Magnetic Resonance

An observational study of variations in the appearance of the alar ligament on magnetic resonance imaging (MRI) and the normal range of lateral flexion and rotation of the atlas was performed to validate some of the premises underlying the use of MRI for the detection of injuries to the alar ligament. Fifteen healthy volunteers were included. Three sets of coronal proton-density images, and axial T2-weighted images of the craniovertebral junction, were obtained at 0.5 T with the neck in neutral position and laterally flexed (coronal proton density) or rotated (axial T2). Five of the subjects also underwent imaging at 1.5 T. The scans were independently examined twice by two radiologists. The presence of alar ligaments was recorded and a three-point scale used to grade the extent of hyperintensity exhibited by the structures: the ligament were graded as 2 and 3 if, respectively, less or more of its cross-section was hyperintense, whereas grade 1 represented a hypointense ligament. The effect of lateral flexion on image quality was assessed. Concordance analysis of the data were performed before and after dichotomising the data on grading. The atlanto-axial angle and rotation of the atlas were measured. The magnitude of movement to right was normalised to that to the left to give, respectively, the flexion index and the rotation index. The alar ligaments were most reliably seen on coronal proton-density scans, with a Maxwell's RE of 0.96 as compared with 0.46 for sagittal images. Flexion of the neck improved definition of the ligaments in only rare instances. Inter-observer disagreement was marked with respect to grading of the ligament on both coronal [composite proportion of agreement (p 0 )=0.44; 95% confidence intervals: 0.26, 0.64)] and sagittal scans [p 0 =0.40 (0.19, 0.63)]. Dichotomising the data did not appreciably improve reliability [Maxwell's RE: )0.11 (coronal scans), )0.20 (sagittal scans)]: for ligaments which demonstrated hypertensive areas (grades 2 and 3) there was complete lack of agreement for both coronal [p 2 =0 (0, 0.25)] and sagittal scans [p2=0 (0-0.30)]. A large response bias was found in the reports of both readers albeit in opposite directions. There was poor concordance between scans obtained at different field strengths [RE (coronal images)=0.25; RE (sagittal images)=0.14). Mean flexion index and mean rotation index were 1.00 (SD 0.03) and 1.01 (SD 0.06), respectively. The MR imaging may not be the investigation of choice for the investigation of subtle injuries to the alar ligament. Whether it can be substituted by kinematic assessment of the occipito-atlanto-axial complex with MRI warrants investigation.

Abstract. In this paper we introduce the concept of statistical deformation mod-els (SDM) which allow the construction of average models of the anatomy and their variability. SDMs are built by performing a statistical analysis of the defor-mations required to map anatomical features in one subject into the corresponding features in another subject. The concept of SDMs is similar to active shape mod-els (ASM) which capture statistical information about shapes across a population but offers several new advantages over ASMs: Firstly, SDMs can be constructed directly from images such as MR or CT without the need for segmentation which is usually a prerequisite for the construction of active shape models. Instead a non-rigid registration algorithm is used to compute the deformations required to establish correspondences between the reference subject and the subjects in the population class under investigation. Secondly, SDMs allow the construction of an atlas of the average anatomy as we...

The preparation of three new examples of water insoluble host/guest assemblies of the general composition:[(R4N)(Me3Sn) 2M (CN) 6· zH2O](R= n-propyl or n-pentyl, M= Fe or Co, 0≤ z≤ 2) from likewise polymeric super-Prussian-blue derivatives [(Me3Sn) 3M (CN) ...

