Influence of pulse sequence parameters at 1.5 T and 3.0 T on MRI artefacts produced by metal–ceramic restorations

Abstract

Objectives: Susceptibility artefacts from dental materials may compromise MRI diagnosis. However, little is known regarding MRI artefacts of dental material samples with the clinical shapes used in dentistry. The present phantom study aims to clarify how pulse sequences and sequence parameters affect MRI artefacts caused by metal-ceramic restorations. Methods: A phantom consisting of nickel-chromium metal-ceramic restorations (i.e. dental crowns and fixed bridges) and cylindrical reference specimens immersed in agar gel was imaged in 1.5 and 3.0 T MRI scanners. Gradient echo (GRE), spin echo (SE) and ultrashort echo time (UTE) pulse sequences were used. The artefact area in each image was automatically calculated from the pixel values within a region of interest. Mean values for similar pulse sequences differing in one parameter at a time were compared. A comparison between mean artefact area at 1.5 and 3.0 T, and from GRE and SE was also carried out. In addition, a parametric correlation between echo time (TE) and artefact area was performed. Results: A significant correlation was found between TE and artefact area in GRE images. Higher receiver bandwidth significantly reduced artefact area in SE images. UTE images yielded the smallest artefact area at 1.5 T. In addition, a significant difference in mean artefact area was found between images at 1.5 and 3.0 T field strengths (p 5 0.028) and between images from GRE and SE pulse sequences (p 5 0.005). Conclusions: It is possible to compensate the effect of higher field strength on MRI artefacts by setting optimized pulse sequences for scanning patients with metal-ceramic restorations.

Quantification of Artifacts in MR Images Caused by Commonly Used Dental Materials

“…In the current study, the size of artifact in gradient recalled echo images was significantly larger than that on spin-echo images, which was in accordance with previous findings (5,(15)(16)(17)(18)(19)(20)(21) This finding may be due to the fact that spin-echo sequences have a 180-degree pulse that refocuses the frequency shifts due to susceptibility in echo time (TE) and thus, eliminates pixel intensity shifts (22). Moreover, in gradient echo (GE) sequence, magnetic field slightly superimposes on the main field and thus, it is the most sensitive sequence to metals (23).…”

Influence of magnetic susceptibility and volume on MRI artifacts produced by low magnetic susceptibility Zr-14Nb alloy and dental alloys

“…However, our study is limited in that other factors, such as imaging conditions, shape, orientation, and position of the object, were not investigated. These factors also affect the artifact volume 9,17,18) and must be considered to predict it more accurately. Especially, previous studies have reported that artifacts appear larger under GRE than SE conditions.…”

“…In recent years, the field strengths used for MRI have increased rapidly, with 3 T now commonly being applied to examine various diseases instead of the more typical 1.5 T. Higher field strengths are advantageous because they provide a greater intrinsic signal-to-noise ratio (SNR). Moreover, it is expected that even higher field strengths will be used, as the SNR is predicted to grow at least linearly with the field strength [7][8][9] . For example, ultra-high-field (7 T or above) MRI scanners allow higher spatial resolution imaging in human applications, which is expected to contribute to the early detection of microstructural changes, clarification of mechanisms, and accurate identification of treatment results in numerous diseases such as epilepsy 10) , multiple sclerosis 11) , and Alzheimer's 12) .…”

Diffusion-weighted MRI for differentiation between sialadenitis and pleomorphic adenoma

“…All scans were acquired using the coronal orientation with a field of view of 40 3 40 3 40 cm 3 and a matrix of 160 3 160 pixels. Radiofrequency pulse and gradient modes were set to "fast", with a phase resolution of 100%.…”

“…1,2 The advent of MRI in dentistry has led to important advances in the field of oral diagnosis. 3,4 MRI provides multiplanar imaging with satisfactory soft-tissue contrast using non-ionizing electromagnetic fields. One of the MRI modalities is diffusion-weighted imaging (DWI), which takes into account water motion at the molecular level, within voxels of a tissue.…”