Showing papers on "Resolution (electron density) published in 2004"
TL;DR: It is demonstrated that datasets meeting these requirements can be obtained by automated block-face imaging combined with serial sectioning inside the chamber of a scanning electron microscope, opening the possibility of automatically obtaining the electron-microscope-level 3D datasets needed to completely reconstruct the connectivity of neuronal circuits.
Abstract: Three-dimensional (3D) structural information on many length scales is of central importance in biological research. Excellent methods exist to obtain structures of molecules at atomic, organelles at electron microscopic, and tissue at light-microscopic resolution. A gap exists, however, when 3D tissue structure needs to be reconstructed over hundreds of micrometers with a resolution sufficient to follow the thinnest cellular processes and to identify small organelles such as synaptic vesicles. Such 3D data are, however, essential to understand cellular networks that, particularly in the nervous system, need to be completely reconstructed throughout a substantial spatial volume. Here we demonstrate that datasets meeting these requirements can be obtained by automated block-face imaging combined with serial sectioning inside the chamber of a scanning electron microscope. Backscattering contrast is used to visualize the heavy-metal staining of tissue prepared using techniques that are routine for transmission electron microscopy. Low-vacuum (20–60 Pa H2O) conditions prevent charging of the uncoated block face. The resolution is sufficient to trace even the thinnest axons and to identify synapses. Stacks of several hundred sections, 50–70 nm thick, have been obtained at a lateral position jitter of typically under 10 nm. This opens the possibility of automatically obtaining the electron-microscope-level 3D datasets needed to completely reconstruct the connectivity of neuronal circuits.
1,506 citations
IBM1
TL;DR: The long relaxation time of the measured signal suggests that the state of an individual spin can be monitored for extended periods of time, even while subjected to a complex set of manipulations that are part of the MRFM measurement protocol.
Abstract: Magnetic resonance imaging (MRI) is well known as a powerful technique for visualizing subsurface structures with three-dimensional spatial resolution. Pushing the resolution below 1 micro m remains a major challenge, however, owing to the sensitivity limitations of conventional inductive detection techniques. Currently, the smallest volume elements in an image must contain at least 10(12) nuclear spins for MRI-based microscopy, or 10(7) electron spins for electron spin resonance microscopy. Magnetic resonance force microscopy (MRFM) was proposed as a means to improve detection sensitivity to the single-spin level, and thus enable three-dimensional imaging of macromolecules (for example, proteins) with atomic resolution. MRFM has also been proposed as a qubit readout device for spin-based quantum computers. Here we report the detection of an individual electron spin by MRFM. A spatial resolution of 25 nm in one dimension was obtained for an unpaired spin in silicon dioxide. The measured signal is consistent with a model in which the spin is aligned parallel or anti-parallel to the effective field, with a rotating-frame relaxation time of 760 ms. The long relaxation time suggests that the state of an individual spin can be monitored for extended periods of time, even while subjected to a complex set of manipulations that are part of the MRFM measurement protocol.
1,379 citations
TL;DR: An iterative phase retrieval method that uses a series of diffraction patterns, measured only in intensity, to solve for both amplitude and phase of the image wave function over a wide field of view and at wavelength-limited resolution is proposed.
Abstract: We propose an iterative phase retrieval method that uses a series of diffraction patterns, measured only in intensity, to solve for both amplitude and phase of the image wave function over a wide field of view and at wavelength-limited resolution. The new technique requires an aperture that is scanned to two or more positions over the object wave function. A simple implementation of the method is modeled and demonstrated, showing how the algorithm uses overlapping data in real space to resolve ambiguities in the solution. The technique opens up the possibility of practical transmission lensless microscopy at subatomic resolution using electrons, x rays, or nuclear particles.
707 citations
Journal Article•
TL;DR: The phase-shifting mask as mentioned in this paper consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite.
Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.
705 citations
TL;DR: Visualization of intra-retinal layers, especially the inner and outer segment of the photoreceptor layer, obtained by FDOCT was comparable to that, accomplished by ultrahigh resolution time domain OCT, despite an at least 40 times higher data acquisition speed of FD OCT.
