Search

In this article, selected new directions in knowledge-based artificial intelligence (AI) and machine learning (ML) are presented: ontology development methodologies and tools, automated engineering of WordNets, innovations in semantic search, and automated machine learning (AutoML). Knowledge-based AI and ML complement each other ideally, as their strengths compensate for the weaknesses of the other discipline. This is demonstrated via selected corporate use cases: anomaly detection, efficient modeling of supply networks, circular economy, and semantic enrichment of technical information.

Purpose Insulinomas are predominantly benign neuroendocrine tumors originating from beta cells within the islets of Langerhans of the endocrine pancreas. Because surgical resection represents the only curative therapy option, exact tumor localization and discrimination of insulinomas from focal or diffuse manifestations of congenital hyperinsulinism are crucial for optimal treatment strategies. We investigated the diagnostic value of glucagon-like peptide 1 receptor PET/CT using Ga-DOTA-exendin 4 for detecting insulinomas and compared the diagnostic value of PET scans performed at 2 time points. Methods In 10 patients with clinically and biochemically suspected insulinoma, PET/CT was performed at 1 hour (PET1) and 2 hours (PET2) after injection of Ga-DOTA-exendin 4. In this retrospective analysis, tracer uptake was visually assessed in both scans by 2 independent readers. SUVmax and tumor-to-background ratio (TBR) of focal lesions were assessed. Imaging results were compared with histopathologic findings, if patients underwent resection. Results Increased focal Ga-DOTA-exendin 4 uptake was observed in 8 of 10 patients concordantly by both readers. Seven patients with focal uptake underwent surgery with tumor enucleation and histopathologic proof of insulinoma (7/8). Two of 10 patients without focal uptake were considered to suffer from diffuse form of congenital hyperinsulinism and consequently received medical treatment. A significant increase of tumoral SUVmax on PET2 (PET1: SUVmax 20.2 ± 8.2 g/mL; PET2: SUVmax 24.7 ± 7.9 g/mL; P = 0.0018) did not result in a significant improvement in TBR (PET1: TBR 4.9 ± 1.7; PET2: TBR 4.3 ± 1.2; P = 0.2892). Conclusions Focal uptake of Ga-DOTA-exendin 4 reliably indicated insulinomas as histopathologically confirmed in all patients undergoing consecutive surgery. The diagnostic value of PET2 was not found to be superior to PET1, indicating that a single 1-hour Ga-DOTA-exendin 4 PET/CT scan is a sufficient and convenient approach for patient care.

ZusammenfassungDie Myokardperfusionsszintigrafie (MPS) hat sich im Bereich der klinischen Anwendung und Methodik in Deutschland in den 10 letzten Jahren kontinuierlich entwickelt. Die neue europäische Leitlinie zur Diagnostik und Behandlung des neu definierten chronischen Koronarsyndroms hat die Rolle der nicht invasiven Bildgebung und damit der nuklearmedizinischen Verfahren bestätigt und gestärkt. Die MPS liefert wertvolle Beiträge zur klinischen Prognoseeinschätzung und Therapieentscheidung aufgrund des Zusammenhanges von szintigrafisch nachgewiesener Perfusionsstörung mit der Häufigkeit von kardiovaskulärem Tod und nicht tödlichem Herzinfarkt.In diesem Artikel wird ein Überblick über die Einsatzbereiche, die aktuellen Leitlinien und den momentanen Stellenwert der MPS sowie eine kurze Zusammenfassung der praktischen Anwendung des Verfahrens gegeben.

A 58-year-old man with progressive dyspnea and recurrent extensive left-sided pleural effusion underwent pulmonary ventilation/perfusion SPECT/CT, which showed a pronounced mismatched perfusion deficit of the entire, normally ventilated left lung. As unilateral perfusion deficits of an entire lobe are generally not due to pulmonary embolism, further CT angiography and cardiac MRI were conducted. These examinations revealed high-grade left pulmonary vein stenosis (PVS) caused by pulmonary vein isolation performed for atrial fibrillation 3 and 4 years earlier. Thus, in addition to, for example, neoplastic processes or pulmonary congenital vascular abnormalities, PVS must be considered as a differential diagnosis and possible pitfall in ventilation/perfusion SPECT/CT in dyspneic patients with prior pulmonary vein isolation.

Background To provide insight into bone turnover, quantitative measurements of bone remodeling are required. Radionuclide studies are widely used in clinical care, but have been rarely used in the exploration of the bone in preclinical studies. We describe a bone planar scintigraphy method for frequent assessment of bone activity in mice across the growing period. Since repeated venous radiotracer injections are hardly feasible in mice, we investigated the subcutaneous route. Methods Repeated 99mTc-hydroxymethylene diphosphonate (HMDP) tracer bone planar scintigraphy studies of the knee region and µCT to measure femur growth rate were performed in eight mice between week 6 and week 27 of life, i.e., during their growth period. Three independent investigators assessed the regions of interest (ROI). An index was calculated based on the counts in knees ROI (normalized by pixels and seconds), corrected for the activity administered, the decay between administration and imaging, and individual weights. Results A total of 93 scintigraphy studies and 85 µCT were performed. Repeated subcutaneous tracer injections were well tolerated and allowed for adequate radionuclide studies. Mean scintigraphic indexes in the knees ROI decreased from 87.4 ± 2.6 × 10−6 counts s−1 pixel−1 MBq−1 g−1 at week 6 to 15.0 ± 3.3 × 10−6 counts s−1 pixel−1 MBq−1 g−1 at week 27. The time constant of the fitted exponential decay was equal to 23.5 days. As control mean femur length assessed by µCT increased from 12.2 ± 0.8 mm at week 6 to 15.8 ± 0.2 mm at week 22. The time constant of the fitted Gompertz law was equal to 26.7 days. A correlation index of −0.97 was found between femur growth and decrease of bone tracer activity count between week 6 and 24. Conclusion This methodological study demonstrates the potential of repeated bone planar scintigraphy in growing mice, with subcutaneous route for tracer administration, for quantitative assessment of bone remodeling.

