No abstract available

No abstract available

[en] The acute hemodynamic effect of intravenous administration of polystyrene microspheres was investigated and correlated with their distribution pattern and kinetics. Microspheres of three diameters (3.4, 7.4, and 11.6 micrometer) were administered. The 7.4- and 11.6-micrometer diameter microspheres were filtered by the pulmonary capillary network following intravenous administration, the majority during the first pass. There was no significant hemodynamic effect following administrations of the 7.4- and 11.6-micrometer diameter microspheres in doses as high as 3.0 X 10(9) and 6.1 X 10(8) respectively (total cross-sectional area of 1.3 X 10(11) and 6.4 X 10(10) micrometer2, respectively). Intravenous administration of 3.4-micrometer diameter microspheres produced significant dose-dependent systemic hypotension and depression of myocardial performance at dosages as slow as 1.0 X 10(10) (cross-sectional area of 9.1 X 10(10) micrometer2). These differences in acute hemodynamic effect from the 7.4- and 11.6-micrometer diameter microspheres may be due to the differences in distribution kinetics and fate of the 3.4-micrometer diameter microspheres, which readily pass through the lungs to the spleen. Although elimination of the smaller spheres from the blood during the first 6-8 min was rapid, i.e., t 1/2 . 1.62 and 1.72 min from the venous and arterial blood circulation, respectively, levels of 10(3) spheres/g of blood were present in the circulation for greater than 1 hr. These findings must be considered in the planning of intravenous administration of microspheres as a drug delivery system to target organs

[en] Separate abstracts were prepared for the 21 papers in the proceedings of the Health Physics Society 1981 Summer School on Reactor Health Physics

[en] A new method for optimizing the design of multi-aperature parallel-hole collimators for the gamma scintillation camera is presented. The method takes into account the frequency spectrum of a plane source object distribution as well as the energy of the radiation. A frequency dependent statistical figure of merit was calculated and combined with a weighted object distribution frequency spectrum to obtain an objective function which, when maximized, yielded the optimum collimator design according to the chosen criteria. The optimization was performed by means of a sequential pattern search technique. The results showed a positive correlation between the objective function and an experimental performance index evaluated for existing collimators. The optimal designs obtained by maximizing the objective function, under the assumption of no scatter within the source, exhibited somewhat higher sensitivity and lower resolution than the commercial low energy collimators tested. It was concluded that much of the resolution capability of very high resolution collimators is unused because of the limitation imposed by the intrinsic resolution of the detector assembly. (author)

No abstract available

[en] The calculation of beta ray dose to the skin due to I-131 contamination includes some assumptions that leads to uncertainties in the evaluation. Because of uncertainties in isotope distribution, two methods have been employed using: (a) the thin infinite-plane source model of Loevinger, et al, and (b) the MIRD model using the S factors for electrons and beta rays. The thin-plane source model has been applied to the case of a surface-plane source distribution realizing that there will be an error due to surface boundary effects. This model has been compared to the MIRD method which overestimates the dose to the skin (i.e., the assumption made in the calculation is that all the beta ray energy is absorbed, which is not the actual case). The surface-plane source calculation has been extended to a homogeneous distribution by assuming uniformly distributed thin-plane sources throughout the skin volume. The data indicate close agreement with the MIRD model. In addition, exponential distributions have been calculated which approach the surface boundary case for large absorption rate constants. The point source data of Berger is presently being investigated to determine whether it can be extended to a plane source geometry for an additional comparison

[en] A comparison of β-ray dose to the skin due to I-131 contamination has been investigated using the empirical infinite-plane thin-source model of Loevinger and the MIRD method utilizing the S factors for β-rays and electrons. The Loevinger model, which was originally developed for the calculation of dose as a function of distance from a plane source, was extended to a uniform activity distribution throughout the skin such that comparisons could be made between the two methods. The results are in close agreement. The advantage of the extended Loevinger model in the present investigation is that one is able to compute a distribution of dose throughout the skin. The model has also been extended to linear and exponential activity distributions. All distributions were used with a modified reference man incorporating the recommendations made by the ICRP for the evaluation of skin dose

[en] Pulmonary edema induced by injections of oleic acid was demonstrated using ¹¹¹In-chloride lung/heart image in five anesthetized dogs. The anesthetized dogs were positioned under a gamma camera interfaced to a computer. After ¹¹¹In-chloride IV injections, dynamic data were recorded at 1 frame/min before and after induced pulmonary edema. The computer generated the curve of the lung-to-heart activity ratio; the ratio rose from 0.5-0.6 at baseline to 0.85-1.5 at th end of the study in the dogs. At the end of each study, the removed lungs demonstrated edematous fluid, and a few red blood cells were seen in the alveoli. The results indicating pulmoinary edema exhibited in the ¹¹¹In-chloride lung-to-heart ratio obtained froma computerized gamma camera were compatable with the pathological results. Since ¹¹¹In-chloride instantly binds to plasma transferrin, an excellent intravascular imaging agent, leakage of this tracer into alveoli indicates loss of membranous wall competence. Pulmonary edema, as in the adult respiratory distress syndrome, is sometimes difficult to diagnose; and this ¹¹¹In-chloride lung-to-heart imaging technique may be potentially useful. (orig.)