Abstract: We present, for the first time, in vivo ultrahigh resolution (~2.5 μm in tissue), high speed (10000 A-scans/second equivalent acquisition rate sustained over 160 A-scans) retinal imaging obtained with Fourier domain (FD) OCT employing a commercially available, compact (500×260mm), broad bandwidth (120 nm at full-width-at-half-maximum centered at 800 nm) Titanium:sapphire laser (Femtosource Integral OCT, Femtolasers Produktions GmbH). Resolution and sampling requirements, dispersion compensation as well as dynamic range for ultrahigh resolution FD OCT are carefully analyzed. In vivo OCT sensitivity performance achieved by ultrahigh resolution FD OCT was similar to that of ultrahigh resolution time domain OCT, although employing only 2–3 times less optical power (~300 μW). Visualization of intra-retinal layers, especially the inner and outer segment of the photoreceptor layer, obtained by FDOCT was comparable to that, accomplished by ultrahigh resolution time domain OCT, despite an at least 40 times higher data acquisition speed of FD OCT.
529 citations
TL;DR: This paper demonstrates nanometer-localized multiple single-molecule (NALMS) fluorescence microscopy by using both centroid localization and photobleaching of the single fluorophores to validate the NALMS microscopy approach.
Abstract: Fitting the image of a single molecule to the point spread function of an optical system greatly improves the precision with which single molecules can be located. Centroid localization with nanometer precision has been achieved when a sufficient number of photons are collected. However, if multiple single molecules reside within a diffraction-limited spot, this localization approach does not work. This paper demonstrates nanometer-localized multiple single-molecule (NALMS) fluorescence microscopy by using both centroid localization and photobleaching of the single fluorophores. Short duplex DNA strands are used as nanoscale "rulers" to validate the NALMS microscopy approach. Nanometer accuracy is demonstrated for two to five single molecules within a diffraction-limited area. NALMS microscopy will greatly facilitate single-molecule study of biological systems because it covers the gap between fluorescence resonance energy transfer-based ( 100 nm) measurements of the distance between two fluorophores. Application of NALMS microscopy to DNA mapping with <10-nm (i.e., 30-base) resolution is demonstrated.
317 citations
TL;DR: The diffraction resolution barrier fundamentally is overcome on the basis of reversible saturable optical transitions, which might eventually allow us to investigate hitherto inaccessible details within live cells.
285 citations
TL;DR: In this paper, the use of slow-scan charge couple device cameras for phase identification and rapid determination of orientation image micrographs is reviewed, and a procedure for improving lattice spacing measurement by utilizing the full resolution of the camera is described with experimental measurements on silicon and nickel showing relative errors of plus/minus 3%.
Abstract: Ten years ago electron backscatter diffraction (EBSD) became available to a wider group active in materials research. This paper highlights some of the more significant developments in camera technology and software developments that have arisen since then. The use of slow-scan charge couple device cameras for phase identification and rapid determination of orientation image micrographs is reviewed. The current limiting spatial resolution of the technique is shown to be less than 10 nm. A procedure for improving lattice spacing measurement by utilizing the full resolution of the camera is described with experimental measurements on silicon and nickel showing relative errors of plus/minus 3%. An investigation of partially recrystallized aluminium shows how the recrystallized fraction can be extracted with confidence but that the mapping of substructure in the highly deformed regions is questionable. Phase identification is described for complex cases in which the phase data tabulated in standard databases do not correspond to what is observed in the EBSD patterns. Phase mapping in a complex mineral in which chemical data and EBSD data are collected simultaneously is shown to be improved by recording both the chemical and the EBSD data into computer memory and proceeding with the phase discrimination and orientation measurement in off-line analysis.
275 citations
TL;DR: A hybrid technique combining the ease of use and ability to see into cells of optical microscopy with the higher resolution of electron microscopy is presented, indicating a potential for multilabeling and specific scintillating markers.