A 31-year-old man developed diarrhea, fatigue, and intermittent fever for 2 weeks. The past few days he had experienced increasing dyspnea and dry cough. Ambulatory reverse transcriptase–polymerase chain reaction testing was positive for SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Because of elevated d-dimer (1.5 mg/L), a lung scintigraphy (V/Q scan) was performed as SPECT/CT. Ventilation SPECT showed reduced ventilation with central nuclide deposition, whereas perfusion SPECT was inconspicuous, excluding pulmonary embolism. However, the low-dose CT revealed bilateral ground-glass opacities as previously described in COVID-19. This case highlights the procedure and findings of V/Q scanning (without embolism) in COVID-19.

Background Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) with 177Lu-labeled PSMA ligands has achieved remarkable results in advanced disease stages of metastatic castration-resistant prostate cancer (mCRPC). However, not all patients benefit from this therapy. Different treatment responses could be explained by tumor heterogeneity triggered by progression and the number of prior treatments. PSMA-negative lesions can be missed on PSMA ligand PET/CT, which subsequently results in an underestimation of tumor burden. Conversely, high FDG uptake may also be an indicator of tumor aggressiveness and thus a poor prognostic marker for response to RLT and overall survival (OS). The aim of this analysis was to investigate the prognostic value of combined PSMA ligand PET/CT and [18F]fluorodeoxyglucose (FDG) PET/CT for outcome prediction in patients undergoing RLT. Materials and methods This bicentric analysis included 54 patients with mCRPC who underwent both FDG and PSMA ligand PET/CT imaging before RLT. In all patients, the pattern of PSMA ligand and FDG uptake was visually assessed. Patients with at least one FDG-positive, but PSMA-negative (FDG+/PSMA−) lesions were compared to patients without any FDG+/PSMA− lesions. A log-rank analysis was used to assess the difference in OS between subgroups. Results Median OS was 11 ± 1.8 months (95% CI 7.4–14.6). A significantly lower OS (p n = 18) with a median OS of 6.0 ± 0.5 months (95% CI: 5.0–7.0 months). In comparison, patients without any FDG+/PSMA− lesions (n = 36) had a median OS of 16.0 ± 2.5 months (95% CI: 11.2–20.8 months). Conclusion FDG+/PSMA− lesions are a negative predictor of overall survival in patients with mCRPC undergoing RLT. However, it remains to be determined if patients with FDG+/PSMA− lesions should be excluded from PSMA RLT.

Different environmental conditions under anesthesia may lead to unstable homeostatic conditions in rodents and therefore may alter kinetics. In this study, the impact of different heating conditions on PET imaging quantification was evaluated. Methods: Two groups of 6 adult female BALB/c nude mice with subcutaneously implanted tumors underwent microPET imaging after injection of 18F-labeled tetrafluoroborate or 18F-FDG. Dynamic scans were acquired under optimal and suboptimal heating conditions. Time-activity curves were analyzed to calculate uptake and washout time constants. Results: With 18F-labeled tetrafluoroborate, optimal animal heating led to a stable heart rate during acquisition (515 ± 35 [mean ± SD] beats/min), whereas suboptimal heating led to a lower heart rate and a higher SD (470 ± 84 beats/min). Both uptake and washout time constants were faster (P < 0.01) in animals maintained with optimal heating. Conclusion: Although the difference in heart rates was slight, optimal heating yielded significantly faster uptake and washout kinetics than suboptimal heating in all organs for both tracers.

The present work compares intravenous (IV) and subcutaneous (SC) routes for contrast-enhanced MRI (CE-MRI) in mice. For that purpose, we selected two contrast media used in clinical practice. MRI acquisitions were performed at 1.5 T on five adult mice (Swiss, 41 g +/- 3 g). On each animal, four acquisitions were achieved with IV and SC administration of either Gd-DOTA or MS-325 (1 acquisition per week). For each route, 0.1 mL of NaCl and 0.1 mL of contrast agent were injected. For each acquisition, 200 T1-weighted images were acquired in a 2 h 34 min time lapse. For each route and contrast medium, dynamic contrast enhancement (DCE) curves were obtained. Time-to-peak (TTP), uptake, and washout constant-time values and contrast-to-noise ratio (CNR) were extracted. IV route TTP value was 4.9 min with Gd-DOTA and 5.4 min with MS-325. SC route TTP was 43.3 min with Gd-DOTA and 45.0 min with MS-325. Despite slower uptake constant-time, we show that SC is a potentially valuable alternative to the IV route in mouse preclinical CE-MRI.

