1. A method for imaging particles using a particle analysis system configured for geometric hydrofocusing, the particles included within a body fluid sample, the method comprising: injecting a sheath fluid along a flowpath of a flowcell of the particle analyzer; injecting the body fluid sample from a sample fluid injection tube at a flow rate into the flowing sheath fluid within the flowcell so as to provide a sample flowstream having a first thickness adjacent the injection tube, the flowpath of the flowcell having a decrease in flowpath size such that thickness of the sample flowstream decreases from the initial thickness to a second thickness adjacent an image capture site; focusing an image capture device by imaging an imaging target having a position fixed relative to the flowcell, the imaging target and sample flowstream defining a predetermined displacement distance along the imaging axis; and acquiring a focused image of a first plurality of the particles from the first sample along the imaging axis at the image capture site of the flowcell, suitable for particle characterization and counting, within the flowstream with the image capture device, wherein the image capture device is focused on the sample flowstream using the focusing step and the predetermined displacement distance, wherein the decrease in flowpath size is defined by a proximal flowpath portion having a proximal thickness, and distal flowpath portion having a distal thickness less than the proximal thickness, wherein a downstream end of the sample fluid injection tube is positioned distal to the proximal flowpath portion, wherein the velocity difference between the sheath and blood fluid samples, in combination with the decrease in flowpath size and the flow rate of the sample, is effective to deliver cells in the sample from the sample fluid injection tube to the image capture site in four seconds or less.