Telomeric DNA consists of G-and C-rich strands that are always polarized such that the G-rich strand extends past the 3' end of the duplex to form a 12-16-base overhang. These overhanging strands can self-associate in vitro to form intramolecular structures that have several unusual physical properties and at least one common feature, the presence of non-Watson-Crick G-G base pairs. The term "G-DNA" was coined for this class of structures . On the basis of gel electrophoresis, imino proton N M R , and circular dichroism (CD) results, we find that changing the counterions from sodium to potassium (in 20 m M phosphate buffers) specifically induces conformational transitions in the G-rich telomeric D N A from Tetrahymena, d(T2G4)4 (TET4), which results in a change from the intramolecular species to an apparent multistranded structure, accompanied by an increase in the melting temperature of the base pairs of > 2 5 O , as monitored by loss of the imino proton N M R signals. N M R semiselective spin-lattice relaxation rate measurements and HPLC size-exclusion chromatography studies show that in 20 m M potassium phosphate (pH 7) buffer (KP) TET4 is approximately twice the length of the form obtained in 20 m M sodium phosphate (pH 7) buffer (Nap) and that mixtures of Na+ and K+ produce mixtures of the two forms whose populations depend on the ratio of the cations. Since K+ and NH4+ are known to stabilize a parallel-stranded quadruplex structure of poly[r(I),], we infer that the multistranded structure is a quadruplex. Our results indicate that specific differences in ionic interactions can result in a switch in telomeric DNAs between intramolecular hairpin-like or quadruplex-containing species and intermolecular quadruplex structures, all of which involve G G base pairing interactions. We propose a model in which duplex or hairpin forms of G-DNA are folding intermediates in the formation of either 1-, 2-, or 4-stranded quadruplex structures. In this model monovalent cations stabilize the duplex and quadruplex forms via two distinct mechanisms, counterion condensation and octahedral coordination to the carbonyl groups in stacked planar guanine "quartet" base assemblies. Substituting one of the guanosine residues in each of the repeats of the Tetrahymena sequence to give the human telomeric DNA, d(T2AG,)4, results in less effective K+-dependent stabilization. Thus, the ion-dependent stabilization is attenuated by altering the sequence. Upon addition of the Watson-Crick (WC) complementary strand, only the Na+-stabilized structure dissociates quickly to form a W C double helix. This demonstrates that under some circumstances the K+-stabilized G-DNA structure can be kinetically preferred over W C DNA.

A procedure to fuse the information of short-axis cine and late enhanced magnetic resonance images is presented. First a coherent 3D reconstruction of the images is obtained by objectbased interpolation of the information of contiguous slices in stacked short-axis cine acquisitions and by the correction of slice misalignments with the aid of a set of reference longaxis slices. Then, late enhanced stacked images are also interpolated and aligned with the anatomical information. Thus, the complementary information provided by both modalities is combined in a common frame of reference and in a nearly isotropic grid, which is not possible with existing fusion procedures. Numerical improvement is established by comparing the distances between unaligned and aligned manual segmentations of the myocardium in both modalities. Finally, a set of snapshots illustrate the improvement in the information overlap and the ability to reconstruct the gradient in the long-axis.

Cognition is thought to result from interactions within large-scale networks of brain regions. Here we propose a method to identify these large-scale networks using functional magnetic resonance imaging (fMRI). Regions belonging to such networks are defined as sets of strongly interacting regions, each of which showing an homogeneous temporal activity. Our method of large-scale network identification (LSNI) proceeds by first detecting functionally homogeneous regions. The networks of functional interconnections are then found by comparing the correlations among these regions against a model of the correlations in the noise.

Functional imaging in humans and anatomical data in monkeys have implicated the insula as a multimodal sensory integrative brain region. The topography of insular connections is organized by its cytoarchitectonic regions. Previous attempts to measure the insula have utilized either indirect or automated methods. This study was designed to develop a reliable method for obtaining volumetric magnetic resonance imaging (MRI) measurements of the human insular cortex, and to validate that method by examining the anatomy of insular cortex in adults with Williams syndrome (WS) and healthy age-matched controls. Statistical reliability was obtained among three raters for this method, supporting its reproducibility not only across raters, but within different software packages. The procedure described here utilizes native-space morphometry as well as a method for dividing the insula into connectivity-based sub-regions estimated from cytoarchitectonics. Reliability was calculated in both ANALYZE (n=3) and BrainImageJava (N=10) where brain scans were measured once in each hemisphere by each rater. This highly reliable method revealed total, anterior, and posterior insular volume reduction bilaterally (all p’s < .002) in WS, after accounting for reduced total brain volumes in these participants. Although speculative, the reduced insular volumes in WS may represent a neural risk for the development of hyperaffiliative social behavior with increased specific phobias, and implicate the insula as a critical limbic integrative region. Native-space quantification of the insula may be valuable in the study of neurodevelopmental or neuropsychiatric disorders related to anxiety and social behavior.

The superior capability of cognitive experts largely depends on quick automatic processes. To reveal their neural bases, we used functional magnetic resonance imaging to study brain activity of professional and amateur players in a board game named shogi. We found two activations specific to professionals: one in the precuneus of the parietal lobe during perception of board patterns, and the other in the caudate nucleus of the basal ganglia during quick generation of the best next move. Activities at these two sites covaried in relevant tasks. These results suggest that the precuneus-caudate circuit implements the automatic, yet complicated, processes of board-pattern perception and next-move generation in board game experts.