International audience; We use high-resolution [Formula: see text] data in multiple experiments to estimate the sources of error during coregistration of images acquired on separate preclinical instruments. In combination with experiments with phantoms, we completed in vivo imaging on mice, aimed at identifying the possible sources of registration errors, caused either by transport of the animal, movement of the animal itself, or methods of coregistration. The same imaging cell was used as a holder for phantoms and animals. For all procedures, rigid coregistration was carried out using a common landmark coregistration system, placed inside the imaging cell. We used the fiducial registration error and the target registration error to analyze the coregistration accuracy. We found that moving an imaging cell between two preclinical devices during a multimodal procedure gives an error of about [Formula: see text] at most. Therefore, it could not be considered a source of coregistration errors. Errors linked to spontaneous movements of the animal increased with time, to nearly 1 mm at most, excepted for body parts that were properly restrained. This work highlights the importance of animal intrinsic movements during a multiacquisition procedure and demonstrates a simple method to identify and quantify the sources of error during coregistration.

Purpose In patients with primary hyperparathyroidism, the preoperative imaging objective is to locate accurately and reliably uniglandular or multiglandular hyperfunctioning parathyroid, to guide surgery, particularly for minimally invasive method. Subtraction planar scintigraphy with dual-isotope (I/Tc-MIBI) is an efficient examination to specify abnormal parathyroid location, but without accurate anatomic reference. This lack should be avoided by a hybrid SPECT/CT image acquisition. Methods We compared planar scans (neck and mediastinum parallel-hole, associated with anterior neck pinhole) to neck and mediastinum SPECT/CT, all with subtraction (I/Tc-MIBI) method, in exact location of abnormal parathyroid in 50 patients with sporadic primary hyperparathyroidism. Surgical and histological findings were used as the standard of comparison. Results Sensitivity is equivalent for the 2 protocols (86% and 75% for SPECT/CT and planar protocol, respectively, P = 0.15), but SPECT/CT was highly specific (specificity 100% and 90% for SPECT/CT and planar protocol, respectively, P = 0.04). In patients with concomitant thyroid disease, subtraction SPECT/CT appeared to be more sensitive than planar protocol (88% and 62% for SPECT/CT and planar protocol, respectively, P = 0.04). Conclusions In preoperative assessment of primary hyperparathyroidism and to guide surgery, we propose to perform first subtraction SPECT/CT and to complete it with neck pinhole, only if tomoscintigraphy is negative.

An universal tool was designed for small animal SPECT/CT/MR coregistration. It was tested on a preclinical MRI (OPTImouse, RS2D, Bischwiller, France) and a micro-SPECT/CT (eXplore speCZT Vision 120, GE, Waukesha, USA), closed to each other, thanks to the short extension of the MRI magnet fringe field. The tool consists of a curved catheter describing many rigid loops, and fixed on a plastic sheet. During acquisitions, it is placed around the animal, in an isolated imaging cell, and filled with a solution containing iodine, copper sulfate and radioisotope. Multimodality imaging is achieved sequentially by moving the cell from one system to the other, in about 20 s. Acquisitions on phantom demonstrate the resolution accuracy of the coregistration process. Whole body trimodal SPECT/CT/MR acquisitions on live mice were coregistrated as well. A simple, cheap tool, easy to fill, could efficiently help for rigid coregistration of preclinical images, acquired on separate imaging apparatus.

We estimate the impact of regulatory heterogeneity on agri-food trade using a gravity analysis that relies on detailed data on non-tariff measures (NTMs) collected by the NTM-Impact project. The data cover a broad range of import requirements for agricultural and food products for the EU and nine of its major trade partners. We find that trade is significantly reduced when importing countries have stricter maximum residue limits (MRLs) for plant products than exporting countries. For most other measures, due to their qualitative nature, we were unable to infer whether the importer has stricter standards relative to the exporter, and we do not find a robust relationship between these measures and trade. Our findings suggest that, at least for some import standards, harmonising regulations will increase trade. We also conclude that tariff reductions remain an effective means to increase trade even when NTMs abound.

A dependence of poliovirus on an unorthodox translation initiation mode can be targeted selectively to drive viral protein synthesis and cytotoxicity in malignant cells. Transformed cells are naturally susceptible to poliovirus, due to widespread ectopic upregulation of the poliovirus receptor, Necl-5, in ectodermal/neuroectodermal cancers. Viral tumor cell killing and the host immunologic response it engenders produce potent, lasting antineoplastic effects in animal tumor models. Clinical application of this principle depends on unequivocal demonstration of safety in primate models for paralytic poliomyelitis. We conducted extensive dose-range-finding, toxicity, biodistribution, shedding, and neutralizing antibody studies of the prototype oncolytic poliovirus recombinant, PVS-RIPO, after intrathalamic inoculation in Macaca fascicularis . These studies suggest that intracerebral PVS-RIPO inoculation does not lead to viral propagation in the central nervous system (CNS), does not cause histopathological CNS lesions or neurological symptoms that can be attributed to the virus, is not associated with extraneural virus dissemination or replication and does not induce shedding of virus with stool. Intrathalamic PVS-RIPO inoculation induced neutralizing antibody responses against poliovirus serotype 1 in all animals studied.

