Search PubMed⌕ Search

Biomedical subjects

F Fazio

Publications and source records attributed to F Fazio.

At least 199 records · Page 11Linked to original sources
PubMed1993

Time dependence of residual tissue viability after myocardial infarction assessed by [18F]fluorodeoxyglucose and positron emission tomography.

Areas of myocardial infarction may retain glycolytic activity and this finding is indicative of tissue viability and predictive of functional recovery after revascularization. In order to assess the relation between the time elapsed from the occurrence of acute myocardial infarction and persistence of myocardial metabolic activity in the infarcted tissue, we prospectively studied 65 patients with previous myocardial infarction diagnosed clinically and by electrocardiographic (Q wave) and enzymatic criteria. All patients underwent coronary angiography and contrast left ventriculography, evaluation of regional myocardial glucose metabolism (in the fasting state) by positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), and assessment of myocardial perfusion by single photon emission computed tomography (SPECT) with technetium-99m methoxyisobutyl isonitrile (99mTc-MIBI). Based on the regional metabolic and perfusion findings, patients were divided into 2 groups, depending on the absence (group 1, 26 patients) or presence (group 2, 39 patients) of [18F]FDG uptake in the underperfused regions. Areas of underperfusion at rest, consistent with the clinically identified myocardial infarction site, were observed in all patients. Severity of coronary artery disease, presence of collaterals, number of hypocontractile segments, and wall motion score did not differ significantly in the 2 groups. The time elapsed from the infarction was significantly greater (1,860 +/- 1,333 days) in group 1 than in group 2 (92 +/- 115 days; p < 0.0001). Exercise caused an increase in severity and/or extent of resting perfusion abnormalities in a greater proportion of patients of group 1 (53% vs 23%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Activation of precentral and mesial motor areas during the execution of elementary proximal and distal arm movements: a PET study.

Regional cerebral blood flow was measured using positron emission tomography (PET) in normal subjects while performing simple aimless proximal and distal arm movements. The aim of the experiment was to compare the somatotopic organization of precentral and mesial (the so called supplementary motor area, SMA) motor cortices and to evaluate whether in man, as in the monkey, the rostral and caudal sectors of SMA are functionally different. The results showed that proximal and distal arm movements are to a large extent segregated in the precentral motor cortex, but not in the SMA. They also showed that the SMA is made of at least two functional sectors. Only the caudal one is activated during simple aimless movements.

Adult↗
PubMed1993

Left and right hemisphere contribution to recovery from neglect after right hemisphere damage--an [18F]FDG pet study of two cases.

A 2-[18F]-Fluoro-2-Deoxy-D-Glucose ([18F]FDG) and positron emission tomography (PET) study was performed in the acute and chronic phase of stroke in one patient with unilateral neglect due to a right hemispheric lesion. In the acute phase, severe neglect, as well as hypometabolism in both the right and in the left unaffected cerebral hemisphere, was demonstrated. At follow-up evaluation the patient showed an almost complete recovery from unilateral neglect. This was associated with a return of left hemisphere metabolism to normal values and partial metabolic recovery in the right hemisphere, where frontal and parietal areas remained functionally impaired. Another patient with an extensive right cerebral ischaemic lesion on CT and severe unilateral neglect was studied by PET in chronic phase. A severe metabolic depression in the left unaffected hemisphere and in the right cerebral areas spared by the lesion, was found. These data suggest that the remission of unilateral neglect might be associated to a functional metabolic recovery in both the undamaged left hemisphere and the unaffected regions of the right hemisphere.

Aged↗
PubMed1993

SPET imaging of cerebral perfusion in patients with non-refractory temporal lobe epilepsy.

