VSE knjižnice (vzajemna bibliografsko-kataložna baza podatkov COBIB.SI)
  • Dose calibration of nonconventional treatment systems applied to helical tomotherapy
    Jeraj, Robert ...
    Current dosimetric protocols based on the absorbed dose (AAPM TG-51 and IAEA TRS-398 protocols) require calibration measurements under reference conditions. For some radiotherapy systems, this ... requirement cannot be met, andcalibration has to be performed under nonreference experimental conditions.In order to solve this problem, both protocols can be extended by inclusion of the measured-to-reference conversion factor, kmr. In order to determine this factor, basic dosimetric quantities, like stopping power ratios, mass attenuation coefficients and chamber correction factors have to be calculated. If measurements are not feasible, accurate Monte Carlo modelingis required. The extension of the protocols is illustrated using the case of the helical tomotherapy radiation unit, where the typical calibration measurement conditions are the 10ì5 cm2 field size and the 85 cm surface source distance, limited by the system design. It was calculated that the kmr factor for this conditions is close to unity (0.997Ş0.001). In addition, the deviation of the measurement conditions from the reference conditions results in the change of the quality conversion factor (approximately 0.995É0.998, depending on the ionization chamber used). This change is the same regardless of the used calibration protocol. For smaller field sizes the corrections become more significant, resulting in the total correction factor compared to the reference conditions of up to 1.5% for the smallest considered field size of 2ì2 cm2.
    Vir: Medical physics. - ISSN 0094-2405 (Vol. 32, 2005, str. 570-577)
    Vrsta gradiva - članek, sestavni del
    Leto - 2005
    Jezik - angleški
    COBISS.SI-ID - 19686695

vir: Medical physics. - ISSN 0094-2405 (Vol. 32, 2005, str. 570-577)
loading ...
loading ...
loading ...

Vnos na polico