Simultaneous Multi-Slice (sms) imaging has found widespread application particularly for BOLD fMRI, and DWI, as it offers high acceleration factors for sequences that are required to operate at a fixed TE. Peak RF power can be a serious impediment to the implementation of these pulses in spin-echo imaging. In this abstract we propose a method to reduce the peak power based on a quadratic phase modulation of the phase of the magnetisation in the spatial domain. In the excitation k-space the multiband RF waveform is then convolved with the FT of a chirp function. The properties of the resultant pulses are explored with respect to their peak power reduction; slice profiles, and ability to simultaneously rephase multiple slices.Hitherto the peak power has been reduced by modifying the phases of the substituent pulses; time shifting the RF pulses with respect to each other. Quadratic phase modulation in the excitation k-space is equivalent to the application of a linear frequency sweep, and can be used to reduce the peak power, but similarly to adiabatic RF pulses this results in a sequential excitation of the MB slices, which imposes additional constraints on the excitation/refocusing pulse pair. The FT of a quadratic phase function has the desirable properties that it has an approximately box-car form while of course preserving the amplitude of the MB pulse. Convolution with the MB pulse form thus offers a perspective for reducing peak power while retaining other desirable characteristics including simultaneous refocusing of all slices. The key idea is that in the spatial domain a single quadratic phase function is used of the form φ=Kz², where K is the scaling factor. As this function is superimposed across slices this implies that not all slices have identical phase profiles and are hence no longer identical in excitation k-space. If a single excitation pulse is used then of course there will be a quadratic phase modulation through the slice(s). This may be refocused by using a pulse with half the amplitude of the phase modulation, or more exotically with a quadratic shim pulse.In order to explore the pulse characteristics in the high flip angle domain SLR optimised 90 and 180 (256 points, BWTP12 and 8 respectively) pulses were used as the basis for generating MB pulses. MB factors of 3 and 5 were considered. MB pulses were generated in the standard fashion by shifting and adding the FT of the pulse forms. Quadratic phase modulation was applied using ten increments of K from zero up to a value corresponding to a phase change of π between adjacent spatial points at the maximum z-coordinate excited. This ensured that no phase aliasing occurred within the excited slices. Magnetisation trajectories were calculated using the Bloch equations. All simulations were performed in IDL (Bolder Colorado, USA).As the quadratic scaling factor increased the peak voltage fell to a plateau well before the phase-aliasing limit was reached, as is shown in figure 1, for the example of 5 slices. This means that the necessity to use half K for refocusing pulses does not lessen the power reduction, as both excitation and refocusing can be accommodated within the plateau. Hence we consider further the pulses associated with K=5. For 5 slices the reduction in peak voltage is about 70% and for 3 slices it was about 60% (data not shown). Slice profiles for 90 and 180 pulses at K=5 are shown in figure 2. The pulse form corresponding to the 90 is shown in figure 3. The pulses all rephased to have the same phase and hence would have the same TE.A quadratic phase modulation in the spatial domain could potentially be refocused by a non-linear gradient pulse. An alternative would be to have the quadratic modulation only within the slices (i.e. modulate as if all the slices were adjacent). Quadratic modulation does lead to some deterioration of the slice profile, but this is relatively minor, and could possibly be corrected by designing the pulses a priori to have a quadratic modulation. There could also be further potential in exploring other phase modulation functions. In conclusion the pulses proposed offer a reduction in peak power without further constraints on the pulse durations.