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Results for “Radioactive Tracers”

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At least 19 recordsLinked to original sources
PubMed1982

Bone blood flow in the femora of anesthetized and conscious dogs in a chronic preparation, using the radioactive tracer microsphere method.

The radioactive tracer microsphere method is applicable to the study of the hemodynamics of bone. As observed previously by others, areas of predominantly cancellous bone produce higher blood flow measurements than do areas of predominantly cortical bone. Bone containing fatty marrow has lower blood flow rates than does bone containing hematopoietic marrow. Blood flow to the femoral neck was the greatest measured (26.74 +/- 1.95 ml/min/100 gm), while the diaphyseal region was the area with the lowest flow (4.67 +/- 0.46 ml/min/100 gm). There was no significant difference between consecutive measurements using up to five differently labeled radioactive microspheres. This enabled observations of the effects of an experimental procedure on bone blood flow in the same animal. Additionally, there was no statistically significant differences between regional blood flows measured 40 days apart in the same animal. Bone blood flow measurements were slightly lower in anesthetized than in conscious dogs. The RTM method is the one most suitable for the estimation of bone blood flow under either acute or chronic conditions.

Anesthesia↗
PubMed1993

Estimation of steady-state flux rates in metabolic systems by computer simulations of radioactive tracer experiments.

The dynamics of radioactive tracers in metabolic systems can be mathematically modelled by coupled systems of differential equations for both the concentrations and the specific radioactivities of the metabolites involved. Computer simulations, i.e. direct fitting of numerical solutions of these equations to observed time-courses of metabolites and specific radioactivities, enables one to estimate unknown kinetic parameters of the system. The theoretical fundamentals of this approach and the main steps towards the quantitative assessment of flux rates in stationary metabolic systems are outlined. An application of the method to the purine nucleotide metabolism of Ehrlich ascites tumor cells is given based on a simplified model of this pathway. The obtained steady-state flux rates indicate a marked increase in the metabolism of the adenine nucleotides during the proliferating phase in comparison to the resting phase of tumor growth.

Adenine Nucleotides↗
PubMed1997

Changes in radioactive tracer distribution in rats after 24 hours of 45 degrees hind limb unweighting.

INTRODUCTION: Changes in radioactive tracer distribution were examined in rats after exposure to a simulated microgravity model of 45 degrees head down tilt (45HDT) or 45 degrees hind limb unweighting (45HU) for up to 24 h. METHODS: Rats were randomly assigned to either 45HDT (or 45HU) experimental groups or control groups for each time point of 0.5 h, 1 h, 2 h, 4 h, 8 h, or 24 h. The 0.5-h through 8-h experimental rats were anesthetized and placed head-down on a ramp at 45 degrees, while control rats were placed in a prone position. Non-anesthetized rats in the 24-h experimental group were tail-suspended at 45 degrees, while control rats were allowed unrestrained movement. Technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, physical half-life of 6.02 h, MW = 492 amu) and indium-labeled diethylenetriamine pentaacetate (111In DTPA, physical half-life of 3.5 d, MW = 545 amu) were used to measure body organ distributions of the radioactive tracers at the 0.5-h-8-h and 24-h time points, respectively. Major organs were harvested after each time period and measured for radioactive counts. Light and electron micrographs were examined. RESULTS: Mean 111InDTPA counts for the lungs, kidneys, and brains of the 24 h 45HU groups were significantly higher than control counts. Light and electron microscopy demonstrated the development of pulmonary edema in the alveolar septal areas after 2 h of 45HDT, and a shift in edema to the pulmonary airways and pulmonary arteries after 24 h of 45HU. CONCLUSIONS: Pulmonary edema development, accompanied by a significant increase in 111InDTPA lung, kidney, and brain counts in the 24-h 45HU groups, suggests vascular injury in the microcirculation of these organs.

Animals↗
PubMed1976

Radioactive tracers in peripheral vascular disease.

The use of radioactive tracers in the diagnostic and therapeutic evaluation of the patient with peripheral arterial or venous disease has proven to be clinically useful. Their application has provided a means by which the regional distribution of perfusion at the level of the microcirculation, at rest and under various stresses, can be assessed. Graft patency can be determined simply and repeatedly, and the relative perfusion of "ischemic" ulcers can be used to assess their healing potential. The presence of arteriovenous shunts can be verified, localized, and quantified. Venous thrombi can be detected, and the competence of the venous valvular system and muscle pump as well as the hemodynamics of the venous system can be quantified.

Amputation, Surgical↗
PubMed1989

[Theoretical and practical problems posed by the measurement of capillary filtration by radioactive tracers].

