We claim the ornamental design for a catheter system cassette, as shown and described.
FIG. 1 is a perspective view from above of an embodiment of the claimed design;
FIG. 2 is a top view of the claimed design of FIG. 1; and,
FIG. 3 is a right-side view of the claimed design of FIG. 1.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.