When a multi shot technique is applied, each shot will have its own effect on the prepulse, with a scan time increase. Multiple shots allow a shorter IR delay but at the cost of increased scan time.
In multi shot technique (also called mosaic imaging), a group of samples, which are contiguous in k space are acquired in the same sequence repetition. The phase encoding steps or profiles are split into 'shots' (sub-acquisitions). The shot interval is the time between the shots. Usually kept as short as possible. Because the acquisitions are divided into different shots, each shot will have less T1 variation, thereby increasing T1 contrast. Two excitations, each requiring the data for one half of k-space, are the simplest variation of multi shot techniques (e.g. positive versus negative phase encoding). The alternative to this mosaic strategy for multi shot EPI is interleaving. In interleaved sequences, each repetition acquires every nth (n is the number of shots) line in k-space and for the complete raw data set the various repetition data are interlaced.

See also Single Shot Technique.