The fi rst part of this study was about measurement of dosimetric parameters for small photon beams to be used as input
data for treatment planning computer system (TPS) and to verify the dose calculated by TPS in Stereotactic Radiosurgery
(SRS) procedure. The beam data required were percentage depth dose (PDD), off-axis ratio (OAR) and scattering factor.
Small beams of 5 mm to 45 mm diameter from a circular cone collimator in SRS were used for beam data measurements.
Measurements were made using pinpoint ionisation chamber (0.016cc). In the second part of this study, we reported
the important of carrying out quality assurance (QA) procedures before SRS treatment which were found to infl uence the
accuracy of dose delivery. These QA procedures consisted of measurements on the accuracy in target localization and
treatment room laser alignment. The calculated TPS dose for treatment was verifi ed using pinpoint ionisation chamber
and thermoluminescent detector (TLD) 100H. The deviation mean between measured and calculated dose was -3.28%.
The measured dose obtained from pinpoint ionisation chamber is in good agreement with the calculated dose from TPS
with deviation mean of 2.17%. In conclusion, pinpoint ionisation chamber gives a better accuracy in dose calculation
compared to TLD 100H. The results are acceptable as recommended by International Commission on Radiation Units
and Measurements (ICRU) Report No. 50 (1994) that dose delivered to the target volume must be within ± 5% error.
Conventional two-dimensional (2D) treatment planning of intracavitary brachytherapy is still a common practice at the radiotherapy center. The purpose of this study was to evaluate the organ at risk (OAR) doses estimated based on International Commission on Radiation Units and Measurements (ICRU) reference-point in patients with cervical cancer treated with high-dose-rate (HDR) intracavitary brachytherapy (ICBT). Between January 2010 and April 2014, 21 cervical cancer patients were treated with 42 fractions of brachytherapy using tandem and ovoids and underwent post-implant two-dimensional (2D) radiograph scans. HDR brachytherapy was delivered to a dose of 18 Gy in two fractions. Using the Oncentra brachytherapy treatment planning system (BTPS) software version 4.1 (Nucletron, Netherlands), the bladder and rectum points were retrospectively reconstructed based on 42 orthogonal radiographs datasets. The ICRU bladder and rectum point doses were recorded. As for results, the mean percentage dose of rectum and bladder for selected patients treated with intracavitary brachytherapy treatment (ICBT) were 47.27 and 75.59%, respectively. Combinations of ovoid’s size, length of tandem and anatomy variation between each patient were factors that affected the dose to the OAR. Therefore, the ICRU reference points can still be used with the 2D brachytherapy treatment planning in evaluating the OAR doses.