Activation cross sections of α-particle induced nuclear reactions on hafnium and deuteron induced nuclear reaction on tantalum: Production of 178W/178mTa generator

In the frame of a systematic study of charged particle production routes of medically relevant radionuclei, the excitation function for indirect production of ^178mTa through ^natHf(α,xn)¹⁷⁸W–^178mTa nuclear reaction was measured for the first time up to 40 MeV. In parallel, the side reactions ^natHf(α,x)^{179,177,176,175}W, ^{183,182,178g,177,176,175}Ta, ^{179m,177m,175}Hf were also assessed. Stacked foil irradiation technique and γ-ray spectrometry were used. New experimental cross section data for the ^natTa(d,xn)¹⁷⁸W reaction are also reported up to 40 MeV. The measured excitation functions are compared with the results of the ALICE-IPPE, and EMPIRE nuclear reaction model codes and with the TALYS 1.4 based data in the TENDL-2013 library. The thick target yields were deduced and compared with yields of other charged particle ((p,4n), (d,5n) and (³He,x)) production routes for ¹⁷⁸W.     

New measurement of excitation functions for (d,x) reactions on natMo with special regard to the formation of 95mTc, 96m+gTc, 99mTc and 99Mo

Cross-sections for the deuteron-induced reactions on natural molybdenum leading to ^93mTc, ^93m+gTc, ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m+gTc, ^99mTc, ⁹⁹Mo, ¹⁰¹Mo, ^90m+gNb, ^92mNb, ⁹⁵Nb and ^89m+gZr were measured in the energy range 3.0–19.6 MeV on the cyclotron U-120 M in the Institute of Nuclear Physics AS CR. Special attention was paid to excitation functions and thick target yields for the formation of ^95mTc, a suitable tracer for ⁹⁹Tc, of ^96m+gTc, which might be used as a beam monitor, and of ^99mTc and ⁹⁹Mo, the most widespread radionuclide generator pair in nuclear medicine. If appropriate, obtained data are compared with the heretofore published cross-sections.     

Production of the mercury-197 through proton induced reaction on gold

The excitation function of the proton exchange reactions on gold was investigated in the energy range from threshold up to 20 MeV. We presented our experimental results upto 14 MeV stacked-foil technique was used, the target was of high purity gold foils (99.99%.) Reactions cross-sections and excitation functions were studied. Both isomeric level cross sections of ¹⁹⁷Hg were measured and calculated theoretically using the DDHMS routine of the EMPIRE-II (v2.19) code. Isomeric cross-section ratios for the pair ^197m,gHg were calculated and presented as a function of proton energy.     

Separation of no-carrier-added 93,94,94m,95,96Tc from 7Li induced natural Zr target by liquid–liquid extraction

Charged particle activation was carried out on ^natZr foil by 42.5 MeV ⁷Li beam to produce ^{93,94,94m,95,96}Tc radionuclides. No-carrier-added (nca) technetium radionuclides were separated from co-produced ^90,96Nb and bulk Zr employing liquid–liquid extraction with the help of anion exchanger trioctylamine (TOA) diluted in cyclohexane and HCl. Bulk Zr was monitored by spiking ^88,89Zr produced by 20 MeV proton induced reaction on ^natY target. The optimum separation was achieved at 0.1 M TOA and 0.01 M HCl. Technetium radionuclides were recovered from the TOA phase by stripping with 0.1 M DTPA (diethylene triamine pentaacetic acid) dissolved in NaOH.     

Excitation functions of 93Nb(n, 2n) 92mNb, 93Nb(n, α)90m,gY, 139La(n, α)136Cs and 181Ta(n,p)181Hf reactions in the energy range of 12.5–19.6 MeV

Cross sections were measured for the ⁹³Nb(n, 2n) ^92mNb, ⁹³Nb(n, α) ^90m,gY, ¹³⁹La(n, α)¹³⁶Cs and ¹⁸¹Ta(n, p)¹⁸¹Hf reactions in the energy range of 12.5–19.6 MeV. Use was made of the activation technique in combination with high-resolution γ-ray spectroscopy, except for the product ^90gY where radiochemical separation and β⁻ counting were applied. The neutron fluence rates were determined using two independent methods, viz. proton recoil telescope and ²⁷Al(n, α)²⁴Na monitor reaction. An appraisal of the available cross section data for the five investigated processes was carried out. Due to its relatively high importance as a dosimetry reaction an evaluation of the ⁹³Nb(n, 2n) ^92mNb excitation function based on the most recent data is recommended. For the other reactions our measurements furnish an extended data base. A comparison of the experimental data with values calculated from the semi-empirical code THRESH is presented. The code predicts unknown activation cross sections only with partial success.     

