Dissertation committee:
Ευστάθιος Ευσταθόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Βασίλειος Κουλουλίας, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Παντελης Καραΐσκος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Παναγιώτης Μπαμίδης , Καθηγητής, Ιατρική Σχολή, ΑΠΘ
Μιχαήλ Μαζωνάκης, Αν. Καθηγητής, Ιατρική Σχολή, Πανεπιστήμιο Κρήτης
Ευάγγελος Παντελης, Αν. Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Καλλιόπη Πλατώνη, Επ. Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Over the last decades, Nanoparticles (NPs) have invaded in modern radiotherapy research since they are proposed as ideal radiosensitizers. Owing to a huge variety of advantageous properties and especially due to their high biocompatibility, gold nanoparticles (AuNPs) have attracted scientific interest since they could be utilized as dose enhancement agents in modern radiotherapy techniques. The aim of this thesis was the quantification of dose enhancement that could be achieved in AuNPs loaded tumors external radiotherapy through Monte Carlo calculations and the determination of the parameters that may affect dose increase.
For this purpose, a flattened and a flattening filter free 6 ΜV photon beam arising from the TrueBeam® linear accelerator was modelled in GATE platform. AuNPs of different sizes were arranged in clusters and distributed in different depths in a modelled water phantom. The clusters were irradiated under the simulated photon beams.
AuNPs size, concentration and their biodistribution were examined concerning their impact in dose enhancement. Dose increase was calculated as a function of distance from clusters and photon beam central axis, while depth in phantom and photon field size were investigated as well.
Τhe results from the research showed that dose was increased up to 27% in presence of AuNPs. The greatest dose enhancement was obtained in the first 100 nm from AuNPs clusters and was reduced with distance. Flattening filter absence led to greater dose increase, almost independently of photon field size. Distribution of AuNPs in the examined depths in water (2, 5 and 10 cm) has been proved appropriate for dose amplification. AuNPs concentration did not have a straightforward impact in dose enhancement since (self) absorption phenomenon from the clusters in water may restrict the number of secondary electrons that deposit their energy in water. The arrangement of closely packed AuNPs in clusters which could be distributed in close distances in tumor regions could possibly cause limitations in dose enhancement due to secondary particles absorption from each underneath cluster.
AuNPs driven radiotherapy needs a thorough research prior to any clinical implementation. AuNPs ideal concentration, biodistribution, excretion routes and toxicity effects should be accurately evaluated. Finally, the implementation of AuNPs distribution and the physics models that dominate in nanoscale should be precisely defined since they should be implemented in treatment planning systems in order to perform nanodosimetric calculations and predict accurately the dose distribution in patients that undergo radiotherapy.
Keywords:
Radiotherapy, Gold nanoparticles, Dose enhancement, Monte Carlo simulations, Nanodosimetry
