Gradient pulses are generated by current conducting gradient coils.
High-frequency components cause the center of gravity of the current to
be shifted by mutual influencing of the coil conductors. The shift
depends on the electrical resistance of the conductor material, which in
turn depends on the temperature of said conductor material, and on the
frequency (, such that the magnetic gradient field B decreases with
increasing frequency. This phenomenon manifests itself as a delay (of the
gradient pulse with respect to the gradient demand D. The invention
proposes to determine during the pulse a quantity representing the
conducting state of the conductors of the gradient system and to use a
model of the MRI apparatus to calculate the gradient delay (from that
quantity and to correct the gradient demand for said delay.
