Patent ID: 7606611

Claim:
A medical apparatus, for use with a magnetic resonance imaging system that generates a magnetic resonance image from magnetic resonance signals in an imaging volume, said medical apparatus comprising: a medical instrument configured for introduction into said imaging volume, said medical instrument having a longitudinal axis and said medical instrument being non-rotationally symmetric around said longitudinal axis; an acquisition unit attached in a fixed physical relation to said medical instrument, said acquisition unit having a reception sensitivity profile for said magnetic resonance signals that is non-constant in a plane substantially perpendicular to said longitudinal axis, and said acquisition unit receiving said magnetic resonance signals in said imaging volume and generating an output signal therefrom; and an evaluation unit in communication with said acquisition unit and supplied with said output signal from said acquisition unit, said evaluation unit being configured to electronically determine from the magnetic resonance signal received by said acquisition unit, a rotational orientation of said medical instrument in said plane, around said longitudinal axis, by identifying said rotational orientation due to said sensitivity profile being non-constant in said plane.