Gamma Emission Probabilities Research Articles

Image-based dosimetry for [225Ac]Ac-PSMA-I&T therapy and the effect of daughter-specific pharmacokinetics

PurposeAlthough 221Fr and 213Bi have sufficient gamma emission probabilities, quantitative SPECT after [225Ac]Ac-PSMA-I&T therapy remains challenging due to low therapeutic activities. Furthermore, 221Fr and 213Bi may underlie a different pharmacokinetics due to alpha recoil. We conducted a quantitative SPECT study and a urine analysis to investigate the pharmacokinetics of 221Fr and 213Bi and the impact on image-based lesion and kidney dosimetry.MethodsFive patients (7.7 ± 0.2 MBq [225Ac]Ac-PSMA-I&T) underwent an abdominal SPECT/CT (1 h) at 24 and 48 h (Siemens Symbia T2, high-energy collimator, 440 keV/218 keV (width 20%), 78 keV (width 50%)). Quantitative SPECT was reconstructed using MAP-EM with attenuation and transmission-dependent scatter corrections and resolution modelling. Time-activity curves for kidneys (CT-based) and lesions (80% isocontour 24 h) were fitted mono-exponentially. Urine samples collected along with each SPECT/CT were measured in a gamma counter until secular equilibrium was reached.ResultsMean kidney and lesion effective half-lives were as follows: 213Bi, 27 ± 6/38 ± 10 h; 221Fr, 24 ± 6/38 ± 11 h; 78 keV, 23 ± 7/39 ± 13 h. The 213Bi-to-221Fr kidney SUV ratio increased by an average of 9% from 24 to 48 h. Urine analysis revealed an increasing 213Bi-to-225Ac ratio (24 h, 0.98 ± 0.15; 48 h, 1.08 ± 0.09). Mean kidney and lesion absorbed doses were 0.17 ± 0.06 and 0.36 ± 0.1 SvRBE=5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{Sv}}}_{{\ ext{RBE}}=5}$$\\end{document}/MBq using 221Fr and 213Bi SPECT images, compared to 0.16 ± 0.05/0.18 ± 0.06 and 0.36 ± 0.1/0.38 ± 0.1 SvRBE=5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{Sv}}}_{{\ ext{RBE}}=5}$$\\end{document}/MBq considering either the 221Fr or 213Bi SPECT.ConclusionSPECT/CT imaging and urine analysis showed minor differences of up to 10% in the daughter-specific pharmacokinetics. These variances had a minimal impact on the lesion and kidney dosimetry which remained within 8%.

Gamma Spectrometry results for the 134Cs nuclear parameters / Resultados de espectrometria gama para os parâmetros nucleares 134Cs

134Cs is produced directly as a fission product (low yield) and too obtained by neutron capture from 133Cs non-radioactive . The National Laboratory for Ionizing Radiation Metrology (LNMRI/IRD/CNEN) of Rio de Janeiro performed standardization of this radionuclide . A solution of 134Cs radionuclide was purchased from commercial supplier to nuclear parameters determination such as activity and emission probabilities of some of its energies. 134Cs is a beta gamma emitter with 754 days of half-life. This radionuclide is used as standard in environmental, water and food control. It is also important to germanium detector calibration The gamma emission probabilities were determined mainly for some energies of the 134Cs by efficiency curve method and the mostly uncertainties obtained were around 1.5 %.

Experimental set-up for the simultaneous measurement of fission and γ-emission probabilities induced by transfer or inelastic-scattering reactions

Fission and gamma-emission probabilities induced by transfer or inelastic scattering reactions with light projectile nuclei are very valuable quantities for constraining the models that describe the de-excitation of heavy nuclei. We have developed an experimental set-up that allows us to simultaneously measure fission and gamma-emission probabilities. The measurement of the gamma-emission probability at excitation energies where the fission channel is open is challenging due to the intense background of gamma rays emitted by the fission fragments. We discuss the procedure to subtract such a background and the constraints that this subtraction and other experimental conditions put on the set up. We show that our set-up complies with these constraints.

