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Biomedical subjects

T F Budinger

Publications and source records attributed to T F Budinger.

At least 109 records · Page 6Linked to original sources
PubMed1980

Physical attributes of single-photon tomography.

Physical properties important for assessment of the potentials of emission computed tomography implemented by collimated detector systems include sensitivity, statistical and angular sampling requirements, attenuation compensation, resolution uniformity, and multisection design constraints. The limited angular range and sampling interval of coded aperture methods for longitudinal tomography impose severe limitations on quantitative imaging capabilities. These methods are discussed. Disadvantages of limited angular range are avoided by transverse section devices that have lower sensitivity than comparable positron devices. It is shown here, however, that the sensitivity for a single section device for head transverse section 2 cm thick can be congruent to 200 events sec-1 microCi-1 per axial cm for 2 x 2 cm resolution. This is 40% of that for a well-designed positron system of similar resolution. The problem of attenuation compensation for constant attenuation, as in brain imaging, is well understood and a fast algorithm of the convolution type gives excellent results if angular sampling is over 360 degrees. Though there is a need to move the single-photon detector array over wide angular distances for adequate sampling, dynamic ECT is possible for the measurement of biological washout kinetics of clinical importance, such as clearance studies in brain. Based on physical principles, experiences with low sensitivity devices, and the prospects for devices with sensitivity comparable to positron tomographs, single photon tomography has sound potentials for research and clinical studies of the adult brain and whole body in small subjects. Practical whole-body tomography in adults is limited to nonquantitative lesion detection.

Tomography, Emission-Computed↗
PubMed1979

Physiology and physics of nuclear cardiology.

This chapter is a primer on the physics of radionuclide detection, flow physiology, and methods of in vivo evaluation of myocardial metabolism and intercavitary flow by noninvasive methods of intravenous isotope injection. This summary presents key concepts for the application of currently available instrumentation as well as future directions of nuclear cardiology. 1. Quantitative information is obtained in nuclear cardiology at the cost of high resolution imaging for two reasons: (a) the intrinsic resolution of the detecting systems is limited by available technology, and (b) the statistics required to achieve a high resolution image necessitate doses and imaging times far in excess of those which can be tolerated. Image resolution for both projection images as well as transverse sections are limited to the range of 5 to 20 mm, depending upon the configuration and instrument involved. 2. The second important concept is the fact that nuclear cardiology gives quantitative information regarding the amount of radiopharmaceutical which has accumulated in or is flowing through the cardiovascular system. This information allows one to deduce the dynamics of flow as well as actual metabolic rates. 3. The major emphasis for future work might well lie in the multiple transverse section imaging of the myocardium using both rotating and static devices. The key feature of this approach is the fact that the volume of interest can be localized and actual concentrations of radiopharmaceuticals can be measured by external detection using reconstruction tomography images. 4. Quantitative data on the distribution of a metabolite which accumulates in the myocardium is of little value if regional blood flow is not also known. 5. Finally, it is shown in this chapter that specific volume flow can be evaluated using short half-life isotopes and equations derived from the principle of conservation of mass. In principle it is now possible to obtain quantitative values delineating endo- and epicardial flow for the heart of man without invasive catheterization or high radiation doses. These procedures involve constant inhalation of carbon dioxide labeled with 15O which converts to labeled water and can be used for evaluating myocardial perfusion; bolus injection of 82Rb, a short half-life analogue of potassium, for repeated (every 5 min) imaging of the evolution of myocardial infarction size; evaluation of the accumulation of labeled fatty acids, amino acids, and sugars in the myocarium; presentation of images which reflect the magnitude of ejection fraction; and noninvasive evaluation of cardiac shunts. It is now possible to perform on the same patient during a few hours the following studies of myocardium: cation perfusion evaluation; water perfusion; uptake of fatty acids, amino acids, and glucose; oxygen utilization of the myocardium; and even measurement of the quantity of lung water. We now have the tools and methods to evaluate the in vivo biochemistry of the ischemic, 128 infarcting, repairing, and hypertrophic myocardium.

Blood Flow Velocity↗
PubMed1979

Evaluation and application of alumina-based Rb-82 generators charged with high levels of Sr-82/85.

