Method and magnetic resonance system for acquiring magnetic resonance data
In a method for acquiring magnetic resonance data with a magnetic resonance system using a magnetic resonance sequence, the sequence has a first partial sequence in which magnetic resonance data are acquired for multiple slices that have to be acquired simultaneously, from which image data for the individual slices are calculated by a reconstruction algorithm. The sequence also has a second partial sequence for determining additional data, which are used to evaluate and/or assess the magnetic resonance data, and which have a spatial resolution that is lower than the magnetic resonance data, in which radio-frequency pulses and readout processes take place in a slice-specific manner through a time offset within a single measuring process, in which a single continuous excitation period with the radio-frequency pulses and a single continuous readout period with the readout processes follow one another, so that separate additional data are directly determined for each slice.
1. A method for acquiring magnetic resonance data, comprising:
operating a magnetic resonance apparatus with a magnetic resonance sequence to acquire magnetic resonance data from a subject situated in the magnetic resonance apparatus;
in a first portion of said sequence, operating said magnetic resonance apparatus to simultaneously acquire magnetic resonance signals from respective multiple slices of the subject;
in a second portion of said sequence that follows said first portion, operating said magnetic resonance apparatus to acquire additional data with a spatial resolution that is lower than a spatial resolution at which said magnetic resonance data are acquired, by radiating a radio-frequency pulse and implementing a slice-specific readout of said additional data for respective slices among said multiple slices, at respective readout times that are chronologically offset with respect to each other following a single continuous excitation of nuclear spins in the subject by said radio-frequency pulses with an individual readout for each slice, thereby obtaining a separate set of additional data for each slice among said multiple slices; and
in a processor, reconstructing a magnetic resonance image of said slices in a reconstruction algorithm dependent on said additional data.
2. A method as claimed in claim 1 comprising operating said magnetic resonance apparatus in said second portion of said sequence to radiate refocussing pulses as said radio-frequency pulses.
3. A method as claimed in claim 1 comprising operating said magnetic resonance apparatus in said second portion of said sequence to activate at least one gradient pulse, preceding readout of said additional data from one of said slices among said multiple slices, that suppresses signals from slices among said multiple slices, other than said one of said slices, during said readout of said additional data from said one of said slices.
4. A method as claimed in claim 1 comprising activating said at least one gradient pulse as spoiler gradient pulse that dephases said signals of said other slices.
5. A method as claimed in claim 1 comprising acquiring said additional data as navigator data that comprises movement information of said subject in real time, and evaluating said movement information to either correct said magnetic resonance data used in said reconstruction algorithm, or to initiate a reacquisition of magnetic resonance data for at least one slice among said multiple slices, before implementing said reconstruction algorithm.
6. A method as claimed in claim 1 comprising using said additional data as reference data in said reconstruction algorithm.
7. A method as claimed in claim 1 comprising using an rs-EPI sequence modified for a blipped CAIPIRINHA technique, as said sequence.
8. A method as claimed in claim 1 comprising using a slice GRAPPA algorithm as said reconstruction algorithm.
9. A method as claimed in claim 1 comprising using an rs-EPI sequence modified for a blipped CAIPIRINHA technique as said sequence, and using a slice GRAPPA algorithm as said reconstruction algorithm.
10. A magnetic resonance apparatus comprising:
a magnetic resonance data acquisition unit;
a control unit configured to operate the magnetic resonance data acquisition unit with a magnetic resonance sequence to acquire magnetic resonance data from a subject situated in the magnetic resonance data acquisition unit;
said control unit being configured to operate said magnetic resonance data acquisition unit in a first portion of said sequence, to simultaneously acquire magnetic resonance signals from respective multiple slices of the subject;
said control unit being configured to operate said magnetic resonance data acquisition unit in a second portion of said sequence that follows said first portion, to acquire additional data with a spatial resolution that is lower than a spatial resolution at which said magnetic resonance data are acquired, by radiating a radio-frequency pulse and implementing a slice-specific readout of said additional data for respective slices among said multiple slices, at respective readout times that are chronologically offset with respect to each other following a single continuous excitation of nuclear spins in the subject by said radio-frequency pulses with an individual readout for each slice, thereby obtaining a separate set of additional data for each slice among said multiple slices; and
a processor configured to reconstruct a magnetic resonance image of said slices in a reconstruction algorithm dependent on said additional data.