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K R Maravilla

Publications and source records attributed to K R Maravilla.

At least 19 recordsLinked to original sources
PubMed1994

The fornix in patients with seizures caused by unilateral hippocampal sclerosis: detection of unilateral volume loss on MR images.

OBJECTIVE: Because some of the axons of the fornix originate in the pyramidal cells of the hippocampus, we hypothesize that neuronal loss within the hippocampus may result in wallerian degeneration and subsequent atrophy of the ipsilateral fornix. Using high-resolution MR imaging, we evaluated the size of the fornix in patients who had lateralizing partial complex temporal lobe seizures after unilateral hippocampal sclerosis. The expectation is that unilateral forniceal atrophy will provide an additional, objective imaging criterion for determining the side of seizure involvement. MATERIALS AND METHODS: We retrospectively reviewed preoperative MR images of 13 patients with temporal lobe epilepsy who subsequently had unilateral hippocampal sclerosis proved surgically. The images were obtained with specially designed bilateral phased-array coils that permitted high-resolution (512 x 512, 16-cm field of view) T2-weighted fast spin-echo imaging of oblique coronal sections. The width of each rostral crus of the fornix was measured by three neuroradiologists who did not know the patients' history and surgical findings, and consensus measurements were obtained. The side with the smaller fornix was interpreted as abnormal. All 13 patients had lateralizing findings on EEG, unilateral anterior temporal lobectomy, and histologic findings of hippocampal sclerosis. RESULTS: The fornix was smaller on the side of hippocampal sclerosis in 12 (92%) of 13 patients. The percentage of asymmetry between the fornices (smallest/largest x 100) varied from 41% to 82% (mean, 68%). CONCLUSION: Our experience indicates that volume loss in the ipsilateral crus of the fornix can be seen on MR images in patients with unilateral hippocampal sclerosis. The size of the fornices should be analyzed in all patients being examined for temporal lobe epilepsy, as asymmetry in the size of the fornices may reveal the side of hippocampal sclerosis. Such knowledge can assist in the preoperative workup of patients with intractable temporal lobe epilepsy related to hippocampal sclerosis.

Atrophy↗
PubMed1994

MR assessment of radiation-induced blood-brain barrier permeability changes in rat glioma model.

PURPOSE: To assess the potential of a T1-weighted, gadolinium-enhanced MR technique for quantifying radiation-induced changes of blood-brain barrier permeability in a model of stereotactically implanted intracerebral gliomas in rats. METHODS: We calculated the gadolinium blood-to-tissue transport coefficient for gadopentetate dimeglumine from signal intensities in sequential MR images in nine control animals that were not irradiated and in five and three animals that had received 2500 cGy and 1500 cGy whole-brain irradiation, respectively, at 2 days before imaging. RESULTS: The average blood-to-tissue transport coefficient values were 9.76 mL.kg-1.min-1 in the control group, 23.41 mL.kg-1.min-1 in the 2500 cGy group, and 25.63 mL.kg-1.min-1 in the 1500-cGy group. Blood-to-tissue transport coefficients were significantly higher after irradiation, indicating increased radiation-induced blood-brain barrier permeability. Similar increased blood-brain barrier leakiness in brain tumors after high-dose irradiation has been shown by previous nuclear medicine studies using quantitative autoradiography. CONCLUSION: Contrast-enhanced dynamic MR of brain gliomas is a sensitive method to document radiation-induced blood-brain barrier breakdown. Quantitative gadolinium-enhanced MR may become a useful tool for the management of patients with brain tumors undergoing radiation therapy.

Animals↗
PubMed1994

Phase III multicenter trial of high-dose gadoteridol in MR evaluation of brain metastases.

