Methods and apparatus for collecting and treating blood component. An apparatus and methods for improvement of an extracorporeal photopheresis treatment is described. A cassette having flexible tubes inside its housing and on the bottom surface outside the cassette housing for ease of manufacturing is operated with a centrifuge bowl having an inlet and two outlets, pressure domes for measuring pressures in tubes, an improved irradiation plate, and a dual chamber bag in an extracorporeal photopheresis treatment.
