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Biomedical subjects

Frédérique Frouin

Publications and source records attributed to Frédérique Frouin.

At least 19 recordsLinked to original sources
PubMed2006

An automated image-processing strategy to analyze dynamic arterial spin labeling perfusion studies. Application to human skeletal muscle under stress.

Arterial spin labeling (ASL) perfusion measurements allow the follow-up of muscle perfusion with high temporal resolution during a stress test. Automated image processing is proposed to estimate perfusion maps from ASL images. It is based on two successive analyses: at first, automated rejection of the image pairs between which a large displacement is detected is performed, followed by factor analysis of the dynamic data and cluster analysis to classify pixels with large signal variation characteristic of vessels. Then, after masking these "vascular" pixels, factor analysis and cluster analysis are further applied to separate the different muscles between low or high perfusion increase, yielding a functional map of the leg. Data from 10 subjects (five normal volunteers and five elite sportsmen) had been analyzed. Resulting time perfusion curves from a region of interest (ROI) in active muscles show a good accordance whether extracted with automated processing or with manual processing. This method of functional segmentation allows automated suppression of vessels and fast visualization of muscles with high, medium or low perfusion, without any a priori knowledge.

Adult↗
PubMed2006

Analysis of CD36 expression on human monocytic cells and atherosclerotic tissue sections with quantum dots: investigation by flow cytometry and spectral imaging microscopy.

OBJECTIVE: To demonstrate CD36 expression with quantum dots (QDs) 525 and/or 605 on human monocytic U937 cells and atherosclerotic tissue sections by means of flow cytometry (FCM) and/or confocal laser scanning microscopy (CLSM). STUDY DESIGN: U937 cells and tissue sections were analyzed by means of FCM and/or CLSM. FCM was performed, using different ultraviolet (UV) and visible (488/532 nm) excitation modes. In the visible mode, fluorescence intensities of QDs, phycoerythrin (PE) and fluorescein isothiocyanate (FITC) were compared. Three-dimensional (3-D) sequences of images were obtained by spectral analysis in a CLSM and analyzed by the factor analysis of medical image sequences (FAMIS) algorithm, providing factor curves and images. Factor images are the result of the FAMIS image processing method, which differentiates emission spectra from 3D sequences of images. In CLSM analysis, preparations are screened in a UV excitation mode to optimize the possibilities of QDs and have the benefit of 4',6-diamino-2-phenylindole or Hoechst 33342 counterstaining of nuclei. RESULTS: FCM and CLSM revealed CD36 expression by means of QDs 525 and/or 605. Fluorescence intensity of PE and of FITC was higher than that of QDs 525 and of 605. As factor curves and images show the red emission of QDs 605 only, subsequent reliable identification and localization of CD36 was obtained. CONCLUSION: QDs 525 and 605 are useful to analyze antigenic expression. Following FCM, which is well adapted to detect fluorescence emission of QDs in the UV or visible excitation mode, CLSM and subsequent spectral analysis assess more specific characterization of QD fluorescent emissions.

Arteries↗
PubMed2006

Flow cytometry and spectral imaging multiphoton microscopy analysis of CD36 expression with quantum dots 605 of untreated and 7-ketocholesterol-treated human monocytic cells.

OBJECTIVE: To evaluate CD36 expression with quantum dots 605 (QDs 605) on untreated and 7-ketocholesterol (7KC)-treated monocytic U937 cells by flow cytometry (FCM) and confocal and multiphoton laser scanning microscopy (CLSM). STUDY DESIGN: Cells were analyzed by CLSM, following flow cytometric quantification of CD36 expression and 7KC uptake. Image sequences were obtained by spectral analysis in monophoton and multiphoton CLSM and analyzed by the factor analysis of medical image sequences (FAMIS) algorithm to differentiate emission spectra. In CLSM analysis, cell deposits were screened in ultraviolet excitation modes to optimize the possibilities of QDs 605 and have the benefit of nuclei counterstaining by DAPI. RESULTS: FCM and CLSM reveal the expression of CD36 by means of QDs 605. FCM provides information on 7KC uptake. CLSM provides the localization of 7KC vs. DAPI. As factor curves and images show the red, narrow emission of QDs 605 vs. violet and blue emissions of 7KC and DAPI, respectively, a reliable identification of CD36 is obtained. CONCLUSION: QDs 605 are useful tools to perform antigenic expression in FCM and CLSM. Moreover, CLSM and subsequent spectral analysis provide a more specific characterization of QDs 605 fluorescent emission in the UV excitation mode and a simultaneous identification of 7KC.

