hrvatski

Doze zračenja od oslikavanja u radioterapiji

Investigation of the imaging doses in external beam 3D conformal image guided radiotherapy (IGRT) ; from CT simulation to patient positioning verification during treatment by means of linac integrated kV cone beam CT (CBCT) and/or electronic portal imaging (EPID) device is presented in this work. An extensive set of dose measurements in standard PMMA CT head (16 cm) and body (32 cm diameter) phantoms were done for most frequently used clinical protocols of CT simulator unit Toshiba Aquilion LB and Elekta XVI system CBCT. Measurements with two different dosimetry systems ; CT Dose Profiler (CTDP) solid state probe with Barracuda meter (RTI Electronics AB) dedicated to helical CT dosimetry and PTW Farmer type ionization chamber of 0.6 cm3 volume calibrated in RTQ9 beam quality, were compared. Suitability of Farmer chamber, usually employed for dose measurements in radiotherapy beams, was confirmed by good agreement with CTDP probe, in head and body phantom center and free in air at Toshiba CT unit. More detailed measurements that included positioning detectors at the center and peripheral holes of the phantoms were conducted for H&N S10 (100 kV) and Pelvis M20 (120 kV) XVI protocols with both detectors, and weighted point dose index DIw analogue to CTDI definition was calculated. Dose to water measured in phantom DIw were 2, 13 cGy for Pelvis and 0, 11 cGy for H&N protocol. Similar measurements for 15 cm scan length of Toshiba Head and Body protocols yielded 6, 12 cGy and 4, 83 cGy, respectively. Furthermore, absorbed doses in the center of the CT phantom were calculated with radiotherapy treatment planning system for EPID imaging with 2MU of 6MV photon beam at isocenter and they were 1, 5 cGy for body and 1, 9 cGy for head phantom.

oslikavanje, CBCT, radioterapija, doze zračenja

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