Gamma Counting Techniques Research Articles

Real time reconstruction of the fast electron spectrum from high intensity laser plasma interaction using gamma counting technique

X-ray and gamma fluxes from the high intensity laser-plasma interaction are extremely short, well beyond temporal resolution of any detectors. If laser pulses come repetitively, the single photon counting technique allows to accumulate the photon spectra, however, its relation to the spectrum of the initial fast electron population in plasma is not straightforward. We present efficient and fast approach based on the Geant4 package that significantly reduces computer time needed to re-construct the high energy tail of electron spectrum from experimental data accounting for the pileup effect. Here, we first tabulate gamma spectrum from monoenergetic electron bunches of different energy for a given experimental setup, and then compose the simulated spectrum. To account for the pileups, we derive analytical formula to reverse the data. We also consider errors coming from the approximation of the initial electron spectrum by the sum of monoenergetic impacts, the finite range of the electron spectrum, etc. and give estimates on how to choose modelling parameters to minimize the approximation errors. Finally, we present an example of the experimental data treatment for the case of laser-solid interaction using 50 fs laser pulse with intensity above 1018 W/cm2.

Neutron transfer in $$^{9}$$Be + $$^{159}$$Tb system

One neutron stripping cross sections ($\sigma_{-1n}$) are measured in $^{9}$Be+$^{159}$Tb system in the energy range E$_{cm}$/V$_{B}$ $\sim$ 0.79 - 1.24 using offline gamma counting technique. The CRC model calculations including the ground state and the 2$^{+}$ resonance state of $^{8}$Be, carried out using the FRESCO code, give a reasonable description of the measured data. In addition, comparisons of reduced 1n-stripping cross sections- $\sigma_{red}$ with $^{9}$Be for different target nuclei (A $\sim$150-200), and $\sigma_{red}$ for $^{9}$Be, $^{6}$Li with $^{159}$Tb target are presented. While no strong target dependence is observed with $^{9}$Be projectile, $\sigma_{red}$($^{9}$Be) is significantly larger than that for $^{6}$Li, which is consistent with the Q-value for transfer reactions and breakup threshold energy of projectiles.

Analysis of radioactivity concentration in natural rubber latex and radiation prevulcanized natural rubber latex (RVNRL)

Radiation vulcanization of natural rubber latex (RVNRL) is an alternative technology to conventional sulphur vulcanization. To eliminate some public members sceptical view toward the radioactivity of the prevulcanized latex produced using gamma radiation, RVNRL was prepared at several radiation doses and then their radioactivity concentration were measured using gamma counting technique. The activity concentration level of Ra-226, Th-232, and K-40 in RVNRL found to be not significantly different from non-vulcanized natural rubber latex (NRL). The reported radioactivity proved that using gamma radiation in the RVNRL preparation could not ionized and produce radioactive materials from NRL minerals. Hence, it is concluded that RVNRL is safe to be used as the main raw material in latex dipped products industry.

Concentration of Uranium and Thorium in Granite Rock in Kadugli, Sudan Using γ - ray Spectroscopy

The aim of the present study is to determine the elemental concentration in (ppm) and specific activity in (Bqkg-1) of Uranium (238U) and Thorium (232Th) contained in the granite rock of a special geological area in Sudan (Kadugli).
 The elemental concentrations and specific activity of 238U and 232Th in granite rock were determined by using the gross gamma counting technique (γ-ray spectroscopy). The analyses were performed for daughter decaying of 238U and 232Th; which are Pb-214, Bi-214 for 238U and Tl-208, Ac-228 for 232Th.
 The experiments were carried out at the Nuclear Laboratory, Physics Department, Universiti Teknologi Malaysia using the facilities of gamma ray spectroscopy system with high purity germanium detector (HPGe) of efficiency 20%.
 Granite samples were collected from Hagar El-Mlik area, 2 km from the central of Kadugli city in southern Kordofan state, Sudan. The rock was crushed and ground to fine powder and sieved with a particle size less than 120 μm. To calculate the concentrations of 238U and 232Th in the granite rock, standard reference materials provided by International Atomic Energy Agency (IAEA) was used.
 The average of elemental concentrations and specific activity of uranium were obtained in the range (1.8 ± 0.11) to (0.80 ± 0.08) ppm, and (22.11 ± 1.30) to (9.79 ± 0.98) Bqkg-1 respectively, while (16.22±1.84) to (7.45±1.34) ppm and (65.42±7.40) to (29.50 ± 5.39) Bqkg-1 are the average concentration and specific activity of thorium. Moreover, average activity concentrations (Bqkg-1) for granite samples have been compared with the typical values of different countries.
 232Th shows high activity concentration (65.42±7.4) Bqkg-1 whereas, 238U activity value is distinctly lower than the corresponding ones obtained from other countries and, in general, all results are acceptable and fall within the range given in UNSCEAR report 1993.

