High frame rate color Doppler echocardiography: a quantitative comparison of different approaches.

Ultrasound color Doppler imaging (CDI) provides a map of the axial blood flow velocities in a 2D/3D region of interest. While CDI is clinically effective for a qualitative analysis of abnormal blood flows, e.g. for valvular disease in cardiology, it is in limited use for quantitative measures, mainly hampered by low frame rate and measurement bias. These limitations can be reduced by different approaches towards high frame rate (HFR) imaging at the expense of reduced image quality and penetration depth. The aim of this study was to quantitatively compare the impact of different HFR sequences on CDI. Different cardiac scan sequences, including diverging waves and multi-line transmission, were designed, implemented on a research system, and compared in terms of patient safety parameters, image quality, and penetration depth. Further, in-vivo images were acquired and compared for healthy volunteers. Results showed that HFR techniques spread artifacts on larger areas compared to standard single line scans (> +50%). Also, due to patient safety limitations, they reduce the penetration depth up to -5 cm. On the other hand, HFR techniques provide comparable velocity estimates (relative difference < 6%) and enhance the time resolution of color Doppler images, achieving frame rates up to 625 Hz in continuous acquisition.