Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Structural MRI”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed2002

An in vitro study to evaluate the accuracy of stereotactic localization using magnetic resonance imaging by means of the Leksell stereotactic system.

The advantages of using magnetic resonance imaging (MRI) as opposed to computed tomographic (CT) scans or ventriculography in stereotactic surgery include the increased tissue contrast of the lesion or target, direct non-reformatted multiplanar imaging and target coordinate determination as well as reduced imaging artefacts produced by the stereotactic frame. One disadvantage of MR stereotaxis, however, is the potential for anatomic inaccuracy due to equipment-induced inhomogeneities of the magnetic field. The authors present an experimental study on an in vitro model to examine the accuracy of target localization using the Leksell stereotactic frame and MR imaging. Ten formalin-fixed brains taken from patients who had died of non-neurological diseases were sealed in a properly modelled plaster-cast shell simulating the skull bone. These models were fixed in the Leksell stereotactic frame and high-field MR images were performed (Siemens Magnetom SP 1.5 Tesla, T1-weighted spin echo sequences, TR/TE 600/15 ms, slice thickness 2 mm, FOV 300 mm). Following electrocoagulation of different targets on both lentiforme nuclei, the localization and extension of the lesions were controlled by MRI. A gross-/histopathological verification was performed. This model allows a good representation of the anatomic structures without any artefacts. The postoperative MRI control and the pathological examination of the lesions matched well with the preoperatively defined targets. The correlation of coordinates and measurements obtained with the pathological studies were within a +/- 2 mm range in all cases.

Brain↗
PubMed1994

Right ventricular outflow tract ventricular tachycardia: detection of previously unrecognized anatomic abnormalities using cine magnetic resonance imaging.

OBJECTIVES: This study attempted to determine whether cine magnetic resonance imaging (MRI), because of its unique ability to image the right ventricle, detects abnormalities in patients with right ventricular outflow tract ventricular tachycardia. BACKGROUND: Right ventricular outflow tract ventricular tachycardia occurs in the absence of apparent structural heart disease. METHODS: We compared cine MRI scans in 22 patients with right ventricular outflow tract ventricular tachycardia, 16 subjects without structural heart disease and 44 patients with other cardiovascular diseases. Echocardiography was performed in 21 patients with ventricular tachycardia. RESULTS: All 22 patients with ventricular tachycardia had normal left ventricular function and no evidence of coronary artery disease. Cine MRI revealed right ventricular structural and wall motion abnormalities more often in patients with ventricular tachycardia (21 [95%] of 22) than in normal subjects (2 [12.5%] of 16, p < 0.0001) or patients without arrhythmia (17 [39%] of 44, p < 0.0001). The abnormalities in patients with ventricular tachycardia (fixed focal wall thinning, excavation, decreased systolic thickening) were located in the right ventricular outflow tract, whereas those in patients without arrhythmia were confined to the free wall. Cine MRI demonstrated abnormalities in patients with ventricular tachycardia more often than did echocardiography (21 [95%] of 22 vs. 2 [9%] of 21, respectively, p < 0.0001). CONCLUSIONS: Right ventricular outflow tract ventricular tachycardia was associated with focal structural and wall motion abnormalities of the right ventricular outflow tract that were detected more often by cine MRI than by other imaging modalities and were not present in patients without arrhythmia or in normal subjects.

Adult↗
PubMed1992

Evaluation of atrial, ventricular and atrioventricular septal defects by cine magnetic resonance imaging.

