A near infra-red video system as a protective diagnostic for electron cyclotron resonance heating operation in the Wendelstein 7-X stellarator.

The Wendelstein 7-X stellarator is a large nuclear fusion device based at Max-Planck-Institut für Plasmaphysik in Greifswald in Germany. The main plasma heating system for steady state operation in W7-X is electron cyclotron resonance heating (ECRH). During operation, part of plama facing components will be directly heated by the non-absorbed power of 1 MW rf beams of ECRH. In order to avoid damages of such components made of graphite tiles during the first operational phase, a near infra-red video system has been developed as a protective diagnostic for safe and secure ECRH operation. Both the mechanical design housing the camera and the optical system are very flexible and respect the requirements of steady state operation. The full system including data acquisition and control system has been successfully tested in the vacuum vessel, including on-line visualization and data storage of the four cameras equipping the ECRH equatorial launchers of W7-X.

Regional cerebral oxygen consumption, blood flow, and blood volume in healthy human aging.

Using high-resolution positron emission tomography and the oxygen 15 continuous inhalation method, we examined the changes in cerebral metabolic rate of oxygen, blood flow, blood volume, and oxygen extraction fraction as a function of age in 25 optimally healthy, unmedicated volunteers who ranged in age from 20 to 68 years. Subjects were strictly selected for absence of cerebrovascular risk factors, dementia, or mental disorders; they had neither biological nor clinical abnormalities, and no focal anomaly on computed tomographic scan. Regions of interest were determined according to the anatomical structures defined on corresponding computed tomographic scan cuts obtained using a stereotaxic head-positioning method. This same method was also used for positron emission tomographic imaging. There was no significant effect of aging on PaCO2 values, hematocrit, arterial blood pressure, cholesterol and triglyceride levels, and blood glucose levels. In most cerebral cortex gyri, the cerebral metabolic rate of oxygen significantly decreased with age according to a linear pattern, with the same magnitude (about -6% per decade) in all four lobes and on both sides. This effect of age on cortical cerebral metabolic rate of oxygen persisted when the possible influence of cortical atrophy, gender, and head size were partialled out. In contrast, the white matter, deep gray nuclei, thalamus, and cerebellum were not significantly affected. The cerebral blood volume declined with a similar pattern to cerebral metabolic rate of oxygen, while changes in cerebral blood flow were less significant, presumably because of larger variance of data across subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Positron emission tomographic studies of [11C]MDL 72222, a potential 5-HT3 receptor radioligand: distribution, kinetics and binding in the brain of the baboon.

The drug MDL 72222, a selective 5-HT3 receptor antagonist, was labelled with 11C and evaluated for distribution kinetics in brain and in vivo binding to 5-HT3 receptors using cold MDL 72222 challenge and positron emission tomography (PET), in three anaesthetized baboons. After tracer doses of [11C]MDL 72222 (i.v. bolus), 11C radioactivity was equally partitioned between plasma and blood cells and readily crossed the blood-brain barrier; it was distributed heterogeneously into 17 different structures of the brain. The kinetic curves for 11C in tissue showed a rapid initial uptake, followed by a slower ascending phase, up to about the twentieth minute and by a plateau, until the end of experiment (90 min). The plateau values indicated marked uptake in brain which, however, varied according to the region considered. In inhibition studies with cold MDL 72222 (1 mg.kg-1) as pretreatment, co-injection or displacement, no clear-cut effects on the kinetics of [11C] MDL 72222 in brain were detected in any region, including those known to be rich in 5-HT3 receptors. These observations suggest that specific binding to 5-HT3 receptors was not detectable in brain in vivo, because of the high lipophilicity (thus a great capacity for non-specific binding) of MDL 72222. These negative findings may also result from both the possible suboptimal affinity of MDL 72222 for 5-HT3 receptors in vivo and the relatively low density of 5-HT3 receptors present only in selected areas of the mammalian brain. This study is a step in the search of selective 5-HT3 receptor radioligands, adequate for in vivo applications. Slow clearance of [11C]MDL 72222 from brain tissue in baboons, should be accounted for in clinical pharmacokinetic investigations for optimal posology considerations.

Determination of 18F-fluoro-2-deoxy-D-glucose rate constants in the anesthetized baboon brain with dynamic positron tomography.

