Relationship of cell size measured by time-of-flight and ploidy. (A) Time-of-flight is the time required for a cell in suspension to pass through a focused light beam, as measured by the pulse width. This measurement is proportional to the cell diameter as illustrated (adapted from Shapiro²¹ ). (B) Relationship between time-of-flight measurement and particle diameter. Small-angle light scatter of standard beads (10-70-μm diameter) was detected by flow cytometry, and the pulse width was measured. The solid line represents the linear regression (r = 0.99). (C) Cell diameter, surface area, and volume of normal human MKs. The derived cell surface areas and volumes were calculated, assuming sphere-shaped particles. (D) Relationship between cell diameter, measured by time-of-flight, and ploidy of normal human marrow megakaryocytes (n = 19). Data are mean ± SD.