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At least 577 records · Page 32Linked to original sources
PubMed2006

[Functional magnetic resonance imaging of the gastrointestinal tract--clinical application possibilities?].

Magnetic resonance imaging (MRI) is a versatile medical imaging tool for which several new applications have been developed. Beside its broad clinical use for the detection of anatomical structures and pathologies MRI has been successfully applied for the non-invasive imaging of human organ functions, including the brain and the cardiovascular system. The use of MRI for the assessment and analysis of gastrointestinal (GI) function is a new approach that is currently performed in only a few research sites. Several characteristics make MRI an ideal technique for the direct assessment of GI physiology: MRI acquires high resolution images with excellent soft tissue contrast, it does not expose subjects to ionizing radiation, is non-invasive, and the acquisition and analysis of the images can be independently verified. In this article we summarize recent developments of MRI techniques in GI research. We will also discuss the advantages and limitations of MRI for this purpose in relation to established medical imaging tools and investigations.

Forecasting↗
PubMed2005

High-resolution imaging of bone precursor cells within the intact bone marrow cavity of living mice.

Bone precursor cells (BPCs) play a critical role in bone maintenance and regeneration. Currently, no tool exists to study BPCs or other bone marrow cell types directly within their complex microenvironment. Here, we describe in vivo magnetic resonance imaging (MRI) of anatomical structures inside the medullary cavity of the mouse femur. We demonstrate that BPCs passively labeled with iron oxide-containing particles can be monitored by MRI within the intact bone marrow at an in-plane resolution of 43x25 microm. Anatomical detail provided by MRI is complemented by functional optical imaging of reporter gene expression. Single-cell dual iron oxide-reporter gene labeling has potential for combined cell tracking and cell biology studies. In summary, we describe a versatile platform suitable for studying the biology of many bone marrow cell types in living bone.

Animals↗
PubMed1999

Male monozygotic twins discordant for periventricular nodular heterotopia and epilepsy.

PURPOSE: To determine zygosity and study cerebral structure in apparently identical twins with discordant manifestation of focal epilepsy. METHODS: Male twins in their fifth decade were scanned by using magnetic resonance imaging (MRI) to detect structural abnormalities. Zygosity was determined by using 10 microsatellite markers. RESULTS: DNA analysis showed that the twins were >99.99% likely to be monozygous; they were discordant for bilateral symmetric periventricular nodular heterotopia (PNH) and epilepsy. CONCLUSIONS: The discordant occurrence of PNH and epilepsy in monozygotic male twins carries implications with respect to somatic mosaicism, currently held to be responsible for PNH in affected male subjects.

Brain Diseases↗
PubMed2003

[New brain imaging techniques].

Neuroimaging technologies have improved neurology and neurosurgery by providing tools to look inside the brain and investigate its functions and diseases. As for any tool, the users should know the basics of each technique and be aware about their uses and limitations. Here we review these new techniques and illustrate their use with examples from studies at the University Hospital in Geneva. From all the techniques, MRI (Magnetic Resonance Imagery) has the highest spatial resolution. Taking advantage of the magnetic properties of the hydrogen nucleus, it is possible to reach a sub-millimeter resolution in 3D. When MRI images are digitized, they can be treated to perform re-slicing, segmentation and 3D reconstruction of cortical surfaces, as well as to measure anatomical structures (volumetry). Functional MRI (fMRI) is based on blood oxygenation changes when a task is performed or when epileptic activity occurred. Then it can be used to non-invasively show for example language, motor or epileptic network activation. Electromagnetic imaging techniques, based on EEG and MEG, have the power to localize in 3D the electrical activity of the brain with millisecond temporal resolution and then to follow the temporal activation of neuronal networks. These techniques use mathematical models and algorithms to compute 3D tomography from 2D recordings on the scalp. In the case of epilepsy, EEG allows epileptic foci identification among propagation sites when it is recorded with a sufficient number of electrodes (> 100) and when realistic head models are used. The functional imaging techniques from nuclear medicine (PET and SPECT) have become very useful in neuroscience to explore cerebral changes associated with neuronal pathologies as well as cognitive and sensory tasks. Many efforts have been made to develop new cameras and models to increase the range of research and clinical applications. Co-registration of structural and functional images allows us to add functional information to a structural deficit, or conversely to better interpret functional images such as PET, SPECT and EEG in terms of specific anatomy. In the case of SPECT and fMRI, substraction between ictal and interictal exams points out areas involved in epileptic processes.

Brain Diseases↗
PubMedDate not supplied

[Clinical significance of magnetic resonance and echocardiographic correlations in the evaluation of hypertrophic cardiomyopathy].

