| The number of cases of total hip replacement(THR)with artificial joint is increasing every year, and the follow-up of these cases has become extremely important. The dimension of the prosthesis from the femoral head region to the tip of the stem differs greatly, resulting in differences in x-ray absorption. Therefore, it is difficult to visualize the entire prosthesis on a single axial projection radiograph. We manufactured a density-compensating filter after measuring differences in the ratio exposure quantity at six reference points on axial projection images of the hip joint. Measured ratio exposure quantities at reference points 1-6 were 14.14, 21.42, 26.87, 30.76, 38.61, and 49.32, respectively. Accordingly, the thicknesses of the acryl component of our filter were 1.0, 3.0, 4.5, 5.0, 6.8, and 7.5 mm, respectively. With our filter, the entire artificial joint system could be visualized in an axial projection radiograph of the hip. Further, radiation could be reduced by 49.3, 61.6, 70.3, 75.8, 82.4, and 84.3% at locations 1-6, respectively. |
