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At least 469 records · Page 26Linked to original sources
PubMed1998

Rhenium-188--a generator-derived radioisotope for cancer therapy.

Rhenium-188 (188Re) is an important therapeutic radioisotope which is obtained on demand as carrier-free sodium perrhenate by saline elution of the tungsten-188/rhenium-188 generator system. With a half-life of 16.9 hours and emission of a high energy beta particle (maximal energy of 2.12 MeV) and a gamma photon (155 keV, 15%) for imaging, 188Re can be provided at reasonable costs for routine preparation of radiopharmaceuticals for cancer treatment.

Half-Life↗
PubMed2005

Distribution of radiation in synovectomy of the knee with 166Ho-FHMA using image fusion.

BACKGROUND: Radiation synovectomy is an effective technique for the treatment of chronic synovitis in patients with rheumatoid arthritis (RA), and is an alternative for surgical synovectomy. Holmium ferric hydroxide macroaggregates (166Ho-FHMA) is suitable for radiation synovectomy, especially because it emits high-energy beta particles and a smaller proportion of low-energy photons that are suitable for gamma-camera imaging. OBJECTIVE: The aim of this study was to develop a method to fuse 166Ho-FHMA single photon emission computed tomography (SPECT) and magnetic resonance (MRI) images, to show the distribution of 166Ho-FHMA inside the joint with images that localize synovitis. METHODS: The knees of 6 patients with RA were treated with 166Ho-FHMA. (99m)Tc-human immunoglobulin ((99m)Tc-HIG) SPECT images and MRI images were taken before 166Ho-FHMA injections. 166Ho-FHMA SPECT images were taken 4, 28, and 40 hours after injections. SPECT and MRI images were merged using a specific image fusion method, called mutual information algorithm, to study associations between anatomical and metabolic information from these images. RESULTS: Fusion of SPECT and MRI images indicated that intensity of radioactivity was associated with the amount of synovitis. Activity distribution of 166Ho-FHMA could be registered using anatometabolic images. CONCLUSIONS: A new method to fuse the distribution of radiation in the synovectomy of the knee was developed using SPECT/MRI image registration. Image registration of SPECT and MRI can be used to determine the activity distribution of radioisotopes in relation to synovitis.

Female↗
PubMedDate not supplied

Radiolabeled microorganisms: comparison of different radioisotopic labels.

Radioactively labeled microorganisms are very useful in assessing the in vitro phagocytic capability of human granulocytes and macrophages. Since microorganisms contain amino acids and nucleic acids, they can be radiolabeled by addition of radioactive amino acid and/or nucleic acid components to the culture medium. The isotopes 3H, 14C, 32P, 35S, and 75Se-have been used for bacterial radiolabeling. All of these commonly used isotopes with the exception of 75Se are beta emitters; 75Se is a gamma emitter. The half-lives of these isotopes vary from 14 days for 32P to 5,730 years for 14C. Because of the differences in their physical properties, they pose very different handling problems and require different kinds of safety precautions. In the event of either external or internal contamination, beta emitters deliver a larger localized radiation dose than do gamma emitters. In the case of internal contamination, the radiation dose increases with increases in the half-life of the radioactive isotope. Gamma radiation, on the other hand, is more penetrating than are beta particles and thus a gamma emitter requires appropriate shielding. Both the cost and the special problem of manipulation associated with these radioactive chemicals should be carefully considered before deciding which radioisotope is preferable for the labeling of microorganisms in the laboratory. In spite of the limitations of 75Se as a nonphysiologic element, it offers the simplest methods of handling among the isotopes considered in this review.

Bacteria↗
PubMed1988

Thyroid cancer after diagnostic doses of iodine-131: a retrospective cohort study.

