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Biomedical subjects

T F Budinger

Publications and source records attributed to T F Budinger.

At least 91 records · Page 5Linked to original sources
PubMed1983

Cardiovascular alterations in Macaca monkeys exposed to stationary magnetic fields: experimental observations and theoretical analysis.

Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposures to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system.

Animals↗
PubMed1983

Regional cerebral metabolic alterations in dementia of the Alzheimer type: positron emission tomography with [18F]fluorodeoxyglucose.

Alzheimer disease is the most common cause of dementia in adults. Despite recent advances in our understanding of its anatomy and chemistry, we remain largely ignorant of its pathogenesis, physiology, diagnosis, and treatment. Dynamic positron emission tomography using [18F]fluorodeoxyglucose (FDG) was performed on the Donner 280-crystal ring in 10 subjects with dementia of the Alzheimer type and six healthy age-matched controls. Ratios comparing mean counts per resolution element in frontal, temporoparietal, and entire cortex regions in brain sections 10 mm thick obtained 40-70 min following FDG injection showed relatively less FDG uptake in the temporoparietal cortex bilaterally in all the Alzheimer subjects (p less than 0.01). Left-right alterations were less prominent than the anteroposterior changes. This diminished uptake was due to lowered rates of FDG use and suggests that the metabolic effects of Alzheimer disease are most concentrated in the temporoparietal cortex. Positron emission tomography is a most powerful tool for the noninvasive in vivo assessment of cerebral pathophysiology in dementia.

Aged↗
PubMed1983

Radiation absorbed doses from iron-52, iron-55, and iron-59 used to study ferrokinetics.

Biological data obtained principally with Fe-59 citrate are used with physical data to calculate radiation absorbed doses for ionic or weak chelate forms of Fe-52, Fe-55, and Fe-59, administered by intravenous injection. Doses are calculated for normal subjects, primary hemochromatosis (also called idiopathic or hereditary hemochromatosis), pernicious anemia in relapse, iron-deficiency anemia, and polycythemia vera. The Fe-52 doses include the dose from the Mn-52m daughter generated after injection of Fe-52. Special attention has been given to the dose to the spleen, which has a relatively high concentration of RBCs and therefore of radioiron, and which varies significantly in size in both health and disease.

Computers↗
PubMed1983

Labeled choline and phosphorylcholine: body distribution and brain autoradiography: concise communication.

Following intravenous injection of labeled choline or phosphorylcholine in rats and mice, the brain uptake as percent injected dose was less than 0.2% with 6-12% going to kidney and 3-6% to liver. A study of [14C]choline autoradiography in a stump-tailed macaque demonstrated a five- to sixfold greater uptake in gray matter than in white matter. Dynamic positron imaging of [11C]choline in a rhesus monkey demonstrated rapid brain uptake followed by rapid washout, with heavy late uptake in muscle. The use of labeled choline and choline analogs as imaging agents in human studies is constrained by the low brain uptake relative to extracerebral tissues.

Animals↗
PubMed1982

Pulse injection, 13C tracer studies of lactate metabolism in humans during rest and two levels of exercise.

In order to determine the role of lactic acid as a metabolic substrate during exercise, the extent of its oxidation was studied using (13C) lactate under three different metabolic conditions in two subjects. During rest, easy exercise (work below the lactate inflection point), and hard exercise (work above the lactate inflection point), 100 mg of Na+-D,L(+)-2,3-(13C) lactate was injected via an indwelling catheter inserted in an antecubital vein. Blood as well as expired gas samples were collected up to 2 h post-injection. Subjects worked at average intensities of 53% and 74% VO2max during easy and hard exercise, respectively. During rest and easy exercise, blood lactate concentrations remained stable at 1-2 nM. During hard exercise, blood lactate increased to 3-4 times those observed at rest. Excretion of 13CO2 peaked much sooner and enrichment of 13C in CO2 was greater during both exercise intensities than during rest. Cumulative recovery of injected 13C as 13CO2 averaged 13.2 and 86.2% through 120 min during rest and easy exercise. Through 45 min of hard exercise, recovery of tracer as CO2 was the same as during a similar time point of easy exercise, 51.8%. The results support the contention that oxidation is the major fate of lactate during exercise.

Adult↗
PubMed1982

Preparation of 11C-methyl iodide and L-[S-methyl-11C]methionine by an automated continuous flow process.

A continuous flow procedure has been developed for the synthesis of 11C-methyl iodide and L-[S-methyl-11C]methionine from 11CO2. The preparation can be completed in 20 min after the end of bombardment. This procedure results in the production of approximately 44 mCi 11C-methyl methionine with a specific activity of 3.3 Ci/mmol. Radiochemical purity is greater than 96%. The procedure has been automated so that the preparation can be carried out remotely, thus minimizing exposure of personnel to radiation.

Carbon Radioisotopes↗
PubMed1982

Image analysis in critical care medicine.

