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Biomedical subjects

A Alavi

Publications and source records attributed to A Alavi.

At least 145 records · Page 8Linked to original sources
PubMed1997

Fluorine-18-FDG evaluation of crossed cerebellar diaschisis in head injury.

UNLABELLED: This study investigates the phenomenon of crossed cerebellar diaschisis in head injury patients. METHODS: We visually compared fluorine-18-fluorodeoxyglucose (FDG)-PET images to radiograph computed tomography or magnetic resonance images in 19 patients with head injury. RESULTS: We found that of 68 focal unilateral lesions, 40% were associated with contralateral cerebellar hypometabolism and 19% were associated with ipsilateral cerebellar hypometabolism. Of supratentorial, extraparenchymal lesions (n = 20), 45% were associated with contralateral cerebellar hypometabolism, whereas 15% had ipsilateral cerebellar hypometabolism. Intraparenchymal lesions were associated with contralateral cerebellar hypometabolism in 38% of the patients and with ipsilateral cerebellar hypometabolism in 21% of the patients. Of the cortical lesions that were the patients' most severe injury, 69% were associated with contralateral cerebellar hypometabolism, whereas only 8% were associated with ipsilateral cerebellar hypometabolism. In patients with focal supratentorial lesions alone, 50% of all focal lesions were associated with contralateral cerebellar hypometabolism and 13% had ipsilateral hypometabolism. Of patients with both focal and diffuse brain injuries, 27% of the focal lesions had contralateral cerebellar hypometabolism and 27% had ipsilateral cerebellar hypometabolism to the most severe focal injury. CONCLUSION: Crossed cerebellar diaschisis is seen more often in patients with focal cortical or extraparenchymal injuries and is not seen in patients with multiple or diffuse brain injuries. Furthermore, this predominance is more pronounced with lesions of the greatest severity.

Adult↗
PubMed1996

Relationships between verbal memory performance and the cerebral distribution of fluorodeoxyglucose in patients with schizophrenia.

Quantitative resting fluorodeoxyglucose-positron emission tomography scans were performed on 42 patients with schizophrenia. Magnetic resonance imaging-based regions of interest were transposed onto the corresponding positron emission tomography images. Region to whole brain ratios were calculated from the mean regional activity per pixel across both hemispheres (left plus right). Laterality scores were calculated from the difference between the mean activity in homotopic regions of the two hemispheres (left minus right). Subjects were tested contemporaneously with the Logical Memory subtest of the Wechsler Memory Scale. The subtest was scored with modified criteria to provide information about verbal recall, perseverations, and other components of verbal memory. Deficits in recall were associated with increased metabolism in selected regions of the left hemisphere that are known to mediate aspects of verbal memory. The findings support hypotheses suggesting that the left hemisphere is functionally overactive in schizophrenia.

Adolescent↗
PubMed1996

Treatment of advanced CNS malignancies with the recombinant adenovirus H5.010RSVTK: a phase I trial.

Primary CNS malignancies are responsible for approximately 12,000 deaths annually in the United States. There has been little change in the outcome for adults with malignant brain tumors over the past few decades, despite improvements in surgical techniques and advances in radiation therapy. These tumors are uniformly fatal one to two years after diagnosis. The morbidity and mortality of this disease arise from the effects of a locally invasive, non-metastasizing lesion. The patients may suffer from seizures, paralysis, incoordination, aphasia, confusion, memory loss, sensory deficits or visual loss, depending on the regions of the brain affected. In addition, they usually require large doses of corticosteroids early and late in their illness, and may experience disabling side effects of this treatment, such as edema, proximal myopathy, diabetes, fungal infections or deep vein thrombosis. Few patients in the older age group are able to work after the diagnosis. Most of the patients are incapable of self-care for several months before death. The localized transfer of new genes into cancer cells potentially permits the expression of proteins with specific biologic functions that may provide a means to alter the biology of tumor growth through a variety of mechanisms including increasing tumor immunogenicity, inducing the local expression of toxic agents, and sensitization of tumors to chemotherapeutic agents. Gene therapy with the transfer of the drug susceptibility gene Herpes virus thymidine kinase (HSV-TK) has shown promise in a number of animal models, including CNS tumors. This study will evaluate the use of adenovirus-mediated transfer of the HSV-TK gene into primary human brain tumors followed by systemic treatment with ganciclovir. The goals of this phase I study are to evaluate the overall safety and efficacy of this treatment and to gain insight into the parameters that may limit the general applicability of this approach. In this phase I study, patients with recurrent gliomas will receive stereotactic-guided injections of the virus into the brain tumor, followed by intravenous ganciclovir for 14 days. Patients eligible to undergo a palliative debulking procedure will receive the same treatment followed by resection on day 7. At the time of resection a second dose of virus will be administered intra-operatively into the residual, unresectable portion of the tumor, and intravenous ganciclovir will be continued for additional 14 days. Tissue removed at the time of resection will be analyzed for evidence of adenovirus infection, thymidine kinase expression and signs of inflammation. The size and metabolic activity of all tumors will be followed by volumetric MRI scans and Position Emission Tomography Scans, respectively. Patients will be enrolled in groups of three, with each group receiving successively larger doses of adenovirus. This study will quantify the toxicity of this therapy, and provide evidence as to the duration of transgene expression and virus induced inflammation.

