Optimizing imaging parameters for MR evaluation of the spine with titanium pedicle screws

Abstract

OBJECTIVE. This study examined the contribution and interdependence of multiple imaging parameters in clinical imaging sequences to aid practicing radiologists in minimizing artifacts during MR imaging of the spine after implantation of titanium pedicle screws. MATERIALS AND METHODS. A lumbar spine specimen with titanium pedicle screws implanted in the pedicle was imaged with a 1.5-T scanner. Sequence type, voxel volume, TE, and bandwidth varied. Different voxel volumes were achieved by altering section thickness, field of view (FOV), and matrix size. Artifact size was measured on sagittal and axial images at the midpedicle level. Artifact size was expressed as a percentage of actual screw size, and mean artifact size was calculated for each sequence. Analysis of variance without replication was done. RESULTS. Mean artifact size ranged from 231% to 364% of actual screw size. Artifact size was independent of voxel volume for voxels greater than 3 mm3 (p < .001). Artifact size decreased significantly [p