Cine magnetic resonance imaging (MRI) was performed on 20 patients (mean age: 5.3 +/- 4.4 years) with atrial, ventricular, or atrioventricular septal defects for evaluation of cardiac structure and blood flow. Prior to cine MRI, electrocardiographically gated MRI using multislice acquisition was performed on all patients to localize optimal slice location. Cine-MRI was obtained with a 30 degrees flip angle, 15 msec echo time, and 30 msec pulse repetition time, on a 256 x 256 or 128 x 128 acquisition matrix. Abnormalities of cardiac structure were well defined in all patients by gated cardiac imaging. In 18 of the 20 patients, cine-MRI was able to detect shunt flow, visualized as a low intensity signal in comparison with the surrounding blood flow. Cine-MRI can provide not only accurate anatomy of cardiac structures but functional assessment of the cardiac chamber, wall topology and flow relations. Cine-MRI will become an important noninvasive technique for assessment of anatomy and physiology in congenital heart disease.

Abnormalities, Multiple↗
PubMed2000

MRI of the spine and spinal cord: imaging techniques, normal anatomy, artifacts, and pitfalls.

BACKGROUND: Magnetic resonance imaging (MRI) is widely used to evaluate the spine and spinal cord. OBJECTIVE: In this article, MRI of the spine is discussed in terms of normal anatomy, standard and advanced imaging techniques, general indications, limitations, and potential for the future. DISCUSSION: Although MRI does not provide the high bony detail possible with computed tomography, the appropriate combination of the sequences takes advantage of the different tissue characteristics to discriminate the various bony-and soft-tissue structures of the spine. CONCLUSION: MRI enables the imaging specialist to evaluate a large anatomic region in multiple planes and can better examine the spinal cord.

Artifacts↗
PubMed1998

Arterial territories of the human brain: cerebral hemispheres.

The development of neuroimaging has allowed clinicians to improve clinicoanatomic correlations in patients with stroke. Anatomic structures are well delineated on MRI, but there is a lack of standardization in their arterial supply. As in our previous study depicting the arterial supply of the brainstem and cerebellum, we present a system of 12 axial sections of the hemispheres depicting the dominant arterial territories, the most important anatomic structures, and Brodmann's areas. The area of variation of the cortical territory of the anterior, middle, and posterior cerebral arteries is also represented. These sections may be used as a practical tool to determine arterial territories on CT or MRI, and may help establish consistent clinicoanatomic correlations in patients with supratentorial stroke.

Anatomy, Artistic↗
PubMed2001

Working memory deficits in schizophrenia are not necessarily specific or associated with MRI-based estimates of area 46 volumes.

Despite substantial evidence that the prefrontal cortex does not function normally in patients diagnosed with schizophrenia, evidence for prefrontal structural abnormalities, as measured by magnetic resonance imaging (MRI), has been inconsistent. Additionally, evidence for relationships between prefrontal structural and functional measures has been limited. The inconsistencies in the MRI literature are, at least in part, due to a lack of standard and specific measurement protocols that allow delineation of functionally distinct cortical regions. In this study, reliable methods for measuring an estimate of area 46 (estimate referred to as area 46(e)), as defined by 'Cereb. Cortex 5 (1995) 323', were developed and used to examine relationships between area 46(e) volumes, working memory, and symptom severity in 23 male patients and 23 healthy male comparison subjects. Patients performed more poorly than healthy reference subjects on all cognitive measures including measures of spatial and non-spatial working memory, but showed no significant corresponding deficits in area 46(e) volumes or whole brain volumes. Moreover, there were no significant relationships between symptom severity and area 46(e) volumes. These findings suggest that the prefrontal functional abnormalities observed in schizophrenia may occur in the absence of prefrontal volume deficits, and may instead involve more widespread brain systems or prefrontal connections with other brain regions.

Adult↗
PubMed2002

High-resolution MRI vs multislice spiral CT: which technique depicts the trabecular bone structure best?

