As told by Shanklin, 2016, 2D SEM images can be turned into 3D object models. “3D surface modeling that can be created using scanning electron microscope absolutely lead to significant understanding of attributes of microscopic surfaces, such as fracture toughness, crack growth and propagation or fracture resistance” (Shanklin, 2016). I considered SEM images, turned them into .ppm format. The .ppm file has been read by a Fortran program to create the 3D mesh, by means of vertices and faces, saved in .obj file format (see please the folder in the dataset). Here I show some cases: Honeycomb, Pores of freeze-dried solutions, Microcellular plastic, Biochar, Wood pores, 'Hexagon' detail of Corbaea scandens, Pollen, Worms, that is a pair of Schistosoma mansoni, and a 'Bassorilievo' and a rendering of Turin Shroud, to show that is it possible to obtain a 3D mesh from pictures. Details and references are given in the .pdf file. Visualizations of .obj files have been obtained by means of https://3dviewer.net/ and GIMP software.

Scanning electron microscopy (SEM) has an important application in the petroleum field, which is often used to analyze the microstructure of reservoir rocks, etc. Most of these analyses are based on two-dimensional images. In fact, SEM can carry out micro-nano scale three-dimensional measurement, and three-dimensional models can provide more accurate information than two-dimensional images. Among the commonly used SEM 3D reconstruction methods, parallax depth mapping is the most commonly used method. Multiple SEM images can be obtained by continuously tilting the sample table at a certain Angle, and multiple point clouds can be generated according to the parallax depth mapping method, and a more complete point clouds recovery can be achieved by combining the point clouds registration. However, the root mean square error of the point clouds generated by this method is relatively large and unstable after participating in point clouds registration. Therefore, this paper proposes a new method for generating point clouds. Firstly, the sample stage is rotated by a certain angle to obtain two SEM images. This operation makes the rotation matrix a known quantity. Then, based on the imaging model, an equation system is constructed to estimate the unknown translation parameters, and finally, triangulation is used to obtain the point clouds. The method proposed in this paper was tested on a publicly available 3D SEM image set, and the results showed that compared to the disparity depth mapping method, the point clouds generated by our method showed a significant reduction in root mean square error and relative rotation error in point clouds registration.

Here we provide a Fortran file to create a 3D mesh (.obj file format) from a 2D grey-scale image, for instance, a SEM (Scanning Electron Microscope) image. The zipped folder contains some examples of 3D reconstructions, as .obj files, that can be visualized on-line by means of https://3dviewer.net/ .

The Focused Ion Beam Scanning Electron Microscope (FIB-SEM) system market is experiencing robust growth, projected to reach a value of $595.5 million in 2025 and maintain a Compound Annual Growth Rate (CAGR) of 5.7% from 2025 to 2033. This expansion is driven primarily by the increasing demand for high-resolution 3D imaging and analysis across diverse scientific and industrial applications. Advancements in materials science, semiconductor manufacturing, and nanotechnology necessitate precise and detailed characterization capabilities, fueling the adoption of FIB-SEM systems. The rising need for failure analysis in electronics and the development of advanced materials with complex microstructures further contribute to market growth. Key players like Thermo Fisher Scientific, Hitachi, Zeiss, JEOL Ltd, Tescan Group, and Raith are driving innovation through technological improvements, expanding product portfolios, and strategic partnerships, fostering competition and accelerating market penetration. The market is segmented by application (e.g., materials science, life sciences, semiconductor), by resolution, and by end-user (e.g., research institutions, industrial labs). While potential restraints could include high initial investment costs and the need for specialized expertise, the overall market outlook remains positive due to the continuous expansion of applications and technological advancements. The historical period (2019-2024) exhibited a growth trajectory consistent with the projected CAGR, indicating a steady market expansion. Future growth will likely be influenced by factors such as government funding for research and development in nanotechnology and materials science, as well as the increasing adoption of FIB-SEM in quality control and process optimization within manufacturing sectors. Furthermore, the development of more user-friendly software and integrated solutions could broaden the user base and drive market expansion. Competitive pressures will likely lead to further price optimization and the introduction of more cost-effective systems, making FIB-SEM technology more accessible to a wider range of users. The geographical distribution of market share will vary based on research and industrial activity, with established economies likely holding a larger share initially.

