Β-emitting Radionuclides Research Articles

Cocktail mismatch effects in 4πβ liquid scintillation spectrometry: Implications based on the systematics of 3H detection efficiency and quench indicating parameter variations with total cocktail mass (volume) and H 2O fraction

Detection efficiency changes for 3H by 4πβ liquid scintillation (LS) spectrometry cannot be adequately monitored by quench indicating parameters when the quench changes are the result of multiple causal factors (e.g. simultaneously varying cocktail sizes and composition). In consequence, some kinds of cocktail mismatches (between LS counting sources) introduce errors that result from efficiency changes that cannot be fully accounted for by quench monitoring compensations. These cocktail mismatch effects are examined for comparative 3H measurements and for 3H-standard efficiency tracing methods for the assay of other β-emitting radionuclides. Inherent errors can occur in both types of radionuclidic assays, as demonstrated with realistic case examples, unless cocktails are very closely matched. The magnitude of the cocktail mismatch effect (and attendant errors) can range from being virtually negligible (particularly for high-energy β-emitting nuclides and for slight single-variable cocktail composition mismatches) to be being very significant for high-precision metrology and standardizations (particularly with easily quenched, low-energy β emitters and for mismatches due to both varying cocktail constituents and concentrations). The findins presented here support the need to understand fully the quenching systematics of a given LS system (combination of cocktails and spectrometer) and the need for very careful control of cocktail preparations.

Radioluminescent Light Source for Optical Oxygen Sensors

A self-powered radioluminescent (RL) light source is evaluated as a means of supplying incident radiation for optical chemical sensors. The light source consists of 147Pm (a β-emitting radionuclide) and ZnS:Ag phosphor. Blue light (450 nm) is produced following the excitation of ZnS:Ag from β particles released by the 147Pm. The utility of this source is judged by evaluating the analytical performance of optical oxygen sensors, where the blue light from the RL source excites a ruthenium complex immobilized in a plasticized PVC or silicon membrane. Analytical information is acquired by measuring the magnitude of oxygen-induced fluorescence quenching of the ruthenium complex. The resulting RL oxygen sensors show good stability and reversibility, with detection limits of 0.25 Torr in gaseous samples and 0.028 ppm in aqueous samples. Although the RL light source is not as bright as conventional electrical-powered sources, RL sources offer the advantages of compact size, simple configuration, low power consump...

Cocktail volume effects in 4πβ Liquid scintillation spectrometry with 3H-standard efficiency tracing for low-energy β-emitting radionuclides

The effect of total liquid scintillation (LS) cocktail volume (or mass) in the 4πβ LS spectrometry of β-emitting radionuclides has been investigated. The magnitude of such possible volume effects on the apparent activity of low-energy β-emitting radionuclides, as determined by the CIEMAT/NIST 3H-standard efficiency tracing method, as well as any systematic trends in the relative detection efficiencies of low-ebergy β-emitters were studied. The radionuclides chosen for the study, 63Ni and 36Cl, were traced against 3H. Detection efficiency losses, as a function of total LS cocktail volume, were found to be energy-dependent. Because of the low E βmax for the decay of 3H and 63Ni, systematic losses in efficiency with increasing cocktail mass, as well as at extremely low (< 5 g) masses were observed. The determination of quench-indicating parameters, even for cocktails of uniform composition, were also found to be volume-dependent. Despite a relatively large (17%) variation in the 3H counting efficiency over the volume range 1–20 mL in 22 mL vials and a corresponding 7% varition in the 63Ni counting efficiency, the CIEMAT/NIST method was able to trace the observed 63Ni activity to about 0.1%. No volume effect on the observed relative efficiency of 36Cl was found. The best condition for repeatability in the determination of the massic activity of a single sample was found to be when the volume is 8–12 mL in a 22 mL vial. The effect of total LS cocktail volume on the efficiency-traced massic activities was found to have no clear, consistent trend and proved difficult to quantify. Nonetheless, two approaches to estimating the magnitude of the effect are presented and indicate that it is extremely small (< 0.1%) and was within the statistical variation of the measurements.

Imaging and therapy with monoclonal antibodies in non-hematopoietic tumors

Although radiolabelled monoclonal antibodies are useful in tumor imaging, in our opinion their most important role is in the evaluation of the capacity of newly developed monoclonal antibodies to localize in tumors specifically. Intravenous injections of monoclonal antibody fragments, labelled with β-emitting radionuclides, can completely eradicate large human colon carcinoma xenografts in nude mice whereas this is not achieved by unconjugated monoclonal antibodies. New strategies are being developed to make radioimmunotherapy applicable to carcinoma patients.