The optimal diagnostic evaluation for spontaneous intracerebral hemorrhage (ICH) remains controversial. In this retrospective study, we assessed the utility of early magnetic resonance imaging (MRI) in ICH diagnosis and management. Eighty-nine (72%) of 123 patients with spontaneous ICH underwent a brain CT and MRI within 30 days of ICH onset. Seventy patients with a mean age of 62 ± 15 years were included. A stroke neurologist and a general neurologist, each blinded to the final diagnosis, independently reviewed the admission data and the initial head CT and then assigned a presumed ICH cause under 1 of 9 categories. ICH cause was potentially modified after subsequent MRI review. The final &#39;gold standard&#39; ICH etiology was determined after review of the complete medical record by an independent investigator. Change in diagnostic category and confidence and the potential impact on patient management were systematically recorded. Mean time to MRI was 3 ± 5 days. Final ICH diagn...

The 26-residue toxin from Staphylococcus aureus, &hemolysin, is thought to act by traversing the plasma membrane. The structure of this peptide, in methanol solution, has been investigated by using high-resolution N M R in combination with molecular dynamics calculations. The 'H N M R spectrum has been completely assigned, and it is shown that residues 2-20 form a relatively stable helix while the residues at the C-terminal end appear to be more flexible. The structures were calculated only from nuclear Overhauser effect data and standard bond lengths. It is shown that the results are consistent with 3JNH-o,CH coupling constants and amide hydrogen exchange rates.

The anterior cingulate cortex (ACC) is thought to be the neuroanatomical interface between emotion and cognition. Because effective emotion-cognition interactions are essential to optimal decision making, clarifying how the functionality of the ACC changes in older age using functional imaging holds great promise for ultimately understanding what contributes to the psychological changes occurring in late life. However, the interpretation of functional imaging studies is complicated by the fact that aging is associated with changes in grey matter volume and in the cerebral vasculature. In the present study, we obtained high-resolution structural magnetic resonance (MR) imaging data and quantitative blood flow images to examine the association between aging, blood flow, and grey matter volume in the ACC. Twenty-six healthy individuals between 25 and 79 years of age underwent quantitative [ 15 O]water positron emission tomography (PET) imaging. The ACC was traced onto tissue-classified images derived from T1-and T2-weighted MRIs using previously defined methods. The ACC was divided into dorsal, rostral, and subgenual regions. Age was negatively correlated with blood flow in dorsal and rostral ACC regions. Effects were weaker but in a similar direction for the subgenual ACC. While older age and lower blood flow were both associated with smaller rostral ACC grey matter volumes, mediation analysis revealed that grey matter volume only partially mediated the effect of age on blood flow in the rostral ACC. Neural alterations not detectable on MR images may lead to reduced blood flow due to fewer and/or less metabolically active neurons. Alternatively, lower blood flow may be a cause, rather than a consequence, of smaller grey matter volume in the ACC. M., 2002. Changes in regional cerebral blood flow abnormalities in late-life depression following response to electroconvulsive therapy. Psychiatry Clin. Neurosci. 56, 31-40. Baron, R.M., Kenny, D.A., 1986. The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations. J. Pers. Soc. Psychol. 51, 1173-1182. Bennett, S.A., Tenniswood, M., Chen, J.H., Davidson, C.M., Keyes, M.T., Fortin, T., Pappas, B.A., 1998. Chronic cerebral hypoperfusion elicits neuronal apoptosis and behavioral impairment. NeuroReport 9, 161-166. ., 2001. Hippocampal and anterior cingulate activation deficits in patients with geriatric depression. Am. J. Psychiatry 158, 1321-1323. Denburg, N.L., Recknor, E.C., Bechara, A., Tranel, D., 2006. Psychophysiological anticipation of positive outcomes promotes advantageous decision-making in normal older persons. Int. J. Psychophysiol. 61, 19-25. Devinsky, O., Morrell, M.J., Vogt, B.A., 1995. Contributions of anterior cingulate cortex to behaviour. Brain 118, 279-306.

The most commonly encountered form of echo planar spectroscopy (EPS) involves oscillating gradients in one spatial dimension during readout. Data are consequently not sampled on a Cartesian grid. A fast gridding algorithm applicable to this particular situation is presented. The method is optimal, i.e., it performs as well as the full discrete Fourier transform (DFT) for band limited signals while allowing for use of the fast Fourier transform (FFT). The method is demonstrated for reconstruction of data that are partially undersampled in the time domain. The advantages of undersampling are lower hardware requirements or fewer interleaves per acquisition. The method is of particular interest when large bandwidths are needed (eg., for high field scanning) and for scanners with limited gradient performance. The unavoidable artifacts resulting from undersampling are demonstrated to be acceptable for spectroscopy with long echo times.

