The glow curve in TLD-100 was compared by applying long preheat time, short preheat time
techniques and without preheat technique before the TLD readout. Fading effect of the TLD signal
upon certain storage time with long preheat time (100°C, 10 minutes using the oven) and short
preheat time techniques (100°C, 10 seconds using the reader) were also studied. 15 TLD-100 chips
were used with 3 of the TLD chips were used for measuring background radiation. 12 TLD chips
were annealed, irradiated, preheated long and short preheat time techniques) and analyzed. The TL
signals output from TLD chips of without preheated were used as the control. Two sets of data were
taken using TLD chips irradiated with 6 MV and 10 MV photon beams. TL signal output was
recorded the highest for short preheat time, followed by long preheat time and no preheating. The
TL signal loss upon certain storage time was also reduced when short preheat time technique was
applied. By applying long preheat time technique the low temperature peak in the glow curve was
completely removed for both energies. Whereas, TLD chips exposed to 6 MV and with short preheat
time technique the low temperature peak did not disappear completely but decreased in intensity as
compared to the control data by 19.80%, 37.69%, 48.19% and 100% at 24, 48, 72 and 96 hours
after exposure prior to readout, respectively. Meanwhile, for 10 MV photon beam with short
preheat time, the small peak intensity was reduced by 19.58% for readout at 24 hours after
irradiation and 100% for 48,72 and 96 hours delayed time prior to readout. It was observed that
the TLD-100 was highly dependent on preheat heating time before readout. Short preheat time
technique was able to reduce post irradiation fading of TLD-100 dosimeters
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.
This study evaluates the ImageJ software as dosimetric tools for analyzing the film dosimeter in high energy photons and electrons. The percentage depth dose of photons of 6 and 10 MV and electrons of 6 and 9 MeV were measured using the Gafchromic EBT2 film dosimeter. The films were scanned and analyzed using the Verisoft software and ImageJ. The beam profiles at nominal photon and electron beam parameters were also evaluated using the two methods. The PDD measured in ImageJ at high energy photons were in good agreement within 1% percentage of discrepancy at all depths in comparison to the Verisoft software. The PDD measured in ImageJ at high energy electrons also showed good agreement to Verisoft software within 8% percentage of discrepancy at all depths. The measured flatness of beam profiles at Dmax, R50, R80 and R90 in ImageJ were also in good agreement to Verisoft software with flatness value between 4 and 8%. The results indicated the suitability of ImageJ software as dosimetric tool for analyzing EBT2 film dosimeter at high energy photon and electrons.
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.