Direct magnetic resonance arthrography of the wrist with axial traction: A feasibility study to assess joint cartilage.

PURPOSE: To assess the impact of axial traction during acquisition of direct magnetic resonance (MR) arthrography of the wrist with regard to joint space width and amount of contrast material between the opposing cartilage surfaces. MATERIALS AND METHODS: Fifteen consecutive patients (12 male, mean age 38.1 years) were included in this Institutional Review Board-approved prospective study. Three-compartment wrist MR arthrographies were performed between October and December 2009 on a 3 T unit using a fat-suppressed T1-weighted isotropic high-resolution volumetric interpolated breathhold examination (VIBE) sequence in the coronal plane, with and without axial traction (3 kg). Two radiologists measured radiocarpal (radioscaphoid, radiolunate) and midcarpal (lunocapitate, hamatolunate) joint space widths, with and without traction, and assessed the amount of contrast material between the opposing cartilage surfaces using a three-point scale: 0 = absence, 1 = partial, 2 = complete. RESULTS: With traction, joint space width increased significantly at the radioscaphoid (Delta = 0.78 mm, P < 0.01), radiolunate (Delta = 0.18 mm, P < 0.01), and lunocapitate (Delta = 0.45 mm, P < 0.01) spaces, and both observers detected significantly more contrast material between the cartilage surfaces. At the hamatolunate space, the differences in joint space width (Delta = 0.14 mm, P = 0.54) and amount of contrast material were not significant. CONCLUSION: Direct wrist MR arthrography with axial traction of 3 kg increases joint space width at the radiocarpal and lunocapitate spaces, and prompts better coverage of the articular cartilage by the contrast material. J. Magn. Reson. Imaging 2011;. (c) 2011 Wiley-Liss, Inc.

Motion compensation strategies in magnetic resonance imaging.

Image quality in magnetic resonance imaging (MRI) is considerably affected by motion. Therefore, motion is one of the most common sources of artifacts in contemporary cardiovascular MRI. Such artifacts in turn may easily lead to misinterpretations in the images and a subsequent loss in diagnostic quality. Hence, there is considerable research interest in strategies that help to overcome these limitations at minimal cost in time, spatial resolution, temporal resolution, and signal-to-noise ratio. This review summarizes and discusses the three principal sources of motion: the beating heart, the breathing lungs, and bulk patient movement. This is followed by a comprehensive overview of commonly used compensation strategies for these different types of motion. Finally, a summary and an outlook are provided.

Neuropathological substrates and structural changes in late-life depression: the impact of vascular burden.

A first episode of depression after 65 years of age has long been associated with both severe macrovascular and small microvascular pathology. Among the three more frequent forms of depression in old age, post-stroke depression has been associated with an abrupt damage of cortical circuits involved in monoamine production and mood regulation. Late-onset depression (LOD) in the absence of stroke has been related to lacunes and white matter lesions that invade both the neocortex and subcortical nuclei. Recurrent late-life depression is thought to induce neuronal loss in the hippocampal formation and white matter lesions that affect limbic pathways. Despite an impressive number of magnetic resonance imaging (MRI) studies in this field, the presence of a causal relationship between structural changes in the human brain and LOD is still controversial. The present article provides a critical overview of the contribution of neuropathology in post-stroke, late-onset, and late-life recurrent depression. Recent autopsy findings challenge the role of stroke location in the occurrence of post-stroke depression by pointing to the deleterious effect of subcortical lacunes. Despite the lines of evidences supporting the association between MRI-assessed white matter changes and mood dysregulation, lacunes, periventricular and deep white matter demyelination are all unrelated to the occurrence of LOD. In the same line, neuropathological data show that early-onset depression is not associated with an acceleration of aging-related neurodegenerative changes in the human brain. However, they also provide data in favor of the neurotoxic theory of depression by showing that neuronal loss occurs in the hippocampus of chronically depressed patients. These three paradigms are discussed in the light of the complex relationships between psychosocial determinants and biological vulnerability in affective disorders.

