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Biomedical subjects

A Alavi

Publications and source records attributed to A Alavi.

At least 325 records · Page 18Linked to original sources
PubMed1986

Enhancement of tumor contrast on radioimmunoscans by using mixtures of monoclonal antibody F(ab')2 fragments.

F(ab')2 fragments of MAbs GA 73-3 (IgG 2 a) and CO 29.11 (IgG 1), which detect distinct antigenic determinants on adenocarcinoma cells of the gastrointestinal tract, were labeled with 131I using the iodogen method. 41 nude mice bearing SW-948 CRC tumors were injected either with a mixture of 100 microCi (11 micrograms) each (n = 9) of the two 131I-F(ab')2 fragments or with either fragment alone at various doses (each group consisting of 8 mice): GA 73-3, 100 microCi (11 micrograms) and 200 microCi (25 micrograms); CO 29.11, 100 microCi (11 micrograms) and 200 microCi (26 micrograms). Whole-body images of the mice were obtained daily for up to six days after injection. Ratios of cpm/pixel in the tumor to those in the rest of the body (rob), representing tumor contrast, were significantly (p less than 0.05) higher in the group of mice injected with the mixture (3.9 +/- 1.5) as compared to those given 100 or 200 microCi of either fragment separately. The biological half-life (T1/2 biol.) of the mixture (44.7 +/- 14.5 h) in the CRC tumors was significantly (p less than 0.05) longer than T1/2 biol. determined in the groups given either fragment alone. T1/2 biol. in the rob was similar in all groups of mice examined.

Animals↗
PubMed1985

Sequential technetium-99m/gallium-67 scintigraphic evaluation of subclinical osteomyelitis complicating fracture nonunion.

Twenty-four patients with a history of post-traumatic fracture nonunion underwent sequential 99mTc and 67Ga citrate scintigraphy in an attempt to differentiate between posttraumatic fracture nonunion and nonunion complicated by subclinical osteomyelitis. Neither technetium nor gallium studies alone nor in combination, with or without clinical correlation, could help delineate between fracture nonunion and nonunion complicated by subclinical osteomyelitis because of the increased technetium and gallium radioisotope uptake associated with the nonunion site.

Adolescent↗
PubMed1985

Nuclear magnetic resonance: an overview of its spectroscopic and imaging applications in pediatric patients.

Magnetic resonance (MR) is a technique that permits the noninvasive evaluation of morphologic features and function based on the distribution of protons and other selected elements. We present a basic description of MR and illustrate both 31P-MR spectroscopy and proton imaging applications in pediatric patients. The applications of these techniques are diverse, and are presented concisely in an attempt to give pediatricians an overview of this new technology and its potential role in patient management.

Adolescent↗
PubMed1985

Glucose metabolic rate kinetic model parameter determination in humans: the lumped constants and rate constants for [18F]fluorodeoxyglucose and [11C]deoxyglucose.

The rate constants and lumped constants (LCs) for [18F]fluorodeoxyglucose ([18F]FDG) and [11C]deoxyglucose ([11C]DG) were determined in humans for the glucose metabolic rate kinetic model used to measure local cerebral glucose consumption. The mean values (+/- SE) of the LCs for [18F]FDG and [11C]DG are 0.52 +/- 0.028 (n = 9) and 0.56 +/- 0.043 (n = 6), respectively. The mean values (+/- SE) of the rate constants k*1, k*2, k*3, and k*4 for [18F]FDG for gray matter are 0.095 +/- 0.005, 0.125 +/- 0.002, 0.069 +/- 0.002, and 0.0055 +/- 0.0003, respectively. The corresponding values for white matter are 0.065 +/- 0.005, 0.126 +/- 0.003, 0.066 +/- 0.002, and 0.0054 +/- 0.0006, respectively. Using these values and previously published values for the rate constants for [11C]DG, the average whole-brain metabolic rates for glucose in normal subjects measured with [18F]FDG and [11C]DG are 5.66 +/- 0.37 (n = 6) and 4.99 +/- 0.23 (n = 6) mg/100 g/min, respectively. These values are not significantly different (t = 1.56, p greater than 0.10) and agree well with reported values in the literature determined by means of the Kety-Schmidt technique.

Adolescent↗
PubMed1985

Cerebral blood flow with the continuous infusion of oxygen-15-labeled water.

This work describes the determination of CBF in eight normal human subjects with positron emission tomographic (PET) imaging using the continuous intravenous infusion of H2(15)O. A whole-brain CBF model is described that permits the comparison of the CBF values determined using PET with those obtained using other methods. This model includes a correction for whole-brain recovery coefficient, a correction for the underestimation of flow due to the nonlinearity of the CBF model when considering tissue that includes both gray and white matter, the use of in vitro-determined brain-blood partition coefficients for gray and white matter, and a variation of the equilibrium model that permits the arterial concentration to vary. CBF values using this method compare well with values determined previously. Regional determinations using a brain overlay atlas are presented. Radiation dosimetry for the continuous infusion of H2(15)O is also included.

