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At least 1,711 records · Page 95Linked to original sources
PubMed2001

Linking structural, metabolic and functional changes in multiple sclerosis.

In patients with multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) has markedly improved our ability to detect the macroscopic abnormalities of the brain and spinal cord. New quantitative magnetic resonance (MR) approaches with increased sensitivity to subtle normal-appearing white matter (NAWM) and grey matter changes and increased specificity to the heterogeneous pathological substrates of MS may give information complementary to conventional MRI. Magnetization transfer imaging (MTI) and diffusion-weighted imaging (DWI) have the potential to provide important information on the structural changes occurring within and outside T2-visible lesions. Magnetic resonance spectroscopy (MRS) adds information on the biochemical nature of such changes. Functional MRI might quantify the efficiency of brain plasticity in response to MS injury and improve our understanding of the link between structural damage and clinical manifestations. The present review summarizes how the application of these MR techniques to the study of MS is dramatically changing our understanding of how MS causes irreversible neurological deficits.

Central Nervous System↗
PubMed2006

Multinuclear NMR and microscopic MRI studies of the articular cartilage nanostructure.

Studies of the structure of articular cartilage by a number of NMR spectroscopic and imaging techniques are reviewed. Advantage is taken of the fact that the NMR investigations can be done non-invasively on the intact tissue and do not require sectioning, slicing and decalcification as in the case of electron microscopy. The different contributions to 1H T2 relaxation are described and it is pointed out that ignoring the biexponential behavior of the transverse relaxation can lead to serious errors in the proton density measurements and the T2 characterization of the articular cartilage. A way to slow the transverse relaxation and to minimize its angular dependence by the use of dipolar echo is described. 2H double quantum filtered spectroscopic MRI is a powerful technique to follow the orientation and density of the collagen fibers in articular cartilage. Using this technique, it was found that attachment of the cartilage to the bone has a stabilizing effect on the collagen matrix and that the hydroxyapatite in the calcified zone resides near the collagen fibers but does not contribute to their order. In response to mechanical pressure, it was shown that the collagen fibers flatten near the surface and become crimped near the bone. A number of NMR techniques have been described for the measurement of 23Na residual quadrupolar interaction. It was found that this can serve as a very sensitive measure of the depletion of proteoglycans. Finally, a combination of the above techniques was used to study a maturation of articular cartilage in pigs. The increased order and density of the collagen fibers from newborn to adult pigs revealed itself as a shortening of T2 and significant increase of the residual quadrupolar interaction of both 2H and 23Na nuclei.

Animals↗
PubMed1994

An automated image-registration technique based on multiple structure matching.

A new image-registration technique that matches multiple structures on complementary imaging data sets (e.g., CT and MRI) has been developed and tested with both phantom and patient data. The algorithm assumes a rigid-body transformation and is suitable for correlating structures within the cranium or at the skull base. The basic premise of the new technique is that an optimum transformation is achieved when the relative volume lying outside of the intersection between a structure and its transformed counterpart is a minimum. This relative volume is calculated numerically using a random sampling approach, and a binary searching algorithm was used to step through the nine-dimensional parameter space consisting of three rotation angles, three scaling factors and three components of a translation vector. For the nine tests using phantom data, the automated structure-matching technique was able to predict the correct rotation angles to within +/- 1 degree. The expected clinical performance of the new technique was assessed by comparing results obtained with the new method to those obtained using other techniques for 12 patients who were treated with charged particles at Lawrence Berkeley Laboratory (LBL) and who had image-registration studies performed as part of their treatment plan. For 9 of the 12 patients considered, the new structure-matching technique produced a significantly better registration than the older methods, as measured by the resultant average relative volume lying outside of the intersection between any structure and its transformed counterpart. For the other three patients, results were not significantly different for the new structure-matching method and the older techniques.

Algorithms↗
PubMed1987

[Magnetic resonance tomography (MRT) of the scrotum--initial results and comparison with sonography. I: Normal anatomy and extratesticular pathology].

