Blood perfusion measurement with multifrequency Doppler ultrasound.

Due to its sensitivity to measurement artifacts, the ultrasonic Doppler technique has not yet become a clinically useful tool for blood perfusion measurements. One of these measurement artifacts is caused by ultrasonic wave interference in combination with the small changes of structures inside the ultrasonic field. These changes are a result of variations in blood pressure, small movements in muscles, and involuntary movements of the transducer. The changes alter the ultrasonic interference pattern, causing fluctuations in the measured perfusion value. In this paper a new multifrequency technique for blood perfusion measurement is presented. The technique is based on a multifrequency setup, with four ultrasonic frequencies simultaneously transmitted with the same transducer. It is shown that by averaging the measured values obtained from each frequency, the sensitivity to ultrasonic wave interference can be lessened. Measurement results from both in vitro and in vivo experiments are presented.