INVESTIGATION OF CHITOSAN FOR DECORPORATION OF 60Co IN THE RAT

With the increased threat of terrorist release of radioactive materials, there is a need for non-toxic decorporation agents to treat internal contamination with radionuclides. In this study, low molecular weight chitosan was evaluated for decorporation of radioactive cobalt (60Co). The affinity of chitosan for Co(II) was tested in vitro using spectrophotometric and potentiometric titration techniques. For in vivo studies, the effect of chitosan on ingested 60Co was evaluated using F344 rats administered a single dose followed by oral chitosan. Chitosan was also evaluated for systemic decorporation of 60Co following intravenous injection with repeated chitosan administration over 5 d. Control animals received 60Co without chelation treatment. Excreta and tissues were collected for analysis using gamma-counting techniques. Results from in vitro experiments confirmed the binding of Co(II) to chitosan, with the postulated formation of a mixed cobalt-chitosan-hydroxide complex species; a stability constant was calculated for this complex. For in vivo studies, oral administration of chitosan significantly reduced systemic absorption of orally administered 60Co as evidenced by an increase in fecal elimination and decrease in urinary elimination. However, oral administration of chitosan lactate slightly decreased fecal excretion of 60Co. Further, oral administration of chitosan significantly reduced 60Co levels in kidney, liver, and skeleton compared to control animals receiving 60Co alone. By the i.v. route, chitosan slightly reduced levels of 60Co in tissues compared to controls, although statistically significant reductions were only observed for blood and kidney. Overall, this commercially available chitosan oligosaccharide exhibited promising potential; further studies are warranted to evaluate the optimal dosing regimen and chemical modifications to increase effectiveness.

Synthesis and preliminary biological evaluation of a 99mTc‐labeled hypericin derivative as a necrosis avid imaging agent

AbstractMono‐[123I]iodohypericin and mono‐[123I]iodohypericin monocarboxylic acid are iodine‐123‐labeled hypericin derivatives which have shown great promise in preclinical studies as necrosis avid imaging agents in animal models of infarction. In view of the more attractive properties of a 99mTc‐labeled hypericin derivative, we have synthesized a conjugate of protohypericin monocarboxylic acid with S‐benzoylmercaptoacetyldiglycyl‐diaminopentane in an overall yield of 15%. The conjugate was labeled with technetium‐99m by exchange labeling at pH 10 in a labeling yield of 95% followed by photocyclization to yield 99mTc‐mercaptoacetyldiglycyl‐1,5‐diaminopentylene hypericincarboxamide (99mTc‐13). The negatively charged 99mTc‐13 complex was purified by reversed phase high‐pressure liquid chromatography and the log P7.4 was determined to be 2.36. In normal NMRI mice, the complex showed slow hepatobiliary clearance while plasma clearance was rapid. The tracer was evaluated in rats with reperfused hepatic infarction by ex vivo autoradiography, gamma counting and histochemical techniques. Unlike the radioiodinated hypericin derivatives, the new tracer agent did not show preferential uptake in necrotic tissue on autoradiography and gamma counting techniques. Conjugation of hypericin with a 99mTc‐chelate, resulting in a change in size, charge and lipophilicity, had a profound effect on the necrosis avidity of the tracer agent. The results show that 99mTc‐13 is not suitable for imaging necrosis. Copyright © 2008 John Wiley & Sons, Ltd.

Reconstructing historical seismicity from lake sediments (Lake Laffrey, Western Alps, France)

AbstractSediment archives from a mountain lake are used as indicators of seismotectonic activity in the Grenoble area (French western Alps, 45°N). Sedimentological analysis (texture and grain‐size characteristics) exhibits several layers resulting from instantaneous deposits in Lake Laffrey: six debris flow events up to 8 cm thick can be attributed to slope failure along the western flank of the basin. Dating with 210Pb and 137Cs gamma counting techniques and the reconnaissance of historical events, provide a constrained age‐depth model. Over the last 250 years, five of such debris flow deposits could be related to historical earthquakes of MSK intensities greater than VI over an area of <60 km. One debris flow deposit triggered at the beginning of the last century can be related to an historical landslide possibly triggered by the artificial regulation of the lake level.

