Blood flow recordings made by 2 dimensional Doppler echocardiography can sometimes be understood more easily than conventional Doppler recordings, because of the anatomical 2 dimensional presentation. In contrast, signal processing has become more complicated and requires more explanation. In 2 dimensional Doppler echocardiography the analog ultrasonic signal received by the transducer is converted into an audible signal, which next is digitized and analyzed for its mean frequency and variance. Data collection and processing require application of multigating and high speed frequency analysis, generally based upon autocorrelation. Some artifacts may be perceived, such as color reversal due to aliasing, deceptively colored tissue surfaces due to beam motion, and wall motion ghost signals due to multiple reflections. Color flow imaging is appropriate for a rapid scan of the heart cavities to detect and roughly evaluate flow abnormalities. Quantification is still accomplished by switching to conventional Doppler mode.