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Effect of Magnetic Resonance Imaging Field Strength on Delineation and Signal Intensity of Alar Ligaments in Healthy Volunteers

Lummel, Nina, MD*; Schöpf, Veronika, Dipl.Ing; Bitterling, Harro, MD; Zeif, Christian, MD*; Kloetzer, Andrea, MD*; Brückmann, Hartmut, MD*; Linn, Jennifer, MD*

doi: 10.1097/BRS.0b013e31825831ca

Study Design. A prospective study of healthy volunteers.

Objective. To evaluate the influence of magnetic resonance imaging (MRI) field strength on the delineation and signal intensity of alar ligaments (AL) in healthy volunteers.

Summary of Background Data. The fact that AL physiologically show morphologic variabilities is well established. However, presence and etiology of high-signal intensities within the AL as well as the influence of the MRI field strength on the signal characteristics of AL are still not completely understood.

Methods. Coronal and sagittal 2-mm proton-density weighted sequences were acquired in 50 healthy volunteers using different MRI field strengths (1 T, 1.5 T, 3 T). Delineation and signal characteristics of AL were evaluated by 2 neuroradiologists independently. Differences concerning delineation and signal intensity between the MRI scanners, inter rater reliability between the 2 readers, and intrarater reliability at different time points were calculated.

Results. Delineation of AL was significantly better both on 3 T and 1.5 T than on 1 T (P = 0.05) in sagittal as well as in coronal view. In coronal view delineation was significantly better on 3 T than on 1.5 T, whereas in sagittal view no significant difference was evident when comparing 1.5 T and 3 T. Concerning signal intensity of AL in sagittal view, there was no significant difference between the 3 different field strengths. Inter-rater and intrarater agreements were fair to moderate with respect to delineation as well as signal intensity of AL.

Conclusion. 1.5 T and 3 T significantly improve the delineation of AL when compared with lower field strength (1 T), but signal intensity of the AL in healthy volunteers is not influenced by the field strength. Increased signal is present in asymptomatic subjects on both low- and high-field magnetic resonance systems. Accordingly, the pathologic relevance of increased signal intensity of the AL, regardless of field strength, may not be indicative of traumatic AL injury.

In this study, we could verify that high-field magnetic resonance imaging (MRI) (1.5 T, 3 T) was superior to low-field MRI (1 T) in the delineation of alar ligaments (AL). However, an influence of the MRI field strength on the signal intensity of AL was not detectable, and hyperintense signal alterations of AL were present in healthy volunteers at high- and low-field strengths and thus have per se no pathologic relevance.

*Department of Neuroradiology, University of Munich, Munich, Germany

MR Centre of Excellence, Medical University Vienna, Vienna, Austria

Sygehus Sønderjyll, Sønderborg, Danmark.

Address correspondence and reprint requests to Nina Lummel, MD, Department of Neuroradiology, University of Munich, Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany; E-mail:

Acknowledgment date: September 6, 2011. First revision: December 2, 2011. Second revision date: January 25, 2012. Third revision date: March 13, 2012. Acceptance date: March 16, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work.

No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

© 2012 Lippincott Williams & Wilkins, Inc.