MRI vs. CT for orthodontic applications: comparison of two MRI protocols and three CT (multislice, cone-beam, industrial) technologies.
OBJECTIVE
To examine the relative usefulness and suitability of magnetic resonance imaging (MRI) in daily clinical practice as compared to various technologies of computed tomography (CT) in addressing questions of orthodontic interest.


METHODS
Three blinded raters evaluated 2D slices and 3D reconstructions created from scans of two pig heads. Five imaging modalities were used, including three CT technologies-multislice (MSCT), cone-beam CT (CBCT), and industrial (µCT)-and two MRI protocols with different scan durations. Defined orthodontic parameters were rated one by one on the 2D slices and the 3D reconstructions, followed by final overall ratings for each modality. A mixed linear model was used for statistical analysis.


RESULTS
Based on the 2D slices, the parameter of visualizing tooth-germ topography did not yield any significantly different ratings for MRI versus any of the CT scans. While some ratings for the other parameters did involve significant differences, how these should be interpreted depends greatly on the relevance of each parameter. Based on the 3D reconstructions, the only significant difference between technologies was noted for the parameter of visualizing root-surface morphology. Based on the final overall ratings, the imaging performance of the standard MRI protocol was noninferior to the performance of the three CT technologies.


CONCLUSIONS
On comparing the imaging performance of MRI and CT scans, it becomes clear that MRI has a huge potential for applications in daily clinical practice. Given its additional benefits of a good contrast ratio and complete absence of ionizing radiation, further studies are needed to explore this clinical potential in greater detail.
Department of Orthodontics and Orofacial Orthopedics, University of Erlangen Medical School, Erlangen, Germany. andreas.detterbeck@uk-erlangen.de.
Andreas
A
Detterbeck
Department of Orthodontics and Orofacial Orthopedics, University of Erlangen Medical School, Erlangen, Germany.
Michael
M
Hofmeister
Department of Orthodontics and Orofacial Orthopedics, University of Erlangen Medical School, Erlangen, Germany.
Elisabeth
E
Hofmann
Research Center for Magnetic Resonance Bavaria (MRB), Würzburg, Germany.
Daniel
D
Haddad
Research Center for Magnetic Resonance Bavaria (MRB), Würzburg, Germany.
Daniel
D
Weber
Fraunhofer Institute for Integrated Circuits (IIS), Project Group NanoCT Systems, Würzburg, Germany.
Astrid
A
Hölzing
Fraunhofer Institute for Integrated Circuits (IIS), Project Group NanoCT Systems, Würzburg, Germany.
Simon
S
Zabler
Institute for Medical Biometry, Informatics and Epidemiology (IMBIE), University of Bonn, Bonn, Germany.
Matthias
M
Schmid
Research Center for Magnetic Resonance Bavaria (MRB), Würzburg, Germany.
Karl-Heinz
KH
Hiller
Research Center for Magnetic Resonance Bavaria (MRB), Würzburg, Germany.
Peter
P
Jakob
Fraunhofer Institute for Integrated Circuits (IIS), Project Group NanoCT Systems, Würzburg, Germany.
Jens
J
Engel
Fraunhofer Institute for Integrated Circuits (IIS), Application Center for Computed Tomography in Metrology, Deggendorf, Germany.
Jochen
J
Hiller
Department of Orthodontics and Orofacial Orthopedics, University of Erlangen Medical School, Erlangen, Germany.
Ursula
U
Hirschfelder
D000818:Animals; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D007221:Industry / Q000379:methods; D007568:Jaw / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D061330:Multidetector Computed Tomography / Q000379:methods*; D015588:Observer Variation; D011861:Radiography, Dental / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D013552:Swine; D013673:Technology Assessment, Biomedical; D014070:Tooth / Q000000981:diagnostic imaging*
Computed tomography; Cone-beam computed tomography; Magnetic resonance imaging; Multislice computed tomography; Three-dimensional imaging