Low Frequency Current Density Imaging (LF-CDI)
LF-CDI is the original implementation of CDI. The frequency range of the electrical current applied in this technique is about 2 Hz to 20 Hz (close to DC). LF-CDI measures the component of the magnetic field parallel to the B0 (large static magnetic field) axis. Subject rotation is required to obtain magnetic field data along all three orthogonal axes. A minimum of two magnetic field components are required to compute current density along a single axis [3,4].
The figure above shows the Spin Echo implementation of LF-CDI. A square current pulse is applied between the 90 and 180 degree RF pulses. An equal and opposite polarity pulse is applied following the 180 RF pulse.