The purpose of this study was to compare trabecular bone structure parameters obtained from high-resolution magnetic resonance (HRMR) and multislice computed tomography (MSCT) images with those determined in contact radiographs from corresponding specimen sections. High-resolution MR and MSCT images were obtained in 39 distal radius specimens. For HRMR the in-plane spatial resolution was 0.152x0.153 mm(2) with a slice thickness of 0.9 and 0.3 mm using a 3D T1-weighted spin-echo sequence. For MSCT the resolution was 0.247x0.247 mm(2) with a collimation of 1 mm. Using a diamond saw, 117 0.9- to 1-mm-thick sections were obtained from these specimens and contact radiographs were acquired. In the corresponding sections structure parameters analogous to bone histomorphometry were determined. Significant correlations between MR- and CT-derived structure parameters and those derived from the contact radiographs were found (p<0.01); r values of up to 0.75 were obtained for HRMR imaging and up to 0.70 for MSCT. On the average, structure parameters showed higher correlations for the MR- than for the CT-derived data. For the MR data the threshold algorithm used for binarizing the images substantially affected these correlations. In conclusion, trabecular bone structure parameters assessed in distal radius HRMR and MSCT images are significantly correlated with those determined in corresponding specimen sections (p<0.01). High-resolution MR-derived structure parameters, however, performed better in the prediction of trabecular bone structure.

Aged↗
PubMed1998

[Dental magnetic resonance tomography (dental MRI) as a method for imaging maxillo-mandibular tooth retention structures].

PURPOSE: To establish a new method for dental imaging using magnetic resonance tomography named Dental-MRT and to demonstrate its usefulness in diagnosing dentogen pathologies of the mandible and maxilla. METHODS: Seven healthy volunteers, three patients with pulpitis, two patients with dentigerous cysts, two patients after tooth transplantation, and three patients with atrophic mandibles have been evaluated. Optimized axial T1- and T2-weighted gradient echo and spin echo sequences in 2D and 3D technique have been established to perform studies of the jaws. The acquired images were reconstructed with a standard dental software package on a work-station as panorama and cross-sectional views of the mandible or maxilla. RESULTS: The entire maxillo-mandibular bone, teeth, dental pulp, and the content of the mandibular canal were well depicted. Patients with pulpitis demonstrate bone marrow edema in the periapical region. Dentigerous cysts and their relation to the surrounding structures are clearly shown. After contrast media administration marked enhancement of the dental pulp can be demonstrated. CONCLUSION: Dental-MRT promises to provide a new tool for visualization and detection of dental diseases.

Adolescent↗
PubMed2002

[Related structures of the lateral sphenoid wall anatomy studies in CT and MRI].

OBJECTIVE: To study the anatomy of the Lateral Sphenoid Wall in CT and MRI in normal adults so as to provide a theoretical basis for imagine science. METHOD: High resolution CT in axial and coronal planes was conducted on 25 normal adults. MRI in axial and coronal planes, using SE T1 WI and FSE T2 WI was conducted on 20 volunteers. RESULT: 1. The pneumatisation of sphenoid sinus can be divided into two types: Pneumatisation of the sphenoid body and the one of sphenoid process. The former one can be subdivided into three categories: concha (2%), pre sellar (20%), sellar (78%). The latter can be subdivided into four categories: lesser wing (38%), greater wing (40%), pterygoid process (34%) and dorsum sellar (6%). 2. The thinnest part (< 1 mm) of the LSW is located at the inner wall of the optic nerve canal (96%), at the bony wall in the plane of sphenoethmoid recess (86%), the bony wall in the plane of the internal carotid artery (66%). 3. Over pneumatised sphenoid sinus could make the foramen rotumdum (64%) and pterygoid canal (44%) protrudes into the sphenoid cavity. CONCLUSION: Attention should be paid to the various mode of pneumatization around the optic nerve canal.

Adolescent↗
PubMed2002

Diazepam-enhanced beta activity in Sturge Weber syndrome: its diagnostic significance in comparison with MRI.