Supplementary Movies of the peer reviewed publication:FIB/SEM technology and high-throughput 3D reconstruction of dendritic spines and synapses in GFP-labeled adult-generated neurons. Front. Neuroanat. | doi: 10.3389/fnana2015.00060

Sample: Single-innervated Meissner corpuscle from the forepaw of a 3-week-old C57BL/6J WT mouseSample Description: Across mammalian skin, structurally complex and diverse mechanosensory end organs respond to mechanical stimuli and enable our perception of dynamic, light touch. How forces act on morphologically dissimilar mechanosensory end organs of the skin to gate the requisite mechanotransduction channel Piezo2 and excite mechanosensory neurons is not understood. Here, we report high-resolution reconstructions of the hair follicle lanceolate complex, Meissner corpuscle, and Pacinian corpuscle and the subcellular distribution of Piezo2 within them. Across all three end organs, Piezo2 is restricted to the sensory axon membrane, including axon protrusions that extend from the axon body. These protrusions, which are numerous and elaborate extensively within the end organs, tether the axon to resident non-neuronal cells via adherens junctions. These findings support a unified model for dynamic touch in which mechanical stimuli stretch hundreds to thousands of axon protrusions across an end organ, opening proximal, axonal Piezo2 channels and exciting the neuron.This dataset contains manually proofread automatic segmentation of the FIB-SEM dataset in jrc_mus-meissner-corpuscle-1.Protocol: Samples were dissected and drop fixed in glutaraldehyde and paraformaldehyde, and then osmicated with osmium tetroxide and potassium ferrocyanide, followed by osmium tetroxide only. Samples were subsequently stained with uranyl acetate and samarium chloride. Samples were dehydrated with an ethanol series followed by anhydrous acetone, infiltrated with Durcupan resin, and cured at 60°C.Contributions: Sample provided by Annie Handler (Harvard Medical School/HHMI) and Qiyu Zhang (Harvard Medical School/HHMI), prepared for imaging by Song Pang (HHMI/Janelia, currently at Yale School of Medicine), imaged by Song Pang and C. Shan Xu (HHMI/Janelia, currently at Yale School of Medicine), post data registration by C. Shan Xu, global image alignment and processing by Annie Handler and Qiyu Zhang, automatic segmentation by Tri M. Nguyen (Harvard Medical School) under the supervision of Wei-Chung Allen Lee (Harvard Medical School), ground truth annotation by Rebecca Plumb, Brianna Sanchez, Karyl Ashjian, Aria Shotland, Bartianna Brown, Madiha Kabeer, Nusrat Africawala, Stuart Cattel, Annie Handler, and Qiyu Zhang (all Harvard Medical School/HHMI), and segmentation proofreading by Annie Handler, Qiyu Zhang, and Michael Nolan-Tamariz (Harvard Medical School/HHMI).Acquisition ID: jrc_mus-meissner-corpuscle-1Voxel size (nm): 6 x 6 x 6 (x, y, z)Data dimensions (µm): 36.7 x 45.3 x 57.2 (x, y, z)Scanning speed (MHz): 1Dataset URL: s3://janelia-cosem-datasets/jrc_mus-meissner-corpuscle-1/jrc_mus-meissner-corpuscle-1.zarr/recon-1/labels/inference/segmentations/EM DOI: https://doi.org/10.25378/janelia.23969070Visualization Website: https://openorganelle.janelia.org/datasets/jrc_mus-meissner-corpuscle-1Publication: Handler et al., 2023

