Biomedical subjects
Publications and source records attributed to W T Yuh.
The etiology and types of intracranial vasculitis are described, along with a neuroimaging-oriented classification system. Specific entities are discussed in detail. The role of various modalities is defined, as well as a practical approach to diagnosis.
PURPOSE: To examine the effects of different gadolinium doses on the delineation of gliomas, particularly the demonstration of abnormal enhancement on T1-weighted images extending beyond the zone of apparent signal abnormality on corresponding T2-weighted images. METHODS: During phase II clinical trials of gadoteridol, 23 patients with pathologically proved gliomas were studied by MR with various doses of gadoteridol, ranging from 0.05 to 0.3 mmol/kg. RESULTS: All of the gliomas were readily detected by T2-weighted images. Twelve of 23 patients demonstrated enhancement on T1-weighted images extending beyond the zone of apparent signal abnormality demonstrated on T2-weighted images. These findings were seen in none of the six patients (0%) studied at 0.05 mmol/kg, one of five patients (20%) studied at 0.1 mmol/kg, four of five patients (80%) studied at 0.2 mmol/kg, and seven of seven patients (100%) studied at 0.3 mmol/kg. CONCLUSIONS: The detection of symptomatic gliomas does not require a contrast agent because they are generally large and readily demonstrated on T2-weighted images. However, the area of postcontrast enhancement of gliomas seems to be greater with higher doses of contrast agent. The cause of the abnormal enhancement extending beyond the zone of apparent signal abnormality on T2-weighted images seen in this limited study is unknown and probably represents tumor infiltration. The frequency of detection of such findings appears to be proportional to the dose of contrast material used.
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.
PURPOSE: To investigate the cost-effectiveness of high-dose MR contrast studies in the management of brain metastases. METHODS: During the phase III clinical trial of high-dose contrast studies (0.3 mmol/kg), 11 of 27 patients were judged by the reviewers to have potential treatment changes based on the additional information provided by the high-dose studies. We retrospectively evaluated how many of these 27 patients had actual treatment changes because of the results of the high-dose study. Using the fee schedule at our institution, the cost-effectiveness was analyzed based on the cost savings from treatment changes and the additional expense of implementing the high-dose studies. RESULTS: A total of 3 craniotomies ($22,800 each) and 2 aggressive courses of radiation therapy ($1122 each) were avoided in 4 patients because of the additional lesions detected by the high-dose studies. This resulted in a treatment cost savings of $70,644. The extra expense for implementing the high-dose study is $9126 for a single injection in all 27 patients, $9295 for 2 separate injections completed in 1 visit in the 11 patients, and $11,154 for 2 separate injections completed in 2 separate visits. The cost savings in management (diagnosis and treatment) therefore ranged from $59,490 to $61,518 for all patients and from $2203 to $2278 per patient. CONCLUSION: Based on our limited data, the high-dose study seems to impact positively on the cost-effectiveness in the management of brain metastases. However, because our study had limitations, our results need to be confirmed with a larger patient population and a more standardized treatment approach and fee schedule.
Many factors affect the ability to detect a CNS lesion. There is no single contrast dose that is optimal for all diseases. By understanding these factors that may affect lesion detection, the appropriate dose for specific pathologic processes may be determined.
PURPOSE: To measure and evaluate the temporal enhancement characteristics of the normal pituitary gland and pituitary adenoma. METHODS: Thirty healthy subjects and 10 patients with sellar pituitary adenomas were studied prospectively using dynamic MR imaging with a 5- or 10-sec temporal resolution during a bolus injection of gadolinium. RESULTS: Qualitative visual analysis demonstrated a consistent sequential pattern of pituitary enhancement in which the posterior lobe enhanced earlier than the anterior lobe by approximately 35 sec. Quantitative analysis revealed that posterior lobe enhancement occurred 9.8 +/- 1.5 sec (mean +/- SEM) before the anterior lobe in healthy subjects, whereas tumor enhancement occurred significantly before the anterior lobe but only slightly before the posterior lobe in patients with adenomas. CONCLUSION: The sequential enhancement pattern of the normal pituitary gland was found to be consistent with its vascular anatomy. In contrast to previous reports, pituitary adenomas were found to enhance earlier than the anterior lobe. These results suggest that pituitary adenomas have a direct arterial blood supply, similar to that of the posterior pituitary lobe.
PURPOSE: To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. METHOD: Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 microns, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L/min per m2. RESULTS: The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. CONCLUSION: Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass.
