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Importace of verification treatment irradiaton position of IMRT prostate
KŘÍŽOVÁ, Marcela
Prostate cancer is the most frequent oncological disease in men. Based on the disease phase and extent, patiens with prostate carcinoma diagnosis are treated with number of different therapies including radical prostatectomy, hormone therapy, chemotherapy, brachytherapy, conventional radiotherapy, conformal radiotherapy and combination of these. This Bachelor Thesis deals with prostate carcinoma treatment using a special conformal radiotherapy method - IMRT (Intensity Modulated Radiotherapy). The first section describes the disease charakter from the clinical point of view and the disease diagnosis, followed by treatment modalities. The main part examines and describes IMRT, treatment planning and resultes from statistic evaluation of irradiation position deviations. IMRT technique allows escalation of the irradiation dose while protecting critical structures. In this way the patient can be irradiated with a total dose of 80 grays (Gy). Patients are irradiated in a linear accelerator. Modulation of the radiation beam using multileaf collimator allows irradiation of different segments of target volume with different doses, so that overal homogenity of the irradiation treatment is achieved through nonhomogenous distribution of the dose. Escalation of the irradiation dose is in a close relationship with the irradiaion position and isocentre position kontrol, so that the treatment quality is guaranteed preventing damane to surrounding healthy tissue. Fixing the patient in irradiation position as well as reproductibility of the position is of essentials importance. The isocentre in irradiation position is verified efore every fraction. Verification portal images are acquired using EPID (Electonic Portal Image Device) Portal Vision LC 250 and then compared with reference verification images acquired by CT when planning the treatment. Portal images are made up of two fields of 12x12 cm size under 0 and 90 or 270 degrees. Deviations are recorded in craniocaudal, mediolateral and anterior-posterior axes, and if they exceed 3mm, the irradiation position is corrected on the irradiation table. In this Thesis, deviations in a group of 30 patients were evaluated using the Aria-Offline Review programme which is an accesory to the treatment planning system. In one third of the statistical group of patient, deviations identified using on offline review were compared with deviations identified by start efore each fraction. Dutiny statistical processing, deviations were recorded within ranges 0-3 mm, 3,1-5 mm and over 5mm. 69% of acceptable deviations were recorded within the 0-3 mm range in the craniocaudal axis, 71% in the mediolateral axis and 67% in the anterior-posterior axis. Based on a complete analysis and evaluation of the deviations we can conclude that verification of the irradiation position in treatment of prostate carcinoma using IMRT is essentials to guarantee the irradiation treatment quality. We have also verified that deviations between 0 and 3 mm are acceptable and in no way impair the treatment quality.
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