Biomedical subjects

F Frouin

Publications and source records attributed to F Frouin.

32 records · Page 2Linked to original sources

PubMed1998

Characterization of cosmids and telomeres in cytogenetic preparations by 3D confocal fluorescence.

OBJECTIVE: To analyze, with fluorescent probes, by three-dimensional (3D) emission patterns, fluorescence in situ hybridization (FISH) preparations (cosmids, telomeres) and to perform factor analysis of medical image sequences (FAMIS); to use FISH to track relevant DNA sequences in cell nuclei during interphase and in mitotic chromosomes; and to use cytogenetic techniques, resulting in flat preparations of whole cells that are assumed to preserve probe access to their targets. STUDY DESIGN: The study design entailed labeling targets by probes (sequences labeled by fluorescein isothiocyanate) in nuclei and/or chromosomes stained by propidium iodide. Visualization of targets was improved when 3D sequences of images obtained on a single photomultiplier detector of the confocal microscope by z stepping were investigated by FAMIS. RESULTS: Factors and factor images showed that targets could be detected and differentiated in focal planes inside nuclei or chromosomes. CONCLUSION: It is possible to localize cosmids in cell nuclei at interphase and telomeres in mitotic chromosomes by means of 3D sequences of images.

Cosmids↗

PubMed1997

Laser scanning confocal microscopy and factor analysis of biomedical image sequences (FAMIS) to detect and characterise HPV DNA sequences by FISH in HeLa cells.

Visualisation and localisation of specific DNA sequences were performed by fluorescence in situ hybridisation (FISH), confocal laser scanning microscopy (CLSM), and factor analysis of biomedical image sequences (FAMIS). HeLa cells containing 10-50 copies per cell of human papillomavirus (HPV) DNA type 18 integrated in cellular DNA were used as a model. HPV-DNA was identified by DNA probes and DNA-DNA hybrids were revealed by alkaline phosphatase and Fast Red (FR) TR salt/naphtol-MX phosphate. Cell nuclei were counterstained with thiazole orange (TO). FAMIS summarises image sequences into a reduced number of images called factor images and curves called factors. Factor images correspond to spatial distributions of the different factors. Factors estimate different individual physical behaviours in the sequence (extinction velocity, spectral emission, depth emission profiles). We verified that HPV-DNA hybridisation signals are specific to the spectrum of FR, and distinguished between FR and TO. The latter result was found by taking into account differences in their extinction velocities. The focus of CLSM was improved on 3D image sequences, and the location of fluorescent signals inside the preparations was determined. Factor images showed that FR stained targets were located on different focal planes at the periphery of the nuclei.

DNA, Viral↗

PubMed1997

Confocal fluorescence analysis of the depth and focus of cytogenetic preparations.

OBJECTIVE: To characterize differences in the depth of fluorescent probes, to observe estimated depth levels (focal planes) on fluorescent in situ hybridization preparations by factor analysis of medical image sequences and to use cytogenetic techniques resulting in flat preparations of whole cells that are assumed to preserve the probes' access to their targets in the human nuclear interphase. STUDY DESIGN: We used labeling of the targets by the probes (sequences labeled by fluoroscein isothiocyonate [FITC]) in the nuclei, stained by propidium iodide. The investigation was performed on this model by three-dimensional (3-D) sequences of images obtained on a single photomultiplier detector of a confocal microscope by selection of emission between 510 and 550 nm and by (z) displacement. The investigation was also performed by obtaining sequences of images from spherical fluorescent beads to verify (z) focusing, to visualize depth differences and to analyze estimated factor images. RESULTS: Estimated images showed depth differences in FITC-stained targets as well as in nuclei, stained with propidium iodide, in interphase and in fluorescent beads, that could not be visualized by conventional 3-D reconstruction. CONCLUSION: It is possible to study 3-D architecture of flattened preparations and penetration of fluorophores inside the beads and to evaluate depth differences.

Cell Nucleus↗

PubMed1996

Radiologic assessment of intranodal vascularity in head and neck squamous cell carcinoma. Correlation with histologic vascular density.

RATIONALE AND OBJECTIVES: Nodal response to chemotherapy in head and neck squamous cell carcinoma depends on the vascularization. The authors assessed different techniques in detecting nodal vascularization. METHODS: Fourteen patients with head and neck tumor were included before surgical treatment. The largest metastatic lymph node (mean axial scanographic diameters 30 x 20 mm) was studied by color and pulsed Doppler, and dynamic magnetic resonance images, processed by factor analysis of medical image sequences (FAMIS), which estimates physiologic contrast enhancement kinetics (factors) and their spatial distributions (factor images). Results were compared with the histologic microvessel density (MVD). Using light microscopy, MVD was estimated by the vascular surface (by staining endothelial cells) to the stroma surface ratio x 100. RESULTS: Three factors were identified by FAMIS: a constant factor in necrosis, an earlier F1 factor and a later F2 factor in normal lymphoid areas and neoplastic stroma. Color flow signal was detected when the MVD was greater than 6.36. CONCLUSIONS: Only one model of vascularization was extracted by FAMIS, with no difference between neoplastic and spared lymphoid areas. The presence of color-flow signals could help predict the response of metastatic lymph nodes to chemotherapy.

