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At least 1,063 records · Page 59Linked to original sources
PubMed2001

A computerized vector manometry and MRI study in children following posterior sagittal anorectoplasty.

The study was designed to evaluate computerized eight-channel vector manometry (8CVM) and pelvic floor magnetic resonance imaging (MRI) as methods to assess the anal sphincter following posterior sagittal anorectoplasty (PSARP) for anorectal malformations, in particular the functional capacity of the sphincter structures in correlation with postoperative MRI findings. Seventeen children had been operated upon for a rectovesical, -urethral, or -vaginal fistula including one female cloacal malformation; 4 had a secondary PSARP. Mean follow-up was 5.57 years. Continence was evaluated with a modified Kelly score. A CVM technique with an eight-channel perfusion catheter was used. In addition to software-supported data, the manometric parameters included a score-system assessing three different pressure zones of the anal canal qualitatively on the three-dimensional image of the anal sphincter profile. The same procedure was performed on sagittal, oblique axial, and oblique coronal MRI. Furthermore, the thickness of the sphincter muscle was assessed at the level of the maximal mean segmental pressure. All children had decreased absolute vector-volumetry values at rest and on squeezing. Correlation with the clinical score was poor. Correlation of the manometric score with the clinical course was similar to the correlation of MRI score with clinical course (R = 0.425; P = 0.1). Thirteen children demonstrated normal or increased sphincter length; 5 of these had a decreased high-pressure zone (HPZ). The position of the anorectum in the sphincter muscles could be evaluated by the vector-volumetry image as anatomic in 11 cases, nearly correctly positioned in 4, and ectopic in 1 child. MRI detected 2 cases of malposition, 10 anatomic, and 4 nearly-anatomic findings. Correlation of the manometric score with the MRI score and the thickness of the sphincter muscle at the HPZ was significantly high (R = 0.801; P < 0.0001). 8CVM is thus highly sufficient in illustrating the function of the sphincter musculature seen on pelvic floor MRI. Both methods only moderately reflect clinical follow-up, since continence depends on more than sphincter ability.

Anal Canal↗
PubMed2001

[Diagnostic imaging in invasive cervical carcinoma: MRI, CT, and ultrasonography].

Carcinoma of the cervix is the fourth most common cancer in women. Accurate staging of the disease is essential in selecting optimal therapy. The clinical staging based on the criteria of the FIGO is inaccurate. With MRI an excellent imaging of the tumour spread within the cervix can be achieved, also tumour extension to the parametria and infiltration of the neighbouring structures as bladder and rectum. MRI is the method of choice in the preoperative staging of cervical cancer. Computed tomography and sonography have lower staging value compared to the MRI. An advantage of CT, compared with MRI, is the high accuracy in investigations of patients with ureteral obstruction and hydronephrosis. Both methods MRI and CT are comparable in assessing pelvic and paraaortic lymph node metastases.

Carcinoma↗
PubMed1987

[MR of the shoulder joint with surface coils at 1.5 tesla. Its anatomy and possible clinical use].

High spatial resolution magnetic resonance images of the shoulder were obtained in axial, sagittal and coronal orientations using a 1.5 T imaging system and anatomically shaped, wrap-around surface coils. Variations in scapular position induced by patient positioning change the relationship of the planes to the shoulder anatomy and make reproducibility of sagittal and coronal planes difficult. We, therefore, use--after axial orientation--image-oblique planes perpendicular and parallel to the glenoid fossa. In this manner MRI can visualise the anatomic structures of the shoulder including rotator cuff, long biceps tendon, articular capsule, articular cartilage, muscles and bones due to the high soft tissue contrast of MRI.

Humans↗
PubMed1988

Imaging modalities for the study of the paranasal sinuses and nasopharynx.

Disease entities affecting the paranasal sinuses and nasopharynx are now evaluated primarily by computed tomography (CT) and magnetic resonance imaging (MRI). Cortical bone is best seen by CT, particularly with thin sections and high-resolution bone mode. Bone marrow and various soft-tissue structures are best evaluated by MRI. This article is a demonstration of the normal anatomy of the area as depicted by both CT and MRI.

Diagnostic Imaging↗
PubMed2004

Quantitative high-resolution magnetic resonance imaging reveals structural implications of renal osteodystrophy on trabecular and cortical bone.

