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W T Yuh

Publications and source records attributed to W T Yuh.

At least 19 recordsLinked to original sources
PubMed1999

Outcome in acute stroke with successful intra-arterial thrombolysis and predictive value of initial single-photon emission-computed tomography.

This study investigates retrospectively, in selected patients, the ischemic outcome (reversible ischemia, infarction, and hemorrhage) and neurologic outcome of acute stroke treated with intra-arterial thrombolysis and the predictive value of pretreatment single-photon emission-computed tomography (SPECT). Thirty patients with complete recanalization within 12 hours were analyzed. The extent of ischemia was outlined on SPECT, and two CBF parameters were calculated: the ratio of ischemic regional activity to CBF in the cerebellum and the asymmetry index. Reversible ischemia, infarction, and hemorrhage were identified by comparing SPECT and follow-up computed tomography. Nine patients (30%) had no or small infarction, 14 (47%) had medium or large infarction, and seven (23%) had hemorrhage. Forty-two lesions were identified (22 reversible ischemia, 13 infarction, and 7 hemorrhage). Duration of ischemia, urokinase dose, disease type, and occlusion site were nonsignificant factors, whereas neurologic outcome and CBF parameters were significant among the three patient groups and three types of ischemic lesions. Ischemic tissue with CBF greater than 55% of cerebellar flow still may be salvageable, even with treatment initiated 6 hours after onset of symptoms. Ischemic tissue with CBF greater than 35% of cerebellar flow still may be salvageable with early treatment (less than 5 hours). Ischemic tissue with with CBF less than 35% of cerebellar flow may be at risk for hemorrhage within the critical time window. Pretreatment SPECT can provide useful parameters to increase the efficacy of thrombolysis by reducing hemorrhagic complications and improving neurologic outcome.

Adult↗
PubMed1999

Severe occlusive carotid artery disease: hemodynamic assessment by MR perfusion imaging in symptomatic patients.

BACKGROUND AND PURPOSE: Cerebral hemodynamic status has been reported to influence the occurrence and outcome of acute stroke. The purpose of this study was to assess hemodynamic compromise in symptomatic patients with severe occlusive disease of the carotid artery by the use of echo-planar perfusion imaging. METHODS: Spin-echo echo-planar perfusion imaging was performed in 11 patients (two had bilateral disease) with severe stenosis or occlusion of the carotid artery who had experienced either a recent transient ischemic attack or minor stroke. Relative cerebral blood volume (rCBV) maps and relative mean transit time (rMTT) maps were generated from the time-concentration curve. Findings on T2-weighted images, angiograms, rCBV maps, and rMTT maps were compared and assessed qualitatively and quantitatively. RESULTS: Although the abnormalities on T2-weighted images were absent, minimal, and/or unrelated to the degree of stenosis or collateral circulation, rMTT maps showed much larger and more distinct perfusion abnormalities along the vascular distribution of the affected vessels in all 13 vascular territories of the 11 patients. Despite obvious abnormalities on rMTT maps, none of the patients had evidence of decreased rCBV in the affected brain tissue (increased in three, normal in eight). A statistically significant difference in rMTT values was found between the affected and unaffected brain tissue, whereas no significant difference was seen in rCBV values. CONCLUSION: Echo-planar perfusion imaging is a noninvasive and rapid method for evaluating the hemodynamics in severe occlusive carotid artery disease and the compensatory vascular changes, and it may be useful in patient management.

Adult↗
PubMed1998

Prediction of tumor control in patients with cervical cancer: analysis of combined volume and dynamic enhancement pattern by MR imaging.

