Abstract: There is provided an ultrasonic diagnostic system wherein received signals are generated in such a manner that ultrasonic pulse beams are transmitted within a subject and reflecting ultrasonic waves from an inside of the subject are received, and a tomographic image is obtained on the basis of the received signals. The ultrasonic diagnostic system is capable of detecting a velocity or a velocity gradient as to the tissue within the subject. Two digital complex signals [R.sub.i (t)+j I.sub.i (t)] and [R.sub.i (t+.DELTA..tau.)+j I.sub.i (t+.DELTA..tau.)], which are apart from each other by .DELTA..tau., are obtained from a complex signal (quadrature detection signal) [h.sub.ci (t)+j h.sub.si (t)] outputted from a complex signal conversion circuit. A phase difference .DELTA..theta..sub.i,i+1 (t) is determined from a complex correlation value C.sub.i,i (t,.DELTA..tau.) of these two complex signals. Further, the phase difference .DELTA..theta..sub.i,i+1 (t) is determined from a complex correlation value C.sub.

Abstract: A parameter of blood is sensed with a system which includes a catheter and a sensor and a volume oscillator element. The catheter has a lumen extending therethrough, a proximal end, a distal end and an opening, adapted to be placed in the blood vessel of a patient. The sensor senses a blood parameter and is adapted to be located outside the patient's body in fluid communication with the lumen. The volume oscillator element is in fluid communication with the lumen and is capable of acting to periodically cause blood to enter and exit the lumen. The system is structured so that a flush or anti-clotting solution flows into the patient when the volume oscillator element is inactive. With the volume oscillator activated, blood is moved back and forth in the lumen to expose the sensors to blood so that the blood parameter of interest can be sensed.