Parameters Optimization of Ultrasound Contrast Agent Harmonic Imaging with Chirp Excitation

A vascular perfusion ultrasound contrast agent (UCA) imaging method is investigated, in which chirp excitation is introduced to increase signal to noise ratio (SNR) and contrast to tissue ratio (CTR). A calculation about the chirp transmitting parameters, a simulation for UCA harmonic imaging and an ultrasound experiment are carried out. The parameters of UCA harmonic imaging with chirp excitation are optimized. The UCA second harmonic images are gained. The results show that: the transmitted chirp with cosine envelope is slightly better than that with other envelope; the suitable ultrasound pressure for chirp excitation UCA harmonic imaging is about 150 kPa; the chirp signal with 67% frequency-modulated (FM) bandwidth can get a good imaging resolution and decrease the interaction between fundamental component and harmonic component. The SNR and CTR of harmonic image formed with chirp excitation get 6.4 dB and 10 dB higher than that of formed with conventional pulse excitation respectively.