Cross section measurements of proton and deuteron induced reactions on natural europium and yields of SPECT-relevant radioisotopes of gadolinium

The existing cross section data of the ^natEu(d,x) and ^natEu(p,x) reactions relevant for the production of ^147,149Gd were expanded up to 70.9 MeV and 44.8 MeV, respectively. Integral yields of radiogadolinium were calculated, showing production rates higher than for the earlier proposed irradiation of highly enriched ¹⁴⁴Sm with α- or ³He-particles. The formation of radioisotopic impurities like ¹⁵¹Gd (T_1/2=124 d) and ¹⁵³Gd (T_1/2=240 d) was below 5%. Production of ^147,149Gd using enriched europium is also discussed.     

Radiochemical determination of cross sections of α-particle induced reactions on 192Os for the production of the therapeutic radionuclide 193mPt

For determination of cross sections of α-particle induced reactions on 99.65% enriched ¹⁹²Os, the methods for electrolytic preparation of thin samples and radiochemical separation of radioplatinum were optimized. The excitation functions of the ¹⁹²Os(α,n)^195mPt and ¹⁹²Os(α,3n) ^193mPt reactions were measured from 20 to 39 MeV. The cross section of the latter reaction reaches a maximum value of about 1.5 b at an energy around 36 MeV. The results of nuclear model calculations using the codes TALYS and STAPRE agreed well with the measured data. The optimum energy range for the production of no-carrier-added ^193mPt (T_1/2=4.33 d) was found to be E_α=40→30 MeV. The thick target yield amounts to 10 MBq/μA h and a possible batch yield of 2 GBq should be sufficient for Auger electron therapy on a wide scale.     

Production of medical radioisotopes with linear accelerators

In this study, we discuss producing radioisotopes using linear electron accelerators and address production and separation issues of photoneutron (γ,n) and photoproton (γ,p) reactions. While (γ,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both are the same. Yields of (γ,p) reactions are typically lower than (γ,n) ones, however they have the advantage that target and product nuclides belong to different chemical species so their separation is often not such an intricate problem. In this paper we consider two examples, ¹⁰⁰Mo(γ,n)⁹⁹Mo and ⁶⁸Zn(γ,p)⁶⁷Cu, of photonuclear reactions. Monte-Carlo simulations of the yields are benchmarked with experimental data obtained at the Idaho Accelerator Center using a 44 MeV linear electron accelerator. We propose using a kinematic recoil method for photoneutron production. This technique requires ¹⁰⁰Mo target material to be in the form of nanoparticles coated with a catcher material. During irradiation, ⁹⁹Mo atoms recoil and get trapped in the coating layer. After irradiation, the coating is dissolved and ⁹⁹Mo is collected. At the same time, ¹⁰⁰Mo nanoparticles can be reused. For the photoproduction method, ⁶⁷Cu can be separated from the target nuclides, ⁶⁸Zn, using standard exchange chromatography methods. Monte-Carlo simulations were performed and the ⁹⁹Mo activity was predicted to be about 7 MBq/(g^⁎kW^⁎h) while ⁶⁷Cu activity was predicted to be about 1 MBq/(g^⁎kW^⁎h). Experimental data confirm the predicted activity for both cases which proves that photonuclear reactions can be used to produce radioisotopes. Lists of medical isotopes which might be obtained using photonuclear reactions have been compiled and are included as well.     