OBJECTIVE: Quantitative analysis of either tumor volume or dynamic enhancement pattern using MR imaging has been reported as useful in the prediction of response to radiation therapy in cancer of the cervix. Because data for both analyses can be obtained in a single MR examination, the purpose of this study was to evaluate whether combining both analyses can further improve the efficacy of using MR imaging to predict tumor control after radiation therapy. MATERIALS AND METHODS: Twenty patients with bulky carcinomas of the cervix, stages bulky IB (n = 2), IIB (n = 6), IIIA (n = 1), IIIB (n = 9), IVA (n = 1), and recurrent (n = 1), were studied. Initial tumor volumes were calculated by outlining the area of tumor in each slice on T2-weighted images and multiplying by the slice profile. Two dynamic contrast-enhanced MR studies were obtained in each patient immediately before the start of radiation therapy and after 20-22 Gy in 2 weeks of radiation therapy. Dynamic enhancement imaging was performed at 3-sec intervals in the sagittal plane for 120 sec after rapid (9 ml/sec) i.v. injection of MR contrast agent (0.1 mmol/kg of gadoteridol) using a power injector. Time and signal intensity curves reflecting the relative signal intensity of contrast enhancement in the tumor region were generated, and the relative signal intensity of the tumor region during the early plateau phase was calculated. Median follow-up was 25 months (range, 11-35 months). RESULTS: The combined analysis did not improve the prediction rate of local recurrence in small-sized tumors, which responded well to radiation therapy regardless of their dynamic enhancement pattern. However, the combined analysis did improve the prediction rate of local recurrence in intermediate- and large-sized tumors (75% and 80%, respectively) over assessment by either volume analysis (33% and 60%, respectively) or dynamic enhancement pattern analysis (64% and 64%, respectively). The combined analysis was most useful in intermediate-sized tumors (40-99 cm3; 33% recurrence), significantly improving differentiation between high-risk (80% recurrence) and low-risk 10% recurrence) patients (p = .010). CONCLUSION: Our preliminary results suggest that the combined data of both tumor morphologic (volume) and microcirculatory (dynamic enhancement pattern) parameters allow more accurate prediction of local failure in patients with advanced cervical cancer than does each individual parameter alone. Combined data appear to have the greatest potential in patients with intermediate-sized tumors, who constitute most patients (60%) and remain a challenge for outcome prediction and management.

Adenocarcinoma↗
PubMed1998

Contrast dosage in the neuroimaging of brain tumors. Principles and indications.

No single dose of MR contrast agent is optimal or adequate for the evaluation of all types of CNS lesions. This article discusses the fundamental principles and various background suppression techniques for lesion detection and delineation. An understanding of all factors influencing lesion conspicuity is important in deciding the optimal dose, if any, of contrast agent and the technique necessary for the procedure.

Adenoma↗
PubMed1998

Transdural spinal cord herniation: imaging and clinical spectra.

PURPOSE: Transdural herniation of the spinal cord is a rarely reported clinical entity, and many of the existing reports were published before the advent of MR imaging. We describe five current cases and compare them with findings in 25 cases reported in the literature to delineate the clinical and imaging spectra of transdural spinal cord herniation. METHODS: MR imaging, CT myelography, and conventional myelography were performed in five patients with transdural herniation of the spinal cord. These studies, along with clinical findings, are described. Intraoperative photographs are included for one case. The salient features of both the current and previously reported cases are summarized in tabular form. RESULTS: In three cases, transdural spinal cord herniation occurred posttraumatically, in one case the cause was iatrogenic and in the others the herniation occurred spontaneously. Imaging features not previously reported include dorsally directed herniations at thoracolumbar levels (two patients), apparent (lacking surgical confirmation) syringomeyelia (one case), a vertebral body nuclear trail sign (one case), and intramedullary hyperintensities on MR images (two cases). Clinical features not previously reported include unilateral pyramidal-sensory deficits (one case) and isolated unilateral pyramidal signs (one case). Clinical findings similar to previous reports include progressive paraparesis (two cases) and progressive Brown-Séquard syndrome (one case). CONCLUSION: Our five cases illustrate certain clinical and imaging findings not previously reported, and, together with the established features of the 25 cases in the literature, delineate the spectra of transdural spinal cord herniation.

Adult↗
PubMed1997

Tumor size evaluated by pelvic examination compared with 3-D quantitative analysis in the prediction of outcome for cervical cancer.

PURPOSE: Tumor size estimated by pelvic examination (PE) is an important prognostic factor in cervical cancer treated with radiation therapy (RT). Recent histologic correlation studies also showed that magnetic resonance (MR) imaging provides highly accurate measurements of the actual tumor volume. The purpose of this study was to: (a) compare the accuracy of PE and MR in predicting outcome, and (b) correlate tumor measurements by PE versus MR. METHODS AND MATERIALS: Tumor measurements were performed prospectively in 43 patients with advanced cervical cancer. MR and PE were performed at the same time intervals: (a) at the start of RT, (b) after 20-24 Gy/2-2.5 weeks, (c) after 40-50 Gy/4-5 weeks, and (d) at follow-up (1-2 months after RT completion). PE measured tumor diameters in anteroposterior, lateral, and craniocaudal direction, and PE-derived tumor size was computed as maximum diameter, average diameter, and ellipsoid volume. MR-derived tumor size was calculated by summation of the tumor areas in each section and multiplication by the section thickness. Tumor regression during RT was calculated for each method as percentage of initial volume. The measurements were correlated with local failure and disease-free survival. Median follow-up was 29 months (range: 9-56 months). RESULTS: Prediction of local control: Overall, tumor regression rate (rapid versus slow) was more precise than the initial tumor size in the prediction of outcome. MR provided a more accurate and earlier prediction of local control (at 2-2.5 weeks, and at 4-5 weeks of RT) than PE (only at follow-up). Based on the initial tumor size, MR was also better than PE in predicting disease-free survival and local control, particularly in large (> or = 100 cm3) tumors. Size correlation: Tumor size (maximum diameter, average diameter, volume) by PE and MR did not correlate well (r = 0.51, 0.61, and 0.58, respectively). When using MR measurements as a reference, PE tended to overestimate intermediate-size (40-99 cm3) tumors. CONCLUSION: This preliminary study suggests that increased precision of tumor volume measurement leads to more accurate and earlier prediction of outcome in cervical cancer. MR tumor volumetry may be useful as an adjunct to PE in selected cases, and holds the potential to impact therapeutic decision-making.

