Excitation Functions of Proton-Induced Reactions on natSn
and natCd: Relevance to the Production of 111In and 114mIn for
Medical Applications
F. Tárkányi1, F. Ditrói1, S. Takács1, I. Mahunka1, J. Csikai1, M. S. Uddin2,
M. Hagiwara2, M. Baba2, T. Ido2, A. Hermanne3, Yu. Shubin4, and A. I. Dityuk4
1
Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary
2
Cyclotron and Radioisotope Center, Tohoku University, Sendai, Japan
3
Cyclotron Laboratory, Vrije Universiteit Brussel, Brussels, Belgium
4
Institute of Physics and Power Engineering, Obninsk, Russian Federation
Abstract: Excitation functions of proton induced nuclear reactions were measured for application purposes up to 80 MeV
proton energies on natural Cd and Sn targets. The measured excitation functions were compared with the experimental results
reported in the literature and with the results of theoretical calculations using the ALICE-IPPE code. In the present work we
report on the excitation functions, the deduced integral yields and impurity levels related to the production of the medical
radioisotopes of indium (111In, 114mIn). High energy production routes by using Cd, In and Sn targets are compared.
composition. The possible advantage of these production
routes: no difficulties with commonly used, expensive,
highly enriched targets (111Cd, 112Cd, 113Cd, 114Cd), high
production yields due to the high target thickness. For
production of 111In and 114mIn by using highly penetrating
protons up to 100 MeV only stable isotopes of Sn, In and
Cd can serve as targets. Out of them the In target results
in a not carrier free 114mIn. Carrier free 111In can only be
obtained via a generator method by short irradiation
(1-2 h) and separation of the produced Sn isotopes. The
111
Sn has short half-life (35.3 min), and completely
decays to 111In. The other In decay-products of the
simultaneously produced Sn radioisotopes are shortlived compared with 111In. The cross sections, the
targetry and the separation method for In were
investigated in detail by the South African group [3, 4].
In this study we determined the excitation functions,
production yields and impurity levels for production of
the medically used 111In and 114mIn via proton irradiation
of Sn and Cd targets.
INTRODUCTION
The 111In (T1/2=2.8 day) isotope is used both for
diagnostic and therapeutic purposes and 114mIn (T1/2=
49.5 day) is a therapeutic radioisotope. Some neutron
deficient radioisotopes of indium - 110In (T1/2=69.1 min),
109
In (T1/2=4.2 h) and 108m,gIn (T1/2= 39.6 min and
T1/2=58.0 min) - have importance as analogs to follow
the bio-distribution of the diagnostic and therapeutic
radioisotopes of indium by using high resolution,
quantitative PET technology. The 111In and 114mIn
radioisotopes are on the list of the medical radioisotopes
of IAEA for production of which recommended cross
section database is required [1, 2].
In the frame of the systematic investigation of the
excitation functions of the light ion induced reactions on
different targets up to 100 MeV, cross sections of proton
induced nuclear reactions on Cd and Sn targets were
measured. These newly obtained data have various
practical applications. Here we present data for
production of medical radioisotopes by using medium
energy cyclotrons and targets with natural isotopic
CP769, International Conference on Nuclear Data for Science and Technology,
edited by R. C. Haight, M. B. Chadwick, T. Kawano, and P. Talou
© 2005 American Institute of Physics 0-7354-0254-X/05/$22.50
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Earlier Investigations
NEW RESULTS AND COMPARISONS
According to our knowledge no earlier results are
available in this energy range in the literature for
reactions on Sn targets. In the case of Cd the available
cross section data are contradicting. Cross sections on
nat
Cd up to 200 MeV protons were measured by Nortier
et al. [3], and by Zaitseva et al. [5] up to 63 MeV. By
comparing the two results the excitation functions show
a significant energy shift. The data of Zaitseva et al.
contradict not only those obtained by Nortier et al. on
nat
Cd, but also their own results measured on
monoisotopic enriched targets of Cd.
Excitation Functions
The excitation functions were measured for
production of 111In and 114mIn as well as for the possible
contaminants. Here we report on the cross section of the
main products.
nat
Sn Target
The measured excitation functions are shown in
Fig. 1 in comparison with the theoretical calculation. In
spite of the long measuring time, the counting statistics
for the gamma-lines from the decay of 114mIn was poor.
As it was mentioned no other experimental data were
found in the literature. The theoretical curve represents
the sum of the activation cross section of the metastable
and ground states and in such a way forms an upper limit
for production of the metastable state.
EXPERIMENTAL AND DATA
EVALUATION
The excitation functions for production of 111,114mIn
radioisotopes were measured from the respective
thresholds up to 80 MeV by using an activation method,
the stacked foil irradiation technique and direct HpGe
gamma counting of irradiated samples. The irradiations
were done at an external beam line of the Tohoku
University (Sendai, Japan) and Vrije Universiteit Brussel
(Brussels, Belgium) cyclotrons. The beam intensity and
the energy degradation were controlled in the whole
energy
range
by
simultaneously
measured
nat
Al(p,x)22,24Na and natCu(p,x)56,58Co,62,65Zn monitor
reactions [6, 7].
90
nat
Sn(p,x)
80
111,114m
In
Cross section (mb) .
70
The experimental technique and the data evaluation
including the estimation of the uncertainties were similar
as described in more details in our earlier reports [7, 8].
60
This work In-111
ALICE-IPPE In-111 direct
ALICE-IPPE In-111 cum
This work In-114m
ALICE-IPPE In-114
50
40
30
20
10
0
0
20
40
60
80
100
Particle energy (MeV)
FIGURE 1. Excitation function of the
nuclear reactions.