Computer techniques have been developed to image, noninvasively, anatomical structure, vessel blood flow, and physiological and biochemical functions, utilizing a number of physical principles. These devices, though costly, appear to provide sufficient diagnostic benefits to warrant their use in some critical care units. The emergence of x-ray, digital subtraction angiography, ultrasound, emission and nuclear magnetic resonance imaging techniques and their medical applications are described. It is shown that the physical variables measured by these techniques are sensitive to disease conditions and, thus, their incorporation in critical care procedures are likely in the future.

Angiography↗
PubMed1982

Brain tumor evaluation using Rb-82 and positron emission tomography.

Positron emission tomography of the brain with 75-sec rubidium-82 obtained from a portable generator (25-day Sr-82 leads to Rb-82) was used to evaluate the integrity of the blood-brain barrier (BBB) in patients with brain tumors. Rubidium is normally excluded from the central nervous system by the intact BBB, but when the BBB is disrupted by a tumor. Rb enters and pools in the extravascular spaces of the central nervous system. Since Rb is also rapidly cleared from the blood, a high tissue-to-blood ratio of the Rb-82 tracer is achieved in regions of BBB disruption after intravenous injection. With dynamic positron emission tomographic imaging, the extravasation of the Rb tracer can be evaluated independent of the intravascular Rb concentration, and very small changes in the BBB permeability can be detected. The results of our studies in eight patients show that this technique is a promising method for evaluation of the BBB integrity in brain-tumor patients.U

Adenocarcinoma↗
PubMed1981

Evaluation of blood-brain barrier permeability changes in rhesus monkeys and man using 82Rb and positron emission tomography.

Dynamic positron tomography of the brain with 82 Rb, obtained from a portable generator [82Sr (25 days) - 82 Rb (76 sec)], provides a means of studying blood-brain barrier (BBB) permeability in physiological and clinical investigations. The BBB in rhesus monkeys was opened unilaterally be intracarotid infusion of 3 M urea. This osmotic barrier opening allowed entry into the brain of intravenously administered rubidium chloride. The BBB opening was demonstrated noninvasively using 82Rb and positron emission tomography and corroborated by the accumulation of 86Rb in tissue samples. Positron emission tomography studies can be repeated every 5 min and indicate that dynamic tomography or static imaging can be used to study BBB permeability changes induced by a wide variety of noxious stimuli. Brain tumors in human subjects are readily detected because of the usual BBB permeability disruption in and around the tumors.

Animals↗
PubMed1981

Nuclear magnetic resonance (NMR) in vivo studies: known thresholds for health effects.

Three sources of harmful health effects from nuclear magnetic resonance (NMR) in vivo techniques have been examined with the following conclusions: (a) Static magnetic fields. Harmful effects on humans and reproducible cellular, biochemical, or genetic effects have not yet been observed at fields less than 2 Tesla (20,000 gauss). (b) Changing magnetic fields. The threshold for effects of induced currents is above that produced from less than 1 to 100 Hz sinusoidal field changes with a maximum field of 5 mT (50 gauss). Waveform, repetition rate maximum B field, and duration of exposure are parameter requiring further study. (c) Radiofrequency (RF) heating. A practical upper level for absorbed power is 4 W/kg in medically important studies of short duration (less than 10 min). For long-term studies, 1.5 W/kg is a reasonable level in low humidity environments. The power absorbed by the subject can be estimated by measuring the RF coil Q before and after the subject is placed in the NMR instrument. Large metal objects will absorb power in proportion to the conductivity of the device or prosthesis.

Animals↗
PubMed1981

A precision flow-controlled Rb-82 generator for bolus or constant-infusion studies of the heart and brain.

A precision flow-controlled rubidium-82 generator has been constructed to deliver 76-sec Rb-82 at either fast or slow flow rates for bolus or constant-infusion studies. A stepping motor drive is interfaced to a microprocessor for pulsed control of flow rate to deliver the saline eluant solution from a large-volume (150 ml) machined pumping syringe through an alumina column that retains the 25-day Sr-82 parent. The generator system delivers 70-90% of the maximum Rb-82 activity in a 20-25 ml bolus elution of 2% NaCl. The Sr-82/Sr-85 breakthrough is 10(-7) - 10(-6). both yield and breakthrough are functions of column length and flow rate. Six separate Sr-82 loadings of the generator were evaluated over a period of nearly 2 yr in studies of myocardial blood perfusion and permeability changes in the blood-brain barrier. Sterility and apyrogenicity of the Rb-82 eluate were maintained during multiple elutions and long-term use of 3-4 mo for each generator loading.

Brain↗
PubMed1980

Emission computerized axial tomography from multiple gamma-camera views using frequency filtering.

Emission computerized axial tomography is achievable in any nuclear medicine department from multiple gamma camera views. Data are collected by rotating the patient in front of the camera. A simple fast algorithm is implemented, known as the convolution technique: first the projection data are Fourier transformed and then an original filter designed for optimizing resolution and noise suppression is applied; finally the inverse transform of the latter operation is back-projected. This program, which can also take into account the attenuation for single photon events, was executed with good results on phantoms and patients. We think that it can be easily implemented for specific diagnostic problems.

Brain↗