New evaluated radioxenon decay data and its implications in nuclear explosion monitoring

This work presents the last updated evaluations of the nuclear and decay data of the four radioxenon isotopes of interest for the Comprehensive Nuclear-Test-Ban Treaty (CTBT): Xe-131 m, Xe-133, Xe-133 m and Xe-135. This includes the most recent measured values on the half-lives, gamma emission probabilities (Pγ) and internal conversion coefficients (ICC). The evaluation procedure has been made within the Decay Data Evaluation Project (DDEP) framework and using the latest available versions of nuclear and atomic data evaluation software tools and compilations. The consistency of the evaluations was confirmed by the very close result between the total available energy calculated with the present evaluated data and the tabulated Q-value. The article also analyzes the implications on the variation of the activity ratio calculations from radioxenon monitoring facilities depending on the nuclear database of reference.

134Cs emission probabilities determination by gamma spectrometry

The National Laboratory for Ionizing Radiation Metrology (LNMRI/IRD/CNEN) of Rio de Janeiro performed primary and secondary standardization of different radionuclides reaching satisfactory uncertainties. A solution of 134Cs radionuclide was purchased from commercial supplier to emission probabilities determination of some of its energies. 134Cs is a beta gamma emitter with 754 days of half-life. This radionuclide is used as standard in environmental, water and food control. It is also important to germanium detector calibration. The gamma emission probabilities (Pγ) were determined mainly for some energies of the 134Cs by efficiency curve method and the Pγ absolute uncertainties obtained were below 1% (k=1).

134Cs activity standardization by 4πβ(LS)-γ(NaI-Tl) anticoincidence counting and submission to international reference system

From a commercial supplier a solution containing 134Cs has been standardized at National Laboratory for Ionizing Radiation Metrology (LNMRI) for the first time using three Liquid scintillation based measurement. These measurement methods are 4πβ-γ live-timed anticoincidence counting, 4πβ-γ coincidence counting and 3H-standard efficiency tracing with the CNET methods. The results obtained by anticoincidence counting was adopted as reference value and its combined uncertainty was 0.38%. The agreement of this reference value with coincidence counting and CNET methods were 0.39% and 0.34% respectively and were in consistency with each uncertainty method. The weighted mean results coincidence counting and CNET methods are also in close agreement 0.03% with anticoincidence counting method and meets the requirement of primary and national standard.This standardization was made in order to reduce the uncertainty in 134Cs measurement in Brazil and also following a request made by Bureau International des Poids and Mesures for new submission to International Reference System. The LNMRI last submission was made in 1987. Therefore from a 134Cs master solution a NIST ampoules was prepared and LNMRI/IRD submitted it to the International Reference System, Bureau International of Poids and Measures (SIR/BIPM). In this paper will be analyzed the LNMRI measurement and performance each measurement methods and also take into account the reference value of KCDB, we determined also the 134Cs gamma emission probabilities of main energy.

Standardization of 106Ru/Rh by live-timed anticoincidence counting and gamma emission determination

The absolute activity standardization measurement system of radionuclide by live-timed anticoincidence counting was implemented at LNMRI in 2008 to reduce the effects of some correction factors on the determination of activity with coincidence counting technique used for decades in the laboratory, for example, the corrections of dead time and resolution.With the live-timed anticoincidence system, the variety of radionuclides that can be calibrated by LNMRI was increased in relation to the type of decay. The objective of this study was to standardize the 106Ru activity, determine gamma emission probabilities by spectrometric method for some energies, and estimate measurement uncertainties.

Determination of the gamma emission probabilities of 239Np

239 Np is an important nuclide as the decay daughter of 239 U and it decays to 239 Pu by emitting beta particles and gamma rays with a half life of 2.356 days. The data of the emission probabilities of its gamma-rays in the open references are consistent except for the main gamma-ray of 106.1 keV, the emission probability of which varies from 25.9% to 27.2%. To verify the emission probability of 106.1 keV gamma-ray of 239 Np, a N-type coaxial HPGe detector was calibrated using 241 Am, 133 Ba, 60 Co, 152 Eu and 155 Eu reference gamma sources to get the accurate efficiency of the 106.1 keV gamma-ray. 239 Np was purified from solution containing 243 Am, where 239 Np is the alpha decay daughter of 243 Am. The specific activity of 239Np solution was determined by a 4πβ (PC)-γ coincidence counting device. There were 6 gamma sources prepared to measure with the HPGe detector, and the activity of 239 Np in each gamma source was calculated with the weights of the solution contained in it. The emission probability of 106.1 keV of 239 Np is measured to be (25.4 ± 0.3)%, which is consistent with 25.34%, the value evaluated in 2014.

