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At least 1,729 records · Page 96Linked to original sources
PubMed1988

[Nuclear magnetic resonance tomography study in orbital diseases with surface coils].

MRI of the orbit with surface coils was performed in 40 patients. In 35 cases the findings were pathologic. The most frequent (n = 9) were malignant melanomas of the choroid, which were distinguishable from hemorrhages (n = 2) by the characteristic signal intensity pattern. MRI only offered advantages over CT in lesions of the orbital apex, the upper part of the orbit, and in the diagnosis of inflammatory processes. In most of the cases of orbital tumors, and particularly where there was involvement of bony structures, CT was equal to or better than MRI.

Adenoma↗
PubMed1998

A new diagnostic approach to vascular rings and pulmonary slings: the role of MRI.

UNLABELLED: The conventional diagnostic work-up of a patient suspected of having a vascular cause for stridor, or dysphagia, includes esophagography and bronchoscopy to delineate the abnormal structure without imaging the structure itself. Cine-angiography is regarded as the golden standard, but is not routinely performed. Magnetic resonance imaging (MRI) is non-invasive and has the important advantage over cine-angiography of depicting all structures in the field of view. Color Doppler echocardiography depicts the great vessels, but not the esophagus and trachea. In 14 patients with obstructive symptoms and in four patients without obstructive symptoms MRI successfully imaged the abnormal structure, as was the case in two symptomatic patients using computer tomography. In this series, the findings were confirmed at surgery or by cine-angiography. CONCLUSION: we suggest that in patients suspected of having a vascular cause for stridor or dysphagia, MRI should be performed. If there is need for a screening procedure, color Doppler echocardiography should be used and if that is equivocal or non-conclusive, esophagography and bronchoscopy should be used. If MRI is difficult to interpret, it should be augmented by magnetic resonance angiography before considering cine-angiography.

Adult↗
PubMed1995

Magnetic resonance imaging for diagnosis of pituitary macrotumors in dogs.

The value of magnetic resonance imaging (MRI) for the evaluation of dogs with pituitary-dependent hyperadrenocorticism (PDH) and CNS signs was assessed. Magnetic resonance imaging of the brain was performed in 13 dogs with PDH and neurologic signs. The diagnosis of PDH was made on the basis of results of adrenocortical function tests and abdominal ultrasonography, in conjunction with appropriate history, clinical signs, and clinicopathologic alterations. Eight dogs had been treated with the adrenocorticolytic agent, mitotane, for 1 to 30 months before the development of neurologic signs. Prior to MRI, each dog had progressive neurologic signs that could not be attributed to hypocortisolism or mitotane toxicosis. The neurologic signs most frequently detected were disorientation and ataxia. Mean age of dogs at the time neurologic signs developed was 9.5 years. Sex predilection was not detected; however, most were large-breed dogs, with 11 of the 13 dogs weighing more than 20 kg. A large mass in the pituitary gland, suprasellar region, or both was easily identified on the magnetic resonance images of each dog. The masses ranged from 8 to 24 mm in size. Expansion of tumors into the suprasellar region and compression of structures adjacent to the pituitary gland were readily detected by MRI. Contrast enhancement did not improve tumor identification, but did enable better delineation between tumor and surrounding structures. After the diagnosis of a macrotumor was made by MRI, radiotherapy was initiated in 9 dogs and was successfully completed in 6. Three dogs had a relapse of neurologic signs 8, 11, and 26 months after radiotherapy was completed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Simulation of nonwetting phase entrapment within porous media using magnetic resonance imaging.

Models representing the pore structures of amorphous, mesoporous silica pellets have been constructed using magnetic resonance images of the materials. Using magnetic resonance imaging (MRI), maps of the macroscopic (approximately 0.01-1 mm) spatial distribution of porosity and pore size were obtained. The nature and key parameters of the physical mechanism for mercury retraction, during porosimetry experiments on the silica materials, were determined using integrated gas sorption experiments. Subsequent simulations of mercury porosimetry within the structural models derived from MRI have been used to successfully predict, a priori, the point of the onset of structural hysteresis and the final levels of mercury entrapment for the silicas. Hence, a firm understanding of the physical processes of mercury retraction and entrapment in these amorphous silica materials has been established.

