Ultrasonic doppler imaging systems with improved flow sensitivity

Abstract

An ultrasonic blood flow measuring and imaging system comprises a transmit-receive transducer for transmitting ultrasonic waves toward and into the human body and for receiving reflected echo signals which are then processed for use in a Doppler blood flow imaging and display system. Multiple ultrasonic pulse beams are transmitted into the body at each of a number of angles in an area under diagnosis. For each angle, a plurality of reflected echo signals are received during successive predetermined time intervals. Each received echo signal has a stationary component reflected from essentially stationary tissue and a Doppler component reflected from areas where movement is sensed, such as blood flow. The reflected echo signals are processed in an MTI filter subtracting a stationary component from the received echo signals to thereby extract a Doppler signal representative of a Doppler component of the received echo signals. The Doppler component is then processed in an MTI filter equalizer having a frequency response which is the inverse of the MTI filter, for producing an output having an essentially flat frequency response over the range of frequencies being measured. The output is used to produce color flow imaging of the blood flow in the area under diagnosis.