Analysis of angle compounding on a fast color Doppler imaging: Phantom study

Fast color Doppler imaging (CDI) based on plane wave excitation and angle compounding is useful for evaluating vascular diseases with high frame rates. Due to limited spatial resolution from plane wave excitation, the image quality of CDI is substantially degraded. To enhance the spatial resolution, angle compounding, in which several tiled plane waves are excited and coherently summed together during receive beamforming, can be used. However, the effect of angle compounding on fast CDI has not been extensively analyzed. In this paper, the analysis of angle compounding on fast CDI with phantom studies is presented. To evaluate the effect of the angle compounding, in this paper, a new color Doppler imaging technique based on sliding angle compounding (CDI-SAC) is adopted. In CDI-SAC, the angle compounding is updated as each new angle compounding is acquired so that there is no reduction in both Doppler pulse-repetition frequency (PRF) and frame rate. For that reason, the CDI-SAC method is used for the analysis of angle compounding on fast CDI. The PRF of 2 kHz and four different sets of compounding angles (i.e., 3, 6, 8 and 12) were used for generating a color Doppler image. The results of each angle compounding from CDI-SAC shows improved hemodynamic representation as the number of combined angle increases. The measured root mean square errors (RMSEs) for three angle sets (3, 6, and 8) by assuming the 12 angle set as the reference are 0.0124, 0.0107 and 0.0082, respectively. These results indicate that the proper selection of the number of angles in fast color Doppler imaging is important for improving spatial resolution while reducing the blocky artifacts.