0
Research Papers

Mapping and Spectral Analysis of Acoustic Vibration in the Scanning Area of the Weak Field Magnetic Resonance Imager

[+] Author and Article Information
Jiří Přibil

Institute of Measurement Science,
Slovak Academy of Sciences,
Dúbravská cesta 9,
Bratislava SK-841 04, Slovakia
e-mail: jiri.pribil@savba.sk

Anna Přibilová

Institute of Electronics and Photonics,
Faculty of Electrical Engineering
and Information Technology,
SUT, Ilkovičova 3,
Bratislava SK-812 19, Slovakia

Ivan Frollo

Institute of Measurement Science,
Slovak Academy of Sciences,
Dúbravská cesta 9,
Bratislava SK-841 04, Slovakia

1Corresponding author.

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received September 30, 2013; final manuscript received May 16, 2014; published online July 25, 2014. Assoc. Editor: Thomas J. Royston.

J. Vib. Acoust 136(5), 051005 (Jul 25, 2014) (10 pages) Paper No: VIB-13-1336; doi: 10.1115/1.4027791 History: Received September 30, 2013; Revised May 16, 2014

The paper describes measurement and calculation of 2D distribution of the vibration signal originated by the gradient coil system of the magnetic resonance imaging (MRI) equipment. The measurement experiments were performed at the bottom plastic holder of the scanning area of the open-air weak magnetic field MRI device. Selection of a usable type of a vibration sensor for measurement in a magnetic field with low B0 up to 0.2 T is also discussed. Realized calibration of the chosen sensor (sensitivity and frequency response) together with determination of the propagation time delay between the excitation impulses and the subsequently generated vibration signal is mentioned, too. The picked-up vibration signal exhibits harmonic character so it is suitable to describe it by determined spectral properties and features. Obtained statistical results of spectral analysis will be used to improve image sharpening and reduction of the motion effect in the MR pictures of thin layer samples and phantoms scanned by this MRI system.

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Scanning space of MRI: (1)—RF knee coil with testing phantom, (2) and (3)—lower and upper permanent magnets and gradient coils

Grahic Jump Location
Fig. 2

Arrangement of sensors on vibration exciter for calibration experiment: (1) and (2)—reference accelerometers KD35a, KD12, (3)—tested vibration sensor SB-1

Grahic Jump Location
Fig. 3

Relative sensitivity of the sensors at fref = 125 Hz; UexcBa0 = 360 mV; Ba0 = {12.9 (SB-1), 4.99 (KD35a), 4.22 (KD12)} mV/ms−2

Grahic Jump Location
Fig. 4

Frequency responses: acceleration sensitivity for SB-1, KD35a, KD12 (a), velocity sensitivity for SB-1 (b); fref = 125 Hz; U excBa0 = 360 mV

Grahic Jump Location
Fig. 6

Arrangement of propagation time delay measurement: RF coil with water phantom (1), SB-1 sensor (2), and experimental coil for pick-up of electrical excitation pulses (3)

Grahic Jump Location
Fig. 7

Distribution of the relative vibration level in (dB): at basic positions 0–18 in 15 × 9 grid with 2D contour map (upper), at extended positions 0–50 with 2D contour map (lower); sequence No. 1

Grahic Jump Location
Fig. 8

Distribution of the relative vibration level in (dB) at positions 0–18 (upper), 2D contour maps (lower); sequences: No. 2. (a), No. 4 (b), and No. 8 (c)

Grahic Jump Location
Fig. 9

Distribution of the excitation signal in (mV): at basic positions 0–18 in 15 × 9 grid with 2D contour map (upper), at extended positions 0–50 with 2D contour map (lower); sequence No. 1

Grahic Jump Location
Fig. 10

Mean values of time delay between electric excitation and vibration signal: from positive part of signal (a), from negative part of signal (b) at positions P0, P1, and P4

Grahic Jump Location
Fig. 11

Mean values of spectral features HNR (a), SFM (b), SC (c), and SE (d) at positions P0, P1, and P4

Grahic Jump Location
Fig. 12

Basic statistical properties of spectral features: HNR (a), SFM (b), SC (c), and SE (d) at position P0

Grahic Jump Location
Fig. 13

Typical waveforms of excitation signals for sequences Nos. 1–8 ((a)–(h)) at position P0, fs = 16 kHz

Grahic Jump Location
Fig. 14

Typical waveforms of vibration signals for sequences Nos. 1–8 ((a)–(h)) at position P0, fs = 16 kHz

Grahic Jump Location
Fig. 15

Spectrograms of vibration signals for sequences Nos. 1–8 ((a)–(h)) at position P0, fs = 16 kHz

Grahic Jump Location
Fig. 16

Periodograms and spectral envelopes of vibration signals for sequences Nos. 1–8 ((a)–(h)) at position P0, fs = 16 kHz

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In