Screening for abnormal capillary filtration in the limbs with radioactive tracers requires the use of molecules of a known hydrodynamic radius. The molecule labeling should be obtained with a pure gamma-emitting radioactive atom, presenting a steady bond with the molecule, in vivo. Indium-111-labeled albumin appears to be the best tracer, and should be injected concurrently with the technetium 99m-labeled erythrocytes. The latter tracer permits assessing volume variations induced by the venous blood return block needed to obtain a capillary pressure increase. A qualitative estimation of lymphatic flow, and screening for abnormal permeability of the lymphatic vessels must be carried out as part of any capillary filtration study protocol.

Capillary Permeability↗
PubMed1980

Lung ventilation model for radioactive tracer itdal breathing.

A mathematical lung ventilation model for radioactive tracer tidal breathing is developed on the basis of the previously established simple mathematical lung model for quantitative regional ventilation measurements. In the present model, the periodicity of breathing is completely taken into account. A precise definition of the effective specific ventilation is given. This was found to be related to the ratio of tidal volume (TV) and functional residual capacity (FRC). The determination of the regional effective specific ventilation is reduced to a simple fitting to a straight line. A description is given of the method of measurement (in the framework of radioisotope dynamic studies) that makes it possible to use the mathematical model for the actual determination of lung ventilation and volume parameters. The model is experimentally verified on healthy subjects, and the value of the effective specific ventilation obtained is in agreement with comparable parameters in the literature. Furthermore, the value for TV/FRC is comparable with that determined by classical spirometrical methods.

Humans↗
PubMed2002

Introduction to the physics of molecular imaging with radioactive tracers in small animals.

Recent advances have greatly enhanced the three-dimensional (3D) imaging of radioactive tracers in living animals. this article introduces the physics of imaging behind the imaging methods. The article first discusses the selection of the radiation emitted from the tracer and then the process of tomographic reconstruction or how 3D images are made from imaging around the outside of the animal. The technique of single photon emission computed tomography (SPECT) in which the detection of one X-ray or gamma ray at a time is employed for image formation is then described. Finally, positron emission tomography (PET) which relies on the simultaneous detection of the pair of gamma-rays formed when the positron annihilates is presented.

Animals↗
PubMed1975

Report of the Inter-Society Commission for Heart Disease Resources. Optimal resource guidelines for radioactive tracer studies of the heart and circulation.

The status of radioactive tracer studies in cardiovascular diagnosis is summarized. Planning guidelines are suggested for a hospital nuclear medical service including a central nuclear medical facility and satellite units, and resource criteria are given for professional personnel including training and duties, equipment, space, and support system. The administrative organization of a nuclear medical service and case loads are discussed. Guidelines for equipment maintenance and quality controls are described.

Cardiovascular Diseases↗
PubMed1989

Static and dynamic computerised radioactive tracer studies, vital dye staining and theoretical mathematical calculations to ascertain the mode of survival of single cephalad channel venous island flaps.

Experiments were performed to ascertain the perfusion and drainage of single cephalad channel saphenous venous flaps in dogs. In the first experiment a standard saphenous flap and a single cephalad channel saphenous venous island flap were dissected on contralateral thighs of dogs. A radioactive tracer, 99mTc, was injected into a foreleg vein and its appearance in both flaps was monitored with the use of a static and dynamic scanner. After this experiment, Evans blue, a vital dye, was injected into the foreleg vein of the dog. Five minutes later both flaps were excised and the dye in the flaps was assayed quantitatively. In the third experiment radioactive tracer was injected into the single cephalad channel venous flap subcutaneously and its decay in the flap as well as its uptake in the rest of the body were measured dynamically. The experiments show that the single cephalad channel venous island flap is perfused by and drains through its single cephalad vein. A mathematical model to justify the above conclusion was worked out independently, based on standard values involved in mammalian circulatory mechanisms as in dog and man.

Animals↗
PubMed1975

Deposition and clearance of inhaled fibrous minerals in the rat. Studies using radioactive tracer techniques.

The deposition and clearance of various fibrous materials have been investigated in the rat using radioactive tracer techniques. The materials used include the U.I.C.C. standard reference samples and synthetic mineral fibres. Measurements of total and alveolar deposition were correlated with the AMADs of the radioactive dust samples which ranged from 1 to 2.5 micron. Although total deposition increases steeply over this range, alveolar deposition is relatively constant only increasing from about 10 to 13%. Alveolar deposition is lower than in man, but the maximum in alveolar deposition appears to occur at a similar aerodynamic diameter. Half times of alveolar clearance, measured over a period of several months following single inhalation exposures, were in the range 60-90 days and no significant difference was observed between amphibole and chrysotile asbestos. Autoradiographs of lung sections indicate that alveolar deposition is relatively uniform and occurs right up to the periphery of the lung. Over a period of several months the uniform distribution alters to one in which fibres accumulate in foci which are mainly subpleural. These foci act as centres for the development of nodular fibrosis.

Animals↗