Low-Intensity Focused Ultrasound Pulsation Device Used During Magnetic Resonance Imaging: Evaluation of Magnetic Resonance Imaging-Related Heating at 3 Tesla/128 MHz

Authors

  • Alexander S. Korb PhD,

    Corresponding author
    1. Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
    • Address correspondence to: Alexander S. Korb, PhD, University of California, 300 UCLA Medical Plaza, 2335, Los Angeles, CA 90095, USA. Email: alexkorb@ucla.edu

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  • Frank G. Shellock PhD,

    1. Department of Radiology, University of Southern California, Los Angeles, CA, USA
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  • Mark S. Cohen PhD,

    1. Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
    2. Departments of Neurology, Radiology, Psychology, Biomedical Physics, and Bioengineering, University of California, Los Angeles, CA, USA
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  • Alexander Bystritsky MD, PhD

    1. Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA, USA
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  • [Correction added after online publication 5-June 2013. In Materials and Methods section, linear radiofrequency amplifier corrected from model 403LA to 240L.]
  • For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http://www.wiley.com/bw/submit.asp?ref=1094-7159&site=1
  • Support: Support for this study came from Brainsonix, Inc. and the Gerald J. and Dorothy R. Friedman New York Foundation for Medical Research. Dr. Bystritsky provided the LIFUP device, courtesy of Brainsonix, Inc.
  • Conflict of Interest: Dr. Bystritsky is the founder of Brainsonix, Inc. Drs. Korb, Shellock, and Cohen report no conflicts of interest.

Abstract

Objective

The objective of this study was to determine magnetic resonance imaging (MRI)-related heating for a low-intensity focused ultrasound pulsation (LIFUP) device used during MRI performed at 3 T/128 MHz.

Materials and Methods

A special phantom was constructed to mimic the thermal properties of the human brain, and a piece of human temporal bone (skull) was embedded on top. Four fluoroptic thermometry probes, placed above and below the skull, were used to measure temperature changes during MRI (3 T/128 MHz; scanner-reported head average specific absorption rate 1.1–2 W/kg) with and without concurrent LIFUP sonication. LIFUP sonication was applied using a focused ultrasound device (BXPulsar 1001, Brainsonix, Inc., Los Angeles, CA, USA) at a derated spatial-peak temporal-average intensity of 3870 mW/cm2.

Results

MRI performed at relatively high specific absorption rate (SAR) caused a slight elevation in temperature (≤0.6°C). Concurrent use of MRI at a medium-strength SAR and LIFUP sonication resulted in maximum temperature rise of 3.1°C after 8 min of continuous use.

Conclusions

Under the specific conditions utilized for this investigation, LIFUP sonication does not appear to present significant heating risks when used concurrently with MRI. This information has important implications for the use of the LIFUP sonication in human subjects undergoing MRI at 3 T/128 MHz.

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