[Improvement of the Radiographic Contrast in Off-center Radiography with Focused Grid].

In radiography with focused grid, it is important to agree the X-ray center on the grid center. Actually, radiography is often put the off-center alignment which disagrees the X-ray center to the grid center. This misalignment decreases radiographic contrast because of cutoff the primary X-rays. The grid-tilt technique which makes the grid tilt corresponding to the misalignment of the X-ray center and the grid center was investigated. Using solid state dosimeter and 10 cm water phantom, transited dose of focused grids (focal distance 120 cm, grid ratio 6:1 and 8:1) were measured at off-center. The transited dose at 6 cm off-center by conventional manner was lower 20% (6:1) and 30% (8:1) to center's one. While by grid-tilt technique, the transited dose at off-center was same to the center's one. Axial radiography of hip joint was applied by this technique.