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PubMed2001

Non-conventional MR techniques to monitor the evolution of multiple sclerosis.

In multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) has proved to be sensitive for detecting lesions and their changes over time. However, conventional MRI cannot characterize and quantify the tissue damage within and outside such lesions. Other quantitative MR techniques, including MR spectroscopy (MRS), magnetization transfer imaging (MTI) and diffusion-weighted imaging (DWI) have the potential to overcome this limitation and, as a consequence, to provide complementary information to conventional MRI. MTI- and DWI-derived measurements quantify the structural changes occurring within and outside lesions seen on conventional MRI scans, and MRS adds information on the biochemical nature of such changes. The application of these MR techniques to the study of MS is dramatically increasing our understanding of how MS causes irreversible deficits, and it is likely to provide useful insights into the pathophysiology of other white matter diseases in the future. The present review summarizes the major contributions made by these three MR techniques in the understanding of MS evolution.

Central Nervous System↗
PubMed1999

A descriptive survey of long-term residents with epilepsy and intellectual disability at the Chalfont Centre: is there a relationship between maladaptive behaviour and magnetic resonance imaging findings?

The advent of high-resolution magnetic resonance imaging (MRI) has facilitated the identification of subtle, aetiologically relevant structural brain abnormalities in a significant proportion of patients with epilepsy and negative standard neuro-imaging. In the present study of people with intellectual disability (ID), the authors show that a high frequency of cerebral structural abnormalities (72.4%) can be demonstrated by high-resolution MRI in patients with epilepsy and ID. Malformations of cortical development (MCD) were found in 8.7% of people without profound ID. An earlier age of onset of habitual seizures was associated with more severe ID and more severe seizures in adulthood. There was no obvious association between this finding and maladaptive behaviour, but a past history of febrile convulsions was associated with increased irritability and agitation. Since there was no obvious association between a history of febrile convulsions and MRI abnormalities, the reason for the above finding remains unclear. Inevitably, any residential epilepsy centre population is subject to selection biases. The population studied was highly skewed, with only one-third of the sample being female and 80% having mild ID. Thus, the findings of the present study cannot necessarily be generalized to all people with ID.

Adolescent↗
PubMed1993

Investigating the pediatric central nervous system.

Imaging investigation of the pediatric central nervous system may be considered in terms of structural imaging and functional imaging. Established structural imaging modalities include ultrasonography, radiography, computed tomography, magnetic resonance imaging (MRI), cerebrospinal fluid imaging (eg, myelography), and angiography. Functional imaging technologies include single photon emission computed tomography (SPECT), positron emission tomography, magnetic resonance spectroscopy, and magnetic resonance perfusion imaging. Furthermore, more recent advances in computer software now allow the superimposed display of separate imaging modalities using image fusion techniques. This technique allows the superimposition of structural imaging data with functional imaging data, eg, SPECT and MRI, or the fusion of structural imaging modalities, eg, computed tomography and MRI. In this respect, current practical and investigative applications of structural and functional imaging of the pediatric central nervous system are reviewed.

Central Nervous System↗
PubMed1995

Neurological Wilson's disease studied with magnetic resonance imaging and with positron emission tomography using dopaminergic markers.

Four patients with neurological Wilson's disease were investigated using magnetic resonance imaging (MRI) and positron emission tomography (PET). All patients had dystonia as their major clinical manifestation but also had dysarthria and at the presentation of the disease had choreoathetoid movements in at least one limb. A multitracer approach with PET was used to visualize various aspects of dopaminergic function; [11C]-(+)-nomifensine (NMF), [11C]raclopride (RAC) and [11C]-L-DOPA (one patient). Correlation analysis of RAC and NMF binding as well as putamen/caudate uptake ratios showed corresponding reductions. The patient investigated with [11C]-L-DOPA had a normal striatal uptake. Generally, structural changes as shown by MRI corresponded to reductions both in NMF and RAC binding. There was no evident correspondence between PET findings and the severity of clinical symptoms seen in the individual patient. In two patients with discrete neurological impairment at the time of investigation, PET showed serious presynaptic dopaminergic lesions in the putamen. Our data suggest that the striatal degeneration seen in Wilson's disease comprises a complex pathology involving both afferent and efferent projections. The discrete neurological impairment seen in some patients with gross striatal pathology might be due to concomitant lesions in functionally counteracting basal ganglia circuits.

Adult↗
PubMed1999

Reduced cerebral blood flow and impaired visual-spatial function in proximal myotonic myopathy.

