Patent ID: 7279894

Claim:
A magnetic resonance tomography apparatus comprising: a basic field magnet which generates a basic magnetic field in a basic magnetic field direction; gradient coils which superimpose at least one gradient magnetic field on said basic magnetic field transversely to a coding direction that coincides with said basic magnetic field direction, to produce an overall magnetic field in said coding direction having a magnetic field strength with a component changing quadratically over distance; a support mechanism adapted to receive an examination subject thereon, for displacing said subject by a distance Δw in said coding direction in said overall magnetic field; a radio frequency system for exciting nuclear spins in said examination subject and for receiving magnetic resonance signals arising from said spins, each of said magnetic resonance signals having a phase and a resonant frequency; and a control computer supplied with said magnetic resonance signals that determines a quadratic change in at least one of differences in said phase and differences in said resonant frequency which occur due to said overall magnetic field component changing quadratically over distance during the displacement of said subject by said distance Δw, and that determines, from said quadratic change, an absolute location L of a magnetic resonance signal in said coding direction.