Determination of the 121Te gamma emission probabilities associated with the production process of radiopharmaceutical NaI[123I

The 123I is widely used in radiodiagnostic procedures in nuclear medicine. According to Pharmacopoeia care should be taken during its production process, since radionuclidic impurities may be generated. The 121Te is an impurity that arises during the 123I production and determining their gamma emission probabilities (Pγ) is important in order to obtain more information about its decay. Activities were also obtained by absolute standardization using the sum-peak method and these values were compared to the efficiency curve method.

Measurement of theγemission probability of173Yb using surrogate reactions

We performed the 174Yb(p,d) reaction in order to measure the gamma-emission probability of 173Yb. The identification of the ejectiles — allowing us to tag the production of 173Yb nuclei — was performed using the STARLiTeR detector system. Unusually, the “statistical“ γ-rays were used to determined the gammaemission probability and a spin distribution was extracted from it. A comparison with the spin distribution from the 174Yb(3He,α) reaction shows that the transferred angular momentum is similar in both reactions.

The 160.44 day 177 mLu as a new gamma calibration standard

Gamma emissions in the decay of 160.44 day isomer 177 m Lu were analyzed with a 60 cc, coaxial HPGe detector. The energies and intensities of 50 gamma transition – 40 of which belong to the daughter 177Hf, that was excited by beta decay of the isomer, and 10 to the isomeric transition in 177Lu were precisely determined. These precise values have resulted in an internally consistent decay scheme for 177 m Lu. These gamma intensity and gamma emission probability measurements will help in making the long lived 177 m Lu available as a calibration standard for HPGe detectors and also for other applications.

Activity determination and nuclear decay data of 113mCd

The radionuclide (113m)Cd was extracted from a Cd component, which has been irradiated in a research reactor during its routine operation. A validated separation procedure was then used to obtain a (113m)Cd solution of high radiochemical purity. The solution was measured by means of liquid scintillation counting for activity determination. To this end, the CIEMAT/NIST efficiency tracing method as well as the triple-to-double coincidence (TDCR) counting technique were used. Measurements in a low-background gamma-ray spectrometer were applied to identify any potential photon-emitting impurities and to measure the 263.7 keV photons from the isomer transition. A gamma emission probability of 0.01839(29)% was determined for this line. The liquid scintillation measurements were also used to evaluate the half-life of (113m)Cd. The decay was followed for about 11 months and a half-life T(1/2)=13.97(13) years was obtained.

Measurement of absolute gamma emission probabilities

The energies and emission probabilities (intensities) of gamma-rays emitted in radioactive decays of particular nuclides are the most important characteristics by which to quantify mixtures of radionuclides. Often, quantification is limited by uncertainties in measured intensities. A technique was developed to reduce these uncertainties. The method involves obtaining a pure sample of a nuclide using radiochemical techniques, and using appropriate fractions for beta and gamma measurements. The beta emission rates were measured using a liquid scintillation counter, and the gamma emission rates were measured with a high-purity germanium detector. Results were combined to obtain absolute gamma emission probabilities. All sources of uncertainties greater than 0.1% were examined. The method was tested with 38Cl and 88Rb.

Study of the gamma emission probability accompanying the spontaneous fission of 252Cf.

A study of the gamma emission accompanying the spontaneous fission process of 252Cf has been performed. The photon emission probability between 3 and 70 MeV and its angular dependence with respect to the fission direction were measured. These measurements were performed as a function of the mass asymmetry of the fission fragments. A large anisotropy in the energy region between 8 and 12 MeV has been found, confirming the results of a previous performed experiment [1]. This phenomena up till now remains unexplained.

