Image Scanning Microscopy Technique Extends Beyond Limits

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WARSAW, Poland, Oct. 22, 2020 — A collaboration between researchers at the University of Warsaw and the Weizmann Institute of Science yielded a method of fluorescence microscopy that, in theory, has no resolution limit. In practice, the team demonstrated a fourfold improvement over the diffraction limit.

The technique, superresolution optical fluctuation image scanning microscopy (SOFISM), uses the naturally occurring fluctuations in emission intensity of fluorescent markers to further enhance the image scanning microscope (ISM)’s spatial resolution. ISM, itself an emerging technique, uses a confocal microscope in which a detector array replaces a single detector. In SOFISM, correlations of intensities detected by multiple detectors are computed.

In principle, the measurement of the nth order correlation can lead to a factor of 2n resolution improvement (with respect to the diffraction limit).

In practice, the resolution achievable for higher-order correlations is limited by the signal-to-noise ratio of the measurements.
A 3 µ microns x 3 µ confocal scan of microtubules in a fixed 3T3 cell labelled with quantum dots analyzed in two ways. Upper left: image scanning microscopy (ISM), lower right: super-resolution optical fluctuation image scanning microscopy (SOFISM) after Fourier-reweighting. Courtesy of the University of Warsaw.

A 3- × 3-µm confocal scan of microtubules in a fixed 3T3 cell labeled with quantum dots analyzed in two ways. Upper left: image scanning microscopy (ISM). Lower right: superresolution optical fluctuation image scanning microscopy (SOFISM) after Fourier reweighting. Courtesy of the University of Warsaw.

“SOFISM is a compromise between ease of use and resolution. We believe that our method will fill the niche between the complex, difficult-to-use techniques providing very high resolution and the easy-to-use lower-resolution methods,” said Radek Lapkiewicz of the University of Warsaw. “SOFISM does not have a theoretical resolution limit, and in our article, we demonstrate results which are four times better than the diffraction limit. We also show that the SOFISM method has a high potential in the imaging of three-dimensional biological structures.

“Until recently, SPAD array detectors were expensive and their specifications were not sufficient for correlation-based microscopy. This situation has recently changed. The new SPAD detectors introduced last year removed both the technological and price-related barriers. This makes us think that fluorescence microscopy techniques such as SOFISM might, in a few years’ time, become widely used in the field of microscopic examination.” 

The research was published in Optica (

Published: October 2020
fluorescence microscopy
Fluorescence microscopy is a specialized optical imaging technique used in biology, chemistry, and materials science to visualize and study specimens that exhibit fluorescence. Fluorescence is the phenomenon where a substance absorbs light at one wavelength and emits light at a longer wavelength. In fluorescence microscopy, fluorescent dyes or proteins are used to label specific structures or molecules within a sample. The basic principles of fluorescence microscopy involve illuminating the...
Superresolution refers to the enhancement or improvement of the spatial resolution beyond the conventional limits imposed by the diffraction of light. In the context of imaging, it is a set of techniques and algorithms that aim to achieve higher resolution images than what is traditionally possible using standard imaging systems. In conventional optical microscopy, the resolution is limited by the diffraction of light, a phenomenon described by Ernst Abbe's diffraction limit. This limit sets a...
Research & TechnologyMicroscopyconfocal microscopeconfocal microscopyfluorescence microscopyimage scanning microscopyISMsuper resolution microscopysuperresolutionsuperresolution fluorescence microscopysuperresolution microscopySOFISMEuropeIsraelUniversity of Warsaw

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