Document Detail

Acoustic pressure waves induced in human heads by RF pulses from high-field MRI scanners.
MedLine Citation:
PMID:  20220368     Owner:  NLM     Status:  MEDLINE    
The current evolution toward greater image resolution from magnetic resonance image (MRI) scanners has prompted the exploration of higher strength magnetic fields and use of higher levels of radio frequencies (RFs). Auditory perception of RF pulses by humans has been reported during MRI with head coils. It has shown that the mechanism of interaction for the auditory effect is caused by an RF pulse-induced thermoelastic pressure wave inside the head. We report a computational study of the intensity and frequency of thermoelastic pressure waves generated by RF pulses in the human head inside high-field MRI and clinical scanners. The U.S. Food and Drug Administration (U.S. FDA) guides limit the local specific absorption rate (SAR) in the body-including the head-to 8 W kg(-1). We present results as functions of SAR and show that for a given SAR the peak acoustic pressures generated in the anatomic head model were essentially the same at 64, 300, and 400 MHz (1.5, 7.0, and 9.4 T). Pressures generated in the anatomic head are comparable to the threshold pressure of 20 mPa for sound perception by humans at the cochlea for 4 W kg(-1). Moreover, results indicate that the peak acoustic pressure in the brain is only 2 to 3 times the auditory threshold at the U.S. FDA guideline of 8 W kg(-1). Even at a high SAR of 20 W kg(-1), where the acoustic pressure in the brain could be more than 7 times the auditory threshold, the sound pressure levels would not be more than 17 db above threshold of perception at the cochlea.
James C Lin; Zhangwei Wang
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Health physics     Volume:  98     ISSN:  1538-5159     ISO Abbreviation:  Health Phys     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-03-11     Completed Date:  2010-04-05     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985093R     Medline TA:  Health Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  603-13     Citation Subset:  IM    
Department of Electrical and Computer Engineering, University of Illinois at Chicago, 851 S. Morgan Street (M/C 154), Chicago, IL 60607-7053, USA.
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MeSH Terms
Electromagnetic Fields
Equipment Safety / standards
Head / anatomy & histology,  radiation effects*,  radiography
Magnetic Resonance Imaging / adverse effects*,  instrumentation,  methods*,  standards
Practice Guidelines as Topic
Radiation Dosage
Radiation Injuries* / prevention & control,  radiography
Radio Waves*
Radiographic Image Interpretation, Computer-Assisted / instrumentation,  methods*,  standards
United States
United States Food and Drug Administration

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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