Method to generate magnetic resonance measurement data with image contrast selected and produced by preparation pulses
View Patent ↗In a method and magnetic resonance apparatus to generate magnetic resonance measurement data, k-space corresponding to the examination region is subdivided into a first region and a second region. The first region includes the k-space center, and a ratio of preparation pulses radiated by the radio-frequency antenna of the magnetic resonance apparatus to RF excitation pulses radiated by the radio-frequency antenna is greater in the first region than in a second region of k-space corresponding to the examination region that is not covered by the first region of k-space. Preparation pulses in the entirety of k-space corresponding to the examination region are therefore not radiated uniformly often, but instead a reduced number of preparation pulses is applied in the second region in comparison to the first region. The total measurement time to generate magnetic resonance data, as well as a SAR exposure, are reduced.
1. A method to generate magnetic resonance (MR) data of an examination region of an examination subject, comprising:
operating an MR data acquisition unit having a measurement volume in which the examination region of the examination subject is located, to generate echo signals originating from said examination region by radiating a plurality of radio-frequency (RF) excitation pulses successively with an RF antenna of said MR data acquisition unit, and generating respectively different magnetic field gradients with a gradient coil system of said MR data acquisition unit to spatially encode said echo signals until data entries corresponding to said examination region have been entered into k-space in a memory, and radiating preparation pulses into the examination region of the examination subject with said RF antenna with a ratio of said preparation pulses to said RF excitation pulses being larger in a first region of k-space corresponding to said examination region and that comprises at least a center of k-space, than a second region of k-space corresponding to said examination region, said second region not being covered by said first region and wherein said first region is a region surrounding said k-space center with a radius depending on a time t 1 that follows after a radiated RF excitation pulse up to acquisition of a following echo signal;
acquiring said echo signals with an RF reception antenna after each radiated RF excitation pulse; and
making said entries in k-space available from said memory as a measurement data file.
2. The method as claimed in claim 1 comprising selecting pulses for radiation as said preparation pulses from the group consisting of T 1 preparation pulses, T 2 preparation pulses, and preparation pulses configured to suppress unwanted signals.
3. The method as claimed in claim 1 comprising radiating no preparation pulses in said second region.
4. The method as claimed in claim 1 comprising selecting said ratio to be at least twice as large in said first region as in said second region.
5. The method as claimed in claim 1 comprising radiating said preparation pulses with a uniform distribution in said first region and in said second region.
6. The method as claimed in claim 1 wherein said first region comprises lines of k-space with a predetermined maximum distance from said center of k-space.
7. A magnetic resonance (MR) apparatus to generate MR data of an examination region of an examination subject, comprising:
an MR data acquisition unit having a measurement volume in which the examination region of the examination subject is located;
a control unit configured to operate said MR data acquisition unit to generate echo signals originating from said examination region by radiating a plurality of radio-frequency (RF) excitation pulses successively with an RF antenna of said MR data acquisition unit, and generating respectively different magnetic field gradients with a gradient coil system of said MR data acquisition unit to spatially encode said echo signals until data entries corresponding to said examination region have been entered into k-space in a memory, and radiating preparation pulses into the examination region of the examination subject with said RF antenna with a ratio of said preparation pulses to said RF excitation pulses being larger in a first region of k-space corresponding to said examination region and that comprises at least a center of k-space, than a second region of k-space corresponding to said examination region, said second region not being covered by said first region and wherein said first region is a region surrounding said k-space center with a radius depending on a time t 1 that follows after a radiated RF excitation pulse up to acquisition of a following echo signal;
acquire said echo signals with an RF reception antenna after each radiated RF excitation pulse; and
said control unit being configured to operate said MR data acquisition unit to make said entries in k-space available from said memory as a measurement data file.
8. 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 (MR) apparatus comprising an MR data acquisition unit, said programming instructions causing said computerized control and evaluation unit to operate said MR apparatus to:
operate the MR data acquisition unit, with an examination region of an examination subject is located in a measurement volume thereof, to generate echo signals originating from said examination region by radiating a plurality of radio-frequency (RF) excitation pulses successively with an RF antenna of said MR data acquisition unit, and generating respectively different magnetic field gradients with a gradient coil system of said MR data acquisition unit to spatially encode said echo signals until data entries corresponding to said examination region have been entered into k-space in a memory, and radiating preparation pulses into the examination region of the examination subject with said RF antenna with a ratio of said preparation pulses to said RF excitation pulses being larger in a first region of k-space corresponding to said examination region and that comprises at least a center of k-space, than a second region of k-space corresponding to said examination region, said second region not being covered by said first region and wherein said first region is a region surrounding said k-space center with a radius depending on a time t 1 that follows after a radiated RF excitation pulse up to acquisition of a following echo signal;
acquire said echo signals with an RF reception antenna after each radiated RF excitation pulse; and
make said entries in k-space available from said memory as a measurement data file.
9. A method as claimed in claim 1 wherein said time t 1 is at least as long as a hardware-dependent minimum switching time between a transmission mode and a reception mode of said RF antenna.
10. A method as claimed in claim 7 wherein said time t 1 is at least as long as a hardware-dependent minimum switching time between a transmission mode and a reception mode of said RF antenna.
11. A method as claimed in claim 8 wherein said time t 1 is at least as long as a hardware-dependent minimum switching time between a transmission mode and a reception mode of said RF antenna.