PURPOSE: To study MR patterns of venous sinus occlusive disease and to relate them to the underlying pathophysiology by comparing the appearance and pathophysiologic features of venous sinus occlusive disease with those of arterial ischemic disease. METHODS: The clinical data and MR examinations of 26 patients with venous sinus occlusive disease were retrospectively reviewed with special attention to mass effect, hemorrhage, and T2-weighted image abnormalities as well as to abnormal parenchymal, venous, or arterial enhancement after intravenous gadopentetate dimeglumine administration. Follow-up studies when available were evaluated for atrophy, infarction, chronic mass effect, and hemorrhage. RESULTS: Mass effect was present in 25 of 26 patients. Eleven of the 26 had mass effect without abnormal signal on T2-weighted images. Fifteen patients had abnormal signal on T2-weighted images, but this was much less extensive than the degree of brain swelling in all cases. No patient showed abnormal parenchymal or arterial enhancement. Abnormal venous enhancement was seen in 10 of 13 patients who had contrast-enhanced studies. Intraparenchymal hemorrhage was seen in nine patients with high signal on T2-weighted images predominantly peripheral to the hematoma in eight. Three overall MR patterns were observed in acute sinus thrombosis: 1) mass effect without associated abnormal signal on T2-weighted images, 2) mass effect with associated abnormal signal on T2-weighted images and/or ventricular dilatation that may be reversible, and 3) intraparenchymal hematoma with surrounding edema. CONCLUSION: MR findings of venous sinus occlusive disease are different from those of arterial ischemia and may reflect different underlying pathophysiology. In venous sinus occlusive disease, the breakdown of the blood-brain barrier (vasogenic edema and abnormal parenchymal enhancement) does not always occur, and brain swelling can persist up to 2 years with or without abnormal signal on T2-weighted images. Abnormal signal on T2-weighted images may be reversible and does not always indicate infarction.
PURPOSE: To describe our experience with MR and angiography in diagnosing intracranial vasculitis and to test the hypothesis that MR can be used to screen for patients unlikely to have vasculitis. METHODS: Ninety-two patients who had angiography with "exclude vasculitis" as the indication or who had angiography and a clinical diagnosis of vasculitis were identified. Angiograms of all 92 patients and the MRs of the 70 patients who had both studies were reviewed. RESULTS: Eleven patients had intracranial vasculitis. Angiography showed characteristic changes in 8. MR, performed in 9 of 11 vasculitis cases, was significantly abnormal in all 9. Among 70 patients who had both studies, 19 had MR that was completely normal or showed only incidental findings. None of these 19 was diagnosed with vasculitis. The diagnostic yield of angiography performed to exclude vasculitis was only 6%. CONCLUSIONS: Evaluation for intracranial vasculitis should include MR. A negative MR excludes intracranial vasculitis more definitively than does a negative angiogram and makes the likelihood of finding vasculitis with angiography negligible.
PURPOSE: To investigate whether MR can provide additional information on fetuses with central nervous system abnormalities as demonstrated by ultrasonography. METHODS: Fetal MR examinations were studied prospectively in 22 pregnant women whose fetuses showed evidence of anomalies on ultrasound performed in the High-Risk Obstetric Clinic. RESULTS: In 19 of 22 cases, postpartum confirmatory diagnoses were obtained by MR or CT examinations, autopsy, or surgery. In general, the image quality of MR is comparable with that of ultrasound. However, in six of 22 cases (27%), MR provided additional information that altered the ultrasound diagnosis; these included cases of infarction, diastematomyelia, normal hemimegalencephaly with early myelination, Dandy-Walker variant, and lipoma. All of these cases had postpartum confirmation. The additional information changed the treatment in three of six patients (no intervention or elective abortion). CONCLUSIONS: In certain situations MR can add valuable information to that obtained by sonography in the evaluation of the fetal central nervous system.
The efficacy of gadopentetate dimeglumine (Gd-DTPA) enhanced magnetic resonance (MR) imaging in the diagnosis and differentiation of soft-tissue, neoplastic and non-neoplastic lesion has not been well established. Thirty patients with soft tissue masses (18 neoplastic and 12 non-neoplastic) were studied, using MR imaging with and without administration of Gd-DTPA. Gd-DTPA proved helpful in characterisation of several entities, including differentiation of solid mass from proteinaceous cyst, demonstration of tumour nodules within haemorrhagic or necrotic masses, and delineation of tumour adjacent to oedema. The use of Gd-DTPA may provide additional information for tissue specificity and, in complicated cases, Gd-DTPA may also provide essential information that cannot be obtained using other methods. We recommend the use of contrast enhanced MR as an adjunct to conventional MR imaging in the initial assessment of musculoskeletal soft tissue masses. However, T2-weighted images show better tissue contrast of the lesions, and are equal to contrast enhanced images in delineation of tumour margins. Non-contrast enhanced images are, therefore, probably adequate for the delineation of lesions for surgical planning when a diagnosis has already been made.