Intramyocellular lipid (IMCL) plays an important role in the study of metabolism in vivo. Magnetic resonance spectroscopy (MRS) studies of IMCL are usually performed with clinical 1.5-T magnetic resonance imaging (MRI) systems and have employed the single-voxel MRS technique. The present study reports the results of our systematic evaluation of the ability of single-and multi-voxel MRS to yield high-quality, contamination-free IMCL levels from the tibialis anterior (TA) muscle. A clinical, 1.5-T, whole-body MRI scanner was used to measure IMCL with a standard knee coil, head coil, or a 3-cm receive-only surface coil with a body coil transmit. Excellent IMCL spectra were obtained in healthy males in only 8 min from multiple 0.25-cm 3 voxels using the surface coil receive/body coil transmit in conjunction with the standard PRESS spectroscopic imaging (SI) technique. This approach provided the spatial resolution and voxel placement flexibility permitting optimal separation of IMCL and extramyocellular lipid. Our findings demonstrate the potential of the SI approach.

The normal anatomy and many pathologies of the pediatric genitourinary system can be assessed with different imaging modalities. Most of them are based on the use of ionizing radiation and/or invasive techniques. The contribution of magnetic resonance imaging in this regard has opened new ways of approaching pathological conditions in this patient group. The addition of the newly developed rapid techniques has enhanced the superiority of MRI, and both morphological and functional evaluation of the genitourinary system can be achieved. There are different factors on which rely the optimization and the efficiency of magnetic resonance urography (MRU). Of importance is adequate patient immobilization and the use of optimal imaging sequences. The rapid technical development, including the advent of the post-processing respiratory navigator, allows acquisition of high-quality images independent of the patient's respiratory rate. In the future, it is expected that MRU, due to its non-use of ionizing radiation, will become the most important tool in the diagnostic work-up of genitourinary pathologies in infants and small children.

To evaluate the feasibility and accuracy of magnetic resonance (MR) coronary angiography for the detection of coronary artery anomalies in infants and children by using surgical fi ndings as a reference. Materials and Methods: The data analysis was approved by the institutional review board. One hundred children with congenital heart disease underwent MR coronary angiography while under general anesthesia (mean age 6 standard deviation, 3.9 years 6 3; age range, 0.2-11 years). A navigator-gated, T2-prepared, three-dimensional steady-state free precession whole-heart protocol (isotropic voxel size, 1.0-1.3 mm 3 ; mean imaging time, 4.6 minutes 6 1.2; mean navigator effi ciency, 70%; 3-mm gating window) was used after injection of gadopentetate dimeglumine. The cardiac rest period (end systole or middiastole) and acquisition window were prospectively assessed for each patient. Coronary artery image quality (score of 0 [nondiagnostic] to 4 [excellent]), vessel sharpness, and coronary artery anomalies were assessed by two observers. Surgery was performed in 58 patients, and those fi ndings were used to defi ne accuracy. Variables were assessed between age groups by using either analysis of variance or Kruskal-Wallis tests. Results: Diagnostic image quality (score, Ն 1 for all coronary artery segments) was obtained in 46 of the 58 patients (79%) who underwent surgery. The origin and course of the coronary artery anatomy depicted with MR imaging was confi rmed at surgery in all 46 patients-including the four (9%) with substantial coronary artery anomalies. Diagnostic-quality images were obtained in 84 of the 100 patients. The rate of success improved signifi cantly when patients were older than 4 months (88% for patients. 4 months vs 17% for patients Յ 4 months, P , .001). Conclusion: Improved whole-heart MR coronary angiography enables accurate detection of abnormal origin and course of the coronary artery system even in very young patients with congenital heart disease.

Using an uncertainty paradigm and functional magnetic resonance imaging (fMRI) we studied the effect of nonspatial selective and divided visual attention on the activity of specific areas of human extrastriate visual cortex. The stimuli were single ovals that differed from an implicit standard oval in either colour or width. The subjects' task was to classify the current stimulus as one of two possible alternatives per stimulus dimension.

