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Biomedical subjects

E G Amparo

Publications and source records attributed to E G Amparo.

At least 19 recordsLinked to original sources
PubMed1995

Preclinical evaluation of manganese carbonate particles for magnetic resonance imaging of the liver.

RATIONALE AND OBJECTIVES: We characterized the physical, biological, and imaging properties of a manganese (Mn) carbonate particle suspension, a contrast agent for hepatic magnetic resonance (MR) imaging. METHODS: Mn carbonate suspensions were produced by controlled precipitation and characterized using light microscopy, transmission electron microscopy, and in vitro relaxivity studies. Efficacy of the agent was studied in normal and tumor-bearing rats using T1-weighted MR imaging. RESULTS: Following intravenous injection of Mn carbonate particles at doses ranging from 10 to 100 mumol Mn/kg, peak hepatic contrast enhancement of approximately 35% occurred from about 125 min until the termination of the MR imaging studies that varied from 125 to 305 min. Lesion conspicuity was increased because of relative intensity differences between normal liver and tumor. Data also showed that Mn carbonate particles dissolved on delivery to the liver, allowing Mn to interact with intrahepatic macromolecular complexes to provide positive contrast enhancement. CONCLUSION: Mn carbonate particles produce significant and sustained hepatic enhancement and should improve detection of small or isointense liver lesions.

Analysis of Variance↗
PubMed1992

Is there a role for diskography in the era of magnetic resonance imaging? Prospective correlation and quantitative analysis of computed tomography-diskography, magnetic resonance imaging, and surgical findings.

We herein report the results of a prospective study to define the role of diskography in the diagnosis of low back pain in an emerging era of magnetic resonance imaging (MRI). The study involved 32 patients (78 disks) with a clinical diagnosis of lumbar disk herniation; all were studied by computed tomography-diskography (CT-D), and 25 (51 disks) were also examined using MRI. The disks were graded on these studies according to a staging scheme modified from Modic. Ten of the patients (13 disks) having both CT-D and MRI underwent exploratory surgery, and the staging at surgery served as the standard against which the evaluative studies were judged. Surgical staging was compatible with the CT-D and MRI results in five disks, while in another five disks it was compatible only with the CT-D results. In the remaining three disks, both CT-D and MRI misidentified the stages. In six disks, CT-D more accurately defined the stage of disease than did MRI, whereas MRI was more precise than CT-D in only one disk. While having documented the value of CT-D as a source of information, particularly when surgery is contemplated, and as an effective means of staging disk herniation, we recommend MRI as the ideal screening test for lumbar radiculopathy and low back pain, reserving diskography for problematic cases.

Adult↗
PubMed1991

Anatomic variation of the corpus callosum in persons with gender dysphoria.

Previous postmortem anatomical studies have demonstrated differences between male and female in the size and shape of the splenium of the corpus callosum. The current study using the magnetic resonance imager compares the corpus callosum in 20 transsexuals and 40 controls to determine if the anatomic variance is related to anatomic sex or gender identity. No statistical differences were found in the cross-sectional areas of the entire corpus callosum, regardless of genetic sex or gender. However, the genetic males did have a larger whole-brain cross-sectional area. Also, even though there was a wide range of differences in shape and size in the splenium, the study found no significant differences between the sexes or between transsexual patients of either sex and the controls.

Adult↗
PubMed1990

Localization of auditory response sources using magnetoencephalography and magnetic resonance imaging.

Magnetoencephalography offers the possibility of localizing accurately and noninvasively the source of intracranial currents associated with normal and abnormal brain activity. The purpose of this study was to assess the validity and across-subject reliability of localization of cortical sources responding to ipsilateral and contralateral auditory stimulation. Magnetic evoked fields to both stimulation conditions were measured in eight consecutive normal subjects, and the cortical sources of these fields were estimated on the basis of these measurements. Subsequent projection of the source location coordinates onto magnetic resonance images showed that in all subjects the sources were accurately estimated to fall in the vicinity of the auditory cortex and that two separate sources may account for the response to ipsilateral and contralateral stimulation.