We have determined the rate constants (ki*) of 18F-fluorodeoxyglucose (FDG) in the unlesioned baboon brain, for use in positron emission tomography (PET) measurements of glucose utilization. In contrast to earlier reports, we used a radiosynthesis which guarantees production of FDG essentially uncontaminated by fluorodeoxymannose, and an improved determination of ki* by (1) direct measurement of the time-shift between bolus arrival in femoral arterial plasma and brain, (2) rapid initial PET frames, and (3) extended data acquisition (up to 180 min). Young adult baboons were studied under anesthesia with either phencyclidine or etomidate. The FDG time-activity curves obtained from temporal grey matter showed a consistent decline after about 80 min, indicating true product loss. Three-compartment modelling was performed for increasing fitting intervals (20-120 min) with both a 5-parameter (K1*-k4*, and vascular volume (Vo)) and a 4-parameter (K1*-k3*,Vo) model. With the latter, both the calculated FDG net clearance ((K* = K1*.k3*/(k2* + k3*)) and the fitted kinetic constants were dependent on fitting interval, i.e., they showed sustained unstability. With the former, the constant k4*, which presumably represents dephosphorylation, was overestimated and unstable for short fitting times (presumably due to heterogeneous brain compartments in the sample tissue), but stabilized at approximately 0.01 min-1 for fitting times > or = 80 min; K1*-k3* and K* were also stable after this time. These findings were identical for both anesthetic regimen. Thus, in the anesthetized baboon, the FDG ki* values can be reliably determined based on an adequate PET acquisition paradigm and with a model that incorporates k4* and > or = 80 min time-activity data.

Brain kinetics and specific binding of [11C]PK 11195 to omega 3 sites in baboons: positron emission tomography study.

We characterized, in vivo, using positron emission tomography in baboons, the kinetics and specific binding of i.v. injected [11C]PK 11195 to omega 3 sites in the brain. Following immediate access to brain tissue, the brain kinetics of [11C] K 11195 showed a slow elimination for the 60 min of study. Both coinjection and pulse-chase (at t = 8 min) with saturating amounts of cold PK 11195 immediately enhanced the availability of radiotracer to brain tissue, but also markedly increased the rate of washout. These effects presumably reflect displacement or inhibition of specifically bound [11C]PK 11195 to both peripheral and central omega 3 sites, respectively. These results indicate that [11C]PK 11195 has easy access and binds with moderate specificity to the normal primate brain in vivo.

Central benzodiazepine receptors in human brain: estimation of regional Bmax and KD values with positron emission tomography.

Studies of central benzodiazepine receptors in the human brain in vivo are now possible using positron emission tomography (PET) and [11C]flumazenil. With the aim of measuring Bmax and Kd in brain regions, we used a two-injection [11C]flumazenil (at high and low specific radioactivity, respectively) pseudo-equilibrium paradigm to evaluate, in seven unmedicated healthy volunteers, the relative merits of three 'reference' structures (pons, hemispheric white matter and corpus callosum) in which the free radioligand concentration in brain tissue was estimated 15-40 min after i.v. injection of the radioligand. By means of high-resolution PET, the Bmax and Kd were calculated for each subject in 18 gray matter structures, based on a two-point Scatchard plot. We found that the use of the corpus callosum as reference often resulted in spurious Bmax and Kd values. The pons was the best reference structure because it provided satisfactory Bmax values (closest to in vitro data) and most consistent Kd values, and was the region easiest to sample on PET images. The pattern of regional Bmax was consistent with that expected from in vitro studies, with values highest in the cerebral cortex, intermediate in the cerebellum, and lowest in the striatum and the thalamus. The Kd values were uniform among regions and were consistent with earlier in vitro and in vivo data. This work documents the feasibility of estimating Bmax and Kd of central benzodiazepine receptors in multiple brain regions for clinical research.

Fully automatic identification of AC and PC landmarks on brain MRI using scene analysis.