OBJECTIVES: This study was performed to assess the extent of functional involvement of the affected hemisphere in Sturge Weber syndrome in comparison with the uninvolved hemisphere. To this end beta activity in the electroencephalogram (EEG) was measured, both before and after administration of diazepam intravenously (i.v.). METHODS: In 9 patients asymmetry in beta band activity was studied before and after diazepam administration. Several beta bands and asymmetry parameters were calculated. beta band asymmetries were compared with structural abnormalities (magnetic resonance imaging, MRI). RESULTS: Total beta activity was reduced in the involved hemisphere in all patients after diazepam administration. In 3 patients functional abnormalities were found in brain regions that were structurally intact. CONCLUSIONS: Decreased diazepam-enhanced beta activity in the EEG is a sensitive criterion of functional abnormality. In patients with subtle structural abnormalities diazepam-enhanced EEG may have added value in diagnosing functional involvement and in monitoring disease progression in patients.

Adolescent↗
PubMed2001

Neuroradiological assessment of brain structure and function and its implication in the pathogenesis of West syndrome.

Neuroimaging studies with magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning have contributed significantly to our understanding of West syndrome. Cortical dysplastic lesions are the most common abnormalities seen with MRI in infants with spasms, but other structural lesions are also detected occasionally. An underlying cortical dysplasia may not be apparent until myelination has advanced in the brain and poor gray-white matter differentiation becomes observable. Many cortical dysplastic lesions can only be detected using PET scanning of glucose metabolism or gamma-aminobutyric acid(A) (GABA(A)) receptor binding. The MRI and PET findings, together with neurophysiological observations, strongly suggest that infantile spasms are initiated as cortical epileptic discharges that, during a 'critical' developmental period, may undergo secondary generalization in an age-dependent mechanism to emerge as spasms. The onset of spasms often coincides with the functional maturation of cerebral cortex. Based on data from glucose metabolism PET scanning as well as electrophysiological and neurochemical findings on infants with spasms, we have postulated that the offending lesion is a focal or diffuse cortical abnormality which, at a critical stage of maturation, causes abnormal functional interactions with brainstem raphe nuclei which project widely throughout the brain. Raphe-cortical projections could mediate the hypsarrhythmic changes seen on EEG. The prominent serotonergic raphe-striatal pathway and descending spinal pathways may be responsible for secondary generalization of the cortical discharges to result in the relatively symmetric spasms. It is likely that additional factors (e.g. genetic) play a role in the manifestation of the age-specific electroclinical features of West syndrome. Recently developed PET tracers can be used to detect epileptogenic brain regions and also to investigate developmental abnormalities of serotonergic (using the tracer alpha[(11)C]methyl-L-tryptophan) and GABAergic (using [(11)C]flumazenil) neurotransmitter systems. These systems are implicated in epileptogenesis, and their involvement in the pathophysiology of West syndrome can be further addressed by future functional neuroimaging studies.

Brain↗
PubMed2004

Structural associations of osteoarthritis pain: lessons from magnetic resonance imaging.

For many years the search for structural associations of osteoarthritis (OA) pain were based on conventional radiographic imaging that predominantly visualizes bone. As well as being tomographic, magnetic resonance imaging (MRI) has the ability to directly visualize all the structures of a joint, including soft tissue and cartilage. Initial MRI studies focused on cartilage assessment, but recently there has been a growing body of work examining the correlation of structural findings with pain in OA and their relation to structural progression. Painful OA knees have more MRI-detected abnormalities and these pathologies are often correlated making individual contributions difficult to assess. However, in large cohort studies, both synovial hypertrophy and large synovial effusions were demonstrated to be more frequent in patients with OA knee pain. Similarly MRI-determined subchondral bone marrow oedema lesions (BME), particularly large ones, are associated with OA knee pain. Meniscal tears in OA knees, although common, have not been linked with pain. Improved, reliable quantification of the structural features and the rapid advances in MRI technology can only improve structure-pain understanding.

Arthralgia↗
PubMed2005

Neurocircuitry in alcoholism: a substrate of disruption and repair.

