reduan abdullah | Universiti Sains Malaysia (original) (raw)

Papers by reduan abdullah

Measurement of source strength of new high dose rate (HDR) 192 Ir supplied by the manufacturer is... more Measurement of source strength of new high dose rate (HDR) 192 Ir supplied by the manufacturer is part of quality assurance recommended by Radiation Safety Section, Ministry of Health of Malaysia. The source strength is determined in reference air kerma rate (RAKR). The purpose of this study was to evaluate RAKR measurement of 192 Ir using well-type ionisation chamber with RAKR stated in the certificate provided by the manufacturer. A retrospective study on 19 MicroSelectron HDR 192 Ir Classic from 2001 to 2009 and 12 MicroSelectron HDR 192 Ir V2 sources from 2009 to 2016 supplied by manufacturer were compared. From the study, the agreement between measured RAKR and RAKR stated in the certificate by manufacturer for all 32 sources supplied were within ±2.5%. As a conclusion, a threshold level of ±2.5% can be used as suitable indicator to spot problems of the brachytherapy system in Department of Nuclear Medicine Radiotherapy and Oncology, Hospital USM.

ABSTRACT: Particular attention may be paid to reassess for treatment planning systems (TPSs) that... more ABSTRACT: Particular attention may be paid to reassess for treatment planning systems (TPSs) that deal with specialized techniques such as stereotactic radiosurgery. It is important for clinical medical physicist to be able to quantify errors involved in the dosimetric parameter data before it can be downloaded into the TPS. The purpose of this study was to verify the measurement of relative output factor (ROF), which is one of the dosimetric parameter data required for Stereotactic Radiosurgery (SRS) treatment planning. ROF of 5 mm to 45 mm diameter Radionic circular cone collimators were measured using three types of ionization chambers, which were A12 Extradin Farmer-type Chamber (0.65 cc), A14 Extradin Microchamber (0.016 cc) and PTW Pinpoint Ionization Chamber (0.016 cc). The ROF measurements were verified using a Monte Carlo (EGSnrc) validated model and other previous studies. In conclusion, pinpoint ionization chamber gave the most reliable ROF result for field size from 5 mm to 45 mm compared to other ionization chambers used in this study. The ROF measurement using pinpoint ionization chamber was in good agreement with the Monte Carlo calculation (± 4.9% percentage deviation). Therefore for measurement of ROF for SRS circular field size, pinpoint ionization chamber was suggested due to its accuracy. This ROF validation test can be carried out during the commissioning and installation of the new TPS and also for annually quality assurance (QA).

ABSTRACT: The performance of treatment planning system (TPS) nowadays is a key component in order... more ABSTRACT: The performance of treatment planning system (TPS) nowadays is a key component in order to deliver an accurate treatment towards target volume in any radiation therapy process. Thus, the purpose of this study is to verify the point doses calculated by Oncentra Brachytherapy Treatment Planning Software 4.1 (Nucletron, Netherlands). Three different simple geometric catheter configurations were planned in TPS, and point doses of TPS calculation were compared with manual calculation and measured point doses using Gafchromic EBT2 films. For manual calculation of three simple geometric catheter configurations planned, 68% of calculated dose agreed with TPS calculation within 10%. This is because the TPS and manual calculations are based on the similar AAPM TG-43 formalism. Meanwhile, 11% of the measured point doses agreed with the TPS calculation within 10%. The films had high spatial resolution, which was highly sensitive for measuring doses in high dose gradient but it also led to overestimation of the dose. It was also inaccurate in detecting the lower dose region due to energy dependence. In conclusion, manually calculated point doses gave the most reliable point dose results compared to the measured point doses in this study. The method used in this study can be used as a procedure for evaluating the accuracy of calculated point doses prior installing and commissioning a new TPS.
Keywords: AAPM TG-43 formalism, brachytherapy treatment planning system, point doses measurements

