Correlated microscopy

Combine data from different imaging devices

Multimodal correlated imaging
Harald Hausen

Main content

The general idea of multimodal correlative imaging is to increase the informational content of images by combining data generated with different imaging devices. Recorded position data or sample features are used to find back the same region in the different instruments and later for computing precise overlays of the data sets obtained. 2D data correlation is sufficient for thin and flat samples but it is likewise possible to correlate whole 3D image volumes. Multimodal correlative imaging can be used for many purposes and is a fast-developing field. It is well implemented at ELMILAB on all levels from instrumentation to sample preparation and image processing.

Imaging across scales of magnification

Multimodal imaging can be used for targeting tiny features in large samples by imaging the samples with devices of increasing resolution. Accordingly, are electron microscopes often the last method used. Low-resolution images prepared with other devices can be imported into the controlling software of ELMILAB instruments and be directly used for navigating to sample regions of interest. Approximate overlay images can be created while imaging. The computation of precise overlays is conducted later with suitable software tools.

Combining data of different quality

By correlating data of different modalities like fluorescence microscopy, x-ray tomography, electron microscopy, and others, very information-rich data sets can be generated and provide insights that could not be obtained by separate analyses of the data. Precise image registration in 2D and 3D is mandatory and requires that enough corresponding features and be identified in the different datasets. The main challenge often is to prepare the samples in a manner that is compatible with the different imaging approaches that shall be combined.

Applications in life sciences

Correlative light and electron microscopy (CLEM) is the most frequently used flavor of multimodal imaging in life sciences and allows for studying the ultrastructural context of molecular biological experiments. Fluorescent signals of markers like antibodies, dyes, tagged reporter constructs, or nanoparticles can be directly visualized on high-resolution images taken in the electron microscope. A straightforward approach implemented at ELMILAB is to prepare ultrathin sections which are mounted on silicon wafers or coated cover slipes first with light and then with scanning electron microscopy. This is possible in 2D on single sections or 3D by imaging serial sections. The only prerequisite is to carefully optimize fixation, sample dehydration, and embedding so that both the molecular markers and the ultrastructural features are retained and accessible for relevant stains. The microwave-assisted sample preparation available at ELMILAB allows for fast and efficient protocol adjustments. The Zeiss Gemini 450 microscope is best suited for correlative imaging.

Applications in materials and geosciences