Magnetic resonance imaging (MRI) allows for precise assessment of all important anatomic structures of the scrotum. Because the differences in signal intensity on T2-weighted images are adequate and there is high detail and contrast resolution in surface coil technique, the delineation of normal and pathologic structures greater than 1 mm is possible. Imaging in the coronal plane is preferable to that in the axial and sagittal plane. Other advantages of MRI include the possibility of comparing both hemiscrota in one imaging plane and the assessment of the inguinal region. In addition, MRI is less dependent on the expertise of the investigator. For the assessment of extratesticular pathology, MRI has advantages over other imaging techniques - including sonography - since the delineation of pathologic changes is much clearer.

Epididymitis↗
PubMed1996

MRI in acute knee dislocation. A prospective study of clinical, MRI, and surgical findings.

We treated 17 knees in 15 patients with severe ligament derangement and dislocation by open repair and reconstruction. We assessed the competence of all structures thought to be important for stability by clinical examination, MRI interpretation, and surgery. Our findings showed that in these polytrauma patients clinical examination was not an accurate predictor of the extent or site of soft-tissue injury (53% to 82% correct) due mainly to the limitations of associated injuries. MRI was more accurate (85% to 100% correct) except for a negative result for the lateral collateral ligament and posterolateral capsule. The detail and reliability of MRI are invaluable in the preoperative planning of the surgical repair and reconstruction of dislocated knees.

Acute Disease↗
PubMed2001

MRI of cortical dysplasia--correlation with pathological findings.

Cortical dysplasia (CD) is the most epileptogenic structural lesion associated with epilepsy and patients with intractable seizures caused by this condition are good surgical candidates. MRI plays an important role in detecting the abnormalities of CD. We clarified the MRI characteristics of CD by comparing imaging and histological findings in 20 patients with intractable seizures who underwent surgical resection. There were 12 males and eight females, mean age at operation was 15 years. MRI was performed at 1.5 tesla; T1-weighted, T2- and proton density-weighted spin-echo and fluid-attenuated inversion-recovery (FLAIR) images were obtained. The lesions were in the frontal lobe in nine cases, temporal in two, occipital in another two, insular in one and multilobar in six. Blurring of the grey/white matter junction was seen in all patients, and T2 prolongation in white matter and/or at the grey/white matter junction in 19. Abnormal signal intensity was more frequent in the white matter or at the grey/white matter junction than in the grey matter. FLAIR images made this abnormal high signal easier to appreciate, and we thought them very useful in this context. In areas of T2 prolongation, we saw dysplastic neurones and/or balloon cells, dysmyelination, and ectopic neuronal clustering histologically; glial proliferation played an important role in prolonging T2.

Adolescent↗
PubMed2006

Volume of cerebellar vermis in monozygotic twins discordant for combat exposure: lack of relationship to post-traumatic stress disorder.

Several functional neuroimaging studies have implicated the cerebellar vermis in post-traumatic stress disorder (PTSD), but there have been no structural neuroimaging studies of this brain structure in PTSD. We utilized magnetic resonance imaging (MRI) with manual tracing to quantify the volumes of three divisions of the mid-sagittal vermis, and their total, within an identical, co-twin control design that employed Vietnam veterans discordant for combat exposure in Vietnam. Each structure's volume was significantly correlated between twins, indicating a partial familial determination: for anterior superior vermis, r=0.73; for posterior superior vermis, r=0.47; for inferior posterior vermis, r=0.51; and for total vermis, r=0.57. There were no significant differences between the PTSD and non-PTSD veterans for any vermis volume, and no significant main effects or interactions when their non-combat-exposed co-twins were added to the analyses. Thus, the results do not support the structural abnormality of cerebellar vermis in combat-related PTSD.

Cerebellum↗
PubMed1994

Magnetic resonance imaging: a new tool in the diagnosis of tumours of the nail apparatus.

