Flow imaging can be used for the analysis of subvisible particles (2 μm to 100 μm in size) in suspension. As a sample stream passes through a flow cell positioned in the field of view of a microscopic system, bright-field images are captured in successive frames. The digital images of the particles present in the sample are stored in a database that can be retrieved and analyzed for count, size, transparency, and various other morphological parameters. Protein particle concentration is reported for one or more size bins as an equivalent circular diameter (ECD), defined as the diameter of a polystyrene microsphere with the same image area as the observed particle. The subvisible protein particle content of RM 8671 lots was evaluated according to the optimized protocol described previously . Figure 6 shows representative images obtained for various particles in the three lots.Fig. 6Representative images of proteinaceous particles and their sizes (in equivalent circular diameter) obtained from 14HB-D-001, 14HB-D-002, and 14HB-D-003 analyses