Spine MR images in patients with pedicle screw fixation: Comparison of conventional and SEMAC-VAT sequences at 1.5 T.

BACKGROUND AND PURPOSE: Slice-encoding metal artifact corrections (SEMAC)-view-angle tilting (VAT) sequences have recently been used in clinical protocols to reduce metal artifacts in MR scans of patients with spinal instrumentation. The objective of this study was to compare the SEMAC-VAT sequence with the conventional MR sequence with a low bandwidth turbo-spin echo (TSE) in terms of image quality, visibility of periprosthetic structures, and diagnostic confidence for detection of postoperative complications in patients who underwent pedicle screw fixation at 1.5 T.

METHODS: Seventy patients who underwent pedicle screw fixation between the thoracic vertebrae and the sacrum were included in the study. The MR scans were retrospectively evaluated by two radiologists for signal-to-noise ratio of anatomical structures and size of artifacts, visibility of periprosthetic anatomical structures, and diagnostic confidence for detection of postoperative complications on conventional TSE and on SEMAC-VAT images. Paired t-tests and Wilcoxon signed-rank tests were used for comparisons, and kappa values were used for inter-observer agreement.

RESULTS: SEMAC-VAT images demonstrated significantly fewer metal artifacts, providing improved delineation of most periprosthetic anatomical structures and higher diagnostic confidence for detection of postoperative complications compared with conventional TSE images (p < 0.001). For the spinal canal, however, the visibility of anatomical structures and diagnostic confidence for detection of postoperative complications were better for conventional TSE than for SEMAC-VAT imaging (p < 0.001).

CONCLUSION: In conclusion, although SEMAC-VAT can significantly reduce metal artifact and provide improved delineation of periprosthetic anatomical structures compared to conventional TSE images, TSE is better for spinal canal evaluation. Therefore, it is important to understand the advantages and disadvantages of SEMAC-VAT and to use it properly.