We describe a method for identification of brain structures from MRI data sets. The bulk of the paper concerns an automatic system for finding the anterior and posterior commissures [(AC) and (PC)] in the midsagittal plane. These landmarks are key for the definition of the Talairach space, commonly used in stereotactic neurosurgery, in the definition of common coordinate systems for the pooling of functional positron emission tomography (PET) images and for neuroanatomy studies. The process works according to a step-by-step procedure: it first analyzes the skull limits. A grey-level histogram is then calculated and allows an automated selection of thresholds. Then, the interhemispheric plane is detected. Following an advanced scene analysis in the midsagittal plane for anatomical structures, the AC and the PC are identified. Experimentally, with a set of 200 patients, the process never failed. Its performances and limits are comparable to that of neuroanatomy experts. Those results are due to a high degree of robustness at each step of the program.

Agraphia in Alzheimer's disease: an independent lexical impairment.

This study was conducted to delineate the pattern of the writing impairments in 12 patients with Alzheimer type dementia. The patients performed writing tasks involving regular and irregular words and nonwords given by dictation as well as a decision test composed of printed words and pictures requiring phonologic, lexical, and semantic processing. Writing from dictation demonstrated a predominant, but nonisolated, lexical deficit. In order to better evaluate this lexical disorder, the correlation between the dictation writing scores and the decision task scores was analyzed. No significant correlation was found among scores for irregular words, phonologically plausible errors, and scores of the lexical or semantic decision tasks, but there was a significant correlation among scores for the nonwords, nonphonological spelling errors, and scores of the phonologic decision task using printed words. These results would suggest that the "lexical" deficit in agraphia, i.e., difficulty in retrieval or loss of the spelling representations of words, is independent of the lexical or semantic capacities involved in other modalities.

A review of database management systems suitable for neuroimaging.

This study comprises a technical assessment of Database Management Systems (DBMS), which may be of use in the analysis of data obtained from human brain mapping procedures. Due to the large expansion of the neuroimaging field, the use of specialized database software to store and process neuroimages and their attached components is inevitable. The advent of multiple software products, a wealth of technical terms and a wide variety of other applications make the choice of a suitable program sometimes difficult. Through the inclusion of some basic and pertinent criteria (e.g., performance, ease of opening, standardization and portability), we present a descriptive comparison of 12 DBMSs currently available in the commercial and public domain. We have compared and tested three main architecture models which are currently available and assessed their potential applications for imaging purposes: relational, object-oriented, and hybrid. The findings of our study demonstrated that the Illustra software was the best suited for a neuroimaging environment because of its intrinsic ability to handle complex and large objects, such as 3D volumes or geometric structures.

VoxeLine: a software program for 3D real-time visualization of biomedical images.

The architecture and implementation of VoxeLine, a new interactive environment for display and analysis of 2D and 3D images in real-time, is discussed. This modular software project comprises two main parts: a user part (without programming expertise) and a programming part which permits its adaptation to specific problems. VoxeLine has the ability to deal with almost all sorts of data types encountered in the biomedical field (e.g. images, vectors). Another important feature is its ability to show datasets in all directions without duplicating data into the main memory. This feature allows VoxeLine to be used on machines with limited memory capacities and power. Real-time 3D manipulations (10 Hz for a 256 x 256 x 124 MRI dataset) are possible on a classic monoprocessor architecture such as a personal computer.

Modeling of the ITER-like wide-angle infrared thermography view of JET.

Infrared (IR) thermography systems are mandatory to ensure safe plasma operation in fusion devices. However, IR measurements are made much more complicated in metallic environment because of the spurious contributions of the reflected fluxes. This paper presents a full predictive photonic simulation able to assess accurately the surface temperature measurement with classical IR thermography from a given plasma scenario and by taking into account the optical properties of PFCs materials. This simulation has been carried out the ITER-like wide angle infrared camera view of JET in comparing with experimental data. The consequences and the effects of the low emissivity and the bidirectional reflectivity distribution function used in the model for the metallic PFCs on the contribution of the reflected flux in the analysis are discussed.

Thermo-mechanical analysis of ITER first mirrors and its use for the ITER equatorial visible∕infrared wide angle viewing system optical design.

ITER first mirrors (FMs), as the first components of most ITER optical diagnostics, will be exposed to high plasma radiation flux and neutron load. To reduce the FMs heating and optical surface deformation induced during ITER operation, the use of relevant materials and cooling system are foreseen. The calculations led on different materials and FMs designs and geometries (100 mm and 200 mm) show that the use of CuCrZr and TZM, and a complex integrated cooling system can limit efficiently the FMs heating and reduce their optical surface deformation under plasma radiation flux and neutron load. These investigations were used to evaluate, for the ITER equatorial port visible∕infrared wide angle viewing system, the impact of the FMs properties change during operation on the instrument main optical performances. The results obtained are presented and discussed.