Tumours of the nail apparatus are often the subject of diagnostic dilemma. Until now, no reliable imaging methods have been available to assess these lesions correctly. We report the results of high and very high-resolution magnetic resonance imaging (MRI), which have been correlated with the anatomical findings in 14 cases of nail apparatus pathology, and discuss the possible contribution of MRI to diagnosis. With very high-resolution MRI, accurate analysis of the anatomy of the nail apparatus is possible, and lesions as small as 1 mm can be detected. An expansive process can be excluded when results are negative. Glomus tumour, mucoid pseudocyst, fibrokeratoma, and exostosis can be differentiated because of their different MRI characteristics. This is of importance when the exact nature of a subungual tumour cannot be determined by clinical findings alone. Measurement, determination of the exact localization of the tumour, and the study of its relationship to the other structures, can provide guidance for subsequent surgical procedures. MRI is reliable and accurate in the delineation of lesions, and provides a new tool for the investigation of pathology of the nail apparatus.

Adolescent↗
PubMed2004

Cardiovascular regulation and hippocampal sclerosis.

PURPOSE: Cardiovascular dysregulation has been detected in patients with temporal lobe epilepsy (TLE) by using cardiovascular reflex tests and analysis of heart rate variability (HRV). The two methods have not previously been used in the same study to compare them in the assessment of cardioregulatory function. Magnetic resonance imaging (MRI) is considered the best method to reveal structural changes such as hippocampal sclerosis associated with TLE. It is not known whether these structural changes modify cardioregulatory function in patients with TLE. METHODS: Standard cardiovascular reflex tests and analysis of spectral and dynamic measures from 24-h electrocardiogram (ECG) recordings were performed for eight patients with and 31 patients without hippocampal sclerosis and for 72 control subjects. MRI also was performed in each patient to reveal hippocampal sclerosis. RESULTS: Various measures of cardiovascular reflexes and HRV were diminished in patients with TLE compared with the control subjects. No significant differences were found in the measures obtained from the cardiovascular reflex tests or analysis of HRV between those with and without hippocampal sclerosis, although a nonsignificant trend toward reduced values was seen among those with hippocampal sclerosis. The values of cardiovascular reflexes and spectral analysis of HRV correlated with each other. CONCLUSIONS: These results suggest that functional rather than structural changes related to TLE are involved mainly as a mechanism of altered cardioregulatory function. The cardiovascular reflex test and analysis of HRV both appear to be useful in studying cardioregulation in patients with TLE.

Adult↗
PubMed1984

[Magnetic resonance: imaging of the heart and mediastinum].

The anatomic structures of the heart and mediastinum can be demonstrated with MRI in three dimensions in their topographic order without contrast medium or heart catheterization. Furthermore, differentiation of the tracheobronchial system and the mediastinal lymph nodes can be discerned with MRI. MRI offers the advantages of reducing invasive diagnostic procedures, eliminating radiation hazards and avoiding the risks of contrast media. Only in the area of the structures adjacent to the diaphragm an improvement of the images by means of additional respiratory-gating is desirable. Concerning tumors in the mediastinum, MRI supplies essential information for the planning of therapy.

Adult↗
PubMed1996

Magnetic resonance imaging of dialysis-related amyloidosis of the shoulder and hip.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of MRI in identifying abnormalities of the periarticular structures in patients with symptoms of dialysis-related amyloid arthropathy. DESIGN AND PATIENTS: MR images of shoulders and hips in 5 dialysis patients with symptoms of amyloid arthropathy were compared to images of shoulders and hips in 4 asymptomatic dialysis patients, shoulders in 9 nondialysis patients, and hips in 12 nondialysis patients. These were evaluated for the presence of focal periarticular osseous lesions, tendinous and capsular thickening, and periarticular fluid. RESULTS: Increased thickness of the supraspinatus tendon was found in both symptomatic and asymptomatic patients. Capsular thickening at the hip was present in all symptomatic patients, and in 3 of 8 asymptomatic hips. Joint and bursal fluid was common in the symptomatic group, and was present in some asymptomatic individuals. Osseous lesions were detected in the absence of plain film findings, and demonstrated variable signal intensity. CONCLUSIONS: MRI is useful in detecting signs of dialysis-related amyloidosis. Findings of a milder degree in asymptomatic dialysis patients suggests that MRI may also be valuable in the early diagnosis of this syndrome.

Adult↗
PubMed1987

Quantification of cardiac function by conventional and cine magnetic resonance imaging.