Generator-produced Rb-82, a 75-sec positron emitter with potential for myocardial blood-flow imaging, was studied with various ion-exchange columns to evaluate the characteristics of alumina as an adsorber for the 25-day Sr-82 parent. Test columns of alumina, Bio Rex 70, and Chelex 100 were loaded with multimillicurie amounts of no-carrier-added Sr-82/Sr-85 (Sr-85 is a production contaminant). The breakthrough of Sr-82/Sr-85, and the yield of Rb-82, were determined for long-term elutions from each column with up to 4 liter of 2% NaCl solution at pH 8 to 9. The breakthrough of Sr-82/85 was 10(-6)-10(-5) from aluminal 10(-6)-10(-4) from Chelex 100 and Bio Rex 70. The effects of eluent flow rate and concentration, and of alumina volume, on the breakthrough and yield were also studied. An improved and automated Rb-82 generator was used for myocardial and brain blood-flow studies in experimental animals and in man; it was equipped with solenoid flow-control valves and five in. of lead shielding for the alumina columns, which were charged with 25-50 mCi Sr-82 (100-150 mCi Sr-85). The Rb-82 generator with alumina column provided up to 20-40 mCi of Rb-82 as often as every 5-10 min with less than 10(-5) breakthrough of Sr-82/85 over the 2- to 3-mo, useful life of the generator.

Aluminum Oxide↗
PubMed1978

Transverse section imaging of mean clearance time.

Transverse sections representing the magnitude of clearance rates or the mean transit time of radionuclide flow through known volumes of interest are computed from angular projections. First the integrated counts for all time intervals at each projection bin for each angle are computed. These modified projection sums are convolved with a filter and backprojected to form an integrated event image. A second image is formed by backprojected the sum over time of the projected values for each angle weighted time. The ratio of the second image to the first image gives a mean clearance time image with high signal to noise and accuracy after thresholding to remove noise in zero-flow regions. The algorithm is verified by computer simulations and has a major benefit in the savings of computational time by a factor of 10 for anticipated clinical studies of brain and kidney blood flow and lung ventilation and perfusion.

Brain↗
PubMed1978

An iodinated catecholamine congener for brain imaging and metabolic studies.

The iodinated O-methylated catecholamine congener, 4-iodo-2,5-dimethoxyphenylisopropylamine (4-I-DPIA), has potential as a new agent for imaging and metabolic studies of the brain and lung. The organ distribution and brain uptake of radioiodine-labeled 4-I-DPIA were studied in the dog and monkey by whole-body scanning, gamma-camera scintigraphy, and organ assay. The brain takes up 2% of the injected dose, with a half-time of 8 sec in the monkey, and the lung takes up 11.8%. An unusual finding was a concentration in the retina, five times that in any other CNS tissue. 4-I-DPIA may have potential in the imaging of normal brain tissues and thereby delineating nonfunctional areas damaged by infarction, trauma, or malignancy, and may also be useful in metabolic studies of catecholamine function. Adequate radioactivity can theoretically be administered with a quantity of 4-I-DPIA 1/10,000 of the pharmacologically active levels. The agent may also find application in lung imaging because of the high pulmonary uptake.

Amphetamines↗
PubMed1978

Quantitative potentials of dynamic emission computed tomography.

Statistical uncertainties in emission computed tomography were simulated in 60 computer studies involving various numbers of events and distributions of activity. Previous studies have shown that for a uniform disc of activity of rms percentage of uncertainty per resolution cell is: 120 X (number of resolution cells)1/4 X (number of events per resolution cell)- 1/2. In this work we examined the more general situation where one or two regions of uniform activity are surrounded by a uniform background, and found that for an equal number of recorded events the uncertainties were reduced when the activity was concentrated in a portion of the field. The empirical relation rms % uncertainty in nt = 120(N)1/4(nt)-3/4, where nt is the number of events in an average target (organ) resolution cell and N is the total number of events recorded, satisfactorily described the relationships between uncertainties, contrast, total number of detected events, and number of resolution cells for all 60 computer studies. By means of this relation, we show the theoretical possibility of gated cardiac imaging with 20% uncertainty in 1 cm X 1 cm regions, and of 1-sec cerebral blood-flow images with 20% uncertainty in 2 cm X 2 cm regions.

Computers↗
PubMed1977

Instrumentation trends in nuclear medicine.

Nuclear medicine instrumentation requires use of various configurations of photon detectors for the purpose of in vivo and in vitro measurements of flow and metabolism. Computed tomography has solved a previous limitation of an ambiguous volume of interest intrinsic to projection images. Selection of instruments involves first, a definition of the medical problem to be solved; then an evaluation of the following characteristics of the candidate instruments: sensitivity, spatial resolution, saturation performance, dead time, uniformity of resolution, uniformity of sensitivity, data processing capabilities, and cost. New developments include dynamic imaging in transverse section with either single photon or positron annihilation photons, and whole-body quantitative imaging of sequential changes in radiopharmaceutical concentration.

Evaluation Studies as Topic↗
PubMed1977

Emission computer assisted tomography with single-photon and positron annihilation photon emitters.

