Low-dose, simple, and fast grating-based X-ray phase-contrast imaging.

Phase sensitive X-ray imaging methods can provide substantially increased contrast over conventional absorption-based imaging and therefore new and otherwise inaccessible information. The use of gratings as optical elements in hard X-ray phase imaging overcomes some of the problems that have impaired the wider use of phase contrast in X-ray radiography and tomography. So far, to separate the phase information from other contributions detected with a grating interferometer, a phase-stepping approach has been considered, which implies the acquisition of multiple radiographic projections. Here we present an innovative, highly sensitive X-ray tomographic phase-contrast imaging approach based on grating interferometry, which extracts the phase-contrast signal without the need of phase stepping. Compared to the existing phase-stepping approach, the main advantages of this new method dubbed "reverse projection" are not only the significantly reduced delivered dose, without the degradation of the image quality, but also the much higher efficiency. The new technique sets the prerequisites for future fast and low-dose phase-contrast imaging methods, fundamental for imaging biological specimens and in vivo studies.

Are the light-harvesting I complexes from Rhodospirillum rubrum arranged around the reaction centre in a square geometry?

The basic photosynthetic unit containing the reaction centre and the light-harvesting I complex (RC-LHI) of the purple non-sulphur bacterium Rhodospirillum rubrum was purified and reconstituted into two-dimensional (2D) membrane crystals. Transmission electron microscopy using conventional techniques and cryoelectron microscopy of the purified single particles and of 2D crystals yielded a projection of the RC-LHI complex at a resolution of at least 1.6 nm. In this projection the LHI ring appears to have a square symmetry and packs in a square crystal lattice. The square geometry of the LHI ring was observed also in images of single isolated particles of the RC-LHI complex. However, although the LHI units are packed identically within the crystal lattice, a new rotational analysis developed here showed that the reaction centres take up one of four possible orientations within the ring. This fourfold disorder supports our interpretation of a square ring symmetry and suggests that a hitherto undetected component may be present within the photosynthetic unit.

Projecting the self to past and future in mental time

Introduction: Human experience takes place in the line of mental-time (MT) created through imagination of oneself in different time-points in past or future (self-projection in time). Here we manipulated self-projection in MT not only with respect to one's life-events but also with respect to one's faces from different past and future time-points. Methods: We here compared MTT with respect to one's facial images from different time points in past and future (study 1: MT-faces) as well as with respect to different past and future life events (study 2: MT-events). Participants were asked to make judgments about past and future face images and past and future events from three different time-points: the present (Now), eight years earlier (Past) or eight years later (Future). In addition, as a control task participants were asked to make recognition judgments with respect to faces and memory-related judgments with respect to events without changing their habitual self-location in time. Behavioral measures and functional magnetic resonance imaging (fMRI) activity after subtraction of recognition and memory related activities show both absolute MT and relative MT effects for faces and events, signifying a fundamental brain mechanism of MT, disentangled from episodic memory functions. Results: Behavioural and event-related fMRI activity showed three independent effects characterized by (1) similarity between past recollection and future imagination, (2) facilitation of judgments related to the future as compared to the past, and (3) facilitation of judgments related to time-points distant from the present. These effects were found with respect to faces and events suggesting that the brain mechanisms of MT are independent of whether actual life episodes have to be re-/pre-experienced and recruited a common cerebral network including the medial-temporal, precuneus, inferior-frontal, temporo-parietal, and insular cortices. Conclusions: These behavioural and neural data suggest that self-projection in time is a crucial aspect of MT, relying on neural structures encoding memory, mental imagery, and self. Furthermore our results emphasize the idea that mental temporal processing is more strongly directed to future prediction than to past recollection.

Identifying psychotic defenses in a clinical interview.

The Defense Mechanisms Rating Scales (DMRS), one of the most widely used and validated instruments in the study of defense mechanisms, does not include psychotic defenses. The Psychotic-DMRS (P-DMRS) has been developed to include 6 psychotic defense mechanisms: psychotic denial, autistic withdrawal, distortion, delusional projection, fragmentation, and concretization. We discuss psychotic defenses, including the difference between psychotic defenses and psychotic symptoms. Six clinical illustrations demonstrate how the 6 P-DMRS defenses can be identified in patients' narratives selected from the transcripts of dynamic interviews. Implications with respect to patient evaluation and treatment are discussed.