Adenocarcinoma↗
PubMed1997

Cavum septi pellucidi in normals and patients with schizophrenia as detected by magnetic resonance imaging.

Cavum septi pellucidi (CSP) is a cavity between the two leaflets of the septum pellucidum. CSP is a developmental anomaly, yet the pathologic implications, if any, of an abnormally large CSP remain unclear. The reported incidence of CSP among normal populations varies greatly from 0.15% to 85%. Several studies have suggested that there is a higher incidence of CSP in patients with schizophrenia. We conducted a thin-slice magnetic resonance imaging study to evaluate the prevalence of CSP in a sample of 75 controls and 55 patients. There was a high incidence of small CSP among both groups: 58.8% in the controls and 58.2% in the patients, suggesting that a small cavum could be considered a normal variant; however, the patient group had significantly higher incidence of large CSP (20.7%) compared to the normal group (3%). The patients with large CSP were all male.

Adult↗
PubMed1997

Indication-related dosing for magnetic resonance contrast media.

This presentation reviews the issue of contrast media dosing and imaging protocols for the optimal MR imaging detection and characterization of pathology. The cumulative clinical experience gained in performing contrast-enhanced MR examinations with gadolinium chelates indicates that a dose of 0.1 mmol/kg body weight provides safe and effective enhancement of most CNS pathology. Doses lower than 0.1 mmol/kg have been shown to be inadequate for delineating all but selected types of CNS pathology, such as masses with a high lesion to background ratio on post-contrast images (acoustic neuromas) or lesions located in areas in which the normal tissue very rapidly takes up contrast agent (e. g. microadenomas in the pituitary gland). Recent clinical studies have suggested a role for high dose gadolinium administration (up to 0.3 mmol/kg) for the optimal detection and delineation of cerebral metastases or other small or poorly enhancing lesions. Differences in the histopathologic characteristics (capillary permeability, vascularity, location, size) of specific diseased tissues may require varying doses or even a different contrast agent to be used for optimal imaging results. As new MR contrast agents and new scanning techniques are introduced, the specific diagnostic question posed will likely determine the choice of pulse sequence, contrast agent and dose used.

Contrast Media↗
PubMed1997

MRI in neuro-Behçet's disease.

Our purpose was to characterise specific MRI findings and to determine their value in neuro-Behçet's disease. We examined 17 patients (14 men, 3 women) with neuro-Behçet's disease using T1- and T2-weighted spin-echo images and contrast-enhanced images at 0.5 T. There were 13 patients (76.5%) who had single or multiple lesions. Most of these were in the basal ganglia, brain stem or deep white matter region, giving high signal on T2-weighted images and isointense or low signal on T1-weighted images. In 3 cases (17.6%) there was linear high signal along the posterior limb of the internal capsule on T2-weighted images. This was considered as a potential differentiating feature of neuro-Behçet's disease. Contrast-enhancement was seen in 17 lesions in 7 patients.

Adult↗
PubMed1996

Tumor perfusion studies using fast magnetic resonance imaging technique in advanced cervical cancer: a new noninvasive predictive assay.