Carcinoma, Squamous Cell↗

PubMed1996

Spectral and dynamic confocal fluorescence characterization of cytogenetic preparations.

Investigations were performed on fluorescent in situ hybridization (FISH) preparations to examine whether factor analysis of medical image sequences (FAMIS) can be used to isolate fluorescent probes by means of their spectral and/or extinction dynamic emission properties. FISH is used to track down chromosomes of interest in cell nuclei and mitoses. Cytogenetic techniques producing flat preparations of whole cells were assumed to preserve the probes' access to their targets. To isolate the result of hybridization in the human nuclear interphase, we used a confocal microscope. Labelling of the targets by the probes (sequences labelled by FITC and TRITC) in the nuclei stained by propidium iodide was used as a biological model. We used two methods to isolate the component parts of the model: multispectral analysis and dynamic studies. In the case of multispectral analysis, the investigation was performed on 2D and 3D sequences of 28 images obtained on a single photomultiplier (PM) detector of the confocal microscope by selection of emission through 10-nm interference filters in the range of 500-780 nm and by z-displacement in each filter setting. In the case of dynamic studies, the investigation was performed on sequences of 30-70 images obtained on the same detector by single or average integrated acquisition of 10-30 scans. Confocal scanning yields images with constant excitation time. These images were investigated by FAMIS and the results revealed that the spectra and kinetics as factors, and factor images corresponded to FITC and TRITC stained targets, as well as to propidium iodide stained interphase. In conclusion, we would verify that targets were isolated through the spectrum of the fluorescent probes and could be distinguished from the propidium iodide used to stain the nuclei. It was also possible to distinguish them from the propidium iodide by taking into account differences in photobleaching of the different fluorochromes. The study leads us to process displacements by registration methods prior to factor analysis to improve the results.

Fluorescein-5-isothiocyanate↗

PubMed1995

Comparison between factor analysis of dynamic structures and Fourier analysis in detection of segmental wall motion abnormalities: a clinical evaluation.

To evaluate Factor Analysis of Dynamic Structures (FADS) versus or in association with other methods, a protocol was set up including as 'gold standard' investigation the left ventricular angiography (LVA) and processing by Fourier Analysis (FA), and FADS with different variants. To refine the diagnosis of Regional Wall Motion Abnormalities (RWMA), processing was done on a sectorial basis for more accurate spatial localization and functional description. 53 patients were studied (8 normal, 45 with coronary artery disease). FADS gave better results than FA on a sectorial basis. Total agreement between FADS and LVA was obtained in 208/265 (78%), while FA was in agreement with LVA in only 167/265 segments (63%). Globally, FADS was significantly better than FA (Z-test: p < 0.05). When only the diagnosis of maximal abnormality was considered, FA and FADS are statistically equivalent. The superiority of FADS vs FA is more obvious in the diagnosis of hypokinesia. Most FA discrepancies corresponded to underestimation of WMA.

Adult↗

PubMed1994

Processing by factor analysis of dynamic dual isotope studies using 99Tcm and 201Tl within a middle energy band. Evaluation in thyroid nodule malignancy.

Simultaneous investigations with two isotopes are currently restricted because of spectral overlap. The factor analysis of spectral and dynamic structures (FASDS) method is shown to achieve accurate spectral separation. In addition, it estimates underlying dynamic mechanisms. Twenty-six patients were injected simultaneously with 99Tcm-pertechnetate and 201Tl-chloride to assess the malignancy of solitary thyroid nodules. List-mode acquisition of spectral, temporal and spatial coordinates of events allows the reconstruction of an image sequence indexed by time and energy. FASDS proceeds in two steps. First it yields both dynamic and spatial information related to each isotope (99Tcm and 201Tl) and partially removes the scatter component. Then it estimates the underlying kinetics and associated spatial distributions of each isotope. Using the 201Tl component, an index was derived from the uptake ratio between nodules and normal thyroid tissue. Concerning the detection of malignant nodules the method indicated no false negative in our limited group of 26 patients. One false positive result was found which could not be classified by the investigation of the 201Tl dynamic components contained in the reconstructed 201Tl factor sequence.

Factor Analysis, Statistical↗

PubMed1993

Factor analysis as a means of determining response to chemotherapy in patients with osteogenic sarcoma.

The prognosis of localized osteogenic sarcoma (OS) has improved considerably since the introduction of neoadjuvant chemotherapy. However, there is a subset of patients who do not show full benefit from neoadjuvant chemotherapy because of chemoresistance. The early identification of poor responders to chemotherapy during neoadjuvant therapy remains difficult. In order to evaluate the role of bone scintigraphy we report our experience of dynamic technetium-99m hydroxymethylene diphosphonate bone scintigraphy in 19 cases of paediatric osteogenic sarcomas. Before the beginning of chemotherapy, a dynamic scan was recorded during 30 min followed by static images at 3 h. The procedure was repeated halfway through the course of chemotherapy (6th week). Histological grading of the response to chemotherapy was carried out in the 12th week, showing nine good responses and ten poor responses. Factor analysis of dynamic structures (FADS) applied to dynamic scans allowed us to identify three factors termed vascular, "soft tissue" and osseous factors. The effect of chemotherapy on each factor was evaluated. Using FADS we were able to detect all the poor histological responders with the combination of vascular and osseous factors. Six out of nine good histological responders were also classified as scintigraphic responders. FADS applied to dynamic bone scans allowed us to identify at an early stage all the poor histological responders to neoadjuvant chemotherapy. This method may have clinical relevance for the therapeutic strategy in patients with OS.

