Pia M. Jungmann MD, Presenter: Nothing to Disclose

Christoph Schaeffeler MD, Abstract Co-Author: Nothing to Disclose

Reinhard Meier MD, PhD, Abstract Co-Author: Nothing to Disclose

Carl Ganter MSc, PhD, Abstract Co-Author: Nothing to Disclose

Ernst J. Rummeny MD, Abstract Co-Author: Nothing to Disclose

Klaus Woertler MD, Abstract Co-Author: Nothing to Disclose

To compare WARP metal artifact-reducing techniques, that combine slice-encoding metal artifact correction (SEMAC), view-angle tilting (VAT) and increased bandwidth with conventional metal artifact-reducing MR sequences in the assessment of periprosthetic soft tissue abnormalities.

Twenty-five patients (13 male,12 female) with metal implants (n=30), referred for MR imaging to evaluate tumor-recurrence or periprosthetic infection, were included. At 1.5T, WARP-techniques and conventional metal artifact-reducing MR sequences (standard-group) were compared for two pulse sequences: Coronal short-tau-inversion-recovery (STIR; n=19 patients) and coronal contrast enhanced T1-weighted (w) sequences (n=19 patients). Quantitative artifact diameters were measured by two experienced radiologists in consensus at four randomly selected spots for each implant. Qualitative parameters were assessed on a five-point scale (1=best, 5=worst): “image distortion”, “artificial signal changes at the edges”, and “diagnostic confidence”. T-tests (quantitative assessment) and Wilcoxon-signed rank tests (qualitative assessment) were used for statistical analyses.

Implants were located at the upper extremity (4/30; humerus or radius), at the lumbar spine (4/30) or at the lower extremity (22/30; proximal femur, knee or tibia). In 3 cases, tumor-recurrence, in 7 cases infection and in 12 cases other pathologies were diagnosed (Figure). Artifacts were significantly reduced in the WARP-group as compared with the standard-group. For STIR images, the mean difference of artifact diameters (±SD) was 10.2±1.6mm (P<0.001; T1-w, 4.1±0.6mm, P<0.001). On images with WARP-techniques, "distortion" and "artificial signal changes" were reduced (STIR, P=0.021, P=0.060; T1-w, P<0.001, P<0.001) and "diagnostic confidence" improved (STIR, 2.1±0.9 vs 3.5±1.9, P=0.002; T1-w, 1.4±0.7 vs 2.8±1.2, P=0.001).

Significant reduction of through-plane and in-plane artifacts was achieved by application of WARP-techniques. These new techniques improved diagnostic image-quality and may be beneficial for detecting periprosthetic pathologies during postoperative follow-up.

New WARP-techniques appear applicable for postoperative follow-up MR imaging of patients with metal implants and suspicion of periprosthetic infection or tumor recurrence.

Jungmann, P, Schaeffeler, C, Meier, R, Ganter, C, Rummeny, E, Woertler, K, View-angle Tilting and Slice-encoding Metal Artifact Correction: Reduction of Artifacts in MR Imaging of Patients with Metal Implants and Suspicion of Infection or Tumor-Recurrence.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14011690.html