Color amplitude imaging: preliminary results using vascular sonographic contrast agents.

Conventional (mean Doppler frequency shift) color Doppler imaging and a new method of displaying blood flow in color that uses the amplitude of the Doppler signal were utilized to evaluate three vascular sonographic contrast agents. To compare the two color flow detection modalities, a total of 20 pairs of contrast agent injections were performed while imaging a variety of abdominal organs and tumors in experimental animal models. The 20 paired injections were scored independently to indicate whether color amplitude imaging better demonstrated the effects of contrast enhancement (n = 14), both techniques were equivalent in demonstrating the effects of contrast enhancement (n = 4), or color Doppler imaging better demonstrated the effects of contrast enhancement (n = 2). These results indicate that compared to color Doppler imaging, color amplitude imaging improved visualization of both normal and abnormal blood flow in 70% of these cases (P < 0.0001). Specifically, with contrast enhancement of the Doppler signals, organ vascularity and regional differences in parenchymal blood flow were better demonstrated with color amplitude imaging than with color Doppler imaging. In addition, since color amplitude imaging is nondirectional and less angle dependent than color Doppler imaging, it was possible to visualize vessel continuity more completely and to demonstrate vessel branching more clearly with this modality. However, owing to the lack of directivity and poor temporal resolution, information obtained with color amplitude imaging appears to be complementary to that of color Doppler imaging. In conclusion, color amplitude imaging is a reliable method of determining the effectiveness of vascular sonographic contrast agents and should be considered one of the primary flow imaging modalities used for the assessment of these agents.