Method and magnetic resonance system for fat saturation

1. A method for acquiring MR data, comprising:

from a control computer, operating an MR scanner, comprising a radio frequency (RF) coil arrangement and a gradient coil system, while an examination subject is situated in the MR scanner, to acquire an initial set of MR data comprising a fat signal from the examination subject;

in said control computer, automatically determining a flip angle as a function of a predetermined requirement for said fat signal;

from said control computer, operating the MR scanner to radiate an RF preparation pulse, having said flip angle, from said RF coil arrangement;

from said control computer, operating said MR scanner to radiate a Spectrally Adiabatic Inversion Recovery (SPAIR) pulse from said RF coil arrangement, after radiating said RF preparation pulse having said flip angle;

from said control computer, operating said RF coil arrangement and said gradient coil system of said MR scanner to acquire another set of MR data, again comprising said fat signal, from said examination subject, and, from said control computer, entering the acquired MR data into an electronic memory; and

via said control computer, making the MR data stored in said electronic memory available in electronic form as a data file.

2. A method as claimed in claim 1 comprising determining said flip angle by:

from said control computer, operating said MR scanner to acquire said initial set of MR data with respective fat signals for respectively different flip angles;

in said control computer, determining a flip angle fat signal relationship between said fat signals and said different flip angles; and

in said control computer, determining said flip angle as a flip angle that thus satisfies said predetermined requirement according to said flip angle fat signal relationship.

3. A method as claimed in claim 2 comprising using, in said control computer, maximum fat saturation as said predetermined requirement, and determining said flip angle as the flip angle that results in the smallest fat signal in accordance with said relationship.

4. A method as claimed in claim 1 comprising, from said control computer, operating said RF coil arrangement and said gradient coil system of said MR scanner to acquire said initial set of MR data from a plurality of slices of the examination subject and, before the MR data for each slice in said initial set of MR data are acquired, radiating a respective SPAIR pulse from said RF coil arrangement.

5. A method as claimed in claim 4 comprising, from said control computer, operating said MR scanner to radiate said RF preparation pulse from said RF coil arrangement before the MR data for each slice in said initial set of MR data are acquired and, in said control computer, setting said flip angle for a first of said plurality of slices to a flip angle value that results in a minimum fat signal in said MR data in said first slice in said initial set of MR data, and setting said flip angle for every other slice in said plurality of slices to the same flip angle value as said flip angle value for said first slice.

6. A method as claimed in claim 4 comprising, from said control computer, operating said MR scanner to radiate said RF preparation pulse from said RF coil arrangement before acquiring said MR data for a first slice in said plurality of slices in said initial set of MR data and, in said control computer, using, as said predetermined requirement, a requirement for uniform fat saturation over said plurality of slices.

7. A method as claimed in claim 6 comprising, in said control computer, measuring said fat signal in the MR data for at least one slice, among said plurality of slices, after said first slice in said initial set of MR data, and giving said flip angle a flip angle value that causes the fat signal of the MR data of the first slice in said initial set of MR data to correspond to said fat signal measured for said at least one other slice.

8. A method as claimed in claim 6 comprising, in said control computer, measuring the fat signal in MR data from at least one slice, among said plurality of slices, after said first slice in said initial set of MR data, for respectively different repetition times of acquisition of said MR data, and determining a repetition time fat signal relationship from the fat signal for said different repetition times, determining the fat signal of said at least one slice as a function of a predetermined repetition time, and giving said flip angle a flip angle value that causes said fat signal in said first slice to produce the fat signal determined for said predetermined repetition time.

9. A method as claimed in claim 8 comprising determining said repetition time fat signal relationship by determining a minimum repetition time and a maximum repetition time, among said different repetition times, wherein said fat signal increases monotonically with the repetition time in a repetition time range between said minimum and maximum repetition times, and determining said flip angle to have a flip angle value a by measuring said fat signal for a plurality of different flip angles in said initial set of MR data, determining a minimum flip angle and a maximum flip angle, wherein the fat signal decreases monotonically with the flip angle in a flip angle range between the minimum and maximum flip angles, and determining α according to

α

=

-

α

ma

⁢

⁢

x

-

α

m

⁢

⁢

i

⁢

⁢

n

TR

m

⁢

⁢

a

⁢

⁢

x

-

TR

m

⁢

⁢

i

⁢

⁢

n

×

(

TR

-

TR

m

⁢

⁢

i

⁢

⁢

n

)

+

α

ma

⁢

⁢

x

.

wherein TR is the repetition time, TR min is the minimum repetition time, TR max is the maximum repetition time, α max is the maximum flip angle, and α min is the minimum flip angle.

10. A magnetic resonance (MR) apparatus comprising:

an MR scanner comprising a radio frequency (RF) coil arrangement and a gradient coil system;

a control computer configured to operate the MR scanner, while an examination subject is situated in the MR scanner, to acquire an initial set of MR data comprising a fat signal from the examination subject;

said control computer being configured to automatically determine a flip angle as a function of a predetermined requirement for said fat signal;

said control computer being configured to operate the MR scanner to radiate an RF preparation pulse, having said flip angle, from said RF coil arrangement;

said control computer being configured to operate said MR scanner to radiate a Spectrally Adiabatic Inversion Recovery (SPAIR) pulse from said RF coil arrangement, after radiating said RF preparation pulse having said flip angle;

an electronic memory;

said control computer being configured to operate said RF coil arrangement and said gradient coil system of said MR scanner to acquire another set of MR data, again comprising said fat signal, from said examination subject, and to enter the acquired MR data into said electronic memory; and

said control computer being configured to make the MR data stored in said electronic memory available in electronic form as a data file.

11. A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a control computer of a magnetic resonance (MR) apparatus, that comprises an MR scanner comprising a radio frequency (RF) coil arrangement and a gradient coil system, said programming instructions causing said control computer to:

operate the MR scanner, while an examination subject is situated in the MR scanner, to acquire an initial set of MR data comprising a fat signal from the examination subject;

automatically determine a flip angle as a function of a predetermined requirement for said fat signal;

operate the MR scanner to radiate an RF preparation pulse, having said flip angle, from said RF coil arrangement;

operate said MR scanner to radiate a Spectrally Adiabatic Inversion Recovery (SPAIR) pulse from said RF coil arrangement, after radiating said RF preparation pulse having said flip angle;

operate said RF coil arrangement and said gradient coil system of said MR scanner to acquire another set of MR data, again comprising said fat signal, from said examination subject, and enter the acquired MR data into an electronic memory; and

make the MR data stored in said electronic memory available in electronic form as a data file.