Assessment of radionuclidic impurities in cyclotron produced 99mTc

IntroductionThe commercial viability of cyclotron-produced ^99mTc as an alternative to generator-produced ^99mTc depends on several factors. These include: production yield, ease of target processing and recycling of ¹⁰⁰Mo, radiochemical purity, specific activity as well as the presence of other radionuclides, particularly various Tc radioisotopes that cannot be separated chemically and will remain in the final clinical preparation. These Tc radionuclidic impurities are derived from nuclear interactions of the accelerated protons with other stable Mo isotopes present in the enriched ¹⁰⁰Mo target. The aim of our study was to determine experimentally the yields of Tc radioisotopes produced from these stable Mo isotopes as a function of incident beam energy in order to predict radionuclidic purity of ^99mTc produced in highly enriched ¹⁰⁰Mo targets of known isotopic composition.MethodsEnriched molybdenum targets of ⁹⁵Mo, ⁹⁶Mo, ⁹⁷Mo, ⁹⁸Mo and ¹⁰⁰Mo were prepared by pressing powdered metal into an aluminum target support. The thick targets were bombarded with 10 to 24 MeV protons using the external beam line of the U-120 M cyclotron of the Nuclear Physics Institute, ?e?. The thick target yields of ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m + gTc and ^97mTc were derived from their activities measured by γ spectrometry using a high purity Ge detector. These data were then used to assess the effect of isotopic composition of highly enriched ¹⁰⁰Mo targets on the radionuclidic purity of ^99mTc as a function of proton beam energy. Estimates were validated by comparison to measured activities of Tc radioisotopes in proton irradiated, highly enriched ¹⁰⁰Mo targets of known isotopic composition.ResultsThe measured thick target yields of ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m + gTc and ^97mTc correspond well with recently published values calculated via the EMPIRE-3 code. However, the measured yields are more favourable with regard to achievable radionuclidic purity of ^99mTc. Reliability of the measured thick target yields was demonstrated by comparison of the estimated and measured activities of ⁹⁴Tc, ⁹⁵Tc, ^95mTc, and ^96m + gTc in highly enriched ¹⁰⁰Mo (99%) targets that showed good agreement, with maximum differences within estimated uncertainties. Radioisotopes ^94mTc and ^97mTc were not detected in the irradiated ¹⁰⁰Mo targets due to their low activities and measurement conditions; on the other hand we detected small amounts of the short-lived positron emitter ⁹³Tc (T_½ = 2.75 h). In addition to ^99mTc and trace amounts of the various Tc isotopes, significant activities of ⁹⁶Nb, ⁹⁷Nb and ⁹⁹Mo were detected in the irradiated ¹⁰⁰Mo targets.ConclusionsRadioisotope formation during the proton irradiation of Mo targets prepared from different, enriched stable Mo isotopes provides a useful data base to predict the presence of Tc radionuclidic impurities in ^99mTc derived from proton irradiated ¹⁰⁰Mo targets of known isotopic composition. The longer-lived Tc isotopes including ⁹⁴Tc (T_½ = 4.883 h), ⁹⁵Tc (T_½ = 20.0 h), ^95mTc (T_½ = 61 d), ^96m + gTc (T_½ = 4.24 d) and ^97mTc (T_½ = 90 d) are of particular concern since they may affect the dosimetry in clinical applications. Our data demonstrate that cyclotron production of ^99mTc, using highly enriched ¹⁰⁰Mo targets and 19–24 MeV incident proton energy, will result in a product of acceptable radionuclidic purity for applications in nuclear medicine.     

Excitation function of the 64Ni(α,p)67Cu reaction for production of 67Cu

The excitation function of the ⁶⁴Ni(α,p)⁶⁷Cu reaction was measured from threshold up to 24 MeV in order to investigate the possibility of production of the β⁻-emitting therapeutic radioisotope ⁶⁷Cu (T_1/2=61.9 h). Two stacks of thin metallic self-supporting foils of ⁶⁴Ni (enrichment 77.8%) prepared by electrolytic deposition were irradiated by α-particle beams. The radioactivity was determined via HPGe detector γ-ray spectrometry. Some ⁶⁷Ga activity (which emits the same γ-rays as ⁶⁷Cu), formed via the ^natCu(α,x)⁶⁷Ga process on trace copper impurity in the Ni foils, was also observed. Corrections were done for ⁶⁷Ga activity contribution and for the ⁶⁷Cu activity escape fraction from the thin Ni-foil. The maximum cross section of the ⁶⁴Ni(α,p)⁶⁷Cu reaction amounts to 34 mb at 22 MeV. The experimental results were compared with theoretical predictions. The integral yield of ⁶⁷Cu at 24 MeV α-particle energy, calculated from the excitation function, amounts to 544 KBq/μAh (48.5 MBq/μA at saturation). It is thus a low-yield reaction.     

Cross section measurement for the 95Mo(n, α)92Zr reaction at 4.0, 5.0 and 6.0 MeV

Measurements of cross sections of the ⁹⁵Mo(n, α)⁹²Zr reaction at E_n=4.0, 5.0 and 6.0 MeV were carried out at the 4.5 MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area ⁹⁵Mo samples were adopted. Fast neutrons were produced through the D(d, n)³He reaction by using a deuterium gas target. A small ²³⁸U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement.     

