Rapid, topology-based particle tracking for high-resolution measurements of large complex 3D motion fields

Abstract

Spatiotemporal tracking of tracer particles or objects of interest can reveal localized behaviors in biological and physical systems. However, existing tracking algorithms are most effective for relatively low numbers of particles that undergo displacements smaller than their typical interparticle separation distance. Here, we demonstrate a single particle tracking algorithm to reconstruct large complex motion fields with large particle numbers, orders of magnitude larger than previously tractably resolvable, thus opening the door for attaining very high Nyquist spatial frequency motion recovery in the images. Our key innovations are feature vectors that encode nearest neighbor positions, a rigorous outlier removal scheme, and an iterative deformation warping scheme. We test this technique for its accuracy and computational efficacy using synthetically and experimentally generated 3D particle images, including non-affine deformation fields in soft materials, complex fluid flows, and cell-generated deformations. We augment this algorithm with additional particle information (e.g., color, size, or shape) to further enhance tracking accuracy for high gradient and large displacement fields. These applications demonstrate that this versatile technique can rapidly track unprecedented numbers of particles to resolve large and complex motion fields in 2D and 3D images, particularly when spatial correlations exist.

Mechanophenotyping of 3D multicellular clusters using displacement arrays of rendered tractions

“…Measuring 3D Cell-Induced Deformations via TPT. We utilized our previously developed TPT algorithm (39) to reconstruct the cell-induced 3D displacement fields by tracking individual fluorescent polystyrene microspheres (1 µm) embedded as fiduciary markers in the silk-collagen matrix. The combination of light-emitting diode illumination-based spinning-disk confocal microscopy and low-NA objective for low-cost, high-throughput imaging of the 96-well-plate setup resulted in diminished signal-to-noise volumetric images.…”

“…These MCF-10A Snail-estrogen receptor (ER) cells were stably transfected to overexpress green fluorescent protein (GFP) in the cytoplasm, as well as an inducible ER construct for controlled EMT through the Snail transcription factor (37,38). Cluster-induced deformations of the hydrogel were visualized by using our topological particle-tracking algorithm to map the displacement of 80,000 to 100,000 tracer particles around each cluster (39), after which the clusters were lysed to define a reference state. This case study focused on clusters cultured for 7 d, since EMT induction in this cell line typically occurs over several days or more (40).…”

“…S4). The displacement noise floor obtained with our topology-based particle tracking (TPT) algorithm was 20.5 nm (39). Finally, the spatial heterogeneity of tractions was then quantified from the number of regions which exceeded the radial or circumferential displacement threshold.…”

Mechanophenotyping of 3D Multicellular Clusters using Displacement Arrays of Rendered Tractions

“…These MCF-10A Snail-ER cells were stably transfected to overexpress green fluorescent protein (GFP) in the cytoplasm, as well as an inducible estrogen receptor construct for controlled EMT through the Snail transcription factor 27,28 . Cluster-induced deformations of the hydrogel were visualized using our topological particle tracking algorithm to map the displacement of 80,000-100,000 tracer particles around each cluster 29 , after which the clusters were lysed to define a reference state. This case study focused on clusters cultured for 7 days, which exhibited distinct morphologies ( Fig.…”

Three-dimensional measurement of small-object surfaces on the basis of fiber optic interferometric fringe projection

“…A new optical information method developed using 3-D shape measurement technology exploits an optical image to detect and transmit information and extract relevant details from captured images, thus completing the recovery and measurement of the 3-D shapes of objects in a computer. [1][2][3] Therefore, phase measurement profilometry based on fringe-structured light projection satisfies the demand for 3-D object surface topography measurement in the previously mentioned application domains. This technology applies the principle of optical triangulation measurement, which can also be applied to the 3-D surface topography measurement of static and dynamic objects.…”