THEORETICAL CALCULATIONS
The experimental cross sections measured in this
work and found in the literature were compared with a
priori theoretical calculation. The used ALICE-IPPE
model code [9] is an upgraded version of ALICE-91
code [10], in which the geometry-dependent hybrid
model is used to describe the pre-equilibrium particle
emission and the statistical model for equilibrium decay.
nat
Sn(p,x)111,114mIn
nat
Cd target
In Figs. 2 and 3 our new experimental results are
compared with earlier experimental results and with the
theoretical calculations. Our data are in good agreement
with the reported values of Nortier et al. [3] and
contradict the results of Zaitseva et al. [5].
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Production of 114mIn
400
nat
Cd(p,x)
111
In
The integral yields of the natSn(p,x)114mIn and of the
Cd(p,x)114mIn nuclear reactions are shown in Fig. 4.
nat
Nortier
Zaitseva
This work
ALICE-IPPE
200
1.E+02
1.E+01
Physical yield (GBq/C) .
Cross section (mb) .
300
100
0
0
10
20
30
40
50
60
Proton energy (MeV)
FIGURE 2. Excitation function of the
reaction.
nat
70
80
90
100
Cd(p,x) 111In nuclear
1.E+00
1.E-01
1.E-02
nat
111
Cd(p,x) In
nat
111
nat
111
nat
114m
nat
114m
In(p,x)
1.E-03
In
Sn(p,x) In
Cd(p,x)
Sn(p,x)
1.E-04
In
In
1.E-05
0
200
nat
Cd(p,x)
114m
40
60
80
100
Particle energy (MeV)
In
FIGURE 4. Integral yields for production of 111In and
on Cd, In and Sn targets by proton bombardment.
150
Cross section (mb) .
20
Nortier
Zaitseva
This work
ALICE-IPPE In-114
100
114m
In
CONCLUSIONS
The prediction capability of the used theoretical code
is acceptably good and very useful to estimate and
understand the magnitude of the different contributing
processes.
50
0
0
20
40
60
Proton energy (MeV)
FIGURE 3. Excitation function of the
reaction.
nat
80
Cd(p,x)
114m
100
The comparison of the excitation functions for
production of 111In on different targets shows:
In nuclear
• The cross section of natSn(p,x)111In reaction up to
60 MeV is small, around 80-100 MeV the cumulative
cross section is about 80 mb. By irradiating Sn
targets two options are open for production of 111In
by separation of In reaction products from the target
material. In the first route the separated In is used
after a proper cooling time. In the second, generator
route, pure 111In can be obtained from the separated
fraction through the decay of the produced 111Sn. The
cross section for the production of 111Sn is around
40 mb, according to the theory. A disadvantage of the
first process is that the final product contains
significant amounts of 114mIn. In the second case if we
do not consider the absolute values of the cross
sections, the short half-life of the 111Sn limits the
production yield (see later by In target). Both
processes can be optimized on the basis of the
excitation functions.
Integral Yields
The integral yields as function of the incident
energies for elemental targets were calculated from the
measured excitation functions. The calculated integral
yields for the different targets are compared on Fig. 4.
Production of 111In
The integral yields of the natSn(p,x)111In,
In(p,x)111Sn and natCd(p,x)111In nuclear reactions are
shown in Fig. 4. For the calculation of the integral
yields, our new data and results of Nortier et al. [3] were
used. For comparison in the case of an In target only the
indirect production rate from the parent 111Sn was
calculated as upper limit, supposing short irradiations
and immediate separation.
nat
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• The cross section of the natIn(p,x)111Sn-111In process
is high in the 20-50 MeV energy range (200-300 mb).
An advantage compared to the other two routes is
that no 114mIn is present in the final product. The main
disadvantage is the small batch yield due to the short
half life of the parent 111Sn (short irradiation time,
losses during the separation).
• The natCd(p,x)111In process has significant production
rates in 10-60 MeV, but the yield of 114mIn is also
high. A minimal contribution can be found with
optimization of the incident energy and the target
thickness.
• For production of 114mIn in carrier free form, only the
Sn and Cd targets should be considered:
• The natCd(p,x)114mIn reaction has high cross sections
at energies up to 40 MeV. The 111In occurs as a
significant contaminant, but it can be reduced to the
required level by a proper cooling time.
• The production of the high spin 114mIn by the
nat
Sn(p,x)114In reactions is more favorable at high
energies. The thicker target probably can compensate
the lower cross sections (compared to natCd).
paper (F. Ditrói) is a grantee of the Bolyai János
Scholarship of the Hungarian Academy of Sciences.
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1. Hermanne A., Gul K., Mustafa M. G., Nortier M.,
Oblozinsky P., Qaim S. M., Scholten B., Shubin Yu. N.,
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emitters (5.1), Charged particle cross-section database for
medical radioisotope production: diagnostic radioisotopes
and monitor reactions, Vienna, IAEA, IAEA-TECDOC1211 (http://www.nds.or.at/medical).
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According to the comparison of the production routes
on the investigated natural targets the required high
purity 111In can be obtained only through the decay of
separated 111Sn. For therapy a mixture of 111In and 114mIn
radioisotopes can be produced effectively by proton
induced nuclear reactions on natural cadmium and tin
targets, in which the amount of 111In can be reduced with
proper cooling time.
ACKNOWLEDGMENTS
This work was done in the frame of HAS-FWO
Vlanderen (Hungary-Belgium) and the HAS-JSPS
(Hungary-Japan) research projects. The authors
acknowledge the support of the research project and of
the respective institutions in providing the beam time
and experimental facilities. One of the authors of this
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