Ingo Spahn

Enhanced production possibility of the therapeutic radionuclides 64Cu, 67Cu and 89Sr via (n, p) reactions induced by fast spectral neutrons

Summary Spectrum averaged cross sections for the 64Zn(n,p)64Cu, 67Zn(n,p)67Cu and 89Y(n,p)89Sr reactions were measured using a 14MeV d(Be) neutron source. In each case a clean radiochemical separation was performed and the radioactivity of the product was determined via high-resolution γ-ray spectrometry or anticoincidence β- counting. The cross sections are three to five times higher than with a fission neutron spectrum. It is postulated that at an intense fast spectral neutron source, e.g. a spallation source, it would be advantageous to use an (n,p) reaction: GBq amounts of 64Cu and 67Cu could be produced in one hour irradiation and of 89Sr in about one day irradiation.

Experimental studies and nuclear model calculations on proton induced reactions on manganese up to 45 MeV with reference to production of 55Fe, 54Mn and 51Cr

Excitation functions of the reactions (55)Mn(p,n)(55)Fe, (55)Mn(p,x)(54)Mn and (55)Mn(p,x)(51)Cr were measured from their respective thresholds up to 18 MeV in the first case and up to 45 MeV in the latter two cases, using the conventional stacked-foil technique. The radioactivity of (55)Fe was determined via high resolution X-ray spectrometry and of other radionuclides via high resolution γ-ray spectrometry. Nuclear model calculations were performed using the codes ALICE-IPPE, EMPIRE and TALYS. In some cases, good agreement was found between the experimental and theoretical data while in others considerable deviations were observed. From the experimental data the expected integral yields of the three investigated radionuclides were calculated.

Uses of alpha particles, especially in nuclear reaction studies and medical radionuclide production

Abstract Alpha particles exhibit three important characteristics: scattering, ionisation and activation. This article briefly discusses those properties and outlines their major applications. Among others, α-particles are used in elemental analysis, investigation and improvement of materials properties, nuclear reaction studies and medical radionuclide production. The latter two topics, dealing with activation of target materials, are treated in some detail in this paper. Measurements of excitation functions of α-particle induced reactions shed some light on their reaction mechanisms, and studies of isomeric cross sections reveal the probability of population of high-spin nuclear levels. Regarding medical radionuclides, an overview is presented of the isotopes commonly produced using α-particle beams. Consideration is also given to some routes which could be potentially useful for production of a few other radionuclides. The significance of α-particle induced reactions to produce a few high-spin isomeric states, decaying by emission of low-energy conversion or Auger electrons, which are of interest in localized internal radiotherapy, is outlined. The α-particle beam, thus broadens the scope of nuclear chemistry research related to development of non-standard positron emitters and therapeutic radionuclides.

Cross-section measurements for the formation of manganese-52 and its isolation with a non-hazardous eluent

Summary With respect to the production of no-carrieradded 52Mn nuclear reactions on natural chromium were investigated. Cross sections of the reactions natCr(p, x)48V, 48,49,51Cr, 52g,mMn were determined in the proton energy range of 7.6 to 45MeV. Additionally, production yields of 52g,mMn and 51Cr were measured in the energy range from 8.2 to 16.9MeV and therefrom the calculated saturation thick target yields were obtained as (2.55±0.31), (6.96±0.57), and (1.53±0.15) GBq/μA, respectively. For in vivo applications like PET, low toxicity is critical and sufficient activity of a radiolabelled compound mandatory. Thus, additional purification steps after separation of radionuclides and target materials have to be avoided. However, no isolation procedure has been reported in the literature so far where radiomanganese is directly obtained in a nonhazardous solution. Therefore a new separation procedure was developed utilizing the cation-exchange resin DOWEX 50W×8 (H+-form). 52gMn was quantitatively isolated from “bulk” chromium after 3 to 4 h in non-hazardous 0.067M ammonium citrate solution. Up to 99% of 52gMn activity was harvested within 10 to 15 mL eluent solution with no measureable 51Cr impurities.

Experimental study of the excitation functions of proton induced nuclear reactions on 167Er for production of medically relevant 167Tm

(167)Tm (T(1/2)=9.25d) is a candidate radioisotope for medical therapy and diagnostics due to its Auger-electron and low-energy X- and gamma-ray emission. Excitation functions of the (167)Er(p,n)(167)Tm reaction and (168)Er(p,n)(168)Tm, (167)Er(p,2n)(166)Tm, (166)Er(p,2n)(165)Tm disturbing reactions were measured up to 15MeV by using the stacked foil irradiation technique and gamma-ray spectroscopy. The measured excitation functions agree well with the results of ALICE-IPPE, EMPIRE-II and TALYS nuclear reaction model codes. The thick target yield of (167)Tm in the 15-8MeV energy range is 6.9MBq/microAh. A short comparison of charged particle production routes of (167)Tm is given.

