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Biomedical subjects

E A George

Publications and source records attributed to E A George.

At least 19 recordsLinked to original sources
PubMed2001

The A(y) problem for p-3He elastic scattering.

We present evidence that numerically accurate quantum calculations employing modern internucleon forces do not reproduce the proton analyzing power, A(y), for p- 3He elastic scattering at low energies. These calculations underpredict new measured analyzing powers by approximately 30% at E(c.m.) = 1.20 MeV and by 40% at E(c.m.) = 1.69 MeV, an effect analogous to a well-known problem in p-d and n-d scattering. The calculations are performed using the complex Kohn variational principle and the (correlated) hyperspherical harmonics technique with full treatment of the Coulomb force. The inclusion of the three-nucleon interaction does not improve the agreement with the experimental data.

Journal Article↗
PubMed1992

Serendipitous scintigraphic detection of asymptomatic anastomotic pseudoaneurysms in human pancreatic allografts.

Two cases of scintigraphically detected asymptomatic graft anastomotic pseudoaneurysms are reported. Both patients previously underwent simultaneous renal and pancreatic transplantation. The role of imaging in the diagnosis of this relatively rare, but potentially lethal, vascular complication of pancreatic transplantation is discussed. This is the first report of anastomotic pseudoaneurysms in pancreatic transplants being diagnosed by scintigraphy.

Adult↗
PubMed1991

Assessment of renal allograft pathology by scintigraphic and ultrasound index-markers.

The efficacies of two scintigraphic and two sonographic techniques and resultant index values, as markers of renal allograft pathology, were assessed. Index values of 183 combined scintigraphic and sonographic examinations in 47 graft recipients were compared to the pathological diagnosis of transplant biopsies and subsequent clinical outcome. All recipients were studied with baseline imaging techniques postoperatively, again when indicated by predefined clinical criteria, and prior to graft biopsy. The scintigraphic technique involved the calculation of indices of thrombotic activity and cortical graft perfusion. Ultrasound involved determination of the Doppler resistance index of Pourcelot and estimations of graft volume from real time images. A decreased cortical perfusion index was, overall, the most sensitive index of acute or chronic graft pathology, but it lacked specificity. Increased thrombotic and resistance indices were 96% and 86% sensitive for acute vascular rejection and were 82% and 76% specific. Jointly increased thrombotic and resistance indices improved the specificity for acute vascular rejection to 98%. An increase in graft volume of more than 50% over stable values was 100% sensitive and 92% specific for acute interstitial rejection, and 95% specific when paired with a normal thrombotic index. A marked increase in the thrombotic index was 100% sensitive for cyclosporine-induced thrombotic microangiopathy, but only 49% specific. The specificity of a markedly increased thrombotic index for thrombotic microangiopathy improved to 93% when the Doppler resistance index remained normal or was only marginally elevated. None of the scintigraphic or ultrasound indices were helpful for the diagnosis of acute tubular necrosis, chronic rejection, recurrent glomerulopathy, or graft infection.

Biopsy↗
PubMed1988

Recurrent hemolytic uremic syndrome in a renal transplant recipient.

This case report presents clinical, scintigraphic, duplex sonographic, and biopsy findings in a 23-year-old female renal allograft (RAG) recipient, who had transplantation for chronic renal failure secondary to hemolytic uremic syndrome (HUS). She demonstrated acute and rapidly progressing RAG failure at 7 weeks after transplantation.

Adult↗
PubMed1988

Radionuclide surveillance of the allografted pancreas.

To determine the value of scintigraphy to detect posttransplantation complications of the allografted pancreas, we retrospectively reviewed 209 scintigrams obtained with 99mTc-sulfur colloid (99mTc-SC) and 99mTc-glucoheptonate (99mTc-GH). The scintigraphic studies were performed in 37 recipients of simultaneous renal and pancreatic allografts harvested from the same donor. 99mTc-SC was used as an indicator of thrombotic vasculitis; pancreatic perfusion and blood-pool parameters were monitored with 99mTc-GH. In 11 of the 37 recipients, scintigraphic abnormalities suggested posttransplantation infarction. Recurrent episodes of acute rejection of the pancreatic allograft, which always coincided with acute rejection of the renal allograft, were monitored in 24 recipients. Rejection-induced ischemic pancreatitis was suggested in 12 of the 24 recipients and persisted in 10 recipients for several weeks after improvement of renal allograft rejection. Pancreatic atrophy was suggested scintigraphically in 16 of the 24 recipients with recurrent episodes of rejection. Spontaneous pancreatic-duct obstruction and obstructive pancreatitis were associated with a scintigraphic pattern similar to that of rejection-induced ischemic pancreatitis. We concluded that the specific radionuclides used in this series are useful for the surveillance and assessment of posttransplantation pancreatic infarction, acute rejection, pancreatitis, and atrophy.

