Cloverleaf coil experiment.

<p>a) Bottom and side X-ray images of the cloverleaf coil used in the experiment. The coils are coupled diagonally to form two figure of eight coils and each figure eight coil is connected to an independent power source. b) Neuro navigation software display. The position of the coil is tracked using the navigator and indicated by the central red dot and the yellow circle over an MRI scan of the brain of the subject. The coil shape is added offline to illustrate the actual position. The yellow sphere at the front is the nasion, the red sphere at the bottom left the left tragus, used in registering MRI and head position. The color scale indicates tentative field strength, calculated in real time assuming a spherical head model and a figure of eight coil. c) Electric field induced in a pickup coil positioned on 2 neighboring wings of the clover leaf coil. The coils were driven separately by 2 Magstim rapid² stimulators. d) A reconstruction of the effective electric field amplitude and direction during a rfTMS pulse of the clover leaf coil with the field of coil #1 directed along the x-axis and the field of coil #2 along the y-axis.