In cancerous cells, physiologically tight regulation of protein synthesis is lost, contributing to uncontrolled growth and proliferation. We describe a novel experimental cancer therapy approach based on genetically recombinant poliovirus that targets an intriguing aberration of translation control in malignancy. This strategy is based on the confluence of several factors enabling specific and efficacious cancer cell targeting. Poliovirus naturally targets the vast majority of ectodermal/neuroectodermal cancers expressing its cellular receptor. Evidence from glioblastoma patients suggests that the poliovirus receptor is ectopically upregulated on tumor cells and may be associated with stem cell-like cancer cell populations and proliferating tumor vasculature. We exploit poliovirus’ reliance on an unorthodox mechanism of protein synthesis initiation to selectively drive viral translation, propagation and cytotoxicity in glioblastoma. PVSRIPO, a prototype nonpathogenic poliovirus recombinant, is scheduled to enter clinical investigation against glioblastoma.

Respiratory tract (RT) infections by members of the enterovirus (EV) genus of the Picornaviridae family are the most frequent cause for the common cold and a major factor in the exacerbation of chronic pulmonary diseases. The lack of a practical small-animal model for these infections has obstructed insight into pathogenic mechanisms of the common cold and their role in chronic RT illness and has hampered preclinical evaluation of antiviral strategies. Despite significant efforts, it has been difficult to devise rodent models that exhibit viral replication in the RT. This is due mainly to well-known intracellular host restrictions of EVs with RT tropism in rodent cells. We report the evolution of variants of the common-cold-causing coxsackievirus A21, an EV with tropism for the human intercellular adhesion molecule 1 (hICAM-1), through serial passage in the lungs of mice transgenic for the hICAM-1 gene. This process was accompanied by multiple changes in the viral genome, suggesting exquisite adaptation of hICAM-1-tropic enteroviruses to the specific growth conditions within the RT. In vivo mouse RT-adapted, variant coxsackievirus A21 exhibited replication competence in the lungs of hICAM-1 transgenic mice, providing a basis for unraveling EV-host interactions in the mouse RT.

Resume L’imagerie preoperatoire des hyperparathyroidismes primaires a pour objectif premier de determiner avec precision et fiabilite la position et les rapports de la glande pathologique afin d’orienter le geste operatoire du chirurgien et de proposer des methodes de chirurgie moins invasives. La scintigraphie planaire de soustraction presente de bonnes performances diagnostiques mais dans ce cadre preoperatoire pour lequel un reperage anatomique optimal est souhaitable, on peut s’interroger sur la valeur ajoutee d’une imagerie multimodale avec fusion anatomique et fonctionnelle. Nous avons entrepris de comparer – au sein d’une population de 23 patients presentant un hyperparathyroidisme primaire – un protocole d’acquisition planaire cervicomediastinal et pinhole cervical anterieur a un protocole tomographique (TEMP) cervicomediastinal de soustraction ( 123 I/ 99m Tc-MIBI) couple a une tomodensitometrie (TDM). Le compte-rendu chirurgical et l’examen histologique constituaient les references pour la population incluse afin de mesurer les performances diagnostiques respectives. Le protocole d’acquisition TEMP/TDM de soustraction que nous avons mis en œuvre s’est revele plus sensible et plus specifique que le protocole d’acquisition planaire a la fois pour le diagnostic et la localisation precise de la glande parathyroide pathologique ; les sensibilites etaient evaluees respectivement a 76 et 56 %, les specificites a 100 et 80 %. Le protocole tomographique est apparu particulierement performant pour les glandes parathyroides d’origine superieure et pour les patients inclus qui presentaient un goitre nodulaire associe.

Many animal viruses exhibit proficient growth in transformed cells, a property that has been harnessed for the development of novel therapies against cancer. Despite overwhelming evidence for this phenomenon, understanding of the molecular mechanisms enabling tumor-cell killing is rudimentary for most viruses. We report here that growth and cytotoxicity of the prototype oncolytic poliovirus (PV), PVSRIPO, in glioblastoma multiforme (GBM) is promoted by mitogen-activated protein kinases (MAPKs) converging on the MAPK signal-integrating kinase 1 (Mnk1) and its primary substrate, the eukaryotic initiation factor (eIF) 4E. Inducing Mnk1-catalyzed eIF4E phosphorylation through expression of oncogenic Ras substantially enhanced PVSRIPO translation, replication, and cytotoxicity in resistant cells. This effect was mimicked by expression of constitutively active forms of Mnk1 and correlated with enhanced translation of subgenomic reporter RNAs. Our findings implicate Mnk1 activity in stimulation of PVSRIPO cap-independent translation, an effect that can be synergistically enhanced by inhibition of the phosphoinositide-3 kinase (PI3K).