Gamma emission probabilities in the decay of 241Pu and 237U, determined from the in-growth of 241Am

The decay rate of chemically purified 241Pu source material was determined by observation of the in-growth of the 59.5-keV γ-ray from the decay of the 241Am daughter over a period of 154 days. From the resulting source calibration and measurements of γ intensities, emission probabilities were determined for four γ-rays from the decay of 241Pu and for eight γ-rays from the decay of its 237U daugther. The uncertainties in the emission probabilities were less than 1% for the 148-keV γ-ray from 241Pu, and for the 65-, 165-, 208-, and 268-keV γ-rays from 237U. Uncertainties for the remaining γ-rays were between 1.0 and 4.2%. The applicability of the various transitions to the quantitative assay of 241Pu is discussed.

Application of two-stage 4 π LS - coincidence method in the measurement of 75Se activity

The method of activity measurements of 75Se with the use of a two-stage coincidence and liquid scintillation counter /LS/ has been presented. The main difficulty in 75Se counting is due to delay in gamma-ray emission of about 17 ms. The anticoincidence method can not be used, as the delay is too significant. The coincidence extrapolation method has been applied with efficiency function of X-ray and electron counting in LS. The extrapolated counting rate contains the decay rate of 75Se but also conversion electrons from the delayed gamma emission and some additional effect due to efficiency of LS for the delayed gamma rays. This effect is determined by the first correction factor. The second correction factor is concerned with the Compton effect in a gamma-ray-counting channel of the scintillation counter with NaI(Tl) crystal, i.e. scattered gamma rays from the delayed gamma rays. This effect can not be avoided even if the channel window is set in such a way that the delayed radiation was not counted directly. The second correction factor was obtained from 51Cr measurements, where the detector efficiency was calculated for the scattered gamma rays from the 320-keV gamma ray. The results of activity measurements are given in the paper with random + systematic counting uncertainty of 0,6 % at a 0,99 confidence level (6 df). The presented method was applied in activity measurements of 75Se sources used for the determination of the gamma-emission probability of this radionuclide and also for the standardization of a 75Se solution.

An idealized theory of the gamma-ray detection mechanism of a simple Moxon-Rae-type detector

A theory of the gamma-ray detection mechanism of a simple Moxon-Rae detector is proposed. The development of the theory is presented in terms of the probability functions appropriate to the production and transmission of electrons resulting from the (γ, e) processes in the converter material. The converter in our treatment is assumed to be graphite and the (γ, e) processes are taken to be Compton scattering. The assumptions made in the calculations of the various probabilities are discussed. Brief discussions of the gamma emission probability (strictly of nuclear origin) and the geometrical probability (indicating the effects of angular correlations) have also been included. Our treatment shows that approximate linearity of the γ-detection efficiency derives jointly from the electron-production and -transmission probability functions. The sharp decrease in the γ-detection efficiency from linearity for E γ <1 MeV is characteristic of the proposed theory and is in general agreement with the experimental observations. Directions for further refinement of the theory have been suggested.

Evidence for Anharmonic binding of isolated Fe impurity atoms

The temperature dependence of the recoil-free gamma emission probability for Fe/sup 57/ as a dilute impurity in metallic In was measured between 4 and 420 deg K. It is concluded that the binding forces cannot be predominately harmonic. This indicates that the properties of isolated atoms may differ markedly from these of the same type of atoms present in higher concentration. The experimental results May be qualitatively understood by considering the impurity atoms to reside in a spherical square well potential. (H.D.R.)

Two-Photon De-Excitation of the 0+ Level inZr90

The transition from the 1.73 Mev O+ excited state of Zr/sup 9//sup 0/ to the 0+ ground state is considered. Electromagnetic radiation is strongly forbidden, so that the only de-excitation modes are internal conversion, internal pair production, or gamma gamma emission. The gamma gamma emission is measured using coincidence techniques. The observed ratio of gamma gamma emission to internal conversion is smaller than predicted theoretically; it is suggested that an intermediate level with an energy>>1.73 Mev causes the low gamma gamma emission probability (T.F.H.)