Materials qualification of reactor structural materials is a critical step in rapid implementation of advanced nuclear reactor technologies, particularly to assess the corrosion performance in these designs. Accelerated qualification of reactor structural materials requires incorporating powerful computational toolsets, such as phase field modelling in the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework, to predict the evolution of structural materials due to corrosion. Accordingly, computational toolsets will require experimental data generated at appropriate length scales to validate accuracy. Focused ion beam (FIB) provides a high degree of control over manipulation of materials for analytical purposes, including capturing data on the evolution in the microstructure and elemental composition of materials at the mesoscale, an appropriate length scale for phase field modelling of intergranular diffusion phenomena using the MOOSE framework. For instance, the FEI Helios G4 UX dual beam plasma FIB microscope at the Irradiated Materials Characterization Laboratory (IMCL) is capable of backscatter diffraction (EBSD) and energy-dispersive x-ray spectroscopy (EDS) documenting the evolution in the microstructure and elemental composition, respectively. The Helios can perform EDS and EBSD three-dimensionally (3D) using tomography, which is then combined using different software packages to visualize 3D volumes correlating elemental composition to microstructural data. The purpose of this investigation was to develop a streamlined characterization and data processing workflow for 3D tomography studies on the FEI Helios G4 plasma FIB. The investigation is segmented into three parts: 1) Optimizing the data collection workflow, 2) identifying appropriate data processing and visualization software (i.e. DREAM.3D, MIPAR, and VGStudioMax), and 3) establishing an infrastructure for public release. The optimization of the data collection workflow is in collaboration with members of the U220 department to setup formal training on the tomography operation of the G4, through ThermoFisher Scientific, and exploring DREAM.3D, MIPAR, and VGStudioMax data processing/visualization software packages. VGStudioMax currently demonstrates the most promise for future use. Optimization of the data collection and processing workflow is still ongoing. A collaboration with INL High Performance Computing (HPC) established an open-source license for expediting the public release of FIB tomography datasets through HPC. FIB tomography data generated by the G4 will provide comprehensive data for validating 3D phase field mesoscale modelling tools within the MOOSE framework for accelerated qualification of reactor structural materials. label::after { content: "" !important; }

The dataset consists of scanning electron microscope (SEM) images of 3D-imprinted microneedles from fabricated conductive, UV-cured hydrogels composites Financing: Miniatura 7, DEC-2023/07/X/ST5/01377.

We used Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) to perform a 3D analysis of the synapses in the layer III neuropils of the Brodmann areas 3b (somatosensory), 4 (motor), and 17 (visual primary) from human brain samples. 3 human brain autopsies cases have been used to achieve a total of 22 FIB/SEM valid image stacks: 4 stacks in BA17 from a single case (AB7); 9 stacks in BA3b (three stacks per case, AB2, AB3, and AB7); and 9 stacks in BA4 (three stacks per case, AB2, AB3, and AB7). Specifically, we studied synaptic junctions, which were fully reconstructed in 3D. We analyzed the synaptic density, 3D spatial distribution, and type (excitatory and inhibitory), as well as the shape and size of each synaptic junction. Moreover, their postsynaptic targets were determined. The present dataset constitutes a detailed description of the synaptic characteristics of the human cortex, which is a necessary step to better understand the organization of the cortex.

The Cryo-Focused Ion Beam Scanning Electron Microscope (Cryo-FIB-SEM) market is experiencing robust growth, driven by advancements in cryogenic microscopy techniques and the increasing demand for high-resolution 3D imaging in diverse scientific fields. The market, estimated at $250 million in 2025, is projected to exhibit a Compound Annual Growth Rate (CAGR) of 15% from 2025 to 2033, reaching approximately $800 million by 2033. Key drivers include the rising need for detailed structural analysis in materials science, nanotechnology, and biological research, particularly in studying sensitive biological samples without the artifacts introduced by traditional preparation methods. The ability of Cryo-FIB-SEM to provide high-resolution images of frozen hydrated samples makes it invaluable for studying cellular structures, macromolecular complexes, and other delicate specimens. Technological innovations, such as improved ion beam control and automation, are further accelerating market expansion. Market segmentation is primarily driven by application (e.g., materials science, life sciences), instrument type (e.g., standalone systems, integrated platforms), and geography. Major players like JEOL, Carl Zeiss, and Thermo Fisher Scientific are actively investing in research and development to enhance the capabilities of their Cryo-FIB-SEM offerings and expand their market share. Market restraints include the high cost of equipment and maintenance, specialized expertise required for operation, and the relatively small number of researchers with extensive training in cryogenic microscopy. However, ongoing technological advancements are gradually reducing operational complexities and driving down costs, potentially mitigating these restraints. The growing adoption of Cryo-FIB-SEM in academic institutions and research organizations is expected to fuel growth, alongside increasing collaboration between researchers and manufacturers for customized applications. Future market growth will hinge on the continuous development of more user-friendly interfaces, enhanced automation capabilities, and the expansion of applications into new areas like drug discovery and advanced materials characterization. The North American market currently holds a significant share, followed by Europe and Asia, with emerging economies exhibiting promising growth potential.

