Patent Number: 
Section: claims

1. A grid holding device for a medical X-ray diagnostic system, which device is adapted to cooperate with a flexible, plate-shaped X-ray grid (401), which in a flat state has a first convergence distance, and which device comprises a flexing means for flexing the X-ray grid in order to adjust the convergence distance of the X-ray grid, wherein the flexing means comprises a first means (404) for flexing the X-ray grid in a first direction from the flat state to a first predetermined flexed position, in which the grid has a second convergence distance, which is longer than the first convergence distance, and a second means (404′) for flexing the X-ray grid in a second direction from the flat state to a second predetermined flexed position, in which the grid has a third convergence distance, which is shorter than the first convergence distance. 2. A grid holding device as claimed in claim 1, in which the first means for flexing comprises a first inflatable element (404) with an elastic wall, which is arranged to exert a pressure, when the element is inflated, on one surface of the X-ray grid (401). 3. A grid holding device as claimed in claim 2, in which the second means for flexing comprises a second inflatable element (404′) with an elastic wall, which is arranged to exert a pressure, when the second element is inflated, on the other surface of the X-ray grid (401). 4. A grid holding device as claimed in claim 3, in which the walls of the inflatable elements are arranged to exert a pressure on the X-ray grid in an area, which is located about a centre line (311) between two opposite edges of the grid (301). 5. A grid holding device as claimed in claim 1, further comprising a box with a lid (402) and a bottom (403), which box is arranged to contain the X-ray grid (401) and in which box said first (404) and second (404′) means for flexing are accommodated. 6. A grid holding device as claimed in claim 5, in which the box comprises at least a first (405, 405′) and a second (407, 407′) pair of resilient beads, the first bead (405, 407) in each pair being attached to the underside of the lid (402) and the second bead (405′, 407′) in each pair being attached to the bottom (403) of the box, opposite the first bead in the respective pairs, and the pairs of beads being arranged to fix the X-ray grid (401) in the box. 7. A grid holding device as claimed in claim 6, in which the pressure in at least one of the beads is variable. 8. A grid device, comprising a flexible, plate-shaped X-ray grid (401), which in a flat state has a first convergence distance, and a grid holding device as claimed in claim 1. 9. A grid device as claimed in claim 8, in which the first convergence distance is in the range of 110–130 cm, the second convergence distance is in the range of 170–190 cm and the third convergence distance is in the range of 70–90 cm. 10. An X-ray diagnostic system, comprising a grid holding device as claimed in claim 1. 11. An X-ray diagnostic system, comprising a grid device as claimed in claim 8. 12. A grid holding device as claimed in claim 2, further comprising a box with a lid (402) and a bottom (403), which box is arranged to contain the X-ray grid (401) and in which box said first (404) and second (404′) means for flexing are accommodated. 13. A grid holding device as claimed in claim 3, further comprising a box with a lid (402) and a bottom (403), which box is arranged to contain the X-ray grid (401) and in which box said first (404) and second (404′) means for flexing are accommodated. 14. A grid holding device as claimed in claim 4, further comprising a box with a lid (402) and a bottom (403), which box is arranged to contain the X-ray grid (401) and in which box said first (404) and second (404′) means for flexing are accommodated. 15. A grid device, comprising a flexible, plate-shaped X-ray grid (401), which in a flat state has a first convergence distance, and a grid holding device as claimed in claim 2. 16. A grid device, comprising a flexible, plate-shaped X-ray grid (401), which in a flat state has a first convergence distance, and a grid holding device as claimed in claim 3. 17. A grid device, comprising a flexible, plate-shaped X-ray grid (401), which in a flat state has a first convergence distance, and a grid holding device as claimed in claim 4. 18. An X-ray diagnostic system, comprising a grid holding device as claimed in claim 2. 19. An X-ray diagnostic system, comprising a grid holding device as claimed in claim 3. 20. An X-ray diagnostic system, comprising a grid device as claimed in claim 9.