Adenoviridae Infections↗
PubMed1996

New noninvasive tests for Helicobacter pylori gastritis. Comparison with tissue-based gold standard.

The current gold standard for diagnosing H. pylori gastritis requires antral biopsy for urease test (eg, CLOtest) and/or history. We compared this gold standard to a new low-dose capsule-based 1 microCi [4C]urea breath test (UBT) and a rapid serum test for anti-H. pylori antibodies (FlexSure HP) in 50 consecutive patients undergoing upper endoscopy. Antral biopsies within 3 cm of the pylorus were used for CLOtest and were stained with H&E and thiazine. Slides were reviewed by a single, blinded pathologist (Review) and compared to the pathology department report (Report). A true positive was defined as a positive CLOtest or Review. The prevalence of H. pylori infection by each test was: CLOtest 32%, Review 36%, gold standard 42%, UBT 38%, FlexSure HP 44%, Report 44%. UBT had sensitivity = 90%, specificity = 96%, positive predictive value = 95%, and negative predictive value = 93% and accurately determined H. pylori status in a subgroup of 10 patients who had completed treatment. The one false positive breath test occurred in a patient with 2+ chronic inflammation on biopsy and a positive antibody test. There were two false negative breath tests. Each had both negative CLOtests and negative antibody tests. FlexSure HP had sensitivity = 74%, specificity = 89%, positive predictive value = 88%, and negative predictive value = 77% in patients not previously treated, but had a high false-positive rate in the 10 patients after treatment. Pathology department Report and blinded pathologist Review had only 84% agreement, kappa = 0.67. Both CLOtest and UBT agreed better with Review (86%, 87%, kappa = 0.68, 0.73, respectively) than Report (78%, 77%, kappa = 0.53, 0.53, respectively) suggesting that Review is more accurate than Report. When biopsy is done, we recommend that a CLOtest be performed followed by histological examination if the CLOtest is negative to ensure adequate sensitivity. However, interpretation of histological slides has significant interobserver variability even in experienced hands and may be inaccurate at times. FlexSure HP has good PPV but inadequate sensitivity to rule out active infection and is not useful in patients after treatment. UBT is an excellent noninvasive test that should be considered in cases where EGD is otherwise not indicated.

Antibodies, Bacterial↗
PubMed1996

Stimulating technetium-99m cerebral perfusion studies with a three-dimensional Hoffmann brain phantom: collimator and filter selection in SPECT neuroimaging.

The choice of collimator and the selection of a filter can affect the quality of clinical SPECT images of the brain. The compromises that 4 different collimators make between spatial resolution and sensitivity were studied by imaging a three-dimensional Hoffmann brain phantom. The planar data were acquired with each collimator on a three-headed SPECT system and were reconstructed with both a standard Butterworth filter and a Wiener pre-filter. The reconstructed images were then evaluated by specialists in nuclear medicine and were also quantitatively analyzed with specific regions of interest (ROI) in the brain. All observers preferred the Wiener filter reconstructed images regardless of the collimator used to acquire the planar images. With this filter, the ultrahigh-resolution fan-beam collimator was the most subjectively preferable and quantitatively produced the highest contrast ratios. The findings support suggestions that higher resolution collimators are preferable to higher sensitivity collimators, and indicate that fan-beam collimators are preferable to parallel-hole collimators for clinical SPECT studies of cerebral perfusion. The results also suggest that Wiener filter enhances the quality of SPECT brain images regardless of which collimator is used to acquire the data.

