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PubMed1978

Post-mortem migration of bone-seeking radionuclides in the rat and rabbit and its effect on estimates of bone uptake.

1. The continued uptake of 18F, 85Sr and 47Ca by bone after death has been studied in rats and rabbits after aortic injection followed by quick killing, a period of recirculation of tracer before death, and perfusion of the carcase. In each case an approximately linear increase of bone radioactivity was observed during a period of 1 h at about the same rate. The proportionate increase depended on the initial concentration of bone-seeking nuclide, ranging from a factor of 1.5 to 4.5. Boiling the carcase did not increase the migration rate. 2. Delay between death and dissection may therefore lead to spuriously high bone concentrations of these radionuclides, leading to over-estimates of bone uptake, extraction ratio or bone blood flow.

Animals↗
PubMed1975

Dimensions of the human eye relevant to radiation protection.

An attempt has been made to clarify the two most important issues relevant to personal eye dosimetry. This involves the identification of the cells which are most at risk from radiation and the specification of their position in the eye. A survey of the radiobiological literature concerning animals and humans shows that the epithelial cells in the equatorial region of the lens are those which are involved in radiation cataract induction. The depth of these cells has been evaluated in the human eye by means of geometrical construction. The relevant dimensions have been determined from a survey of published anatomical data and supplemented by new data obtained by slit-image photography. In a normal adult population (20-65 years) the minimum depth of the incriminated cells is 2.3 plus or minus 0.4 mm; the upper and lower values are associated with young and old subjects respectively. Approximate calculations for isotropic 90Sr/90Y and 106Rh beta-radiation fields indicate that a planar dosemeter, which integrates the tissue dose between depths of 2.5-3.5 mm, should give a reasonable measure of the mean equatorial dose for the variety of eye and irradiation geometries likely to be met during a life-time exposure. The long established, but tentative, value of 3 mm for the effective depth of the lens is thus confirmed.

Adult↗
PubMed1980

The perturbation correction factor of ionisation chambers in beta-radiation fields.

In determining the absorbed dose in a solid medium by means of gas-filled ionisation chambers, the perturbation of the radiation field by the chamber needs to be taken into account. So far, an appropriate correction factor has neither been calculated nor measured for beta-radiation. This work describes its experimental determination for an extrapolation chamber and beta-radiation fields of 147Pm, 204Tl, and 90Sr + 90Y. The results show that the correction factor may be assumed to be the product of a shield factor and a scatter factor the magnitudes of which depend on the chamber geometry and the radiation field. The change of the perturbation correction factor with phantom depth is important for the measurement of depth dose curves. This is demonstrated by an example.

Electrons↗
PubMed1975

Changes in regional coronary blood flow with hypertonic mannitol in conscious dogs.

Systemic haemodynamics and regional myocardial blood flow responses to hypertonic mannitol were studied in 10 conscious and 23 anaesthetized dogs. Mannitol infusion significantly increased regional myocardial blood flow in the conscious, intact dogs. Mannitol increased total coronary flow 20% in anasethetized animals compared to 80% in the awake ones. In both groups mannitol exerted a significant positive inotropic effect as evidenced by increases in maximal LV dp/dt and dp/dt/p. These studies have also demonstrated that the intact conscious dog that has not received any sedation has an inner:outer wall left ventricular flow ratio greater than 1-0.

Anesthesia↗
PubMed1985

Reduction of 85Sr, 137Cs, 131I and 141Ce retention in rats by simultaneous oral administration of calcium alginate, ferrihexacyanoferrate(II), KI and Zn-DTPA.

The effect of simultaneous oral administration of a mixture of calcium alginate, ferrihexacyanoferrate(II) and KI and of the chelating agent zinc diethylenetriaminepentaacetate (Zn-DTPA) on the retention of radioactive Sr, Cs, I and Ce was investigated in 7-week-old female rats. The respective antidotes were administered in food during the first three days of the experiment and the radionuclides were administered on the second day of the experiment. The radionuclide retention was determined in the whole body, carcass, gut, liver, kidneys and respective critical organs six days after oral administration of 85Sr, 137Cs, 131I and intraperitoneal administration of 141Ce and one day after oral administration of 141Ce. Simultaneous oral administration of the four therapeutic agents reduced the retention of radioactive Sr, Cs and I administered orally and Ce applied intraperitoneally. Zn-DTPA did not diminish efficacy of antidotes from the mixture nor did the mixture significantly alter the effect of Zn-DTPA. Simultaneous oral administration of calcium alginate, ferrihexacyanoferrate(II), KI and Zn-DTPA might present a convenient method for delayed therapy especially in cases of prolonged increased environmental exposure to several radionuclides.

Administration, Oral↗
PubMed1996

Transfer, pathways, enrichment, and discharge of 137Cs and 90Sr in the pulp industry.

