Figure 2.

Example of concurrent TMS-fMRI protocols. There are three possible ways to apply TMS pulses during fMRI simultaneously. (A) A method enabling TMS to interfere with EPI slices. Perturbed EPI slices (indicated by an orange cross) are sacrificed and replaced by slice interpolation, typically from the volumes before and after the volume of interest (indicated by orange EPI slices). Advantages: High flexibility to stimulate at any time regardless of EPI timing. Disadvantages: It requires a high level of post-processing capabilities to detect the damaged EPI slices and replace them. (B) A method to insert a gap time between EPI slices and apply TMS pulses meanwhile. Advantages: No EPI slices are sacrificed. Disadvantages: The number of stimulations is limited as it needs to fit in the gap time. Hence, the whole TMS-fMRI protocol tends to be longer. (C) A method to interleave TMS pulses with EPI slices. Advantages: It allows for continuous stimulation which is often used as a therapeutic protocol. Disadvantages: Reliable hardware and software are essential as the pulses must be controlled precisely.