714
M. Dohlus et al.
doctors. The leading companies report that 35% of the SPECT scanners produced
are sold combined with Computed Tomography (CT). In the same way the request of
PET/CT and PET/MRI systems that combine metabolic and morphological imaging
is stably increasing and so is the demand of positron emitter radionuclides. In the
years to come many factors will contribute to define the role of accelerators in the
commercial production of medical isotopes. Unforeseen events as the shortage of
Molibdenum-99 described at the end of this section can weaken a situation that was
considered stable. The primary role of reactors, to which it is ascribed approximately
80% of the medical radioisotope production, can be diminished by downsides as
the rigidity of a centralized production, the risk of incident in nuclear power plant,
and the problems connected to radioactive waste. These drawbacks are strongly
reduced with radioisotope production based on accelerators and this can play in
their favor.
Today PET imaging is certainly the largest medical use of the cyclotron
radioisotopes. IAEA reports in its 2006 survey that 75% of the cyclotrons are
dedicated to FDG [53]. Concerning SPECT, some radioisotopes for (gamma- and
gamma/beta-emitters) are produced only with cyclotrons (Iodine-123, Indium-111,
Gallium-67, Cobalt-57) some others, as Copper-67 and Rhenium-186, are produced
both with cyclotrons or reactors.
Immuno-positron emission tomography is an imaging technique that, using
radio-labeled monoclonal antibodies, allows tracking and quantifying their distribution in the body, and can be applied to imaging of human malignancies.
Zirconium-89 has a primary role in immunoPET being used in most of the diagnoses
based on radioactive antibodies [59]. Its favorable characteristics are a half-life of
3.3 days which allows a manageable production and distribution, and the favorable
decay mode where the unavoidable gamma rays have energies well distinguishable
from PET photons. Finally Zirconium-89 production, via proton-neutron reaction in
Yttrium-89, is optimal at energies of 14 MeV, widely available in cyclotron facilities
[see Table 11.3].
Radiopharmaceuticals for therapy represent only 5% of the total production [60],
nevertheless the research in the field of cancer targeted radionuclide treatments is
active and the role of cyclotrons is becoming more and more important. The isotopes
that better conform to the therapy are those that decay transferring locally all their
energy. The favorable decay products are alpha particles, beta particles and Auger
electrons. The optimal radionuclide is selected based on essential characteristics,
which are (i) the possibility to associate it to molecules or, in case of radioimmunotherapy, to monoclonal antibody, with affinity to tumour cells, (ii) the right
decay time to allow the kinetics and avoid overdose, (iii) the availability of the
product in reliable quantities, and (iv) the affordable cost. The research is trying to
balance these demanding needs and the number of radionuclides under examination
is getting large.
Alpha-particles emitters are Astatine-211, produced with the reaction
209 Bi( 4 2 He,2n) by 28 MeV alpha particle beams, and Bismuth-212, obtained from a
M. Dohlus et al.
doctors. The leading companies report that 35% of the SPECT scanners produced
are sold combined with Computed Tomography (CT). In the same way the request of
PET/CT and PET/MRI systems that combine metabolic and morphological imaging
is stably increasing and so is the demand of positron emitter radionuclides. In the
years to come many factors will contribute to define the role of accelerators in the
commercial production of medical isotopes. Unforeseen events as the shortage of
Molibdenum-99 described at the end of this section can weaken a situation that was
considered stable. The primary role of reactors, to which it is ascribed approximately
80% of the medical radioisotope production, can be diminished by downsides as
the rigidity of a centralized production, the risk of incident in nuclear power plant,
and the problems connected to radioactive waste. These drawbacks are strongly
reduced with radioisotope production based on accelerators and this can play in
their favor.
Today PET imaging is certainly the largest medical use of the cyclotron
radioisotopes. IAEA reports in its 2006 survey that 75% of the cyclotrons are
dedicated to FDG [53]. Concerning SPECT, some radioisotopes for (gamma- and
gamma/beta-emitters) are produced only with cyclotrons (Iodine-123, Indium-111,
Gallium-67, Cobalt-57) some others, as Copper-67 and Rhenium-186, are produced
both with cyclotrons or reactors.
Immuno-positron emission tomography is an imaging technique that, using
radio-labeled monoclonal antibodies, allows tracking and quantifying their distribution in the body, and can be applied to imaging of human malignancies.
Zirconium-89 has a primary role in immunoPET being used in most of the diagnoses
based on radioactive antibodies [59]. Its favorable characteristics are a half-life of
3.3 days which allows a manageable production and distribution, and the favorable
decay mode where the unavoidable gamma rays have energies well distinguishable
from PET photons. Finally Zirconium-89 production, via proton-neutron reaction in
Yttrium-89, is optimal at energies of 14 MeV, widely available in cyclotron facilities
[see Table 11.3].
Radiopharmaceuticals for therapy represent only 5% of the total production [60],
nevertheless the research in the field of cancer targeted radionuclide treatments is
active and the role of cyclotrons is becoming more and more important. The isotopes
that better conform to the therapy are those that decay transferring locally all their
energy. The favorable decay products are alpha particles, beta particles and Auger
electrons. The optimal radionuclide is selected based on essential characteristics,
which are (i) the possibility to associate it to molecules or, in case of radioimmunotherapy, to monoclonal antibody, with affinity to tumour cells, (ii) the right
decay time to allow the kinetics and avoid overdose, (iii) the availability of the
product in reliable quantities, and (iv) the affordable cost. The research is trying to
balance these demanding needs and the number of radionuclides under examination
is getting large.
Alpha-particles emitters are Astatine-211, produced with the reaction
209 Bi( 4 2 He,2n) by 28 MeV alpha particle beams, and Bismuth-212, obtained from a