Computed transverse section emission tomography using 99mTc with the Anger camera is compared to positron annihilation coincident detection using a ring of crystals and 68Ga. The single-photon system has a line spread function (LSF) of 9 mm full width at half maximum (FWHM) at the collimator and gives a transverse section reconstruction LSF of 11 mm FWHM with 144 views. The positron ring has a LSF of 6 mm at the center with a transverse section reconstruction LSF of 7.5 mm FWHM. Correction for uniformity of detector response and accurate center of rotation determination is essential in both techniques. The signal-to-noise ratio in a reconstruction is diminished by a factor of 1.2 x (number of resolution elements)1/4 over that expected from the average number of events per resolution element. Attenuation compensation causes more noise to appear in the center than the edge for both modes and an average increase in uncertainty of 30%. The effects of attenuation result in more loss of data for positron coincidence imaging than for single-photon imaging even at energies of 80 keV. For a 20-cm cylinder imaged in transverse section, only 20% of the positron annihilation events are not scattered; however, at 140 keV, 40% of the photons are not scattered. The relative crystal efficiency gives single-photon imaging an advantage of 5. On the other hand, the solid angle advantage of positron photon coincidence imaging is about 100 for the comparisons of this paper. Taking these factors into account, we find positron-computed section imaging has a tenfold increase in sensitivity over multiple-view imaging with the scintillation camera, which gives multiple sections but requires camera or patient rotation.

Elementary Particles↗
PubMed1977

Three dimensional imaging of the myocardium with radionuclides.

Transverse sections of the distribution of 129Cs and 201Ti in the human myocardium were obtained using 36 and 72 views of the thorax with a large field of view Anger camera. The cardiac cycle was divided into 100-msec intervals to obtain motion images of an average cycle of the beating heart. At least 300,000 events must be detected for each cardiac phase of each section for quantitative work. Over 8 million events from the upper thorax must be accumulated in gated studies if three or more sections are obtained for 8 intervals of 100 msec to 150 msec.

Animals↗
PubMed1977

Apollo-Soyuz light-flash observations.

While dark adapted, two Apollo-Soyuz astronauts saw eighty-two light flash events during a complete 51 degrees orbit which passed near the north magnetic pole and through the South Atlantic Anomaly. The frequency of events at the polar parts of the orbit is 25 times that noted in equatorial latitudes and no increased frequency was noted in the South Atlantic Anomaly at the 225-km altitude. The expected flux of heavy particles at the northern and southern points is 1-2 min-1 per eye, and the efficiency for seeing HZE particles which were below the Cerenkov threshold is 50%.

Arctic Regions↗
PubMed1977

Cyclotron-produced Zn-62: its possible use in prostate and pancreas scanning as a Zn-62 amino acid chelate.

Zinc-62 is a positron emitter that localizes in pancreas, prostate, and liver. Cyclotron-produced Zn-62 was separated by column chromatography and evaluated in vivo as the chelate of five amino acids and also as 62ZnCl2. Tissue-distribution studies were done in normal animals from 0.7-23 hr after intravenous administration. Pancreas-to-liver ratios (per gram) of about 1.0 were found at 1.5 hr in studies on rats, dogs, and monkeys. Pancreas was as difficult to separate from liver in Zn-62 (amino acid) images as in [75Se] selenomethionine images. Some studies were done with Zn-65 to determine the effects of carrier zinc and molar ratios of ligand. The highest ratio of pancreas to liver in these studies was 1.44. This uptake ratio decreases with increasing amounts of histidine, but the ratio is increased by adding carrier zinc because there results a decrease in liver uptake and no change in the pancreas uptake. There is sufficient specificity of pancreas and prostate uptake to make feasible emission computed tomography with Zn-62.

Amino Acids↗
PubMed1977

Rubidium-82 generators for imaging studies.

Strontium-82, produced by spallation reaction with medium-energy proton beams, was used to evaluate Bio-Rex 70 and Chelex-100 ion-exchange resins for use in a compact Rb-82 generator. Adsorption of Sr-82 to the resin column, Rb-82 elution yields, Sr breakthrough, and 82Rb-Sr separation factors were determined for newly prepared columns and for longterm elution conditions. Separation factors of 10(7) to 10(8) were obtained with 2% NaCl elutions from Bio-Rex 70 resin columns while the separation factors was about 5 X 10(4) with the Chelex-100 resin column.

Evaluation Studies as Topic↗
PubMed1977

Thallium-201 for medical use. Part 3: Human distribution and physical imaging properties.

Studies were undertaken to determine the biologic distribution of thallium-201 in man. The disappearance from the blood is extremely rapid and intracellular deposition is nearly immediate. The biologic half-time of thallium was measured by both the Brookhaven whole-body counter and the Donner whole-body scanner, with excellent agreement. The effective whole-body half-time of thallium-201 is about 57 hr. Concentration of activity was seen in the heart, kidneys, large bowel, and thyroid. The whole-body radiation dose is 0.21 rads/mCi.

Animals↗