The objective of this study is to measure the peripheral dose (PD) at different depths and field ... more The objective of this study is to measure the peripheral dose (PD) at different depths and field sizes using film dosimetry. PD of 6 MV Siemens Primus linear accelerator photon beam for 10 cm square field and 2.5 cm diameter cone were measured at 1.5 cm and 10 cm depth, 100 cm source surface distance (SSD) with Kodak EDR2 film. PD for 10 cm square field and 2.5 cm cone were measured for the distance 1 cm to 5 cm from the geometric field edge. PD was calculated as a percentage of the central axis dose. The PD for both field sizes decreased with increasing distance from the beam edge. PD was also larger for 10 cm square field compared to 2.5 cm circular field for both depths. At 10 cm depth, the measured PD was 20% and 10% higher compared to that of 1.5 cm depth for 10 cm and 2.5 cm field size respectively. The PD for a given beam energy is a function of distance from the beam edge, field size and depth. At any depth measured, PD increases as the field size increases due to radiation scattered from the beam and scatter arising from within the medium. At deeper depth, more Compton electrons are produced and scattered to the peripheral region hence causes the PD to increase with depth. At any field size measured, peripheral dose increases as the depth increases. PD also increases as the field size increases.

The study is carried out to assess the exposure rate that could contribute to public exposure in ... more The study is carried out to assess the exposure rate that could contribute to public exposure in a radioiodine
ward delay tank facility of Radiotherapy, Oncology and Nuclear Medicine, Department, Hospital Universiti Sains
Malaysia (HUSM). The exposure rate at several locations including the delay tank room, doorway and at the public
walking route was measured using Victoreen 415P-RYR survey meter. The radioactive level of the 131I waste was
measured using Captus 3000 well counting system. The results showed that exposure rate and total count of the delay tank sample increased when the radioiodine ward was fully occupied with patient and reduced when the ward was vacant. Occupancy of radioiodine ward for two consecutive weeks had dramatically increased the exposure rate around the delay tank and radioactive level of 131I waste. The highest exposure rate and radioactive level was recorded when the ward was occupied for two consecutive weeks with 177.00 μR/h and 58.36 kcpm respectively. The exposure rate decreased 15.76 % when the door of the delay tank room was closed. The exposure rate at public walking route decreased between 15.58 % and 36.92 % as the distance increased between 1 and 3 m.

Treatment interruption is not uncommon in radiotherapy. Common reasons for treatment interruption... more Treatment interruption is not uncommon in radiotherapy. Common reasons for treatment interruption include machine breakdown, holidays and patient severe radiation reactions. Here RTtxGap, an Android application to assist calculations of compensation for treatment gap, is reported. It uses linear quadratic (LQ) model to calculate the biological effective dose (BED) that is used to solve for treatment gap compensations. Solutions are calculated using BED equation, with consideration for tissue proliferation. The accuracy of results has been verified using LQL Equiv software to be accurate within 1%. Five treatment interruption examples were used to illustrate the capability of the software to calculate the treatment compensation schedules. Solving these examples also illustrates the general consensus regarding compensating for unscheduled treatment interruptions, which ultimately involves balancing the BEDs of tumour and organ at risk. In addition to compensation for treatment gap, RTtxGap can also be used to calculate equivalent total dose in 2-Gy fraction (EQD2), to modify treatment schedule and to calculate alternative dose prescriptions having the same isoeffect.

This study was done to investigate the verification technique of treatment plan quality assurance... more This study was done to investigate the verification technique of treatment plan quality assurance for brachytherapy. It is aimed to verify the point doses in 192 Ir high dose rate (HDR) brachytherapy between Oncentra Masterplan brachytherapy treatment planning system and independent calculation software at a region of rectum, bladder and prescription points for both pair ovoids and full catheter set ups. The Oncentra TPS output text files were automatically loaded into the verification programme that has been developed based on spreadsheets. The output consists of source coordinates, desired calculation point coordinates and the dwell time of a patient plan. The source strength and reference dates were entered into the programme and then dose point calculations were independently performed. The programme shows its results in a comparison of its calculated point doses with the corresponding Oncentra TPS outcome. From the total of 40 clinical cases that consisted of two fractions for 20 patients, the results that were given in term of percentage difference, it shows an agreement between TPS and independent calculation are in the range of 2%. This programme only takes a few minutes to be used is preferably recommended to be implemented as the verification technique in clinical brachytherapy dosimetry. 1. Introduction Brachytherapy is a treatment method which requires the delivery of radiation directly into or onto the surface of the area to be treated. In order to ensure the optimal treatment of patients, an institution must develop a suitable quality control (QC) programme for brachytherapy sources, equipment and the physical and clinical procedures [1]. A quick calculation check to evaluate the output of a treatment plan allows detection of any possible errors. Seeking a compromise for efficiency both in the time required for the extra calculation and in the level of reliability. The purpose of this study was to verify the point doses in 192Ir HDR brachytherapy between Oncentra brachytherapy treatment planning and independent calculation software. To the specific review, this study compared the values of planned and independent calculated point doses of 192Ir of rectum and bladder in HDR brachytherapy. These studies also compared the values of planned and independent calculated point doses based on prescription points. Lastly, it was the comparison of the values of planned and independent calculated point doses between pair ovoid applicator and full catheter set ups at rectum, bladder and prescription points.

