Segmentation d’images de lésions cérébrales primitives en TEP FET : influence du volume de travail

Purpose(1) Evaluate the reproducibility of segmentation methods depending on the preselection region for tumour volume determination on ¹⁸F-fluoro-ethyl-tyrosine (FET) PET. (2) Evaluate the intra and inter-operator reproducibility of the manual delineation. (3) Compare this delineation with the segmentation methods.Materials and methodsEighteen FET PET of patients with glioblastoma were analysed. Preselection regions were determined prior to any segmentation. Two physicians delineated the tumour volume manually. The tumour volume was also delineated with a threshold method (40 and 70% of SUV_max), and a random walk based method. Pearson coefficient (r) (P < 0.05 for r > 0.468) and Jaccard indices (JI) were used to compare the volumes.ResultsManual delineation was reproducible with r = 0.97 and IJ = 0.65 for intra-operator, and r = 0.76 and IJ = 0.45 for inter-operator reproducibility. The preselection regions for a given lesion were different and the segmentation varied with the preselection region: r = 0.55 JI = 0.58; r = 0.85 JI = 0.83; r = 0.70 JI = 0.39 respectively for the threshold of 40%, 70% and the random walk. The segmentation differed form de manual delineation with r = 0.37 and JI = 0.16; r = 0.54 and JI = 0.42; r = 0.43 and JI = 0.37 respectively for the threshold of 40%, 70% and the random walk.ConclusionThe reproducibility of the segmentation methods depends extensively on the preselection region. The intra-operator reproducibility of cerebral lesion delineation on FET PET is satisfactory. The inter-operator reproducibility could be improved.     

Ovarian Fibroma Mimicking Malignant Tumor on F-18 FDG PET/CT

Benign ovarian tumors like fibroma rarely shows mild or moderate F-18 FDG uptake. FDG-avid adnexial lesions in postmenopausal women should be as considered primarily malignant. A 69 years old female who had diagnosis with both colon adenocarcinoma and lung carcinoma, was referred to F-18 FDG PET/CT imaging for follow up. A mass lesion showing moderate F-18 FDG uptake at right adnexial region was detected. She was operated after gynaecological evaluation. Her histopathology examination was reported as ovarian fibroma.     

Cancer de la prostate : utilité de la TEP-TDM à la F-fluorocholine

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for ¹⁸F-fluorodeoxyglucose (¹⁸FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with ¹⁸F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of ¹⁸F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.     

TEP/TDM au FDG et bilan initial des lymphomes : du diagnostic au pronostic

Lymphoma represents a very heterogeneous pathologic disease group and its initial assessment, treatment strategy and prognosis is closely related within each histological subtype. The diagnosis of lymphoma disease is often due to the development of a tumour mass at a lymph node area, or within an organ with or without systemic symptoms. However, all these signs remain non specific. Biopsy is the only reliable diagnostic tool, which can be carried out surgically or guided by the morphological and functional imaging. Once the histological diagnosis is determined by the WHO classification, the staging procedure aim is to provide the prognosis to assist the therapeutic decision. Morphologic imaging primarily based on CT remains the reference in exploring most cases. But in the last decade, the introduction of functional imaging using FDG-PET/CT has dramatically changed the therapeutic management of lymphoma. The additional clinical value provided by initial FDG-PET/CT could lead to an alteration of the therapeutic strategy, as well as to the optimization of radiation therapy or to the establishment of prognostic score and lead to improved lymphoma patient survival in the future.     

Diatom-associated bacteria are required for aggregation of Thalassiosira weissflogii

Aggregation of algae, mainly diatoms, is an important process in marine systems leading to the settling of particulate organic carbon predominantly in the form of marine snow. Exudation products of phytoplankton form transparent exopolymer particles (TEP), which acts as the glue for particle aggregation. Heterotrophic bacteria interacting with phytoplankton may influence TEP formation and phytoplankton aggregation. This bacterial impact has not been explored in detail. We hypothesized that bacteria attaching to Thalassiosira weissflogii might interact in a yet-to-be determined manner, which could impact TEP formation and aggregate abundance. The role of individual T. weissflogii-attaching and free-living new bacterial isolates for TEP production and diatom aggregation was investigated in vitro. T. weissflogii did not aggregate in axenic culture, and striking differences in aggregation dynamics and TEP abundance were observed when diatom cultures were inoculated with either diatom-attaching or free-living bacteria. The data indicated that free-living bacteria might not influence aggregation whereas bacteria attaching to diatom cells may increase aggregate formation. Interestingly, photosynthetically inactivated T. weissflogii cells did not aggregate regardless of the presence of bacteria. Comparison of aggregate formation, TEP production, aggregate sinking velocity and solid hydrated density revealed remarkable differences. Both, photosynthetically active T. weissflogii and specific diatom-attaching bacteria were required for aggregation. It was concluded that interactions between heterotrophic bacteria and diatoms increased aggregate formation and particle sinking and thus may enhance the efficiency of the biological pump.     

Epstein-Barr Virus-Induced Expression of a Novel Human Vault RNA

Non-protein-coding RNAs (ncRNAs) have recently emerged on the scene of genomic research as prominent players in the regulation of gene expression. Many functionally characterized ncRNAs have been shown to be differentially expressed in various organisms during specific environmental or developmental conditions, thus establishing regulatory networks crucial for shaping cellular life. Here, we show that the expression of vault RNAs (vtRNAs) is specifically up-regulated in human lymphocytes upon infection by γ-herpesviruses, such as the Epstein-Barr virus and Kaposi's sarcoma virus. vtRNAs are ncRNAs that are integral to the vault complex, a gigantic (13 MDa) hollow ribonucleoprotein particle with a thus far elusive biological role. Stimulation of vtRNA expression by the Epstein-Barr virus was evident for all three canonical vtRNAs (hvg1-hvg3) and also for a novel ncRNA candidate, initially termed CBL-3. This ncRNA shares clear primary- and secondary-structure similarities with the three known vtRNAs. Importantly, CBL-3 co-sediments with intact vault particles in density gradients of various human cell lines, thus strongly indicating this ncRNA as a novel, fourth vault-complex-associated RNA.     

