Radiation therapy technologies and medical imaging related to image guided radiotherapy (IGRT) are rapidly developing areas of cancer treatment. Today IGRT is available in most radiotherapy centres all around the world – including 14 centres in Hungary - since most cases of malignant tumours are treated with the help of this technology. The new generation of linear accelerators (LINAC) are equipped with electronic portal imaging devices (EPID) and kilovoltage (kV) cone-beam CT (CBCT). These image modalities can be applied for the patients before all treatment fractions. Imaging involves additional dose for the patient, but image guided radiotherapy (IGRT) increases the accuracy of the set-up and therefore the effectiveness of the treatment. Image quality is essential for the treatment verification and precise correction of the patient set-up. For brachytherapy treatment, a new mobile CBCT will be available in Hungary this year. With this equipment, the real position of the applicators and radiation sources can be verified, and a new field of therapy - image guided brachytherapy (IGBT) can be investigated. The goal of this PhD topic is to develop different methods of dosimetric analyzes and determine the additional dose related to the different image modalities, furthermore, to analyse the different image quality parameters for the different medical imaging equipment and to compare the dosimetric and image quality parameters of conventional spiral CTs and CBCTs. Candidate will be involved in the IAEA Coordinate Research Projects for Advanced Tools for Quality and Dosimetry of Digital Imaging in Radiology (E24025) (https://www.iaea.org/newscenter/news/new-crp-advanced-tools-for-quality-and-dosimetry-of-digital-imaging-in-radiology-e24025), through the National Institute of Oncology, especially for the investigation of the image quality of CBCTs.