Early aspects of the intrarenal distribution of mercury after the intravenous administration of mercuric chloride

The present study was designed to evaluate the early aspects of the renal accumulation and intrarenal distribution of inorganic mercury in rats given a nontoxic 0.5 μmol/kg or a moderately nephrotoxic 2.0 μmol/kg intravenous dose of mercuric chloride. Each dose of mercuric chloride contained between 1.0–1.5 μCi 203Hg 2+ in order to make it possible to follow the pattern for the intrarenal accumulation of inorganic mercury with standard gamma-counting techniques. Within the first 5 min after injection of either dose of mercuric chloride, about 70% of the dose of mercury was abstracted from blood. About 10% of the dose was in the combined renal mass, with the greatest fraction in the cortex. The liver contained about 5% of the dose. By the end of the first 3 h after injection of either dose, greater than 90% of the dose of mercury had been abstracted from the blood. At this time, about 8% of the dose was in the liver and more than 50% of the dose was found in the total renal mass. Again, the concentration of mercury in the renal cortex was greater than that in any other zone. The concentration of mercury in the outer stripe of the outer medulla also increased markedly over the first 3 h after injection, but was half that in the cortex. No change in the concentration of mercury was detected in the inner stripe of the outer medulla and inner medulla over the 3-h time period. Findings from the present study indicate that the pattern for intrarenal distribution of mercury does not change significantly during the initial 3 h after injection of the moderately nephrotoxic dose of mercuric chloride. Normally, the concentration of mercury in the outer stripe of the outer medulla increases above that in the cortex sometime during the first 24 h after a low or moderately nephrotoxic dose of inorganic mercury. The present findings indicate that this shift occurs sometime after the first 3 h.

Effects of metastatic and non-metastatic mammary adenocarcinoma on tissue distribution of gallium-67 in the rat

The purpose of this work was to study the effect of metastatic and non-metastatic mammary adenocarcinoma on tissue distribution of gallium-67 (67 Ga) citrate in Fischer-344 female rats by the use of gamma counting techniques. The homogenate (0.1 mm) of a sample of metastatic and non-metastatic tumor was implanted by subcutaneous injection in the right footpad of each animal's hind extremity. The animals bearing metastatic tumor were studied 2-24 days and the non-metastatic group 2-30 days after the implantation of tumor homogenate. The control group consisted of four animals and tumor-bearing groups of seven to eight animals at each time point. All animals were injected with 1.11 MBq of 67Ga citrate by intravenous administration and sacrificed in halothane anesthesia 48 h later. The relative tissue uptake data are presented as arithmetical mean value with a standard error and graphically demonstrated as normalized data with respect to control. The results demonstrate that 67Ga citrate uptake was largely unaffected in most organs by the presence of either metastatic or non-metastatic tumor. Gallium-67 uptake, however, was significantly and consistently increased in the popliteal lymph nodes of the ipsilateral extremity of tumor implant in the metastatic group. No difference was observed in the non-metastatic tumor group. The findings of this experimental work indicate that the host reaction to the tumor does not modify the gallium uptake characteristics in the normal tissues of tumor-bearing animals.

Determination of thorium isotopes in seawater by nondestructive and radiochemical procedures

Procedures have been developed for the analyses of dissolved and particulate 234Th, 228Th, 230Th and 232Th in seawater. Large volume samples (>1000 1) are collected using in situ pumps. Seawater is pumped sequentially through a filter cartridge and two MnO 2 adsorbers for the collection of particulate and dissolved Th, respectively. Both filters adsorbers are analysed for 234Th using a simple gamma counting technique. This newly developed 234Th procedure can be conducted at sea, and thus provides an easy and efficient method for 234Th analyses on large volume samples. Subsequent radiochemical purification procedures and low-level alpha counting techniques are used in the laboratory for the analyses of 228Th, 230Th and 232Th on these same samples.

Radioimmunoassay in microtiter plates: A convenient method for determining bound radiolabelled ligand

A radioimmunoassay was performed in the wells of casein-coated microplates employing 125I-labelled sheep anti-human second antibody. The antigen-antibody complexes were thereafter dislodged from the well walls using the detergent sodium dodecyl sulfate (SDS) and the entire contents of the wells were simultaneously absorbed into 48 cellulose acetate-absorbing cartridges. All 48 cartridges were transferred to counting vials and the radioactivity determined by standard gamma counting techniques. The particular advantage of the method described here is the ease with which the supernatants can be collected and transferred to counting vials with minimal handling of radioactive samples.