Acoustic Stimulation↗
PubMed1990

Magnetic resonance imaging and neuropsychological findings in human immunodeficiency virus infection.

Neurobehavioral functioning and magnetic resonance imaging (MRI) were investigated in 25 patients with various Centers for Disease Control (CDC) stages of human immunodeficiency virus (HIV) infection and in a control group of seven normal subjects. Unequivocal slowing of information processing speed and cerebral atrophy were related to the stage of HIV infection, with patients in CDC group IV exhibiting the most abnormal findings. Slowing of response speed was directly related to the severity of cerebral atrophy.

Adult↗
PubMed1989

Dichotic listening and manual performance in relation to magnetic resonance imaging after closed head injury.

In order to investigate post-traumatic hemispheric disconnection effects, dichotic listening and intermanual tasks were administered to 69 patients who had sustained a closed head injury of varying severity. The manual tasks consisted of naming objects palpated in either hand, transfer of postures from one hand to the other and writing. Consistent with predictions, the degree of ear asymmetry in dichotic listening performance was directly related to the severity of the head injury as reflected by the degree of impaired consciousness. Depth and localisation of parenchymal lesion characterised by magnetic resonance imaging were also related to the degree of ear asymmetry. Parenchymal lesions situated in sites which could potentially interfere with callosal auditory or geniculocortical pathways produced a greater disparity in response to left versus right ear inputs as compared with parenchymal lesions in areas such as the frontal lobes which are purportedly unrelated to asymmetries in dichotic listening performance. The results provide further evidence for the effects of multifocal brain lesions involving the white matter on tasks which require intra and/or interhemispheric integration.

Adolescent↗
PubMed1989

Magnetic resonance imaging after closed head injury in children.

Magnetic resonance imaging (MRI) was performed in a series of 21 children and adolescents who had been hospitalized after sustaining closed head injuries of varying severity at least 6 months previously. Areas of high intensity in the parenchyma were present in 8 of the 11 severely injured patients, whereas MRI findings were normal in all 10 patients with mild-to-moderate head injuries. Lesions involving the subcortical white matter were confined to severely injured patients whose clinical features were compatible with diffuse axonal injury. Neuropsychological assessment disclosed deficits primarily in the severely injured patients; these deficits were significantly associated with persistent lesions visualized by MRI. Serial MRI and neurobehavioral assessment following early injury may be useful in documenting cognitive impairment in relation to structural alterations of the young brain.

Adolescent↗
PubMed1989

Neurobehavioral and magnetic resonance imaging findings in two cases of decompression sickness.

Two divers underwent neurobehavioral examinations and magnetic resonance imaging (MRI) while hospitalized during the first 2 weeks after sustaining decompression sickness (DCS). Their neurologic findings included a Brown-Séquard Syndrome consistent with spinal cord lesion, and focal deficits consistent with cerebral lesion(s). MRI revealed subcortical white matter lesions in the brains of both divers, whereas no lesion of the spinal cord was demonstrated. The patients exhibited neurobehavioral sequelae including disturbances of memory, divergent thinking, and visuospatial and motor functioning. Focal neurologic deficits resolved in both patients, and their cognitive and memory problems improved slowly. Findings in these two divers raise the possibility that cerebral insult more frequently accompanies spinal cord injury in DCS than previously thought.

Adult↗
PubMed1988

Intramural hemorrhage simulating gastric neoplasm.

We report a case of benign gastric ulcer with secondary extensive intramural hemorrhage causing a radiographic appearance consistent with a large ulcerated gastric neoplasm. This is the second such case reported and the first studied with sonography and computed tomographic scan. A brief review of the literature on intramural gastric hematoma is presented.

Adult↗
PubMed1988

Renal transplant dysfunction: MR evaluation.