PVS-RIPO is a genetically recombinant, non-pathogenic poliovirus chimera with a tumor-specific conditional replication phenotype. Consisting of the genome of the live attenuated poliovirus type 1 (Sabin) vaccine with its cognate IRES element replaced with that of human rhinovirus type 2, PVS-RIPO displays an inability to translate its genome in untransformed neuronal cells, but effectively does so in cells originating from primary tumors in the central nervous system or other cancers. Hence, PVS-RIPO unleashes potent cytotoxic effects on infected cancer cells and produces sustained anti-tumoral responses in animal tumor models. PVS-RIPO presents a novel approach to the treatment of patients with glioblastoma multiforme, based on conditions favoring an unconventional viral translation initiation mechanism in cancerous cells. In this review, we summarize advances in the understanding of major molecular determinants of PVS-RIPO oncolytic efficacy and safety and discuss their implications for upcoming clinical investigations.

International audience; The rationale of this work is to point out the relevance of in vivo MR images of mice obtained using a dedicated low-field system. For this purpose a small 0.1 T water-cooled electro-magnet and solenoidal radio frequency (RF) transmit–receive coils were used. All MR images were acquired in three-dimensional (3D) mode. An isolation cell was designed allowing easy placement of the RF coils and simple delivery of gaseous anesthesia as well as warming of the animal. Images with and without contrast agent were obtained in total acquisition times on the order of half an hour to four hours on normal mice as well as on animals bearing tumors. Typical in plane pixel dimensions range from 200 × 200 to 500 × 500 µm2 with slice thicknesses ranging between 0.65 and 1.50 mm. This work shows that, besides light installation and low cost, dedicated low-field MR systems are suitable for small rodents imaging, opening this technique even to small research units.

Objective This work aims at demonstrating the interest of low field magnetic resonance imaging (MRI) for in vivo imaging in rat. Material and methods MRI is performed using an open resistive 0.1 T magnet with a homogeneous zone measuring 6 cm × 10 cm × 10 cm. Rats under isoflurane gaseous anesthesia are placed in a technical cell for small animal imaging. Radio frequency solenoidal coils are developed for each application. Gradient echo T1 and T2-weighted sequences are programmed to acquire 3D data in vivo in rats. Results Acquisition times are comprised between 1 min for scout sequences and 2 h 10 min to acquire volumes with in-plane pixel size ranging from 0.37 to 1 mm and a slice thickness between 0.37 mm and 1.88 mm. Information obtained from our acquisitions are comparable to those reported in the literature about five applications: 1: intracerebral glioma; 2: cerebral contrast enhancement using manganese; 3: description of knee joint anatomy; 4: cardiac dynamic acquisition synchronized on cardiac rhythm; 5: whole body (thorax and abdomen) acquisition. Conclusion Rat MRI using an 0.1 T device allows to answer to the biological questions studied in this work at the expense of long acquisition times compared to high field MRI. Low field MRI offers economical and technical characteristics that could make it attractive to a non-specialized scientific community aiming at realizing daily MRI in vivo in rat.

Ultra high molecular polyethylene (UHMWPE) is used in artificial knee joints and therefore subjected to cyclic loading. The hysteretic thermo-mechanical response of medical grade ultra high molecular weight polyethylene under compressive cyclic loading at high stress levels was investigated. It was shown that the repeated loading leads to heat dissipation that heavily alters the properties of the polyethylene and is crucial to its fatigue behaviour.

This article reviews and explains the basic physical principles of metal-induced MRI artifacts, describes simple ways to reduce them, and presents specific reduction solutions. Artifacts include signal loss, pile-up artifacts, geometric distortion, and failure of fat suppression. Their nature and origins are reviewed and explained though schematic representations that ease the understanding. Then, optimization of simple acquisition parameters is detailed. Lastly, dedicated sequences and options specifically developed to reduce metal artifacts (VAT, SEMAC, and MAVRIC) are explained.

This overview first summarizes the last decade of continuous developments and improvements in pre-clinical imaging methods that are now essential tools for in vivo evaluation of cardiac morphology and function in living mice, involving nuclear emission of labeled molecules (micro-PET and micro-SPECT) and electromagnetic wave interactions with biological tissues (micro-CT and micro-MRI). In the following, and for better understanding, the basic physical principles and specific technical innovations of the aforementioned imaging methods are reviewed. Specificity, sensitivity, and spatial and temporal resolutions, together with the corresponding advantages and weaknesses of each method are then discussed, and cardiac image-acquisition protocols and illustrative examples are given for each modality. Emerging hybrid cardiac imaging is also presented and illustrated. Then, recent biological insights provided by mouse cardiac imaging are presented. Finally, imaging strategies in mouse cardiac phenotyping involving the aforementioned methods, adding metabolic and molecular information to morphological data, are emphasized and discussed. Curr. Protoc. Mouse Biol. 2:129-144 © 2012 by John Wiley & Sons, Inc.