Adult↗
PubMed1983

Renal allograft accumulation of Tc-99m sulfur colloid: temporal quantitation and scintigraphic assessment.

Renal allograft accumulation of Tc-99m sulfur colloid (TSC) was studied using visual assessment of scintigraphic displays and a quantitative temporal model in 210 examinations of 56 transplant recipients. The quantitative temporal model related the immediate pool of the radioagent in the transplant to the fixed allograft accumulation of TSC at 20 minutes after administration. Examinations performed less than 3 days after grafting or steroid pulse therapy were excluded. Rejection was established by clinical and biochemical evaluation in all 84 examinations that showed acute or chronic allograft rejection. Rejection was accurately diagnosed by visual scintigraphic assessment in 82% of the established cases; this improved to 99% with relative temporal quantitation analysis. Sensitivity improved from 78% by visual examination to 95% with temporal quantitation and specificity improved from 83% to 100%.

Graft Rejection↗
PubMed1982

Radionuclide diagnosis of allograft rejection.

Interaction with one or more anatomical and physiopathological characteristics of the rejecting renal allograft is suggested by those radioagents utilized specifically for the diagnosis of allograft rejection. Rejection, the most common cause of declining allograft function, is frequently mimicked clinically or masked by other immediate or long term post transplant complications. Understanding of the anatomical pathological features and kinetics of rejection and their modification by immunosuppressive maintenance and therapy are important for the proper clinical utilization of these radioagents. Furthermore, in selecting these radionuclides, one has to consider the comparative availability, preparatory and procedural simplicity, acquisition and display techniques and the possibility of timely report. The clinical utilities of radiofibrinogen, 99mTc sulfur colloid and gallium-67 in the diagnosis of allograft rejection have been evaluated to a variable extent in the past. The potential usefulness of the recently developed preparations of 111In labeled autologous leukocytes and platelets are presently under investigation.

Animals↗
PubMed1981

Quantitative temporal analysis of 99mTechnetium p-isopropyl-iminodiacetic acid (PIPIDA) as a measure of hepatic function in health and disease.

Excretory liver function was analyzed in 10 healthy volunteers and 28 subjects with acute or chronic liver injury following intravenous administration of 99mtechnetium p-isopropyl iminodiacetic acid. Hepatobiliary transit of this agent was quantitated at 5-min intervals for a total of 60 min. Indices of total liver activity, liver cell uptake, liver parenchymal clearance, and bile duct clearance of 99mtechnetium p-isopropyl iminodiacetic acid were calculated from time--activity curves over heart, liver, extrahepatic bile ducts, and gallbladder. Seven subjects with acute viral hepatitis, 15 with extrahepatic biliary obstruction, and 6 with intrahepatic cholestasis were evaluated. Compared with healthy volunteers, a significant (p less than 0.0001) reduction in total liver activity and liver parenchymal clearance was demonstrated in all patient groups. Major resolution in all liver-derived indices, particularly total liver activity, occurred during convalescence from hepatitis and after biliary drainage. Nonmeasurable bile duct clearance always indicated a diagnosis of extrahepatic obstruction in cholestatic subjects, and this index normalized in subjects following biliary drainage. Whereas visual assessment of 99mtechnetium p-isopropyl iminodiacetic acid scans provided limited, useful information about the functional status of the liver, quantitative temporal analysis proved to be a much more effective technique.

Biliary Tract↗
PubMed1980

Mechanism of hepatic extraction of gelatinized 99m technetium sulfur colloid.

