[CT osteodensitometry in the area immediate to hip endoprostheses].

UNLABELLED

The value of metal artifact reduction in quantitative bone density determination in the vicinity of metallic implants was studied.

METHOD

Ten cadaver femora with hip endoprostheses implanted intra vitam were examined in CT with varying slice thicknesses, tube voltage, scan time and magnification factor. The artifact-laden images were then processed using a metal artifact reduction programme (MAR). The metallic implant was removed, allowing the bone slices to be examined again with the same imaging parameters, but without the bothersome metal artifacts. This allowed comparison of bone density values obtained before and after application of MAR with data obtained after implant removal.

RESULTS

A comparison of the bone density measurements between the sample group without implants and the group with indwelling implants prior to MAR showed an unexpected correlation coefficient r = 0.975-0.977. The correlation coefficients after MAR rose to r = 0.987-0.992 in 125 kV and r = 0.989-0.991 in 85 kV modes. The reproducibility of the density measurements for the groups without implants and with implants following MAR showed variation coefficients (VC) of 1.16% and 0.75% respectively. The reproducibility of the manual definition of the region of interest (ROI) in bone showed a VC = 2.19%.

CONCLUSIONS

Bone density in the vicinity of metallic implants can be reliably and reproducibly determined using MAR.