The pattern of regional cerebral blood flow was assessed by single photon emission tomography and (99mTc)HM-PAO in 28 patients with clinical diagnosis of non-refractory cryptogenic temporal lobe epilepsy on chronic treatment with carbamazepine. Each patient underwent a magnetic resonance imaging study of the brain. An EEG was performed concurrently with the assessment of cerebral blood flow. Areas of focal hypoperfusion were observed in 8/28 patients, and a concurrent EEG focus was identified in 10/28 patients. Areas of hypoperfusion and the EEG foci were consistent in 6 of the 10 patients with EEG abnormalities; in 2 patients hypoperfusion and the EEG abnormalities were on opposite sides, though in homologous areas; in 2 patients the perfusion pattern was normal in spite of the EEG abnormalities. The number of clinical seizures and EEG abnormalities was higher for the patients presenting with cerebral hypoperfusion than for those with normal perfusion. It is concluded that the evaluation of cerebral blood flow may provide useful information for both diagnostic and prognostic assessment of these patients.

Adult↗
PubMed1993

Crossed aphasia: a PET follow up study of two cases.

Two cases of aphasia after right hemispheric stroke in right handed patients are described. The first patient had a severe mixed transcortical aphasia, apraxia and neglect after a lesion involving the right lenticular nucleus and periventricular white matter; aphasia was still present after three months. The second patient had a mild, transient fluent aphasia after a small right hemispheric periventricular lesion. Studies with [18F]FDG and positron emission tomography (PET) showed functional depression extending to the structurally unaffected left hemisphere in both patients in the acute stage. After three months, in the patient with persistent aphasia, metabolism was still reduced in the right hemisphere, with some recovery of hypometabolism on the left, while metabolic values had returned to normal in the patient with full language recovery. A close parallelism between glucose metabolism and clinical course in crossed aphasia is shown, as well as the presence of a functional involvement of the structurally unaffected left hemisphere in the acute stage.

Aged↗
PubMed1993

[18F]FDG PET in fatal familial insomnia: the functional effects of thalamic lesions.

We used [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) to study regional cerebral glucose utilization (rCMRglc) in four patients with fatal familial insomnia (FFI), a prion disease with a mutation at codon 178 of the prion protein gene. Two patients, presenting only with insomnia and dysautonomia, had a prominent and, in one case, selective thalamic hypometabolism. The remaining two cases presented a more complex clinical picture with multiple neurologic deficits, with both thalamic and widespread brain hypometabolism involving the majority of cortical structures, basal ganglia, and the cerebellum. This widespread pattern was present in the early stage of the disease and showed significant worsening as the disease progressed in one patient examined twice. The thalamic hypometabolism, consistently found with PET in FFI patients, is in agreement with the neuropathologic findings and is a hallmark of the disease.

Adult↗
PubMed1993

Three-step tumor pre-targeting in lung cancer immunoscintigraphy.

Radiolabelled MoAbs have been used in both the diagnosis and the treatment of a variety of tumors. Recently, a three-step tumor pre-targeting strategy has been proposed to overcome one of the major limiting factors in radioimmunodetection: the low tumor-to-background ratio. We evaluated this pre-targeting protocol in 10 patients diagnosed as having pulmonary carcinoma. One milligram of biotinylated anti-CEA MoAb (FO23C5) was administered i.v. (1st step); 24 hours later 5 mg of avidin was injected i.v. (2nd step) followed by 100-500 ng of 111In-biotin (5 mCi) the day after (3rd step). Imaging was performed using single photon emission tomography (SPET). No toxicity and no adverse reactions were observed. Tumor was detected in 8 out of 10 patients. Mediastinal metastases were also localised in 2 out of 3 patients, and adrenal gland recurrency in 1 out of 2 patients. The tumor/background (normal lung), heart, liver and spine ratios were respectively 2.0, 1.0, 1.3 and 4.1 at 90 minutes post-injection. These preliminary data show that the three-step pretargeting method is safe and allows SPECT tumor localization soon after the injection of the radiolabel. In the future, the use of MoAbs with higher specificity could result in improved tumor-targeting, and in the possibility of lung cancer radioimmunotherapy.

Aged↗
PubMed1993

Comparability of FDG PET studies in probable Alzheimer's disease.