Bi-planar 2D-to-3D registration in Fourier domain for stereoscopic X-ray motion tracking

In this paper we present a new method to track bonemovements in stereoscopic X-ray image series of the kneejoint. The method is based on two different X-ray imagesets: a rotational series of acquisitions of the stillsubject knee that will allow the tomographicreconstruction of the three-dimensional volume (model),and a stereoscopic image series of orthogonal projectionsas the subject performs movements. Tracking the movementsof bones throughout the stereoscopic image series meansto determine, for each frame, the best pose of everymoving element (bone) previously identified in the 3Dreconstructed model. The quality of a pose is reflectedin the similarity between its simulated projections andthe actual radiographs. We use direct Fourierreconstruction to approximate the three-dimensionalvolume of the knee joint. Then, to avoid the expensivecomputation of digitally rendered radiographs (DRR) forpose recovery, we reformulate the tracking problem in theFourier domain. Under the hypothesis of parallel X-raybeams, we use the central-slice-projection theorem toreplace the heavy 2D-to-3D registration of projections inthe signal domain by efficient slice-to-volumeregistration in the Fourier domain. Focusing onrotational movements, the translation-relevant phaseinformation can be discarded and we only consider scalarFourier amplitudes. The core of our motion trackingalgorithm can be implemented as a classical frame-wiseslice-to-volume registration task. Preliminary results onboth synthetic and real images confirm the validity ofour approach.

Imagerie des bronchectasies : valeur diagnostique, fonctionnelle et pronostique.

Messages à retenir: La scanographie hélicoïdale à collimation fine sur l'ensemble du thorax est l'examen de référence pour le diagnostic et l'évaluation de la distributiontopographique et de l'étendue des bronchectasies.Les reformations multiplanaires et les techniques de projection d'intensité maximum et minimum améliorent les performances diagnostiques et permettent unemeilleure détection des lésions associées des petites voies aériennes (bronchiolite infectieuse, bronchiolite oblitérative).Chez les patients atteints de bronchectasies, le degré d'épaississement pariétal bronchique ainsi que l'étendue des zones hypodenses hypoperfusées traduisantdes lésions d'obstruction bronchiolaire sont parfaitement corrélés à la sévérité du retentissement fonctionnel de la maladie .La scanographie est peu fiable pour reconnaître le diagnostic étiologique des bronchectasies. Résumé: La scanographie hélicoïdale multidétecteur à collimation fine sur l'ensemble du thorax au cours d'une seule et même apnée inspiratoire est supérieure auxexamens en coupes fines incrémentales haute résolution avec un intervalle de coupes de 10 mm, pour le diagnostic et l'évaluation de l'étendue desbronchectasies. L'usage des reformations multiplanaires améliore la détection des bronchectasies, augmente la reproductibilité des radiologues pour lediagnostic des bronchectasies ainsi que leur niveau de confiance pour apprécier la distribution lésionnelle . L'examen scanographique évalue le nombre et ladistribution des impactions mucoïdes dans des bronches dilatées et le retentissement de l'atteinte bronchique sur les voies aériennes distales et le parenchymepulmonaire. La recherche d'atteinte associée des petites voies aériennes est systématique : détection des foyers de bronchiolite infectieuse et évaluation de l'étendue des zones hypodenses, hypoperfusées, avec piégeage, qui reflètent les lésions de bronchiolite oblitérative . Ces dernières sont corrélées au degré desévérité de l'obstruction fonctionnelle. La scanographie reste peu fiable pour le diagnostic étiologique des bronchectasies. Inversement, certains mécanismessont facilement identifiés, tels que les bronchectasies post-obstructives et les bronchectasies par traction des fibroses pulmonaires .

MDCT arthrography of the hip: value of the adaptive statistical iterative reconstruction technique and potential for radiation dose reduction.