Natural and artificial radionuclides are transferred from terrestrial ecosystems via the forest industry to coastal sea water. The material processed, i.e., wood, fresh water, and bark, have low levels of radionuclides, but large amounts of raw materials are processed annually. Thus the annual flux of radionuclides is substantial. The purpose of this investigation was to study transfer, redistribution, enrichment, and discharges of 137Cs and 90Sr in pulp industry employing the sulphate process. 137Cs and 90Sr were measured by means of Ge-detectors and a low level liquid scintillation spectrometer, respectively. 137Cs was highly enriched in the recovering process for sodium, while 90Sr was enriched in the recovering system for calcium compared to concentration levels in raw materials. The concentrations of 137Cs and 90Sr in bark were almost ten times the concentration level in conifer wood. No 137Cs or 90Sr could be identified in atmospheric discharges from the combustion processes. The products contained very low levels of these radionuclides. Only 5% of the annual input of 137Cs and 90Sr were found in the products. Discharges of radionuclides from this particular pulp production plant is nearly 40% of the annual 137Cs and 90Sr input. The contribution of 137Cs and 90Sr to coastal seawater is probably of minor importance providing that wood or fresh water from highly contaminated areas are not utilized.

Cesium Radioisotopes↗
PubMed2001

Dosimetric effect of source centering and residual plaque for beta-emitting catheter based intravascular brachytherapy sources.

Catheter-based radiation delivery systems employing both beta-particle and gamma-ray emitters are currently being investigated for their efficacy in addressing restenosis following percutaneous coronary intervention (PCI). The dosimetric consequences of source centering within the arterial lumen and presence of residual plaque are potentially important issues for the uniform delivery of dose to the arterial tissue. In this study, we have examined the effect of source centering on the resulting dose to the arterial wall from clinical intravascular brachytherapy sources containing 32P and 90Sr/Y90. Monte Carlo simulations using the MCNP code were performed for these catheter-based sources with offsets of 0.5 mm and 1 mm from the center of the arterial lumen in homogenous water medium as well as in the presence of residual plaque. Three different positions were modeled and the resulting dose values were analyzed to assess their impact on the resulting dose distribution. The results indicate a variation ranging from -40% to +70% for 32P source and -30% to +50% for 90Sr/90Y at a radial distance of 2 mm from the center of the coronary artery, relative to the dose from a centered source, for a 0.5 mm offset. The variation for a 1 mm offset ranges from -65% to +182% for 32P source and to -50% to +140% for 90Sr/90Y. A concentric residual plaque layer was also modeled so as to assess the combined influence of offset and residual plaque on the dosimetry. Finally the effect of cardiac motion and its potential impact on catheter position and hence the dose distribution is also examined by considering two separate cases of catheter displacement. The results indicate that dose variations range between -28% to +91% when it is assumed that cardiac motion causes catheter movement during coronary lesion irradiation.

Beta Particles↗
PubMed2002

Application of imaging-derived parameters to dosimetry of intravascular brachytherapy sources: perturbation effects of residual plaque burden.

The dosimetric effect of geometric and material heterogeneities on intravascular brachytherapy dose delivery has been studied recently. Residual plaque within the coronary vessel appears to have an impact on the uniform delivery of radiation dose to the arterial tissue. In this study, we have examined the effect of residual plaque burden and post-PCI (percutaneous coronary intervention) plaque configuration on the dose to the arterial wall from clinical intravascular brachytherapy beta-emitting sources containing 32P and 90Sr/90Y. Monte Carlo simulations using the MCNP4B code were performed for these catheter-based sources with residual plaque burden ranging between 25% and 50%. The residual plaque burden values were derived from post-PCI data provided in several recent clinical studies. Dose calculations were performed for three different values of plaque density (1.45 g cm(-3), 2.20 g cm(-3), and 3.1 g cm(-3)) and three different plaque morphologies for the same residual plaque burden. The dose perturbation factor (DPF), defined as the ratio of dose at 2 mm radial distance for a given case to the dose at the same radial distance in homogeneous water medium, was determined for each of the three different plaque densities. The range of DPF values was 0.81-1.01, 0.62-0.99, and 0.41-0.97 for different plaque densities for the 32P source. Corresponding DPF values for the 90Sr/90Y source were 0.90-1.01, 0.84-1.01, and 0.62-1.01. The results indicate the need for accurate assessment of post-PCI clinical measurements such as minimal lumen diameter and residual plaque burden and incorporation of these values into dose calculations.

Brachytherapy↗
PubMed1999

Variation in oncologic opinion regarding management of metastatic bone pain with systemic radionuclide therapy.

UNLABELLED: The objective of this study was to determine whether there is consistency of opinion regarding the management of metastatic bone disease pain among medical oncologists who are given the option of using systemic radionuclide therapy (89Sr, 153Sm). METHODS: One hundred board-certified medical oncologists were given a brief clinical summary of three patients with metastatic cancer. Management options included oral, parenteral and transdermal delivery forms of opioid analgesics; external beam irradiation; and systemic radionuclide therapy. The oncologists rated, in whole numbers from 1 (most appropriate) to 10 (least appropriate), their opinions on the appropriateness of each proposed intervention for each patient. RESULTS: Systemic radionuclide therapy was perceived consistently as having low appropriateness for palliation of metastatic bony pain compared with opioid analgesics. A slight increase in appropriateness for systemic therapy was indicated for the patient with widespread metastatic disease, who, on the basis of literature reports, was unlikely to benefit from such therapy. The oncologists rated the appropriateness of systemic therapy as low in the patient with limited early disease, in which the literature indicates the greatest benefit will be derived from such intervention. CONCLUSION: Referring oncologists perceive the appropriateness of systemic radionuclide therapy as low. Their perception of its appropriateness increases with extent of disease. As a result, this palliative option is underutilized or used in less-than-optimal disease settings.

Aged↗