Resume Objectif Developper la methodologie d'acquisition et de traitement des donnees scintigraphiques fonctionnelles hepatobiliaires chez la souris normale. Materiel et methodes L'etude scintigraphique a ete realisee a l'aide d'une gamma-camera dediee a l'imagerie du petit animal sur 11 souris femelles adultes CD1 sous anesthesie gazeuse. L'acquisition comportait une serie dynamique de 40 images sequentielles d'une minute apres injection intraveineuse de mebrofenine technetiee. Deux individus ont ete utilises pour des acquisitions morphologiques tomodensitometriques par microscanner X avec injection de produit de contraste et ont contribue au choix du placement des regions d'interet scintigraphiques. Quatre modeles analytiques : hepatogramme corrige et deconvolue (A), modele bicompartimental (B), modele a cinetique rapide (C) et analyse factorielle (D) ont ete appliques aux donnees scintigraphiques a partir des regions d'interet centrees sur les cavites cardiaques et le foie. Resultats La cinetique hepatobiliaire de la mebrofenine est caracterisee par un temps du maximum tmax compris entre 4,5 et 4,6 minutes, un temps du centre de gravite tcdg de 6,2 a 7,0 minutes et une demi-vie de decroissance exponentielle t1/2decr de 5,4 a 6,8 minutes, une fraction d'extraction hepatique de 100 %. Les temps de captation et d'excretion sont de 2,3 et 5,8 minutes pour le modele bicompartimental et de 3,2 et 3,3 minutes pour le modele a cinetique rapide. Les comparaisons ne retrouvent pas de difference significative entre les foies droit et gauche ni entre les modeles A, B, C et D pour les constantes de captation ni entre les modeles A, B et D pour les constantes de d'excretion. Conclusion Differentes modelisations compartimentales ont permis d'obtenir des valeurs de reference de la fonction hepatobiliaire pour la souris normale CD1.

Our aim was to conduct a quantitative and qualitative evaluation of high-resolution skull-bone imaging for dentistry and otolaryngology using different architectures of recent X-ray computed tomography systems.Three multi-slice computed tomography (MSCT) systems and one Cone-beam computed tomography (CBCT) system were used in this study. All apparatuses were tested with installed acquisition modes and proprietary reconstruction software enabling high-resolution bone imaging. Quantitative analyses were performed with small fields of view with the preclinical vmCT phantom, which permits to measure spatial resolution, geometrical accuracy, linearity and homogeneity. Ten operators performed visual qualitative analyses on the vmCT phantom images, and on dry human skull images.Quantitative analysis showed no significant differences between protocols in terms of linearity and geometric accuracy. All MSCT systems present a better homogeneity than the CBCT. Both quantitative and visual analyses demonstrate that CBCT acquisitions are not better than the collimated helical MSCT mode.Our results demonstrate that current high-resolution MSCT protocols could exceed the performance of a previous generation CBCT system for spatial resolution and image homogeneity.• Quantitative evaluation is a prerequisite for comparison of imaging equipment. • Bone imaging quality could be objectively assessed with a phantom and dry skull. • The current MSCT shows better image quality than a dental CBCT system. • CBCT remains a work-in-progress technology.

The understanding of the flow structures and the particle transport/deposition across the human bronchial system remains a challenge to achieve because of the complexity of the geometry of human lungs. This work relies a strong collaboration between physicians, medical imaging researchers, fluid mechanics researcher and CFD researchers. Four configurations of airways (the generic Weibel model, the Human model proposed by Hiroko Kitaoka, a realistic Rat lung obtained by \(\mu \)-CT and a realistic rabbit geometry obtained by a synchrotron based CT) have been generated, meshed and simulated using the CFD commercial package CFD-ACE. Both steady and realistic inflow rates have been studied as well as the associated transport and deposition of particles.

PURPOSE In patients experiencing colorectal carcinoma, exhaustive analysis of indicates extent of hepatic and pulmonary surgery that prolongs survival of patients. PATIENTS AND METHODS To localize metastasis, we compared 2 F-FDG PET-CT imaging protocols, early respiratory gated scan, and delayed scan, to standard PET imaging procedure. SUVmax and lesion-to-healthy tissue ratio were measured in 60 pulmonary and 21 hepatic lesions by each of the 2 imaging protocols. RESULTS In the liver, metastatic lesion-to-healthy tissue ratios significantly increased on delayed scans as compared with early scans (P < 0.001). Better ratios could not be obtained when using respiratory gated scans, whereas more lesions were detected on delayed scans. In the lungs, metastatic lesion- to-healthy tissue ratio increased significantly on delayed scans for largest lesions (P < 0.001). Ratios were not better when exploring smallest metastatic lesions or when using respiratory gated scans. Factors interfering with F-FDG PET-CT sensitivity are discussed, such as respiratory motion and high FDG physiological uptake in healthy liver parenchyma. CONCLUSIONS Our studies indicate that routine acquisitions should use delayed hepatic scans for all patients referred for evaluation, recurrence check, or monitoring of colorectal adenocarcinoma. Delayed pulmonary scans are useful for the largest metastatic lesions and should be used in addition to early scan. In our experience, respiratory gated scans seem to be less convenient because of a low sensitivity in detection, as compared with the delayed technique; in addition, this technique is currently complicated by some technical issues, although these might be overcome with new gated protocols.