OBJECTIVE: The purpose of this article is to assess the effect of the adaptive statistical iterative reconstruction (ASIR) technique on image quality in hip MDCT arthrography and to evaluate its potential for reducing radiation dose. SUBJECTS AND METHODS: Thirty-seven patients examined with hip MDCT arthrography were prospectively randomized into three different protocols: one with a regular dose (volume CT dose index [CTDIvol], 38.4 mGy) and two with a reduced dose (CTDIvol, 24.6 or 15.4 mGy). Images were reconstructed using filtered back projection (FBP) and four increasing percentages of ASIR (30%, 50%, 70%, and 90%). Image noise and contrast-to-noise ratio (CNR) were measured. Two musculoskeletal radiologists independently evaluated several anatomic structures and image quality parameters using a 4-point scale. They also jointly assessed acetabular labrum tears and articular cartilage lesions. RESULTS: With decreasing radiation dose level, image noise statistically significantly increased (p=0.0009) and CNR statistically significantly decreased (p=0.001). We also found a statistically significant reduction in noise (p=0.0001) and increase in CNR (p≤0.003) with increasing percentage of ASIR; in addition, we noted statistically significant increases in image quality scores for the labrum and cartilage, subchondral bone, overall diagnostic quality (up to 50% ASIR), and subjective noise (p≤0.04), and statistically significant reductions for the trabecular bone and muscles (p≤0.03). Regardless of the radiation dose level, there were no statistically significant differences in the detection and characterization of labral tears (n=24; p=1) and cartilage lesions (n=40; p≥0.89) depending on the ASIR percentage. CONCLUSION: The use of up to 50% ASIR in hip MDCT arthrography helps to reduce radiation dose by approximately 35-60%, while maintaining diagnostic image quality comparable to that of a regular-dose protocol using FBP.

Fast low-specific absorption rate B0 -mapping along projections at high field using two-dimensional radiofrequency pulses.

PURPOSE: At 7 Tesla (T), conventional static field (B0 ) projection mapping techniques, e.g., FASTMAP, FASTESTMAP, lead to elevated specific absorption rates (SAR), requiring longer total acquisition times (TA). In this work, the series of adiabatic pulses needed for slab selection in FASTMAP is replaced by a single two-dimensional radiofrequency (2D-RF) pulse to minimize TA while ensuring equal shimming performance. METHODS: Spiral gradients and 2D-RF pulses were designed to excite thin slabs in the small tip angle regime. The corresponding selection profile was characterized in phantoms and in vivo. After optimization of the shimming protocol, the spectral linewidths obtained after 2D localized shimming were compared with conventional techniques and published values from (Emir et al NMR Biomed 2012;25:152-160) in six different brain regions. RESULTS: Results on healthy volunteers show no significant difference (P > 0.5) between the spectroscopic linewidths obtained with the adiabatic (TA = 4 min) and the new low-SAR and time-efficient FASTMAP sequence (TA = 42 s). The SAR can be reduced by three orders of magnitude and TA accelerated six times without impact on the shimming performances or quality of the resulting spectra. CONCLUSION: Multidimensional pulses can be used to minimize the RF energy and time spent for automated shimming using projection mapping at high field. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Le déni de l'écrit à l'écran. L'écrivain, son oeuvre et l'univers filmique

L'article examine, à travers un grand nombre d'exemples principalement issus du cinéma hollywoodien contemporain, les implications esthétiques et narratologiques de ce « paradoxe » qui consiste à vouloir filmer l'écrivain et son travail. L'analyse de films présentant diverses formes de mise en abyme - l'écrivain y est souvent visualisé sous la forme d'une projection dans l'oeuvre qu'il écrit - permet à l'auteur de montrer comment les films tendent à développer sur le plan scénaristique des stratégies visant à compenser le déficit en termes de spectaculaire et d'action qu'implique la monstration de la matérialité de l'écrit. Il est ainsi question de la manière dont certains films exacerbent la dimension orale du verbal, optent pour des motifs tels que la panne d'inspiration de l'écrivain, associent l'écrit à un personnage qui le met en actes ou transforment le contenu de l'oeuvre d'un auteur en un monde.

Projections de l'utilisation des lits dans le canton de Vaud : hôpitaux de zone, 1990-2010

La projection utilise toujours le programme de simulation SIMULIT, dans sa treizième version. (...) Seule l'évolution démographique a été considérée dans les projections du nombre de lits: aucune des autres variables susceptibles de changer dans le futur n'a été prise en compte, ni celle en relation avec l'activité hospitalière elle-même (modification des taux d'hospitalisation, des durées de séjour, etc.), ni celles concernant l'état de santé de la population (modification de l'incidence ou de la prévalence des maladies). En d'autres termes, cette projection montre l'effet de l'évolution démographique sur l'activité hospitalière, si les caractéristiques de cette activité devaient rester celles observées dans les années 80. Il ne s'agit donc pas d'une prévision. [Auteurs, p. 1]

Flow targeted 3D steady-state free-precession coronary MR angiography: comparison of three different imaging approaches.