Computer Simulation↗
PubMed2006

The value of specific MRI features in the evaluation of suspected placental invasion.

OBJECTIVE: The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. SUBJECTS AND METHODS: A retrospective review of the prenatal MR scans of 10 patients with a diagnosis of placenta accreta, placenta increta or placenta percreta made by pathologic and clinical reports and of 10 patients without placental invasion was performed. Two expert MRI readers were blinded to the patients' true diagnosis and were asked to score a total of 17 MRI features of the placenta and adjacent structures. The interrater reliability was assessed using kappa statistics. The features with a moderate kappa statistic or better (kappa > .40) were then compared with the true diagnosis for each observer. RESULTS: Seven of the scored features had an interobserver reliability of kappa > .40: placenta previa (kappa = .83); abnormal uterine bulging (kappa = .48); intraplacental hemorrhage (kappa = .51); heterogeneity of signal intensity on T2-weighted (T2W) imaging (kappa = .61); the presence of dark intraplacental bands on T2W imaging (kappa = .53); increased placental thickness (kappa = .69); and visualization of the myometrium beneath the placenta on T2W imaging (kappa = .44). Using Fisher's two-sided exact test, there was a statistically significant difference between the proportion of patients with placental invasion and those without placental invasion for three of the features: abnormal uterine bulging (Rater 1, P = .005; Rater 2, P = .011); heterogeneity of T2W imaging signal intensity (Rater 1, P = .006; Rater 2, P = .010); and presence of dark intraplacental bands on T2W imaging (Rater 1, P = .003; Rater 2, P = .033). CONCLUSIONS: MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.

Case-Control Studies↗
PubMed2006

Contrast-enhanced 3D MRI of lung perfusion in children with cystic fibrosis--initial results.

This paper is a feasibility study of magnetic resonance imaging (MRI) of lung perfusion in children with cystic fibrosis (CF) using contrast-enhanced 3D MRI. Correlation assessment of perfusion changes with structural abnormalities. Eleven CF patients (9 f, 2 m; median age 16 years) were examined at 1.5 T. Morphology: HASTE coronal, transversal (TR/TE/alpha/ST: 600 ms/28 ms/180 degrees /6 mm), breath-hold 18 s. Perfusion: Time-resolved 3D GRE pulse sequence (FLASH, TE/TR/alpha: 0.8/1.9 ms/40 degrees ), parallel imaging (GRAPPA, PAT 2). Twenty-five data sets were acquired after intravenous injection of 0.1 mmol/kg body weight of gadodiamide, 3-5 ml/s. A total of 198 lung segments were analyzed by two radiologists in consensus and scored for morphological and perfusion changes. Statistical analysis was performed by Mantel-Haenszel chi-square test. Results showed that perfusion defects were observed in all patients and present in 80% of upper, and 39% of lower lobes. Normal lung parenchyma showed homogeneous perfusion (86%, P<0.0001). Severe morphological changes led to perfusion defects (97%, P<0.0001). Segments with moderate morphological changes showed normal (53%) or impaired perfusion (47%). In conclusion, pulmonary perfusion is easy to judge in segments with normal parenchyma or severe changes. In moderately damaged segments, MRI of lung perfusion may help to better assess actual functional impairment. Contrast-enhanced 3D MRI of lung perfusion has the potential for early vascular functional assessment and therapy control in CF patients.

Adolescent↗
PubMed1998

[Magnetic resonance imaging of hypopharyngeal and cervical esophageal cancer].

Imaging by MR (MRI) and esophageal barium meal of 17 cases of hypopharyngeal and cervical esophageal cancer were analyzed. The results indicate that esophageal barium meal can not demonstrate the invading of neoplasms to the adjacent structure. Therefore, it is difficult to use the only data of esophageal barium meal for TNM staging. The results also indicate that MRI is more useful and reliable in assessing the three dimensional structure and the neoplasms invading to the adjacent structure. This results suggest that MRI is that useful in determining the diagnosis, TNM staging and the determining the appropriate operative therapy for hypopharyngeal and cervical esophageal cancer.

Adult↗
PubMed2004

Magnetic resonance imaging of isolated single liposome by magnetic resonance force microscopy.

