Determination of 68 Ga production parameters by different reactions using ALICE and TALYS codes

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1 PRAMANA c Indian Academy of Sciences Vol. 72, No. 2 journal of February 2009 physics pp Determination of 68 Ga production parameters by different reactions using ALICE and TALYS codes MAHDI SADEGHI 1,, TAYEB KAKAVAND 2, LEILA MOKHTARI 2 and ZOHREH GHOLAMZADEH 1 1 Agricultural, Medical & Industrial Research School, P.O. Box , Karaj, Iran 2 Physics Faculty, Zanjan University, P.O. Box , Zanjan, Iran Corresponding author. msadeghi@nrcam.org MS received 12 July 2008; revised 22 September 2008; accepted 30 September 2008 Abstract. Gallium-68 (T 1/2 = 68 min, I β+ = 89%) is an important positron-emitting radionuclide for positron emission tomography and used in nuclear medicine for diagnosing tumours. This study gives a suitable reaction to produce 68 Ga. Gallium-68 excitation function via 68 Zn(p, n) 68 Ga, 68 Zn(d, 2n) 68 Ga, 70 Zn(p, 3n) 68 Ga and 65 Cu(α, n) 68 Ga reactions were calculated by ALICE-91 and TALYS-1.0 codes. The calculated excitation function of 68 Zn(p, n) 68 Ga reaction was compared with the reported measurement and evaluations. Requisite thickness of the targets was obtained by SRIM code for each reaction. The 68 Ga production yield was evaluated using excitation function and stopping power. Keywords. Gallium-68; excitation function; cyclotron; cross-section. PACS No Introduction The 68 Ga-labelled somatostatin derivatives have increasing applications in cancer imaging [1]. These compounds can be used for positron emission tomography (PET) imaging of tumours expressing somatostatin receptors. 68 Ga-based imaging agents to study pulmonary, myocardial and cerebral perfusion as well as renal and hepatobiliary function, to detect blood-brain barrier defect, to image tumour, brain and bone has been investigated [2 6]. It is employed for transmission measurements for encoding calibration and normalization of detector efficiencies of PET scanners [7]. There are four methods for the accelerator production of 68 Ga: (i) 68 Zn(p, n) 68 Ga, (ii) 68 Zn(d, 2n) 68 Ga, (iii) 70 Zn(p, 3n) 68 Ga and (iv) 65 Cu(α, n) 68 Ga. The 68 Zn(p, n) 68 Ga reaction has been studied by Tarkanyi et al [8], Szelecsenyi et at [9], Hermanne et al [10] and Howe [11] up to 30 MeV energy [8 11]. Gilly et al seems to be the only one to have studied 68 Zn(d, 2n) 68 Ga reaction. Their crosssection measured in the range of 5 to 12 MeV [12]. There is no data and excitation 335

2 Mahdi Sadeghi et al curve for 70 Zn(p, 3n) 68 Ga. Bonesso et al [13], Stelson and Mcgowan [14], Singh et al [15] and Bryant et al [16] have been working on 65 Cu(α, n) 68 Ga reaction below 30 MeV energy [13 16]. In this work, several methods for gallium-68 production using ALICE-91 and TALYS-1.0 have been studied. Theoretical yield and required thickness of target for reactions were calculated. Optimum reaction was compared with experimental data. 2. Methods 2.1 Calculation of excitation function Excitation function of 70 Zn+p, 65 Cu+α, 68 Zn+p and 68 Zn+d reactions were calculated using ALICE-91 and TALYS-1.0 codes [17 19]. The codes were used simultaneously to increase the accuracy of calculations Brief description of nuclear models applied for cross-section calculations The TALYS code: The pre-equilibrium particle emission is described using the two-component exciton model. The model implements new expressions for internal transition rates and new parametrization of the average squared matrix element for the residual interaction obtained using the optical model potential from refs [17,18]. The phenomenological model is used for the description of the pre-equilibrium complex particle emission. The equilibrium particle emission is described using the Hauser Feshbach model. The hybrid ALICE code: This code uses the Weisskopf Ewing evaporation model, the Bohr Wheeler model for fission and the geometry-dependent hybrid model for pre-compound decay. The hybrid model is relevant to the pre-compound decay but not to the compound decay. The hybrid means a marriage between two theories on the pre-compound decay. The geometry-dependent hybrid model is a further revision of the hybrid model. 2.2 Calculation of the required thickness of target According to SRIM (stopping and range of ions in matter) code, the required thickness of the target was calculated [20]. The physical thickness of the target layer is chosen in such a way that for a given beam/target angle geometry (90 ) the incident beam is exited from the target layer with predicted energy. To minimize thickness of the target layer, 6 geometry is preferred; so the required layer thickness will be less with coefficient 0.1. The calculated thicknesses are shown for ideal reactions in table 1. Table 1. Required thickness for 68 Ga production. Reaction 68 Zn(p, n) 68 Ga 68 Zn(d, 2n) 68 Ga 70 Zn(p, 3n) 68 Ga 65 Cu(α, n) 68 Ga Energy range (MeV) Recommended thickness of the target (µm) Pramana J. Phys., Vol. 72, No. 2, February 2009

