Correcting B0 Field Distortions in MRI Caused by Stainless Steel Orthodontic Appliances at 1.5 T Using Permanent Magnets – A Head Phantom Study

Abstract

Susceptibility artifacts caused by stainless steel orthodontic appliances (braces) pose significant challenges in clinical brain MRI examinations. We introduced field correction device (FCD) utilizing permanent magnets to cancel the induced B0 inhomogeneity and mitigate geometric distortions in MRI. We evaluated a prototype FCD using a 3D-printed head phantom in this proof of concept study. The phantom was compartmented into anterior frontal lobe, temporal lobe, fronto-parieto-occipital lobe, basal ganglia and thalami, brain stem, and cerebellum and had built-in orthogonal gridlines to facilitate the quantification of geometric distortions and volume obliterations. Stainless steel braces were mounted on dental models of three different sizes with total induced magnetic moment 0.15 to 0.17 A·m2. With braces B0 standard deviation (SD) ranged from 2.8 to 3.7 ppm in the temporal and anterior frontal lobes vs. 0.2 to 0.3 ppm without braces. The volume of brain regions in diffusion weighted imaging was obliterated by 32–38% with braces vs. 0% without braces in the cerebellum. With the FCD the SD of B0 ranged from 0.3 to 1.2 ppm, and obliterated volume ranged from 0 to 6% in the corresponding brain areas. These results showed that FCD can effectively decrease susceptibility artifacts from orthodontic appliances.

Diffusion-weighted MR imaging of musculoskeletal tissues: incremental role over conventional MR imaging in bone, soft tissue, and nerve lesions

“…For example, yellow bone marrow exhibits a low DWI SI and very low ADC values because of its abundance of fat cells (and thus hydrophobicity) while red marrow shows a higher DWI SI and ADC values due to its higher water content and cellularity ( Figure 4 ). 6 A range of ADC values by structure and tissue type is displayed in Table 2 . In addition to the DWI offering insight into the water content and cellular density of body tissues, DWI also offers improved visualization of small structures due to excellent background suppression, e.g .…”

Magnetic resonance imaging investigations in patients with metallic dental prosthesis: “The associated dilemma for medical fraternity and the dentist's role”

“…Some authors have mentioned the use of a mouthpiece as a spacer for avoiding backscatter and other prototypes of field correcting devices. [ 24 25 ] The MRI safe splint is an innovative technique and is helpful to assure safety during the MRI, it can be advised and fabricated during the pre MRI dental examination.…”