A computer simulation of the metallic artifacts in MRI caused by dental magnetic attachments

Abstract

Dental magnetic attachments, which are relatively simple to use and provide good retention and stability, have been increasingly used as dental prostheses. These attachments are composed of ferromagnetic stainless-steel keepers and magnetic assemblies embedded in the denture. The use of magnetic resonance imaging (MRI) to investigate lesions in the oral and maxillofacial areas is quite common. When a patient with a magnetic keeper undergoes MRI examination of the oral or maxillofacial area, however, the keeper is considered a metallic artifact (MA). Depending on the location of the lesion requiring diagnosis, the patient may be required to remove the keeper. The extent of the MA is known to be related to the hardware and pulse sequence parameters and the magnetic properties of the keeper. In this study, we propose a new method to estimate the extent of the MA in MR images caused by a keeper placed in the MRI, approximating the keeper with a magnetic dipole. This method should allow us to express the relationship among the hardware and pulse sequence parameters, the magnetic properties of the keeper and the extent of the MA in the MR image. To evaluate the validity of the method, we compare the MA in MR images produced by the proposed method with those in any experimental MR images taken in the existing study. Via our computer simulations, we show that the proposed method outperformed the existing approach and can estimate the extent of the MA based on the hardware and pulse sequence parameters and the magnetic properties of the keeper. By estimating the extent of the MA in the MR image by using our method before the MRI examination, depending on the location of the lesion requiring diagnosis, it may not be necessary to remove the keeper.