A method for quantifying radioactivity associated with protein in silver-stained polyacrylamide gels

A method is described in which individual proteins labeled with weak β-emitting radionuclides, separated by polyacrylamide gel electrophoresis, and stained with silver are released from the gel by the use of the periodate soluble cross-linking agent N,N′-dialyltartardiamide. The radioactivity can then be quantitated using liquid scintillation counting. The method is shown to be insensitive to reasonable variations in the intensity of staining as well as the gel volume over a practical range of gel slices. Recovery from the gel is extremely good with 93% of the counts associated with 14C-labeled proteins of known radioactive concentration being recovered. Analysis of a complex mixture of 3H-labeled proteins indicates resolution similar to that obtainable by autoradiography without the problems associated with quenching of autoradiographic signal by the staining procedure. The method is used to determine the amount of fucose and mannose incorporated into a putative cell adhesion protein during development of the cellular slime mold Dictyostelium purpureum.

The multistep avalanche chamber as a detector in radiochromatography imaging

We have investigated the possibility of using the multistep avalanche chamber as an imaging detector in radiochromatography. High position resolution, better than 0.5 mm fwhm, combined with a high sensitivity give very satisfactory results. Measurement on two-dimensional distributions of β-emitting radionuclides such as 3H, 14C and 35S are presented and compared with results obtained from autoradiography.

An Autoradiographic Technic for Plutonium, Polonium, and Promethium Tissue Sections

Syrian hamster lung sections containing 238Pu, 239Pu, 210Pu, or 147Pm are deparaffLized and hydratedto water. The slides are dipped in NTB emulsion, allowed to dry overnight, and exposed in Bakelite boxes at room temperature. They are then developed in D-19 for two to four minutes, rinsed in distilled water for ten seconds, fixed in Kodak fixer for five minutes, and washed at least 30 minutes in distilled water before staining with nuclear fast red and indigo-carmine. This autoradiographic technic, in conjunction with this particular staining procedure, gives a quick, efficient method for working with different α- and β-emitting radionuclides.

An Autoradiographic Technic for Plutonium, Polonium, and Promethium Tissue Sections

Syrian hamster lung sections containing 238Pu, 239Pu, 210Pu, or 147Pm are deparaffLized and hydratedto water. The slides are dipped in NTB emulsion, allowed to dry overnight, and exposed in Bakelite boxes at room temperature. They are then developed in D-19 for two to four minutes, rinsed in distilled water for ten seconds, fixed in Kodak fixer for five minutes, and washed at least 30 minutes in distilled water before staining with nuclear fast red and indigo-carmine. This autoradiographic technic, in conjunction with this particular staining procedure, gives a quick, efficient method for working with different α- and β-emitting radionuclides.

Detection of hard β-emitting radionuclides in aqueous solutions using Cerenkov radiation: A review article

Cerenkov counting of solutions is advocated as a useful means of detecting hard β-emitters; the present work is dedicated to the practical aspects of Cerenkov detection with commercially available liquid scintillation spectrometers. The variations of count rates with the type of vials and the volume of solutions are pointed out. With a spectrometer equipped with S 11 phototubes, detection efficiencies from 16 calibrated sources are found to be 23–50 per cent for emitters of E β maximum in the range 1·3−2·3 MeV and 50–70 per cent up to 3·5 MeV. The results of experiments with various optical filters suggest a direct relationship between the β energy of the isotope and the fraction of Cerenkov light emitted in the ultra-violet region. Pulse height analysis either by calculation of the channel ratio obtained from the spectrometer or by direct oscilloscopic display of spectra enables the energy of any unknown β-emitter to be evaluated. Color quenching of biological solutions inhibits more widespread use of Cerenkov counting while solute quenching is shown not to be a problem. Changes induced by 31 wavelength shifters are assessed; we single out Esculin as one of the most effective. Stress is being put on the advantages of Cerenkov counting of 42K, 32P, 86Rb and 24Na and the applicability of the method to more than 40 β-emitters having maximum beta energies above 1 MeV.