Brain structure in asymptomatic FMR1 premutation carriers at risk for fragile X-associated tremor/ataxia syndrome.

Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset movement disorder affecting FMR1 premutation carriers, is associated with cerebral and cerebellar lesions. The aim of this study was to test whether computational anatomy can detect similar patterns in asymptomatic FMR1 premutation carriers (mean age 46.7 years) with qualitatively normal -appearing grey and white matter on brain MRI. We used a multimodal imaging protocol to characterize brain anatomy by automated assessment of gray matter volume and white matter properties. Structural changes in the hippocampus and in the cerebellar motor network with decreased gray matter volume in lobule VI and white matter alterations of the corresponding afferent projections through the middle cerebellar peduncles are demonstrated. Diffuse subcortical white matter changes in both hemispheres, without corresponding gray matter alterations, are only identified through age × group interactions. We interpret the hippocampal fimbria and cerebellar changes as early alterations with a possible neurodevelopmental origin. In contrast, progression of the diffuse cerebral hemispheric white matter changes suggests a neurodegenerative process, leading to late-onset lesions, which may mark the imminent onset of FXTAS.

Prenatal diagnosis of congenital lung malformations.

Prenatal diagnosis of congenital lung anomalies has increased in recent years as imaging methods have benefitted from technical improvements. The purpose of this pictorial essay is to illustrate typical imaging findings of a wide spectrum of congenital lung anomalies on prenatal US and MRI. Moreover, we propose an algorithm based on imaging findings to facilitate the differential diagnosis, and suggest a follow-up algorithm during pregnancy and in the immediate postnatal period.

Imaging of cavitary necrosis in complicated childhood pneumonia.

The aim of this study was to illustrate the chest radiographs (CR) and CT imaging features and sequential findings of cavitary necrosis in complicated childhood pneumonia. Among 30 children admitted in the Pediatric Intensive Care Unit for persistent or progressive pneumonia, respiratory distress or sepsis despite adequate antibiotic therapy, a study group of 9 children (5 girls and 4 boys; mean age 4 years) who had the radiographic features and CT criteria for cavitary necrosis complicated pneumonia was identified. The pathogens identified were Streptococcus pneumoniae( n=4), Aspergillus( n=2), Legionella( n=1), and Staphylococcus aureus( n=1). Sequential CR and CT scans were retrospectively reviewed. Follow-up CR and CT were evaluated for persistent abnormalities. Chest radiographs showed consolidations in 8 of the 9 patients. On CT examination, cavitary necrosis was localized to 1 lobe in 2 patients and 7 patients showed multilobar or bilateral areas of cavitary necrosis. In 3 patients of 9, the cavitary necrosis was initially shown on CT and visualization by CR was delayed by a time span varying from 5 to 9 days. In all patients with cavities, a mean number of five cavities were seen on antero-posterior CR, contrasting with the multiple cavities seen on CT. Parapneumonic effusions were shown by CR in 3 patients and in 5 patients by CT. Bronchopleural fistulae were demonstrated by CT alone ( n=3). No purulent pericarditis was demonstrated. The CT scan displayed persistent residual pneumatoceles of the left lower lobe in 2 patients. Computed tomography is able to define a more specific pattern of abnormalities than conventional CR in children with necrotizing pneumonia and allows an earlier diagnosis of this rapidly progressing condition. Lung necrosis and cavitation may also be associated with Aspergillus or Legionella pneumonia in the pediatric population.

Reduced fronto-temporal and limbic connectivity in the 22q11.2 deletion syndrome: vulnerability markers for developing schizophrenia?