Development of a realistic photonic modeling for the evaluation of infrared reflections in the metallic environment of ITER.

In nuclear fusion experiments, the plasma facing components are exposed to high heat fluxes and infrared (IR) imaging diagnostics are routinely used for surveying their surface temperature for preventing damages. However the future use of metallic components in the ITER tokamak adds complications in temperature estimation. Indeed, low and variable emissivity of the observed surface and the multiple reflections of the light coming from hot regions will have to be understood and then taken into account. In this paper, a realistic photonic modeling based on Monte Carlo ray-tracing codes is used to predict the global response of the complete IR survey system. This also includes the complex vessel geometry and the thermal and optical surface properties using the bidirectional reflectivity distribution function that models the photon-material interactions. The first results of this simulation applied to a reference torus are presented and are used as a benchmark to investigate the validity of the global model. Finally the most critical key model parameters in the reflected signals are identified and their contribution is discussed.

New field programmable gate array-based image-oriented acquisition and real-time processing applied to plasma facing component thermal monitoring.

During operation of present fusion devices, the plasma facing components (PFCs) are exposed to high heat fluxes. Understanding and preventing overheating of these components during long pulse discharges is a crucial safety issue for future devices like ITER. Infrared digital cameras interfaced with complex optical systems have become a routine diagnostic to measure surface temperatures in many magnetic fusion devices. Due to the complexity of the observed scenes and the large amount of data produced, the use of high computational performance hardware for real-time image processing is then mandatory to avoid PFC damages. At Tore Supra, we have recently made a major upgrade of our real-time infrared image acquisition and processing board by the use of a new field programmable gate array (FPGA) optimized for image processing. This paper describes the new possibilities offered by this board in terms of image calibration and image interpretation (abnormal thermal events detection) compared to the previous system.

Wall reflection issues for optical diagnostics in fusion devices.

The problem of light reflection has been raised as a high priority issue for optical diagnostics in next step fusion devices where metallic wall environment will generate significant perturbations in the diagnostics measurements. Tore Supra is a large size tokamak equipped with water-cooled stainless-steel panels used to sustain the plasma long shot radiations. These panels are highly reflective and affect significantly optical systems. In particular, we show that the infrared imaging diagnostic, which surveys the plasma facing component surface temperature for safety purposes, can give incorrect information due to reflected light coming from the bottom limiter. In the visible range, motional Stark effect and Zeff measurements experience important drifts during the plasma heating phases due to parasitic light coming from the limiter, but also from the plasma itself when the viewing lines are facing the reflecting walls. In the next step fusion devices such as ITER, the possibility to use optical measurements needs to be accessed by a modeling of the diagnostic light in its machine environment and the development of new techniques of online correction.

Engineering and manufacturing of ITER first mirror mock-ups.

Most of the ITER optical diagnostics aiming at viewing and monitoring plasma facing components will use in-vessel metallic mirrors. These mirrors will be exposed to a severe plasma environment and lead to an important tradeoff on their design and manufacturing. As a consequence, investigations are carried out on diagnostic mirrors toward the development of optimal and reliable solutions. The goals are to assess the manufacturing feasibility of the mirror coatings, evaluate the manufacturing capability and associated performances for the mirrors cooling and polishing, and finally determine the costs and delivery time of the first prototypes with a diameter of 200 and 500 mm. Three kinds of ITER candidate mock-ups are being designed and manufactured: rhodium films on stainless steel substrate, molybdenum on TZM substrate, and silver films on stainless steel substrate. The status of the project is presented in this paper.

Progress of the ITER equatorial vis/IR wide angle viewing system optical design.