Radium isotopes in coastal and open ocean surface waters of the Western North Pacific

Using manganese-impregnated fiber extraction and high-efficiency gamma counting techniques, we measured the distribution of 228Ra and 226Ra in surface waters near the coast of Japan and in the western North Pacific. There is no evidence in our data that any significant amount of 228Ra is added to open ocean surface waters from the coastal waters around Tokyo Bay. High 228Ra concentrations (> 10 dpm/10 3 kg), were observed along the Kuroshio Current as compared to < 2.5 dpm/10 3 kg between 10° and 30°N of the central gyre, and hence the major source of 228Ra in the surface water is likely to be the East Asian continental shelf zones. A simple one-dimensional eddy diffusion and advection model is used to explain the observed decrease of 228Ra from coast to the open ocean. The model results indicate two mixing regimes across the Kuroshio Current System with apparent eddy diffusion coefficients of K y = 4 × 10 5 cm 2 s −1 at distance y < 200 km from the coast, and K y = 4 × 10 7 cm 2 s −1 at y > 200 km. Along ∼40°N where an eastward flow of the ‘Kuroshio Extension’ prevails, an advective flow of > 0.1 knot is consistent with the observation of nearly constant 228Ra along the track. The geographical distribution pattern of 228Ra is clearly different from that of atmospherically derived 210Pb. Thus the 228Ra in surface water serves as a useful tracer that accompanies fluvially and coastally derived elements during their subsequent lateral transport toward the central gyre.

Neutron leakage measurements from a medical linear accelerator.

The McCall method has been used to measure neutron leakage from the Mevatron 77, 18- and 15-MV photon beams. Gold foil activation has been used employing a beta counting technique for the 18-MV beam and a gamma counting technique for both the 18- and 15-MV beam. The two counting techniques were used to evaluate their relative merit. The measurements were made at various locations in the patient-treatment plane for different field sizes. The results show that the thermal-neutron dose equivalent contributes only about 1%-2% of the total neutron dose equivalent. At 100 cm, the neutron dose equivalent for the 18-MV beam is approximately six times that of the 15-MV beam, slightly exceeding the 0.1% of the useful beam criteria used by some of the regulatory agencies. In light of the uncertainty in fluence to dose equivalent conversion factors, the increased dose equivalent above 0.1% is insignificant.

Quantitative measurement of intrapulmonary and extrapulmonary right-to-left shunt.

We have developed a new technique that enables the shunting of blood from the right to the left side of the circulation to be partitioned into a cardiac and a lung component. The effects of recirculation are minimal, and the method does not require on-line data analysis. Quantitative estimates of these components have been made in two normal dogs and in five patients with raised pulmonary arterial pressures, some of whom were known to have a patent foramen ovale. The results were compared with oxygen shunt measured during air breathing. A poorly soluble gas, nitrogen, radiolabelled with 13N in solution is injected first into a central vein while matched samples of blood are drawn from the pulmonary artery and the aorta. A second solution containing 13N is injected into the right ventricle and sampled from the aorta only. Standardized gamma-counting techniques were used to analyze both the injected radioactivity and the radioactivity in the samples. These two measurements enable us to calculate the total right-to-left shunt, the pulmonary shunt, and by subtraction the extrapulmonary cardiac shunt.

Cosmogenic nuclides in recently fallen meteorites: Evidence for galactic cosmic ray variations during the period 1967–1978

Cosmogenic radionuclides were measured on 48 fragments of 24 meteorites which fell between 1967 and 1978. Nondestructive gamma counting techniques were used to obtain data on 7Be, 46Sc, 48V, 51Cr, 54Mn, 56Co, 57Co, 58Co and 60Co on at least some of the samples. Sodium 22 and 26Al measurements are reported on all 48 samples. In addition, new rare gas data and exposure ages are reported for the meteorites Guibga, Gorlovka, Dhajala, Louisville, Acapulco, Jilin, Kabo, Alta‐Ameen, and Canon City. The cosmogenic radioisotope and rare gas data are interpreted in terms of a time dependent modulation of galactic cosmic rays spanning one full 11 year sun spot cycle. Special attention is given to the data on 22Na, 46Sc, 54Mn, and 48V with either 26Al or 22Ne/21Ne used to provide a shielding correction. The shielding normalized data using the 26Al method appear to correlate well with calculated production rates scaled against the Deep River neutron monitor. The data for the four isotopes are consistent with a production rate variation of a factor of 2.5–3 between solar maximum and solar minimum for sun spot cycle 20. These data demonstrate that the production rates of cosmic ray‐produced nuclides in meteorites vary considerably according to modulation by the 11‐year solar cycle and support the concept that variations of solar‐modulated, cosmic ray flux of similar magnitude have occurred over much longer time periods.