The 22q11.2 deletion syndrome (22q11DS) is a widely recognized genetic model allowing the study of neuroanatomical biomarkers that underlie the risk for developing schizophrenia. Recent advances in magnetic resonance image analyses enable the examination of structural connectivity integrity, scarcely used in the 22q11DS field. This framework potentially provides evidence for the disconnectivity hypothesis of schizophrenia in this high-risk population. In the present study, we quantify the whole brain white matter connections in 22q11DS using deterministic tractography. Diffusion Tensor Imaging was acquired in 30 affected patients and 30 age- and gender-matched healthy participants. The Human Connectome technique was applied to register white matter streamlines with cortical anatomy. The number of fibers (streamlines) was used as a measure of connectivity for comparison between groups at the global, lobar and regional level. All statistics were corrected for age and gender. Results showed a 10% reduction of the total number of fibers in patients compared to controls. After correcting for this global reduction, preserved connectivity was found within the right frontal and right parietal lobes. The relative increase in the number of fibers was located mainly in the right hemisphere. Conversely, an excessive reduction of connectivity was observed within and between limbic structures. Finally, a disproportionate reduction was shown at the level of fibers connecting the left fronto-temporal regions. We could therefore speculate that the observed disruption to fronto-temporal connectivity in individuals at risk of schizophrenia implies that fronto-temporal disconnectivity, frequently implicated in the pathogenesis of schizophrenia, could precede the onset of symptoms and, as such, constitutes a biomarker of the vulnerability to develop psychosis. On the contrary, connectivity alterations in the limbic lobe play a role in a wide range of psychiatric disorders and therefore seem to be less specific in defining schizophrenia.

Optic perineuritis secondary to Wegener's granulomatosis.

BACKGROUND: Optic perineuritis (OPN) is an inflammatory condition involving the optic nerve sheath because of a variety of causes. We describe three patients in whom OPN was secondary to Wegener's granulomatosis (WG) and compare the clinical findings in these cases with those of idiopathic OPN. METHODS: This is a retrospective small case series derived from patients with OPN seen in an outpatient neuro-ophthalmology clinic. Medical records and imaging studies of these patients were reviewed. RESULTS: These patients shared clinical similarities with idiopathic OPN including age, sex, symptoms, radiographic findings and steroid responsiveness. However, recurrence of symptoms on lowering the prednisone dose below 40 mg distinguished these patients from those with idiopathic OPN. CONCLUSIONS: Steroid dependency in idiopathic OPN should raise suspicion of WG. Patients with OPN should be specifically questioned regarding pre-existing upper respiratory tract disorders and rheumatic symptoms and laboratory testing should include acute phase reactants, anti-neutrophil cytoplasmic antibodies and tests of renal function.

Estimation of sex and age of "virtual skeletons"--a feasibility study.

This article presents a feasibility study with the objective of investigating the potential of multi-detector computed tomography (MDCT) to estimate the bone age and sex of deceased persons. To obtain virtual skeletons, the bodies of 22 deceased persons with known age at death were scanned by MDCT using a special protocol that consisted of high-resolution imaging of the skull, shoulder girdle (including the upper half of the humeri), the symphysis pubis and the upper halves of the femora. Bone and soft-tissue reconstructions were performed in two and three dimensions. The resulting data were investigated by three anthropologists with different professional experience. Sex was determined by investigating three-dimensional models of the skull and pelvis. As a basic orientation for the age estimation, the complex method according to Nemeskéri and co-workers was applied. The final estimation was effected using additional parameters like the state of dentition, degeneration of the spine, etc., which where chosen individually by the three observers according to their experience. The results of the study show that the estimation of sex and age is possible by the use of MDCT. Virtual skeletons present an ideal collection for anthropological studies, because they are obtained in a non-invasive way and can be investigated ad infinitum.

Behavior of endogenous tumor-associated macrophages assessed in vivo using a functionalized nanoparticle.