Magnetic resonance imaging (MRI) has been effective for depicting cardiac anatomy and is already established as a technique for the evaluation of some structural abnormalities of the heart and pericardium. With recent advances, MRI can now be used to quantitate cardiac function. Multiphasic ECG-gated spin-echo imaging has been used to quantitate right and left ventricular volumes and ejection fraction, left ventricular mass, and regional myocardial wall thickening. The new technique of cine MRI acquires frames during the cardiac cycle with a time resolution corresponding to 20 msec up to approximately 40 frames for an average cardiac cycle. This technique uses narrow flip angle (30 degrees) and gradient refocused echoes. Cine MRI has been used to measure ventricular volumes and ejection fraction and regional myocardial wall thickening. It is also sensitive to the detection of valvular regurgitation and can provide quantitation of regurgitant volume. This article reviews the current status of MRI for quantitating cardiac function.

Heart↗
PubMedDate not supplied

Computed tomography vs. magnetic resonance imaging of acute bacterial sinusitis: a rabbit model.

PURPOSE: Computed topography (CT) and magnetic resonance imaging (MRI) are important, both clinically and in a research setting, in assessing bacterial sinusitis (BS). The use of CT scanning to evaluate sinus opacification in a reversible model of rabbit acute sinusitis has been reported. MRI offers the potential for better visualization of soft tissue and fluid changes within the paranasal sinuses. MRI has potential as a research tool in animal models of sinusitis. This article compares the use of CT and MRI in measuring maxillary sinus opacification in rabbits during experimental, reversible BS. MATERIALS AND METHODS: In 2 independent trials, New Zealand White rabbits were imaged for baseline anatomy, and BS was generated by sinus inoculation with Staphylococcus aureus. Serial imaging was performed as a measure of the progression and resolution of BS during the trials. Two experienced, independent reviewers then scored each CT and MRI for percent opacification of the maxillary sinus. These scores were analyzed to assess the degree of agreement between the reviewers. RESULTS: The correlation coefficients for CT and MRI were 0.6816 and 0.3584, respectively. The Z-statistic comparing these correlation coefficients was significant (P < .0001), indicating that CT is a more precise measure of reversible BS in this rabbit model. Differences in mean scan time and cost per scan were also significantly different (P < .0001), with CT being both quicker and less expensive. CONCLUSIONS: Greater interobserver consistency of scan interpretation, with less time and cost, make CT the preferred tool for measuring BS in this rabbit model. Attributes of MRI such as better resolution of fluid-tissue interfaces and custom surface coil design for visualization of specific anatomic structures are discussed as they may increase the effectiveness of MRI as an imaging modality in future sinusitis research.

Acute Disease↗
PubMed1990

[Nuclear magnetic resonance imaging in cardiology].

Magnetic resonance imaging (MRI) is particularly well suited to cardiovascular studies since the spontaneous contrast between circulating blood and the cardiac and vascular structures is excellent. The theoretical principles and technical modalities of MRI are summarized prior to describing its cardiovascular applications. Owing to the quality of its anatomical images MRI was first used in daily practice to complete or replace other imaging methods. Its applications are illustrated here. They include aortic pathology (aneurysm, dissection, postoperative control), complex congenital cardiac pathology, hypertrophic cardiomyopathy, heart tumours, post-infarction ventricular aneurysms, and pericardial pathology. The applications of MRI that are currently being evaluated or developed are described. Due to the recent acquisition of cinematographic images MRI is now capable of evaluating the cardiac function. As for the use of MRI to characterize the cardiac muscle, this is a highly original application which may soon become an interesting diagnostic tool.

Aortic Diseases↗
PubMed1991

Negative MRI findings in knee injury: clinical implications.

Magnetic resonance imaging (MRI) is now commonly used to diagnose knee pathology. Based on results in a study conducted in a private practice setting, the diagnostic value of MRI for all articular cartilage surfaces, menisci, ligaments, and soft tissue structures of the knee was determined. Subjects included 102 consecutive patients undergoing arthroscopic knee surgery for whom MRI findings also were available. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of MRI were calculated. Sensitivity was highest for meniscus tears: 73.2% for medial tears and 63.3% for lateral tears. Sensitivity for other pathologies was poor, ranging from 26.2% for chondromalacia of the patella to 11.1% for loose bodies. Negative predictive values were variable, ranging from 84.3% for lateral meniscus tears to 39.2% for chondromalacia of the patella. MRI for most pathologies had an NPV between 50 and 75%. Results indicate a high rate of false negative MRI findings.

