Temperature measurements in materials with different conductivities using mild microwave hyperthermia techniques : correlation of results with quantitative MRI techniques

• Κύριος συγγραφέας: Γιαννακάκη, Βασιλική
• Άλλοι συγγραφείς: Giannakaki, Vasiliki
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Hyperthermia; MRI hyperthermia; Υπερθερμία

Ηyperthermia is a cancer treatment method that has been used for thousands of years. Hyperthermia is defined as the delivery of a desired and controlled form of heat to a disease site while protecting the surrounding healthy tissue from irreversible damage. As a cancer treatment, hyperthermia has sparked a lot of attention. In hyperthermia treatments, tumors are selectively heated to temperatures exceeding 40◦C, while healthy tissues are maintained below critical temperatures. Hyperthermia is a non-invasive therapeutic option that has been shown to be quite effective in clinical treatment. However, the issue of temperature monitoring stifles its growth. Magnetic resonance imaging is one of the methods under investigation for noninvasive thermometry (MRI). Thermometric image parameters based upon magnetic resonance relaxation times are taken into account. Relaxation times are temperature dependent. In comparison to invasive procedures, MRI-based temperature mapping techniques are safe and have been used to detect temperature changes in a number of applications. Magnetic resonance imaging (MRI) is a versatile and powerful medical imaging technique that has been widely used in clinical practice. A major advantage of MRI over other imaging modalities, aside from its nonionizing radiation nature, is that it may produce superior and versatile soft tissue contrasts based on the intrinsic features of tissues. Three common contrast methods utilized in clinical applications are proton density–weighted contrast, T1−weighted contrast, and T2−weighted contrast. During the experimental process we created hyperthermia states in four samples using microwave diathermy antenna. With the use of an MRI system we visualized and correlated the effects of hyperthermia. The purpose of this work was twofold. The initial goal was to measure and quantify the T2 parameter as a function of temperature in mild hyperthermia, in order to control the T2 index as a way of measuring temperature changes during the hyperthermia process. The T2 parameter was measured for four different samples. The first three had electrical properties -and more specifically electrical conductivity (EC)- that resembled various tissues at 37◦C. The first solution had conductivity which was resembling fat, the second had grey matter and the third a cerebrospinal fluid. The fourth solution was a colony of human melanoma cancer cells. Secondarily, conductivities of the four solutions were measured in a temperature range of 20◦C to 45◦C after the process of heating, in order to quantify conductivity C versus temperature T as well as the conductivity dependence of different heating processes, such as microwave diathermy and heating induction.