A single Nickel nanowire has been characterised using 3 experimental techniques.Scanning electron microscope (SEM) data folder contains a single .TIFF image of a fallen Nickel nanowire, where the title refers to the name of the sample.Atomic and magnetic force micrscope (AFM and MFM) data folder contains raw output data where titles refer to the name of the sample (181017JA) and the magnetic field applied (eg 0mT), from software Nanoscope 5, these can be opened in any AFM processing software such as Gwyddion or WSxM. Each file contains data regarding the height (corresponding to AFM) and the phase (corresponding to the MFM).Simulation data folder contains .VTS files where the titles correspond to the appropriate field applied to the simulated wire. The file type .VTS can be opened and viewed within a 3D visualisation program such as Paraview. Research results based upon these data are published at https://doi.org/10.3390/nano10030429

Image datasets from the publication : LimeSeg: A coarse-grained lipid membrane simulation for 3D image segmentation

• Vesicles.tif: spinning-disc confocal images of giant unilamellar vesicles
• HelaCell-FIBSEM.tif: a 3D Electron Microscopy (EM) dataset of nearly isotropic sections of a Hela cell, acquired with a focused ion beam scanning electron microscope (FIB-SEM). Sections are aligned with TrackEm2 (doi: ), without additional preprocessing.
• DrosophilaEggChamber.tif: point scanning confocal images of a Drosophila egg chamber. Channel 1: cell nuclei stained with DAPI. Channel 2: cell membranes visualized with fused membrane proteins Nrg::GFP and Bsg::GFP.

Image metadata contains extra information including voxel sizes.

The Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) market is experiencing robust growth, driven by advancements in nanotechnology, materials science, and semiconductor research. The increasing demand for high-resolution imaging and precise material manipulation at the nanoscale is fueling market expansion across diverse sectors, including academia, research institutions, and the semiconductor industry. Applications range from failure analysis in electronics to advanced materials characterization and 3D reconstruction of biological samples. Considering a conservative estimate based on typical growth in specialized scientific equipment markets, let's assume a 2025 market size of $500 million with a Compound Annual Growth Rate (CAGR) of 7% projected through 2033. This CAGR reflects both the ongoing technological advancements within FIB-SEM technology and the consistent expansion of its applications in various fields. The market segmentation indicates strong demand across both double-beam and multibeam systems, with university and research institutions representing significant customer bases. Leading manufacturers such as Hitachi, Thermo Fisher, JEOL, Zeiss, and Raith GmbH are competing in this dynamic market through continuous innovation and strategic partnerships. The continued development of sophisticated software for data analysis and 3D reconstruction will be a key factor driving future growth. Furthermore, the increasing need for advanced characterization techniques in fields like life sciences and energy research will contribute significantly to market expansion. However, high capital costs associated with FIB-SEM systems and the requirement for specialized expertise in operation and maintenance could potentially restrain market growth, particularly in smaller research labs or developing regions. Nevertheless, the advantages provided by FIB-SEM technology in terms of precision, resolution, and analytical capabilities are expected to outweigh these challenges, ensuring continued market growth throughout the forecast period. The Asia-Pacific region, with its burgeoning technological advancements and growing research investments, is expected to witness significant growth in the coming years.

The Focused Ion Beam Scanning Electron Microscope (FIB-SEM) market is experiencing steady growth, projected to reach a value of $1638.9 million in 2025 and maintain a Compound Annual Growth Rate (CAGR) of 4.2% from 2025 to 2033. This growth is fueled by increasing demand across diverse sectors, including semiconductor manufacturing, materials science research, and life sciences. Advancements in FIB-SEM technology, such as improved resolution, faster imaging speeds, and enhanced automation, are key drivers. The ability to perform high-precision 3D imaging and micro-fabrication makes FIB-SEMs indispensable for applications requiring detailed nanoscale analysis. The market is segmented by application (e.g., semiconductor failure analysis, materials characterization, biological sample imaging), and by geographic region, with North America and Europe currently dominating due to strong research infrastructure and a high concentration of leading companies such as Thermo Fisher Scientific, Hitachi High-Technologies Corporation, JEOL Ltd., Carl Zeiss, and Tescan Group. Competition is intense, with companies focusing on innovation and strategic partnerships to expand their market share. Despite the positive outlook, challenges remain. The high cost of FIB-SEM systems is a significant barrier to entry, particularly for smaller research institutions and companies in developing economies. Furthermore, the need for specialized expertise to operate and maintain these complex instruments presents a limitation. However, ongoing technological advancements, alongside the increasing availability of financing options and service contracts, are expected to mitigate these restraints gradually. The market is expected to witness considerable innovation in areas such as automation, higher throughput, and user-friendly software, leading to wider adoption and accessibility. The increasing adoption of advanced analytical techniques combined with the growing need for higher resolution imaging will contribute to the market's expansion.