Adolescent↗
PubMed2001

Dipole modeling of interictal and ictal EEG and MEG paroxysms.

Dipole modeling procedures can be used to statistically estimate the location and the orientation of intracerebral sources of electroencephalographic (EEG) and magnetoencephalographic (MEG) signals. These methods have been applied to interictal spikes for more than 20 years and suggest that interictal paroxysms might be generated by a network of cortical structures rather than by a focal area. In this review we address the questions of (1) the spatial extend of this network in different types of epilepsies, (2) the spatial relationship between this network and other structural of functional abnormalities as assessed by Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET), and (3) the reliability of dipole sources of interictal and ictal paroxysms. Dipole modeling results suggest that, in temporal lobe epilepsies, both neocortical and mesio-temporal structures are involved during interictal spikes; frontal lobe epilepsies are often characterized by more complex source distributions, that, in general, involve a large area and bilateral frontal structures. In addition, dipole modeling results are also found in close agreement with MRI data in cases where focal dysplasia or heterotopia are diagnosed. Nevertheless, in most other cases, sources of interictal spikes and MRI lesions, though overlapping in space, are not totally congruent. The best concordance between sources of interictal spikes and glucose hypometabolism on PET data is usually found for temporal lobe epilepsies. Most often, intracranial and intracerebral recordings validate both the localization and the time activation of interictal spike dipoles. However, results obtained for ictal discharges are less reliable, which therefore addresses the usefulness of dipole modeling procedures in assessing sources of ictal discharges. In conclusion, dipole modeling results can rarely be used in planning a selective surgery without invasive recordings. However, the studies reviewed in this paper strongly suggest that their analysis, in combination with other non-invasive data, might be useful to better delineate the epileptogenic zone, and help the implantation of intracerebral electrodes.

Journal Article↗
PubMedDate not supplied

MRI of the intracerebral lesions at 0.5 Tesla: comparison of fast spin-echo and conventional spin-echo sequences.

Fast spin-echo sequences was compared with conventional spin-echo sequences at 0.5 Tesla, in 130 patients who attended for routine brain MRI. Artefacts and contrast behaviour of anatomical structures and lesions were assessed visually and quantitatively by contrast-to-noise ratios. The difference between conventional spin-echo and fast spin-echo in contrast in intracerebral tumors and infarcts was not found to be significant statistically. Small amounts of haemosiderin and calcifications could not be seen on fast spin-echo images especially in T2 weighted. Flow artefacts were considerably reduced on fast spin-echo images. Motion artefact was considerably increased on dual-echo fast spin-echo sequences. There were no statistical differences between the results of the visual findings and between those of CNR values except for contrast between CSF and white matter and between haemoatoma and background in T2 sequences. Our results suggest that by virtue of the shorter acquisition time, diagnostic reliability and reduced flow artefact single-echo FSE sequences should be preferred to dual-echo CSE sequences in routine brain MRI at 0.5 Tesla.

Brain Diseases↗
PubMed2000

Displacement imaging of spinal cord using q-space diffusion-weighted MRI.

Displacement MR images of water in in vitro rat spinal cord were computed from q-space analysis of high b value diffusion-weighted MRI data. It is demonstrated that q-space analysis of heavily diffusion-weighted MRI (qs-DWI) provides MR images in which physical parameters of the tissues such as the mean displacement and the probability for zero displacement of the water molecules are used as contrasts. It is shown that these MR images provide structural information surpassing the spatial resolution of conventional MRI by several orders of magnitude. This imaging methodology was used to follow spinal cord maturation in the rat. It was found that changes in the diffusion characteristics of white matter upon maturation are responsible for the emergence of gray/white matter contrast. The mean displacement of water molecules in the white and gray matter of the mature rat spinal cord was found to be 2-3, and 8-10 microns, respectively. The potential and the limitations of this new imaging methodology for early detection of white matter disorders are discussed.

Animals↗