Despite these theoretical advantages, POMP and other simultaneous multi-slice excitation schemes are hampered because noise and phase-encoding artifacts (e.g., flow, wrap-around) may be propagated from one image to the other. Furthermore, because they cannot be used in conjunction with a no-phase-wrap option, they can only be applied in situations when the imaged object does not exceed the FOV in the phase-encode direction.
Advanced Discussion (show/hide)»
The POMP technique is the oldest of a class of techniques that utilize time-multiplexing to acquire MR signals simultaneously from two or more slices. The classic POMP method, described in the Q&A above, is an example of simultaneous echo/image refocusing.
A second different approach combines slice excitation at different off-resonance frequencies with demultiplexing based on spatial sensitivity differences of RF receiver coils. This method is known as Multi-Band (MB) excitation. The MB method allows 3 or more slices to be simultaneously excited, increasing imaging efficiency.
The MR signals from MB slices are unfolded by using spatial sensitivity information in each RF channel similar to techniques employed in parallel imaging. As each receiver coil records a combination of MR signals from all excited slices weighted by sensitivities of that specific coil. A matrix inversion procedure can thus decode locations and reconstruct images of the respective slices.
The simultaneous image refocusing and MB methods are not mutually exclusive, and can be combined for improved results. See paper by Feinberg et al below.
Feinberg DA, Moeller S, Smith SM et al. Multiplexed echo planar imaging for sub-second whole brain FMRI and fast diffusion imaging. PLoS ONE 2010; 5(12):e15710.
Glover GH. Phase-offset multiplanar (POMP) volume imaging: a new technique. J Magn Reson Imaging 1991; 1:457-461.
Larkman DJ, Hajnal JV, Herlihy AH, et al. Use of multicoil arrays for separation of signal from multiple slices simultaneously excited. J Magn Reson Imaging 2001; 13:313–317.
Lee KJ, Wild JM, Griffiths PD, Paley MNJ. Simultaneous multislice imaging with slice multiplexed RF pulses. Mag Reson Med 2005; 54:755–760.
Souza SP, Szumowski J, Dumoulin CL, et al. SIMA: simultaneous multislice acquisition of MR images by Hadamard-encoded excitation. J Comput Assist Tomogr 1988; 12:1026–1030.
Weaver JB. Simultaneous multislice acquisition of MR images. Magn Res Med 1988; 8:275–284.
How does frequency-encoding let you stimulate a given slice?