Adolescent↗

PubMed1993

Target apex-seeking in factor analysis of medical image sequences.

The aim of factor analysis of medical image sequences (FAMIS) is to estimate a limited number of physical or physiological fundamental functions. Its oblique rotation stage strongly affects the quality and the interpretation of the resulting estimates (factors and factor images). A new target apex-seeking method which integrates physical or physiological knowledge in this stage is described. This knowledge concerns some of the fundamental functions and reacts on the determination of all the factors. A simulated spectral study illustrates the method. We discuss its properties in comparison with the other approaches using a priori physical or physiological information.

Computer Simulation↗

PubMed1993

A statistical model for the determination of the optimal metric in factor analysis of medical image sequences (FAMIS).

A statistical model is added to the conventional physical model underlying factor analysis of medical image sequences (FAMIS). It allows a derivation of the optimal metric to be used for the orthogonal decomposition involved in FAMIS. The oblique analysis of FAMIS is extended to take this optimal metric into account. The case of scintigraphic image sequences is used. We derive in this case that the optimal decomposition is obtained by correspondence analysis. A scintigraphic dynamic study illustrates the practical consequences of the use of the optimal metric in FAMIS.

Factor Analysis, Statistical↗

PubMed1992

Diagnosis of malignancy in thyroid nodules by factor analysis of spectral and dynamic structures: a simultaneous dual-isotope dynamic study with thallium-201 and iodine-131.

The aim of this study was to identify malignant thyroid nodules using iodine-123 and thallium-201 simultaneous dynamic acquisition. The image sequences acquired were processed by factor analysis of spectral and dynamic structures (FASDS). Some 49 patients were investigated, and their diagnoses were confirmed by histological examination. Data processing enables the estimation of the spectra of the two isotopes and the evaluation of the kinetics and spatial structures related to each tracer. The superimposition of thallium and iodide sum images allowed us to delineate the nodule accurately. Two groups were defined: 21 patients who had 201Tl uptake in the nodule, and 28 who had none. In the first group, 5 nodules were carcinomas, whereas all nodules in the second group were benign. The results of the 201Tl dynamic study improved the diagnosis of carcinoma as the number of false-positive cases decreased. FASDS succeeds in extracting spectral and kinetic information, proving its usefulness in clinical diagnosis.

Adenoma↗

PubMed1992

Factor analysis of dynamic magnetic resonance imaging in predicting the response of osteosarcoma to chemotherapy.

RATIONALE AND OBJECTIVES: The response of osteosarcoma to preoperative chemotherapy was assessed using dynamic magnetic resonance imaging (MRI) processed by factor analysis of medical image sequences (FAMIS). METHODS: Forty-nine dynamic image sequences, acquired after a bolus injection of gadolinium in 10 patients, were processed by FAMIS: FAMIS is a means whereby physiologic contrast enhancement kinetics, called factors, and their spatial distribution, termed factor images, are estimated. Tumor volumes were measured on static MRIs, and factor images were compared with histologic maps of the resected specimens. RESULTS: A substantial increase in tumor volume reflected a poor response to chemotherapy. Viable tumor was precisely depicted by the early vascular factor image, reflecting rapid uptake by tumor vessels. This early uptake disappeared in all five patients who responded to chemotherapy, whereas it persisted in four of five nonresponders. CONCLUSION: FAMIS of dynamic MRI is proposed as a possible means of predicting the response of osteosarcoma to chemotherapy.

Adolescent↗

PubMedDate not supplied

FAMIS: a software package for functional feature extraction from biomedical multidimensional images.

An increased number of image sequences is acquired in all modalities of the biomedical imaging field in order to study displacement or metabolism of a tracer or a contrast agent. It requires effective processing methods to estimate the underlying physiological components. We have developed a software package based on factor analysis algorithms which can adapt to various imaging modalities and its extension to double-indexed image sequences. We describe general characteristics of the software and present the main points of the user-friendly interface. The performances of the package are discussed and the possibilities of the methodology are illustrated using an example in magnetic resonance imaging.

Algorithms↗

PubMedDate not supplied

Extraction of functional volumes from medical dynamic volumetric data sets.

A method based on factor analysis is presented to process dynamic volumetric (t + 3D) data sets acquired for flow, excretion, or metabolic studies. It estimates a reduced number of underlying physiological kinetics and their associated spatial distributions, corresponding to functional volumes, using dedicated algorithms. The global (t + 3D) approach is shown to be superior to the conventional one, which repeats estimations on each (t + 2D) data set, obtained for each slice or projection of the volume.

Algorithms↗