OBJECTIVE: To compare brain involvement in myotonic dystrophy (DM) with that of proximal myotonic myopathy (PROMM). BACKGROUND: PROMM is a multisystem disease with many features in common with DM. METHODS: Twenty patients with DM (CTGF[500-700), 20 patients with PROMM, and 20 normal control subjects were studied. Neuropsychological testing was performed in 12 patients with PROMM and in 18 patients with DM; brain MRI was performed in 17 of 20 PROMM patients and 15 of 20 DM patients. Ten patients with PROMM and 11 patients with DM were subjected to H2(15)O PET. RESULTS: Two-thirds of the patients with PROMM and one-half of those with DM were impaired on visual-spatial recall, whereas one-third of the patients with PROMM and less than half of those with DM showed an impairment in visual-spatial construction. Brain MRI was normal, or showed only nonspecific white matter abnormalities in both PROMM and DM patients. PET studies in PROMM patients showed a bilateral decrease in regional cerebral blood flow (rCBF) of the orbitofrontal and medial frontal cortex, whereas DM patients had more widespread hypoperfusion that extended to the dorsolateral frontal cortex and subcortical regions. CONCLUSIONS: Impaired visual-spatial function may be present in proximal myotonic myopathy. This correlates best with a reduction in regional cerebral blood flow observed in H2(15)O PET brain scans rather than with specific structural abnormalities observed on brain MRI.

Adolescent↗
PubMed1996

Functional magnetic resonance imaging in a stereotactic setup.

The localization of critical structures within the brain is important for the planning of therapeutic strategies. Functional MRI is capable to assess functional response of cortical structures to certain stimuli. The authors present two techniques for functional MRI (fMRI) in a stereotactic set-up. The skull of the patients has been immobilized for stereotactic treatment planning either with a self developed stereotactic ceramic frame and bony fixation or with an individual precision mask system made of light cast. It has been shown that this frame does not produce any image distortion. fMRI was performed using a modified FLASH sequence on a conventional 1.5 T MRI scanner with a specially developed linear polarized head coil. The imaging technique used was an optimized conventional 2D and 3D, first order flow rephased, gradient echo sequence (FLASH) with fat-suppression and reduce bandwidth (16-28 Hz/pixel) and TR = 80-120 ms, TE = 60 ms, flip angle = 40 degrees, matrix = 128 x 128, FOV = 150-250 mm, slice-thickness = 2-5 mm, NEX = 1, and a total single scan time for one image of about 7 sec. The motor cortex stimulation was achieved by touching each finger to thumb in a sequential, self-paced, and repetitive manner. Statistical parametric maps based on student's test were calculated. Pixels with a highly significant signal increase (p < 0.001) are overlaid on T1w SE images. The primary motor and sensory cortex could be visualized with this method in all 10 patients that were imaged in this study. Due to tight fixation of the patient's skull there have been no motion artifacts. These results show that functional MRI is feasible in an stereotactic set-up with an standard 1.5 T scanner. This is a prerequisite for the exact pre therapeutic assessment of the function of cortical centers.

Brain↗
PubMed2005

Imaging of parasellar lesions.

UNLABELLED: The sellar and parasellar region is an anatomically complex area that represents a crucial crossroad of important adjacent structures, e.g. orbits, cavernous sinus and its content, polygon of Willis, hypothalamus through the pituitary stalk and dural reflections forming the diaphragm sellae and the walls of the cavernous sinuses. Although the cavernous sinus represents the most relevant parasellar structure, from the practical and clinical point of view all the structures that surround the sella turcica can be included in the parasellar region. CT and, mainly, MRI are the imaging modalities to study and characterise the normal anatomy and the majority of processes in this region. We present a practical short review of the most relevant CT and MRI characteristics, such as location, nature of contrast enhancement and presence of cystic components, together with clinical findings, which permit differentiation of the most frequent and less common lesions found in the parasellar region. LEARNING OBJECTIVES: -A short review of the anatomy and clinical symptoms related to the parasellar region. -Radiological characterisation, mainly by MRI, of the many lesions that alter the structure and function of sellar and parasellar anatomy. -Description of the MRI features that permit differentiation among less common lesions.

Humans↗
PubMed1994

New techniques in magnetic resonance and epilepsy.

Developments in magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and single photon emission tomography (SPECT) have opened new opportunities for noninvasive brain investigation. Functional imaging methods involving noninvasive MRI and minimally invasive PET and SPECT are available that allow investigation of brain abnormality in intractable epilepsy patients. Noninvasive techniques enable the investigation of many aspects of the underlying neuropathologic basis of intractable seizures and of the relationship of functional abnormalities both to structural abnormalities and to the seizure focus. New MRI techniques demonstrate the structure of the brain in fine detail (especially the hippocampus), provide information about the underlying metabolism of brain regions, and demonstrate functional activity of the brain with high spatial and temporal resolution. The clinical impact of this noninvasive information cannot be overstated and these techniques provide indispensable information to neurologists specializing in epileptology. The proper use and interpretation of the findings provided by these new technologies will be a major challenge to epilepsy programs in the next few years.

