1. A method for imaging particles using a particle analysis system configured for combined viscosity and geometric hydrofocusing, the particles included within a blood fluid sample, the method comprising: injecting a sheath fluid along a flowpath of a flowcell of the particle analyzer, the sheath fluid having a viscosity that is different from a viscosity of the blood fluid sample; injecting the blood 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 fluid stream 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 fluid stream decreases from the initial thickness to a second thickness adjacent an image capture site; imaging a first plurality of the particles from the sample at the image capture site of the flowcell; 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 viscosity 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, while a viscosity agent in the sheath fluid retains viability of cells leaving structure and content of the cells intact when the cells extend from the sample fluid stream into the flowing sheath fluid as the cells travel from the sample fluid injection tube to the image capture site.