1. A particle analysis system that performs geometric hydrofocusing for imaging particles in a body fluid sample, the system comprising: a flowcell having a flowpath, the flowpath comprising a first channel and a second channel; a sheath fluid injection system, wherein an output of the sheath fluid injection system is fluidly connected to the first channel, a sample fluid injection system in fluid communication with the flowpath, the sample fluid injection system comprising an injection tube, wherein: an outlet of the injection tube is fluidly connected to the second channel, the first channel and the second channel are coaxial about a longitudinal axis, and a cross-sectional area of the second channel decreases from the outlet of the injection tube to an image capture site, the cross sectional area orthogonal to the longitudinal axis; an image capture device aligned with the image capture site along an imaging axis; an imaging target fixed to the flowcell; a focusing module comprising a focusing mechanism to move the image capture device; and a processor operatively coupled to the image capture device, wherein the processor is programmed to: control the image capture device to acquire a first image of the imaging target, analyze the first image for a level of contrast, determine, using the level of contrast, a first position of the image capture device from the imaging target where an image of the imaging target is focused, control the focusing mechanism to move the image capture device to a second position a predetermined distance from the first position along the imaging axis, wherein the predetermined distance is nonzero, and control the image capture device at the second position to acquire a second image, wherein the second image is focused at the predetermined distance from the imaging target.