Relatively few clinical studies have investigated the role of MRI in the patients with hypertrophic cardiomyopathy. To assess MR capabilities in defining the presence, distribution and severity of left ventricular hypertrophy, the prevalence and clinical correlations of right ventricular hypertrophy and the prevalence and clinical implications of structural myocardial abnormalities, MRI and echocardiography were performed on 37 unselected patients with hypertrophic cardiomyopathy. The two methods were in agreement in 100% of cases in diagnosing the disease and classifying left ventricular hypertrophy as asymmetric, concentric or apical, and in 92% of cases in assessing the topographic distribution of hypertrophy of ventricular segments. A statistically significant linear correlation was found between echocardiographic and MR measurements of interventricular septum (r = 0.69, p < 0.0001, SEE = 4) and left posterior wall of the left ventricle (r = 0.67, p < 0.0001, SEE = 2.4). Right ventricular hypertrophy (right anterior wall diastolic thickness > 5 mm) was demonstrated by MRI in 23 of 33 patients (70%). In this group, left posterior wall thickness and left atrial diameter were higher (15 +/- 4 vs 11 +/- 2, p < 0.01 and 45 +/- 9 vs 38 +/- 5 mm, p < 0.05, respectively). On T2-weighted sequences, areas of reduced signal intensity, probably due to myocardial fibrosis, were detected in 16 cases (43%). This group was characterized by higher max. septal thickness (25 +/- 7 vs 21 +/- 6 mm, p < 0.05) and max. left posterior wall thickness (15 +/- 9 vs 7 +/- 8 mm, p < 0.05). All the three cases with dilated and hypokinetic left ventricle showed this kind of tissue abnormality. In conclusion, MRI provided clear, accurate and exhaustive data on the presence and distribution of left ventricular hypertrophy in hypertrophic cardiomyopathy. Right ventricular hypertrophy and structural abnormalities of ventricular myocardium can also be detected and quantified. Right ventricular involvement is associated with more severe hypertrophy of left ventricular posterior wall. Structural myocardial abnormalities, probably due to fibrosis, are related to the extent of left ventricular hypertrophy.

Adolescent↗
PubMed2004

Evaluation of internal lung motion for respiratory-gated radiotherapy using MRI: Part I--correlating internal lung motion with skin fiducial motion.

PURPOSE: To measure the internal lung motion due to respiration using magnetic resonance images (MRIs); to evaluate the correlation between lung motion and skin surface motion and the reliability of tracking lung motion with external fiducials. METHODS AND MATERIALS: An MRI protocol using fast gradient-echo sequences was developed to acquire dynamic cine images of the thoracoabdominal region along the axial, sagittal, and coronal planes. The subjects (3 healthy volunteers and 4 lung cancer patients) were instructed to perform normal or altered breathing during MRI. Lung vessels identified on MRI were used as anatomic landmarks for internal lung structures. From sagittal cine MRI scans, the positions of the lung vessels and skin surface were tracked and their movements measured. Correlation between the movements of the external markers and internal structures was then calculated and analyzed. RESULTS: Lung vessel motion in the superior-inferior (SI) direction correlated best with mid-upper abdominal skin surface movement (correlation coefficient, 0.89 +/- 0.09 and 0.87 +/- 0.23 for volunteers and patients, respectively). The anterior-posterior (AP) vessel motion generally correlated poorly with the skin surface movement, with marker placement on the upper chest yielding the strongest results (correlation coefficient, 0.72 +/- 0.23 and 0.44 +/- 0.27 for volunteers and patients, respectively). The strength of the correlation depended on the locations of the tracked vessels, locations of the skin surface, and subjects' breathing patterns. The best correlation was seen between the motion of an abdominal fiducial and SI lung motion. Significant intersubject variability was also observed. CONCLUSION: Movement of an external fiducial may not correlate fully with, or predict, internal lung motion. Effective monitoring of respiration may have to rely on a combination of multiple fiducials and other physiologic parameters, such as lung volume and/or air flow.

Adult↗
PubMed1994

[MRI in orthopedics: diagnosis of joint disorders].

For the visualization of joint structures, magnetic resonance imaging (MRI) has definite advantages over other imaging modalities. High soft tissue contrast and multiplanar capabilities contribute to adequate representation of the joints. With surface and special coils as well as high gradient field strengths, superior spatial resolution can be achieved, thus allowing for depiction of fine anatomical details. Newly developed pulse sequences, especially with fat suppression techniques and utilization of paramagnetic contrast agents (gadolinium complexes) have improved image contrast. Examination techniques, results and diagnostic value of MRI in various joints are discussed. Close cooperation between orthopaedic surgeons and radiologists is mandatory for effective and economically acceptable use of MRI in the diagnosis of joint disorders.

