Naslov
Dosimetric verification of compensated beams using radiographic films

Autori
Jurković, Slaven ; Žauhar, Gordana ; Faj, Dario ; Smilović Radojčić, Đeni ; Švabić, Manda

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
11th International Symposium on Radiation Physics / Chris Chantler - Melbourne, 2009, 202-202

Skup
11th International Symposium on Radiation Physics

Mjesto i datum
Melbourne, Australija, 20.09.2009. - 25.09.2009

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Radiation therapy ; dosimetry ; compensators

Sažetak
Intracavitary application of brachytherapy sources followed by external beam radiation is common practice in radiotherapy of carcinoma of the cervix. Since brachytherapy sources deliver very high doses to the central portion of the target volume this part must be shielded while irradiate with photon beams. There are several shielding techniques in practice ; from standard cervix wedge and more precise, customized step wedge filters or use of multileaf collimator (MLC) for the intensity modulation of the external beam dose according to the brachytherapy distribution. After the brachytherapy we use high energy photon beams modulated with accurately calculated compensators. Since dosimetric verification needs high spatial resolution it makes radiographic film the dosimeter of choice. However, the disadvantage of the film is over- response to low energy photons. This disadvantage arises from the fact that the silver-bromide grains in the film emulsion preferentially respond to photons with energies lower than about 400 keV. Compensator shields central part of the beam and the dose beneath the compensator is delivered mostly by scattered, low energy photons. Radiographic film dosimetric verification is done at 10 cm depth where the scattered component of the dose is more pronounced. In order to check radiographic film dosimetric verification of compensated beam we made measurements with ion chambers in water phantom and used it as a gold standard. Film measurements showed overesponse that approached up to15% regarding measurements with ionization chambers. We calculated photon spectra at the measurement planes using the Monte Carlo simulation of particle transport. The magnitude of over-response was associated with the changes in the spectra of photon energy in the beam. The measurements with diode linear array and amorphous silicon electronic portal imaging device would also be discussed.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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