Adult↗
PubMed1997

The ProHance story: the making of a novel MRI contrast agent.

The four gadolinium chelates currently in clinical use as magnetic resonance imaging (MRI) contrast agents differ in two structural features: linear vs. macrocyclic cores, and ionic vs. nonionic charge types. While all are equivalent in relaxation effectiveness, the nonionic molecules have lower osmolality and viscosity and may be formulated safely at greater concentrations, and delivered confidently at greater doses and as a faster bolus. The macrocyclic molecules are more stable and show less tendency to dissociate free Gd. ProHance was conceived well over a decade ago, based upon a unique structure. It was first marketed in the USA in 1992, and was the first nonionic agent. It remains today still the only commercial MRI agent that is both macrocyclic and nonionic. To date it has been used safely in over a million patients.

Animals↗
PubMed2001

[MRI in the preoperative diagnosis of chronic sinusitis: comparison with CT].

PURPOSE: To determine the value of MRI in the preoperative evaluation of chronic paranasal sinusitis and to compare the results with CT and intraoperative findings. METHOD/MATERIALS: 42 patients with clinical signs of chronic paranasal sinusitis underwent MRI after CT evaluation on one day, with subsequent functional endoscopic sinus surgery on the next day. Coronary CT was obtained with 5-mm slices and table-feed in the prone position, while MRI was performed in the supine position with coronary T2-TSE + pd and coronary and transverse HASTE, each with 5-mm slice thickness. Aquisition time in MRI was less than 8 minutes. Two radiologists reviewed the CT and MRI scans for signs of sinusitis and detection of anatomical landmarks. The results were correlated with the intraoperative findings. RESULTS: MRI offered no artifacts of dental work and showed more often high quality pictures than CT. CT and MRI demonstrated a good correlation in the detection of mucosal pathologies (kappa = 0.46-0.87) and anatomic variants (kappa = 0.55-0.86). All important anatomical structures could be evaluated sufficiently with MRI for preoperative management. Both diagnostic tools showed an unsatisfactory correlation with intraoperative findings in the ethmoidal complex and maxillary sinus (tau = -0.08-0.3). CONCLUSIONS: MRI is a fast and reliable alternative to preoperative CT in examining paranasal sinuses and offers a good visualization of mucosal changes. CT and MRI both give an unreliable representation of the ethmoidal complex.

Artifacts↗
PubMed2003

GdIII complexes with fast water exchange and high thermodynamic stability: potential building blocks for high-relaxivity MRI contrast agents.

On the basis of structural considerations in the inner sphere of nine-coordinate, monohydrated Gd(III) poly(aminocarboxylate) complexes, we succeeded in accelerating the water exchange by inducing steric compression around the water binding site. We modified the common DTPA(5-) ligand (DTPA=(diethylenetriamine-N,N,N',N",N"-pentaacetic acid) by replacing one (EPTPA(5-)) or two (DPTPA(5-)) ethylene bridges of the backbone by propylene bridges, or one coordinating acetate by a propionate arm (DTTA-prop(5-)). The ligand EPTPA(5-) was additionally functionalized with a nitrobenzyl linker group (EPTPA-bz-NO(2) (5-)) to allow for coupling of the chelate to macromolecules. The water exchange rate, determined from a combined variable-temperature (17)O NMR and EPR study, is two orders of magnitude higher on [Gd(eptpa-bz-NO(2))(H(2)O)](2-) and [Gd(eptpa)(H(2)O)](2-) than on [Gd(dtpa)(H(2)O)](2-) (k(ex)298=150x10(6), 330x10(6), and 3.3x10(6) s(-1), respectively). This is optimal for attaining maximum proton relaxivities for Gd(III)-based, macrocyclic MRI contrast agents. The activation volume of the water exchange, measured by variable-pressure (17)O NMR spectroscopy, evidences a dissociative interchange mechanism for [Gd(eptpa)(H(2)O)](2-) (DeltaV(not equal sign)=(+6.6+/-1.0) cm(3) mol(-1)). In contrast to [Gd(eptpa)(H(2)O)](2-), an interchange mechanism is proved for the macrocyclic [Gd(trita)(H(2)O)](-) (DeltaV (not equal sign)=(-1.5+/-1.0) cm(3) mol(-1)), which has one more CH(2) group in the macrocycle than the commercial MRI contrast agent [Gd(dota)(H(2)O)](-), and for which the elongation of the amine backbone also resulted in a remarkably fast water exchange. When one acetate of DTPA(5-) is substituted by a propionate, the water exchange rate on the Gd(III) complex increases by a factor of 10 (k(ex)298=31x10(6) s(-1)). The [Gd(dptpa)](2-) chelate has no inner-sphere water molecule. The protonation constants of the EPTPA-bz-NO(2) (5-) and DPTPA(5-) ligands and the stability constants of their complexes with Gd(III), Zn(II), Cu(II) and Ca(II) were determined by pH potentiometry. Although the thermodynamic stability of [Gd(eptpa-bz-NO(2))(H(2)O)](2-) is reduced to a slight extent in comparison with [Gd(dtpa)(H(2)O)](2-), it is stable enough to be used in medical diagnostics as an MRI contrast agent. Therefore both this chelate and [Gd(trita)(H(2)O)](-) are potential building blocks for the development of high-relaxivity macromolecular agents.