Ankle Joint↗
PubMedDate not supplied

Uniting Kraepelin and Bleuler: the psychology of schizophrenia and the biology of temporal lobe abnormalities.

Bleuler and Kraepelin are described as icons of the aggressively psychological and aggressively biologic approaches to schizophrenia. We suggest that methodologic advances in studying the function and structure of the brain now allow a reconciliation of these seemingly dissimilar approaches, particularly in the temporal lobe. We begin with a brief historic overview of these different approaches to schizophrenia and then describe structural (magnetic resonance imaging [MRI]), functional (event-related potential [ERP]), and neuropsychological studies in this disorder, including a summary of work conducted in our own laboratory. Recent MRI investigations agree on the presence of volume reductions in schizophrenia in the medial temporal lobe structures of the hippocampus-amygdala complex and of the para-hippocampal gyrus. Furthermore, two recent studies also indicate volume reductions in the superior temporal gyrus (STG). These volume reductions are most prominent in male patients and in the left hemisphere of right-handed patients with schizophrenia. Along with structural studies, there has been a burgeoning interest in MRI-clinical correlations, with volume reductions in the anterior STG being associated with hallucinations and those in the posterior STG being associated with thought disorder. Functional ERP studies also implicate the importance of the temporal lobe in schizophrenia; in addition, ERP abnormalities have been directly associated with a left greater than right MRI volume reduction of the posterior STG. Neuropsychological studies in nonpsychiatric patients are also consistent with a pattern of functional deficits shown to arise from temporal lobe abnormalities, whereas direct MRI-neuropsychological correlations in schizophrenic patients show that decreased performance on tests of verbal memory, abstraction, and categorization correlates with reduced MRI volume of left and right temporal lobe structures. Integration of these findings with those from basic neuroscience suggests a possible role of excitatory amino acid neurotransmission dysregulation and excitotoxicity in the pathology of schizophrenia. A data-based pathophysiologic characterization of schizophrenia is now becoming a reality, and the next few years should see a further unification of the Kraepelinian and Bleulerian approaches to this disorder.

Brain Mapping↗
PubMed1994

Female siblings with Pendred's syndrome.

Female siblings with Pendred's syndrome were admitted to our clinic. The abnormality of the acoustic structure was examined by MRI. Bilateral enlargement of the vestibular aqueduct and a prominently marked endolymphatic sac were found on MRI. These findings seemed likely to represent a Mondini deformity. Acoustic structure in Pendred's syndrome was examined here by MRI for the first time. We examined their HLA-DR locus as a genetic marker using the affected sib-pair method preliminary. HLA typing might be a diagnostic criteria of Pendred's syndrome, although the present siblings possessed 2 HLA genes in common.

Adolescent↗
PubMed2000

Structural and functional brain development and its relation to cognitive development.

Despite significant gains in the fields of pediatric neuroimaging and developmental neurobiology, surprisingly little is known about the developing human brain or the neural bases of cognitive development. This paper addresses MRI studies of structural and functional changes in the developing human brain and their relation to changes in cognitive processes over the first few decades of human life. Based on post-mortem and pediatric neuroimaging studies published to date, the prefrontal cortex appears to be one of the last brain regions to mature. Given the prolonged physiological development and organization of the prefrontal cortex during childhood, tasks believed to involve this region are ideal for investigating the neural bases of cognitive development. A number of normative pediatric fMRI studies examining prefrontal cortical activity in children during memory and attention tasks are reported. These studies, while largely limited to the domain of prefrontal functioning and its development, lend support for continued development of attention and memory both behaviorally and physiologically throughout childhood and adolescence. Specifically, the magnitude of activity observed in these studies was greater and more diffuse in children relative to adults. These findings are consistent with the view that increasing cognitive capacity during childhood may coincide with a gradual loss rather than formation of new synapses and presumably a strengthening of remaining synaptic connections. It is clear that innovative methods like fMRI together with MRI-based morphometry and nonhuman primate studies will transform our current understanding of human brain development and its relation to behavioral development.

Adolescent↗
PubMed2003

Pyridoxine-dependent seizures and cognition in adulthood.