Algorithms↗
PubMed2005

7-Ketocholesterol favors lipid accumulation and colocalizes with Nile Red positive cytoplasmic structures formed during 7-ketocholesterol-induced apoptosis: analysis by flow cytometry, FRET biphoton spectral imaging microscopy, and subcellular fractionation.

BACKGROUND: Oxidized low-density lipoproteins play key roles in atherosclerosis. Their toxicity is at least in part due to 7-ketocholesterol (7KC), which is a potent inducer of apoptosis. In this study on human promonocytic U937 cells, we determined the effects and the interactions of 7KC with cellular lipids during 7KC-induced apoptosis. METHODS: Morphologic and functional changes were investigated by microscopic and flow cytometric methods after staining with propidium iodide, 3,3'-dihexyloxacarbocyanine iodide, and Hoechst 33342. Cellular lipid content was identified by using filipin to quantify free cholesterol and Nile Red (NR), which emit a yellow or orange-red fluorescence in the presence of neutral and polar lipids, respectively. After staining with NR, interactions of 7KC with cellular lipids were identified by fluorescence resonance energy transfer biphoton spectral imaging confocal microscopy and by subcellular fractionation, gas chromatography, and mass spectrometry. RESULTS: During 7KC-induced apoptosis the fluorescence from filipin and the ratio of measured (orange-red vs. yellow) fluorescence of NR were enhanced. Spectral analysis of images obtained in biphoton mode and resulting factor images demonstrated the occurrence of fluorescence resonance energy transfer between 7KC and NR and the subsequent colocalization of 7KC and NR. These data were in agreement with biochemical characterization and demonstrated that 7KC and neutral and polar lipids accumulate in NR-stained cytoplasmic structures. CONCLUSIONS: During 7KC-induced apoptosis, 7KC modifies the cellular content of neutral and polar lipids, favors free cholesterol accumulation, and colocalizes with neutral and polar lipids that are inside NR-stained cytoplasmic structures.

Apoptosis↗
PubMed2005

New criteria for assessing fit quality in dynamic contrast-enhanced T1-weighted MRI for perfusion and permeability imaging.

Contrast-enhanced (CE) MRI provides in vivo physiological information that cannot be obtained by conventional imaging methods. This information is generally extracted by using models to represent the circulation of contrast agent in the body. However, the results depend on the quality of the fit obtained with the chosen model. Therefore, one must check the fit quality to avoid working on physiologically irrelevant parameters. In this study two dimensionless criteria-the fraction of modeling information (FMI) and the fraction of residual information (FRI)-are proposed to identify errors caused by poor fit. These are compared with more conventional criteria, namely the quadratic error and the correlation coefficient, both theoretically and with the use of simulated and real CE-MRI data. The results indicate the superiority of the new criteria. It is also shown that these new criteria can be used to detect oversimplified models.

Algorithms↗
PubMed2005

Optimization of factor analysis of the left ventricle in echocardiography for detecting wall motion abnormalities.

This study has tested solutions to optimize the ability of factor analysis of the left ventricle in echocardiography (FALVE) to detect segmental wall motion abnormalities automatically. On four- and two-chamber views of 38 patients, two factors (one flat curve and one curve describing the contraction-relaxation sequence) were extracted and associated factor images were combined to synthesize a parametric image (constant image in green, positive/negative values of the contraction-relaxation image in red/blue). The segments were graded on the visual and the parametric views. The impact of selecting a whole cardiac cycle, masking the left ventricle and realigning the image sequence on the results, was demonstrated. Systematic realignment had a positive impact, especially for patients with left bundle branch block or pacemaker. After alignment, for the entire population, the absolute concordance was 68.6% and the relative concordance (within one grade) was 99%. Thus, FALVE is promising for detecting segmental wall motion abnormalities.