The chronic, excessive consumption of alcohol results in significant modification of selective neural systems of the brain structure, physiology, and function. Quantitative MR structural imaging, diffusion tensor imaging (DTI), and functional MRI (fMRI), together with neuropsychological challenges, have enabled rigorous in vivo characterization of the results of alcoholism on the brain in the human condition. Neuroimaging has also enabled longitudinal study for the examination of alcoholism's dynamic course through periods of drinking and sobriety. Controlled studies have revealed compelling evidence for alcohol-related brain structural and functional modification--some longstanding, some transient, and some compensatory. Patterns of circuitry disruption identified through structural and functional MRI studies suggest a central role for degradation of frontocerebellar neuronal nodes and connecting circuitry affecting widespread brain regions and contributing to alcoholism's salient, enduring, and debilitating cognitive and motor deficits--executive dysfunction, visuospatial impairment, and ataxia.

Aging↗
PubMed2006

[Imaging cervical myelo- and radiculopathy].

PURPOSE: This article gives an overview of the diagnostic possibilities available in the diagnosis of cervical myelo- and radiculopathy. We compared conventional myelography, CTM, and MRI. MATERIAL AND METHODS: Twenty-five patients with clinical evidence of cervical myelo- or radiculopathy were included. Sagittal and transverse T1-weighted (T1w) TSE and T2-weighted (T2w) TSE sequences were compared with myelography and CTM. Statistical analysis was performed using Wilcoxon's -test. RESULTS: Disc herniation could be depicted in CTM as well as in MRI. The extent of herniation did not differ between CTM and T1w. The extent of herniation seemed higher on T2w than on T1w (p <0.001). Foraminal encroachment was easier to diagnose in CTM. When regarding transverse T1w and T2w images simultaneously, a missing root in MRI corresponded to a missing root in CTM and conventional myelography and vice versa. Our data demonstrated the relative inability of MRI to determine whether the compression is by soft tissue or bony structures. CONCLUSION: The present study proposes that MRI, when available, should be the imaging method of first choice in patients with suspected radiculo- and myelopathy.

Adult↗
PubMedDate not supplied

[Comparison of ultrasonography and magnetic resonance in the postoperative monitoring of complete subcutaneous rupture of the Achilles tendon].

The diagnostic accuracy of US and MRI in the subcutaneous rupture of the Achilles tendon has already been assessed. We used both techniques to study the Achilles tendon during the postoperative repair process after surgery according to Bosworth. The results were compared and discussed in relation to clinical recovery. Ten patients with complete subcutaneous rupture of the Achilles tendon were followed-up with physical examination and submitted to US and MR studies 40, 60 and 90 days postoperatively. Eighty patients recovered in the expected time, while 2 took longer. At 90 days, the US findings in 7 patients and the MR findings in 8 patients who recovered in the expected time could be considered normal. US poorly distinguished the tendon from the reinforcement flap because of gross tendon echostructure. The tendon and the reinforcement flap were not distinguishable at MRI because they were uniformly hypointense. Clinical recovery appeared as a hyperechoic structure and a gross fibrillar pattern at US and as a hypointense structure with some small hyperintense areas at MRI. US and MRI were in disagreement in one patient with a postoperative algodystrophic syndrome, where US showed some alterations which were considered false positives because of clinical recovery and negative MR findings. US and MR patterns were considered abnormal in the 2 patients with delayed recovery. US showed persistent hyperechoic areas within the tendon, while the MR signal was of intermediate intensity in the tendon and reinforcement flap. To conclude, we believe that US is an appropriate technique for the postoperative follow-up of complex subcutaneous ruptures of the Achilles tendon. Additional MRI should be performed in all the cases where US findings are in disagreement with clinics.

Achilles Tendon↗
PubMed2005

Mean diffusivity and fractional anisotropy histogram analysis of the cervical cord in MS patients.