A case report of neonatal onset pyridoxine-dependent seizures in a male patient with early diagnosis and treatment is presented. The patient's epilepsy was recognized and treated with pyridoxine (vitamin B6) within 8 hours of birth. Treatment has been nearly continuous since that time. This paper reports the results of a full neuropsychological evaluation at age 37 years and MRI completed at age 31 years. Consistent with other case reports in the literature, there was a significant Performance IQ (PIQ) advantage with decreased Verbal IQ (VIQ) and expressive language skills (Full-Scale IQ 71, VIQ 64, PIQ 85). MRI demonstrated characteristic thinning of the posterior corpus callosum. This report provides an example of early treatment that nonetheless results in a mild mental retardation. The similarity of the structural changes on MRI and the cognitive profile of this patient to those of others reported in the literature suggest that the underlying mechanism for both may be the same.

Adult↗
PubMed1992

[Nuclear magnetic resonance of anorectal malformations and persistent postoperative fecal incontinence].

We review our experience with Magnetic Resonance Imaging (MRI) in the evaluation of 6 patients showing anorectal malformation, and 4 more with persistent postoperative fecal incontinence. Preoperative sagittal, axial and coronal planes were studied with special consideration to the pelvic and vertebral structures. The excellent resolution of MRI allowed accurate identification of the pelvic musculature in all patients, including those with bizarre sacral abnormalities. MRI revealed structural anomalies not detected previously, such as teathering cord, intraspinal lipoma, presacral mass and renal malformation. In our institution, MRI has replaced the CT scan in the study of patients suffering of persistent fecal incontinence. In non operated on cases of anorectal malformations, MRI determines with extraordinary accuracy the location of the rectal atretic pouch, the actual pelvic muscular quality, and the detection of previously unsuspected associated anomalies.

Anal Canal↗
PubMed1997

Reliability and validity of MRI measurement of the amygdala and hippocampus in children with fragile X syndrome.

Evidence from numerous structural magnetic resonance imaging (MRI) studies has converged to implicate mesial temporal lobe structures in the pathophysiology of several developmental and psychiatric disorders. Efforts to integrate the results of these studies are challenged, however, by the lack of consistency, detail and precision in published protocols for the manual measurement of the amygdala and hippocampus. In this study, we describe a highly detailed, standardized protocol for measuring the amygdala and the hippocampus. Within the context of this protocol, we tested the inter- and intra-rater reliability of two frequently cited methods for normalizing the anatomical position of the amygdala and hippocampus prior to measurement. One method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the long axis of the hippocampus. The second method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the axis connecting the anterior and posterior commissures. Inter- and intra-rater reliability coefficients (using the intraclass correlation) ranged from 0.80 to 0.98, indicating that both methods for positional normalization are highly reliable. In addition, we tested the validity of each method by comparing the temporal lobe anatomy of children with fragile X syndrome to a group of unaffected children matched by age and gender. We found that hippocampal volumes in children with fragile X were significantly increased when either rotational method was used. These results replicated previous findings, suggesting that either method can be validly applied to neuronanatomic studies of pediatric populations.

Adolescent↗
PubMed1993

Solvate structures in water-methanol solutions of MRI contrast agents: electron spin echo envelope modulation in gadolinium chelates.

Electron Spin Echo Envelope Modulation (ESEEM) data are reported for three gadolinium (III) chelates, Gd-EDTA, Gd-DTPA, and Gd-TTHA, in frozen D2O/CH3OD glasses. This series includes Gd-DTPA, an MRI contrast agent that is in clinical use. Three-pulse electron spin echo modulation patterns can be modeled to yield geometrical information; e.g., distances and numbers of Gd+3-OD interactions. Interpreted by a spherical shell model, the data for Gd-TTHA are accounted for by Gd+3 surrounded by seven deuterons at an effective distance of 3.9 A. We attribute these deuterons to second-coordination sphere solvent molecules, since it is likely that Gd+3 is fully coordinated by a TTHA ligand. For analysis of ESEEM from Gd-EDTA and Gd-DTPA, the second-sphere structures of Gd-EDTA, Gd-DTPA, and Gd-TTHA are assumed equivalent. 2H-ESEEM from inner-sphere solvent molecules gives the effective distance between deuterons and Gd+3 to be approximately 2.7 A for the inner-sphere water in both EDTA and DTPA complexes. The results of simulations also give the isotropic hyperfine and quadrupole coupling constants for solvent deuterium in these systems. Possible sources of error in the determination of r and q by this method are discussed.

Chelating Agents↗
PubMed2005

Feasibility of in vivo structural analysis of high-resolution magnetic resonance images of the proximal femur.