Abstract: A capability for scanning electron microscopy of wet biological specimens is presented. A membrane that is transparent to electrons protects the fully hydrated sample from the vacuum. The result is a hybrid technique combining the ease of use and ability to see into cells of optical microscopy with the higher resolution of electron microscopy. The resolution of low-contrast materials is approximately 100 nm, whereas in high-contrast materials the resolution can reach 10 nm. Standard immunogold techniques and heavy-metal stains can be applied and viewed in the fluid to improve the contrast. Images present a striking combination of whole-cell morphology with a wealth of internal details. A possibility for direct inspection of tissue slices transpires, imaging only the external layer of cells. Simultaneous imaging with photons excited by the electrons incorporates data on material distribution, indicating a potential for multilabeling and specific scintillating markers.
244 citations
TL;DR: The systematic exploitation of anisotropic thermal expansion will help reduce the effects of peak overlap in the analysis of powder diffraction data.
Abstract: The optical design and performance of the high-resolution powder diffraction beam line BM16 at ESRF are discussed and illustrated. Some recent studies carried out on BM16 are described, including crystal structure solution and refinement, anomalous scattering, in situ measurements, residual strain in engineering components, investigation of microstructure, and grazing-incidence diffraction from surface layers. The beam line is built on a bending magnet, and operates in the energy range from 5 keV to 40 keV. After the move to an undulator source in 2002, it will benefit from an extented energy range up to 60 keV and increased flux and resolution. It is anticipated that enhancements to the data quality will be achieved, leading to the solution of larger crystal structures, and improvements in the accuracy of refined structures. The systematic exploitation of anisotropic thermal expansion will help reduce the effects of peak overlap in the analysis of powder diffraction data.
239 citations
TL;DR: The structures were determined to be dominantly cubic, but each undergoes different dynamics after the ultrafast substrate temperature jump, and changes in local bond distances with time elucidated the structural changes in the far-from-equilibrium regime at short times and near-equilibration at long times.
Abstract: We report direct determination of the structures and dynamics of interfacial water on a hydrophilic surface with atomic-scale resolution using ultrafast electron crystallography. On the nanometer scale, we observed the coexistence of ordered surface water and crystallite-like ice structures, evident in the superposition of Bragg spots and Debye-Scherrer rings. The structures were determined to be dominantly cubic, but each undergoes different dynamics after the ultrafast substrate temperature jump. From changes in local bond distances (OH··O and O···O) with time, we elucidated the structural changes in the far-from-equilibrium regime at short times and near-equilibration at long times.
TL;DR: A method for high-resolution scintillation detection is described that eliminates the depth-of-interaction problem encountered with pinhole cameras, and is expected to provide intrinsic detector resolutions better than 150 microm.
Abstract: Exciting new SPECT systems can be created by combining pinhole imaging with compact high-resolution gamma cameras. These new systems are able to solve the problem of the limited sensitivity-resolution trade-off that hampers contemporary small animal SPECT. The design presented here (U-SPECT-III) uses a set of detectors placed in a polygonal configuration and a cylindrical collimator that contains 135 pinholes arranged in nine rings. Each ring contains 15 gold pinhole apertures that focus on the centre of the cylinder. A non-overlapping projection is acquired via each pinhole. Consequently, when a mouse brain is placed in the central field-of-view, each voxel in the cerebrum can be observed via 130 to 135 different pinholes simultaneously. A method for high-resolution scintillation detection is described that eliminates the depth-of-interaction problem encountered with pinhole cameras, and is expected to provide intrinsic detector resolutions better than 150 ?m. By means of simulations U-SPECT-III is compared to a simulated dual pinhole SPECT (DP-SPECT) system with a pixelated array consisting of 2.0 ? 2.0 mm NaI crystals. Analytic calculations indicate that the proposed U-SPECT-III system yields an almost four times higher linear and about sixty times higher volumetric system resolution than DP-SPECT, when the systems are compared at matching system sensitivity. In addition, it should be possible to achieve a 15 up to 30 times higher sensitivity with U-SPECT-III when the systems are compared at equal resolution. Simulated images of a digital mouse-brain phantom show much more detail with U-SPECT-III than with DP-SPECT. In a resolution phantom, 0.3 mm diameter cold rods are clearly visible with U-SPECT-III, whereas with DP-SPECT the smallest visible rods are about 0.6?0.8 mm. Furthermore, with U-SPECT-III, the image deformations outside the central plane of reconstruction that hamper conventional pinhole SPECT are strongly suppressed. Simulation results indicate that future pinhole SPECT systems are likely to bring about significant improvements in radio-molecular imaging of small animals.