The incidence of thyroid cancer was evaluated in 35,074 patients examined for suspected thyroid disorders between 1951 and 1969 with an average of 1.92 megabecquerel [(MBq) 52 microCi] of 131I. The radiation dose to the thyroid gland was, on the average, approximately 0.5 Gy. The mean age at the time of examination was 44 years; 5% were under age 20. Patients were followed for an average of 20 years. Record linkage with the Swedish Cancer Register identified 50 thyroid cancers occurring 5 years or more after the initial 131I examination, in contrast to 39.4 expected based on general population rates [standardized incidence ratio (SIR) = 1.27, 95% confidence interval = 0.94-1.67]. Risk was highest among males (SIR = 2.70, n = 10), patients followed 5-9 years (SIR = 2.22, n = 23), and patients receiving more than 74 microCi or 2.74 MBq of 131I (SIR = 2.04, n = 17). However, these observations were confounded by the fact that patients examined for a suspected thyroid tumor received the highest 131I exposures and were at highest overall risk (SIR = 2.77, n = 34). Patients given 131I for reasons other than a suspected tumor were not at increased risk (SIR = 0.62, n = 16). Patients anticipated to be at highest risk, i.e., women (SIR = 1.12, n = 40) and those observed for 10 years or more (SIR = 0.93, n = 27), showed no evidence of a dose response. Overall, these data provide little proof that 131I is carcinogenic in humans and support the notion that the carcinogenic potential of internal 131I beta particles might be as low as four times less than external x rays or gamma rays.

Adolescent↗
PubMed2001

Internal dosimetry for inhalation of hafnium tritide aerosols.

Metal tritides with low dissolution rates may have residence times in the lungs which are considerably longer than the biological half-time normally associated with tritium in body water, resulting in long-term irradiation of the lungs by low energy beta particles and bremsstrahlung X rays. Samples of hafnium tritide were placed in a lung simulant fluid to determine approximate lung dissolution rates. Hafnium hydride samples were analysed for particle size distribution with a scanning electron microscope. Lung simulant data indicated a biological dissolution half-time for hafnium tritide on the order of 10(5) d. Hafnium hydride particle sizes ranged between 2 and 10 microns, corresponding to activity median aerodynamic diameters of 5 to 25 microns. Review of in vitro dissolution data, development of a biokinetic model, and determination of secondary limits for 1 micron AMAD particles are presented and discussed.

Aerosols↗
PubMed2005

Developing instruments for measurement of plutonium activity in the environmental samples in the case of radiation accident.

According to the Russian norms, the permissible specific activity of 239Pu in the air and water are the lowest. Still the problem of low (compared to permissible) Pu activity measurement for environmental samples arises, for instance, in the case of radiation accident during transportation or storage of excess weapons-grade plutonium transferred to the civil sphere of utilisation. The base method of Pu activity measurement is alpha spectrometry by using silicon detector. A new model of alpha spectrometer, based on silicon surface-barrier detector with background level less than 1-3 pulses per day has been developed. A simple unfolding method for the determination of Pu activity of samples with various thickness based on alpha spectrum measurement has been also developed. L-X photon detection is also used for reducing the measurement threshold of Pu activity determination. A method based on detecting L-X photons of Pu, excited by X rays and beta particles, is applied for further reducing the threshold.

Alpha Particles↗
PubMed2006

Bystander responses in three-dimensional cultures containing radiolabelled and unlabelled human cells.

Research on the radiation-induced bystander effect has been carried out mainly in 2-D tissue culture systems. This study uses a 3-D model, wherein apparently normal human diploid fibroblasts (AG1522) are grown in a carbon scaffold, to investigate the induction of a G(1) checkpoint in bystander cells present alongside radiolabelled cells. Cultures were simultaneously pulse-labelled with (3)H-deoxycytidine ((3)HdC) to selectively irradiate a minor fraction of cells, and bromodeoxyuridine (BrdU) to identify the radiolabelled cells. After thorough washing of cultures, iododeoxyuridine (IdU) was administered to detect proliferating bystander cells. The cultures were harvested at various times thereafter, and cells were reacted with two monoclonal antibodies specific to IdU/BrdU or BrdU, respectively, stained with propidium iodide, and subjected to multi-parameter flow cytometry. Cell-cycle progression was followed in radiolabelled cells (BrdU(+)) that were chronically irradiated by low energy beta particles emitted by DNA-incorporated (3)H, and in unlabelled bystander cells (BrdU(-)) by a flow cytometry based cumulative labelling index assay. As expected, radiolabelled cells were delayed, in a dose-dependent manner, in G(2) and subsequently G(1). No delay occurred in progression of bystander cells through G(1), when the labelled cells were irradiated at dose rates up to 0.32 Gy h(-1).

