In some examples, a system including a fluid stream monitoring system. The monitoring system includes an illumination device configured to illuminate at least some of particles suspended in a fluid stream; and an imaging device configured to image the illuminated particles at a first image plane that intersects a longitudinal axis of the fluid stream, wherein the illumination device and the imaging device are registered to the fluid stream delivery device in the first image plane, where the first image plane is substantially orthogonal to the longitudinal axis. The system includes processing circuitry configured to determine one or more physical characteristics of the fluid particles.