A method, carried out by a computer or a control unit for a magnetic resonance imaging system, for subject-specific optimisation of a multiband RF pulse for exciting spins within a field-of-view to obtain a target magnetisation in a magnetic resonance imaging examination of a subject, wherein the RF pulse is a spokes RF pulse comprising a train of sub-pulses, called spokes, interleaved with gradient blips, wherein the gradient blips determine the trajectory of a magnetisation in transmit k-space so that each sub-pulse is played at a specific position in transmit k-space, and wherein each sub-pulse is to excite a pre-determined number of slices simultaneously, the method comprising the steps of a1. Receiving a subject-specific B1+-field map of the field-of-view, a2. Receiving a starting k-space position and using that as the current k-space position, b. For each of the slices to be excited by the RF pulse, performing the following steps (i) to (iii): i. calculating a sub-pulse based on the current k-space position, taking into account the B1+-field map, and calculating the expected magnetization after that sub-pulse; ii. calculating the inverse Fourier transform of the difference between the expected magnetization and the target magnetisation; iii. determining an optimal k-space position for the next spoke for this slice to be at the position where the absolute value of the inverse Fourier transform has a maximum; c. determining the next k-space position for all slices together based on the optimal k-space positions determined for each slice individually; e. calculating (40, 42) the multi-band RF pulse based on the k-space positions determined in step c. wherein the RF pulse is a spokes RF pulse comprising a train of sub-pulses, called spokes, interleaved with gradient blips, wherein the gradient blips determine the trajectory of a magnetisation in transmit k-space so that each sub-pulse is played at a specific position in transmit k-space, and wherein each sub-pulse is to excite a pre-determined number of slices simultaneously, the method comprising the steps of a1. Receiving a subject-specific B1+-field map of the field-of-view, a2. Receiving a starting k-space position and using that as the current k-space position, b. For each of the slices to be excited by the RF pulse, performing the following steps (i) to (iii): i. calculating a sub-pulse based on the current k-space position, taking into account the B1+-field map, and calculating the expected magnetization after that sub-pulse; ii. calculating the inverse Fourier transform of the difference between the expected magnetization and the target magnetisation; iii. determining an optimal k-space position for the next spoke for this slice to be at the position where the absolute value of the inverse Fourier transform has a maximum; i. calculating a sub-pulse based on the current k-space position, taking into account the B1+-field map, and calculating the expected magnetization after that sub-pulse; ii. calculating the inverse Fourier transform of the difference between the expected magnetization and the target magnetisation; iii. determining an optimal k-space position for the next spoke for this slice to be at the position where the absolute value of the inverse Fourier transform has a maximum; c. determining the next k-space position for all slices together based on the optimal k-space positions determined for each slice individually; e. calculating (40, 42) the multi-band RF pulse based on the k-space positions determined in step c.