PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging
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Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time.
Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence. Field-of-view and acquisition times were chosen to enable in vivo application. Two implant-supported prostheses were tested (porcelain fused to metal non-precious alloy and monolithic zirconia).
Smallest artefact was measured for TSE sequences with no difference between the standard TSE and the SEMAC. MSVAT-SPACE reduced artefacts about 56% compared to the standard SPACE. Effect of the PETRA was dependent on sample used. Image quality and SNR were comparable for all sequences except PETRA, which yielded poor results.
There is no benefit in terms of artefact reduction for SEMAC compared to standard TSE. Usage of MSVAT-SPACE is advantageous since artefacts are reduced and higher resolution is achieved.
• SEMAC is not superior to TSE in terms of artefact reduction.
• MSVAT-SPACE reduces susceptibility artefacts while maintaining comparable image quality.
• PETRA reduces susceptibility artefacts depending on material but offers poor image quality
KeywordsMagnetic resonance imaging Artefacts Teeth Dental implants Metals
Cone beam computed tomography
Multi-detector computed tomography
Multiple-slab acquisition with VAT gradient, based on a SPACE sequence
Pointwise encoding time reduction with radial acquisition
Region of interest
Slice-encoding for metal artefact correction
Sampling perfection with application-optimised contrasts using different flip angle evolution
Ultrashort time of echo sequence
View angle tilting
Work in progress
TH receives funding from a postdoctoral fellowship of the Medical Faculty of the University of Heidelberg. The authors would like to thank Stefanie Sauer, PhD, a pharmacist at the Department of Pharmacy, Heidelberg University Hospital, for her contribution to the MRI phantom. Furthermore, we would like to thank NORAS MRI products GmbH, especially Daniel Gareis, MSc, for providing a prototype of the 16-channel multipurpose coil.
Compliance with ethical standards
The scientific guarantor of this publication is Dr. rer. nat. Sabine Heiland.
Conflict of interest
The authors of this manuscript declare relationships with the following companies: Siemens Healthcare GmbH and NORAS MRI products GmbH. The co-authors M.Nittka, PhD, and D.Grodzki, PhD, are employees of Siemens Healthcare GmbH and were involved in the technical development of the metal-artefact-reducing pulse sequences.
The study was supported in part by the Dietmar-Hopp-Stiftung (project no 23011228).
Statistics and biometry
No complex statistical methods were necessary for this paper.
Informed consent was not required since no living animals were studied.
Institutional review board approval was not required since no living animals were studied.
• performed at one institution
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