal within a tolerance range at the first position and at the second position; and

an amount of non-linearities of gradient fields is equal within a tolerance range at the first position and at second position.

12. The method of claim 3 , further comprising:

providing data which describes at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields within the subarea as a function of the position along the axial direction;

determining the first position and the second position based on the provided data.

13. The method of claim 11 , further comprising:

providing data which describes at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields within the subarea as a function of the position along the axial direction; and

determining the first position and the second position based on the provided data.

14. The method of claim 1 ,

wherein, at the first position and the second position, first and second MR data are respectively acquired for a number of layers with different spatially-encoding gradient fields.

15. The method of claim 12 ,

wherein, at the first position and the second position, first and second MR data are respectively acquired for a number of layers with different spatially-encoding gradient fields.

16. The method of claim 15 , further comprising:

determining the number of layers based on a comparison of the provided data with a tolerance range of at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields for each layer of the respective number of layers.

17. The method of claim 13 ,

wherein, at the first position and the second position, first and second MR data are respectively acquired for a number of layers with different spatially-encoding gradient fields.

18. The method of claim 17 , further comprising:

determining the number of layers based on a comparison of the provided data with a tolerance range of at least one of the inhomogeneities in the basic magnetic field and the non-linearities of gradient fields for each layer of the respective number of layers.