We used functional magnetic resonance imaging of healthy subjects to investigate the neural basis for spontaneous "willed" action. We hypothesised that such action involves prefrontal cortex (PFC) and supplementary motor area (SMA), in addition to primary motor cortex. Furthermore, we predicted that PFC and SMA would demonstrate similar temporal response dynamics, distinct from primary motor cortex. Specifically, we predicted earlier activation in PFC and SMA, manifest as shorter response latencies compared with primary motor cortex. Six right-handed males participated in an event-related design and were required to generate spontaneous motor acts inside the scanner. By deciding "which" of two buttons to press, and "when" to press them, subjects generated sequences of action that were of high information content ("novelty" or "randomness"). Utilising a short repetition time (1 s), we acquired functional images that covered most of the frontal and parietal cortices. The onset of action was associated with significant activation in bilateral PFC, left primary motor cortex, and, close to the midline, SMA. Following action, mean time to half-maximum blood oxygenation level-dependent response was significantly earlier in left PFC and SMA than primary motor cortex. Our findings suggest that neural correlates of spontaneous willed action are distributed in executive and motor centres, and that temporal response dynamics differentiate "higher" regions from subordinate motor areas.

We present a photosensitive polymer composite with superparamagnetic characteristics for the fabrication of microactuators. A uniform distribution of particles in the photosensitive polymer matrix SU-8 is achieved by applying superparamagnetic nanoparticles with the aid of a surfactant. The composite contains Fe 3 O 4 nanoparticles up to 3 vol.% (12 wt.%) with diameters of around 13 nm. Superparamagnetic composite microcantilevers are successfully fabricated and actuated in resonance by the magnetic field of an external coil.

Cerebral organization during sentence processing in English and in American Sign Language (ASL) was characterized by employing functional magnetic resonance imaging (fMRI) at 4 T. Effects of deafness, age of language acquisition, and bilingualism were assessed by comparing results from (i) normally hearing, monolingual, native speakers of English, (ii) congenitally, genetically deaf, native signers of ASL who learned English late and through the visual modality, and (iii) normally hearing bilinguals who were native signers of ASL and speakers of English. All groups, hearing and deaf, processing their native language, English or ASL, displayed strong and repeated activation within classical language areas of the left hemisphere. Deaf subjects reading English did not display activation in these regions. These results suggest that the early acquisition of a natural language is important in the expression of the strong bias for these areas to mediate language, independently of the form of the language. In addition, native signers, hearing and deaf, displayed extensive activation of homologous areas within the right hemisphere, indicating that the specific processing requirements of the language also in part determine the organization of the language systems of the brain.

Substrate reduction therapy (SRT) is considered to be a potential therapeutic option for juvenile GM2 gangliosidosis (jGM2g). We evaluated the efficacy of SRT in jGM2g, assessing neurological, neuropsychological and brain magnetic resonance imaging (MRI) outcomes over a 24-month period of treatment. In an open-label and single-center study, five jGM2g patients (mean age 14.6+/-4.5 years) received oral miglustat at doses of 100-200mg t.i.d. adjusted to body surface area. Patients underwent general and neurological examinations, neuropsychological, electrophysiological, and brain MRI studies. All patients showed neurological deterioration over the period of the study, with particularly notable worsening of gait, speech and coordination. One patient experienced acute psychosis, and another showed worsening of pre-existing epilepsy. Some neuropsychological tests showed no evidence of deterioration in the three patients with high enough cognitive functioning for reliable assessment. Profound cognitive impairment in two children precluded neuropsychological evaluation. In four patients, evaluation of brain MRI showed no changes in white matter signal abnormalities and cerebellar atrophy noted at baseline, while one patient showed progression of cerebellar and supratentorial brain atrophy. Transmission electron microscopy analysis of peripheral mononuclear cells showed reduction of intracytoplasmatic inclusions with treatment. SRT with miglustat of patients with jGM2g failed to ameliorate progressive neurological deterioration, but apparently no worsening of some areas of cognitive function tested and brain MRI lesions was noted over 24 months of treatment. The results must be interpreted with care owing to the small sample of patients and the lack of a control-arm.

Brain and cerebrospinal fluid (CSF) movements are influenced by the anatomy and mechanical properties of intracranial tissues, as well as by the waveforms of driving vascular pulsations. The authors analyze these movements so that the purely hemodynamic factors are removed and the underlying mechanical couplings between brain, CSF, and the vasculature are characterized in global fashion. These measurements were used to calculate a set of impulse response functions or modulation transfer functions, characterizing global aspects of the vasculature's mechanical coupling to the intracranial tissues, the cervical CSF, and the cervical spinal cord. These functions showed that a sudden influx of blood into the head was rapidly accommodated by some type of intracranial reserve or capacity. After this initial response, an equal volume of CSF was driven through the foramen magnum over the next 200-300 ms as the intracranial reserve relaxed to its base-line state.