Adult↗
PubMed2004

Factor analysis of the left ventricle by echocardiography (FALVE): a new tool for detecting regional wall motion abnormalities.

BACKGROUND: Factor analysis of the left ventricle in echography was developed to study the regional wall motion. Two factors and associated factor images were estimated using specific constraints: one "constant" factor and another "contraction-relaxation" factor. The constant factor was encoded in green, the positive component of the contraction in red and the negative in blue. METHODS: The evaluation was carried out on 12 patients with LBBB or pacemaker (group A), and on 26 others (group B). The segments were graded separately on the cine-loops by three experienced echocardiographers. Similarly, the three-color combination of the factor images was read at the endocardial border and each segment was scored. RESULTS: An absolute concordance was obtained for 64.8% of the segments and a relative concordance (within one grade) for 97.2%. They were 71% and 99.6% in group B. Most of the discordant cases were explained by the global motion during the cardiac cycle. The standard deviation of the difference between the mean wall motion scores was 0.38 for all the patients; it was reduced to 0.30 in group B. CONCLUSION: Factor analysis is a promising tool to study the regional wall motion. It might become useful for assessing segmental wall motion in 2D and 3D echo.

Artifacts↗
PubMed2004

Ultrasound elastography based on multiscale estimations of regularized displacement fields.

Elasticity imaging is based on the measurements of local tissue deformation. The approach to ultrasound elasticity imaging presented in this paper relies on the estimation of dense displacement fields by a coarse-to-fine minimization of an energy function that combines constraints of conservation of echo amplitude and displacement field continuity. The multiscale optimization scheme presents several characteristics aimed at improving and accelerating the convergence of the minimization process. This includes the nonregularized initialization at the coarsest resolution and the use of adaptive configuration spaces. Parameters of the energy model and optimization were adjusted using data obtained from a tissue-like phantom material. Elasticity images from normal in vivo breast tissue were subsequently obtained with these parameters. Introducing a smoothness constraint into motion field estimation helped solve ambiguities due to incoherent motion, leading to elastograms less degraded by decorrelation noise than the ones obtained from correlation-based techniques.

Algorithms↗
PubMed2004

Multiple excitation confocal analysis of targets in nuclei of cytogenetic preparations.

OBJECTIVE: To demonstrate that cellular preparations requiring color analysis of different domains stained by molecular cytogenetic methods (fluorescence in situ hybridization) can be processed by spectral analysis of fluorescent emissions by either factor analysis of medical image sequences (FAMIS) or a META confocal configuration to isolate fluorescent probes. STUDY DESIGN: Three-dimensional sequences of images obtained by spectral analysis in a META confocal microscope (Carl Zeiss SAS, Jena, Germany) were analyzed by META processing and the FAMIS algorithm, which provides factor curves. META and factor images were then the result of image-processing methods that cover emission spectra. RESULTS: Factor curves and factor or META images can help to analyze targets inside nuclei. CONCLUSION: It is possible to process preparations containing numerous spots on different colors to differentiate stained targets and to improve visualization and detection.

Carcinoma, Renal Cell↗
PubMed2004

Analysis of the fluorescence of monodansylcadaverine-positive cytoplasmic structures during 7-ketocholesterol-induced cell death.

OBJECTIVE: To analyze multilamellar cytoplasmic structures by confocal laser scanning microscopy (CLSM) combined with factor analysis of biomedical image sequences (FAMIS). STUDY DESIGN: After treatment of U937 cells with 7-ketocholesterol (7-keto), cytoplasmic alterations were assessed with monodansylcadaverine (MDC). By ultraviolet excitation of a confocal laser scanning microscope (UV-CLSM), spectral sequences were performed to characterize 7-keto and MDC distribution inside cells. FAMIS was used to transform the image sequences in factor curves and images. RESULTS: By UV-CLSM, 7-keto fluorescence was detected together with MDC, which revealed morphologic cytoplasmic changes in cells. The factor images obtained from confocal image sequences emphasized the view of these results. These data are in agreement with biochemical characterizations of MDC-positive structures. CONCLUSION: The combined use of confocal microscopy and FAMIS allowed us to detect MDC-positive cytoplasmic structures in 7-keto-treated cells and to colocalize MDC and 7-keto distribution. This new method confirms the usefulness of MDC as a marker of oxysterol-induced cell death.

