title: CT Metal Artifact Reduction in the Spine: Can an Iterative Reconstruction Technique Improve Visualization?
abstract: OBJECTIVE
  Metal-related artifacts from spine instrumentation can obscure relevant anatomy and pathology. We evaluated the ability of CT images reconstructed with and without iterative metal artifact reduction to visualize critical anatomic structures in postoperative spines and assessed the potential for implementation into clinical practice.
  
  
  METHODS
  We archived CT projection data in patients with instrumented spinal fusion. CT images were reconstructed by using weighted filtered back-projection and iterative metal artifact reduction. Two neuroradiologists evaluated images in the region of spinal hardware and assigned a score for the visualization of critical anatomic structures by using soft-tissue and bone windows (critical structures totally obscured, n = 0; anatomic recognition with high diagnostic confidence, n = 5). Using bone windows, we measured the length of the most pronounced linear artifacts. For each patient, neuroradiologists made recommendations regarding the optimal use of iterative metal artifact reduction and its impact on diagnostic confidence.
  
  
  RESULTS
  Sixty-eight patients met the inclusion criteria. Visualization of critical soft-tissue anatomic structures was significantly improved by using iterative metal artifact reduction compared with weighted filtered back-projection (median, 1 ± 1.5 versus 3 ± 1.3, P < .001), with improvement in the worst visualized anatomic structure in 88% (60/68) of patients. There was not significant improvement in visualization of critical osseous structures. Linear metal artifacts were reduced from 29 to 11 mm (P < .001). In 87% of patients, neuroradiologists recommended reconstructing iterative metal artifact reduction images instead of weighted filtered back-projection images, with definite improvement in diagnostic confidence in 32% (22/68).
  
  
  CONCLUSIONS
  Iterative metal artifact reduction improves visualization of critical soft-tissue structures in patients with spinal hardware. Routine generation of these images in addition to routine weighted filtered back-projection is recommended.
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota Kotsenas.amy@mayo.edu.
authors.forename: A L
authors.identifier: http://orcid.org/0000-0003-0463-955X
authors.initials: AL
authors.lastname: Kotsenas
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota.
authors.forename: G J
authors.initials: GJ
authors.lastname: Michalak
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota.
authors.forename: D R
authors.initials: DR
authors.lastname: DeLone
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota.
authors.forename: F E
authors.initials: FE
authors.lastname: Diehn
authors.affiliation: Siemens Medical Solutions (K.G., A.F.H.), Malvern, Pennsylvania.
authors.forename: K
authors.initials: K
authors.lastname: Grant
authors.affiliation: Siemens Medical Solutions (K.G., A.F.H.), Malvern, Pennsylvania.
authors.forename: A F
authors.initials: AF
authors.lastname: Halaweish
authors.affiliation: Siemens Healthcare (A.K., R.R., B.S.), Forchheim, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Krauss
authors.affiliation: Siemens Healthcare (A.K., R.R., B.S.), Forchheim, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Raupach
authors.affiliation: Siemens Healthcare (A.K., R.R., B.S.), Forchheim, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schmidt
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota.
authors.forename: C H
authors.initials: CH
authors.lastname: McCollough
authors.affiliation: From the Department of Radiology (A.L.K., G.J.M., D.R.D., F.E.D., C.H.M., J.G.F.), Mayo Clinic, Rochester, Minnesota.
authors.forename: J G
authors.initials: JG
authors.lastname: Fletcher
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D005260:Female; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D019736:Prostheses and Implants; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008670:Metals