Experimental determination of proton induced reaction cross sections on natNi near threshold energy

Abstract A newly developed facility at the 3 MV Tandem Accelerator at Dhaka for measurement of proton induced reaction cross sections in the energy region below 5 MeV is outlined and tests for the beam characterization are described. The results were validated by comparison with the well-known excitation function of the 64Ni(p, n)64Cu reaction. Excitation functions of the reactions natNi(p, x)60,61Cu, natNi(p, x)55,57,58m+gCo and natNi(p, x)57Ni were also measured from threshold to 16 MeV using the stacked-foil technique, whereby irradiations were performed with 5 MeV protons available at the Tandem Accelerator and 16.7 MeV protons at the BC 1710 cyclotron at Jülich, Germany. The radioactivity was measured using HPGe γ-ray detectors. A few results are new, the others strengthen the database. In particular, the results of the reaction natNi(p, x)61Cu below 3 MeV could serve as beam monitor.

Nuclear data for production of 88Y, 140Nd, 153Sm and 169Yb via novel routes

The possibilities of production of the therapy-related radionuclides 140Nd, 153Sm and 169Yb, and of 88Y, in no-carrier-added form were investigated. For 88Y production the nuclear processes natSr(p,xn)88Y and natRb(α, xn)88Y over the energy ranges Ep = 14→9 MeV and Eα = 18→12 MeV, respectively, can be utilised, although the former reaction is superior, both in terms of yield and radionuclidic purity. For 140Nd production the reactions 141Pr(p, 2n)140Nd and natCe(3He, xn)140Nd were investigated in detail. The optimum energy ranges are Ep = 30→15 MeV and E3He = 35→ 20 MeV, respectively. Both processes yield high-purity 140Nd. The former reaction, however, leads to a product yield about 17 times higher than the latter reaction, and is therefore to be preferred. In the case of 153Sm, investigations were done on the 153Eu(n,p)153Sm reaction with 14 MeV d(Be) neutrons as well as on the 150Nd(α, n)153Sm reaction. The yield of the (n,p) reaction is very low, but the (α, n) reaction over the energy range Eα = 25→15 MeV offers a good potential for production of no-carrier-added 153Sm in quantities sufficient for therapeutic applications. Also for the radionuclide 169Yb a novel route, viz.169Tm(p,n)169Yb reaction, was investigated. A critical comparison of this route with the commonly used (n, γ) route, however, showed that, due to the much higher cost involved, the (p,n) process should be utilised only when there is a real need of the high specific radioactivity product.

New cross section measurements for production of the positron emitters 75Br and 76Br via intermediate energy proton induced reactions

Abstract The radionuclides 75Br and 76Br are of considerable interest for application in Positron Emission Tomography (PET). For their production so far mostly low-energy or low-yield production processes have been employed. In this work the production of both isotopes was investigated using intermediate energy proton induced reactions and enriched target materials. Cross section data of the 77,78,80Se(p,xn)75Br processes were measured up to 66 MeV and those of the 77,78,80Se(p,xn)76Br processes up to 85 MeV. The measured excitation functions were compared with calculated results of the nuclear model code ALICE-IPPE. From the experimental excitation curves, thick target yields were calculated. They are fairly high over the investigated intermediate energy ranges. The production possibilities of 75Br and 76Br via various routes and the radionuclidic impurities associated with them are discussed.

Optimized separation procedure for production of no-carrier-added radiomanganese for positron emission tomography

Abstract The natCr(p, xn)-process is a very efficient route for production of 52gMn (T1/2 = 5.59 d). Based on measurements of distribution coefficients with different media and ion-exchange resins, an optimized chromatographic separation of radiomanganese from natCr with the resin Amberlite CG400 was developed. With this system natCr is eluted first with an acetic acid/methanol 1:1 mixture at room temperature and 52gMn thereafter with 3 M HCl at 50 ℃. Within a separation time of 4 h the method yielded 99.5% of the n.c.a. 52gMn in 2–3 mL of 3 M HCl. An ICP-MS analysis revealed a chromium impurity of 0.07 mg (0.014%) in the n.c.a. 52gMn solution, making this separation method suitable for the production of 52gMn for medical applications like positron emission tomography (PET).

New cross section measurements for the production of the Auger electron emitters 77Br and 80mBr

Abstract The two Auger electron emitting radionuclides of bromine, namely 77Br (T1/2=57.04 h) and 80mBr (T1/2=4.4 h), are promising candidates for internal radiotherapy. In this work, nuclear reaction cross sections were determined for their production using enriched Se targets. Thin Se samples were irradiated with incident protons of energies up to 85 MeV and the induced radioactivity was measured via non-destructive γ-ray spectroscopy, allowing the determination and extension of the excitation functions of the four reactions 77,78,80Se(p,ߙxn) 77Br and 80Se(p,ߙn)80mBr. The possible thick target yields were calculated and the different production routes discussed, especially with regard to the yield and the radionuclidic purity of the produced radionuclides.