TL;DR: A reconstruction of native GroEL by electron cryomicroscopy (cryo-EM) and single particle analysis at 6 A resolution and a measurable shift in the positions of three alpha helices in the intermediate domain is observed, not consistent with any of the 7 monomeric structures in the Protein Data Bank model (1OEL).
TL;DR: Practical non‐linear microscopes do approach their theoretical resolution and therefore show no resolution disadvantage relative to confocal microscopes in spite of the longer excitation wavelength.
Abstract: Calculated and measured resolution figures are presented for confocal microscopes with different pinhole sizes and for nonlinear (2-photon and second harmonic) microscopes. A modest degree of super-resolution is predicted for a confocal microscope but in practice this is not achievable and confocal fluorescence gives little resolution improvement over widefield. However, practical non-linear microscopes do approach their theoretical resolution and therefore show no resolution disadvantage relative to confocal microscopes in spite of the longer excitation wavelength.
TL;DR: This method, slow electron velocity-map imaging, provides spectral line widths of better than 1 meV, providing a dramatic reduction of data acquisition time compared to other techniques with comparable resolution.
Abstract: A technique for high resolution anion photodetachment spectroscopy is presented that combines velocity map imaging and anion threshold photodetachment. This method, slow electron velocity-map imaging, provides spectral line widths of better than 1 meV. Spectra over a substantial range of electron kinetic energies are recorded in a single image, providing a dramatic reduction of data acquisition time compared to other techniques with comparable resolution. We apply this technique to atomic iodine and the van der Waals cluster I.CO2 as test systems, and then to the prereactive Cl.D2 complex where partially resolved structure assigned to hindered rotor motion is observed.
TL;DR: In this paper, a theoretical analysis of how intense, few-cycle infrared laser pulses can be used to image the structure of small molecules with nearly 1 fs temporal and sub-A spatial resolution.
Abstract: We present a theoretical analysis of how intense, few-cycle infrared laser pulses can be used to image the structure of small molecules with nearly 1 fs temporal and sub-A spatial resolution. We identify and analyse several physical mechanisms responsible for the distortions of the diffraction image and describe a recipe for recovering an un-distorted image from angle and energy-resolved electron spectra. We also identify holographic patterns in the photoelectron spectra and discuss the requirements to enhancing the hologram resolution for imaging the scattering potential.
Book•
01 Jun 2004Abstract: Introduction Non-singularity and resolution of singularities Curve singularities Resolution type theorems Surface singularities Resolution of singularities in characteristic zero Resolution of surfaces in positive characteristic Local uniformization and resolution of surfaces Ramification of valuations and simultaneous resolution Smoothness and non-singularity Bibliography Index.
TL;DR: It is demonstrated that the degree of over-fitting is reduced with a weighting scheme that depends on the signal-to-noise ratio in the data, which improves the accuracy of resolution measurement by the commonly used Fourier shell correlation.
TL;DR: A simple method to estimate the coherently scattered signal as a function of resolution is presented, and it is shown that the required X-ray flux or dose scales as the inverse third power of resolution for a specimen of constant volume and density.
Abstract: Coherent diffractive imaging using a coherent X-ray source promises to be a useful microscopic method for imaging noncrystalline objects at high spatial resolution. In this article a simple method to estimate the coherently scattered signal as a function of resolution is presented, and it is shown that the required X-ray flux or dose scales as the inverse third power of resolution for a specimen of constant volume and density. A simulated case study using the proposed energy-recovery linac source is also presented, which confirms the estimated flux requirement.
TL;DR: The resolution among Pseudomonas taxa based on the combined data set analysis of the different lineages increased due to a synergistic effect of the individual data sets, and the taxonomic status of biovars of P. putida is discussed.
Abstract: A study of representatives of the bacterial genus Pseudomonas, analysing a combined data set of four molecular sequences with completely different properties and evolutionary constraints, is reported. The best evolutionary model was obtained with a hierarchical hypothesis testing program to describe each data set and the combined data set is presented and analysed under the likelihood criterion. The resolution among Pseudomonas taxa based on the combined data set analysis of the different lineages increased due to a synergistic effect of the individual data sets. The unresolved fluorescens lineage, as well as other weakly supported lineages in the single data set trees, should be revised in detail at the biochemical and molecular level. The taxonomic status of biovars of P. putida is discussed.
