Θωμάς Μαρής, Καθηγητής, Ιατρική Σχολή, Πανεπιστήμιο Κρήτης, Επιβλέπων
Ιωάννης Δαμηλάκης, Καθηγητής, Ιατρική Σχολή, Πανεπιστήμιο Κρήτης
Μιχάλης Μαζωνάκης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, Πανεπιστήμιο Κρήτης
Magnetic resonance imaging (MRI) is a method based on the phenomenon of nuclear magnetic resonance (NMR) and its optimization is achieved by combining settings of many parameters. Especially in quantitative MRI, where magnetic relaxation times (T1, T2) and other physical properties are measured, the parameters of the imaging system play a very important role in the results of the measurements. Thus, it is considered necessary to use phantoms in order to calibrate the unit system and evaluate the measurement methods.
These phantoms should simulate the relaxation times, but also the physical properties of the biological tissues. In addition, they must be physically and chemically stable over time and easy to manufacture. These phantoms are made of radiation-sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose, with the ability to uniquely record the radiation dose distribution in three dimensions (3D).
Dosimetry has been a main factor for the development of radiotherapy techniques and there are already various dosimetric systems and methods for estimating the dose administered to tissues and other means. Polymer gel dosimeters offer a wide range of potential applications in the three-dimensional verification of complex dose distribution such as in intensity modulated radiotherapy (IMRT). Today, complex algorithms are used to determine the dose distributions required in a treatment plan, and of course the rapid development of technology enables the development of modern radiotherapy techniques.
In the context of this work, two different polymer gel dosimeters (VIPET and VIPASCU) were compared, in terms of their basic properties in MRI. These dosimeters were studied, at various concentrations, to investigate the effect, of the changes in the concentration of specific monomers, on the magnetic recovery times T1 and T2.
The main goal was to manufacture a new polymerization gel dosimeter which is less toxic, economical but at the same time easy to make and efficient with high dose sensitivity. It was also important to optimize the quality of the results from the radiotherapy experiments performed, with the parallel support of magnetic resonance imaging techniques.
Finally, we additionally compared the two methods which was used to measure magnetic relaxation times, as the first, Multi Spin Echo, is widely used in clinical practice, while HASTE is not.
Polymer gel dosimetry, MRI, Gel, T2 magnetic restoration time, Radiotherapy, Non-toxic