Chelating Agents↗
PubMed2001

[Diagnosis of intra-articular fracture of the head of the tibia. A prospective comparative study].

Complete visualization of the joint surface is essential for correct assessment of tibial head fractures. Conventional tomography, computed tomography (CT), and magnetic resonance imaging (MRI) are compared in this prospective study. We examined 27 patients (19 suffering from B fractures and 8 from C fractures) from 1 January 1995 to 11 November 1998. Conventional tomography underestimated the fractures in 3 of the 19 cases of B fractures. Computed tomography underestimated two of these cases. MRI could not exactly depict the essential structures in three of the eight cases of C fractures because of edema and effusions. MRI identified complete cruciate ligament rupture in 6 of the 27 cases (18%) and 10 meniscal ruptures in 9 cases (33%: 6 medial meniscus, 4 lateral meniscus). Complete ruptures of the lateral collateral ligament were detected in five cases and medial collateral ligament ruptures in two cases. According to this, 63% of the patients suffered from relevant accompanying soft tissue injuries. The rate of soft tissue injuries increased up to 92% including the partial collateral ligament ruptures. Local hospital conditions permitting, X-ray-loaded conventional tomography should no longer be used in tibial head fractures. X-ray-free MRI is most efficient in cases of B fractures, which can in most cases be treated with a minimum of invasive techniques. Computed tomography is to be used in cases of C fractures that are regularly managed by open surgery accompanied by direct visualization of the inside of the knee joint.

Adult↗
PubMed1992

Identification of the epileptic focus: magnetic resonance imaging.

Magnetic resonance imaging (MRI) is the most sensitive and specific structural imaging technique available to demonstrate focal epileptogenic lesions in patients with intractable partial epilepsy. MRI may be useful in the selection of candidates for surgical treatment of epilepsy. The studies may also assist in the implantation of depth electrodes and in the stereotactic resection of epileptogenic lesions. More recent applications of this neuroimaging modality in the surgical treatment of epilepsy include pre-operative hippocampal formation of volume measurements and postoperative quantitative determinations of cortical resections.

Brain↗
PubMed1992

[Dissection of the sub-astragalar ligaments and magnetic resonance imaging].

The aim of this study is to find the different ligamentous structures in the subtalar region through dissection and to compare them with images obtained on MRI. MRI allows visualization of the different ligamentous structures with greater precision than with computerized tomography. This investigation should permit a more precise diagnosis of injuries often poorly understood in this region.

Humans↗
PubMed2004

[Virtual colonography in CT and MRI examinations].

The paper presents new ways of visualizing internal structures of the large intestine. Use of spiral computed tomography (CT) or magnetic resonance imaging (MRI) combined with appropriate software leads to imaging that can be compared with colonoscopy or double contrast enema. The authors discuss patients' preparation, methods for CT and MRI variants, indications, advantages and costs.

Colonic Neoplasms↗
PubMed2001

Magnetic resonance imaging in rheumatoid arthritis: current status and future directions.

The performance of alternative imaging endpoints in clinical trials can be compared in terms of validity, rate of change, measurement precision, and convenience and cost. With respect to technical performance, magnetic resonance imaging (MRI) appears to show greater sensitivity than radiography for detecting bone abnormalities in rheumatoid arthritis (RA). In addition to monitoring changes in the bones, cartilage, and synovium, MRI can directly visualize the full spectrum of tendon pathology, and has been shown to identify tendonitis and tendon rupture with greater accuracy than clinical examination. MRI is currently regarded to be the most sensitive imaging technique for identifying trauma, infection, ischemia, and primary and secondary neoplasia of bone. Several studies have also shown MRI to be highly sensitive for detecting what appear to be bone erosions in the hands and wrists of patients with RA. MRI shows remarkable promise as a tool for identifying and monitoring structural damage in the joints of patients with RA. MRI appears to be able to identify bone erosions with greater sensitivity than radiography, and to disclose edema-like changes in the marrow, which may precede actual erosion formation. As new therapies with structure modifying capabilities enter the clinic, the ability to identify patients appropriate for those therapies and then to monitor the effectiveness and safety of treatment become increasingly important.