Brain↗
PubMed1996

Cerebral HMPAO SPECT in patients with major depression and healthy volunteers.

1. The authors examined the regional cerebral distribution of [Tc-99m] HMPAO using single photon emission computed tomography (SPECT) in patients with major depression and in healthy controls. 2. 19 patients and 16 healthy controls had SPECT images of the brain acquired with 740 MBq (20 mCl) of [Tc-99m] HMPAO on a triple-headed camera equipped with fan beam collimators. 3. Mean counts per pixel were measured in 13 regions of each hemisphere and compared to the mean activity in the whole brain, the ipsilateral hemisphere, and cerebellum. A "laterality score" was calculated for each structure by subtracting the mean counts per pixel in a region of the right hemisphere from the mean counts in the homotopic region of the left hemisphere and normalizing the difference by the average in both regions. The degree of hemispheric asymmetry was calculated from the absolute values of the laterality scores. 4. The distribution of HMPAO was more variable in patients than in controls; while the mean activity ratios were not significantly different in any region. Asymmetries between homotopic regions of the limbic system were more pronounced in patients than in controls. However, there were no consistent left-to-right asymmetries in either group. 5. The present data indicate that regional cerebral distribution of HMPAO may not be discretely abnormal in depression, but demonstrates heightened variability in depressives (vs. control subjects).

Adult↗
PubMed1996

The relationship between exposed galactose and N-acetylglucosamine residues on IgG in rheumatoid arthritis (RA), juvenile chronic arthritis (JCA) and Sjögren's syndrome (SS).

The relationship between exposed galactose and N-acetylglucosamine on IgG in RA, JCA and SS was investigated. This was achieved using IgG isolated from serum where the levels of galactose and N-acetylglucosamine (GlcNAc) were detected using biotinylated lectins. Galactose and GlcNAc on IgG from patients with RA and JCA are inversely related, but in contrast, in SS, galactose expression on IgG decreased while GlcNAc expression remained similar to normal levels. Alterations in IgG glycosylation are closely associated with the development of adult and juvenile chronic arthritis and SS, but the changes involved are different in RA compared with SS, suggesting that the precise pattern of exposed sugars is associated with different rheumatological diseases.

Acetylglucosamine↗
PubMed1996

Gated resting Tl-201 SPECT in the evaluation of myocardial viability.

Gating of resting Tl-201 SPECT to evaluate myocardial viability is now clinically feasible. Two cases are presented to illustrate the additional information of wall motion and wall thickening obtained from gating. This additional information may improve the classification of viable myocardium and requires further study.

Aged↗
PubMed1996

Comparison of diagnostic performance with ventilation-perfusion lung imaging in different patient populations.

PURPOSE: To determine if patient age, chest radiographic abnormalities, or history of cardiopulmonary disease or venous thromboembolism affected diagnostic performance with ventilation-perfusion (V-P) imaging. MATERIALS AND METHODS: Receiver operating characteristic (ROC) analyses were performed on the final V-P imaging interpretation data obtained during the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study. Diagnostic performance with V-P imaging was not substantially different in patients with varying ages, an abnormal chest radiograph, or a history of venous thromboembolism or cardiopulmonary disease. CONCLUSION: Because diagnostic performance with V-P imaging in detection of pulmonary embolism was similar among the patient populations examined, an abnormal chest radiograph or history of venous thromboembolism or cardiopulmonary disease does not appear to adversely affect overall diagnostic performance in evaluation of acute pulmonary embolism.

Adult↗
PubMed1996

Cerebral blood flow changes in limbic regions induced by unsolvable anagram tasks.

OBJECTIVE: The study addressed the question of whether unsolvable as opposed to solvable cognitive problems activate discrete neuronal systems in the human brain. METHOD: Twelve healthy humans tried to solve unsolvable anagrams. Solvable anagrams and a resting baseline after each anagram task served as control conditions in a within-subject design. Activation was measured with the equilibrium infusion method by using 15O-labeled water and positron emission tomography, with absolute quantitation of anatomically defined regional cerebral blood flow (CBF). RESULTS: Compared to rest, both anagram tasks increased activity in frontal and temporal regions. The soluble task condition increased hippocampal activation and decreased mammillary bodies activity, while unsolvable anagrams were associated with increased CBF to the mamillary bodies and amygdala and decreased hippocampal activity. CONCLUSIONS: A limbic network integrating negative emotion and cognition seems reflected in reciprocal diencephalic and limbic activation with solvable and unsolvable anagrams. Since unsolvable anagrams have been used to induce learned helplessness in humans, this finding may provide an initial step toward clarifying its neural substrate.