DOI•
04 Jun 2004
TL;DR: In this article, the authors dealt with the multi-dimensional reconstruction of the earth's conductivity distribution based on DC resistivity data, which represents a nonlinear and ill-posed minimization problem with many degrees of freedom.
Abstract: The presented thesis deals with the multi-dimensional reconstruction of the earth’s conductivity distribution based on DC resistivity data. This task represents a nonlinear and ill-posed minimization problem with many degrees of freedom. In this work, techniques for regularization and controlling of this problem are depicted and classified. Particularly, it is concentrated on explicit regularization types, which impose constraints onto the model. The system of equations as resulting from the application of the Gauss-Newton minimization can be solved efficiently. Furthermore, it is shown how the regularization strength can be controlled. The method of non-linear resolution analysis plays a central role in the thesis. It represents a powerful tool to estimate the quality of inversion results. Furthermore, the derived resolution measures provide the basis for the optimization of experimental design concerning information content and efficiency. Methods of error estimation, forward modeling and the calculation of the Jacobian matrix for DC resistivity data are developed. Procedures for appropriate parameterization and inversion control are pointed out by studies of synthetic models. Different inversion and regularization methods are examined in detail. A linearized study is used to compare different data sets considering their efficiency. Moreover, a triplegrid-technique for the incorporation of topography into three-dimensional inversion is presented. Finally the inversion methods are applied to field data. The depicted optimization strategies are realized in practice, which increases the economic relevance of threedimensional data acquisition. The structure of the subsurface is imaged in detail for several applications in the fields of cavity detection, archaeology and the investigation of ground falls. The resolution analysis is successfully established to appraise the obtained results.
TL;DR: It is shown that the performance of NSOM can be extended to measurements in liquid environments using a diving bell concept and, for the first time, individual fluorescent molecules on the membrane of cells in solution are imaged with a spatial resolution of 90 nm.
TL;DR: In this paper, the authors present a technique of scanning electron microscopy that is adapted to the study of wet samples, where the wet environment is protected in a small chamber enclosed by a membrane, which is thin enough for energetic electrons to go through and interact with the sample studied.
Abstract: We present a technique of scanning electron microscopy that is adapted to the study of wet samples. The wet environment is protected in a small chamber enclosed by a membrane, which is thin enough for energetic electrons to go through and interact with the sample studied. We detail both the technique and the general mechanisms of signal formation in the imaging of samples through a membrane. We first describe our setup and the properties required for the membrane, the main element in this method. Some simple measurements for its characterization are given, guiding the choice of material and thickness. We then go on to describe the capabilities of the technique in imaging a variety of different samples. We evaluate the accessible contrast and resolution, and the current needed to obtain them. Low contrast samples can be imaged with an improvement in resolution over optical microscopy. High contrast samples like gold markers labeling a biological cell can be imaged with a resolution of the order of 10 nm. The resolution depends on the location of the particle in the sample: the closer to the membrane, the better the resolution. We believe such a result opens up potential applications for routine experiments in biology, and expect this new technique to find numerous applications in domains where liquid samples are investigated such as soft materials science.
TL;DR: In this article, a peak-fit analysis of Cr 2p XPS spectra of Cr(III) compounds is proposed, based on the experimental and theoretical work of other authors.
Abstract: By using modern XPS systems it is possible to obtain spectra with well-resolved spin orbit, multiplet and field splitting even with powder samples mounted using adhesive tape. Measurement of Cr2O3 powder with the latest generation of XPS spectrometers, which are able to analyse non-conductive powders with ultimate energy resolution, revealed multiplet splitting features and satellite emission in the Cr 2p spectrum. Therefore, peak-fit analysis of Cr 2p XPS spectra of Cr(III) compounds requires a more appropriate approach and common practice has to be reconsidered. One possible way to analyse this spectrum is proposed, based on the experimental and theoretical work of other authors. Copyright © 2004 John Wiley & Sons, Ltd.
