To investigate the influence of dose, mechanical index (MI), and imaging techniques on contrast-enhanced ultrasound (CEUS) with Sonazoid^®.

In vitro models were prepared utilizing medical ultrasonic couplants and latex hoses. Sonazoid^® was diluted and prepared. In each dose group (0.1 ml/L, 0.15 ml/L, and 0.2 ml/L), Sonazoid^® (24 ml) was injected slowly and uniformly into the tube at 9 MI values (0.16, 0.19, 0.22, 0.25, 0.27, 0.33, 0.4, 0.5, and 0.7) using different imaging techniques [power modulation imaging (Gen) and pulse inversion imaging (Hres1)]. The probe was fixed to the maximum long-axis section of the latex hose for scanning. Quantitative analysis was performed using time-intensity curves to assess the enhancement, attenuation, and sustained enhancement time of microbubbles in the tube under different doses, MI values, and imaging techniques.

The enhancement in the 0.15 ml/Lgroup was higher than that of the 0.1 ml/L group [(31.0±5.0) dB vs (28.7±5.0) dB, P<0.001], but there was no significant difference in attenuation between them [1.0 (0.3, 1.8) dB vs 0.6 (0.2, 1.4) dB, P=0.064]. The enhancement and attenuation of Hres1 were higher than those of Gen [(33.4±5.4) dB vs (28.9±4.5) dB, P<0.001; 1.0 (0.4, 2.1) dB vs 0.8(0.3, 1.7) dB, P=0.027], and the sustained enhancement time of microbubbles was shorter [(6.9±1.8) s vs (7.5±2.5) s, P=0.003]. The balance between the enhancement and sustained enhancement time of microbubbles was obtained at MI=0.25 in Hres1 and MI=0.22 in Gen, respectively.

The clinical application of CEUS with Sonazoid^® should consider the influence of dose, MI, and imaging technique, in order to achieve ideal imaging effects.