| Abstrakt: | Radioisotopes play an important role in nuclear medicine, both in medical diagnostics
and in the development of isotope - targeted therapy. At present, there is a crisis in world
radioisotope production mainly because of the exploitation of nuclear research reactors which
global production of radioisotopes is based on. The answer to this situation is the search for
alternative ways of making radionuclides for nuclear medicine. Within this work the
possibilities of the use of the medical linear accelerators for the aforementioned purposes was
checked. The high-energy photons generated in such medical linac cause photonuclear
reactions (γ,n) and (γ,2n) which except of radioactve isotopes, neutrons are also produced in.
These neutrons with the broad energy spectrum are the contamination of the therapeutic
beam. The secondary neutron radiation can also be a source of nuclear reactions leading to the
production of radioisotopes.
The main aim of the thesis was to test a possibility of production of medical isotopes
such as: 99Mo/99mTc, 198Au, 186Re and 188Re. The targets made of the natural elements were
irradiated with the use of high-energy therapeutic 20 MV X-ray beam generated by the
Varian medical linacs (Clinac 2300 and TrueBeam). The irradiations were performed at the
Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology in Gliwice. The
produced activity was determined on the base of the gamma energy spectra measured during
decay of specific radioisotopes. The spectral measurements were carried out by means of the
germanium detector. The research is completely innovative, there are no scientific reports
with similar experiments.
In this thesis the research associated with therapeutic dose enhancement was also
described. The dose enhancement is obtained when the high atomic number metal
nanoparticles are introduced to a target volume. This dose enhancement is caused by the
increase of the photoelectric effect due to irradiation with the therapeutic megavoltage
X-rays. The additional increase of a dose can be reached by means of the nanoparticles with
radioactive gold atoms. Simulations were carried out using GEANT4 in version 4.9.2
installed on the Linux platform.
The first part of the thesis is based on literature and available scientific publications. In
the introduction the most important problems that make it possible to understand the research
presented in this work were discussed. The literature section presents possible applications of
radionuclides. I tested methods of their production, and briefly discribed their basic physical
properties. What is more, this section describes important issues related to knowledge of
current methods of production of radioisotopes and techniques of nanoparticle synthesis
including gold nanoparticles.
The methodology of measurements and calculations is described in the second part of
the thesis. This section presents an innovative radionuclide production technique using
medical linear accelerators available in each oncology center. Moreover, this chapter
summarizes qualitative data analysis methods in a brief manner, including computational
methods. The experimental part presents the spectra of gamma radiation emitted by
radioactive isotopes recorded by means of semiconductor detectors, decay schemes of
radionuclide, and cross sections for typical reactions occurring in target materials during the
emission of high energy therapeutic beams. The rest of this chapter includes the results of
experiments based on well known production methods. A discussion of the results of
experiments taken from the specialist literature has the advantage that in the following part of
this thesis facilitates the interpretation of the obtained results. It allows to estimate the
effectiveness of the proposed method of production of radioactive isotopes used in nuclear
medicine.
The six chapter presents the structure of simulation programs based on the Monte Carlo
techniques. A separate chapter (the chapter seven) presents the results of experiments and
calculations. The obtained results were compared with literature data and summarized in the
chapter eight. |