A practical method for resolution of two β-emitting radionuclides by liquid scintillation counting

A practical method for resolution of mixtures of two β-emitting radionuclides is described utilizing liquid scintillation counting procedures which combine simplicity of quench correction with the reliability of the “Discriminator ratio” method of double-label counting. A channel is set for each radionuclide, allowing 10 per cent overlap of the lower energy member into the channel set for the higher energy member, and quench correction standards and experimental samples are counted with and without an external standard. Simultaneous equation solutions are used which make optimal use of channels ratio data available by direct print-out. If R A and R B equal net cpm in channels A and B, R a and R b equal net cpm for radionuclides a and b, and F a ∼ and the channels ratio A B for radionuclides a and b, and R a = ( F b R B − R A / ( F a F b − 1) and R b = ( F a R A − R B )/ F a F b − 1). Values for F and counting efficiency (to convert cpm to dpm), as functions of the channels ratio A B for the external standard, amy graph made using counting data for the graphically derived from the quench correction standtards. quench correction standards. Absence of restrictions and ease of adaptation make the method applicable to any pair of β-emitting radionuclides sufficientlly different diffrecent in Energy to be accurately resolved; this can be determined from a plot of per cent error in resolution of each radionuclide as a function of the ratio of the amounts of each member present in the mixture.

Anwendung der β-strahlungsanregung der röntgenstrahlung zur untersuchung der diffusion in festkörpern

There has been proposed the method of diffusion investigation by layer analysis based on the measurement of X-rays formed in β-X conversion process. This method has two versions i.e. the measurement of K X-rays characteristic for a given element and the measurement of high-energy part of bremsstrahlung radiation spectrum. The second version has been tested on the base of bismuth diffusion in copper. This method can be applied to all β-emitting radionuclides which diffuse in medium of sufficiently high atomic number.

Zur Absolutmessung der Radioaktivität reinerβ-Strahler mit flüssigen Szintillatoren

The use of liquid scintillation counting for the absolute standardization of pure β-emitting radionuclides by means of the efficiency-tracing method is investigated. Special effects occuring by the use of liquid scintillators do not lead to important errors. Results of measurements of the nuclides35S and45Ca are given.

Radioassay for β-emitters in biological materials using cerenkov radiation

An investigation was conducted on the detection of β-emitting radionuclides in plant roots by means of Cerenkov radiation. The samples were directly radioassayed in polyethylene vials with an aqueous solution of the wavelenght shifter 7-amino-1,3-naphthalene-disulfonic acid. High efficiencies are obtained for hard β-emitters, e.g. about 60% for 86Rbuin 1 g tissue. The relatively weak β-emitter 36Cl can still be determined with an efficiency of 13 per cent in plant roots. The maximum β-energy of a nuclide must be at least 0.5 MeV for radioassay by Cerenkov radiation in biological material. Self-absorption of weak β-emitters in tissues has to be considered. The procedure described here should be applicable to other plant tissues and to animal materials. The method was tested in experiments on the kinetics of ion absorption by plant roots and earlier work in which radioactivity was determined with a gas-flow counter was confirmed.

The use of Cerenkov radiation in the measurement of β-emitting radionuclides

Cerenkov radiation produced in an aqueous by ß-emitting radionuclides of energy greater than 260 KeV has been investigated as a means of radioassay. Compared with liquid scintillation techniques sample preparation is simple volumes up 20 ml may be counted and the efficiency is unaffected by chemical quenching. Due to the low photon yield the method is only practicable for radionuclides emitting ß-particles of energy >1 MeV. The detection efficiency has been studied as a function of ß energy; representative values are 25 per cent for 32P and 62 per cent for 106Ru 106Rh using a commercial liquid scintillation counter fitted with two photomultiplier tubes in a fast coincident circuit. Colour and ultraviolet quenching can be serious and methods of correcting for them have been studie; external standardization, decoloration and the use of ultra-violet filters are shown to be convenient techniques. The counting efficiency is improved by using quarts apparatus, incorporating wavelength shifters and (because of the directional nature of Cerenkov radiation) by using a non-coincidence circuit.

RADIOGRAPHIC CHANGES FOLLOWING THE ADMINISTRATION OF BONE-SEEKING RADIONUCLIDES.

During investigations on the carcinogenic effects of α and β-emitting radionuclides, serial radiographs of rats injected with single and repeated doses of 32P, 239Pu, or 241Am were studied to record the development of radiation-induced changes. Among the lesions observed were failure of longitudinal bone growth, abnormal bone moulding, pathological fractures, and the production of sclerosing, lytic, and mixed forms of osteosarcoma. The induction of bone tumours could be identified early and the development followed closely; radiographic changes were described.