The results of 45 MR examinations were prospectively compared with the clinical course and biopsy results in 38 renal transplant patients to determine the role of MR in evaluating allograft dysfunction. Twenty-six patients underwent allograft biopsy. In eight patients in whom the biopsy was performed more than 48 hr after MR examination and in 19 patients who did not have a biopsy, the subsequent clinical course was sufficiently diagnostic to determine the specific cause of the transplant dysfunction. Corticomedullary differentiation, graded from 0 to 3, was not helpful in separating rejection (n = 20) from acute tubular necrosis (n = 9), drug toxicity (n = 7), pyelonephritis (n = 2), or normal grafts (n = 7) because of overlap between groups (sensitivity =; 60%, specificity = 60%). In the six patients with two or more MR studies, serial changes in corticomedullary differentiation were not consistent and could not be used to diagnose rejection. When any abnormality of allograft sinus fat, size or shape, or corticomedullary differentiation was considered, the sensitivity for the diagnosis of rejection approached 80%; however, specificity was low (48%). We conclude that MR imaging is not sufficiently accurate to replace transplant biopsy and therefore has a limited role in the evaluation of transplant dysfunction.

Cyclosporins↗
PubMed1988

Relationship of depth of brain lesions to consciousness and outcome after closed head injury.

Magnetic resonance (MR) imaging was performed in 94 patients who sustained closed head injury of varying severity. Results of MR studies obtained after the intensive care phase of treatment disclosed that intracranial lesions were present in about 88% of the patients. Consistent with the centripetal model of progressive brain injury proposed in 1974 by Ommaya and Gennarelli, the depth of brain lesion was positively related to the degree and duration of impaired consciousness. Further analysis indicated that the relationship between depth of brain lesion and impaired consciousness could not be attributed to secondary effects of raised intracranial pressure or to the size of intracranial lesion(s).

Adolescent↗
PubMed1988

MRI of cervical carcinoma.

MRI is useful for demonstrating enlarged retroperitoneal lymph nodes and for demonstrating the carcinoma mass in patients with carcinoma of the cervix. MRI evaluation of the parametria appears promising, but further studies are necessary to elucidate the optimal imaging parameters and to better define the overall accuracy of MRI compared to the clinical evaluation of the parametria.

Carcinoma↗
PubMed1987

Developmental features of the neonatal brain: MR imaging. Part I. Gray-white matter differentiation and myelination.

To establish the normal appearance of the neonatal brain, 51 neonates, 29-42 weeks postconception, underwent magnetic resonance (MR) imaging with a 0.6-T magnet in a prospective study. T1-weighted images were used to devise stages for the appearance of gray-white matter differentiation and extent of myelination. The results show that from 29 to 42 weeks postconception, changes in gray-white matter differentiation and myelination follow the stages in an orderly and predictable fashion. Changes in white matter intensity appear related to progressive decrease in brain water content. Myelination progresses cephalad from the brain stem at 29 weeks to reach the centrum semiovale by 42 weeks. Delayed myelination, defined as the absence of myelin in the corona radiata by 37 weeks, was seen in nine infants with complicated perinatal courses. Awareness of these developmental features should help to minimize misinterpretation of normal changes in the neonatal brain and lead to earlier detection of pathologic conditions, both with MR imaging and computed tomography.

Brain↗
PubMed1987

Developmental features of the neonatal brain: MR imaging. Part II. Ventricular size and extracerebral space.

Magnetic resonance (MR) imaging with a 0.6-T magnet was performed on 51 neonates, aged 29-42 weeks postconception. In 45 neonates, the ventricular/brain ratio (V/B) at the level of the frontal horns and midbody of the lateral ventricles ranged from 0.26 to 0.34. In six other infants a V/B of 0.36 or greater was associated with either cerebral atrophy or obstructive hydrocephalus. The width of the extracerebral space measured along specified points varied little in the neonatal period and ranged from 0 to 4 mm in 48 infants. Extracerebral space widths of 5-6 mm were seen in three other infants with severe asphyxia. Prominence of the subarachnoid space overlying the posterior parietal lobes is normal in neonates and should not be confused with cerebral atrophy. The authors conclude that V/B ratios of 0.26-0.34 and extracerebral space widths of 0-4 mm represent the normal range, and that neonates whose measurements exceed these values should be followed up.

Brain↗