In this project I work on developing ways to use a FIB-SEM to create a 3D model of biological samples. The method can be used in several projects with Grøn Dyst angles and I here report on my work on imaging malaria infected blood cells which is essential for a deeper understanding of how the parasite might be targeted by medicine, and algae samples that are essential for ecotoxicologial studies and later will be used for algae species used in biomass and biofuel production.

The entorhinal cortex (EC) is a brain region located on the anterior part of the medial temporal lobe which has been shown to be essential for memory functions and spatial navigation. Mapping the EC connectivity may contribute to the understanding of its structural design. One possible approach to decipher EC connectivity is its analysis at the ultrastructural level, using electron microscopy, to map synaptic contacts (synapses). Thus, a detailed ultrastructural analysis to map true synaptic contacts (or synapses) using 3D electron microscopy could contribute to a better understanding of the human cerebral cortex organization. We used Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) to perform a 3D analysis of the synapses in the neuropil in layers 1, 2 (subdivisions 2-is and 2-ni) and 3 of the medial Entorhinal Cortex (MEC). 3 human brain autopsies cases (AB2, AB7, and M16) have been used to obtain a total of 36 FIB/SEM valid image stacks. Specifically, we studied synaptic junctions, which were fully reconstructed in 3D. We analyzed the synaptic density, 3D spatial distribution, and type (excitatory and inhibitory), as well as the shape and size of each synaptic junction. Moreover, their postsynaptic targets were determined. Present data are intended to complete a detailed description of the synaptic organization of the human medial Entorhinal Cortex to better understand its functional organization.

This acquisition is part of the CellMap 2024 Segmentation ChallengeChallenge DOI: https://doi.org/10.25378/janelia.c.7456966Challenge Website: https://cellmapchallenge.janelia.org/Sample: Wild-type, interphase HeLa cell.Sample description: Understanding cellular architecture is essential for understanding biology. Electron microscopy (EM) uniquely visualizes cellular structure with nanometer resolution. However, traditional methods, such as thin-section EM or EM tomography, have limitations inasmuch as they only visualize a single slice or a relatively small volume of the cell, respectively. Here, we overcome these limitations by long-term imaging whole cells and tissues via the enhanced Focus Ion Beam Scanning Electron Microscopy (FIB-SEM) platform in high resolution mode with month-long acquisition duration. We use this approach to generate reference 3D image data sets at 4-nm isotropic voxels. Together with subsequent segmentation, we hope to create a reference library to explore comprehensive quantification of whole cells and all their constituents, thus addressing questions related to cell identities, cell morphologies, cell-cell interactions, as well as intracellular organelle organization and structure.HeLa cells, human cervical cancer cells that are the oldest and most commonly used cell line, are easily cultured and widely used in cell biology labs as a basic model to test diverse hypotheses. Having such cells imaged in their entirety can provide a reference to which perturbations in growth, genetic, environment, etc. can be compared. Here we present a typical 3D data set on the example of the entire HeLa cell. The mitochondrial network is clearly identified, as well as 2D cross-sections of standard cellular organelles, such as centrosome, Golgi apparatus, and nuclear envelope. Notably, every example illustrates the advantages of isotropic 3D imaging for cell biology. No single 2D cross-section allows visualizing all centriole sub-distal appendages, however quick segmentation of 3D data set characterizes them easily. Stereotypical 2D images of the Golgi stacks do not reveal the fenestration details and long thin tubular extensions, that can only be seen in 3D. Polyribosomal chains on the nuclear envelope are mostly hidden in 2D cross-sections but easily resolved and detailed in 3D. The unique ability of enhanced FIB-SEM to image whole cells and tissues at 4-nm isotropic voxels over large volumes makes it an ideal tool to map in toto the 3D ultrastructural relationship in living systems.Protocol: High pressure freezing, freeze-substitution resin embedding with 2% OsO4 0.1% UA 3% H2O in acetone; resin embedding in Eponate 12.Contributions: Sample provided by Aubrey Weigel (HHMI/Janelia), prepared for imaging by Gleb Shtengel (HHMI/Janelia), with imaging and post-processing by C. Shan Xu (HHMI/Janelia).Acquisition ID: jrc_hela-3Final voxel size (nm): 4.0 x 4.0 x 3.24 (X, Y, Z)Dimensions (µm): 50 x 4 x 39 (X, Y, Z)Imaging start date: 2017-08-09Imaging duration (days): 31Landing energy (eV): 1000Imaging current (nA): .25Scanning speed (MHz): .2Dataset URL: s3://janelia-cosem-datasets/jrc_hela-3/jrc_hela-3.zarr/recon-1/em/EM DOI: https://doi.org/10.25378/janelia.13114244Visualization Website: https://openorganelle.janelia.org/datasets/jrc_hela-3Publication: Xu et al., 2021, Heinrich et al., 2021

