Design of a phantom for the quality control of high dose rate 192Ir source used in brachytherapy.
OBJECTIVE
A new phantom is proposed for measuring the strength of 192Ir high dose rate sources and for verification of the dose calculated by the treatment planning system. The complete formalism and measurement procedure for this phantom is described, as well as the preliminary results obtained in a number of centers around Brazil.


METHODS
The measurements are performed using powder thermoluminescent dosimeter capsules; the source strength is measured in air and the verification of the dose calculation algorithm in water phantom. The correction factors required to take into account the specificities related to the geometry and the phantom materials have been assessed using the PENELOPE Monte Carlo code and experimental methods. The dedicated phantom, constructed to use as part of a QA program, in this case specifically for high dose rate 192Ir brachytherapy sources, allows simultaneous irradiation of three thermoluminescent dosimeter capsules, requiring only one source stop (dwell positions).


RESULTS
The phantom was mailed to seven radiotherapy institutions in Brazil, and the results show its usefulness in verifying the source air kerma and correctness of treatment planning dose calculation in water phantom.


CONCLUSIONS
The comparison made between the phantom measurements, the well-type ionization chamber, and source specifications stated by the hospital (most of the times provided by the source manufacturer) agreed within 3% showing the quality in the HDR dose delivery in Brazilian radiotherapy centers.
Ochoa
Ricardo
R
Laboratório de Ciências Radiológicas (LCR) Universidade do Estado de Rio de Janeiro, Rio de Janeiro, Brazil.
Gómez
Fredy
F
Ferreira
Ivaldo H
IH
Gutt
Federico
F
de Almeida
Carlos E
CE
D000465:Algorithms; D001918:Brachytherapy / Q000592:standards*; D002138:Calibration; D006801:Humans; D007496:Iridium Radioisotopes / Q000592:standards*; D019047:Phantoms, Imaging; D011786:Quality Control; D011879:Radiotherapy Dosage / Q000592:standards*
D007496:Iridium Radioisotopes