PURPOSE: To explore the potential role of micro-magnetic resonance imaging (micro-MRI) for quantifying trabecular and cortical bone structural parameters in renal osteodystrophy (ROD), a multifactorial disorder of bone metabolism, traditionally evaluated by bone biopsy. MATERIALS AND METHODS: Seventeen hemodialysis patients (average PTH level = 502 +/- 415 microg/liter) were compared with 17 age-, gender-, and body mass index (BMI)-matched control subjects. The average dialysis duration for the patients was 5.5 years (range = 0.96-18.2 years). Three-dimensional (3D) fast large-angle spin-echo (FLASE) MR images of the distal tibia (voxel size = 137 x 137 x 410 microm(3)) were processed to yield bone volume fraction (BV/TV). From a skeletonized representation of the trabecular bone network, the topology of each bone voxel was determined providing surface and curve voxel densities (SURF and CURV) and the topological erosion index (EI). Further, high-resolution two-dimensional (2D) spin-echo images were collected at the tibial midshaft for measurement of cortical bone cross-sectional area (CCA), relative CCA expressed as a percentage of total bone area (RCA), and mean cortical thickness (MCT). RESULTS: The data show both RCA and MCT to be lower in the patients (61.2 vs. 69.1%, P = 0.008, and 4.53 vs. 5.19 mm, P = 0.01). BV/TV and SURF were lower, while EI was increased in the patients, although these differences were not quite significant (P = 0.06-0.09). All of the cortical and trabecular findings are consistent with increased bone fragility. CONCLUSION: The data suggest that micro-MRI may have potential to characterize the structural implications of metabolic bone disease, potentially providing a noninvasive tool for the evaluation of therapies for ROD.

Adult↗
PubMed1991

Morphometry and magnetic resonance imaging of the human brain in normal controls and Down's syndrome.

A new powerful stereological tool for exact quantification of brain structures on magnetic resonance imaging (MRI) scans was used. Applying Cavalieri's principle, unbiased estimation of volume can be obtained. The method was applied to estimate the volume of different brain structures from normal controls. Data were used for comparison with data obtained by analyzing the brains of persons with Down's syndrome. A normalization procedure based on volume of cranial cavity is introduced and its advantages discussed, as is the coefficient of error as an indicator for the precision of the measurement.

Adult↗
PubMed2006

Magnetic resonance imaging changes of sacroiliac joints in patients with recent-onset inflammatory back pain: inter-reader reliability and prevalence of abnormalities.

To study the inter-reader reliability of detecting abnormalities of sacroiliac (SI) joints in patients with recent-onset inflammatory back pain by magnetic resonance imaging (MRI), and to study the prevalence of inflammation and structural changes at various sites of the SI joints. Sixty-eight patients with inflammatory back pain (at least four of the five following criteria: symptom onset before age 40, insidious onset, morning stiffness, duration >3 months, improvement with exercise--or three out of five of these plus night pain) were included (38% male; mean age, 34.9 years [standard deviation 10.3]; 46% HLA-B27-positive; mean symptom duration, 18 months), with symptom duration <2 years. A MRI scan of the SI joints was made in the coronal plane with the following sequences: T1-weighted spin echo, short-tau inversion recovery, T2-weighted fast-spin echo with fat saturation, and T1-spin echo with fat saturation after the administration of gadolinium. Both SI joints were scored for inflammation (separately for subchondral bone and bone marrow, joint space, joint capsule, ligaments) as well as for structural changes (erosions, sclerosis, ankylosis), by two observers independently. Agreement between the two readers was analysed by concordance and discordance rates and by kappa statistics. Inflammation was present in 32 SI joints of 22 patients, most frequently located in bone marrow and/or subchondral bone (29 joints in 21 patients). Readers agreed on the presence of inflammation in 85% of the cases in the right SI joint and in 78% of the cases in the left SI joint. Structural changes on MRI were present in 11 patients. Ten of these 11 patients also showed signs of inflammation. Agreement on the presence or absence of inflammation and structural changes of SI joints by MRI was acceptable, and was sufficiently high to be useful in ascertaining inflammatory and structural changes due to sacroiliitis. About one-third of patients with recent-onset inflammatory back pain show inflammation, and about one-sixth show structural changes in at least one SI joint.

Adult↗
PubMed2005

Strategies for block-design fMRI experiments during task-related motion of structures of the oral cavity.