PURPOSE: To assess the efficacy and safety profile of high-dose (0.3 mmol/kg cumulative dose) gadoteridol in patients with suspected central nervous system metastatic disease. METHODS: We studied 67 patients using an incremental-dose technique. Patient monitoring included a medical history, physical examination, vital signs, and extensive laboratory tests within 24 hours before and after the MR examination. Precontrast T1- and T2-weighted spin-echo studies were performed, followed by intravenous injection of 0.1 mmol/kg of gadoteridol. T1-weighted images were acquired immediately after and at 10 and 20 minutes after injection. At 30 minutes an additional 0.2 mmol/kg of gadoteridol was administered (0.3-mmol/kg cumulative dose), and T1-weighted images were acquired. Cases demonstrating abnormal MR findings were assessed for efficacy by unblinded and blinded reviewers and were analyzed quantitatively. RESULTS: Three adverse effects in two patients were considered to be related to gadoteridol administration. No adverse effects were serious; all self-resolved. Forty-nine cases showed abnormal MR findings and were included in the efficacy analysis. A significantly greater number of lesions was seen on the high-dose as opposed to the standard-dose images. Blinded and unblinded readers identified 5 and 8 patients, respectively, with solitary lesions on standard-dose examination and multiple lesions on high-dose examination. Two patients who had normal standard-dose findings had lesions identified on high-dose studies. Quantitative analysis of 133 lesions in 45 patients demonstrated significant increases in lesion signal intensity on high-dose studies when compared with standard-dose studies. CONCLUSION: Gadoteridol can be safely administered up to a cumulative dose of 0.3 mmol/kg. High-dose contrast studies provide improved lesion detectability and additional diagnostic information over studies performed in the same patients with a 0.1-mmol/kg dose and aid in patient diagnosis and treatment. High-dose gadoteridol study may facilitate the care of patients with suspected central nervous system metastasis.

Adolescent↗
PubMed1994

Lesion enhancement in radio-frequency spoiled gradient-echo imaging: theory, experimental evaluation, and clinical implications.

PURPOSE: To investigate the lesser lesion conspicuity after gadolinium contrast infusion with radio-frequency spoiled gradient-echo (SPGR) sequences relative to conventional T1-weighted spin-echo techniques. METHODS: The influences of repetition time, echo time, and flip angle on spin-echo and SPGR signal were studied with mathematical modeling of the image signal amplitude for concentrations of gadopentetate dimeglumine solute from 0 to 10 mM. Predictions of signal strength were verified in vitro by imaging of a doped water phantom. The effects of standard (0.1 mmol/kg) and high-dose (0.3 mmol/kg) gadoteridol on spin-echo and SPGR images were also investigated in three patients. RESULTS: The measured amplitude of undoped water and the rate of increase of doped water signal with increasing gadopentetate concentration (slope) for spin-echo 600/11/1/90 degrees (repetition time/echo time/excitations/flip angle) and SPGR (600/11/190 degrees) were similar and exceeded those of SPGR (35/5/145 degrees). Greater increases in SPGR doped water signal and its slope were produced by increasing TR than by varying echo-time or flip angle. The subjective lesion conspicuity and measured lesion contrast at 0.3 mmol/kg were greater with spin-echo (600/11/1/90 degrees) than with SPGR (35/5/145 degrees) in all three patients; the measured lesion enhancement was similar for both techniques in two patients and decreased for SPGR in the third patient. CONCLUSIONS: The phantom studies suggest that the short repetition time of 35 msec, typically used in clinical SPGR imaging, is largely responsible for a reduced signal amplitude and a diminished rate of increase of signal with increasing gadopentetate concentration, relative to spin-echo. Phantom and clinical studies suggest that the dose of paramagnetic agent required to achieve SPGR lesion conspicuity with short repetition time comparable with spin-echo would have to be higher than the dose in current clinical use.

Brain↗
PubMed1993

Use of the magnetic resonance contrast agent gadodiamide in the central nervous system. Results of a multicenter trial.