At the southern end of the Gregory Rift Valley, Lake Magadi occupies the bottom of a relatively large drainage basin. It is presently covered by a thick trona crust, which overlies two silty-clay units deposited during Late Pleistocene high lake stands. These units consist of a mixture of detrital grains (anorthoclase, amphiboles, quartz), clays (illite, authigenic zeolites), phosphates, and sedimentary sodium silicates and cherts. A late diagenetic calcite is occasionally observed. The authigenic and/or diagenetic mineralogical phases were extracted and analyzed for their uranium and thorium isotope contents. All yielded highly correlated ( 234 U 232 Th vs. 238 U 232 Th ) and ( 230 Th 232 Th vs. 234 U 232 Th ) isochrons defining two-component mixing systems (detrital and authigenic phases). The detrital component is characterized by large excesses of 230Th (over 234U) and by 230 Th 232 Th ratios carrying an imprint of the source rocks (e.g., Precambrian basement vs. volcanics) and indicating efficient uranium-leaching processes during the previous pedologic cycle. The slope of the isochrons defines the 234 U 238 U and 230 Th 234 U ratios of the authigenic component, i.e., the age of the uranium-uptake episode. Zeolites yield an age of 10.4 ± 0.6 ka. This age is in agreement with the 14C chronology already established for the most recent high lake level episode in the basin (10,000–12,000 yr Bp). Sodium-silicates and cherts yield distinct ages of 98.5 ± 20 and 6 ± 3 ka, respectively, for the lower and upper lacustrine units. These ages allow the conclusion that (1) sedimentary silicates are of late diagenetic origin, and (2) that the lower lacustrine unit was deposited during a former high Lake Magadi level, possibly during the lacustrine episode dated at 135 ± 10 ka from uranium-series measurements on littoral stromatolites. Finally, the late diagenetic calcite, which yields an age of about 5 ka, indicates a significant change in the sediment interstitial water chemistry. This is also shown by the occurrence of calcitic oncolites in flat deposits assigned to a mid-Holocene minor oscillation of Lake Magadi level on the basis of their 14C ages. It is concluded that uranium-series measurements in diagenetic minerals may give access to the age of their formation.

The aim of this study was to monitor in vivo with low field MRI growth of a murine orthotopic glioma model following a suicide gene therapy.The gene therapy consisted in the stereotactic injection in the mice brain of a modified vaccinia virus Ankara (MVA) vector encoding for a suicide gene (FCU1) that transforms a non toxic prodrug 5-fluorocytosine (5-FC) to its highly cytotoxic derivatives 5-fluorouracil (5-FU) and 5'-fluorouridine-5'monophosphate (5'-FUMP). Using a warmed-up imaging cell, sequential 3D T1 and T2 0.1T MRI brain examinations were performed on 16 Swiss female nu/nu mice bearing orthotopic human glioblastoma (U87-MG cells). The 6-week in vivo MRI follow-up consisted in a weekly measurement of the intracerebral tumor volume leading to a total of 65 examinations. Mice were divided in four groups: sham group (n=4), sham group treated with 5-FC only (n=4), sham group with injection of MVA-FCU1 vector only (n=4), therapy group administered with MVA-FCU1 vector and 5-FC (n=4). Measurements of tumor volumes were obtained after manual segmentation of T1- and T2-weighted images.Intra-observer and inter-observer tumor volume measurements show no significant differences. No differences were found between T1 and T2 volume tumor doubling times between the three sham groups. A significant statistical difference (p0.05) in T1 and T2 volume tumor doubling times between the three sham groups and the animals treated with the intratumoral injection of MVA-FCU1 vector in combination with 2 weeks per os 5-FC administration was demonstrated.Preclinical low field MRI was able to monitor efficacy of suicide gene therapy in delaying the tumor growth in an in vivo mouse model of orthotopic glioblastoma.

Resume La dialyse peritoneale occupe une place importante dans la prise en charge de l’insuffisance renale au stade terminal, notamment chez le jeune enfant. L’optimisation de son efficacite necessite l’emploi de solutions de dialyse biocompatibles mais aussi l’amelioration du recrutement de la surface peritoneale d’echange (SPE). Les modeles experimentaux animaux sont une etape essentielle pour mesurer la SPE. Nous proposons une methode, rapide, de mesure in vivo de la SPE chez le rat a l’aide de donnees de microtomodensitometrie (μTDM) et a partir de la mesure du volume de dialysat obtenu par dilution isotopique de nanocolloides-99mTc.

Resume La cardiomyopathie de Takotsubo (CTT), decrite initialement au debut des annees 1990, represente 1 a 2 % des evenements cardiaques aigus et fait partie des diagnostics differentiels du syndrome coronarien aigu (SCA). Les examens isotopiques suivants : tomoscintigraphie myocardique au 201Tl (ou 99mTc-tetrofosmine), a la 123I-meta-IodoBenzyl-Guanidine (123I-mIBG) et tomographie par emission de positons (TEP)-tomodensitometrie (TDM) au 18F-flurodesoxyglucose (FDG) ont permis respectivement l’etude de la perfusion, de l’innervation et du metabolisme ventriculaire gauche (VG) afin d’evaluer l’apport de ces techniques chez des patients atteints de CTT. Dans les 15 jours suivant le declenchement de la maladie, quatre patients ont beneficie d’une tomoscintigraphie myocardique de perfusion et d’une tomoscintigraphie myocardique a la 123I-mIBG. Un TEP-FDG cardiaque a aussi ete realise chez deux d’entre eux. Nous avons reevalue l’innervation et le metabolisme myocardique trois mois et plus de six mois apres la phase aigue et compare le niveau de fixation des radionucleides. La perfusion du VG etait normale chez tous les patients, alors que l’examen a la 123I-mIBG et le TEP-FDG cardiaque montraient en phase subaigue une hypofixation apicale. L’association d’une perfusion normale et d’un metabolisme glucidique altere etait en faveur d’un aspect de « discordance inverse » entre la perfusion et le metabolisme dans la region apicale du VG. Les anomalies de fixation initiales de la 123I-mIBG et du FDG tendaient a se normaliser sur les examens ulterieurs. Les resultats ont montre la part neurogene preponderante dans l’etat de sideration myocardique apicale definissant la CTT. La tomoscintigraphie myocardique a la 123I-mIBG est l’examen a retenir pour eliminer plus facilement ce diagnostic parmi les diagnostics differentiels de SCA.