Adult↗
PubMed1996

Use of positron emission tomography and evoked potentials in the detection of cortical afferents from the gastrointestinal tract.

OBJECTIVE: Positron emission tomography permits precision identification of the cerebral regions involved in physiologic functions. As the cerebral localization for visceral sensation has not been identified, our aim was to examine the cerebral viscerotopic representation for rectal sensation. METHODS: Cerebral-evoked potentials were measured in five healthy volunteers who underwent rectal balloon distension. Simultaneously, cerebral blood flow was measured using positron emission tomography with 15H2O. RESULTS: A cerebral-evoked potential occurred with rectal balloon distension. An increase in cerebral blood flow was noted in the pre- and postcentral gyrus and the thalamus. CONCLUSION: The techniques for measuring cerebral-evoked potentials and cortical blood flow are useful in the delineation of the cerebral regions subserving visceral sensation.

Brain↗
PubMed1996

Hemodynamic indices of myocardial dysfunction correlate with dipyridamole thallium-201 SPECT.

UNLABELLED: Important differences in hemodynamics and tracer kinetics occur with dipyridamole compared to exercise scintigraphy. To better understand the clinical significance of dipyridamole SPECT 201Tl scintigraphy, we examined the relationships between scintigraphy and clinical, and angiographic and hemodynamic variables in patients with CAD. METHODS: Forty-nine subjects were divided into three study groups. Patients in Groups A (n = 11) and B (n = 20) had a low (<5%) likelihood of CAD. Group A underwent maximal exercise thallium stress testing. Group B underwent thallium dipyridamole scintigraphy. Group C (n = 18) consisted of patients with coronary artery disease who had dipyridamole thallium scintigraphy and cardiac catheterization within 2 wk. Thallium lung-to-myocardial ratio (L/M), left ventricular dilation and perfusion defect site were compared to hemodynamic, clinical and angiographic variables. RESULTS: The Group A L/M ratio of 0.23 +/- 0.05 (mean +/- 1 s.d.) was significantly lower (p < 0.001) compared to the Group B L/M ratio of 0.31 +/- 0.05. In Group C, the UM ratio showed correlation with indices of left ventricular dysfunction including lower resting ejection fraction (p = 0.02, r = 0.83), higher pulmonary capillary wedge pressure (p = 0.01, r = 0.58) and lower cardiac index (p = 0.03, r = 0.54). Left ventricular dilation was associated with hemodynamic changes of ventricular failure including lower resting ejection fraction (p = 0.008, r = 0.88) and higher pulmonary capillary wedge pressure (p = 0.02, r =0.54). Immediate and delayed perfusion defect size showed good correlation with lower resting left ventricular ejection fraction (p = 0.02, r = 0.83, and p = 0.004, r = 0.91, respectively). CONCLUSION: Lung uptake, left ventricular dilation and perfusion defect size show good correlation to hemodynamic indices of resting left ventricular dysfunction. A combination of these factors may be a better predictor of future cardiac events and prognosis.

Cardiac Catheterization↗
PubMed1995

Mood effects on limbic blood flow correlate with emotional self-rating: a PET study with oxygen-15 labeled water.

Positron emission tomography was used to study the effects of experimentally controlled mood states on cerebral blood flow (CBF), measured with the quantitative equilibrium infusion method and 15O-labeled water. Twenty-seven brain regions in each hemisphere were assessed in 16 normal subjects. CBF and heart rate were measured during happy and sad mood induction, and during two nonemotional control conditions: sex differentiation and resting baseline. Valence-specific effects of mood on CBF were obtained for subcortical, but not for frontal-temporal or control regions. CBF increased in left amygdala and decreased in right amygdala during sad mood relative to the averaged control conditions. These changes correlated with shifts toward negative affect. Correlations were opposite for subcortical (negative affect associated with lower left hemispheric CBF) compared with frontal-temporal cortical regions. Results support limbic involvement in regulating emotional states and suggest some reciprocity between subcortical and frontal-temporal regulation of emotional experience.

Adolescent↗