title: Magnetic resonance imaging of the inferior alveolar nerve with special regard to metal artifact reduction.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) is an excellent imaging modality for displaying peripheral nerves. Since the knowledge about MRI of the inferior alveolar nerve (IAN) is limited, this pilot study aims to identify the prospects and limitations of MRI of the IAN, with special consideration of metal artifacts.
  
  
  METHODS
  Initially, in vitro MRI of a dental implant was performed to establish an optimized protocol for metal artifact reduction using WARP sequences (a software package provided by Siemens Healthcare, Erlangen, Germany) including view angle tilting (VAT) and slice-encoding metal artifact correction (SEMAC) techniques. MRI with this optimized protocol was performed in three volunteers and four patients presenting with postoperative IAN impairment. Measuring the evaluable area and the artifact size was performed to assess the benefit of the specific artifact reduction sequences.
  
  
  RESULTS
  In vitro imaging of a dental implant demonstrated that WARP sequences with VAT and SEMAC techniques led to a volume reduction of the artifact of up to 69.1%. Observations in both volunteers and patients with neurosensory IAN impairment showed a distinct artifact reduction with the MRI protocol adapted to metallic materials. Additionally VAT and SEMAC techniques improved the imaging due to further artifact reduction. As a main drawback of the VAT technique, the image quality was compromised by a blurring effect. Still, on 3-T MRI the resolution was high enough to reveal even fine structures. Imaging of the IAN was successful in all cases despite metallic material in the region of interest, and structural IAN changes could be detected in correlation with clinical symptoms.
  
  
  CONCLUSIONS
  In contrast to conventional radiography and computed tomography, MRI can directly depict the IAN and provide reliable information on its position and exact course within the mandible. MRI offers an objective assessment of IAN injuries, supporting the decision-making process regarding surgical exploration and microneural repair. With the advent of specialized MRI techniques such as VAT and SEMAC, reduction of metal artifacts is considerably improved.
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology (Head: Prof. C. Zimmer), Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany. Electronic address: monika.probst@tum.de.
authors.forename: Monika
authors.initials: M
authors.lastname: Probst
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Tuebingen, Eberhard Karls University Tuebingen, Hoppe-Seyler-Straße 3, 72076, Tuebingen, Germany.
authors.forename: Vivien
authors.initials: V
authors.lastname: Richter
authors.affiliation: Department of Oral and Maxillofacial Surgery, Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Weitz
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology (Head: Prof. C. Zimmer), Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany.
authors.forename: Jan Stefan
authors.initials: JS
authors.lastname: Kirschke
authors.affiliation: Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Ismaninger Straße 22, 81675, Munich, Technical University Munich, Germany.
authors.forename: Carl
authors.initials: C
authors.lastname: Ganter
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ludwig Maximilians University of Munich, Lindwurmstraße 2a, 80337, Munich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Troeltzsch
authors.affiliation: Siemens AG, Healthcare Sector, Allee am Roethelheimpark 2, 91052, Erlangen, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Nittka
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ludwig Maximilians University of Munich, Lindwurmstraße 2a, 80337, Munich, Germany.
authors.forename: Carl-Peter
authors.initials: CP
authors.lastname: Cornelius
authors.affiliation: Department of Diagnostic and Interventional Neuroradiology (Head: Prof. C. Zimmer), Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Zimmer
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ludwig Maximilians University of Munich, Lindwurmstraße 2a, 80337, Munich, Germany.
authors.forename: Florian Andreas
authors.initials: FA
authors.lastname: Probst
mesh_terms: D016477:Artifacts; D015921:Dental Implants; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D008340:Mandibular Nerve / Q000000981:diagnostic imaging*; D008670:Metals; D010865:Pilot Projects
chemical_list: D015921:Dental Implants; D008670:Metals
keywords: Inferior alveolar nerve; MRI; Metal artifact reduction; SEMAC; VAT; View-angle tilting