3 Determination of 68 Ga production parameters Table Ga production yield for various reactions. Reaction 70 Zn(p, 3n) 68 Ga 68 Zn(d, 2n) 68 Ga 68 Zn(p, n) 68 Ga 65 Cu(α, n) 68 Ga Theoretical yield, ALICE code (GBq/µA h) Theoretical yield, TALYS code (GBq/µA h) Calculation of theoretical yield Enhancing the projectile energy, beam current and the time of bombardment increase the production yield. The production yield can be calculated by the equation Y = N E2 ( ) 1 LH de M I(1 e λt ) σ(e)de, (1) E 1 d(ρx) where Y is the activity (in Bq) of the product, N L is the Avogadro number, H is the isotope abundance of the target nuclide, M is the mass number of the target element, σ(e) is the cross-section at energy E, I is the projectile current, de/d(ρx) is the stopping power, λ is the decay constant of the product and t is the time of irradiation. The production yield of 68 Ga by different reactions was calculated using the Simpson numerical integral as in eq. (1) (table 2). 3. Results 3.1 Excitation function of 70 Zn(p,3n) 68 Ga reaction Excitation functions of the proton-induced reaction on zinc-70 were measured by ALICE-91 and TALYS-1.0 codes and evaluation of the acquired data showed that the best range of energy is 20 to 50 MeV. In this energy range, isotope impurity of 69 Ga (stable) has considerable excitation function compared to 68 Ga. The separation of isotope impurities is not possible by chemical methods, so this reaction is not carrier free for 68 Ga production. ALICE and TALYS codes predicted the maximum cross-section to be 680 mb at 31 MeV and 350 mb at 30 MeV respectively. According to SRIM code the required target thickness should be 390 µm. According to the cross-section data of ALICE-91 and TALYS-1.0 codes, 68 Ga production yields were and 5.85 GBq/µA h respectively (figure 1). 3.2 Excitation function of 65 Cu(α, n) 68 Ga reaction According to these codes, the optimum range of energy to produce 68 Ga via 65 Cu(α, n) 68 Ga reaction is 7 to 15 MeV. There is no isotopic impurity in this energy range. The non-isotopic impurities are 68 Zn (stable) and 65 Cu (stable). Pramana J. Phys., Vol. 72, No. 2, February

4 Mahdi Sadeghi et al Figure 1. Excitation function of 70 Zn(p, 3n) 68 Ga reaction. (a) ALICE code, Figure 2. Excitation function of 65 Cu(α, n) 68 Ga reaction. (a) ALICE code, The predicted maximum cross-sections were 928 mb and 700 mb at 15 MeV energy for ALICE and TALYS codes. The required target thickness should be 3.36 µm and 68 Ga production yields were 0.42 and 0.29 GBq/µA h for cross-section data of ALICE-91 and TALYS-1.0 codes respectively. Calculated TALYS data is in agreement with the cross-section value reported by Stelson et al (figure 2). 3.3 Excitation function of 68 Zn(d, 2n) 68 Ga reaction The acquired data from ALICE-91 and TALYS-1.0 codes showed that 68 Ga has full benefit excitation function of 7 to 70 MeV. Deuteron bombardment of zinc- 68 target produces the radionuclide impurity 67 Ga (73 h) that has long half-life compared to 68 Ga (1.1 h); its benefit excitation function is 16 up to 70 MeV. On the other hand, 69 Ga isotope (stable) will be produced from 7 to 16 MeV energy. Hence this reaction is not suitable for gallium-68 production in the energy range of MeV and is not carrier free in the other range. These codes predicted the maximum cross-section to be 1259 mb and 728 mb at 16 MeV. According to SRIM code, the required target thickness should be 44 µm. The calculated TALYS data are in agreement with the cross-section value reported by Gilly et al (figure 3). 338 Pramana J. Phys., Vol. 72, No. 2, February 2009

