European Radiology

, Volume 27, Issue 12, pp 5104–5112 | Cite as

PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging

  • Tim HilgenfeldEmail author
  • Marcel Prager
  • Alexander Heil
  • Franz Sebastian Schwindling
  • Mathias Nittka
  • David Grodzki
  • Peter Rammelsberg
  • Martin Bendszus
  • Sabine Heiland
Head and Neck



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.

Key Points

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


Magnetic 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


Radio frequency


Region of interest


Slice-encoding for metal artefact correction


Signal-to-noise ratio


Sampling perfection with application-optimised contrasts using different flip angle evolution


Turbo-spin-echo sequence


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

Informed consent was not required since no living animals were studied.

Ethical approval

Institutional review board approval was not required since no living animals were studied.


• Prospective

• experimental

• performed at one institution


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Copyright information

© European Society of Radiology 2017

Authors and Affiliations

  • Tim Hilgenfeld
    • 1
    Email author
  • Marcel Prager
    • 1
    • 2
  • Alexander Heil
    • 1
  • Franz Sebastian Schwindling
    • 3
  • Mathias Nittka
    • 4
  • David Grodzki
    • 4
  • Peter Rammelsberg
    • 3
  • Martin Bendszus
    • 1
  • Sabine Heiland
    • 1
    • 2
  1. 1.Department of NeuroradiologyHeidelberg University HospitalHeidelbergGermany
  2. 2.Section of Experimental RadiologyHeidelberg University HospitalHeidelbergGermany
  3. 3.Department of ProsthodonticsHeidelberg University HospitalHeidelbergGermany
  4. 4.Siemens Healthcare GmbHErlangenGermany

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