Functional MRI (fMRI) studies of jaw motion, speech, and swallowing disorders have been hampered by motion artifacts. Tissue motion perturbs the static magnetic field, creating geometric distortions in echo-planar images that lead to many false positives in activation maps. These problems have restricted blood oxygenation level-dependent (BOLD) fMRI studies involving orofacial muscles to event-related designs, which offer weak contrast-to-noise ratios when compared to block designs. Two new approaches are described that greatly reduce false positives in the activation maps created by the distortions in block-design fMRI studies involving jaw and tongue motion during chewing. First, an appropriate task duration of 10-14 s was found to maximize functional contrast while minimizing motion artifacts. Second, three motion-sensitive postprocessing methods were applied successively to examine the temporal and spatial characteristics of responses and identify and remove false positives caused by motion artifacts. These techniques are shown to allow the use of block design in an fMRI study of a jaw motion task. Extension to speech and swallowing tasks is discussed.

Adult↗
PubMed2001

Enlargement of the fornix in early-onset schizophrenia: a quantitative MRI study.

Abnormalities of temporal lobe structure and frontal lobe function occur in schizophrenia. There have been few studies of young people with schizophrenia and little is known about temporo-frontal connectivity in the disease. Therefore, the cross-sectional area of the body of the fornix was measured on MR images from 17 young people with schizophrenia, nine with other serious psychiatric illnesses and eight without illness. The mean age of each group was 16-17 years. The mean cross-sectional fornix area in subjects with schizophrenia was significantly larger than that in subjects without illness ( approximately 40%) and psychiatric controls ( approximately 26%). There was no such significant difference between subjects without illness and psychiatric controls. The nature of the larger fornix in early-onset schizophrenia, whether it persists and whether it occurs in schizophrenia presenting in adulthood, remain to be elucidated.

Adolescent↗
PubMed1999

Evaluation of the spatial accuracy of magnetic resonance imaging-based stereotactic target localization for gamma knife radiosurgery of functional disorders.

PURPOSE: This study was undertaken to determine the impact of geometric distortions on the spatial accuracy of magnetic resonance imaging (MRI)-guided stereotactic localization for gamma knife functional radiosurgery. METHOD: The spatial accuracy of MRI was evaluated by comparing stereotactic coordinates of intracranial targets, external fiducials, and anatomic structures defined by computed tomographic and MRI studies of the Radionics skull phantom (Radionics, Inc., Burlington, MA), the Rando head phantom, and 11 patients who underwent gamma knife functional radiosurgery. The distortion in MRI was assessed from computed tomographic and MRI fusion studies for these patients, as well as from MRI studies acquired by swapping the direction of the magnetic field gradients for five patients who underwent gamma knife radiosurgery and three patients who underwent MRI-guided frameless surgery. A follow-up program to compare the location of the created lesion with the intended target complemented the analysis. RESULTS: The average difference between computed tomographic and MRI stereotactic coordinates of external fiducials, intracranial targets, and anatomic landmarks was of the order of 1 pixel size (0.9 x 0.9 x 1 mm3) along the x, y, and z axes. The average linear scaling along these axes as determined by fusion studies was approximately 0.8% and consistent with a single pixel. The follow-up studies, available for seven patients, revealed good agreement between the location of the created lesion and the intended target. CONCLUSION: The spatial accuracy of an MRI-based localization system can be comparable to computed tomography-based localization with the added benefit of MRI resolution. Both machine- and object-related MRI distortions can be reduced to an acceptable level with contemporary scanners, optimized scanning sequences, and distortion-resistant stereotactic instruments.

Artifacts↗
PubMed1990

Functional magnetic resonance imaging in medicine and physiology.

Magnetic resonance imaging (MRI) is a well-established diagnostic tool that provides detailed information about macroscopic structure and anatomy. Recent advances in MRI allow the noninvasive spatial evaluation of various biophysical and biochemical processes in living systems. Specifically, the motion of water can be measured in processes such as vascular flow, capillary flow, diffusion, and exchange. In addition, the concentrations of various metabolites can be determined for the assessment of regional regulation of metabolism. Examples are given that demonstrate the use of functional MRI for clinical and research purposes. This development adds a new dimension to the application of magnetic resonance to medicine and physiology.

Animals↗
PubMed1986

Magnetic resonance imaging (MRI) in the diagnosis of cerebral arteriovenous angiomas.

