An imaging system may be used to image a fluid sample containing particles. The imaging system may include a fluid channel that receives the fluid sample and a reactive agent that selectively attaches to target particles in the fluid sample. An activation mechanism may be operated to trigger a chemical reaction between the fluid sample and the reactive agent. The imaging system may include an image sensor integrated circuit and image sensor pixels to capture a detectable effect of the chemical reaction. The image sensor integrated circuit may be synchronized to the activation mechanism such that it captures an image of the fluid sample after the chemical reaction is triggered by the activation mechanism.