Results of studies with positron emission tomography (PET) of 18F-2-fluoro-2-deoxy-D-glucose (FDG) in patients with probable Alzheimer's disease (AD) were compared among three European centers with different PET scanners (in-plane resolution ranging between 6.75 mm and 9.2 mm). A ratio of glucose metabolism in the most typically affected regions over the least typically affected regions was calculated to quantitatively analyze the characteristic pattern of AD. Diagnostic accuracy of this composite ratio was high (95.8%) and was superior to that of most ratios derived from single regions. Correspondingly, there was a consistent, highly significant difference between patients (mean ratio 0.77 +/- 0.11) and normals (mean 0.99 +/- 0.04) without significant differences among laboratories. Possible small effects of rate constant variation and region size were analyzed by computer simulation. The results demonstrate that a common investigation protocol may yield FDG PET data in different laboratories that are closely comparable in spite of differences between scanners and imaging equipment.

Aged↗
PubMed1993

A procedure for patient repositioning and compensation for misalignment between transmission and emission data in PET heart studies.

A procedure for patient repositioning and compensation for misalignment between transmission and emission data in positron emission tomography (PET) heart studies has been developed. Following the transmission scan (TR1), patients are moved from the scanner bed for the administration of the tracer, and repositioned when ready for the emission scan (EM1). A short postinjection transmission scan (TR2) is performed at the end of the EM1 study. TR1 and TR2 images are compared to recognize misalignment between transmission and emission studies. TR1 sinograms are compensated for misalignment to allow for a proper attenuation correction. The procedure has been tested on phantom and [18F]FDG PET heart studies. Misalignments down to 2.5 mm translation and 1 degree rotation in the transaxial plane and 4 mm in the axial direction can be recognized and compensated for. The procedure is suitable for clinical purposes, allowing reduction of patient time on the scanner bed, increased patient comfort and significant increase of patient throughput.

Deoxyglucose↗
PubMed1993

Measurement of regional cerebral glucose utilization with fluorine-18-FDG and PET in heterogeneous tissues: theoretical considerations and practical procedure.

Functional tissue heterogeneity, i.e., inclusion of tissues with different rates of blood flow and metabolism within a single region of interest, is an unavoidable problem with PET. Errors in determination of regional cerebral glucose utilization (rCMRglc) with [18F]FDG have resulted from the currently used simplifying assumption that all regions examined are homogeneous. We have established an optimal, yet practical procedure to minimize errors due to tissue heterogeneity in determination of rCMRglc. Effects of applying the three-rate constant kinetic model designed for homogeneous tissues with both dynamic and single-scan procedures and the Patlak plot were evaluated in normal subjects in experimental periods up to 120 min following tracer injection. The procedure with a single scan carried out any time within the interval between 60 and 120 min following tracer injection, combined with population average rate constants determined over a 120-min period, was found to be optimal for quantitative rCMRglc studies.

Adult↗
PubMed1992

Errors introduced by tissue heterogeneity in estimation of local cerebral glucose utilization with current kinetic models of the [18F]fluorodeoxyglucose method.

