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Magn Reson Med. 2017 Jan;77(1):102-111. doi: 10.1002/mrm.26082. Epub 2015 Dec 30.

Real-time monitoring of inertial cavitation effects of microbubbles by using MRI: In vitro experiments.

Author information

1
Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.
2
Department of Electrical Engineering, Chang Gung University, Taoyuan, Taiwan.
3
Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
4
Division of Medical Engineering Research, National Health Research Institutes, Miaoli, Taiwan.

Abstract

PURPOSE:

To investigate the feasibility of half-Fourier acquisition single-shot turbo spin-echo (HASTE) for real-time monitoring of signal changes because of water flow induced by inertial cavitation (IC) during microbubbles (MBs)-present focused ultrasound (FUS) exposure.

THEORY AND METHODS:

Strong turbulence produced in MB solution at the onset of IC results in the difficulty to refocus signal echoes and thus the decrease in signal intensity (SI). Fundamental investigations were conducted using an agar phantom containing MB dilutions exposed to 1.85-MHz FUS. The effects of various experimental conditions including MB concentrations, imaging slice thicknesses, chamber diameters, acoustic pressures, duty cycles, and pulse repetition frequencies (PRFs) were discussed.

RESULTS:

Continuous 2.8 MPa FUS exposure resulted in SI changed from 11% to 55% when MBs concentrations increased from 0.025% to 0.1%. When slice thickness increased from 3 mm to 6 or 8 mm, smaller SI changes were observed (84%, 59%, and 46%). Images acquired with chamber diameter of 6 and 3 mm showed SI changes of 84% and 35%, respectively. In burst modes, higher duty cycles exhibited higher SI changes, and lower PRFs exhibited smaller and longer SI decrease.

CONCLUSION:

Under various conditions, substantial signal changes were observable, suggesting the feasibility of applying HASTE to real-time monitor IC effect under FUS exposure. Magn Reson Med 77:102-111, 2017. © 2015 Wiley Periodicals, Inc.

KEYWORDS:

focused ultrasound; half-Fourier acquisition single-shot turbo spin-echo (HASTE); inertial cavitation; microbubble; real-time monitoring

PMID:
26714923
DOI:
10.1002/mrm.26082
[Indexed for MEDLINE]

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