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The influence of acoustic transmit parameters on the destruction of contrast microbubbles in vitro

William T Shi1,3, Flemming Forsberg1, Priya Vaidyanathan1,4, Audun Tornes2, Jonny Østensen2 and Barry B Goldberg1

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In this study, the destruction of the contrast agent Sonazoid (GE Healthcare, Oslo, Norway) was measured in vitro as a function of centre frequency (2–3 MHz), acoustic amplitude (0.66–1.6 MPa), pulse length (2–16 cycles) and PRF (0.5–8.0 kHz). Up to 82% of microbubbles were destroyed after exposure to a single 1.6 MPa acoustic pulse (16 cycles, 2.5 MHz and PRF of 1.0 kHz), while at a low amplitude of 0.66 MPa, fractional destruction increased gradually from 0 to 40% after exposure to 9 (identical) pulses. Fractional destruction increased from approximately 8 to 66% as pulse length was changed from 2 to 16 cycles following exposure to a single 2.5 MHz, 1.3 MPa pulse. As the PRF was increased from 0.5 to 8.0 kHz, shorter exposure time intervals (from 4.8 to 1.2 ms) were needed to achieve the same fractional destruction of 80%. Conversely, as the transmit frequency was increased from 2 to 3 MHz the fractional destruction decreased (by more than half within the first 3 pulses). The influence of changes in acoustic pressure and duty cycle on the destruction of Sonazoid microbubbles was highly statistically significant (p ≤ 0.01) with a threshold around 0.67 MPa for a duty cycle of 0.0064. In conclusion, the fractional destruction increases with the duty cycle and the acoustic pressure amplitude and decreases with ultrasonic transmit frequency. Better understanding of the influence of the ultrasound transmit parameters on the destruction of contrast microbubbles should help improve existing contrast-assisted imaging modalities and may help develop new techniques for better use of contrast agents.


PACS

87.63.D- Ultrasonography

43.80.Qf Medical diagnosis with acoustics (in PACS, see also 87.63.D−)

43.80.Vj Acoustical medical instrumentation and measurement techniques

43.35.Wa Biological effects of ultrasound, ultrasonic tomography

Subjects

Biological physics

Medical physics

Dates

Issue 16 (21 August 2006)

Received 1 March 2006, in final form 15 June 2006

Published 2 August 2006



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