Adult↗
PubMed1985

Quantitative analysis of liver function in percutaneous transhepatic biliary drainage patients.

The diagnostic usefulness of Tc-99m DISIDA cholescintigraphy as a predictor of eventual catheter and hepatic function in patients who have undergone percutaneous transhepatic biliary drainage (PTBD) for extrahepatic biliary obstruction was evaluated. Twenty-nine cholescintigrams were performed in 14 patients. The examinations were divided into two groups: Group A (N = 17), in which the patient's clinical status deteriorated within two to three days post-PTBD, and Group B (N = 12), in which the patients did well clinically post-PTBD. No significant difference between the two groups was demonstrated by visual analysis of the analog images or by analysis of serum bilirubin levels. A computer program, developed by the authors, quantitates several parameters of DISIDA kinetics, reflecting hepatic function based upon compartmental analysis. A significant difference (P less than .001) was demonstrated between the mean transport constants (blood clearance constant = k1; hepatic clearance constant = k2) for the two groups. It is concluded that serum bilirubin levels and visual inspection of analog images are inadequate independent predictors of hepatic function in patients post PTBD. The transport constants k1 and k2 are quantitative parameters of hepatic function that may be of prognostic value in patients post PTBD.

Adult↗
PubMed1985

The "liver scan" appearance in cholescintigraphy. A sign of complete common bile duct obstruction.

One hundred consecutive Tc-99m IDA hepatobiliary scans were reviewed revealing 14 scans (14%), that showed nonvisualization of the common bile duct (CBD), gallbladder (GB), and small bowel (SB), but good hepatic uptake of Tc-99m IDA derivative, a pattern designated by us as "the liver scan appearance." In 11 of 14 cases (79%), the diagnosis of complete CBD obstruction was confirmed by surgery, percutaneous transhepatic cholangiogram (PTC), endoscopic retrograde cholangiopancreatography (ERCP), and/or percutaneous needle biopsy (PBx). Common bile duct obstruction was suspected but not proven in the other three cases. The cholescintigraphic, ultrasound, PTC, ERCP, intraoperative cholangiogram, clinical, laboratory, and surgical findings are presented and correlated. The "liver scan-appearance" by cholescintigraphy should suggest a diagnosis of complete common bile duct obstruction; however, it does not specifically differentiate between stone or tumor as the cause of obstruction.

Cholangiography↗
PubMed1985

Sources of variability in quantitative thallium analysis.

Nineteen patients undergoing exercise thallium scanning had two separate redistribution 40 degree LAO acquisitions obtained; the gamma camera was repositioned between the views. Data were analyzed by generating 60-point circumferential profile curves for each of the 38 images and the variability of individual points and 18 degrees and 36 degrees segments was determined. Intraobserver variability, assessed by reanalyzing the scans one week later, was approximately 5.0%. The interobserver variability was of similar magnitude (approximately 6%). The total reimaging variability was, however, significantly larger (approximately 13%). It is concluded that quantitative image analysis is highly reproducible with low intra- and interobserver variabilities, but the act of repositioning and reimaging introduces significant additional variability. This may limit the ability of quantitative thallium scanning to document changes in the size of defects.

Adult↗
PubMed1985

Viscerally induced cutaneous vasospasm.

Superficial vasomotor tone in the forearm has been thought to be dependent mostly on vasodilatation rather than vasoconstriction. Despite this view we report now that a mechanism for profound vasoconstriction exists in the forearm surface. This phenomenon was observed in normal subjects undergoing elective radial artery catheterization and the stimulus for the vasoconstriction consisted of the intra-arterial infusion of normal saline (rate of 0.5 - 6.0 ml/min). Two components to this reaction were observed. A stable pericatheter zone of pallor varied in extent proportional to the rate of infusion. The second component consisted of distal patches of vasoconstriction over the whole anterior forearm surface which first appeared 5 to 10 seconds after the infusion rate was increased. These satellite areas tended to coalesce with sustained infusion but they were unstable over time. Local changes in vascular intrinsic regulation can account for the pericatheter vasoconstriction but this does not readily explain the observed distal changes. The time latency, distribution and evolution of the distal vasoconstriction suggests the operation of an autonomic vasomotor reflex arc.

Adult↗
PubMed1985

Ischemic lesions of the occipital cortex and optic radiations: positron emission tomography.

We used 18-F-fluoro-2-deoxyglucose positron emission tomography (PET) and computed tomography (CT) to study eight patients with homonymous hemianopias or quadrantanopias due to ischemic lesions of the visual pathways. Four patients with ischemic damage to all or part of the occipital lobe had decreased glucose metabolism in the affected region. Three patients with ischemic damage limited to the optic radiations had decreased glucose metabolism in the portion of striate cortex appropriate for the visual field defect. Changes in glucose metabolism frequently occurred in the undamaged ipsilateral thalamus and visual association areas.

