Researchers at Nicolaus Copernicus University in Toruń developed an innovative full-field optical coherence elastography system that enables much faster three-dimensional imaging of tissue mechanical properties. Published in the journal Optica, their findings show that rapid data acquisition can be achieved without compromising the high phase stability needed to detect microscopic tissue displacements with high sensitivity. In the future, this technology could support cancer diagnosis and the intraoperative assessment of surgical margins.
Optical coherence elastography (OCE) is an emerging imaging technique that uses optical coherence tomography (OCT) to measure minute deformations in biological samples subjected to controlled mechanical loading. This makes it possible to map tissue mechanical properties, such as relative stiffness or deformability. Such mechanical contrast can reveal pathological changes that alter tissue mechanical properties but may not be visible in conventional structural images.
Volumetric imaging is particularly important in biomedical applications. Tumors are often stiffer than the surrounding healthy tissue and may also exhibit considerable microscopic heterogeneity in their mechanical properties. Producing high-resolution three-dimensional images of tumors therefore requires rapid acquisition over large tissue volumes without compromising sensitivity to minute deformations.
Conventional OCE systems typically use a focused light beam that scans across the sample. Although this approach enables sensitive imaging of tissue mechanical properties, the time required to acquire three-dimensional datasets can be a major limitation. Increasing the scanning speed can also introduce additional phase noise, reducing the accuracy of measurements of minute tissue displacements.
The system developed by the NCU researchers uses a full-field approach. Instead of scanning the sample point by point, a high-speed camera captures signals simultaneously across the entire field of view. Combined with a wavelength-swept light source, this enables three-dimensional optical data to be acquired during a single wavelength sweep.
The system developed by the NCU researchers uses a full-field approach. Instead of scanning the sample point by point, a high-speed camera captures signals simultaneously across the entire field of view, while a stable wavelength-swept light source enables three-dimensional optical data to be acquired during a single wavelength sweep. Particular emphasis was placed on minimizing phase noise through a common-path interferometer configuration and active reduction of the spatial coherence of the illumination. Together, these features provide high phase stability in volumetric measurements while maintaining the substantial increase in acquisition speed.
The developed system acquires elastographic images at a rate of two volumes per second, corresponding to an effective acquisition rate of 4.2 million A-scans per second. At comparable signal levels, it provides better phase and strain sensitivity than a reference scanning OCE system. This enables three-dimensional strain maps to be acquired much faster without compromising the measurement sensitivity required for elastographic imaging.
The system was first validated using silicone phantoms with controlled optical and mechanical properties and was subsequently tested on freshly excised human breast cancer specimens. In the tissue studies, elastographic images were compared with conventional histopathological assessment. The results showed that regions containing malignant tumour tissue exhibited substantially greater spatial heterogeneity in strain than the connective tissue surrounding the tumour. The study represents a step towards the clinical use of OCE in cancer diagnosis, with the potential to help distinguish malignant from healthy tissue and support the intraoperative assessment of surgical margins.
The research was conducted by scientists from the Institute of Physics at Nicolaus Copernicus University in Toruń, NCU’s Collegium Medicum in Bydgoszcz, and the Prof. Franciszek Łukaszczyk Oncology Centre in Bydgoszcz. The findings were published in Optica, one of the leading journals in optics and photonics: https://doi.org/10.1364/OPTICA.589818.
Team:
NCU Institute of Physics: Seweryn Morawiec, Matt S. Hepburn, Marta K. Skrok, Patrycjusz Stremplewski, Maciej Szkulmowski, Brendan F. Kennedy
NCU Collegium Medicum: Mateusz Maniewski, Łukasz Szylberg