Method for determining the spatial distribution of magnetic resonance signals in subvolumes of an object under examination

A method for determining a spatial distribution of magnetic resonance signals from at least one of N non-overlapping subvolumes of an object under examination in a measurement volume of a magnetic resonance apparatus, wherein N≥2, the method comprising the steps of:

• a) executing a preparation step, the preparation step comprising:
• a1) selecting a measurement sequence with encoding steps, wherein each encoding step includes irradiation of one or more spatially selective RF pulses to effect one magnetization change in each encoding step;
• a2) selecting the N subvolumes such that, taken together, those subvolumes completely cover at least one volume under examination, the volume under examination corresponding to a part of the object under examination in which nuclear spins excited during execution of the selected measurement sequence contribute to at least one of acquired MR signals;
• a3) selecting a reception encoding scheme with K reception encoding steps, wherein K≥1, the reception encoding scheme defining unique spatial encoding in at least one spatial dimension for at least one of the subvolumes, wherein that spatial encoding is not unique for an entire volume under examination in at least one spatial dimension;
• a4) defining a transmission encoding scheme with I transmission encoding steps, wherein I≥N≥2, wherein encoding is effected via an amplitude and/or phase of transverse magnetization defined spatially dependently by means of a magnetization change, wherein, for each of the I transmission encoding steps, the magnetization change is defined such that, at no position within each subvolume, a same encoding is defined as at another position within another subvolume, with excited nuclear spins contributing to an acquired magnetic resonance signal in at least one transmission encoding step and in at least two of the subvolumes;
• and
• a5) calculating a temporal amplitude and phase profile of the spatially selective RF pulses to be irradiated to effect the magnetization changes;
• b) carrying out an execution step for all encoding steps, each reception encoding step that is defined according to the reception encoding scheme being executed I times with variations according to the I transmission encoding steps of the transmission encoding scheme, wherein, in each encoding step, all RF pulses calculated for each transmission encoding step of the transmission encoding scheme are applied by means of at least one transmission element and, without overlapping in time with those RF pulses, a spatial encoding is effected according to a reception encoding scheme, with magnetic resonance signals being acquired by means of at least one reception element;
• c) executing a reconstruction step based on the transmission encoding scheme, wherein components of the acquired magnetic resonance signals are assigned to the N subvolumes and, for at least one of the subvolumes spatially encoded according to the reception encoding scheme, one or more spatial distributions of the magnetic resonance signals is reconstructed from the acquired magnetic resonance signals and/or variables derived therefrom are calculated, wherein this or these subvolumes are designated mapping volumes;
• and
• d) executing a result step in which results of the reconstruction step are stored and/or displayed.