The spinal cord is frequently involved in multiple sclerosis (MS), and cord damage may be an important contributor to disability. Diffusion tensor magnetic resonance imaging (DT-MRI) provides quantitative information about the structural and orientational features of the central nervous system. In order to assess whether diffusion tensor-derived measures of cord tissue damage are related to clinical disability, mean diffusivity (MD) and fractional anisotropy (FA) histograms from the cervical cord were acquired from a large cohort of MS patients. Diffusion-weighted sensitivity-encoded (SENSE) echo planar images of the cervical cord, and brain dual-echo and diffusion-weighted scans were acquired from 44 patients with MS and 17 healthy controls. Cord and brain MD and FA histograms were produced. An analysis of variance model, adjusting for cord volume and patient age, was used to compare cord DT-MRI parameters from controls and patients. A multivariate linear regression model was used to identify DT-MRI variables independently associated with disability. Average cervical cord FA was significantly lower in MS patients compared to controls. Cord cross-sectional area, average FA and average MD were all significantly correlated with the degree of disability (r values ranging from 0.36 to 0.51). The multivariate linear regression model retained average cord FA and average brain MD as variables independently associated with disability, with a correlation coefficient of 0.73 (P < 0.001). DT-MRI reveals a loss of cervical cord tissue structure in MS patients. The strong correlation found between a composite DT-MRI score and disability suggests that a full and accurate assessment of cervical cord damage in MS provides information that usefully contributes to an explanation of the clinical manifestations of the disease.

Adult↗
PubMed2006

New developments of brain imaging for Parkinson's disease and related disorders.

Parkinson's disease (PD) and related disorders are subcortical degenerations targeting the nigrostriatal dopaminergic system and basal ganglia. Traditionally, MRI has been used to detect structural and positron emission tomography and single emission computed tomography functional neurochemical and metabolic changes associated with these disorders. Recently, advances in diffusion-weighted MRI, ultrasonography, and radiotracer-based imaging have yielded greater sensitivity for revealing structural change and allowed detection of changes in brain dopamine levels after levodopa and during behavioral tasks. This review focuses on these recent advances in neuroimaging technology and their use for the diagnosis and assessment of PD and other parkinsonian disorders.

Blood-Brain Barrier↗
PubMed2001

Structural evaluation of articular cartilage: potential contribution of magnetic resonance techniques used in clinical practice.

OBJECTIVE: To determine whether routine magnetic resonance imaging (MRI) techniques can detect age-related structural modifications of bovine articular cartilage. METHODS: The cartilage of 3-month-old, 3-year-old, and 13-year-old animals was studied. T1- and T2-weighted MR sequences were performed using a 1.5T clinical imager and a 3-inch surface coil. Histologic slices (5 microm) of cartilage specimens were stained with picrosirius red (for collagen) and toluidine blue (for glycosaminoglycans [GAGs]). A polarized light study was performed to determine the collagen network organization. Except for the 13-year-old animal cartilage, the biochemical content was studied on slices cut parallel to the surface to determine GAG and hydroxyproline (collagen) content. Cartilage profiles were performed to determine the MR pixel intensity and the histologic color intensity. RESULTS: On T1-weighted images, the cartilage was homogeneous, with pixel intensity profiles presenting low variations. On T2-weighted images, the cartilage was laminar in the 3-month-old animals and became homogeneous thereafter. The pixel intensity varied through the cartilage depth with a profile that depended on the age of the animal. The collagen and GAG staining showed abrupt transitions in the 3-month-old animal, while in older animals the cartilage became more homogeneous with a mild gradient of matrix constituents with depth. These results were confirmed by findings of a biochemical study. In addition to these matrix content variations, the bovine cartilage presented modifications of its collagen network organization with aging. CONCLUSION: The MR T2-weighted sequences depicted signal variations with age in bovine cartilage concomitant with modifications in its structure. If confirmed in clinics, these observations will reinforce the place of MRI in characterizing cartilage with aging and pathologic processes.

Aging↗