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Comparison of doses in the target volume and critical organs for Intensity Modulated Radiation Therapy (IMRT) and proton therapy
STIEBLINGOVÁ, Tereza
The topic of this thesis is a view at the two selected modern irradiation techniques - IMRT (Intensity-Modulated Radiation Therapy) and proton therapy. I compared them at a general level in the theoretical part, and in the practical part I focused on the absorbed doses in selected critical organs in patients with prostate cancer. In the theoretical part I worked with specialized literature and articles from medical journals and also with a number of internet sources. For example I worked with a publication titled Radiační onkologie by Pavel Šlampa or Klinická onkológia a rádioterapia by Ľudovit Jurga. I made a concept based on the obtained information, which is composed of generally related topics, e.g. the position of radiotherapy in the treatment of oncological diseases, characteristics of ionizing radiation, the process of radiation treatment planning etc. After these introductory chapters I focused specifically on photon IMRT technique and proton therapy which are among the most modern methods of contemporary radiation oncology. In the theoretical part I set the description of these selected techniques as a goal, with an emphasis on their advantages and disadvantages. In the practical part I analyzed these two techniques in terms of received minimum, medium and maximum doses in selected critical organs rectum, bladder and both femoral heads using different fractionation schemes. The results were compared with information from the theoretical part. In the practical part, the testing of this hypothesis was set as my goal: During the treatment of prostate cancer with accelerated protons the healthy surrounding tissue and critical organs will receive smaller amount of radiation dose than IMRT technique. Proton Therapy Center (PTC) in Prague provided me with some irradiation plans including CT scans from 20 anonymous patients diagnosed with prostate cancer and treated with protons. Then I worked with these plans in planning program to create a photon IMRT plan for each proton plan and in order to be able compare these two techniques in each patient in different fractionation schemes. When I compared IMRT technique and proton therapy, both in norm-fractionated scheme, moderate doses were lower with protons in all 20 patients in all selected critical organs. The average difference in moderate doses of these techniques in all selected critical organs is 11,022 Gy. Specifically, from the results is further evident, that the bladder and the rectum absorb less minimal and medium dose if proton therapy has been used in any fractional mode (short, long, norm-fractionated scheme) than in the photon IMRT therapy. These results were obtained in all 20 patients. When I compared IMRT technique and proton therapy, both in short scheme or long scheme, in terms of the maximum doses in the bladder and rectum, the values were comparable in the both critical organs. In none of the literature used as a source is a mention of minimal and medium doses on heads of both femurs. But if I compare the median doses proton's therapy with doses IMRT's photon therapy, both in norm-fractionated scheme, the medium doses were lower if proton therapy had been used. The results of minimal doses are contradictory and conclusions are not so unequivocal. The values of the maximum doses of the right and left femoral head were lower in overwhelming majority of 20 patients in proton therapy (in the short and also in long scheme). The average difference in the left head of femur is 3,434 Gy (proton's short scheme vs. photon's short scheme), respectively 6,654 Gy (proton's long scheme vs. photon's long scheme). The average difference in the right head of femur is 5,422 Gy (proton's short scheme vs. photon's short scheme), respectively 9,273 Gy (proton's long scheme vs. photon's long scheme).

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