Modeling the nonlinear microbubble response to coded, multi-pulse sequences

TY - CHAP

T1 - Modeling the nonlinear microbubble response to coded, multi-pulse sequences

AU - Chetty, K

AU - Eckersley, RJ

PY - 2005

Y1 - 2005

N2 - In this study a modified Rayleigh-Plesset model was used to examine the nonlinear acoustic response of ultrasound (US) contrast microbubbles to multi-pulse phase and amplitude modulated, chirp encoded sequences. Tradeoffs between the signal-to-noise ratio (SNR) and axial resolution were quantified for differing chirp time-bandwidth products and methods for minimising the artefacts formed in the post processing stages were also investigated. Results from the simulated chirp, pulse inverted, amplitude modulated (Chirp PIAM) sequences were compared to equivalent short pulse PIAM sequences of equal bandwidth and excitation amplitude. It was found that the chirp length can be increased and bandwidth reduced to improve SNR but resolution must be sacrificed for this benefit. The sidelobes were minimised by using chirps with a centre frequency and bandwidth tuned to the microbubble's resonant frequency and frequency response respectively. Furthermore, alternating the frequency sweep direction of one chirp in the sequence and using an optimum insonation pressure was also found to reduce the sidelobe artefacts. Over the pressure ranges simulated (25-200 kPa peak negative pressure), comparisons to the short pulse PIAM sequence showed that the chirp sequences preserve their extra energy after scattering which translates to an improved SNR after processing, with best improvement at the highest pressures; SNR = 27.7 +/- 3 compared to 19.0 2 for PIAM. The resolution of the Chirp PIAM sequence improves with increasing insonation pressures though it is always worse than short pulse PIAM which is independent of the driving pressure. The FWHM of the measured data was found to increase from the ideal case of 1.5 mu s to 1.9 +/- 0.2 mu s for PIAM and 2.4 +/- 0.3 mu s for Chirp PIAM.

AB - In this study a modified Rayleigh-Plesset model was used to examine the nonlinear acoustic response of ultrasound (US) contrast microbubbles to multi-pulse phase and amplitude modulated, chirp encoded sequences. Tradeoffs between the signal-to-noise ratio (SNR) and axial resolution were quantified for differing chirp time-bandwidth products and methods for minimising the artefacts formed in the post processing stages were also investigated. Results from the simulated chirp, pulse inverted, amplitude modulated (Chirp PIAM) sequences were compared to equivalent short pulse PIAM sequences of equal bandwidth and excitation amplitude. It was found that the chirp length can be increased and bandwidth reduced to improve SNR but resolution must be sacrificed for this benefit. The sidelobes were minimised by using chirps with a centre frequency and bandwidth tuned to the microbubble's resonant frequency and frequency response respectively. Furthermore, alternating the frequency sweep direction of one chirp in the sequence and using an optimum insonation pressure was also found to reduce the sidelobe artefacts. Over the pressure ranges simulated (25-200 kPa peak negative pressure), comparisons to the short pulse PIAM sequence showed that the chirp sequences preserve their extra energy after scattering which translates to an improved SNR after processing, with best improvement at the highest pressures; SNR = 27.7 +/- 3 compared to 19.0 2 for PIAM. The resolution of the Chirp PIAM sequence improves with increasing insonation pressures though it is always worse than short pulse PIAM which is independent of the driving pressure. The FWHM of the measured data was found to increase from the ideal case of 1.5 mu s to 1.9 +/- 0.2 mu s for PIAM and 2.4 +/- 0.3 mu s for Chirp PIAM.

KW - ultrasound

KW - contrast microbubbles

KW - multi-pulse sequences

KW - coded excitation

KW - chirp

KW - MEDICAL ULTRASOUND

M3 - Conference paper

SN - 0-7803-9382-1

T3 - ULTRASONICS SYMPOSIUM

SP - 2007

EP - 2010

BT - 2005 IEEE Ultrasonics Symposium, Vols 1-4

PB - IEEE

CY - NEW YORK

T2 - IEEE International Ultrasonics Symposium

Y2 - 18 September 2005 through 21 September 2005

ER -