title: Static and dynamic errors in particle tracking microrheology.
abstract: Particle tracking techniques are often used to assess the local mechanical properties of cells and biological fluids. The extracted trajectories are exploited to compute the mean-squared displacement that characterizes the dynamics of the probe particles. Limited spatial resolution and statistical uncertainty are the limiting factors that alter the accuracy of the mean-squared displacement estimation. We precisely quantified the effect of localization errors in the determination of the mean-squared displacement by separating the sources of these errors into two separate contributions. A "static error" arises in the position measurements of immobilized particles. A "dynamic error" comes from the particle motion during the finite exposure time that is required for visualization. We calculated the propagation of these errors on the mean-squared displacement. We examined the impact of our error analysis on theoretical model fluids used in biorheology. These theoretical predictions were verified for purely viscous fluids using simulations and a multiple-particle tracking technique performed with video microscopy. We showed that the static contribution can be confidently corrected in dynamics studies by using static experiments performed at a similar noise-to-signal ratio. This groundwork allowed us to achieve higher resolution in the mean-squared displacement, and thus to increase the accuracy of microrheology studies.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Thierry
authors.initials: T
authors.lastname: Savin
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Doyle
mesh_terms: D000465:Algorithms; D001703:Biophysics / Q000379:methods*; D004058:Diffusion; D004548:Elasticity; D018715:Microscopy, Video / Q000379:methods; D008958:Models, Molecular; D015233:Models, Statistical; D008962:Models, Theoretical; D016011:Normal Distribution; D009991:Oscillometry; D017785:Photons; D015203:Reproducibility of Results; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water