Patent ID: 8374678

Claim:
A medical apparatus comprising: a C-arm x-ray apparatus comprising a plurality of components configured to operate to acquire an image of a region of a body of a patient located in an acquisition region of the C-arm x-ray apparatus, said plurality of components including a C-arm that is movable through a plurality of different positions and that exhibits a predictable mechanical deformation in at least one of said positions; at least one position determination device configured to determine a position of a medical instrument adapted to interact with the body of the patient in an interaction region located within said acquisition region, said at least one position determination device being fixedly attached to a component among said plurality of components of said C-arm x-ray apparatus, the fixed attachment of said at least one position determination device to said component producing a known relationship between position coordinates of said C-arm x-ray apparatus in a defined coordinate system and position coordinates of said at least one position determination device in said defined coordinate system; a measurement device that identifies when said C-arm is in said at least one of said positions by emitting a measurement device signal; and a computer supplied with said measurement device signal and with an image of said region of the body of the subject acquired by said C-arm x-ray apparatus, said computer comprising a display screen and being configured to mix an image of said instrument into said image of said region of the body of said patient in a positionally accurate mixing at said display screen, using said position of said instrument obtained by said at least one position determination device, and said computer being configured to update said known relationship between the position coordinates of said C-arm x-ray apparatus and the position coordinates of said at least one position determination device, dependent on said measurement device signal, to update said known relationship, when said C-arm is in said at least one of said positions, dependent on said predicted mechanical deformation, to obtain an updated relationship, and to use said updated relationship to maintain said positionally accurate mixing despite said C-arm exhibiting said predictable deformation in said at least one of said positions.