Eight patients with angiographically confirmed arteriovenous malformations (AVMs) were studied by CT and MRI. MRI scans were performed with a 0.35 Tesla wholebody scanner using three spin-echo sequences (SE 400/35, SE 1600/35, SE 1600/70). In CT and MRI, pathological findings were obtained in all cases. In MRI AVMs were displayed as lesions of low signal intensity in the applied sequences. Full extent of the lesions as well as the relationship to the surrounding structures were clearly demonstrated in MRI in all patients. Based on the characteristic sequence dependent signal intensity property of the lesions, the differential diagnosis in the sense of an AVM could be obtained by MRI in all cases. Concerning topographical imaging and/or differential diagnosis, MRI was superior to CT in 4 out of 8 cases. MRI offers advantages in the demonstration of AVMs of the cerebral midline, especially in brain stem angiomas.

Brain Neoplasms↗
PubMed1999

Diagnosis of subtle focal dysplastic lesions: curvilinear reformatting from three-dimensional magnetic resonance imaging.

Focal cortical dysplasia is a frequent cause of medically intractable partial epilepsy. These lesions are being increasingly identified by high quality images provided by magnetic resonance imaging (MRI), resulting in improved seizure control of surgically treated patients. Small dysplastic lesions are often missed by conventional MRI methods. The identification of subtle structural abnormalities by rectilinear slices is often limited by the complex convolutional pattern of the brain. We developed a method of curvilinear reformatting of three-dimensional MRI data that improves the anatomical display of the gyral structure of the hemispheric convexities. It also reduces the asymmetric sampling of gray-white matter that may lead to false-positive results. We present 5 patients in whom conventional two-dimensional and three-dimensional MRI with multiplanar reformatting was initially considered normal. Subsequent studies using curvilinear reformatting identified lesions in all. Four patients underwent surgery with histological diagnosis of focal cortical dysplasia. Three patients are seizure-free and 1 had significant improvement in seizure control. These results indicate that an increase in the detection of subtle focal dysplastic lesions may be accomplished when one improves the anatomical display of the brain gyral structure by performing curvilinear reformatting.

Adolescent↗
PubMedDate not supplied

[Fetal magnetic resonance].

UNLABELLED: The increasing use of magnetic resonance imaging (MRI) in fetal evaluation is due to its excellent structural and morphological resolution. We report nine fetal MRI examinations and discuss some of the technical issues related to this technique. METHODS: We report nine fetal MRI done in the MRI Center in Caselas, Portugal, between January 1999 and March 2000. The fetal ages ranged from 24 and 33 weeks of gestation. RESULTS: The MRI diagnoses were: one normal case, two normal variants, two hydrocephalus due to intraventricular hemorrhage, one corpus callosum agenesis, one corpus callosum hypoplasia, one case with white matter encephaloclastic lesions and one case of torcular and superior sagittal sinus dilatation. In one case the MRI confirmed the ultrasonography (US) diagnosis, in two cases the MRI depicted the etiology of the pathologies found with US, in three cases there was a suspicion of pathology with US but the MRI was normal or had normal variants, and in three cases the MRI diagnoses were different from those made by US. CONCLUSIONS: MRI has the highest sensitivity for fetal imaging and should be used if the US is insufficient to establish the diagnosis.

Female↗
PubMed1992

The significance of diagnostic imaging in acute and chronic brain damage in boxing. A prospective study in amateur boxing using magnetic resonance imaging (MRI).

The significance and possible extent of structural damage to the central nervous system (CNS) due to boxing are investigated. Bleeding, especially microhematomas, is considered to be one probable cause of the chronic encephalopathy in boxers. In a prospective study, 13 amateur boxers were investigated with the help of MRI several times before and after their fights. The MRI investigations were accompanied by neurologic examinations before and after the fights. Among the 13 boxes, 5 demonstrated focal neurological signs following the fights, without evidence of small hematoma or other structural alterations. The number of head punches did not correlate with the occurrence of neurologic signs. These results indicate that up to now imaging methods cannot clarify the development of chronic encephalopathy.

Acute Disease↗
PubMed2003

Quantitative MR image analysis in subjects with defects in the PAX6 gene.