To investigate the safety and efficacy of the low-osmolar, nonionic contrast agent, gadodiamide injection (Omniscan, Sanofi Winthrop Pharmaceuticals, New York, NY), for magnetic resonance imaging (MRI) of the head and spine, a multicenter study involving 439 patients was done at 15 centers as part of a Phase II/III clinical trial. Unenhanced MRI scans were obtained after which the patients were injected with 0.1 mmol/kg gadodiamide, and the MRI was repeated. The patients' vital signs were monitored, and laboratory studies were conducted. Neurologic status was examined before and after the study. The images were evaluated for contrast enhancement. No patient had any significant adverse event or serious change in clinical status. Abnormalities were found in 80% (351) of all patients studied, and it was found that, in 75% (266) of these, the postgadodiamide injection images were improved or facilitated visualization of lesions compared with preinjection images. The investigators believe that, based on the results of this study, gadodiamide injection is safe and effective for imaging the head and spine. They suggest that future studies further assess and compare the safety parameters of gadodiamide injection with those of other nonionic and ionic gadolinium ligands.

Central Nervous System Diseases↗
PubMed1992

Uses and limitations of spoiled gradient-refocused imaging in the evaluation of suspected intracranial tumors.

This article describes the use of a radiofrequency-spoiled gradient-recalled (SPGR) imaging pulse sequence in the evaluation of intracranial masses. This pulse sequence provides excellent anatomic detail with T1-weighted image contrast. Rapid, sequential, single-slice (two-dimensional) images of the brain can be obtained in patients who are unable to hold still for long periods of time. In addition, volumetric (three-dimensional) image data sets can be obtained that provide extremely thin (1- to 2-mm) sections of high detail and good signal-to-noise ratio for selected critical structures within the brain. Finally, because SPGR is also utilized for time-of-flight angiography, parenchymal information can be obtained simultaneously with cerebral blood vessel definition. One potential pitfall that the magnetic resonance radiologist must be aware of is the fact that, in many patients, the degree of contrast enhancement is greatly diminished on postgadolinium SPGR images compared with conventional spin-echo T1-weighted images. Comparison with a set of standard spin-echo postcontrast images or, potentially, the use of higher doses of gadolinium may solve this problem. In spite of this limitation, the selective utilization of SPGR imaging can yield additional useful information for evaluation and preoperative planning in patients with intracranial masses.

Brain Neoplasms↗
PubMed1992

Central nervous system manifestations in human immunodeficiency virus infection without AIDS.

To characterize neurological and neuropsychological findings associated with human immunodeficiency virus type-I (HIV) infection, 77 seropositive homosexual or bisexual males with no or minor symptoms of HIV were compared prospectively to 44 HIV seronegative men by observers blinded to serological status of the subjects. Neurological symptoms and examination findings were not significantly different between seropositives and seronegatives except for cranial nerve findings, predominantly mild hearing impairment. Mean performance scores for a 15-test neuropsychological battery were within an unimpaired range for both groups, although for five tests, mean scores were significantly poorer in seropositives. After adjustment for vocabulary score, and demographic and psychosocial variables, the mean score of seropositives was significantly worse only for the Benton Visual Retention Test. Magnetic resonance (MR) images of brain were abnormal in 14 (27%) of 52 seropositives and one of 10 seronegatives (value was not significant). HIV was isolated from cerebrospinal fluid (CSF) in 31 (61%) of 51 seropositives. The only clinical or laboratory difference between CSF culture positives and negatives was a higher CSF immunoglobulin synthesis rate in the former subjects (medians of 10.3 versus 0.1 mg/day; p = 0.03). An additional 13 seropositive subjects had immunologic evidence of central nervous system HIV infection, defined by a serum-to-CSF HIV antibody ratio of less than 5.5. Intracranial abnormalities on MR imaging were associated with CSF immunologic responses to HIV. Nervous system involvement occurred in the vast majority of men with early HIV infection, but clinically significant impairment was uncommon.

Adult↗
PubMed1991

Improved method for in vivo magnetic resonance contrast media research.