PURPOSE: To compare 3 different flow targeted magnetization preparation strategies for coronary MR angiography (cMRA), which allow selective visualization of the vessel lumen. MATERIAL AND METHODS: The right coronary artery of 10 healthy subjects was investigated on a 1.5 Tesla MR system (Gyroscan ACS-NT, Philips Healthcare, Best, NL). A navigator-gated and ECG-triggered 3D radial steady-state free-precession (SSFP) cMRA sequence with 3 different magnetization preparation schemes was performed referred to as projection SSFP (selective labeling of the aorta, subtraction of 2 data sets), LoReIn SSFP (double-inversion preparation, selective labeling of the aorta, 1 data set), and inflow SSFP (inversion preparation, selective labeling of the coronary artery, 1 data set). Signal-to-noise ratio (SNR) of the coronary artery and aorta, contrast-to-noise ratio (CNR) between the coronary artery and epicardial fat, vessel length and vessel sharpness were analyzed. RESULTS: All cMRA sequences were successfully obtained in all subjects. Both projection SSFP and LoReIn SSFP allowed for selective visualization of the coronary arteries with excellent background suppression. Scan time was doubled in projection SSFP because of the need for subtraction of 2 data sets. In inflow SSFP, background suppression was limited to the tissue included in the inversion volume. Projection SSFP (SNR(coro): 25.6 +/- 12.1; SNR(ao): 26.1 +/- 16.8; CNR(coro-fat): 22.0 +/- 11.7) and inflow SSFP (SNR(coro): 27.9 +/- 5.4; SNR(ao): 37.4 +/- 9.2; CNR(coro-fat): 24.9 +/- 4.8) yielded significantly increased SNR and CNR compared with LoReIn SSFP (SNR(coro): 12.3 +/- 5.4; SNR(ao): 11.8 +/- 5.8; CNR(coro-fat): 9.8 +/- 5.5; P < 0.05 for both). Longest visible vessel length was found with projection SSFP (79.5 mm +/- 18.9; P < 0.05 vs. LoReIn) whereas vessel sharpness was best in inflow SSFP (68.2% +/- 4.5%; P < 0.05 vs. LoReIn). Consistently good image quality was achieved using inflow SSFP likely because of the simple planning procedure and short scanning time. CONCLUSION: Three flow targeted cMRA approaches are presented, which provide selective visualization of the coronary vessel lumen and in addition blood flow information without the need of contrast agent administration. Inflow SSFP yielded highest SNR, CNR and vessel sharpness and may prove useful as a fast and efficient approach for assessing proximal and mid vessel coronary blood flow, whereas requiring less planning skills than projection SSFP or LoReIn SSFP.

Projections de l'utilisation des lits dans le canton de Vaud : CHUV, 1990-2010

Il faut insister sur le sens et les limites des résultats présentés ici. Seule l'évolution démographique a été considérée dans les projections du nombre de lits: aucune des autres variables susceptibles de changer dans le futur n'a été prise en compte, ni celles en relation avec l'activité hospitalière elle-même (modification des taux d'hospitalisation, des durées de séjour, etc.), ni celles concernant l'état de santé de la population (modification de l'incidence ou de la prévalence des maladies). En d'autres termes, cette projection montre l'effet de l'évolution démographique sur l'activité hospitalière, si les caractéristiques de cette activité devaient rester celles observées dans les années 80. Il ne s'agit donc pas d'une prévision. Le nombre de lits projetés constitue une sorte de référence, qui peut faciliter l'élaboration de scénarios sanitaires, ceux par exemple destinés à modifier l'effectif des lits hospitaliers. [Auteurs, p. 1]

Adaptive statistical iterative reconstruction reduces patient radiation dose in neuroradiology CT studies.