Vertical distribution of 137Cs and its accumulation rate in lake sediments.

Vertical distributions of 137Cs in the sediments of Lake Biwa, Lake Suigetsu and Lake Mikata were measured by the non-destructive gamma counting technique using a germanium-lithium detector. Possible sedimentation rates were estimated based upon the depth of 137Cs penetrating into the sediments.

Effect of arterial stretch on transmural albumin and Evan's blue dye transport.

The influence of arterial wall circumferential stretch (lambda) on the 32-min diffusive mural uptake of 125I-albumin and of Evan's blue dye (EBD) across the injured endothelial surface was studied in the intimal-medial preparation of the canine descending thoracic aorta (DTA). Albumin uptake (MA nmol/cm2) was measured by standard gamma counting techniques and the corresponding EBD uptake (ME) by the reflectance method. MA and ME were measured at a physiological stretch (lambda = 1.4) and at a hypertensive stretch (lambda = 1.8) at four equispaced locations (z) along the DTA. When lambda was changed from 1.4 to 1.8, the average percentage change of MA was -2% and of ME was -4%. These decreases were not significant (P greater than 0.10), and we conclude that arterial wall stretch exerts only minor influence on the parameters governing albumin and EBD-albumin accumulation in the intimal surface of the deendothelialized arterial intimal-medial tissue system.

Targeting of lipid vesicles: specificity of carbohydrate receptor analogues for leukocytes in mice.

The presence of particular surface carbohydrate modifications is shown to affect dramatically the stability and tissue specificity of unilamellar distearoyl phosphatidylcholine vesicles in mice. Use of the gamma-ray probe 111In3+ permits analysis of tissue distributions by standard gamma counting techniques and determination of the structural integrity of the vesicles by perturbed angular correlation spectroscopy. Addition of a 6-aminomannose derivative of cholesterol to the lipid bilayer produces initial retention of high levels of intact vesicles in the lung after intravenous injection followed by concentration of intact vesicles in the liver and spleen. Vesicles bearing 6-aminosugar residues are found to concentrate in the axillary space in aggregates of polymorphonuclear leukocytes when administered subcutaneously. The in vivo stability of 6-aminomannose-labeled vesicles is substantially greater after intravenous or subcutaneous administration than that observed for any other system examined. The dose-response effects observed with surface modifications indicate that a particular receptor topography is important in the mechanism leading to transport and destruction of these vesicles.

Grain-boundary self-diffusion in Pb

We have carried out self-diffusion studies along grain boundaries in polycrystalline Pb specimen in the temperature range of 70–200 °C. Pb203 radioactive isotope (half life of 52.1 h) was used as a tracer, and precision microtome serial sectioning and high-efficiency gamma counting techniques were employed. The combined diffusion parameter δDb in Pb grain boundaries is expressed by the Arrhenius relation δDb=(6.1±0.9)×=10−9 exp(−0.46±0.01 eV/kT)(cm3/sec) .

Comparison of three radioligands, selenium-75, lodine-125, and tritium, in the radioimmunoassay of methotrexate.

Radioimmunoassays for methotrexate are described, involving use of a rabbit antiserum to a conjugate of the drug and bovine serum albumin and the drug labeled with tritium, selenium-75, or iodine-125. Of the two gamma emitters, the 75Se-labeled drug was prepared by the Radiochemical Centre, Amersham, England and the 125I-labeled drug in the laboratory, by the Chloramine T iodination technique. The stability of labels with both methods allows use of the faster, cheaper, and simpler gamma-counting techniques, with results available after 3 h. All three methods have acceptable sensitivity, accuracy, precision, and reproducibility, and are specific for methotrexate, with no significant interference from naturally occurring folates or leucovorin. The assays in which the gamma emitters are used have significant practical advantages over the beta emitter and are much better suited to automation and clinical application. The main advantage of 75Se=labeled methotrexate is its longer half-life, 121 days, as compared with 60 days for 125I.