The effects of tissue heterogeneity on the estimation of regional cerebral glucose utilization (rCMRglc) in normal humans with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) were compared with respect to the various kinetic models of the [18F]FDG method. The kinetic models were conventional homogeneous tissue models of the [18F]FDG method, with (4K Model) and without (3K Model) a rate constant to account for an apparent loss of [18F]2-fluoro-2-deoxy-D-glucose-6-phosphate ([18F]FDG-6-P), and a tissue heterogeneity model (TH Model). When either of the kinetic models designed for homogeneous tissues was applied to heterogeneous tissues, estimates of the rate constant for efflux of [18F]FDG from the tissue (k2*) and of the rate constant for phosphorylation of [18F]FDG (k3*) decreased as the duration of the experimental period was increased. When the 4K Model was used, estimates of the rate constant for the apparent dephosphorylation of [18F]FDG-6-P (k4*) were significantly greater than zero and fell with increasing duration of the experimental period. Although the TH Model included no term to describe an apparent dephosphorylation of [18F]FDG-6-P, the fit of the TH Model to the time course of total tissue radioactivity was at least as good as and often better than the fit of the 4K Model in the 120-min period following the pulse of [18F]FDG. Hence, the high estimates of k4* found in PET studies of less than or equal to 120 min can be explained as the consequence of measuring radioactivity in a heterogeneous tissue and applying a model designed for a homogeneous tissue; there remains no evidence of significant dephosphorylation of [18F]FDG-6-P in this time period. Furthermore, use of the 4K Model led to an overestimation of rCMRglc; whole-brain glucose utilization calculated with the 4K Model was greater than 20% higher than values usually obtained in normal humans by the model-independent Kety-Schmidt technique. rCMRglc was accurately estimated by the TH Model and, in experimental periods sufficiently long to minimize the effects of tissue heterogeneity, also by the original 3K Model of the deoxyglucose method.

Adult↗
PubMed1992

Metabolic impairment in human amnesia: a PET study of memory networks.

Human amnesia is a clinical syndrome exhibiting the failure to recall past events and to learn new information. Its "pure" form, characterized by a selective impairment of long-term memory without any disorder of general intelligence or other cognitive functions, has been associated with lesions localized within Papez's circuit and some connected areas. Thus, amnesia could be due to a functional disconnection between components of this or other neural structures involved in long-term learning and retention. To test this hypothesis, we measured regional cerebral metabolism with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in 11 patients with "pure" amnesia. A significant bilateral reduction in metabolism in a number of interconnected cerebral regions (hippocampal formation, thalamus, cingulate gyrus, and frontal basal cortex) was found in the amnesic patients in comparison with normal controls. The metabolic impairment did not correspond to alterations in structural anatomy as assessed by magnetic resonance imaging (MRI). These results are the first in vivo evidence for the role of a functional network as a basis of human memory.

Adult↗
PubMed1992

In vivo demonstration of insulin-receptor defect with 123I-labeled insulin and scintigraphic scanning in severe insulin resistance.

OBJECTIVE: Insulin-receptor function in humans is usually studied in vitro on readily available cells, e.g., erythrocytes and fibroblasts. Although these cells are not metabolically important targets for insulin action, information derived from them are often taken as representative of other tissues. The aim of this study was to investigate insulin receptors in vitro on erythrocytes and in vivo on one of the main insulin-target organs, the liver. RESEARCH DESIGN AND METHODS: A 16-yr-old girl affected by severe insulin resistance was identified. Insulin receptor binding was measured on the erythrocytes of the patient and of 6 nondiabetic volunteers. The biodistribution of 123I-labeled insulin was studied in vivo by scintigraphic scanning in the insulin-resistant patient and in 10 nondiabetic volunteers. RESULTS: Erythrocytes of this patient displayed a markedly reduced [125I]insulin binding. In vivo 123I-insulin biodistribution was characterized by lack of hormone uptake by the liver (4 vs. 21% of the injected dose in control subjects) contrasting with intense accumulation of radioactivity in the kidneys. CONCLUSIONS: Our studies show that defects of insulin binding can be directly demonstrated in vivo on liver receptors with a noninvasive technique with low radiotoxicity.

Adolescent↗
PubMed1991

Sneddon syndrome: cerebral perfusion studies by Tc99m HM-PAO and SPECT.

Sneddon syndrome is a non-inflammatory, non-atherosclerotic disease involving small and medium-sized arteries of the brain and of the skin. The arteriographic examination is often negative despite progressive impairment of the neurological status. In 3 patients with Sneddon syndrome cerebral perfusion was assessed with single photon emission computerized tomography (SPECT) and technetium99 m-hexamethylpropylenamineoxime (Tc99 HM PAO). A correlation between clinical and SPECT finding was found, with significant focal reduction of regional cerebral blood flow (rCBF) in the two more severely affected patients.

Adult↗