Arthritis, Rheumatoid↗
PubMed1997

Magnetic resonance imaging of anal sphincters after reconstruction of high or intermediate anorectal anomalies with posterior sagittal anorectoplasty and fistula-preserving technique.

BACKGROUND/PURPOSE: Internal anal sphincter (IAS) function can be expected in approximately 75% of cases of high or intermediate anorectal anomaly reconstruction if the fistula region is preserved and transposed to become the new anal canal. METHODS: To investigate the morphology of the IAS structure, magnetic resonance (MR) imaging was performed postoperatively in 14 patients operated on with posterior sagittal anorectoplasty (PSARP) and fistula-preserving technique. The results were compared with the appearance of the anal canal in seven normal children. In addition, comparison was made with the images of five patients operated on with earlier pull-through techniques, in which the fistula region was resected. RESULTS: In all patients operated on with PSARP and fistula-preserving technique, the MRI displayed an IAS-like smooth muscle structure encircling a closed anal canal. In comparison with normal controls, the image of this IAS was more irregular and had greater variations in thickness in different directions. Moreover, the area of the IAS structure was larger in comparison with the controls. Eleven of the 14 patients showed a positive rectoanal inhibition reflex in rectoanal manometry. However, the MR findings of the three cases lacking the reflex were not different compared with the rest of the group. The five patients operated on with earlier techniques demonstrated an open anal canal without a measurable IAS smooth muscle component. CONCLUSIONS: An IAS smooth muscle structure was seen by MRI in all patients operated on with PSARP and fistula-preserving technique independently of the severity of the malformation and the postoperative physiological IAS function. However, this structure was in most cases more voluminous and irregular compared with normal controls.

Adolescent↗
PubMed2004

Femoral neck trabecular microstructure in ovariectomized ewes treated with calcitonin: MRI microscopic evaluation.

UNLABELLED: Ovariectomy induces deterioration of the trabecular structure in the femoral neck of ewes, as depicted by MR microscopic imaging. This structural deterioration is prevented by salmon calcitonin treatment. INTRODUCTION: This study evaluated the trabecular (Tb) microarchitecture of an ovariectomy (OVX)-induced osteoporotic model in ewes and determined the effects of salmon calcitonin (sCT), an osteoclast inhibitor, on the Tb structure. This is the first report of OVX-induced changes in the Tb structure in the femoral neck in the ewes and effect of sCT on the microarchitecture. MATERIALS AND METHODS: Ewes (5-8 years old, n = 28) were equally allocated into sham (Sham), OVX injected with vehicle, or OVX injected with sCT at 50 or 100 IU, three injections per week. They were killed 6 months after OVX. The femoral neck was examined with an MR imager at 9.4 T in axial, coronal, and sagittal planes. An internal calibration procedure as a means of standardizing image analysis was used to adjust the segmentation threshold. Data from all three planes were averaged. RESULTS AND CONCLUSIONS: Compared with Sham, OVX induced significant changes (p < 0.0125) in the MRI-derived femoral neck Tb structure: Tb bone volume fraction (BV/TV), -18%; Tb number, -20%; Tb separation, +23%; number of free ends, +28%; number of nodes, -39%; number of Tb branches, -23%; mean length of Tb branches, -19%. Compared with OVX, treatment of sCT at 100 IU significantly improved all the Tb structural parameters to the Sham level (p < 0.0001 approximately p = 0.0281), whereas 50 IU significantly increased the Tb number and the mean length of the Tb branches. BV/TV explained 74% of the variation of compressive stress of the trabecular cylinder cores of the femoral neck. Combining all structural parameters in a multivariate regression analysis significantly improved the explanation to 84%, and adding BMD further improved the predictive ability of the model to 92%. We conclude that OVX induces deterioration of the MRI-derived Tb microstructure in the femoral neck of ewes. sCT treatment prevents OVX-induced changes. The femoral neck microarchitecture significantly correlates with its biomechanical properties. Combining microstructural parameters with BMD further improves the prediction of bone biomechanical properties. The effects of sCT on OVX ewes may help explain reduced fracture risk in postmenopausal osteoporotic women treated with sCT.

Animals↗