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At least 19 recordsLinked to original sources
PubMed1990

Ion exchange chromatography on a new form of tin dioxide for the isolation of strontium radioisotopes from fission products: an application to milk samples.

An amorphous, partially-reduced tin dioxide, having properties of an inorganic exchanger, was tested for application to fission product separations. Due to the good sorption of both strontium and barium the application of the exchanger to radiostrontium isolation from fission product mixtures is subject to important restrictions. An application to 90Sr determination in milk is proposed.

Animals↗
PubMed1975

Influence of perfusion pressure and heart rate on local myocardial flow in the collateralized heart with chronic coronary occlusion.

We studied the influence of controlled changes in perfusion pressure and heart rate on the regional distribution of myocardial flow in normal dogs and in dogs with multiple chronic coronary artery occlusions but without infarctions. Local myocardial blood flow was determined with the tracer microsphere technique. By stepwise altering of systemic blood pressure during maximal vasodilation classical pressure flow relations were obtained. One week after complete chronic occlusion a functionally and anatomically well-defined compartmentation of blood flow was found. The dilatory reserve is clearly compromised not only in the collateral-dependent myocardium but also in the apparently normal myocardium which delivers collateral flow. An "arterio-arterial shunting" mechanism is shown to exist. Several months after coronary occlusion, regional mycoardial flow is still nonhomogeneous. Although the coronary dilatory capacity of the collateralized myocardium is nearly normal, that of the normal myocardium is found to be higher than normal. Vessel growth in both areas is discussed as being responsible for this phenomenon. Right ventricular pacing during maximal vasodilation produces a flow decrease to the endocardial muscle layers in normal dogs, while the epicardial flow is unchanged. One week after complete chronic coronary occlusion pacing during maximal vasocilation reduces the dilatory capacity in the collateralized areas to such an extent that the supplementary increase in myocardial oxygen demand will induce ischemia because of the compromised oxygen supply.

Animals↗
PubMed1979

Radioisotope therapy in bone and joint disease.

The short range tissue destruction of beta-emitting radioisotopes can be utilized in painful metastatic disease of the skeleton by employing a radionuclide that is specifically metabolized in or adjacent to these lesions. Sodium phosphate P 32 has been used for this purpose for the past 25 yr. It uptake in skeletal tumor and in osteoblastic new bone adjacent to tumor can be markedly increased by pharmacologic stimulation using androgenic steroids, or during rebound deposition after a course of parathyroid hormone. Although efficacy in terms of subjective pain relief is high, more objective signs of success are often lacking, and survival, while more confortable, is not prolonged. Marrow depression is the most significant side effect. A beta-emitting, bone-seeking isotope, 89Sr, may have a better therapeutic/toxic ratio, and should receive further trial. Radiation-induced necrosis has also been applied, though more hesitantly, to the proliferative, destructive, but nonmalignant synovium in rheumatoid disease. Here, a number of colloidal preparations, most commonly 198Au, have been employed. Again, relief of symptoms, particularly recurrent joint effusions, is quite high, although the basic disease process is not reversed. The major hazard here appears to be leakage of material to regional lymph nodes, resulting in irradiation of circulating lymphocytes. Although chromosomal damage can be detected when such cells are then cultured, the actual consequences of this, if any, are not presently known. Both shorter-lived (165Dy) and longer-lived (32P) larger-size colloids are being evaluated, which may prove safer in this regard than 198Au.

Bone Marrow↗
PubMed1976

The dosimetry of radioisotopes incorporated in bone using cavity ionization theory.

Cavity ionization theory is applied to the dosimetry of bones incorporating beta- and gamma-emitting radioactive isotopes. The assumptions inherent in different theoretical approaches to bone dosimetry are reviewed and compared with those adopted in cavity theory. In presenting the theory attention is given to the effects of electron and photon attenuation and to the absence of electronic equilibrium which may occur in bone. The mean marrow dose is calculated for a range of cavity size and gamma-ray energies and for a beta-ray emitter. The mean marrow dose and the mean endosteal dose are calculated for a human lumbar vertebra and some comparisons made with the results of other workers. It is concluded that cavity theory provides a useful approach to the dosimetry problems of bone-seeking beta- and gamma-ray radioactive isotopes.

Adult↗
PubMed1976

Calculated beta-ray dose factors for trabecular bone.

Mean dose factors have been calculated for those tissues in bone that are relevant to the induction of late irradiation effects; namely, red bone marrow and endosteal tissues lining trabecular bone surfaces. The calculations are based on a Monte Carlo computer method for beta-emitting radionuclides which are distributed uniformly throughout the volume of mineralized bone. Results are given for the radionuclides 14C, 45Ca, 22Na, 18F, 32P, 90Y and 90Sr+90Y (all considered for this purpose as volume-seekers) for seven bones from the adult human skeleton and calculations are also presented of average skeletal dose factors. Where possible, results are compared with those derived from other methods based on simple geometrical models.

Adult↗
PubMed1986

The single-passage extraction of 18F in rabbit bone.

The only clinically applicable method for the quantitative measurement of blood flow to the skeleton which has so far been developed rests on the assumption that the initial extraction of the bone-seeking isotope 18F from blood by bone is known and constant. Previous work to measure the single-passage extraction ratio of this isotope in rabbit bone has been criticised, so a novel technique has been developed in which isotope recirculation cannot occur. In addition, the post mortem uptake of isotope from surrounding tissues and the vascular tracer content of the bone can be monitored. The apparent extraction ratios of two bone-seeking isotopes, 85Sr and 18F, were measured in nine animals, and extrapolated to the time of death from both the time at which dissection of the bones began (giving a maximum value) and the time at which it ended (giving a minimum). Mean blood flow to the femur was 0.562 ml min-1 (SD = 0.170, n = 15) and mean blood flow to the tibia was 0.290 ml min-1 (SD = 0.140, n = 12). Statistical analysis of the results showed that there were significant differences in the extrapolated ratio between animals and significantly higher extraction of isotope in the tibia than in the femur. There was no significant difference between the extraction of 85Sr and that of 18F. The best estimate of the single-passage extraction ratio of 85Sr and 18F which can be made, therefore, is that in rabbit femur it is 0.88 (SE 0.04) and in the rabbit tibia it is 1.08 (SE 0.04). Post mortem uptake of isotope increases the apparent extraction ratio by about 1% per minute.

Animals↗