Patent ID: 7543986

Claim:
An x-ray C-arm apparatus comprising: a C-arm exhibiting a C-arm plane; a plurality of components mounted on said C-arm, including an x-ray source and a radiation detector; a C-arm mount to which said C-arm is mounted for rotation around an orbital axis, said C-arm and said plurality of components mounted thereon having an overall center of gravity, and said plurality of components mounted on said C-arm, in combination exerting a first torque on said C-arm totaling all respective torques produced by said plurality of components; and a compensation device located on said C-arm entirely between said x-ray source and said radiation detector, said compensation device comprising a counterweight mounted on a rotatable arm that spaces said counterweight from said C-arm, and a gear arrangement that interacts with said C-arm upon rotation of said C-arm to rotate said rotatable arm and said counterweight, dependent on rotation of said C-arm to produce a second torque that at least partially compensates said first torque.