QUANTITATIVE MEASUREMENTS OF 2ND-HARMONIC DOPPLER USING ULTRASOUND CONTRAST AGENTS

Quantitative measurements of second harmonic and first harmonic Dopple r were carried out using two ultrasound contrast agents, Albunex(R) an d FS069. The RMS amplitudes of the Doppler shift spectra were measured as a function of the concentration of the agents, frequency and trans mitted acoustic pressure. The results showed that, for a given lot of contrast agent investigated, FS069 was able to produce higher levels o f first and, especially, second harmonic signals compared to Albunex, Under the same experimental conditions, the RMS Doppler amplitude (RDA ) of FS069 was 3.8 +/- 0.8 dB higher than Albunex at first harmonic an d 12.6 +/- 0.8 dB higher at second harmonic. The ratio of the second h armonic to first harmonic RDA, which we called R(2)/R(1), decreases at a rate of 7 dB/MHz for both agents with increasing frequency. The dif ference in the value of R(2)/R(1) between FS069 and Albunex at any fre quency was approximately 4.5 dB, R(2)/R(1) was found to increase linea rly as a function of the transmitted acoustic pressure for both agents . Simulations using the Rayleigh-Plesset equation show a decrease of R (2)/R(1) at a rate of 5 dB/MHz. Comparison of experimental results wit h theory indicates that the shell elasticity parameter may be an incre asing function of the mean diameter of the bubbles. Copyright (C) 1996 World Federation for Ultrasound in Medicine and Biology.