Patent ID: 6054858
Filing Date: 2000-04-25
Classification: G01R

Abstract:
In a magnetic resonance imaging apparatus having a primary coil for generating a primary magnetic field in a first direction, an auxiliary coil for generating an auxiliary magnetic field in a direction parallel to the primary magnetic field and resulting in a net magnetic field in a first direction and an rf coil for transmitting and receiving an rf signal that generates an imaging signal in a direction substantially perpendicular to the direction of the net magnetic field, a method for tuning the apparatus to the resonant frequency of the rf coil comprising the steps of:placing a sample within the primary coil, auxiliary coil and rf coil of the magnetic resonance imaging apparatus and causing the nuclear spins of the sample to resonate at a Larmor frequency proportional to the net magnetic field;applying radio frequency signals of one or more frequencies to the rf coil;monitoring the transfer of energy into the rf coil in response to the applied radio frequency signals;identifying the frequency at which energy transfer into the rf coil is maximized;varying the magnitude of the current applied to the auxiliary coil to change the net magnetic field so that the Larmor frequency of the sample is substantially the same as the identified frequency at which energy transfer into the rf coil is maximized.