Slice-specific phase correction in slice multiplexing

A magnetic resonance (MR) apparatus that corrects a signal phase in a slice multiplexing data acquisition of MR signals from a subject, said apparatus comprising:

• an MR data acquisition scanner;
• a processor;
• said processor being configured to operate said MR data acquisition scanner so as to execute a slice multiplexing data acquisition sequence wherein, for each of at least two slices of the object, MR signals are acquired in said slice multiplexing data acquisition sequence by said at least two slices being respectively excited by radiating two radio-frequency (RF) pulses, each having a resonance frequency and the resonance frequencies differing from each other, in order to produce a different magnetization respectively in each of said at least two slices, while a slice selection gradient is activated, for a slice selection duration in a slice selection direction;
• said processor being configured to calculate a linear phase error along the slice selection direction, said linear phase error arising from slice-specific linear field deviations that occur along the slice selection direction due to magnetic fields other than said slice selection gradient that act on said at least two slices in the slice selection direction;
• additionally in said processor, for each of said two RF pulses, also calculating a time offset, relative to a middle of said slice selection duration, with an offset amount that corrects said calculated linear phase error when a combination of said two RF pulses is radiated at the calculated time offsets, with said combination of said two RF pulses modifying a gradient moment that acts on said different magnetizations occurring in said at least two slices during said slice selection duration;
• said processor being further configured to operate said MR data acquisition scanner in order to execute said slice multiplexing data acquisition sequence, including radiating said two RF pulses respectively at times corresponding to the respective, calculated time offsets, while activating said slice selection gradient in said slice selection direction and with a partial temporal overlap of RF pulses said two that are radiated, so as to acquire said MR signals with said linear phase correction produced by said gradient moment, without altering or augmenting said activated slice selection gradient;
• and
• said processor being configured to make the acquired MR signals available from the processor in electronic form, as a data file.