INTRODUCTION: Adaptive statistical iterative reconstruction (ASIR) can decrease image noise, thereby generating CT images of comparable diagnostic quality with less radiation. The purpose of this study is to quantify the effect of systematic use of ASIR versus filtered back projection (FBP) for neuroradiology CT protocols on patients' radiation dose and image quality. METHODS: We evaluated the effect of ASIR on six types of neuroradiologic CT studies: adult and pediatric unenhanced head CT, adult cervical spine CT, adult cervical and intracranial CT angiography, adult soft tissue neck CT with contrast, and adult lumbar spine CT. For each type of CT study, two groups of 100 consecutive studies were retrospectively reviewed: 100 studies performed with FBP and 100 studies performed with ASIR/FBP blending factor of 40 %/60 % with appropriate noise indices. The weighted volume CT dose index (CTDIvol), dose-length product (DLP) and noise were recorded. Each study was also reviewed for image quality by two reviewers. Continuous and categorical variables were compared by t test and free permutation test, respectively. RESULTS: For adult unenhanced brain CT, CT cervical myelography, cervical and intracranial CT angiography and lumbar spine CT both CTDIvol and DLP were lowered by up to 10.9 % (p < 0.001), 17.9 % (p = 0.005), 20.9 % (p < 0.001), and 21.7 % (p = 0.001), respectively, by using ASIR compared with FBP alone. Image quality and noise were similar for both FBP and ASIR. CONCLUSION: We recommend routine use of iterative reconstruction for neuroradiology CT examinations because this approach affords a significant dose reduction while preserving image quality.

La perpétuation de l'oralité du muet dans quelques incipit filmiques des premières années du parlant

Partant d'une perspective sémiotique appliquée aux débuts de film pour élargir l'approche à une réflexion historique sur l'intermédialité, cet article examine le postulat selon lequel les spectacles vivants qui précédaient la projection des films dans les années 1920 ont été en quelque sorte « happés » par le discours filmique. A travers l'examen d'un ensemble de films réalisés entre 1927 et 1937 qui accordent dans leurs génériques ou leurs prologues une place prépondérante à l'adresse vocale, l'auteur met en évidence certains phénomènes de résurgence de l'oralité propre à la période « muette », les speaker des premiers talkies endossant une fonction à certains égards similaire à celle du bonimenteur des premiers temps. L'accent est mis sur la production cinématographique de Guitry, dont la passion pour la « théâtralité » l'incite à proposer des formes singulières d'auto-mise en scène et d'adresse au spectateur. La question de la réflexivité des incipit passe également par la prise en compte de la dimension technologique, qui est parfois intégrée au film même, à l'instar de l'ouverture radiophonique de L'Atlantide de Pabst. Ces considérations s'inscrivent plus généralement dans une réflexion sur les diverses imitations de la voix vive à l'ère des technologies de l'audiovisuel.

Radiographic total disc replacement angle measurement accuracy using the Oxford Cobbometer: precision and bias.

Total disc replacement (TDR) clinical success has been reported to be related to the residual motion of the operated level. Thus, accurate measurement of TDR range of motion (ROM) is of utmost importance. One commonly used tool in measuring ROM is the Oxford Cobbometer. Little is known however on its accuracy (precision and bias) in measuring TDR angles. The aim of this study was to assess the ability of the Cobbometer to accurately measure radiographic TDR angles. An anatomically accurate synthetic L4-L5 motion segment was instrumented with a CHARITE artificial disc. The TDR angle and anatomical position between L4 and L5 was fixed to prohibit motion while the motion segment was radiographically imaged in various degrees of rotation and elevation, representing a sample of possible patient placement positions. An experienced observer made ten readings of the TDR angle using the Cobbometer at each different position. The Cobbometer readings were analyzed to determine measurement accuracy at each position. Furthermore, analysis of variance was used to study rotation and elevation of the motion segment as treatment factors. Cobbometer TDR angle measurements were most accurate (highest precision and lowest bias) at the centered position (95.5%), which placed the TDR directly inline with the x-ray beam source without any rotation. In contrast, the lowest accuracy (75.2%) was observed in the most rotated and off-centered view. A difference as high as 4 degrees between readings at any individual position, and as high as 6 degrees between all the positions was observed. Furthermore, the Cobbometer was unable to detect the expected trend in TDR angle projection with changing position. Although the Cobbometer has been reported to be reliable in different clinical applications, it lacks the needed accuracy to measure TDR angles and ROM. More accurate ROM measurement methods need to be developed to help surgeons and researchers assess radiological success of TDRs.