title: The response of phospholipid-encapsulated microbubbles to chirp-coded excitation: implications for high-frequency nonlinear imaging.
abstract: The current excitation strategy for harmonic and subharmonic imaging (HI and SHI) uses short sine-bursts. However, alternate pulsing strategies may be useful for enhancing nonlinear emissions from ultrasound contrast agents. The goal of this study was to corroborate the hypothesis that chirp-coded excitation can improve the performance of high-frequency HI and SHI. A secondary goal was to understand the mechanisms that govern the response of ultrasound contrast agents to chirp-coded and sine-burst excitation schemes. Numerical simulations and acoustic measurements were conducted to evaluate the response of a commercial contrast agent (Targestar-P(®)) to chirp-coded and sine-burst excitation (10 MHz frequency, peak pressures 290 kPa). The results of the acoustic measurements revealed an improvement in signal-to-noise ratio by 4 to 14 dB, and a two- to threefold reduction in the subharmonic threshold with chirp-coded excitation. Simulations conducted with the Marmottant model suggest that an increase in expansion-dominated radial excursion of microbubbles was the mechanism responsible for the stronger nonlinear response. Additionally, chirp-coded excitation detected the nonlinear response for a wider range of agent concentrations than sine-bursts. Therefore, chirp-coded excitation could be a viable approach for enhancing the performance of HI and SHI.
authors: Department of Electrical and Computer Engineering, University of Rochester, Rochester New York 14627, USA.
authors: Himanshu
authors: H
authors: Shekhar
authors: Marvin M
authors: MM
authors: Doyley
mesh_terms: D000162:Acoustics; D003198:Computer Simulation; D003287:Contrast Media; D045423:Microbubbles; D017711:Nonlinear Dynamics; D009716:Numerical Analysis, Computer-Assisted; D010743:Phospholipids; D011312:Pressure; D059629:Signal-To-Noise Ratio; D013018:Sound Spectrography; D013500:Surface Tension; D014465:Ultrasonics / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D010743:Phospholipids
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