In the presence of an off-resonance radiofrequency field, recovery of longitudinal magnetization to a steady state is not purely monoexponential. Under reasonable conditions with zero initial magnetization, recovery is nearly exponential and an effective relaxation rate constant R1eff = 1/T1eff can be obtained. Exact and approximate formulas for R1eff and steady-state magnetization are derived from the Bloch equations for spins

Roel A. M. Heesakkers, MD Gerrit J. Jager, MD, PhD Anke M. Hövels, MSc Bartjan de Hoop, MD Harrie C. M. van den Bosch, MD Frank Raat, MD J. Alfred Witjes, MD, PhD Peter F. A. Mulders, MD, PhD Christina Hulsbergen van der Kaa, MD, PhD Jelle O. Barentsz, MD, PhD Purpose: To prospectively evaluate the feasibility of magnetic resonance (MR) imaging with ferumoxtran-10 in patients with prostate cancer to depict lymph node metastases outside the routine pelvic lymph node dissection (PLND) area.

Transmission of compressed medical images is becoming a vital tool in telemedicine. Thus new methods are needed for efficient image compression. This study discovers the best design parameters for a data compression scheme applied to digital magnetic resonance (MR) images. The proposed technique aims at reducing the transmission cost while preserving the diagnostic information. By selecting the wavelet packet's filters, decomposition level, and subbands that are better adapted to the frequency characteristics of the image, one may achieve better image representation in the sense of lower entropy or minimal distortion. Experimental results show that the selection of the best parameters has a dramatic effect on the data compression rate of MR images. In all cases, decomposition at three or four levels with the Coiflet 5 wavelet (Coif 5) results in better compression performance than the other wavelets. Image resolution is found to have a remarkable effect on the compression rate.

An improved method for the synthesis of phosphatidylcholines from phosphatidic acid and choline is described. The technique utilizes the tetraphenylborate salt of choline together with the condensing agent 2,4,6-triisopropylbenzenesulfonyl chloride. The yields in the reaction are consistently in the range 70-75%.-Harbison, G. S., and R. G. Cri5n. Improved method for the synthesis of phosphatidylcholines. J. Lipid Res. 1984. 45: 1140-1 142. Supplementary key w o r b phosphatidylcholine proton magnetic resonance dim yristoylphosphatidylcholine

This communication reports on post-processing of continuous wave EPR spectra by a digital convolution with filter functions that are subjected to differentiation or the Kramers-Krö nig transform analytically. In case of differentiation, such a procedure improves spectral resolution in the higher harmonics enhancing the relative amplitude of sharp spectral features over the broad lines. At the same time high-frequency noise is suppressed through filtering. These features are illustrated on an example of a Lorentzian filter function that has a principal advantage of adding a known magnitude of homogeneous broadening to the spectral shapes. Such spectral distortion could be easily and accurately accounted for in the consequent least-squares data modeling. Application examples include calculation of higher harmonics from pure absorption echo-detected EPR spectra and resolving small hyperfine coupling that are unnoticeable in conventional first derivative EPR spectra. Another example involves speedy and automatic separation of fast and broad slow-motion components from spin-label EPR spectra without explicit simulation of the slow motion spectrum. The method is illustrated on examples of X-band EPR spectra of partially aggregated membrane peptides.

This paper is concerned with the problem of evaluating goodness-of-fit of a path analytic model to an interregional correlation matrix derived from functional magnetic resonance imaging (fMRI) data. We argue that model evaluation based on testing the null hypothesis that the correlation matrix predicted by the model equals the population correlation matrix is problematic because P values are conditional on asymptotic distributional results (which may not be valid for fMRI data acquired in less than 10 min), as well as arbitrary specification of residual variances and effective degrees of freedom in each regional fMRI time series. We introduce an alternative approach based on an algorithm for automatic identification of the best fitting model that can be found to account for the data. The algorithm starts from the null model, in which all path coefficients are zero, and iteratively unconstrains the coefficient which has the largest Lagrangian multiplier at each step until a model is identified which has maximum goodness by a parsimonious fit index. Repeating this process after bootstrapping the data generates a confidence interval for goodness-of-fit of the best model. If the goodness of the theoretically preferred model is within this confidence interval we can empirically say that the theoretical model could be the best model. This relativistic and data-based strategy for model evaluation is illustrated by analysis of functional MR images acquired from 20 normal volunteers during periodic performance (for 5 min) of a task demanding semantic decision and subvocal rehearsal. A model including unidirectional connections from frontal to parietal cortex, designed to represent sequential engagement of rehearsal and monitoring components of the articulatory loop, is found to be irrefutable by hypothesis-testing and within confidence limits for the best model that could be fitted to the data.