Introduction: Previous study has reported the experimental evidence of gold nanoparticles (AuNPs)... more Introduction: Previous study has reported the experimental evidence of gold nanoparticles (AuNPs) radiosensitization during continuous low-dose-rate gamma irradiation with lowenergy brachytherapy sources. It was discovered that the presence of AuNPs increased the biological effect by 70-130%. Hence, the purpose of this study is to investigate the effect of AuNPs on the biological effect in human fetal osteoblasts (hFOB) and HeLa cells irradiated with high-dose-rate (HDR) brachytherapy.

DESCRIPTION 15th International Congress of Radiation Research 2015 Abstract

Introduction: The purpose of this study is to compare the dosimetric characteristic of Gafchromic... more Introduction: The purpose of this study is to compare the dosimetric characteristic of Gafchromic films EBT2 and EBT3 for clinical photon and electron beams. This study focus on examining the film responses by comparing the calibration curves, percentage depth dose (PDD) curves and beam profiles of both films for different energy of photon and electron beams. Scanning and side orientation effects for both types of films were also investigated.

DESCRIPTION 15th International Congress of Radiation Research 2015 Abstract

The glow curve in TLD-100 was compared by applying long preheat time, short preheat time techniqu... more 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...

It has become a great challenge in the modern radiation treatment to ensure the accuracy of treat... more It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC). On the other hand, computed tomography (CT) images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d 80 (depth of the 80% dose beyond Z max ) using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.

Conventional two-dimensional (2D) treatment planning of intracavitary brachytherapy is still a co... more 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.
Keywords: International Commission on Radiation Units and Measurements (ICRU) reference points; intracavitary
brachytherapy treatment (ICBT); organ at risk (OAR) doses; two-dimensional (2D) treatment planning

It has become a great challenge in the modern radiation treatment to ensure the accuracy of treat... more It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC). On the other hand, computed tomography (CT) images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d80 (depth of the 80% dose beyond Zmax) using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.
Key words: Amalgam; dose calculation algorithm; Monte Carlo; streak artifact

Recently, Monte Carlo (MC) calculation method has reported as the most accurate method of predict... more Recently, Monte Carlo (MC) calculation method has reported as the most accurate method of predicting dose distributions in radiotherapy. In this present work investigation on the accuracy of MC (EGSnrc) in calculating electron beam central axis dose was conducted. Calculation of central axis depth dose distributions for 9 MeV electron beams from medical linear accelerator (Siemens Primus) was performed with BEAMnrc and DOSXYZnrc source code on personal desktop. Both source codes were included in EGSnrc package. Results were compared with an ion chamber measurement. On central axis dose MC data shows a good agreement with ion chamber measurement which is less than 2% percentage different. In this context the model is accurate and potentially to achieve the dose delivery as recommended by ICRU report.

The fi rst part of this study was about measurement of dosimetric parameters for small photon bea... more 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 influence 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 verified 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.

Keywords: Stereotactic radiosurgery (SRS), treatment planning system (TPS), pinpoint ionisation chamber, thermoluminiscent
detector (TLD), dose verifi cation

The aim of this project is to do comparative study in calibrating Ir-192 source using well ioniza... more The aim of this project is to do comparative study in calibrating Ir-192 source using well ionization chamber and air measurement using Farmer ionization chamber. To calibrate the Ir-192 using well ionization chamber, the HDR unit was programmed so that the source was at the most sensitive position inside the well-chamber. The charges were measured at 45 second time interval two times using the electrometer operated at +300V and -300V. Sources air kerma strength was determined based on the AAPM task group 43 brachytherapy dosimetry protocol. In the in-air method using the Farmer ionization chamber and calibration jig, the HDR unit was programmed so that the source was at the position that gave the maximum response in the catheter. The source air kerma strength was calculated using a formula proposed by Goestch et al, (1991). The Ir-192 source air kerma strength by the well chamber was 2.7780cGym2/h while in the in-air measurement was 2.609cGym2/h. Both results are less than 3% from the source strength written in the calibration certificate. The well chamber method is quite direct and less time consuming compare to the in-air measurement and this is the method utilised in HUSM.

