The ornamental design for a handheldultrasoundsystem, as shown and described.
FIG. 1 is a perspective view of a handheld ultrasound system;
FIG. 2 is a top view thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a back view thereof; and,
FIG. 7 is a front view thereof.
The broken lines depict portions of the handheld ultrasound system that form no part of the claimed design; the broken lines form no part of the claimed design.