| Objective 1. To explore the imaging manifestations of loosening of the cementless artificial hip prosthesis. 2. To explore the effect of Multi-detector computed tomography(MDCT) scan parameters and post-processing imaging methods on metallic artifacts, so as to achieve the perfection in reduction of artifacts caused by metallic implants.Materials and methods 1. X-ray plain films and CT images before the first revision after the cementless artificial hip replacement of 37 cases were analyzed retrospectively and contrasted with the intraoperative exploration results. Then the relationship between the prosthesis loosening and the thickness and zones involving of the radiolucent line, the fracture of the screw of acetabular cup and the lucent line around the screw were summaried. 2. Titanium water phantom designed by us was scanned under MDCT with alternating scan parameters including tube voltage, tube current, pitch and focal spot. Then the areas of image artifacts were measured to evaluate their relevance. 15 postoperative patients with images of vertebral implantation were obtained under conventional scan parameters and were post-processed by using optimized reconstruction and conventional methods such as multi-planar reconstruction(MPR), window width and level adjustment, volume rendering technique(VRT) and then evaluation of the quality of images.Results 1.(1)16 cases of no loosening acetabular prosthesis: 6 cases with no radiolucent line in zones I~III(37.5%); 4 cases with >2mm radiolucent line in one zone(25.0%); 2 cases with ≤2mm lucent line in zones I and II(12.5%); 4 cases with ≤2mm radiolucent line in zones I~III, but at least with one zone ≤1mm(25.0%);(2) 12 cases of loosening acetabular prosthesis: 5 cases with >2mm radiolucent line at least in twozones(41.7%); 4 cases with >1mm radiolucent line in zones I~III(33.3%); 2 cases with >1mm radiolucent line in only one zone; 1 case with radiolucent line in zones I~III as well as ≤1mm radiolucent line in one zone;(3) 18 cases of no loosening femoral prosthesis: 12 cases with on radiolucent line(66.7%); 6 cases with the scattered radiolucent line(33.3%), 5 of them involving no more than two zones;(4) 10 cases of aseptic loosening femoral prosthesis : 3 cases with >1mm radiolucent line in zones 1~7(30.0%); 4 cases with >1mm radiolucent line in zones 1, 4 and 7(40.0%); 3 cases with >1mm radiolucent line in zones 1~3 or 4~7(30.0%);(5) 6 cases of infectious loosening femoral prosthesis: 1 case with >2mm radiolucent line in four zones and skin antrum formation, the other cases just with radiolucent line in no more than three zones;(6) 19 cases of acetabular prosthesis with screws: 9 cases with no loosening, and the screw with no fracture and >2mm radiolucent line; the other 10 cases, 3 of them with screw fractures, 4 of them with >2mm radiolucent line, and the other 3 cases with on screw fractures and no >2mm radiolucent line. 2. Under varying tube voltage, pitch, and focal spot scanning, the difference in area of artifacts was statistically significant. With the increase of tube voltage or the decrease of pitch, area of artifact declined gradually. Scan done with small focal spot showed the area of artifact smaller than the scan done with larger focal spot. Under different tube currents, there was no significant difference statistically. Usage of soft tissue algorithm(Kernel B40f) in bone window reconstruction, wide windows(2000HU window width, 600 HU window level) and VRT could improve image quality.Conclusion 1. Imaging provides a good evaluation for loosening of the cementless artificial hip prosthesis, but the application of CT was limited by its metallic artifacts to a certain extent. 2. Selection of appropriate MDCT scan parameters and post-processing imaging methods can reduce the metal artifacts, which leads to the improvement of image quality and diagnosis. |
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