Papers by Keyword: Dosimetry

Abstract: Thermoluminescence (TL) characteristics for various cross-sections of 6 mole% of tailor-made Ge-doped cylindrical optical fibers were determined. The general TL characteristic i.e., dose rate dependence, energy dependence, dose response and reproducibility of the samples have been investigated. The samples were irradiated using electron beam (Linac) and been exposed to dose ranging from 1 to 4 Gy. The cylindrical optical fibers provide highly linear dose response within the clinical relevant dose range, independence of radiation energy over the range of energies investigated, independence of dose rate and excellent reproducibility. This research shows that germanium doped silica fibers have high potential of dosimetric properties and suitable as TL-mode detectors in instances of radiotherapy (clinical dosimetry).

Abstract: Solid polymeric track detectors (SPTDs), due to their insensitivity to low LET radiations and integrating nature of signal registration, are found to be effective and convenient for neutron measurements, particularly in pulsed and mixed radiation fields such as in particle accelerator environments. This paper in addition to reviewing some of the existing methods of neutron spectrometry and dosimetry, explores new approaches on the use of SPTDs for neutron measurements, elaborates on the extended energy response and rapid etching techniques of SPTDs along with some new results. Microwave induced chemical etching (MICE) technique, recently introduced for rapid and efficient processing of track detectors is discussed in the paper.Contents of Paper

Abstract: This study concerns on the thermoluminescence (TL) characteristics of carbon doped aluminum oxide (Al₂O₃:C) as ionizing radiation dosimeter. The thermoluminescence response, linearity and sensitivity subjected to Co-60 gamma irradiation were investigated. Carbon doped (0.2 mol %) aluminum oxide samples in form of powder were irradiated to 1.25 MeV Co-60 gamma ray with doses ranging from 1 Gy to 50 Gy. Irradiations were performed by using Co-60 gamma ray model 220 Excel with the source activity, A = 2.310925534 kGy h¹ at Universiti Kebangsaan Malaysia. The glow curves were analysed to determine various characterizations of the TLDs. It is shown that the glow curve of the sample contains a single peak at about 180°C with broad peak appears at the right of the spectrum. It is also shown that the TL intensity has linear relationship with delivered dose and the average TL sensitivity was calculated as 3.30 nC mg^-1 Gy^-1.

Abstract: We propose a failure detection method for GaN-based dosimetric systems, which basically consist of a GaN-incorporated optical fiber probe coupled to a photodetection module. The method consists in introducing UV excitation with a 285nm LED, and detecting the photoluminescence (PL) of the GaN transducer centered at 380nm. Spectral analysis of the detected signal allows verification of normal operation and identification of failure cases, due to problems of GaN-fiber coupling and poor fiber connection between probe and photodetection module. The proposed method is implemented and experimentally tested, including the use of a 660nm LED to illuminate the probe to verify the transmission ratio between probe and photodetection module. The validity of this method has been verified.

Abstract: In this paper, the novel ZnO nanophosphors is synthesized by solgel method. The study exposed ZnO nanophosphors samples in Gamma (y) radiation to investigate their thermo-luminescence (TL) intensity as a function of temperature. The thermo-luminescence response has been studied in the dose range 0.291.16 kGy and it is observed that the thermo-luminescence response increases with increase in the dose. Moreover, the TL intensity increases with temperature and attains its maximum value near 200 Cand decreases after this temperature. Keywords: Dosimetry; Thermo-luminescence; Zinc oxide; Nanophosphors.

Abstract: In this paper we have reported excellent luminescence properties of novel nanophosphors synthesized through solgel method with narrow size distribution. The size and morphology of the prepared ZnO nanophosphors has been confirmed through XRD and SEM. We have investigated their photo-luminescence (PL) intensity as a function of wavelength. We have prepared ZnO nanophosphor of size 6 nm. It is observed two different emission peaks near 375 nm in the ultraviolet (UV) and near 525 nm in the visible region. The prepared ZnO nanophosphor has enough potential for optoelectronic applications. Keywords: Dosimetry; Thermo-luminescence; Zinc oxide; Nanophosphors.