Magnetic resonance imaging (MRI) is very useful spectroscopy to visualize a three-dimensional (3D) real structure inside the sample without physical destruction. The spatial resolution of the readily available MRI spectrometer is, however, limited by a few ten to hundreds of microns due to a technological boundary of generating larger magnetic field gradient and to the insensitivity inherent to the inductive signal detection. Magnetic resonance force microscopy (MRFM) is new alternative MRI spectroscopy which is anticipated to significantly surpass the conventional MRI in both resolution and sensitivity. We report two imaging experiments on our MRFM spectrometer operated at room temperature and in vacuum approximately 10(-3)Pa. One is for approximately 20 microm liposome membrane labeled entirely by a nitroxide imaging agent and the other for approximately 15 microm DPPH particles, both are nearly the same size as that of human cell. The reconstructed images at spatial resolution approximately 1 microm were in satisfactory agreement with the scanning electron microscope images. The potential capability of visualizing intrinsic radicals in the cell is suggested to investigate redox process from a microscopic point of view.

Biphenyl Compounds↗
PubMed2000

Qualitative MRI findings in patients with schizophrenia: a controlled study.

A variety of brain structural abnormalities, which can be identified only by qualitative methods, have been shown to correlate with clinical presentation and course of schizophrenia. In the present study, MRI scans of 122 patients with DSM-IV schizophrenia and 81 non-psychiatric controls were evaluated. Among males, the frequency of CNS developmental abnormalities (CDAs) was higher in patients than in controls. Lateral ventricular enlargement (LVE) was more frequent in patients than in controls; when subjects were grouped in three age classes, LVE was more frequent in patients than in controls in the youngest and the oldest age group. Patients with LVE or third VE were older than those without these abnormalities. Schizophrenic patients with LVE or cortical atrophy (CA) had a longer duration of illness than those without these abnormalities. Both patients with LVE and those with third VE had a poorer outcome than those without these abnormalities. CDA findings add to the evidence of a higher frequency of neurodevelopmental abnormalities in male schizophrenic patients. Results concerning LVE suggest that both developmental and degenerative processes underlie this abnormality. The association of LVE and third VE with a poor outcome indicates that qualitative MRI evaluation might be of clinical relevance.

Adolescent↗
PubMed2006

Hippocampal T2 signal change during amygdala kindling epileptogenesis.

PURPOSE: The rat electrical amygdala kindling model is one of the most widely studied animal models of temporal lobe epilepsy (TLE); however, the processes underlying epileptogenesis in this model remain incompletely understood. Magnetic resonance imaging (MRI) is a powerful method to investigate epileptogenesis, allowing serial imaging of associated structural and functional changes in vivo. Here we report on the results of serial MRI acquisitions during epileptogenesis in this model. METHODS: Serial T2-weighted MR images were acquired before, during, and after the induction of kindling, to investigate the development and progression of imaging abnormalities. RESULTS: T2-weighted acquisitions demonstrated the development of regions of increased signal in the rostral ipsilateral regions of CA1 and dentate gyrus in kindled (five of seven) but not in control rats (p < 0.05). Quantification of the T2 signal demonstrated a significant increase in kindled animals when compared with controls, 2 weeks after kindling ceased, in the ipsilateral hippocampus and the hippocampal sub regions of CA1 and the dentate gyrus (p < 0.05). No significant difference was observed in hippocampal volumes between kindled or control animals at any of the times. CONCLUSIONS: The results of this study validate a method for acquiring serial MRI during amygdala kindling and demonstrate the induction of T2 signal abnormalities in focal regions of the hippocampus. These regions may be important sites for the neurobiologic changes that contribute to epileptogenesis in this model.

Amygdala↗
PubMed1999

The radiological findings in chronic expanding hematoma.

OBJECTIVE: To identify the characteristic MRI findings of chronic expanding hematoma correlated with the pathology. DESIGN AND PATIENTS: Three patients who had a chronic expanding hematoma involving the musculoskeletal system were reviewed retrospectively. RESULTS AND CONCLUSION: Huge soft tissue masses suggestive of malignancy with destruction of the bony structure were revealed on radiography and computed tomography. MRI showed the masses to exhibit heterogeneous signal intensity on both T1 and T2-weighted images with a peripheral rim of low signal intensity, reflecting the central zones of fluid collection due to fresh and altered blood with a wall of collagenous fibrous tissue. These MRI findings were seen in all three patients and are considered to be characteristic; they assist in differentiation from neoplasm in consideration of the history of trauma or surgery.