Bystander Effect↗
PubMed1990

Considerations for imaging Re-188 and Re-186 isotopes.

Re-186 and Re-188 have been suggested for radioimmunotherapy because of their energetic beta particles, imageable gamma photons, and chemical properties similar to technetium. Because of this potential, these isotopes were evaluated before in vivo imaging was attempted. It was found that low-abundance, high-energy gamma photons present in these rhenium isotopes require a medium-energy collimator to yield optimal image resolution and count rate, which are critical factors in the performance of preliminary imaging studies on patients for antibody imaging and therapy.

Humans↗
PubMed2001

Rhenium-188 HEDP to treat painful bone metastases.

PURPOSE: Rhenium-188 hydroxyethylidine diphosphonate (HEDP) is a new and attractive radiopharmaceutical that localizes in skeletal metastases and emits beta particles that may be therapeutically beneficial. In this study, the therapeutic efficacy of Re-188 HEDP was investigated in an uncontrolled initial trial of 61 patients with different types of advanced cancer for the palliation of painful bone metastases. MATERIALS AND METHODS: Sixty-one patients with painful bone metastases of lung, prostate, breast, renal, rhinopharyngeal, and bladder cancers were treated with 1.1 GBq (31 mCi) to 6.9 GBq (188 mCi) Re-188 HEDP. After treatment, the patients were followed at weekly intervals for the first 2 months and monthly thereafter for as long as 1 year. Hematologic function tests were also performed before and after treatment for 6 weeks. Pain responses were scored according to a three-point pain-rating scale as complete, significant, and minimal. RESULTS: Prompt and significant relief of bone pain occurred in 80% of patients overall. Of the specific tumor types, pain relief was achieved in 77% of patients with lung cancer, in 80% with prostate cancer, in 83% with breast cancer, in 100% with bladder cancer, in 50% with renal cancer, in 50% with rhinopharyngeal cancer, and in 87% of patients with other tumor types, with no severe side effects or hematopoietic toxicity. CONCLUSION: This large clinical trial verified that Re-188 HEDP is a useful radiopharmaceutical agent to treat painful bone metastases from various tumor types.

Bone Neoplasms↗
PubMed1985

Radiological sampling and analytical methods for National Primary Drinking Water Regulations.

Radiological sampling and analysis performed under the National Interim Primary Drinking Water Regulations were evaluated for the U.S. Environmental Protection Agency (EPA) Office of Drinking Water to consider whether any changes should be recommended. The authors reviewed the analytical screening scheme; sample collection, storage and analysis procedures; selection of analytical methods; reliability of results; and possible future needs. The main problem in the program has been dependence on a screening scheme of gross alpha-particle activity measurement and 226Ra analysis for predicting elevated 228Ra levels to determine compliance with the maximum contaminant level (MCL) for Ra. In some aquifers, 228Ra levels have been found to be unrelated to 226Ra levels. Several alternatives are discussed to eliminate this problem. A secondary problem is that the measurement for assuring compliance with the MCL for gross alpha-particle activity minus Ra, Rn and U uses chemical U analysis and assumes equilibrium of 238U and 234U. Because some ground waters are known to be at disequilibrium, radiometric U analysis is needed for those gross alpha-particle activities and chemical U values that could result in an erroneous conclusion relative to the MCL. In addition, studies were recommended for determining analytical uncertainties and assuring reliable sampling and sample maintenance; improvements in the system for accepting methods were suggested; and methods were identified for several radionuclides not currently in the analytical program that may be needed to assure absence of elevated radiation doses and could be useful for identifying trace contaminants.

Alpha Particles↗
PubMed1990

Analysis of 228Ra and 226Ra in public water supplies by a gamma-ray spectrometer.