5 Determination of 68 Ga production parameters Figure 3. Excitation function of 68 Zn(d, 2n) 68 Ga reaction. (a) ALICE code, Figure 4. Excitation function of 68 Zn(p, n) 68 Ga reaction. (a) ALICE code, 3.4 Excitation function of 68 Zn(p, n) 68 Ga reaction Excitation functions of the proton-induced activities on zinc-68 were measured by the codes, and the evaluation of the acquired data showed that the best range of energy is from 4 to 13 MeV. In this energy range, there is no isotopic impurity. The non-isotopic impurities of 68 Zn (stable) and 65 Cu (stable) are separated easily using chemical methods. ALICE and TALYS codes predicted the maximum crosssection to be 896 mb at 13 MeV and 826 mb at 11 MeV respectively (figure 4). The physical thickness of the enriched zinc layer is obtained in such a way that for a given beam/target angle geometry the particle exit energy should be about 4 MeV. According to SRIM code, the thickness has to be 41 µm for 6 geometry. The codes results as well as those of Tarkanyi et al, Szelecsenyi et al, Hermanne et al and Howe are shown in figure Conclusion 70 Zn(p, 3n) 68 Ga and 68 Zn(d, 2n) 68 Ga reactions are not desirable to produce nocarrier-added of 68 Ga because of the production of isotopic impurities. Results of the calculations showed that production yield of 68 Ga via 68 Zn(p, n) 68 Ga will be as much as the other reactions. Production of 68 Ga can be achieved by 68 Zn(p, n) 68 Ga Pramana J. Phys., Vol. 72, No. 2, February

6 Mahdi Sadeghi et al Figure 5. Excitation function of 68 Zn(p, n) 68 Ga reaction from experimental data, TALYS-1.0 and ALICE-91 codes. ideal reaction for low energy cyclotrons (Cyclone 30, IBA, Belgium). Results of ALICE and TALYS codes are just in agreement with experimental data. References [1] H R Maecke, M Hofman and U Haberkon, Nucl. Med. 46(1), 172 (2005) [2] J F Eary and K A Krohn, Nucl. Med. 27, 1737 (2000) [3] M A Green and M J Welch, Nucl. Med. Bio. 16, 435 (1998) [4] C J Anderson and M J Welch, Chem. Rev. 99, 2219 (1999) [5] W Damian, R Helmut, W Beatrice, C R Jean, G Mihaela and H Michael, Nucl. Med. Mol. Imaging 32, 6 (2005) [6] W A Breeman, M De Jong, E De Blois, B F Bernard and M Konijnenberg, Eur. J. Nucl. Med. Mol. Imaging 32, 478 (2005) [7] F S Al-Saleh, K S Mugren and A Azzam, Appl. Radiat. Isot. 65, 1101 (2007) [8] F Tarkanyi, F Szelecsenyi, Z Kovacs and S Sudar, Radiochimica Acta 50, 19 (1990) [9] F Szelecsenyi, T E Boothe, S Takacs, F Tarkanyi and E Tavano, Appl. Radiat. Isot. 49, 1005 (1998) [10] A Hermanne, N Walravens and O Cicchelli, Optimization of isotope production by cross-section determination, in: Proc. of Int. Conf. Nuclear Data for Science and Technology edited by S M Qaim, May 1991, Jülich, Germany (Springer-Verlag, Berlin, 1992) p. 616 [11] H A Howe, Phys. Rev. 109, 2083 (1958) [12] J L Gilly, G A Henriet, M Preciosaalves and P C Capron, Phys. Rev. 131(4), 1727 (1963) [13] O Bonesso, M J Ozafran, H O Mosca, M E Vazquez, O A Capurro and S J Nassiff, Radioanal. Nucl. Chem. 152(1), 189 (1991) [14] P H Stelson and F K Mcgowan, Phys. Rev. B133, 911 (1964) 340 Pramana J. Phys., Vol. 72, No. 2, February 2009

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