Background: Magnetic resonance follow-through (MRFT) is a new cross-sectional imaging modality with the potential to accurately stage ileal Crohn's disease (CD), while avoiding ionizing radiation and the discomfort associated with enteroclysis. We aimed to assess the reliability of this technique in assessing the extent and activity of ileal CD, and to assess its influence on subsequent management.

Imaging plays an essential role for the detection and analysis of pathologic conditions of the brachial plexus. Currently, several new techniques are used in addition to conventional 2D MR sequences to study the brachial plexus: the 3D STIR SPACE sequence, 3D heavily T2w MR myelography sequences (balanced SSFP = CISS 3D, True FISP 3D, bFFE and FIESTA), and the diffusion-weighted (DW) neurography sequence with fiber tracking reconstruction (tractography). The 3D STIR sequence offers complete anatomical coverage of the brachial plexus and the ability to slice through the volume helps to analyze fiber course modification and structure alteration. It allows precise assessment of distortion, compression and interruption of postganglionic nerve fibers thanks to the capability of performing maximum intensity projections (MIP) and multiplanar reconstructions (MPRs). The CISS 3D, b-SSFP sequences allow good visualization of nerve roots within the spinal canal and may be used for MR myelography in traumatic plexus injuries. The DW neurography sequence with tractography is still a work in progress, able to demonstrate nerves tracts, their structure alteration or deformation due to pathologic processes surrounding or located along the postganglionic brachial plexus. It may become a precious tool for the understanding of the underlying molecular pathophysiologic mechanisms in diseases affecting the brachial plexus and may play a role for surgical planning procedures in the near future.

An NMR signal from a sample in a constant stray field of a portable NMR sensor is sensitized to vibrations. The CPMG sequence is synchronized to vibrations so that the constant gradient becomes an &quot;effective&quot; square-wave gradient, leading to the vibration-induced phase accumulation. The integrating nature of the spot measurement, combined with the phase distribution due to a non-uniform gradient and/or a wave field, leads to a destructive interference, the drop in the signal intensity and changes in the echo train shape. Vibrations with amplitudes as small as 140 nm were reliably detected with the permanent gradient of 12.4 T/m. The signal intensity depends on the phase offset between the vibrations and the pulse sequence. This approach opens the way for performing elastometry and micro-rheology measurements with portable NMR devices beyond the walls of a laboratory. Even without synchronization, if a vibration frequency is comparable to 1/2TE of the CPMG sequence, the sig...

A new approach based on nonlinear inversion for autocalibrated parallel imaging with arbitrary sampling patterns is presented. By extending the iteratively regularized Gauss-Newton method with variational penalties, the improved reconstruction quality obtained from joint estimation of image and coil sensitivities is combined with the superior noise suppression of total variation and total generalized variation regularization. In addition, the proposed approach can lead to enhanced removal of sampling artifacts arising from pseudorandom and radial sampling patterns. This is demonstrated for phantom and in vivo measurements. Magn Reson Med 67:34-41, 2012.

... ŁCorrespondence to: Karol Jackowski, Laboratory of NMR Spectroscopy, Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw, Poland. E-mail: [email protected] ... 13. Harris RK, Becker ED, Cabral de Menezes SM, Goodfellow R, Granger P. Pure Appl. ...

The extent to which the brain regions associated with face processing are selective for that specific function remains controversial. In addition, little is known regarding the extent to which face-responsive brain regions are selective for human faces. To study regional selectivity of face processing, we used functional magnetic resonance imaging to examine whole brain activation in response to human faces, dog faces, and houses. Fourteen healthy right-handed volunteers participated in a passive viewing, blocked experiment. Results indicate that the lateral fusiform gyrus (Brodmann's area 37) responds maximally to both dog and human faces when compared with other sites, followed by the middle/inferior occipital gyrus (BA 18/19). Sites that were activated by houses versus dog and human faces included the medial fusiform gyrus (BA 19/37), the posterior cingulate (BA 30), and the superior occipital gyrus (BA 19). The only site that displayed significant differences in activation between dog and human faces was the lingual/medial fusiform gyrus. In this site, houses elicited the strongest activation, followed by dog faces, while the response to human faces was negligible and did not differ from fixation. The parahippocampal gyrus/amygdala was the sole site that displayed significant activation to human faces, but not to dog faces or houses. D

