Author details

accumulations and the predicted Q<sup>F</sup> value. Also, in this case, the increase of Q<sup>F</sup> is more distinctive for the SE sequences. Values in Table 4 describe the influence of TR and NACC values on the final time duration of the executed scan sequence. While the increased TR causes only moderately greater overall time duration, the changed NACC parameter has comparably higher influence on the final time duration. This effect is also shown in a detailed comparison of numerical results for different NACC values in Table 5. For the "Hi-Res" sequence types, the increase of the parameter NACC from 2 to 16 results in about 2.8 times greater value of Q<sup>F</sup> but 6 times greater than that of TDUR. For the "3D" sequence types, the increase of the resulting time duration is also affected by the choice of the number of 3D phases (equivalent to the number of slices with selection of the slice thickness for the "Hi-Res" sequences) in

Acoustic noise measurement in the vicinity of the investigated open-air MRI device yielded the maximum sound pressure level of about 82 dB(C) at the distance of 45 cm from the central point of the MRI scanning area for the GE scan sequence with short TE and TR times and the sagittal orientation of scan slices. For examination of other parts of the human body (leg, arm, etc.), the head is not inserted directly between the upper and the lower gradient coils, so the noise level is much lower as documented for different distances in Figure 10. Finally, the scanning times for the mostly used 3D or Hi-Res sequences are in general less than 15 minutes (typically about 3–5 minutes depending on the chosen number and thickness of the slices)—exposition of the examined person and his/her hearing system to the noise

If there is need for more detailed MR images with higher quality factor Q<sup>F</sup> (e.g., in scanning of particular parts of the human brain, the eye, the middle and inner ear, etc.), the time duration TDUR can be much longer (more than half an hour). In such a case, the long exposition to the vibration and acoustic noise may impose great physiological and psychological stress on the patient. Therefore, these scan

The results of the performed measurements are useful for precise description of the process of the mechanical vibration excitation and the acoustic noise radiation in the scanning area and in the vicinity of the MRI device. The measurement results and comparisons with a similar low-field MRI tomograph can be used in optimization of the acoustic noise suppression in the speech recorded parallel with applica-

This work was funded by the Slovak Scientific Grant Agency project VEGA 2/ 0001/17 and the Ministry of Education, Science, Research, and Sports of the Slovak Republic VEGA 1/0905/17, and the Slovak Research and Development Agency,

parallel as shown in Tables 6 and 7.

Noise and Vibration Control - From Theory to Practice

and vibration is not significant.

Acknowledgements

project no. APVV-15-0029.

Conflict of interest

114

parameters should be chosen only in the urgent cases.

The authors declare no conflict of interest.

tion of MRI scanning for 3D modeling of the human vocal tract [19].

5. Conclusions

Jiří Přibil1 \*, Anna Přibilová<sup>2</sup> and Ivan Frollo<sup>1</sup>

1 Institute of Measurement Science, SAS, Bratislava, Slovak Republic

2 Institute of Electronics and Photonics, Faculty of Electrical Engineering and Information Technology, SUT, Bratislava, Slovak Republic

\*Address all correspondence to: umerprib@savba.sk

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
