ABSTRACT
The paper is aimed at the determination of the efficiency of various technologies of conformal radiotherapy for patients with nasopharyngeal carcinoma. The study included 56 patients with squamous cell carcinoma of the nasopharynx treated with conformal radiotherapy. 3D-CRT was performed for 28 patients, IMRT--22 patients, RapidArc--6 patients. Dosimetric parameters were determined for planned volumes and organs at risk. TD on high-risk areas was 70Gy, intermediate-risk zones 60-66Gy and low-risk areas 50-56 Gy. There were determined session duration of exposure and the number of monitor units to evaluate the efficiency of treatment. Average (Dmean), maximum (Dmax) and the minimum (Dmin) dose for RapidArc, IMRT and 3D-CRT on PTV amounted to 70.2 Gy, 69.1 Gy and 70.7 Gy; 76.2 Gy, 76.1 Gy and 77Gr; 48.8, 54.4 and 46,6Gr respectively. Compared with IMRT and 3R-CRT RapidArc reduce Dmean in the brainstem and optic nerves by 14.1% and 23%; 12.2% and 25% respectively. The average number of MU (monitor unit) with RapidArc, IMRT and 3D-CRT was 357, 1386 and 870. The average session time of irradiation was: with RapidArc, IMRT and 3D-CRT--300, 900 and 480 seconds. Compared with IMRT and 3D-CRT average treatment time and the number of monitor units in RapidArc were reduced by 74%, 42% and 67%, 47%. Thus RapidArc and IMRT technologies allow getting a better dose distribution in the irradiated volume, compared with 3 D-CRT on homogeneity and conformity. RapidArc technique reduces the pressure on the critical organs, diminishes exposure to the session and a number of MU.