Adult↗
PubMed1985

Multiple-hospital survey of ejection-fraction variability using a cardiac phantom.

A dynamic cardiac phantom was used to provide identical input data at 11 different nuclear medicine laboratories throughout the Philadelphia area, and the variability in the resulting calculations of ejection fraction (EF) was assessed. The variability observed between different operators using the same computer system averaged 3 EF units, which was similar to that between different observers using different types of computers. In the range of low ejection fractions, however, there was a suggestion that EFs calculated with an MDS computer were slightly lower than those from a DEC computer.

Cardiac Output↗
PubMed1985

Osteomalacia. An imposter of osseous metastasis.

A case of osteomalacia with multiple asymmetrically distributed pseudofractures (Looser's zones) simulating metastases is presented. Radiographic correlation is essential to increase specificity and avoid misinterpretation.

Aged↗
PubMed1984

Contralateral cerebellar hypometabolism following cerebral insult: a positron emission tomographic study.

Positron emission tomographic studies of 16 patients with cerebral ischemia and brain tumor showed asymmetries in cerebellar metabolism not encountered in 14 normal control subjects. An asymmetry was present in 62.5% of cases. The lower metabolic rate occurred in the cerebellar hemisphere contralateral to the cerebral lesion (p less than 0.001; sign test). In all cases computed tomography showed the supratentorial lesion to be unilateral and the posterior fossa contents to be unaffected. The presence of depressed cerebellar metabolism was highly associated with involvement of the contralateral parietal lobe (p less than 0.02; phi coefficient). The presence of a cerebellar abnormality was not related to the presence of any particular sign. Serial studies showed normalization of cerebellar metabolism over time. It is likely that this effect is a result of interruption of the functional interconnections between the cerebrum and the cerebellum.

Adult↗
PubMed1984

Positron emission tomographic studies of perceptual tasks.

Metabolic mapping in conjunction with positron emission tomography was used to examine the response of the human brain to physiological stimuli. Local cerebral glucose consumption was measured by means of the fluorine-18-labeled fluorodeoxyglucose technique. The coefficient of variation of this measurement for various gray matter structures varies from 19.5 to 26.4%. If repeat measurements are made in the same subject using carbon-11-labeled deoxyglucose as the tracer, the coefficient of variation of repeat measurements for these same structures is reduced to between 5.2 and 8.7%. Stimulation of one visual field in normal subjects produced a significant (p less than 0.01) increase in metabolism in the contralateral visual cortex. An auditory stimulus consisting of a tape-recorded factual story presented through earphones to only one ear produced a significant (p less than 0.001) increase in glucose consumption in the contralateral temporal cortex. The effects of vigilance or attention on cerebral metabolism were also examined. There was significantly greater metabolism in the right versus the left inferior parietal region in subjects attending to a visual or auditory task compared with those who were not. Anxiety appeared to produce significantly greater glucose utilization in the right hemisphere compared with the left in those subjects who had a higher level of anxiety during the measurement. Metabolic mapping promises to be a powerful new tool in furthering our understanding of the organization and functioning of the human brain.

Anxiety↗
PubMed1984

Labeling monoclonal antibodies and F(ab')2 fragments with (111In) indium using cyclic DTPA anhydride and their in vivo behavior in mice bearing human tumor xenografts.

Monoclonal antibodies (MAb) and their F(ab')2 fragments to human colorectal carcinoma (CRC) and human melanoma-associated antigens were conjugated to diethylenetriaminepentaacetic acid (DTPA) via an acylation reaction using cyclic DTPA dianhydride. Relative immunoreactivity of the F(ab')2 fragments was as high as 70% when an average of only 0.7 DTPA molecules was conjugated per fragment, decreasing rapidly to less than 5% when 9.0 DTPA molecules were conjugated. The 111In-labeled whole MAb in mice bearing human tumor xenografts showed higher concentrations in tumor, liver, kidney, and spleen 7 days after injection of MAb when compared with the same MAb labeled with 131I. F(ab')2 labeled with 111In showed a marked persistence in the tumor-bearing mice with higher concentrations in all organs except blood, when compared with 131I-labeled F(ab')2. Radioactivity was particularly high in the kidneys. Although images of human tumor xenografts were easily visualized using 131I-labeled F(ab')2 3 days after injection, it was difficult to visualize tumor grafts with 111In-labeled F(ab')2 due to persistently high renal, liver, and background activity. Increased catabolism of the 131I-labeled MAb may be the cause of the difference; but antibodies with high immunological activity are a necessity for in vivo imaging studies before firm conclusions can be drawn.

Animals↗