Tumor-associated macrophages (TAMs) invade the tumor stroma in many cancers, yet their role is incompletely understood. To visualize and better understand these critical cells in tumor progression, we screened a portfolio of rationally selected, injectable agents to image endogenous TAMs ubiquitously in three different cancer models (colon carcinoma, lung adenocarcinoma, and soft tissue sarcoma). AMTA680, a functionally derivatized magneto-fluorescent nanoparticle, labeled a subset of myeloid cells with an "M2" macrophage phenotype, whereas other neighboring cells, including tumor cells and a variety of other leukocytes, remained unlabeled. We further show that AMTA680-labeled endogenous TAMs are not altered and can be tracked noninvasively at different resolutions and using various imaging modalities, e.g., fluorescence molecular tomography, magnetic resonance imaging, and multiphoton and confocal intravital microscopy. Quantitative assessment of TAM distribution and activity in vivo identified that these cells cluster in delimited foci within tumors, show relatively low motility, and extend cytoplasmic protrusions for prolonged physical interactions with neighboring tumor cells. Noninvasive imaging can also be used to monitor TAM-depleting regimen quantitatively. Thus, AMTA680 or related cell-targeting agents represent appropriate injectable vehicles for in vivo analysis of the tumor microenvironment.

In vivo detection of brain Krebs cycle intermediate by hyperpolarized magnetic resonance.

The Krebs (or tricarboxylic acid (TCA)) cycle has a central role in the regulation of brain energy regulation and metabolism, yet brain TCA cycle intermediates have never been directly detected in vivo. This study reports the first direct in vivo observation of a TCA cycle intermediate in intact brain, namely, 2-oxoglutarate, a key biomolecule connecting metabolism to neuronal activity. Our observation reveals important information about in vivo biochemical processes hitherto considered undetectable. In particular, it provides direct evidence that transport across the inner mitochondria membrane is rate limiting in the brain. The hyperpolarized magnetic resonance protocol designed for this study opens the way to direct and real-time studies of TCA cycle kinetics.

L'magerie forensique [Forensic imaging].

In recent years, modern techniques of medical imaging such as MDCT (multidetector-computed tomography) and MRI (magnetic resonance imaging) have pioneered post mortem (pm) investigations, especially in forensic medicine. Particularly pm angiography permits investigating the vascular system in a way which is not possible by performing only conventional autopsy. Beside these radiological methods, other modem visualizing techniques like the three dimensional (3D) surface scan have been implemented in order perform reconstructions of complex cases. By the use of pm imaging techniques, more objective and accurate documentations can be realized that permit an increase of quality in forensic investigations.

Using a NPWE model observer to assess suitable image quality for a digital mammography quality assurance programme.

A method of objectively determining imaging performance for a mammography quality assurance programme for digital systems was developed. The method is based on the assessment of the visibility of a spherical microcalcification of 0.2 mm using a quasi-ideal observer model. It requires the assessment of the spatial resolution (modulation transfer function) and the noise power spectra of the systems. The contrast is measured using a 0.2-mm thick Al sheet and Polymethylmethacrylate (PMMA) blocks. The minimal image quality was defined as that giving a target contrast-to-noise ratio (CNR) of 5.4. Several evaluations of this objective method for evaluating image quality in mammography quality assurance programmes have been considered on computed radiography (CR) and digital radiography (DR) mammography systems. The measurement gives a threshold CNR necessary to reach the minimum standard image quality required with regards to the visibility of a 0.2-mm microcalcification. This method may replace the CDMAM image evaluation and simplify the threshold contrast visibility test used in mammography quality.

3D visualization software to analyze topological outcomes of topoisomerase reactions.

The action of various DNA topoisomerases frequently results in characteristic changes in DNA topology. Important information for understanding mechanistic details of action of these topoisomerases can be provided by investigating the knot types resulting from topoisomerase action on circular DNA forming a particular knot type. Depending on the topological bias of a given topoisomerase reaction, one observes different subsets of knotted products. To establish the character of topological bias, one needs to be aware of all possible topological outcomes of intersegmental passages occurring within a given knot type. However, it is not trivial to systematically enumerate topological outcomes of strand passage from a given knot type. We present here a 3D visualization software (TopoICE-X in KnotPlot) that incorporates topological analysis methods in order to visualize, for example, knots that can be obtained from a given knot by one intersegmental passage. The software has several other options for the topological analysis of mechanisms of action of various topoisomerases.