Methods for measuring 228Ra were reviewed to select a brief and simple screening procedure under NIPDW Regulations for public water supplies. A two-step method was considered to concentrate Ra by evaporation or co-precipitation and to count it with a gas ionization detector, a liquid-scintillation detector, or a Ge detector with multichannel analyzer. Gross beta particle counting appears to be feasible for screening to meet the 0.04 Bq L-1 detection limit. One can utilize the same sample volume as currently collected and measure radiation with commonly available equipment in reasonable time. The required sample volumes were estimated on the basis of known counting efficiencies and background count rates. Gamma-ray spectral analysis is the recommended option, however, because 226Ra and 228Ra can be determined directly and simultaneously. Several aspects of the method were examined to assure that the concentration procedure is nearly quantitative and that the detection limit can be reached with a 3.8-L sample in a 6000-s counting period. The method was tested with Ra tracer solutions and EPA intercomparison samples over the range of 0.04 to 1 Bq L-1. It was found appropriate for 228Ra and 226Ra analyses.

Radium↗
PubMed1993

A Monte Carlo approach to assessing 147Pm in the liver of the adult phantom.

A low-background phoswich detector is used to detect small amounts of 147Pm--a pure beta-emitting nuclide--present in the liver of an occupational worker. The assessment was based on the measurement of bremsstrahlung radiation produced by the beta particles in the tissue. Computer programs based on Monte Carlo techniques for photon transport have been developed to calculate the response of an external phoswich detector to 1) a 147Pm point source embedded in tissue-equivalent slabs of various thicknesses; and 2) various source distributions of 147Pm in the liver of an adult phantom. The goal is to theoretically calibrate the phoswich detector for each source distribution and to study the variation of maxima of the spectra with the depth of the source in the adult phantom liver and tissue-equivalent slabs. The initial bremsstrahlung photon distribution of 147Pm in water has been computed using Wyard's and Pratt's methods. These calculations have been compared with experimental measurements using Perspex acrylic sheet slabs. Good agreements have been noted when the initial bremsstrahlung spectrum is obtained by using Wyard's method. These results find applications in monitoring the liver burdens in occupational workers handling 147Pm-based radioluminous paints.

Adult↗
PubMed1997

Energy deposition pattern from tritium and different energy photons--a comparative study.

Energy deposition patterns of beta particles from tritium decay have been analyzed in comparison with photon radiation in the energy range from 12 to 1250 keV. Energy deposition was modeled by Monte Carlo means using electron tracks in water vapor with a complete follow up of delta electrons. Ionizations have been used as representative of track structure. Frequencies of clusters on a nanometer scale and their spatial distribution in spherical targets representing cell nuclei have been derived. Cluster analysis has been carried out by implementing a k-means method. Frequencies of ionization clusters from tritium are similar to 60-100 keV photons. Spatial distribution of clusters from tritium closely match approximately 70 keV photons up to 2 microm separation.

Monte Carlo Method↗
PubMed1998

A method and apparatus for monitoring the level of tritiated water vapor in air using a solid scintillator.

Tritium is presently used in large quantities in laboratories for technological studies, as fuel for the process of nuclear fusion, and in the manufacture of radio-luminescent items. It is also produced in fission nuclear plants (with a yield of 10(-4) if the fuel is 235U and twice as much if the fuel is 239Pu), particularly in those which use D2O as moderator. The weak energy of beta particles (Emean=5.7 keV) produced by tritium implies that it is only harmful if internalized. In nature tritium in air is mainly present under two different chemical forms: elementary (HT, DT, T2) and oxidized (HTO, DTO, T2O). The latter is extremely more dangerous than the former as far as radioprotection is concerned; for this reason the derived air concentration limit (8 x 10(5) Bq m(-3)) for the gaseous form is 25,000 times higher than the value for the oxidized one. The purpose of the work presented here is to realize an area monitor that is able to discriminate in real time between the two chemical forms. Using the properties of zeolite as an absorber and scintillator, it was possible to construct such a detector. In 1 h the instrument can reveal HTO concentrations 40 times below the derived air concentration. A concentration equal to the derived air concentration can be revealed within the first minute of counting and the performance may be further improved. Moreover, the prototype realized is able to work automatically and continuously for 5 h. The capability of discriminating the oxidized chemical form, the sensitivity, and the possibility of obtaining real time information make this instrument a good monitor in those cases where there is a real risk of tritium air contamination.