International audience; Localization of regions with increased uptake of radiotracer in small-animal SPECT is greatly facilitated when using coregistration with anatomic images of the same animal. As MRI has several advantages compared with CT (soft-tissue contrast and lack of ionizing radiation) we developed a SPECT/low-field MRI hybrid device for small-animal imaging.Methods: A small-animal single-pinhole gamma-camera (pinhole, 1.5 mm in diameter and 12 cm in focal length) adjacent to a dedicated low-field (0.1 T) small MR imager (imaging volume, 10 x 10 x 6 cm(3)) was used. The animal was placed in a warmed nonmagnetic polymethyl methacrylate imaging cell for MR acquisition, which was followed immediately by SPECT after translation of the imaging cell from one modality to the other. 3-Dimensional T1-weighted sequences were used for MRI. Phantom studies enabled verification of a low attenuation (10%) for (99m)Tc and (201)Tl and a very slight increase in Compton scattering due to the radiofrequency coil and polymethyl methacrylate imaging cell.Results: SPECT/MRI data acquisition and image coregistration of selected examples using different radiotracers for lungs, kidneys, and brain were obtained in 3 nude mice with isotropic spatial resolutions of 0.5 x 0.5 x 0.5 mm(3) for MRI and 1 x 1 x 1 mm(3) for SPECT. The total acquisition time for combined SPECT and MRI lasted 1 h 45 min.Conclusion: A low-magnetic-field strength of 0.1 T is a simple and useful solution for a small-animal dual-imaging device combining pinhole SPECT with the adjacent MR imager.

Prognosis of patients with Bartholin’s gland carcinoma(BGC) is strictly related to the nodal stage at diagnosis. Thus, it iscrucial to perform reliable staging for optimal treatment planning. Inspite of wide clinical utilization of F-18 FDG PET in oncologicalroutine, its role in vulvar malignancies is not completely defined. Tokeep organs and preserve anal and ureteral function, a patient withadvanced undifferentiated BGC (FIGO IV-A) received 50 Gy to thewhole pelvis, whole vagina and bilateral inguinal lymph nodes withconcomitant chemotherapy, followed by interstitial brachytherapy.F-18 FDG PET-CT was performed at staging and after treatmentcompletion. Complete regression of the initial metabolic abnormal-ities was shown on posttreatment images, confirming the efficacy ofthe adopted conservative approach. F-18 FDG PET-CT imagingcould have a role in staging and assessing treatment efficacy inaggressive BGC. Key Words: Bartholin’s gland carcinoma, undifferentiatedcarcinoma, F-18 FDG PET, chemoradiation, brachytherapy(

Magnetic resonance elastography (MRE) is an increasingly used method for non-invasive determination of tissue stiffness. MRE has shown its ability to measure in vivo elasticity or viscoelasticity depending on the chosen rheological model. However, few data exist on quantitative comparison of MRE with reference mechanical measurement techniques. MRE has only been validated on soft homogeneous gels under both Hookean elasticity and linear viscoelasticity assumptions, but comparison studies are lacking concerning viscoelastic properties of complex heterogeneous tissues. In this context, the present study aims at comparing an MRE-based method combined with a wave equation inversion algorithm to rotational rheometry. For this purpose, experiments are performed on in vitro porcine brain tissue. The dynamic behavior of shear storage (G') and loss (G ('')) moduli obtained by both rheometry and MRE at different frequency ranges is similar to that of linear viscoelastic properties of brain tissue found in other studies. This continuity between rheometry and MRE results consolidates the quantitative nature of values found by MRE in terms of viscoelastic parameters of soft heterogeneous tissues. Based on these results, the limits of MRE in terms of frequency range are also discussed.

A magnetic resonance elastography (MRE) based method that consists in measuring dynamic viscoelastic parameters of soft matter by analysis of propagating shear waves at different frequencies is proposed. Dynamic shear tests were performed on soft gels with a dedicated magnetic resonance imaging system at low field (0.1T) and were compared with results obtained with a mechanical rotational rheometer. Storage and loss moduli were plotted against frequency with both methods and good agreement was found between their results in the shared frequency range. Therefore, it is shown that the described method could be a reliable and accessible tool for three-dimensional dynamic mechanical analysis on soft matter able to overcome dynamic range, sample dimensions and directional limitations of mechanical rheometers. Advantages and limits of the method are discussed.