TL;DR: In this article, 3D transmission electron microscopy (3D-TEM) combined with electron tomography was used to visualize and evaluate structural characteristics in 3D space, such as the size and volume of in situ silica generated in the NR matrix by the sol-gel reaction of tetraethoxysilane, at nanometer scale resolution.
Abstract: Summary: Three dimensional (3D) nanostructures of particulate silicas in natural rubber (NR) were observed for the first time by use of 3D transmission electron microscopy (3D-TEM) combined with electron tomography The method enabled us to visualize and evaluate structural characteristics in 3D space, such as the size and the volume of in situ silica generated in the NR matrix by the sol-gel reaction of tetraethoxysilane, at nanometer scale resolution
The reconstructed mass density view of the silica in an in situ silica-filled natural rubber vulcanizate, as determined by 3D-TEM
TL;DR: It is shown that the number of pixels in elemental images determines not only the lateral resolution but also the depth resolution, which contributes to depth-of-focus degradation in three-dimensional integral imaging (II).
Abstract: We present the effects of a finite number of pixels in elemental images on the resolution and the depth of focus in three-dimensional integral imaging (II). We show that the number of pixels in elemental images determines not only the lateral resolution but also the depth resolution. The minimum number of pixels required in each elemental image is calculated to avoid depth-of-focus degradation. We evaluate how II system performance degrades as the number of pixels in each elemental image changes. The product of the depth of focus and the lateral resolution squared is used as the performance metric.
TL;DR: In this paper, the authors used scanning and transmission electron microscopy (SEM) to image hundreds of single-wall carbon nanotube probes and to correlate probe morphology with AFM image resolution.
Abstract: Scanning and transmission electron microscopy were used to image hundreds of single-wall carbon nanotube probes and to correlate probe morphology with AFM image resolution. Several methods for fabricating such probes were evaluated, resulting in a procedure that produces image-quality single-wall nanotube probes at a rate compatible with their routine use. Surprisingly, about one-third of the tips image with resolution better than the nanotube probe diameter and, in exceptional cases, with resolution better than 1 nm. This represents the highest lateral resolution reported to date for a SWNT probe.
TL;DR: In this paper, XMM-Newton observations of the young (~2-5 Myr) cluster around the hot (O9.5V) star sigma Orionis AB, aimed at obtaining a high resolution RGS spectrum of the hot star as well as EPIC imaging data for the whole field.
Abstract: We present XMM-Newton observations of the young (~2-5 Myr) cluster around the hot (O9.5V) star sigma Orionis AB, aimed at obtaining a high resolution RGS spectrum of the hot star as well as EPIC imaging data for the whole field. We show that the RGS spectrum of sigma Ori AB may be contaminated by weaker nearby sources which required the development of a suitable procedure to extract a clean RGS spectrum and to determine the thermal structure and wind properties of the hot star. We also report on the detection of a flare from the B2Vp star sigma Ori E and we discuss whether the flare originated from the hot star itself or rather from an unseen late-type companion. Other results of this observation include: the detection of 174 X-ray sources in the field of sigma Ori of which 75 identified as cluster members, including very low-mass stars down to the substellar limit; the discovery of rotational modulation in a late-type star near sigma Ori AB; no detectable line broadenings and shifts (<800 km s^-1) in the spectrum of sigma Ori AB together with a remarkable low value of the O VII forbidden to intercombination line ratio and unusually high coronal abundances of CNO elements.
01 Oct 2004-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the quality of a given 3D-data set, i.e. the tomogram of stained biological cells seeded on a polymer multifilament yarn in phosphate buffered saline, can be optimized with respect to the product of spatial and density resolution.
Abstract: The quality of the X-ray tomogram not only depends on the spatial resolution but also on the density resolution or contrast. Based on the theory of [Nucl. Instr. and Meth. 206 (1983) 541] it is concluded that the density resolution can be substantially improved by merging of pixels, referred to as binning, prior to reconstruction. We demonstrate that the quality of a given 3D-data set, i.e. the tomogram of stained biological cells seeded on a polymer multifilament yarn in phosphate buffered saline, can be optimized with respect to the product of spatial and density resolution – the image quality factor. This procedure improves or even enables the visualization and quantification of selected constituents in the tomogram.