Static and Dynamic Errors in Particle Tracking Microrheology

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 u...

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Bibliographic Details
Published in:Biophysical journal 2005-01, Vol.88 (1), p.623-638
Main Authors: Savin, Thierry, Doyle, Patrick S.
Format: Article
Language:English
Subjects:
Algorithms
Biophysics
Biophysics - methods
Diffusion
Elasticity
Error propagation
Fluids
Microscopy
Microscopy, Video - methods
Models, Molecular
Models, Statistical
Models, Theoretical
Molecules
Normal Distribution
Oscillometry
Photons
Reproducibility of Results
Spectroscopy, Imaging, Other Techniques
Time Factors
Water - chemistry
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Summary: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.
ISSN:0006-3495
1542-0086
DOI:10.1529/biophysj.104.042457