Abstract: This article presents an online checking method to get the accumulated x-ray radiation dose for Computed Tomography imaging investigations performed to the human patients. When the patient arrived to imaging center to request a new investigation the system will generate an online verification based on the CNP. The software application will show a warning message if the radiation doze is exceeded. The software technologies used are based on web services and HL7 Version 2.3.1 standard.

Abstract: In this work, results on the thermoluminescence dosimetry properties of beta particle irradiated ZnO obtained by thermal annealing of chemically synthesized ZnS are reported. ZnS powder was sintered at 950 °C during 24 h in air, in order to obtain pellet-shaped ZnO samples. The thermoluminiescence (TL) intensity of ZnO previously exposed to beta radiation increased as the dose increased in the 0.025-6.4 kGy interval studied. Characteristic glow curves exhibited two emission maxima at ~ 94 and ~ 341 °C. The dosimetric peak located at ~ 341 °C shifted towards lower temperatures as the dose increased, which indicates that second-order kinetic processes are involved in the thermoluminiescence emission. The dose response of ZnO showed a linear behaviour in the 0.025 Gy-0.8 kGy dose interval, which makes this material suitable and promising for medical, industrial and also space dosimetry applications. The thermoluminescence total signal faded down 48 % 6 h after irradiation and showed an asymptotic behaviour for longer times, due mainly to the ~ 341 °C stable and dosimetric glow peak.

Abstract: This study proposed a CCD-based (charge-coupled device) optical computed tomography scanner (CT-s2) for 3D gel dosimetry. A parallel laser light was generated to pass through the gel sample using a diffuser and collimating lens. A CCD was used to capture projection image of gel sample at each step. An image reconstruction algorithm, filtered-back projection (FBP) technique was used to reconstruct the 3D image. Two better rotational steps are suggested as 1.0 degree and 1.5 degree for considering both of angular resolution and position deviation. The un-irradiated and irradiated BANG gel samples were scanned and reconstructed using FBP technique. Some artifacts were found in reconstructed images. Some discussions for artifacts were conducted and some solutions provided by previous researches to reduce these artifacts will be evaluated in the future work.

Abstract: Objective: To compare dose-volume histograms (DVHs) and the dose distribution of three-dimensional conformal radiotherapy(3DCRT),7 fields radiotherapy(7FRT) and intensity-modulated radiotherapy (IMRT) of treatment planning in gastric cancer. Methods: We selected 5 patients with gastric cancer, they were pathologically confirmed stage T3,T4 or N+ gastric cancer. All patients underwent radical gastrectomy. A dosimetry study was carried out on these five patients. For each patient, three kinds of treatment planning were designed with a prescribed dose of 45Gy to 95％of PTV.Many kinds of parameters of these plans in each patient were compared: isodose distributions line、dose-volume histogram(DVH)、V95%、V110%、CI、HI、EI of target volume and the dose of related critical organs. Results: IMRT was superior to 3DCRT and 7F-RT in dose uniformity（p＜0.05）, there was no statistical difference between 3DCRT and 7FRT in CI（p>0.05）.IMRT had better dose conformity than 3DCRT and 7FRT（p＜0.05）, and 3DCRT was better than 7FRT in CI（p＜0.05）.IMRT showed better EI than 3DCRT and 7FRT（p＜0.05）,there was no statistical difference between 3DCRT and 7FRT in EI（p>0.05）.IMRT had advantage at sparing liver compared with 3DCRT and 7FRT（p＜0.05）,7FRT showed better D1/3 of liver than 3DCRT（p＜0.05）,but there was no statistical difference between 3DCRT and 7FRT in Dmean of liver（p>0.05）.IMRT expressed better Dmax of spinal cord than 3DCRT and 7F-RT（p＜0.05）, and 7FRT was better than IMRT in Dmax of spinal cord（p＜0.05）.But the dose received by the both kidneys were not significantly different. Conclusion: IMRT is superior to 3DCRT and 7FRT,and 3DCRT plans showed better CI and Dmax of spinal cord composed to 7FRT,and 7FRT was superior to 3DCRT in D1/3 of liver. IMRT for gastric cancer had physics advantage for clinical application.