Previously, high resolution MRI to assess bone structure of deep-seated regions of the skeleton such as the proximal femur was substantially limited by signal-to-noise ratio (SNR). With the advent of new optimized pulse sequences in MRI at 1.5 T and 3 T, it may now be possible to depict and quantify the trabecular microarchitecture in the proximal femur. The purpose of this study was to investigate the feasibility of assessing trabecular microstructure of the human proximal femur in vivo with MR imaging at 1.5 T and 3 T. MR images of six young, healthy male and female subjects were acquired using standard clinical 1.5-T and high-field 3-T whole-body MR scanners. Using a T2/T1-weighted 3D FIESTA sequence (and a 3D FIESTA-C sequence at 3 T to avoid susceptibility artifacts) a resolution of 0.234 x 0.234 x 1.5 mm(3) was achieved in vivo. Structural parameters analogous to standard bone histomorphometry were determined in femoral head and trochanter regions of interest. Bone mineral density (BMD) measurements were also obtained using dual-energy X-ray absorptiometry (DXA) for the femoral trochanter in the same subjects. The bone structure of the proximal femur is substantially better depicted at 3 T than at 1.5 T. Correlation between the structural parameters obtained at both field strengths was up to R =0.86 for both the femoral head and the trochanteric region. However, the resolution of the images limits the application of 3D structural analysis, making the assessment more akin to 2D textural measures, which may be correlated to histomorphometric but are not identical measures. This feasibility study establishes the potential of MRI as a means of imaging proximal femur structure, and improvements in technique and resolution enhancements are warranted.

Adult↗
PubMed1995

MRI evaluation of the brain in infantile neuronal ceroid-lipofuscinosis. Part 1: Postmortem MRI with histopathologic correlation.

The purpose of this study was to correlate postmortem magnetic resonance imaging (MRI) with histopathologic findings in brains of a series of autopsied patients with infantile neuronal ceroid-lipofuscinosis, a recessively inherited progressive encephalopathy. Eight formalin-fixed brains (age range at death, 7 to 13 years) were examined with MRI. One patient had also undergone brain MRI 2 years before death. Histopathologic analyses were made from standard areas selected on the basis of the MRI scans. Postmortem MRI findings did not differ significantly from the findings in the patient who was also examined during life. Typical findings were extreme cerebral atrophy and hypointensity of the gray-matter structures in relation to the white matter on T2-weighted images, a pattern the reverse of normal. Characteristic histologic findings were almost complete loss of cortical neurons and secondary loss of axons and myelin sheaths in the white matter. The drastically altered relative intensities of the gray- and white-matter structures on the MRI scans reflected replacement of the neurons with hypertrophic astrocytes and/or macrophages filled with storage material.

Brain↗
PubMed2006

Functional organization of perisylvian activation during presentation of sentences in preverbal infants.

We examined the functional organization of cerebral activity in 3-month-old infants when they were listening to their mother language. Short sentences were presented in a slow event-related functional MRI paradigm. We then parsed the infant's network of perisylvian responsive regions into functionally distinct regions based on their speed of activation and sensitivity to sentence repetition. An adult-like structure of functional MRI response delays was observed along the superior temporal regions, suggesting a hierarchical processing scheme. The fastest responses were recorded in the vicinity of Heschl's gyrus, whereas responses became increasingly slower toward the posterior part of the superior temporal gyrus and toward the temporal poles and inferior frontal regions (Broca's area). Activation in the latter region increased when the sentence was repeated after a 14-s delay, suggesting the early involvement of Broca's area in verbal memory. The fact that Broca's area is active in infants before the babbling stage implies that activity in this region is not the consequence of sophisticated motor learning but, on the contrary, that this region may drive, through interactions with the perceptual system, the learning of the complex motor sequences required for future speech production. Our results point to a complex, hierarchical organization of the human brain in the first months of life, which may play a crucial role in language acquisition in our species.

Adult↗
PubMed2005

How does DWI correlate with white matter structures?

Diffusion-weighted MRI (DWI) is widely used to characterize brain white matter (WM), particularly through the use of diffusion tensor imaging (DTI). In this study the spatial characteristics of DWI in WM of cat visual cortex were investigated at 9.4T at very high resolution. It is shown that the spatial extent of the WM tract as measured from the DWI images depends highly on the b-value. In particular, when the diffusion gradient is applied perpendicular to the main direction of the fiber tract, the estimated thickness of the tract at the commonly used b-value of 1000 s/mm2 exceeds by 50% the thickness as it appears on a T2-weighted image. Only at b-values greater than 6000 s/mm2 does the thickness of the tract approach the thickness characterized by the T2-weighted image and that observed on histological slices of the same area. Further analysis of these results indicates that the choice of b-value of 1000 s/mm2 may not be optimal for the demarcation of anisotropic WM structures. DWI at high b-value may contain spatial information that is more specific to WM tracts.

Animals↗