Investigation of the natZn(p,x)62Zn nuclear process up to 70 MeV: a new 62Zn/62Cu generator

The excitation function of the ^natZn(p,x)⁶²Zn nuclear process was measured by the stacked-foil technique up to a proton energy of 70 MeV to obtain accurate data for production of the ‘mother nuclide’ (⁶²Zn) of the PET related β⁺ emitting radioisotope ⁶²Cu. Investigations were also made on the ⁶⁶Zn(p,x)⁶²Zn and ^natZn(p,xn)⁶⁶Ga processes and on the ⁶⁶Zn(p,n)⁶⁶Ga reaction using ^natZn and highly enriched ⁶⁶Zn. The excitation functions were compared with the published data. Thick target yields for the ^natZn(p,x)⁶²Zn and ^natCu(p,xn)⁶²Zn processes were also calculated up to 70 MeV. On the basis of these calculations the ^natZn+p process results in higher yield for ⁶²Zn above 50 MeV than the ^natCu+p process. The latter process is presently used for practical production of ⁶²Zn. In an energy window from 70 to 30 MeV the available EOB yield of the ^natZn+p reactions is around 19 mCi/μA h (0.7 GBq/μAh) that makes the ^natZn(p,x)⁶²Zn process a good candidate for routine generator production.     

Excitation functions of proton-induced reactions on natFe and enriched 57Fe with particular reference to the production of 57Co

Excitation functions of the reactions ^natFe(p,xn)^55,56,57,58Co, ^natFe(p,x)⁵¹Cr, ^natFe(p,x)⁵⁴Mn, ⁵⁷Fe(p,n)⁵⁷Co and ⁵⁷Fe(p,α)⁵⁴Mn were measured from their respective thresholds up to 18.5 MeV, with particular emphasis on data for the production of the radionuclide ⁵⁷Co (T_1/2=271.8 d). The conventional stacked-foil technique was used, and the samples for irradiation were prepared by an electroplating or sedimentation process. The measured excitation curves were compared with the data available in the literature as well as with results of nuclear model calculations. From the experimental data, the theoretical yields of the investigated radionuclides were calculated as a function of the proton energy. Over the energy range E_p=15→5 MeV the calculated yield of ⁵⁷Co from the ⁵⁷Fe(p,n)⁵⁷Co process amounts to 1.2 MBq/μA h and from the ^natFe(p,xn)⁵⁷Co reaction to 0.025 MBq/μA h. The radionuclidic impurity levels are discussed. Use of highly enriched ⁵⁷Fe as target material would lead to formation of high-purity ⁵⁷Co.     

Yield and purity of 82Sr produced via the natRb(p,xn)82Sr process

The recently reported cross-section data for the production of ⁸²Sr via the ^natRb(p,xn)⁸²Sr process were evaluated. For the ^natRb(p,xn)⁸⁵Sr process, cross-sections were measured experimentally over the proton energy range of 25–45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of ⁸⁵Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide ⁸²Sr and the impurity ⁸⁵Sr were calculated. Yields were also determined experimentally over several energy ranges using thick ^natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of ⁸²Sr, an incident proton energy of 60 MeV or above is recommended; the ⁸⁵Sr impurity then corresponds to <20%.     

Study of activation cross sections of proton induced reactions on barium: Production of 131Ba→131Cs

In the frame of a systematic study of charged particle production routes of the therapeutic radioisotope ¹³¹Cs, excitation functions of the ^natBa(p,x)^135,132mgLa, ^{ind135m,cum133m,cum133mg,cum131mg}Ba and ^{136mg,134mg,132,cum129}Cs reactions were measured in the 30?70 MeV energy range using stacked foil irradiation technique, activation method and gamma spectroscopy. Comparisons with new results of the ALICE-IPPE and EMPIRE-II codes and with existing data obtained with TALYS code are shown. From the measured cross section data integral yields were calculated and compared with experimental integral yield data reported in the literature. Potential use of proton induced reactions on Ba for production of ¹³¹Cs is discussed.     

Excitation function of 3He-particle induced nuclear reactions on natural palladium

Excitation functions of ³He-particle induced nuclear reactions on natural palladium were measured using the standard stacked foil technique and high resolution γ-ray spectroscopy. From their threshold energies up to 27 MeV, cross-sections for ^natPd(³He,x)^{103,104,105,106m,110m,111,112}Ag and ^natPd(³He,x)^{104,105,107,111m}Cd reactions were measured. The nuclear model codes TALYS-1.4, and EMPIRE-3.1 were used to describe the formation of these products. The present data were compared to theoretical results and to the available experimental data. Integral yields for some important radioisotopes were determined.     