The equatorial vis/IR wide angle viewing system is present in four ITER diagnostic equatorial ports. This instrument will cover a large field of view with high spatial and temporal resolutions, to provide real time temperature measurements of plasma facing components, spectral data in the visible range, information on runaway electrons, and pellet tracking. This diagnostic needs to be reliable, precise, and long lasting. Its design is driven by both the tokamak severe environment and the high performances required for machine protection. The preliminary design phase is ongoing. Paramount issues are being tackled, relative to wide spectral band optical design, material choice, and optomechanical difficulties due to the limited space available for this instrument in the ports, since many other diagnostics and services are also present. Recent progress of the diagnostic optical design and status of associated R&D are presented.

B-SPID: an object-relational database architecture to store, retrieve, and manipulate neuroimaging data.

We propose a hardware and software architecture to respond to crucial problems in the neuroimaging field: storage, retrieval, and processing of large datasets. The B-SPID project, here discussed, concerns the processing of neuroimages and attached components stored in an object-relational multimedia database management system (DBMS). Advanced bioinformation concepts are exploited in this project such as large scale data storage, high level graphical user interfaces and 3D graphical processing and display of data. Our database implementation is based on standard programming components, runs on several UNIX platforms and is written to be evolutive. Queries on this database are designed to obtain and display from neuroimaging data several types of results (pictures, text, or 3D graphical shapes) on heterogeneous systems.

Clues about the functional neuroanatomy of verbal working memory: a study of resting brain glucose metabolism in Parkinson's disease.

In addition to motor impairment, non-demented patients with Parkinson's disease (PD) exhibit a variable degree of cognitive impairment which could indicate dysfunction in the central executive of working memory. In this study, we have employed positron emission tomography measurements of resting brain glucose metabolism (CMRglc) to investigate the neural substrates underlying this dysfunction, taking PD as a model disease to assess, within the framework of Alexander's striato-pallido-thalamo-cortical cognitive circuits the functional neuroanatomy of the central executive. We studied central executive performance in 17 non-demented, highly selected PD patients, by means of the Brown-Peterson paradigm (BPP), and correlated the BPP performance according to various response delays (from 0 to 18 s) with local cerebral metabolic rates of glucose. We document for the first time that the BPP performance in PD is heterogeneous not only across delays (with PD patients selectively impaired for the 0 and 3 s delays, compatible with impaired attention and central executive, respectively), but also from subject to subject; a multiple correspondence analysis was able to distinguish two patient subgroups according to short delay BPP performance. The correlational analysis with PET data evidenced a limited number of significant correlations, most of which were consistent with our working hypothesis. Notably, a positive correlation between lateral frontal relative metabolism and BPP performance for short delays, and a negative one between these scores and mediodorsal (MD) thalamic nucleus metabolism, would fit the way in which caudate dopamine denervation would alter in opposite directions frontal cortex and MD nucleus synaptic activity and in turn affect central executive function. The results from this study lend further support to the role of altered thalamo-prefrontal interplay as the basis for central executive dysfunction in PD.

A voxel-based method for the statistical analysis of gray and white matter density applied to schizophrenia.

We describe a novel technique for characterizing regional cerebral gray and white matter differences in structural magnetic resonance images by the application of methods derived from functional imaging. The technique involves automatic scalp-editing of images followed by segmentation, smoothing, and spatial normalization to a symmetrical template brain in stereotactic Talairach space. The basic idea is (i) to convert structural magnetic resonance image data into spatially normalized images of gray (or white) matter density, effected by segmenting the images and smoothing, and then (ii) to use Statistical Parametric Mapping to make inferences about the relationship between gray (or white) matter density and symptoms (or other pathophysiological measures) in a regionally specific fashion. Because the whole brain sum of gray (or white) matter indices is treated as a confound, the analysis reduces to a characterization of relative gray (or white) matter density on a voxel by voxel basis. We suggest that this is a powerful approach to voxel-based statistical anatomy. Using the technique, we constructed maps of the regional cerebral gray and white matter density correlates of syndrome scores (distinct psychotic symptoms) in a group of 15 schizophrenic patients. There was a negative correlation between the score for the reality distortion syndrome and regional gray matter density in the left superior temporal lobe (P = 0.01) and regional white matter density in the corpus callosum (P < 0.001). These abnormalities may be associated with functional changes predisposing to auditory hallucinations and delusions. This method permits the detection of structural differences within the entire brain (as opposed to selected regions of interest) and may be of value in the investigation of structural gray and white matter abnormalities in a variety of brain diseases.