Mapping of noise and vibrations in the environment of NMR tomographs with a weak magnetic field

(Investigators: J. Přibil, I. Frollo, D. Gogola, T. Dermek)


During scanning in a magnetic resonance (NMR) tomograph, mechanical vibrations occur due to the function of the coils of the gradient system and acoustic noise is subsequently generated. This is a source of interference, especially in 3-D imaging – an increase in background noise and a decrease in image sharpness. The imaging procedure of the human vocal tract was tested, in which the speech signal is also scanned during phonation in an NMR tomograph. Mapping of the distribution of noise intensity and mechanical vibrations in the scanning space of NMR tomographs with weak magnetic field up to 0.2 T (open E-scan OPERA and whole-body TMR96), including selection of suitable position, distance and directional characteristic of acoustic signal sensor and assessment of metal influence shielding cage for the reflected acoustic noise wave. The results of the analysis of the spectral properties of vibrations will be used to suppress unwanted acoustic signals as well as artifacts in MR images of thin films and material samples. The acquired knowledge will further serve to develop new experimental coils and special test phantoms for mapping homogeneity, intensity distribution and other properties of weakly magnetic materials.

Fig. 1: General view of an open NMR tomograph E-scan OPERA in a shielded metal cage (a), lying person during the experiment of parallel recording of speech signal and MR scan of voice tract (b), obtained MR image together with visualization of speech signal (c).

 

Related projects:
• VEGA 2/0001/17 – Measurement and imaging methods based on magnetic resonance for materials and biomedical research.
• APVV-15-0029 – Research of comparative magnetic resonance imaging methods for the diagnosis of neurological and musculoskeletal diseases

 

Publications:

  1. PŘIBIL, J. – PŘIBILOVÁ, A. – FROLLO, I. Analysis of acoustic noise and its suppression in speech recorded during scanning in the open-air MRI. In Advances in Noise Analysis, Mitigation and Control. In Editor Noor Ahmed. – InTech, 2016. ISBN 978-953-51-4762-6, p. 205-228.
  2. PŘIBIL, J. – PŘIBILOVÁ, A. – FROLLO, I. Comparison of mechanical vibration and acoustic noise in the open-air MRI. In Applied Acoustics, 2016, vol. 105, p. 13-23. ISSN 0003-682X. (1.462-IF2015)
  3. PŘIBIL, J. – PŘIBILOVÁ, A. – FROLLO, I. Two methods of automatic evaluation of speech signal enhancement recorded in the open-air MRI environment. In Measurement Science Review, 2017, vol. 17, no. 6, p. 257-263. ISSN 1335-8871. (1.344-IF2016)
  4. PŘIBIL, J. – GOGOLA, D. – DERMEK, T. – FROLLO, I. Automatic evaluation of noise suppression in speech signal recorded during phonation in the open-air MRI. In MEASUREMENT 2017: Proceedings of the 11th International Conference on Measurement. Editors: J. Maňka, M. Tyšler, V. Witkovský, I. Frollo. – Bratislava, Slovakia: Institute of Measurement Science, Slovak Academy of Sciences, 2017, 205-208. ISBN 978-80-972629-0-7.
  5. PŘIBIL, J. – PŘIBILOVÁ, A. – FROLLO, I. Automatic GMM-based evaluation of noise suppression in the speech signal recorded during phonation in the open-air MRI. In 40th International Conference on Telecommunications and Signal Processing, TSP 2017. Editor: Herencsar, N. – Brno, Czech Republic: Faculty of Electrical Engineering and Communication, Brno University of Technology, 2017, p. 350-353. ISBN 978-1-5090-3982-1.
  6. PŘIBIL, J. – PŘIBILOVÁ, A. – GOGOLA, D. – FROLLO, I. Measurement of noise and vibration produced by the whole-body magnetic resonance imager working with a weak magnetic field. In Noise and Vibration in Practice: Peer-reviewed Scientific Proceedings. Editor: S. Žiaran; Reviewers: Ľ. Argalášová, M. Balážiková, P. Beneš et al. Bratislava, Slovak Republic: Slovak University of Technology, 2017, Vol. 22, p. 65-70. ISBN 978-80-227-4696-0.