The backwards comparability of wrist worn GENEActiv and waist worn ActiGraph accelerometer estimates of sedentary time in children

ObjectivesTo examine the backward comparability of a range of wrist-worn accelerometer estimates of sedentary time (ST) with ActiGraph 100 count min⁻¹ waist ST estimates.DesignCross-sectional, secondary data analysisMethodsOne hundred and eight 10–11-year-old children (65 girls) wore an ActiGraph GT3X+ accelerometer (AG) on their waist and a GENEActiv accelerometer (GA) on their non-dominant wrist for seven days. GA ST data were classified using a range of thresholds from 23 to 56 mg ST estimates were compared to AG ST 100 count min⁻¹ data. Agreement between the AG and GA thresholds was examined using Cronbach’s alpha, intraclass correlation coefficients (ICC), limits of agreement (LOA), Kappa values, percent agreement, mean absolute percent error (MAPE) and equivalency analysis.ResultsMean AG total ST was 492.4 min over the measurement period. Kappa values ranged from 0.31 to 0.39. Percent agreement ranged from 68 to 69.9%. Cronbach’s alpha values ranged from 0.88 to 0.93. ICCs ranged from 0.59 to 0.86. LOA were wide for all comparisons. Only the 34 mg threshold produced estimates that were equivalent at the group level to the AG ST 100 count min⁻¹ data though sensitivity and specificity values of ∼64% and ∼74% respectively were observed.ConclusionsWrist-based estimates of ST generated using the 34 mg threshold are comparable with those derived from the AG waist mounted 100 count min⁻¹ threshold at the group level. The 34 mg threshold could be applied to allow group-level comparisons of ST with evidence generated using the ActiGraph 100 count min⁻¹ method though it is important to consider the observed sensitivity and specificity results when interpreting findings.     

An Am/Be neutron source and its use in integral tests of differential neutron reaction cross-section data

An Am/Be neutron source, installed recently at the Rajshahi University, is described. Neutron flux mapping was done using the nuclear reactions ¹⁹⁷Au(n,γ)¹⁹⁸Au, ¹¹³In(n,γ)^114mIn, ¹¹⁵In(n,n′γ)^115mIn and ⁵⁸Ni(n,p)⁵⁸Co. An approximate validation of the neutron spectral shape was done using five neutron threshold detectors and the iterative unfolding code SULSA. Integral cross sections of the reactions ⁵⁴Fe(n,p)⁵⁴Mn, ⁵⁹Co(n,p)⁵⁹Fe and ⁹²Mo(n,p)^92mNb were measured with fast neutrons (E_n>1.5 MeV) and compared with data calculated using the neutron spectral distribution and the excitation function of each reaction given in data libraries: an agreement within±6% was found.     

Physical optimization of production by deuteron irradiation of high specific activity 177gLu suitable for radioimmunotherapy

Deuteron-induced nuclear reactions for generation of no-carrier-added (NCA) Lu isotopes were investigated using the stacked-foil activation technique on natural Yb targets at energies up to E_d = 18.18 MeV.The decay curve of ¹⁷⁷Yb, the growth curve of the cumulative (direct and indirect) and the direct production of ^177gLu were determined. The analysis of these curves conducts to the evidence that the predominant route for the production of ^177gLu is the indirect reaction ¹⁷⁶Yb(d,p)¹⁷⁷Yb, which decays to ^177gLu. In the spectra acquired one year from the EOB the γ lines of ^177mLu are not evident.A comparison between the calculated activity of ^177gLu produced with a cyclotron and with a nuclear reactor is given.     

Excitation functions of proton-induced reactions in natCu in the energy range 7–17 MeV

Elemental production cross sections were measured for (p,x) reactions on natural Cu targets, leading to the formation of ^62,63,65Zn. These reactions are generally used for monitoring the proton beam intensity and energy e.g. in isotope production facilities. Cross sections were obtained by activation of stacked foils and subsequent gamma spectroscopy. The production data for ^62,63,65Zn between 7 and 16.5 MeV proton energy are presented as well as comparisons with literature values. Good agreement with the evaluated values was found for most of the cross-section values.