Air Pollutants, Radioactive↗
PubMed1998

Issues in the reconstruction of environmental doses on the basis of thermoluminescence measurements in the Techa riverside.

The potential of thermoluminescence measurements of bricks from the contaminated area of the Techa river valley, Southern Urals, Russia, for reconstructing external exposures of affected population groups has been studied. Thermoluminescence dating of background samples was used to evaluate the age of old buildings available on the river banks. The anthropogenic gamma dose accrued in exposed samples is determined by subtracting the natural radiation background dose for the corresponding age from the accumulated dose measured by thermoluminescence. For a site in the upper Techa river region, where the levels of external exposures were extremely high, the depth-dose distribution in bricks and the dependence of accidental dose on the height of the sampling position were determined. For the same site, Monte Carlo simulations of radiation transport were performed for different source configurations corresponding to the situation before and after the construction of a reservoir on the river and evacuation of the population in 1956. A comparison of the results provides an understanding of the features of the measured depth-dose distributions and height dependencies in terms of the source configurations and shows that bricks from the higher sampling positions are likely to have accrued a larger fraction of anthropogenic dose from the time before the construction of the reservoir. The applicability of the thermoluminescent dosimetry method to environmental dose reconstruction in the middle Techa region, where the external exposure was relatively low, was also investigated.

Alpha Particles↗
PubMed1998

NMR microscopy of trabecular bone and its role in skeletal dosimetry.

One of the more intractable problems in internal dosimetry is the assessment of energy deposition by alpha and beta particles within trabecular, or cancellous, bone. In the past few years, new technologies have emerged that allow for the direct and nondestructive 3D imaging of trabecular bone with sufficient spatial resolution to characterize trabecular bone structure in a manner needed for radiation dosimetry models. High-field proton nuclear magnetic resonance (NMR) imaging is one such technology. NMR is an ideal modality for imaging trabecular bone due to the sharp contrast in proton density between the bone matrix and bone marrow regions. In this study, images of the trabecular regions within the bodies of a human thoracic vertebra have been obtained at a field strength of 14.1 T. These images were digitally processed to measure chord length distribution data through both the bone trabeculae and marrow cavities. These distributions, which were found to be qualitatively consistent with those measured by F. W. Spiers and colleagues at the University of Leeds using physical sectioning and automated light microscopy, yielded a mean trabecular thickness of 201 microm and a mean marrow cavity thickness of 998 microm. The NMR techniques developed here for vertebral imaging may be extended to other skeletal sites, allowing for improved site-specific skeletal dosimetry.

Bone Marrow↗
PubMed1999

Detection of radon decay products in rainwater.

The Argonne National Laboratory-East (ANL-E) Environmental Radiation Monitoring System measures and records ambient radiation levels and provides detection capability for radon decay products in rain clouds. These decay products in rainwater tracked into a facility on the shoes of workers can cause false alarms from hand and shoe monitors. The monitors at ANL-E can easily detect the radon decay products, and the 19.6 and 26.8 min half-lives of the beta-particle emitters are long enough in many cases for sufficient activity to still be present to initiate a contamination alarm when the shoes are checked for radioactivity. The Environmental Radiation Monitoring System provides a warning when precipitation contains elevated levels of radon decay products. It is based on a prototype developed at the Super Collider Laboratory. During its first year of operation there were nine alarms from radon decay products with an alarm trigger point set at 30% greater than background. The alarms occurred at both monitoring stations, which are approximately 1,000 m apart, indicating large diameter radon clouds. The increases in background were associated with low atmospheric pressure. There was no correlation with radon released from the coal-burning steam plant on the site. Alarms also occurred when short-lived accelerator-produced radioactivity in the exhaust stack plume passed over the NaI(Tl) detector in one of the stations. The 450 MeV proton accelerator near the station produced 12C, 13N, and 15O by spallation of air nuclei. The gamma-ray spectrum from the plume from the accelerator exhaust stack was dominated by the 511 keV annihilation gamma rays from decay of these radionuclides. These gamma rays were easily distinguished from the 609 keV, 1,120 keV, and 1,764 keV gamma rays emitted by the radon decay products.

Atmospheric Pressure↗