Aged↗
PubMedDate not supplied

Preoperative assessment of local tumor extent in advanced rectal cancer: CT or high-resolution MRI?

BACKGROUND: We compared high-resolution magnetic resonance imaging (MRI) with computed tomography (CT) in the assessment of tumor infiltration in surrounding structures for locally advanced primary and recurrent rectal cancer. METHODS: Twenty-six patients with operable, locally advanced rectal cancer (15 recurrent and 11 primary) were evaluated with conventional pelvic CT and 1.5-T high-resolution MRI with a quadrature phased-array coil. The images were scored for invasion of nine neighboring pelvic structures, and the results were compared with surgical and histologic findings. RESULTS: A total of 234 structures in 26 patients was evaluated for tumor invasion. For MRI the, sensitivity was 97% and the specificity 98%; for CT, the sensitivity was 70% and the specificity was 85%. The difference in performance was statistically significant (p<0.001). The failure most frequently made on CT was the false-positive prediction of pelvic floor and piriform muscle invasion (14), whereas MRI showed only four false-positive predictions. MRI correctly predicted all four cases of sacral bone invasion, three of which were missed by CT. MRI was accurate in 20 patients (80%) and CT in only five patients (19%). CONCLUSION: High-resolution MRI using a quadrature phased-array coil is highly accurate and superior to CT in predicting tumor infiltration in surrounding structures for locally advanced primary or recurrent rectal cancer and is recommended in the preoperative work-up of these tumors.

Adenocarcinoma↗
PubMed1999

Schizophrenia with onset after age 50 years. 2: Neurological, neuropsychological and MRI investigation.

BACKGROUND: Late-onset schizophrenia (LOS) may have a basis in age-related coarse brain disease, but empirical support for this is conflicting. AIMS: Is LOS characterised by more neurological disease than early-onset schizophrenia (EOS)? METHODS: DSM-III-R-defined LOS subjects (n = 27) were compared with 30 EOS and 34 volunteer control subjects on neurological status, neuropsychological test performance and brain magnetic resonance imaging (MRI). RESULTS: LOS and EOS groups had more 'soft' neurological signs and drug-induced movement abnormalities, and performed more poorly on tests assessing speed of information processing, memory and frontal executive functioning. On MRI, the LOS and EOS groups had greater lateral ventricular size than the control group. The LOS subjects also had more signal hyperintensities in periventricular white matter and subcortical nuclei than controls. CONCLUSIONS: LOS and EOS subjects were very similar on neuropsychological, neurological and structural neuroimaging parameters, except that there were more MRI periventricular hyperintensities in LOS subjects.

Age of Onset↗
PubMedDate not supplied

Structural brain abnormalities in first-episode mania.

Using magnetic resonance imaging (MRI), we studied brain morphometric differences between patients with first-episode mania (n = 17) and normal control subjects (n = 16). Patients were admitted for their first psychiatric hospitalization and met DSM-III-R criteria for bipolar disorder, manic or mixed. Diagnoses were made using the Structured Clinical Interview for DSM-III-R. Patients and control subjects were matched for age, gender, height, past history of substance abuse, and handedness, although control subjects had attained higher levels of education. MRI inversion recovery coronal scans were used for measurements. Volumetric measurements were obtained for cerebral hemispheres, lateral and third ventricles, caudate, thalamus, and cingulate gyrus. Patients with first-episode mania demonstrated significantly larger third-ventricular volumes, possibly increased lateral ventricular volumes, and differences in gray/white matter distribution compared with normal control subjects. The possible pathophysiological meaning of these findings is discussed.

Adolescent↗
PubMed2006

High-resolution MRI: in vivo histology?

