Magnetic resonance apparatus and operating method

1. A method to operate a magnetic resonance apparatus comprising:

acquiring magnetic resonance data by operating a magnetic resonance data acquisition unit according to data acquisition pulse sequence in which a radio-frequency excitation pulse, which excites nuclear spins in a subject, is radiated when a full strength of at least two activated phase coding gradients in said pulse sequence is reached;

entering magnetic resonance signals resulting from excitation of said nuclear spins into an electronic memory organized as k-space, by scanning k-space in a first region thereof that does not include a center of k-space, and scanning k-space in a Cartesian manner in a second region of k-space that remains without the first region;

providing sequence parameters for said data acquisition pulse sequence to a processor that describe a number of acquisitions of said first and second regions of k-space and a repetition time of said number of acquisitions;

in said processor, automatically determining, from said sequence parameters, a gradient field strength of said at least two phase coding gradients that corresponds to a shortest total acquisition time for executing said data acquisition pulse sequence; and

making a designation of said gradient strength available at an output of said processor in an electronic form.

2. A method as claimed in claim 1 comprising operating said magnetic resonance data acquisition unit with a PETRA sequence, as said pulse sequence.

3. A method as claimed in claim 1 wherein scanning k-space in a Cartesian manner comprises implementing single point imaging in said second region of k-space.

4. A method as claimed in claim 1 comprising, at a display unit in communication with said processor, visually displaying a representation of said gradient field strength.

5. A method as claimed in claim 4 comprising, via a user interface in communication with said processor, allowing manual entry of a command that selectively activates or deactivates said display of said representation of said calculated gradient field strength.

6. A method as claimed in claim 1 comprising, from said processor, automatically controlling operation of said data acquisition unit according to said pulse sequence, with said calculated gradient field strength.

7. A method as claimed in claim 1 comprising selecting said sequence parameters from the group consisting of parameters describing an image resolution, parameters describing a size of a field of view, parameters describing a size of a matrix in k-space in which said data points are entered, parameters describing an echo time of said pulse sequence, parameters describing a number of radial spokes in said first region of k-space, and parameters describing a time within said pulse sequence for ramping said phase coding gradients.

8. A method as claimed in claim 1 comprising calculating said gradient field strength by calculating a minimum of:

T acq =( N rad +256/3*π*(γ* TE*G *FOV) 3 )*( TE+T ramp +N /(2γ*FOV* G ))

for the total acquisition time, wherein N rad is the number of radial spokes to be acquired in k-space, TE is the echo time, G is the gradient strength, FOV is the size of the field of view, T ramp is the time provided for the ramping of the phase coding gradients, γ is the gyromagnetic ratio of said nuclear spins, and N is the matrix size in k-space; or via use of predetermined values for the gradient strength in the formula for the total acquisition time and selection of the value leading to the lowest total acquisition time.

9. A magnetic resonance apparatus comprising:

a magnetic resonance data acquisition unit:

a control unit configured to operate the magnetic resonance data acquisition unit to acquire magnetic resonance data according to data acquisition pulse sequence in which a radio-frequency excitation pulse, which excites nuclear spins in a subject, is radiated when a full strength of at least two activated phase coding gradients in said pulse sequence is reached;

said control unit configured to enter magnetic resonance signals resulting from excitation of said nuclear spins into an electronic memory organized as k-space, by scanning k-space in a first region thereof that does not include a center of k-space, and scanning k-space in a Cartesian manner in a second region of k-space that remains without the first region;

a processor configured to receive sequence parameters for said data acquisition pulse sequence that describe a number of acquisitions of said first and second regions of k-space and a repetition time of said number of acquisitions;

said processor being configured to automatically determine, from said sequence parameters, a gradient field strength of said at least two phase coding gradients that corresponds to a shortest total acquisition time for executing said data acquisition pulse sequence; and

said processor being configured to make a designation of said gradient strength available at an output of said processor in an electronic form.

10. A non-transitory, computer-readable data storage medium encoded with programming instructions, said data storage medium being loaded into a computerized control and evaluation system of a magnetic resonance apparatus, that also comprises a magnetic resonance data acquisition unit, said programming instructions causing said computerized control and evaluation system to:

operate the magnetic resonance data acquisition unit to acquire magnetic resonance data according to data acquisition pulse sequence in which a radio-frequency excitation pulse, which excites nuclear spins in a subject, is radiated when a full strength of at least two activated phase coding gradients in said pulse sequence is reached;

enter magnetic resonance signals resulting from excitation of said nuclear spins into an electronic memory organized as k-space, by scanning k-space in a first region thereof that does not include a center of k-space, and scanning k-space in a Cartesian manner in a second region of k-space that remains without the first region;

receive sequence parameters for said data acquisition pulse sequence that describe a number of acquisitions of said first and second regions of k-space and a repetition time of said number of acquisitions;

automatically determine, from said sequence parameters, a gradient field strength of said at least two phase coding gradients that corresponds to a shortest total acquisition time for executing said data acquisition pulse sequence; and

make a designation of said gradient strength available at an output of said control and evaluation system in an electronic form.