PURPOSE: To evaluate magnetic resonance (MR) imaging in the planning of radiation therapy for patients with cervical cancer. MATERIALS AND METHODS: MR imaging was performed in 15 patients with predominantly advanced cervical carcinomas. Skin markings of the radiation ports were labeled with MR-detectable tubing and beads to assess the adequacy of port placement. Volume and extent of tumor at MR imaging were compared with those at physical and computed tomographic (CT) examinations. RESULTS: Tumor involvement of normal structures (parametrium, vagina, endometrium) was more extensive at MR imaging than at clinical examination in six patients (40%) and at CT in five patients (33%), resulting in modification of the radiation fields in eight patients (53%). Tumor size was larger on MR images than at clinical examination in 11 patients (73%). CONCLUSION: MR imaging can depict tumor volume and better delineate the extent of involvement than physical and CT examination. This can be useful for placement of radiation ports, especially when small boost fields are used.
OBJECTIVE: This study was designed to evaluate the relation between intelligence and a variety of measures of brain structure. METHOD: Magnetic resonance imaging scans were used to measure the volume of the intracranial cavity, cerebral hemispheres, lateral ventricles, temporal lobes, hippocampus, caudate, and cerebellum, as well as the overall volume of gray matter, white matter, and CSF, in 67 healthy, normal volunteers. Intelligence was measured with the Wechsler Adult Intelligence Scale--Revised. RESULTS: Full-scale IQ was found to be significantly correlated with intracranial, cerebral, temporal lobe, hippocampal, and cerebellar volume but not with caudate and lateral ventricle volume. There were also significant correlations of full-scale, verbal, and performance IQ with overall gray matter volume but not with white matter or CSF volume. Gender differences were noted in the pattern and number of correlations between the volume of the brain and its subregions and full-scale, verbal, and performance IQ. CONCLUSIONS: The results suggest that the size of some cerebral structures may account for a significant, but modest, proportion of the variance in human intelligence.
BRAINBLAST, a program that uses voxel processing, was developed in order to produce high-fidelity three-dimensional reconstructions of the brain. Four steps were used to produce images: washing away cerebrospinal fluid (via histogramming), dissecting away the blood vessels (via a connectivity heuristic), highlighting the sulci and gyri (via a lighting model), and resampling the interior contents of the brain. After reconstruction, the images can be resampled, rotated, written on, measured, or redissected. The technique has a variety of applications: study of individual variation in sulcal and gyral patterns, evaluation of structure/function relationships, measurement of volumes or subregions using anatomically defined landmarks, and teaching of neuroanatomy.
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Magnetic resonance imaging is frequently used for visualization of soft tissues of the head and neck. It was the purpose of this study to determine whether gold eyelid weights, used for treatment of lagophthalmos in facial palsy, would be deflected at high magnetic strengths during imaging. Ex vivo study of six incrementally increasing weights at two magnetic strengths was performed. There was no deflection of any of the gold eyelid loads at either 0.5-tesla or 1.5-tesla magnetic strengths. We conclude that patients with gold eyelid weights are not at risk of damage from movement of the prostheses during magnetic resonance imaging examination.
Volumetric measurements of subcortical and temporal structures were done on a sample of 54 schizophrenic patients, who were compared with 48 bipolar patients and 47 normal controls. We observed the male schizophrenic patients to have significant enlargement in the putamen and lesser enlargement in the caudate. We found the right temporal lobe to be larger than the left across all diagnostic groups, although bipolar females failed to have this asymmetry. We did not replicate the finding of decreased hippocampal, amygdala, or temporal lobe volume in our schizophrenic patients. Nor did we find significant differences between our bipolar patients and controls in the structures measured, with the exception of the right hippocampus. Our findings are consistent with a developmental defect in pruning of subcortical brain regions or with a compensatory synaptic increase secondary to decreased input from other brain regions such as the prefrontal cortex or anterior temporal lobe structures. Coupled with the lack of temporal lobe asymmetry in bipolar females, these findings suggest that different types of gender-specific neurodevelopmental abnormalities may occur in affective versus schizophrenic psychosis, which may reflect the effects of hormonal influences on brain development in predisposed individuals.