This paper describes an approach for contrast media research with which high resolution MR images of rats can be studied before, during, and after intravenous contrast media administration. Using a probe designed to hold up to eight rats, the contrast-enhancing properties in normal rat brains of Gd-DTPA, a low molecular weight compound, and polylysine-(Gd-DTPA), a high molecular weight compound, were compared simultaneously in two groups of four rats each. Signal intensity-time graphs, as measured over various anatomical structures of the normal rat head, demonstrated the feasibility of directly comparing enhancement patterns of two pharmacologically different contrast agents and obtaining relevant data in a single experiment.

Animals↗
PubMed1991

Neuroradiology.

Explore the source record for details and available documents.

Brain Diseases↗
PubMed1991

Multicenter study of gadodiamide injection as a contrast agent in MR imaging of the brain and spine.

To evaluate the safety and efficacy of gadodiamide injection, a nonionic gadolinium chelate complex, in magnetic resonance (MR) imaging of the head and spine, a phase II-III trial was conducted in 439 patients with known or suspected lesions in the central nervous system. All patients received gadodiamide injection in a dosage of 0.1 mmol/kg and were monitored; MR images were evaluated for contrast material enhancement. No serious adverse events or clinically important trends in vital signs, laboratory values, or neurologic status were observed. Gadodiamide injection enhanced or facilitated the visualization of lesions in 266 or 353 patients (75.4%) in whom lesions were shown on unenhanced images, enhanced images, or both; in these 266 patients, the diagnosis was changed in 76 patients (28.6%) and facilitated in 190 patients (71.4%). It is concluded that gadodiamide injection is safe and effective for MR imaging of the head and spine in patients with suspected abnormalities of the central nervous system.

Brain↗
PubMed1989

Prevalence of lumbosacral intervertebral disk abnormalities on MR images in pregnant and asymptomatic nonpregnant women.

The prevalence of lumbosacral intervertebral disk bulge and herniation on sagittal magnetic resonance (MR) images was determined in 45 pregnant subjects and 41 asymptomatic nonpregnant women of childbearing age. MR technique differed for the pregnant and nonpregnant groups. Fifty-three percent of pregnant and 54% of nonpregnant women had an abnormal disk (bulge or herniation) at one or more levels (L3-4, L4-5, or L5-S1). The difference was not statistically significant. There was also no significant difference in the distribution of outcomes among the 45 pregnant subjects, 17 parous nonpregnant women, and 24 nulliparous women. The results suggest that lumbosacral disk bulges or herniations are common in women of childbearing age, whether pregnant or not, and that, contrary to an earlier report, pregnant women do not have an increased prevalence of disk abnormalities.

Adult↗
PubMed1989

Myocutaneous flap failure: early detection with Gd-DTPA-enhanced MR imaging.

Magnetic resonance (MR) imaging was used to evaluate myocutaneous flap viability in an animal model. Bilateral myocutaneous panniculus carnosus groin flaps were created in 14 piglets. Eight of the piglets underwent early occlusion of the vascular pedicle to one flap that resulted in flap failure in all cases. Six piglets underwent late occlusion of the vascular pedicle to one flap that resulted in flap survival in all cases. Spin-echo T1- and T2-weighted MR images were obtained from all piglets 2 and 24 hours after occlusion. Additional gadolinium diethylene-triaminepentaacetic acid (DTPA)-enhanced serial T1-weighted images were obtained in four piglets who underwent early occlusion and in four piglets who underwent late occlusion of the pedicle. The T2-weighted images showed increased signal intensity in both occluded and control flaps and thus did not help predict flap viability. Gd-DTPA-enhanced images enabled accurate prediction of flap viability. The images of early-occluded (non-viable) flaps demonstrated no contrast material enhancement, while both the late-occluded (viable) flaps and the control flaps were contrast enhanced. The authors conclude that Gd-DTPA-enhanced MR imaging can help predict myocutaneous flap viability in piglets.

Animals↗
PubMed1988

Gd DTPA. Clinical efficacy.

Both the diagnostic accuracy and sensitivity of the MRI diagnosis of central nervous system neoplasms appear to be improved by the administration of a paramagnetic contrast agent, Gd DTPA.

Brain Neoplasms↗