Akademska digitalna zbirka SLovenije - logo
VSE knjižnice (vzajemna bibliografsko-kataložna baza podatkov COBIB.SI)
  • Experimental determination of field output factors and detector specific output correction factors in small fields of megavoltage radiotherapy beams [Elektronski vir]
    Casar, Božidar
    The goal of this work was to determine field output factors, ▫$\Omega^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫, using EBT3 radiochromic films and W1 plastic scintillator as reference detectors on two ... different linear accelerators. Secondly, we aimed to provide a large and consistent set of data for detector specific output correction factors, ▫$k^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫, for small static fields for seven solid state detectors and seven small ionization chambers. In the case of ionization chambers, ▫$k^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ were determined in two orientations - parallel and perpendicular, to test the hypothesis, that ▫$k^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ are lower and therefore advantageous for parallel orientation. ▫$\Omega^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ were determined for 6 and 10 MV photon beams with and without flattening filter and for nine fields ranging from 0.5 x 0.5 ▫$cm^2$▫ to 10 x 10 ▫$cm^2$▫. Signal readings obtained with EBT3 radiochromic films and W1 plastic scintillator were fitted by an analytical function. ▫$k^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ were determined empirically for 14 clinically used small detectors, under the same experimental conditions. It has been found that, for a given linear accelerator, ▫$\Omega^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ need to be determined for every combination of photon beam energy, filtration, and field size as the differences between them can be statistically significant (p < 0.05). Further, it has been demonstrated, that the parallel orientation of ionization chamber is advantageous over the perpendicular, which is an important contribution to the present international dosimetry protocol for small fields IAEA TRS-483. Use of two reference detectors for the determination of field output factors for small static fields in MV photon beams is a novel approach and has been justified in our thesis. Large set of ▫$k^{f_{clin},f_{ref}}_{Q_{clin},Q_{ref}}$▫ data for seven solid-state detectors and seven ionization chambers in four MV beams determined on two linear accelerators by a single group of researchers can be considered a valuable supplement to the literature and the IAEA TRS-483 dataset. Recommendation on the orientation of ionization chambers is the last significant outcome of our work.
    Vrsta gradiva - disertacija ; neleposlovje za odrasle
    Založništvo in izdelava - [Zagreb : B. Casar], 2019
    Jezik - angleški
    COBISS.SI-ID - 3265659