PURPOSE: This study investigated sequential changes in tumor blood supply using magnetic resonance (MR) perfusion imaging and assessed their significance in the prediction of outcome of patients with advanced cervical cancer. The purpose of this project was to devise a simple, noninvasive method to predict early signs of treatment failure in advanced cervical cancer treated with conventional radiation therapy. METHODS AND MATERIALS: Sixty-eight MR perfusion studies were performed prospectively in 17 patients with squamous carcinomas (14) and adenocarcinomas (3) of the cervix, Stages bulky IB (1), IIB (5), IIIA (1), IIIB (8), and IVA (1), and recurrent (1). Four sequential studies were obtained in each patient: immediately before radiation therapy (pretherapy), after a dose of 20-22 Gy/ approximately 2 weeks (early therapy), after a dose of 40-45 Gy/ approximately 4-5 weeks (midtherapy), and 4-6 weeks after completion of therapy (follow-up). Perfusion imaging of the tumor was obtained at 3-s intervals in the sagittal plane. A bolus of 0.1 mmol/kg of MR contrast material (gadoteridol) was injected intravenously 30 s after beginning image acquisition at a rate of 9 ml/s using a power injector. Time/signal-intensity curves to reflect the onset, slope, and relative signal intensity (rSI) of contrast enhancement in the tumor region were generated. Median follow-up was 8 months (range 3-18 months). RESULTS: Tumors with a higher tissue perfusion (rSI > or = 2.8) in the pretherapy and early therapy (20-22 Gy) studies had a lower incidence of local recurrence than those with a rSI of < 2.8, but this was not statistically significant (13% vs. 67%; p = 0.05). An increase in tumor perfusion early during therapy (20-22 Gy), particularly to an rSI of > or = 2.8, was the strongest predictor of local recurrence (0% vs. 78%; p = 0.002). However, pelvic examination during early therapy (20-22 Gy) commonly showed no appreciable tumor regression. The slope of the time/signal-intensity curve obtained before and during radiation therapy also correlated with local recurrence. Follow-up perfusion studies did not provide information to predict recurrence. CONCLUSION: These preliminary results suggest that two simple MR perfusion studies before and early in therapy can offer important information on treatment outcome within the first 2 weeks of radiation therapy before response is evident by clinical examination. High tumor perfusion before therapy and increasing or persistent high perfusion early during the course of therapy appear to be favorable signs. High perfusion suggests a high blood and oxygen supply to the tumor. The increase in tumor perfusion seen in some patients early during radiation therapy suggests improved oxygenation of previously hypoxic cells following early cell kill. Radiation therapy is more effective in eradicating these tumors, resulting in improved local control. Our technique may be helpful in identifying early-while more aggressive therapy can still be implemented-those patients who respond poorly to conventional radiation therapy.

Adenocarcinoma↗
PubMed1996

Anatomic distribution of metastases in the vertebral body and modes of hematogenous spread.

STUDY DESIGN: A retrospective review of the magnetic resonance spine examinations of 49 patients with metastatic bone disease to the spine was performed. OBJECTIVES: To determine whether the pattern of metastatic distribution in the spine correlates with the type of primary tumor and theoretical mode of hematogenous spread by arterial or venous routes. SUMMARY OF BACKGROUND DATA: In 1940, Batson theorized a venous plexus route by which tumors spread to the spine from pelvic tumors such as prostatic carcinoma. It this theory is true, the venous vascular anatomy of the spine would result in metastases being deposited in the central or posterior vertebral body, whereas arterial deposits would occur near the end-plates. METHODS: Each vertebral body was divided into 27 equal cells in the magnetic resonance images; the central and posterior cells in the midsagittal view were defined as central, and the other cells were defined as peripheral. The primary tumor was assigned to either the arterial or venous group based on Batson's proposed mode of spread. The average number of lesions per involved vertebral body in the central and peripheral regions was calculated. RESULTS: There was no statistically significant correlation between tumors with proposed arterial/venous routes of metastasis and central/peripheral location of metastatic deposits. CONCLUSION: The mechanism by which tumors spread to the vertebral body may not be via a pure arterial or venous route. Other mechanisms such as tissue specificity, cascade system, and closed loop circulation system may be involved.

Adolescent↗
PubMed1996

Usefulness of tumor volumetry by magnetic resonance imaging in assessing response to radiation therapy in carcinoma of the uterine cervix.