Cerebral development is governed by genetic and environmental factors. Animal models provide much of our knowledge about genetic influences in the brain but it is not clear how similar or relevant these are to the human brain. The investigation of human subjects with mutations in genes known to be expressed in the developing brain is an alternative approach to improving our understanding of the role of genetic factors in brain development. We investigated 24 subjects with known mutations in the PAX6 gene (including representatives of all the known mutations of the gene) which are associated with characteristic ocular abnormalities in humans and animals. We have quantified MRI data using several techniques to assess qualities of cerebral structure which are difficult to interpret visually. Abnormalities were identified using voxel-based morphometry, statistical morphometrics, and measurement of corpus callosum cross-sectional area when comparing data from subjects with PAX6 abnormality and 72 age-and sex-matched control subjects. These abnormalities include grey matter changes in the cerebellum and occipital poles and white matter loss in the corpus callosum, alteration of sulcal orientation in the occipital lobe, and alteration to overall neuronal connectivity. These abnormalities complement and exceed the changes seen in the mouse models, and those seen on visual inspection alone of the human MRI data. Structural differences were also identified between the two largest genotype mutation subgroups.

Adult↗
PubMed2003

Mesial temporal damage in temporal lobe epilepsy: a volumetric MRI study of the hippocampus, amygdala and parahippocampal region.

Despite neuropathological and electrophysiological evidence for the involvement of parahippocampal structures in temporal lobe epilepsy (TLE), little attention has been paid to morphometric measurements of these structures in patients with TLE. Using high resolution MRI, we previously showed that the volume of the entorhinal cortex was decreased in patients with TLE. The purpose of this study was: (i) to determine whether changes in the volume of the perirhinal cortex and posterior parahippocampal cortex were detectable by MRI; and (ii) to study the distribution and degree of atrophy in mesial temporal structures including the hippocampal head, body and tail, amygdala, entorhinal cortex, perirhinal cortex and posterior parahippocampal cortex. MRI volumetric analysis was performed using a T(1)-weighted three-dimensional gradient echo sequence in 20 healthy subjects and 25 TLE patients with intractable TLE. In patients with either left or right TLE, the hippocampal head, body and tail and the entorhinal and perirhinal cortices ipsilateral to the seizure focus were significantly smaller than in normal controls. The mean volume of the posterior parahippocampal cortex was not different from that of normal controls. Within the hippocampus, the hippocampal head was more atrophic than the hippocampal body and hippocampal tail. Within the parahippocampal region, the entorhinal cortex was more severely affected than the perirhinal cortex. Our MRI results confirm pathological findings of damage in the mesial temporal lobe, involving not only the hippocampus and the amygdala, but also the entorhinal and perirhinal cortices. The pattern of atrophy may be explained by cell loss secondary to a disruption of entorhinal-hippocampal connections as a result of privileged electrical dialogue between these two structures.

Adolescent↗
PubMed1999

Visualizing and characterizing white matter fiber structure and architecture in the human pyramidal tract using diffusion tensor MRI.

We used diffusion tensor imaging to assess diffusion anisotropy in the pyramidal tract in ten young, and ten elderly subjects (five males and five females in each group). The purpose of this study was to define normative values for anisotropy at different anatomic levels of the brainstem as well as to assess differences due to age, gender, and laterality. In all subjects, anisotropy was highest in the cerebral peduncle, lowest in the caudal pons, and intermediate in the medulla. In the pons and medulla the regional variability was high, with significant differences in anisotropy even between contiguous slices. Multifactorial ANOVA (performed using the average value of anisotropy within each region of interest) revealed that elderly subjects had significantly lower values than young subjects in the cerebral peduncle, with no differences in the pons and medulla. No significant differences in anisotropy due to gender and side were found. The differences in anisotropy at different levels of the brainstem reflect differences in the local architecture of white matter fibers. Anisotropy is high in the cerebral peduncle because fibers have a highly ordered arrangement, while in the pons and medulla, anisotropy is lower because the local fiber architecture is less coherent due to the presence of other fibers and nuclei. The biologic meaning of the intergroup differences in anisotropy is discussed in light of the structure and architecture of the tissue under investigation. We also consider potential sources of artifacts, such as noise and motion, partial volume contamination, anatomic mismatching, and the use of inappropriate statistical tests. We conclude that the age-related decrease in anisotropy in the cerebral peduncle is not artifactual but rather reflects subtle structural changes of the aging white matter. Our study however shows that caution must be exercised in interpreting diffusion anisotropy data.

Adult↗