Benzimidazoles↗
PubMed2004

Analysis of fluorescent MRI contrast agent behavior in the liver and thoracic aorta of mice.

OBJECTIVE: To characterize the behavior of magnetofluorescent products injected in mice intravenously. STUDY DESIGN: The magnetic resonance imaging (MRI) products were labelled with fluorescent molecules to examine the biodistribution process in vivo and observe them at the cellular level by means of confocal microscopy. Three-dimensional (3D) sequences of images were obtained by spectral analysis of sample preparations in a multiphoton confocal microscope and analyzed by the factor analysis of medical image sequence algorithm, which provides factor curves. Factor images are the result of image-processing methods that utilize information from emission spectra. Preparations are also screened in the counting mode to provide fluorescent lifetime imaging microscopy (FLIM) characterizations. RESULTS: Factor images and FLIM images can help to analyze MRI targeting inside the liver and thoracic aorta of mice. They show positive detection of Fe-Texas red and BOPTA-Eu in the liver and positive detection of Fe-Texas red and negative detection of BOPTA-Eu inside the thoracic aorta. CONCLUSION: This investigation established the utility of fluorescent MRI contrast agents as in vivo staining tools for cellular sites.

Algorithms↗
PubMed2004

FRET multiphoton spectral imaging microscopy of 7-ketocholesterol and Nile Red in U937 monocytic cells loaded with 7-ketocholesterol.

OBJECTIVE: To show the effect of 7-ketocholesterol (7KC) on cellular lipid content by means of flow cytometry and the interaction of 7KC with Nile Red (NR) via ultraviolet fluorescence resonance energy transfer (FRET) excitation of NR on U937 monocytic cells by means of 2-photon excitation confocal laser scanning microscopy (CLSM). STUDY DESIGN: Untreated and 7KC-treated U937 cells were stained with NR and analyzed by flow cytometry and CLSM. 3D sequences of images were obtained by spectral analysis in a 2-photon excitation CLSM and analyzed by the factor analysis of medical image sequences (FAMIS) algorithm, which provides factor curves and images. Factor images are the result of the FAMIS image processing method, which handles emission spectra. In FRET analysis, preparations are screened at selected UV wavelengths to avoid emission of NR in the absence of 7KC. RESULTS: During 7KC-induced cell death,flow cytometry and CLSM revealed a modification of the cellular lipid content. Factor images show FRET occurrence and subsequent colocalization of 7KC and NR. CONCLUSION: This investigation established the utility of 2-photon excitation CLSM to assess colocalization of 7KC with NR by FRET and to identify and distinguish polar and neutral lipids stained by NR that accumulate from the effect of 7KC.

Cell Death↗
PubMed2003

Using an adaptive semiautomated self-evaluated registration technique to analyze MRI data for myocardial perfusion assessment.

PURPOSE: To validate the adaptive semiautomated self-evaluated registration technique (ASSERT) followed by factor analysis of medical image sequence (FAMIS) for analyzing myocardial perfusion using magnetic resonance imaging (MRI) images. MATERIALS AND METHODS: Eleven patients having a significant stenosis of at least one coronary artery detected by coronarography were examined by thallium tomoscintigraphy and perfusion MRI (first-pass of Gd-DTPA-BMA) at rest and under pharmacologic stress. The MRI images were analyzed by ASSERT to correct for rigid motion in the acquisition plane and to reject those images that were severely deformed or acquired outside the slice plane. The images thus obtained were analyzed by FAMIS. The resulting factor images representing myocardial perfusion were read to identify the ischemic territories corresponding to left anterior descending coronary arteries and right coronary arteries. RESULTS: ASSERT allowed automatic correction for motion and the exclusion of images that could not be registered. The ischemic territories, identified from the factor images of the myocardium, agreed with those identified by coronarography and tomoscintigraphy for 20 of the 22 territories. CONCLUSION: The results demonstrate the feasibility of analyzing myocardial perfusion using MRI acquisition and treating the resulting images by ASSERT and FAMIS. Extending this method to multislice examinations will enable evaluation of the perfusion of the whole myocardium.