PURPOSE: Clinical evaluation of tumor size in cervical cancer is often difficult, and clinical signs of radiation therapy failure may not be present until well after completion of treatment. The purpose of this study is to investigate early indicators of treatment response using magnetic resonance (MR) imaging for quantitative assessment of tumor volume and tumor regression rate before, during, and after radiation therapy. METHODS AND MATERIALS: Thirty-four patients with cervical cancer Stages IB [5], IIB [8], IIIA [1], IIIB [14], IVA [3], IVB [1], and recurrent [2] were studied prospectively with four serial MR examinations obtained at the start of radiation therapy, at 2-2.5 weeks (20-24 Gy), at 4-5 weeks (40-50 Gy), and 1-2 months after treatment completion. Tumor volume was assessed by three-dimensional volumetric measurements using T2-weighted images of each MR examination. The volume regression rate was generated based on the four sequential MR studies. These findings were correlated with local control, metastasis rate, and disease-free survival. Median follow-up was 18 months (range: 9-43 months). RESULTS: The tumor regression rate after a dose of 40-50 Gy correlated significantly with treatment outcome. The actuarial 2-year disease-free survival was 88.4% in patients with tumors regressing to < 20% of the initial volume compared with 45.4% in those with > or = 20% residual (p = 0.007). The incidence of local recurrence was 9.5% (2 out of 21) and 76.9% (10 out of 13), respectively (p < 0.001). Analysis by initial tumor volume showed that this observation was valid in patients with initial volumes between 40 and 100 cm3. Analysis by FIGO stage confirmed this observation in all patients except those with Stage IB. CONCLUSION: Sequential tumor volumetry using MR imaging appears to be a sensitive measure of the responsiveness of cervical cancer to irradiation. Treatment response can be assessed as early as during the course of radiation therapy by measurement of initial tumor volume and regression rate at 40-50 Gy. In patients with large (> 40 cm3) and advanced (Stage > or = IIIA) tumors, this technique may be helpful in supplementing the clinical examination for response assessment. The identification of patients at high risk for treatment failure may ultimately lead to improved clinical outcome.

Adult↗
PubMed1996

MRI of brucella polyneuritis in a child.

MRI of a rare case of polyneuritis following brucellosis is presented. An 8-year-old boy with a history of brucellosis showed marked enlargement of the origin of the left fifth cranial nerve and contrast enhancement of the fifth cranial nerves and the Gasserian ganglion in Meckel's caves. A well-defined low-signal cystic mass showing peripheral contrast enhancement lay anteromedial to the left seventh and eighth cranial nerves. The seventh and eighth nerves showed marked enhancement. The prechiasmatic portion of the right optic nerve showed fusiform enlargement with marked contrast enhancement of the nerve and right optic tract. MRI immediately after treatment showed no enhancement of the cranial nerves. Enlargement of the origin of the left fifth cranial nerve persisted, but there was no enlargement of the optic nerve. The mass near the left seventh and eighth cranial nerves was still present with no obvious morphological change, but no longer showed peripheral enhancement.

Brucellosis↗
PubMed1996

Magnetic resonance imaging used to assess patients with trigeminal neuralgia.

To assess the value of magnetic resonance imaging in the evaluation of trigeminal neuralgia, 51 patients were studied by magnetic resonance imaging after a trigeminal protocol. Clinical and magnetic resonance imaging results were correlated. Seventeen (33%) nonvascular abnormalities and 27 (53%) vascular contacts or compressions of the trigeminal nerve were demonstrated. Of the patients younger than of 29 and 39 years of age, 100% and 45%, respectively, had a tumor or multiple sclerosis compared with 20% and 18% of those older than 40 and 60 years of age, respectively. One third of the patients with pain in more than one branch of the trigeminal nerve had tumors. On the basis of this study, magnetic resonance imaging may be useful in discovering underlying pathoses associated with trigeminal neuralgia if patients have failed to respond to an initial conservative treatment. The patients most likely to exhibit significant magnetic imaging resonance findings are young and with pain in more than one trigeminal branch.

Adolescent↗
PubMed1996

Echo-planar FLAIR imaging in evaluation of intracranial lesions.

Fluid-attenuated inversion-recovery (FLAIR) imaging is a magnetic resonance imaging technique that improves lesion detection in the brain. This technique suppresses signal from free water in cerebrospinal fluid and maintains the hyperintense lesion contrast of T2-weighted spin-echo imaging. Unfortunately, conventional FLAIR imaging requires a long acquisition time and provides a limited number of sections. A combination of echo-planar imaging and FLAIR imaging offers the image contrast effects of FLAIR imaging and the speed of echo-planar imaging. Clinically, the echo-planar FLAIR technique is most helpful in detecting subtle, early lesions that do not enhance, such as early infarct, demyelinating disease, early infection, and trauma. The increased magnetic susceptibility effect associated with the echo-planar technique can be clinically useful in detecting subtle hemorrhage and cavernous angioma. Echo-planar FLAIR imaging is a practical and efficient means of screening the entire brain in a short time.

Brain Diseases↗
PubMed1996

Neuroradiology.

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Humans↗