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Magnetic Resonance Imaging in Cadaver Dogs With Metallic Vertebral Implants at 3 Tesla: Evaluation of the WARP-Turbo Spin Echo Sequence

Griffin, John F. IV DVM, DACVR*; Archambault, Nicholas S. DVM; Mankin, Joseph M. DVM, DACVIM-Neurology; Wall, Corey R. MS, DVM, DACVR*; Thompson, James A. DVM, DVSc*; Padua, Abraham Jr BS§; Purdy, David PhD§; Kerwin, Sharon C. MS, DVM, DACVS

doi: 10.1097/BRS.0b013e3182a58b14

Study Design. Laboratory investigation, ex vivo.

Objective. Postoperative complications are common after spinal implantation procedures, and magnetic resonance imaging (MRI) would be the ideal modality to image these patients. Unfortunately, the implants cause artifacts that can render MRI nondiagnostic. The WARP-turbo spin echo (TSE) sequence has been developed to mitigate artifacts caused by metal. The objective of this investigation was to evaluate the performance of the WARP-TSE sequence in canine cadaver specimens after implantation with metallic vertebral implants.

Summary of Background Data. Magnetic field strength, implant type, and MRI acquisition technique all play a role in the severity of susceptibility artifacts. The WARP-TSE sequence uses increased bandwidth, view angle tilting, and SEMAC (slice-encoding metal artifact correction) to correct for susceptibility artifact. The WARP-TSE technique has outperformed conventional techniques in patients, after total hip arthroplasty. However, published reports of its application in subjects with vertebral column implants are lacking.

Methods. Ex vivo anterior stabilization of the atlantoaxial joint was performed on 6 adult small breed (<8 kg) cadaver dogs using stainless steel screws and polymethylmethacrylate. Axial and sagittal T2-weighted and short tau inversion recovery MRI was performed using conventional pulse sequences and WARP-TSE sequences at 3 T. Images were assessed qualitatively and quantitatively.

Results. Images made with the WARP-TSE sequence had smaller susceptibility artifacts and superior spinal cord margin depiction. WARP-TSE sequences reduced the length over which susceptibility artifacts caused spinal cord margin depiction interference by 24.9% to 71.5% with scan times of approximately 12 to 16 minutes.

Conclusion. The WARP-TSE sequence is a viable option for evaluating the vertebral column after implantation with stainless steel implants.

Level of Evidence: N/A

An anterior atlantoaxial stabilization procedure was performed on 6 canine cadaver specimens prior to magnetic resonance imaging (MRI) with the WARP-turbo spin echo (TSE) sequence and conventional MRI. The WARP-TSE sequence reduced the size of susceptibility artifacts and improved spinal cord margin depiction with scan times of approximately 12 to 16 minutes.

*Department of Veterinary Large Animal Clinical Sciences, Texas A&M University, College Station, TX

Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO

Department of Veterinary Small Animal Clinical Sciences, Texas A&M University, College Station, TX; and

§Siemens Medical Solutions, Malvern, PA.

Address correspondence and reprint requests to John F. Griffin IV, DVM, DACVR, 4475-TAMU, College Station, TX; E-mail:

Acknowledgment date: February 4, 2013. First revision date: June 4, 2013. Second revision date: July 13, 2013. Acceptance: July 16, 2013.

The device(s)/drug(s) that is/are the subject of this manuscript is/are exempt from FDA or corresponding national regulations.

My manuscript includes unlabeled/investigational uses of the products/devices listed below and the status of these is disclosed in the manuscript: WARP-Turbo Spin Echo MRI sequence.

Department of Veterinary Small Animal Clinical Sciences, Texas A&M University funds were received to support this work.

No relevant financial activities outside the submitted work.

© 2013 by Lippincott Williams & Wilkins