The global Focused Ion Beam Scanning Electron Microscope (FIB-SEM) system market is experiencing robust growth, projected to reach $578.3 million in 2025 and maintain a Compound Annual Growth Rate (CAGR) of 5.5% from 2025 to 2033. This expansion is driven by several key factors. Advancements in semiconductor technology necessitate higher resolution imaging and precise material modification at the nanoscale, fueling demand for FIB-SEM systems in research and development. The increasing adoption of FIB-SEM in life sciences, particularly for 3D cellular imaging and analysis, further contributes to market growth. Material science applications, such as failure analysis and characterization of new materials, also represent a significant market segment. The market is segmented by ion source type (Ga Ion Source and Non-Ga Ion Source) and application (Material Science, Life Sciences, and Semiconductor). Leading players like Thermo Fisher Scientific, Hitachi, Zeiss, JEOL Ltd, Tescan Group, and Raith are driving innovation and competition within this dynamic market. Geographical distribution reveals a strong presence across North America, Europe, and Asia Pacific, reflecting the concentration of research institutions and advanced manufacturing facilities in these regions. Growth in emerging markets, such as those in Asia Pacific and the Middle East & Africa, is anticipated to be significant in the coming years, driven by increasing investment in scientific research and technological advancement. While the market faces some restraints, such as the high cost of FIB-SEM systems and the need for specialized expertise for operation and maintenance, the overall growth trajectory remains positive, propelled by continuous technological innovations and the expanding applications of FIB-SEM across various scientific disciplines. The market is expected to see significant growth across all segments with the semiconductor industry and life sciences expected to be the most prominent growth drivers in the coming years.

3D x-ray tomography and 2D scanning electron microscopy (SEM) data behind the publications:

Salling, F.B, Jeppesen, N., Sonne, M.R., Hattel, J.H., Mikkelsen, L.P. Individual Fibre Inclination Segmentation from X-ray Computed Tomography using Principal Component Analysis, Journal of Composite Materials, 56, 83-98, https://doi.org/10.1177/00219983211052741, 2022.

to where the reference should be given if used.

Details on the data-set is given in the supplementary document found together with the data

The data-files is given for the two material case called Mock and UD. For each material case, the data is given as:

• .txm-files: 3D reconstructed x-ray scan files
  • FoV 2mm binning 2 (analyzed in the paper)
  • FoV 4mm binning 1 (additional data-set)
• 2Dtif.zip-files: 2D tif-stack version of the 3D reconstructed data-set
• .tif-files: stitched SEM scanning file used for fiber volume fraction determination
• .hdr-files: meta-data ASCII file behind the SEM scan
• tif.zip-files: The individual images behind the stitched SEM scanning file
• fig-files: digital form of the fibre trajectories colored according to their individual mean inclination used in figure xx in reference yy
• m-files: Matlab-script for calculating the fibre volume fraction (Vf) from the SEM image
• mat-files: Mat-file with the segmented part in the SEM image used for the Vf calculation