Post mastectomy or lumpectomy irradiation of the chest wall or breast is common practice to minim... more Post mastectomy or lumpectomy irradiation of the chest wall or breast is common practice to minimize the local recurrences. Chest wall irradiation is a complicated technical procedure as the pathological target volume involves the normal structures like lung, heart, and head of humerus, esophagus and trachea known as organ at risk. The aim of this study was to verify the cases of the conventional tangential field technique among the breast cancer patients from year 2006 to 2011. In this study, the previous data of breast cancer patients treated with radiation from 2006 to 2011 were evaluated. Conventional 2D planning was done by taking body contour of the patient. Tangential verification films were taken in patients where excess of lung volume was suspected. The data was analyzed to verify the real lung volume irradiated. From a total 112 patients underwent tangential verification films during that period, 33% of patients underwent breast conservative surgery (BCS) while the rest underwent mastectomy. The depth of the field from the skin to 90% isodose ranges from 2.0 to 8.0 cm. However, 15 (13.4%) out 112 patients needed a replanning. As a conclusion, from 112 cases, the numbers of re-plan cases for year 2006 to 2011 were only 13 (11.61%) which is less than 15%. This result can be used by the centre who no dot have the facilities for simulation to verify the depth dose in 2D planning.

Teaching Documents by reduan abdullah

Quality Assurance in Medical Radiation II is part of requirement to be fulfilled by students for ... more Quality Assurance in Medical Radiation II is part of requirement to be fulfilled by students for Bachelor in Health Science (Medical Radiation). This manual book becomes the guidance for students while performing quality assurance works for medical radiation equipments as well as laboratory report writing.This manual book is divided into two parts that is Radiotherapy and Nuclear Medicine. There are guidelines including international protocols in performing quality assurance for medical radiation equipments especially Radiotherapy and Nuclear Medicine equipments.

DESCRIPTION 15th International Congress of Radiation Research 2015 Abstract

It has become a great challenge in the modern radiation treatment to ensure the accuracy of treat... more It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC). On the other hand, computed tomography (CT) images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d80 (depth of the 80% dose beyond Zmax) using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.
Key words: Amalgam; dose calculation algorithm; Monte Carlo; streak artifact

Keywords: Stereotactic radiosurgery (SRS), treatment planning system (TPS), pinpoint ionisation chamber, thermoluminiscent
detector (TLD), dose verifi cation

The purpose of this study was to measure the dosimetric parameters for small photon beams to be u... more The purpose of this study was to measure the dosimetric parameters for small photon beams to be used as input data for treatment planning computer system (TPS) and to verify dose calculated by TPS in Stereotactic Radiosurgery (SRS) procedure. The beam data required were Percentage Depth Dose (PDD), Off-axis Ratio (OAR), and Scatter Factor or Relative Output Factor. Small beams of 5mm to 45 mm diameter circular cone collimators used in SRS were utilized for beam data measurements. Two type of detectors were used which are pinpoint 3D ionization chamber (0.016cc) and EDR2 film dosimetry. The ionization chamber and EDR2 film give slightly similar results on PDD curve but for OAR measurement, the film gives more accurate results especially in penumbra length compared to ionization chamber due to characteristic of the film which has higher spatial resolution. For second part of this study, we reported the important quality assurance (QA) procedures before SRS treatment that influenced the dose delivery. These QA procedures consist of measurements on the accuracy in target localization and room laser’s alignment. The dose calculated to be delivered for treatment was verified using pinpoint ionization 3D chamber and TLD 100H. The mean deviation of measured dose using TLD 100H compared to calculated dose was 3.37%. Beside that, pinpoint ionization 3D chamber give more accurate results of dose compared to TLD 100H. The measured dose using pinpoint ionization 3D chamber are good agreement with calculated dose by TPS with deviation of 2.17%.The results are acceptable such as recommended by International Commission on Radiation Units and Measurements (ICRU) Report No. 50 that dose delivered to the target volume must be within ±5% error.