Study on simulation models of tomato fruit quality related to cultivation environmental factors

Plant growth simulation models are valuable tools for optimizing the environmental factors and managing crop cultivation in cultural facilities. Researches presently on tomato simulation models have mainly focused on the plant growth and development, growth stages, dry matter production and distribution, however, no report on modeling of tomato fruit quality has been published yet. In this study, the method of accumulated Thermal Effectiveness and PAR (TEP) was employed to model the dynamic relationship between the major quality indicators and the environmental factors. Data of both indicators of tomato fruit quality and environmental factors, temperature and solar radiation of the cultivation environment, were collected under multiple protected structures like solar greenhouse and plastic tunnel for tomato production. The variety of simulation models were established based on the effects of temperature and solar radiation on tomato quality formation, and independently tested with the modeling data. The results show that the dynamic changes of the indicators of fruit quality after fruit set are accorded with the amount of accumulated TEP and individual indicators of fruit quality are suitable to its specific models. The fruit hardness is well accorded with a formula of generalized least squares FHi = k₁ + k₂ × TEPi + k₃ × TEPi² ; Fruit soluble sugar content is in a formula of Logistic model  . Fruit organic acid content is in a formula of generalized least squares OACi = n₁ + n₂ × TEPi + n₃ × TEPi². Fruit tannin content is in a formula of Johnson Schumacher model  . According to the established fruit hardness model, the determination coefficient R² values based on the 1:1 beeline between the simulated values and the measured values of the first, second, third and the fourth truss of fruit are 0.9396, 0.9181, 0.8910 and 0.9523, respectively and values of root mean square error (RMSE) are 0.833 kg/cm², 0.942 kg/cm², 0.628 kg/cm² and 0.738 kg/cm², respectively. Based on the established fruit soluble sugar content model, the determination coefficient R² values based on the 1:1 beeline between the simulated values and the measured values of the first, second, third and the fourth truss of fruit are 0.8596, 0.9420, 0.9027 and 0.9473, respectively and the values of RMSE are 1.011%, 0.710%, 0.771% and 0.608%, respectively. On the basis of the established fruit organic acid content model, the determination coefficient R² values based on the 1:1 beeline between the simulated values and the measured values of the first, second, third and the fourth truss of fruit are 0.8856, 0.9025, 0.9183 and 0.8768, respectively and the values of RMSE are 0.029%, 0.030%, 0.024% and 0.023%, respectively. According to the established fruit tannin content model, the determination coefficient R² values based on the 1:1 beeline between the simulated values and the measured values of the first, second, third and the fourth truss of fruit are 0.9481, 0.9219, 0.9521 and 0.8911, respectively and the values of RMSE are 13.41 mg/kg, 14.04 mg/kg, 13.92 mg/ kg and 16.78 mg/kg, respectively. All of the coefficients of determination R² are higher than 0.85, and the values of RMSE are generally smaller, which means the modeling is accurate and well accordance. This study will form a theoretic basis and provide technical support for the management of tomato production and environment control under plastic tunnel and solar greenhouse cultivation.     

Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin

Exopolymeric substances (EPS) isolated from a pure culture of the marine bacterium Marinobacter sp. and the marine diatom Skeletonema costatum (axenic) were partially purified, chemically characterized and used as dissolved organic matter (DOM) for the production of macroaggregates. The role of organic particles such as transparent exopolymeric particles (TEP) and Coomassie stained particles (CSP) in the production of macroaggregates was experimentally assessed. Three experimental rolling tanks containing sterile medium with: (1) EPS, (2) EPS + live diatom cells and (3) EPS + killed bacteria, and three control tanks without any added EPS were used for macroaggregate production. Changes in abundance and average size of macroaggregates were monitored using image analysis, whereas TEP and CSP were enumerated microscopically. In the presence of microbial EPS, macroaggregates of a size of 23-35 mm(2) were produced. Aggregate size and abundance considerably varied with both time and source of EPS. No correlation was observed for macroaggregate size and abundance with either TEP or CSP. One-way ANOVA demonstrated significant differences in the variance of particle abundance and size in tanks having only EPS or EPS in combination with live diatom cells. Our data suggest that production of macroaggregates was influenced by polymer chemistry and surface properties of colliding particles, whereas TEP and CSP concentrations were influenced by molecular weight of EPS and the presence of growing cells. Interestingly, macroaggregates were formed in the near absence of TEP and CSP, highlighting the role of other unknown processes in the transformation of DOM to particulate organic matter (POM) in aquatic environments.     

A method to quantify at late imaging a release rate of 18F-FDG in tissues

This theoretical work shows that the rate constant for the (18)F-FDG release in tissues can be assessed without needing any arterial blood sampling. The method requires that the clearance of (18)F-FDG from plasma has occurred, whereas (18)F-FDG is still present in the tissue. This condition can be met dating from 3 h after (18)F-FDG injection, when hydration and/or phlorizin injection are applied after the routine static acquisition. The release rate constant can be obtained from a graphical analysis performed at the later decreasing phase of the tissue tracer activity. A two-compartment and a three-compartment model are developed, both in accordance with one another. To cite this article: E. Laffon et al., C. R. Biologies 328 (2005).