Hepatic extraction, cellular and subcellular localization of gelatin stabilized Tc-99m sulfur colloid was studied in the rat model with time sequenced microautoradiography from 15 min to 24 h following I.V. administration of the tracer. Hepatic lobular and cellular distribution, quality and quantity of focal grain pattern, grain clusters, remained essentially constant for the period of study. Grain clusters were associated predominantly with Kupffer cells lining the peripheral segment of hepatic lobular sinusoids. Subcellular localization of gelatinized Tc sulfur colloid, stained prior to the I.V. administration with osmium tetroxide, was demonstrated with a transmission electron microscope in unosmicated liver tissue. Extracted Tc sulfur colloid particles were attached in groups to cytoplasmatic membranous intrasinusoidal projections of activated Kupffer cells. Intracytoplasmatic phagocytosis was not demonstrated. The kinetic arrest and en groupe extraction of Tc sulfur colloid particles at the Kupffer cell membrane suggests a specific membrane receptor site and specific Tc sulfur colloid particle-plasma protein interaction at the time of extraction. Hepatic extraction of gelatinized Tc sulfur colloid thus reflects primarily extra and intra hepatic hemodynamics and does not serve as an indicator of phagocytic hepatic reticuloendothelial system function.

Animals↗
PubMed1979

Radionuclide venography and lung scanning: Concise communication.

In 102 patients suspected of pulmonary embolism, we have assessed the ability of a radionuclide (emission) venogram to complement the pulmonary perfusion scintigram in establishing a diagnosis. The efficacy was compared using decision analysis and Bayes's theorem. Two criteria for a positive test were compared: Criterion 1--the test is positive if the lung scan a) indicates a high probability of pulmonary embolus, or b) is abnormal but indeterminate for pulmonary embolus; Criterion 2--the test is positive a) if the lung scan indicates a high probability of pulmonary embolus, or b) if the emission venogram is positive in a patient with a lung scan considered abnormal but indeterminate for pulmonary embolus. The use of Criterion 2 decreased the sensitivity from 100% to 95% and increased the specificity from 74% to 93%. We conclude that a simultaneous emission venogram assists in improving the specificity, accuracy, and the predictive value of a standard pulmonary perfusion study in the diagnosis of pulmonary embolus.

Foot↗
PubMed1976

Comparative evaluation of renal transplant rejection with radioiodinated fibrinogen 99mTc-sulfur collid, and 67Ga-citrate.

The diagnostic accuracy, ease, and technical feasibility of imaging with 131I-or 125 I-fibrinogen, 99mTc-sulfur colloid, and 67 Ga-citrate in renal transplant rejection are compared. Radiofibrinogen data resulted from literature review, radiocolloid data from 125 studies in 52 transplant patients, and gallium citrate data from 24 examinations in seven renal transplant patients performed simultaneously with the radiocolloid studied. Specificity of graft labeling during rejection appears to be similar with radiofibrinogen, 99mTc-sulfur colloid, and 67Ga-citrate. For routine clinical use 99mTc-sulfur colloid surpasses radiofibrinogen and radiogallium because of its better imaging qualities with a permissible radiation dose, leading to better separation of positive and negative results. The 99mTc-sulfur colloid accumulates in areas of intravascular fibrin thrombosis in acute and chronic rejecting renal transplants. Hence, the mechanisms for accumulation of 99mTc-sulfur colloid and labeled fibrinogen in rejecting transplants would seem to be similar. Such physiologic properties as rapid blood clearance and such physical properties as short physical half-life combine to produce reliable graft visualization with adequate definition, thus favoring 99mTc-sulfur colloid as the single agent of choice for clinical evaluation of renal transplant rejection at this time.

Animals↗
PubMed1975

Brain scans, dexamethasone therapy, and brain tumors.

Eight men with primary or metastatic brain tumors were examined with brain scans before and after the administration of dexamethasone. All patients demonstrated some improvement in their clinical neurologic status during therapy, and two patients had a dramatic response. Seven of the eight patients examined showed a decrease in the apparent size of the original lesion on recent brain scan while receiving dexamethasone. Comparison of immediate scans obtained 15 to 20 minutes following the administration of sodium pertechnetate Tc 99m with those obtained two or three hours later suggests that the change in apparent size of the original lesion results from decrease in peritumor edema.

Adult↗
PubMed1975

Further evaluation of 99m-Tc sulfur colloid accumulation in rejecting renal transplants in man and a canine model.

Renal transplant accumulation of 99m-Tc sulfur colloid was evaluated in 41 patients. Ninety-five examinations were performed comparing transplant with bone marrow activity and clinical or pathological diagnosis. 99m-Tc sulfur colloid accumulated in acute or chronic rejection as long as the vascular supply of the grafted kidney was not severely impaired. Accumulation was marked in chronic rejection, slight in acute rejection and absent in normally functioning transplants or in those with acute tubular necrosis. In the 10 dog models, no accumulation was seen in autografted transplants and early accumulation was demonstrated within the hyperacutely rejecting kidneys of allografted dogs.

Angiography↗