Abstract:
Radiation dose to bladder and rectum in the treatment of cervical cancer using
high dose rate brachytherapy is a limiting factor to the delivery of the
prescribed dose to the target. The objective of this study is to determine
absorbed dose to the bladder and rectum (organs at risk) in the treatment of
cervical cancer using multisource high dose rate brachytherapy treatment
system in order to establish an in-vivo dosimetric and quality assurance
protocol for patient treatment. A phantom was constructed using perspex for
the measurement of dose distribution to the bladder and rectum. Gafchromic
EBT3 films were used as dosimeters for measuring doses received by the
bladder and rectum. The variation between doses calculated by the treatment
planning system (TPS) and the doses measured by the Gafchromic EBT3 film
at the bladder point was 15.38% (mean) ranging from -29.03% to 43.75%. The
variation between doses calculated by the TPS and the doses measured by the
film at rectum point was 14.73% ranging from -47.22% to 51.06%. Two
mathematical algorithms were developed from the study to enable dose
estimation to the bladder and rectum for error detection, variation analysis and
verification of the treatment system. The variation between doses calculated
by the TPS and the doses calculated by the model at the bladder point was
9.53% ±8.04. The variation between doses calculated by the TPS and the doses
calculated by the model at the rectal point was 13.57% ±8.46. The results of
the proposed models are within the ± 15% uncertainty proposed for dose
delivery in radiation therapy (Hanson et al., 1994). The model is therefore
recommended for clinical applications
