Patent ID: 6982038

Claim:
A centrifugal method of processing a fluid having red blood cells and platelets dispersed therein and of collecting a volume of the fluid being rich with the platelets which are less susceptible to centrifugal forces than the red blood cells, comprising: receiving a fill device containing a fill volume of the fluid having red blood cells and platelets and a collection device for storing the collected volume of the fluid being rich with the platelets; filling a separation chamber with the fluid having red blood cells and platelets including pumping the fluid having red blood cells and platelets from the fill device through a fluid connection line to the separation chamber, wherein during the filling the separation chamber is rotated by a centrifuge at a fill rotation rate; performing a soft spin to first separate the red blood cells from the platelets in the fluid by operating the centrifuge to spin the separation chamber at a soft spin rotation rate; first withdrawing a first volume of the fluid from the separation chamber to remove a first portion of the red blood cells, the first withdrawing includes pumping a fast withdraw volume of the fluid with the red blood cells away from the separation chamber, the first withdrawing includes determining a calibrated output signal from a sensor proximal the separation chamber during the fast withdraw volume pumping; second withdrawing a second volume of the fluid from the separation chamber to remove a second portion of the red blood cells, wherein the second withdrawing includes monitoring the separation chamber via the sensor for an interface between the red blood cells and the platelet rich volume in the fluid, and pumping the second volume of the fluid away from the separation chamber until the interface is detected, wherein the interface monitoring includes comparing signals received from the sensor with the calibrated output signal during fluid pumping of the second volume, pumping a line clearing volume of the fluid from the separation chamber and the fluid connection line to remove remaining fluid containing the red blood cells from the separation chamber and the fluid connection line; and collecting the collection volume of the fluid rich with the platelets by pumping the fluid with the platelets from the fluid connection line and the separation chamber into the collection device until the collection volume has been received in the collection device.