Aged↗
PubMed2002

Factor analysis of medical image sequences improves evaluation of first-pass MR imaging acquisitions for myocardial perfusion.

RATIONALE AND OBJECTIVES: Factor analysis of medical image sequences (FAMIS) applied to gadolinium chelate-enhanced subsecond magnetic resonance (MR) imaging was evaluated as a postprocessing method for assessing myocardial perfusion in coronary artery disease (CAD). MATERIALS AND METHODS: To assess the accuracy of motion correction, five normal volunteers underwent MR imaging at rest. Thirteen patients with well-documented CAD and no myocardial infarction underwent MR imaging at rest and after dipyridamole administration. After motion correction, a single myocardial tissue factor (FAMISt) image was obtained with FAMIS for each raw MR imaging series acquisition. To evaluate how FAMIS could improve the analysis of these acquisitions, five readers visually assessed myocardial perfusion with FAMISt and raw MR images, and a multicase, multireader receiver operating characteristic analysis was performed. RESULTS: FAMISt images significantly improved detection of the perfusion defects when compared with raw MR images (P = .002). Areas under the receiver operating characteristic curves ranged from 0.84 to 0.93 with FAMISt images and from 0.48 to 0.85 with raw MR images. CONCLUSION: FAMIS applied to first-pass MR imaging series provided myocardial perfusion images that improve the objective assessment of myocardial perfusion in patients with CAD.

Adult↗
PubMed2002

Improved confocal characterization of targets in nuclei of cytogenetic preparations.

OBJECTIVE: To show that cellular preparations requiring depth analysis of different domains stained by molecular cytogenetic methods (fluorescence in situ hybridization and primed in situ) can be improved by regularized factor analysis of medical image sequences (FAMIS) to isolate fluorescent probes by means of intensity depth profiles of fluorochromes, to track relevant DNA sequences (cosmids and centromeres) in cell nuclei during interphase and to improve the use of cytogenetic techniques resulting in flat preparations of whole cells that are assumed to preserve probe access to their targets. STUDY DESIGN: 3D sequences of images obtained by depth displacement in a confocal microscope were first analyzed by the FAMIS algorithm, which provides factor curves. Factor images then resulted from regularization methods that improve signal/noise ratio while preserving target contours. RESULTS: Factor curves and regularized factor images helped analyze targets inside nuclei. CONCLUSION: It is possible to process preparations containing numerous spots (even when they are on different planes) to differentiate stained targets, to investigate depth differences and to improve visualization and detection.

Cell Nucleus↗
PubMed2002

Distribution of injected MRI contrast agents in mouse livers studied by confocal and SIMS microscopy.

OBJECTIVE: To localize magnetic resonance imaging (MRI) contrast agents injected intravenously into mouse livers. STUDY DESIGN: Parallel studies were performed on fluorescent europium and nonfluorescent, paramagnetic gadolinium and on a product combining nanoparticles of Fe and Texas Red to obtain combined information on the distribution of these molecules inside the liver. The distribution of different superparamagnetic iron oxides was also studied because the size of these new compounds is not always convenientfor microcirculation studies. RESULTS: Europium and Texas Red can be detected by confocal microscopy. Europium, iron and gadolinium can be detected by secondary ion mass spectrometry (SIMS) microscopy. Studies confirmed the complementarity of both microscopies. They also confirmed the possibility of using europium as a model of gadolinium to analyze thefate of MRI contrast agents. CONCLUSION: The methodology can be used on mice injected intravenously and analyzed by confocal and SIMS microscopy to localize MRI contrast agents inside cellular and tissue specimens of mice.

Animals↗