Background: Functional imaging studies indicate that imbalances in cortico-limbic activity and connectivity may underlie the pathophysiology of MDD. In this study, using functional Magnetic Resonance Imaging (fMRI), we investigated differences in cortico-limbic activity and connectivity between depressed patients and healthy controls. Methods: Fifteen unmedicated unipolar depressed patients and 15 matched healthy subjects underwent fMRI during which they first completed a conventional block-design activation experiment in which they were exposed to negative and neutral pictures. Next, low frequency blood oxygenation dependent (BOLD) related fluctuations (LFBF) data were acquired at rest and during steady-state exposure to neutral, positive and negative pictures. LFBF correlations were calculated between anterior cingulate cortex (ACC) and limbic regions -amygdala (AMYG), pallidostriatum (PST) and medial thalamus (MTHAL) and used as a measure of cortico-limbic connectivity. Results: Depressed patients had increased activation of cortical and limbic regions. At rest and during exposure to neutral, positive, and negative pictures cortico-limbic LFBF correlations were decreased in depressed patients compared to healthy subjects.

Disorders in verbal and emotional communication and imitation, social reciprocity and higher-order cognition observed in individuals with Autism Spectrum Disorders (ASD) are presented here as phenotypic expressions of Temporo-Spatial Processing Disorders (TSPD). TSPDs include various degrees of disability in i) processing multi-sensory stimuli online, ii) associating them into meaningful and coherent patterns and iii) producing real-time sensorymotor adjustments and motor outputs. In line with this theory, we found that slowing down the speed of facial and vocal events enhanced imitative, verbal and cognitive abilities in some ASD children, particularly those with low functioning autism. We then argue that TSPDs may result from Multi-system Brain Disconnectivity-Dissynchrony (MBD), defined as an increase or decrease in functional connectivity and neuronal synchronization within/between multiple neuro-functional territories and pathways. Recent functional magnetic resonance imaging (fMRI) and electrophysiological studies supporting MBD are outlined. Finally, we review the suspected underlying neurobiological mechanisms of MBD as evidenced in neuroimaging, genetic, environmental and epigenetic studies. Overall, our TSPD/MBD approach to ASD may open new promising avenues for a better understanding of neuro-physio-psychopathology of ASD and clinical rehabilitation of people affected by these syndromes.

Triplet state sublevel spectroscopy using optical detection of magnetic resonance (ODMR) in zero magnetic field can be successfully employed to study (i) the environment of tryptophan (Trp) residues in a protein by observing the position and structure of phosphorescence spectra, zero field ODMR transitions and triplet state sublevel kinetics, (ii) the energy transfer among Trp residues, and (iii) whether any

Large medical image datasets form a rich source of anatomical descriptions for research into pathology and clinical biomarkers. Many features may be extracted from data such as MR images to provide, through manifold learning methods, new representations of the population's anatomy. However, the ability of any individual feature to fully capture all aspects morphology is limited. We propose a framework for deriving a representation from multiple features or measures which can be chosen to suit the application and are processed using separate manifold-learning steps. The results are then combined to give a single set of embedding coordinates for the data. We illustrate the framework in a population study of neonatal brain MR images and show how consistent representations, correlating well with clinical data, are given by measures of shape and of appearance. These particular measures were chosen as the developing neonatal brain undergoes rapid changes in shape and MR appearance and were derived from extracted cortical surfaces, non-rigid deformations and image similarities. Combined single embeddings show improved correlations demonstrating their benefit for further studies such as identifying patterns in the trajectories of brain development. The results also suggest a lasting effect of age at birth on brain morphology, coinciding with previous clinical studies.

Alzheimer's disease Voxel-based morphometry T2-weighting Amyloid Grey matter pathology Voxel-based morphometry (VBM) of T1-weighted magnetic resonance (MR) images has been widely used to identify regional atrophy in neurodegenerative conditions such as Alzheimer's disease (AD). In theory, however, T2-weighting should be more sensitive to tissue pathology, though until recently, volumetric T2-weighted images were unavailable. We tested the hypothesis that T2-VBM would be more sensitive to grey matter pathology in AD than T1-VBM using the recently-developed SPACE acquisition, which provides true-3D, high-resolution T2weighted images. This was contrasted to conventional T1-weighted MPRAGE images acquired at the same session and resolution. All of the atrophic regions identified with T1-VBM were also identified with T2-VBM. Additional abnormalities were, however, identified with T2-VBM and the distribution of these bore a striking resemblance to the distribution of amyloid plaque deposition in AD, suggesting that T2-VBM detects signal changes due to histopathology over and above those attributable to atrophy. In keeping with this hypothesis, the relevant statistical tests demonstrated that the difference in sensitivity was caused by an apparent change in T2-weighted signal intensity that was not present in T1-weighted images. These results suggest that T2-VBM has the potential to advance VBM beyond atrophy detection to more expansive applications in tissue pathology mapping.