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The Suppression of Selected Acoustic Noise Frequencies in MRI

Shou, Xingxian
http://rave.ohiolink.edu/etdc/view?acc_num=case1281404517

Abstract Details

2011, Doctor of Philosophy, Case Western Reserve University, Physics.
Problems due to Magnetic Resonance Imaging (MRI) acoustic noise have long been an important concern, both in research and clinical applications. A study is made of certain dominant frequencies in the acoustic noise spectrum of the MRI system. Motivated by both spring and string ideas, we investigate whether the contributions to the sound from certain frequencies can be cancelled by the appropriate the gradient pulse sequence design. Ideas for cancelling these frequencies are investigated by carrying out theoretical string calculations. The MRI gradient assembly is modeled as a string and the gradient pulse sequences as a driving force for that string. Analytical results are obtained with different input gradient pulses including boxcars, trapezoids, and multiple trapezoids, along with special “quadratic” pulses. Pulse trains composed of repetitions of these pulse structures are studied. For comparison and to test these ideas, both simulations and experiments are carried out to verify our analytical results for the cancellations of selected frequency peaks. The idea that vibrations resulting from an impulsive force associated with a ramping up of a gradient pulse are shown to be cancelled immediately upon the application of another impulsive force coming from the subsequent appropriately timed ramping down of that pulse is verified both by simulations and experiments. A general approach to suppression of multiple-frequency contributions involving a series of gradient pulses with variable timings is given for the cancellations between pairs of impulse forces. The various examples investigated with string analytics and simulations and the associated MRI experiments are a physical embodiments of general time-invariant linear response theory. The present study also provides a foundation to explain results in previous papers on this subject. The method suggests that a variety of pulse profiles and timing combinations can be used to attenuate important contributions to the acoustic output spectrum.
Robert Brown, PhD (Advisor)
Jeffrey Duerk, PhD (Committee Member)
David Farrell, PhD (Committee Member)
Harsh Mathur, PhD (Committee Member)
Shmaryu Shvartsman, PhD (Committee Member)
148 p.
Acoustics; Biomedical Research; Physics
Acoustic noise; MRI system; Vibrating string; Gradient pulse optimization

Recommended Citations

Citations

  • Shou, X. (2011). The Suppression of Selected Acoustic Noise Frequencies in MRI [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1281404517

    APA Style (7th edition)

  • Shou, Xingxian. The Suppression of Selected Acoustic Noise Frequencies in MRI. 2011. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1281404517.

    MLA Style (8th edition)

  • Shou, Xingxian. "The Suppression of Selected Acoustic Noise Frequencies in MRI." Doctoral dissertation, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1281404517

    Chicago Manual of Style (17th edition)

case1281404517
1,218
© 2010, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.