| 摘要 |
A jig for positioning an instrument, for example a biopsy needle, includes a stop (7) for defining the position of a free end (3) of the instrument in a first coordinate direction (Z) of a three-dimensional system of coordinates, and an adjusting mechanism (15, 17) for adjusting the position of the instrument in second (X) and third (Y) coordinate directions of the system of coordinates. The adjusting mechanism is accommodated in a housing (23) in which furthermore a phantom (5) is rigidly mounted. The adjusting mechanism includes a first and a second circular disc (15, 17), having a first and a second central axis (19, 21), respectively, each central axis extending perpendicularly to the plane of the relevant disc and through its center (16, 18). The first disc (15) is journalled in the housing (23) so as to be rotatable about the first central axis (19) and is provided with an eccentrically situated circular opening (27) whose diameter is substantially equal to the diameter of the second disc (17). The second disc (17) is journalled in said opening (27) so as to be rotatable about the second central axis (21). The first and second central axes (19, 21) extend parallel to the first coordinate direction (Z) and the first central axis intersects the plane of the second disc (17) at a distance (d) from the center (18) of the second disc which is smaller than the radius (r) of the second disc. At the same distance (d) from the center (18) a passage (29) is provided in the second disc (17), which passage is arranged to guide the instrument (1) in the first coordinate direction (Z). |
