- The paper introduces Fourier Synthesis Optical Diffraction Tomography (FS-ODT), a novel method enabling 3D refractive index imaging at kilohertz rates.
- FS-ODT leverages new pattern multiplexing and computation strategies to achieve high-speed volumetric data acquisition.
- Validated on various samples, FS-ODT enables detailed study of rapid biological processes and particle dynamics in complex environments.
Fourier Synthesis Optical Diffraction Tomography for Kilohertz Rate Volumetric Imaging
The paper presented here describes Fourier Synthesis Optical Diffraction Tomography (FS-ODT), a novel imaging technique that extends the capabilities of quantitative phase imaging by achieving kilohertz volumetric imaging rates. This method represents a significant advancement in the field of three-dimensional biological imaging, particularly when high-speed imaging is required to capture rapid processes occurring in complex environments often found in biological and soft matter systems.
FS-ODT is introduced as a quantitative phase imaging technique capable of recording the three-dimensional refractive index of samples at kilohertz rates. It leverages new pattern generation methods and inverse computation strategies to multiplex multiple illumination angles into a single tomogram, thereby increasing the volumetric imaging rate substantially. The validation of FS-ODT is presented through its application in imaging various samples—namely, polystyrene microspheres (PMS) and biological organisms such as Tetrahymena and E. coli. The performance of FS-ODT was assessed by accurately recovering the refractive index across different pattern complexities and demonstrating its utility in studying hindered diffusion and microswimmer motility in colloid systems.
The core innovation of FS-ODT lies in its approach to pattern multiplexing—both through position multiplexing, which extends the system's field of view, and angle multiplexing, which improves the depth and volume of information captured in each image cycle. The systemic architecture involves a Digital Micromirror Device (DMD) designed to work at high refresh rates, which can be configured to generate multiple overlapping illumination patterns that synthesize simple atomic patterns in the Fourier plane. The result is a substantial increase in information content per image, allowing for high-speed acquisition without compromising image quality.
The ability for FS-ODT to generate a large number of multiplexed patterns addresses existing challenges in ODT, where traditionally the need for many angular views limits the speed of acquisition. By using multiplexed light patterns, FS-ODT manages to perform high-quality tomographic reconstructions at speeds not achievable with previous methods. This is particularly pertinent in studying samples with complex scattering and dynamic environments—a field (without metaphorical intention) where traditional phase microscopy methods like CLM, DHM, and SIP fail.
Describing the technique's performance, the authors present evidence that FS-ODT achieves robust 3D refractive index reconstructions across varying experimental conditions and sample types. For instance, the imaging of a single \qty{10}{\micro\meter} PMS in immersion oil at multiple multiplexing factors demonstrates the technique's reliability and accuracy, as high-quality reconstructions were consistent across all multiplexing levels tested. The living environments of microorganisms such as E. coli and Tetrahymena are also effectively imaged using FS-ODT, indicating its potential applicability across different biological scales and contexts.
Practically, FS-ODT's ability to offer kilohertz-scale imaging speeds while maintaining resolution and field of view enables the probing of rapid biological processes and particle kinetics in situ. It suggests significant potential for widespread use in biophysical research, including the investigation of cell motility within viscoelastic and heterogeneous media. Theoretical implications include exploring physical interactions in complex 3D environments, where mechanics and micro-dynamics are critical.
Future developments in FS-ODT are likely to explore enhancements in hardware to further boost imaging rates and maintain image fidelity. This might include adopting faster and more efficient light modulation technologies like acousto-optic and electro-optic modulators, as well as refining the multiplexing algorithms through machine learning techniques to handle increased complexity and potentially reduce computational overhead.
In conclusion, the development of FS-ODT represents an important progression in the capability of phase imaging technologies to address the demand for high-speed, high-resolution volumetric imaging in biological and soft-matter research, promising significant advancements in our understanding of microscopic and mesoscale phenomena.