Author: Avneesh Chhabra, Zhiyue J. Wang, Qing Yuan 👨🔬
Affiliation: University of Texas Southwestern Medical Center 🌍
Purpose: Magnetic susceptibility artifacts from dental arches and hardware often compromise MRI neurography of jaw and facial nerves. This study aims to characterize these artifacts and provide insights to guide corrective measures for enhancing imaging quality and interpretations.
Methods: B0 mapping using 3D gradient echo sequences was performed on 16 patients undergoing maxillofacial and jaw nerve MR neurography at 3T. All patients had dental hardware that may induce susceptibility artifacts. Phase maps were analyzed to quantify the magnetic moment of the artifact sources relative to surrounding tissues.
Results: Significant susceptibility artifacts were observed in 8 out of 16 patients. In 7 of these 8 patients, B0 phase maps displayed distinct magnetic dipole patterns from a point-like source, indicating that the sources are confined to a compact volume, whereas in one case, the source is distributed along a line on dental arch. Two cases exhibited a dipole strength comparable to that of a stainless-steel dental bracket, with a magnetic moment of m=0.0003 and 0.005 Am2, respectively. In 5 patients, the artifacts were attributed to a point-like air-space source within the dental arch (median m=3.3x10-5, range 0.5x10-5 to 6.0x10-5 Am2) , resembling susceptibility artifacts commonly observed around paranasal sinuses. Theoretically, 1 cc of air space in tissue induces a magnetic moment of approximately 0.00002 Am2 at 3T. These air-space-related artifacts were severe enough to interfere with MR neurography pulse sequences, significantly compromising the visibility of the inferior alveolar and lingual nerves.
Conclusion: Magnetic susceptibility artifacts may originate from dental implants, but can also result from missing teeth, where air-filled spaces act as paramagnetic sources relative to the surrounding diamagnetic tissue. Simple corrective measures, such as filling the space with chewing gum, could potentially mitigate these artifacts. Further testing is required to validate these approaches and improve imaging quality.