For centuries scientists have been fascinated with the question of how the brain works. Investigators have looked at both where different functions are localized and how the anatomical microstructure varies across the brain surface. Here we discuss how advances in magnetic resonance imaging (MRI) have allowed in vivo visualization of the fine structure of the brain that was previously only visible in post-mortem brains. We present data showing the correspondence between definitions of the primary visual cortex defined anatomically using very high-resolution MRI and functionally using functional MRI. We consider how this technology can be applied to allow the investigation of brains that differ from normal, and what this ever-evolving technology may be able to reveal about in vivo brain structure in the next few years.

Brain↗
PubMed1991

Treatment planning for stereotactic radiosurgery of intra-cranial lesions.

Stereotactic radiosurgery of intra-cranial lesions is a treatment modality where a well defined target volume receives a high radiation dose in a single treatment. Our technique delivers this dose using a set of non-coplanar arcs and small circular collimators. We use a standard linear accelerator in our treatments, and the adjustable treatment parameters are: isocenter location, gantry arc rotation interval, couch angle, collimator field size, and dose. The treatment planning phase of the treatment determines these parameters such that the target volume is sufficiently irradiated, and dose to surrounding healthy tissue and critical, dose-limiting structures is minimized. The attachment of a BRW localizing frame to the patient's cranium combined with CT imaging (and optionally MRI or angiography) provides the required accuracy for localizing individual structures in the treatment volume. The treatment is fundamentally 3-dimensional and requires a volumetric assessment of the treatment plan. The selection of treatment arcs relies primarily on geometric constraints and the beam's eye view concept to avoid irradiating critical structures. The assessment of a treatment plan involves isodose distributions throughout the volume and integral dose-volume histograms. We present the essential concepts of our treatment planning approach, and illustrate these in three clinical cases.

Adolescent↗
PubMed1998

Usefulness of heavily T2-weighted magnetic resonance imaging in patients with cerebellopontine angle tumors.

OBJECTIVE: Heavily T2-weighted magnetic resonance imaging (MRI) has been reported to be useful for the diagnosis of lesions of the inner ear or its central connections. We evaluated the usefulness of heavily T2-weighted MRI in 18 patients with cerebellopontine angle tumors. METHODS: The lesions were acoustic neuromas in 14 patients and meningiomas in 4 patients. The findings of heavily T2-weighted MRI were compared with those of three-dimensional T1-weighted gradient field echo MRI. RESULTS: An accurate description of the situation of the tumor in the internal auditory canal (IAC) was possible, because the inner ear was clearly shown on the heavily T2-weighted magnetic resonance images. We could therefore detect the acoustic neuromas located at the fundus of the IAC and the meningiomas growing into the IAC. The residual tumor in the IAC can be shown postoperatively. It was difficult to demonstrate these findings using three-dimensional T1-weighted gradient field echo MRI because of the poor presentation of the petrous bone structures. The lower cranial nerves and the VIIth and VIIIth cranial nerves were more clearly demonstrated by heavily T2-weighted MRI than by three-dimensional T1-weighted gradient field echo MRI. Using heavily T2-weighted MRI, the VIIth and VIIIth cranial nerves of the lesion side were demonstrated in half of the patients with acoustic neuromas smaller than 2.5 cm. CONCLUSION: We conclude that heavily T2-weighted MRI is useful to detect the relationship among the tumor, the IAC, the inner ear, and the surrounding cranial nerves.

Adult↗
PubMed1995

[Fast and ultra-fast MRI imaging of the heart].

Conventional magnetic resonance imaging (MRI) is capable of providing satisfactory morphological images of the heart and the surrounding structures. It has further evolved into a well accepted modality for functional cardiac studies such as flow quantification and volumetry. MRI has, however, been hampered by long image acquisition times. This combined with its non-real-time nature and the limited spatial resolution hs made it difficult to extend MRT to the study of small cardiac structures. Recent technical improvements have made breath-held or real-time MRI feasible and thus laid the foundations for further applications in the field of cardiovascular imaging, notably MR coronary angiography, imaging of cardiac valve leaflets, as well as first-pass perfusion studies. Moreover ultrafast MR techniques may eventually replace conventional data acquisition strategies and thus drastically increase patient throughput by shortening acquisition time. This article provides an overview of the technical advances in MRI and their application to the cardiovascular system and discusses possibilities of combined ultrafast and interventional strategies.

Echo-Planar Imaging↗