title: The accuracy of ultrashort echo time MRI sequences for medical additive manufacturing.
abstract: Additively manufactured bone models, implants and drill guides are becoming increasingly popular amongst maxillofacial surgeons and dentists. To date, such constructs are commonly manufactured using CT technology that induces ionizing radiation. Recently, ultrashort echo time (UTE) MRI sequences have been developed that allow radiation-free imaging of facial bones. The aim of the present study was to assess the feasibility of UTE MRI sequences for medical additive manufacturing (AM).
  
  
  
  Three morphologically different dry human mandibles were scanned using a CT and MRI scanner. Additionally, optical scans of all three mandibles were made to acquire a "gold standard". All CT and MRI scans were converted into Standard Tessellation Language (STL) models and geometrically compared with the gold standard. To quantify the accuracy of the AM process, the CT, MRI and gold-standard STL models of one of the mandibles were additively manufactured, optically scanned and compared with the original gold-standard STL model.
  
  
  
  Geometric differences between all three CT-derived STL models and the gold standard were <1.0 mm. All three MRI-derived STL models generally presented deviations <1.5 mm in the symphyseal and mandibular area. The AM process introduced minor deviations of <0.5 mm.
  
  
  
  This study demonstrates that MRI using UTE sequences is a feasible alternative to CT in generating STL models of the mandible and would therefore be suitable for surgical planning and AM. Further in vivo studies are necessary to assess the usability of UTE MRI sequences in clinical settings.
authors.affiliation: 1 Department of Oral and Maxillofacial Surgery/Oral Pathology and 3D InnovationLab, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Maureen
authors.identifier: 0000-0001-9208-283X
authors.initials: M
authors.lastname: van Eijnatten
authors.affiliation: 2 Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Erik-Jan
authors.initials: EJ
authors.lastname: Rijkhorst
authors.affiliation: 2 Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Mark
authors.initials: M
authors.lastname: Hofman
authors.affiliation: 1 Department of Oral and Maxillofacial Surgery/Oral Pathology and 3D InnovationLab, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Tymour
authors.initials: T
authors.lastname: Forouzanfar
authors.affiliation: 1 Department of Oral and Maxillofacial Surgery/Oral Pathology and 3D InnovationLab, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Wolff
mesh_terms: D002102:Cadaver; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging; D013997:Time Factors; D014057:Tomography, X-Ray Computed
keywords: X-ray computed; dimensional measurement accuracy; magnetic resonance imaging; printing; three-dimensional; tomography