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oe1(光电查) - 科学论文

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出版时间
  • 2015
研究主题
  • Calibration process of OSL detectors
  • Iodine-131
  • OSL-BeO
  • Dosimetry of staff and patients
  • Optically Stimulated Luminescence (OSL)
应用领域
机构单位
  • Akdeniz University
72 条数据
?? 中文（中国） ▾

  • Characterization of a non-contact imaging scintillator-based dosimetry system for total skin electron therapy

    摘要： Surface dosimetry is required for ensuring effective administration of total skin electron therapy (TSET); however, its use is often reduced due to the time consuming and complex nature of acquisition. A new surface dose imaging technique was characterized in this study and found to provide accurate, rapid and remote measurement of surface doses without the need for post-exposure processing. Disc-shaped plastic scintillators (1 mm thick x 15 mm) were chosen as optimal-sized samples and designed to attach to a flat-faced phantom for irradiation using electron beams. Scintillator dosimeter response to radiation damage, dose rate, and temperature were studied. The effect of varying scintillator diameter and thickness on light output was evaluated. Furthermore, the scintillator emission spectra and impact of dosimeter thickness on surface dose were also quantified. Since the scintillators were custom-machined, dosimeter-to-dosimeter variation was tested. Scintillator surface dose measurements were compared to those obtained by optically stimulated luminescence dosimeters (OSLD). Light output from scintillator dosimeters evaluated in this study was insensitive to radiation damage, temperature, and dose rate. Maximum wavelength of emission was found to be 422 nm. Dose reported by scintillators was linearly related to that from OSLDs. Build-up from placement of scintillators and OSLDs had a similar effect on surface dose (3.9% increase). Variation among scintillator dosimeters was found to be 0.3 ± 0.2%. Scintillator light output increased linearly with dosimeter thickness (~1.9×/mm). All dosimeter diameters tested were able to accurately measure surface dose. Scintillator dosimeters can potentially improve surface dosimetry-associated workflow for TSET in the radiation oncology clinic. Since scintillator data output can be automatically recorded to a patient medical record, the chances of human error in reading out and recording surface dose are minimized.

    关键词： non-contact,surface dosimetry,optical imaging,scintillator,remote

    更新于2025-11-14 15:30:11

  • Structural, photoluminescence and thermoluminescence study of novel Li+ co-activated lanthanum oxide activated with Dy3+ and Eu3+ obtained by microwave-assisted solution combustion synthesis

    摘要： Stimulated luminescence of novel La2O3 nanophosphors doped with Dy3+ and Eu3+ and co-activated with Li+, prepared by microwave-assisted solution combustion synthesis, was investigated for the very first time. X-ray diffraction results indicated hexagonal La2O3 crystalline phase. Lanthanide and Li+ doping did not affect the La2O3 crystal structure. Scanning electron microscopy images showed nanoparticle morphologies such as plates, rods and irregular shapes. Photoluminescence spectra of La2O3:Dy3+, Li+ exhibited blue and green emission bands due to Dy3+ transitions. For La2O3:Eu3+, Li+, sharp emission lines, corresponding to the optical transitions of Eu3+ were observed. Thermoluminescence glow curve of La2O3:Dy3+, Li+ previously exposed to beta radiation exhibited a prominent glow peak located at ～46 °C, possibly useful for after-glow or persistent luminescence applications, whereas La2O3:Eu3+, Li+ curve, displayed three intense peaks at ～50, ～110 and ～150 °C. Thermoluminescent signal repeatability and decay curve asymptotic behaviour could place La2O3:Eu3+, Li+ as suitable for medium and high-dose radiation dosimetry applications.

    关键词： Dosimetry,Thermoluminescence,Solution combustion synthesis,La2O3 co-doped nanoparticles

    更新于2025-10-22 19:40:53

  • Rapid Multisite Remote Surface Dosimetry for Total Skin Electron Therapy: Scintillator Target Imaging

    摘要： Verifying radiation-field uniformity in total skin electron therapy is important to ensuring adequate and effective treatment administration. This clinical study presents a novel, scintillation-based, optical-imaging technique for conducting surface dosimetry in patients undergoing total skin electron therapy. The system exceeded the ease of use of established dosimetry techniques at a similar level of accuracy.

    关键词： total skin electron therapy,optical imaging,surface dosimetry,scintillator,remote dosimetry

    更新于2025-09-23 15:23:52

  • Evaluation of patient effective dose in a PET/CT test

    摘要： The positron emission tomography (PET)/computed tomography (CT) technique generates high doses in patients because two radiodiagnostic modalities are used in a single examination. In this study, the absorbed and effective doses generated by CT scans and by the incorporation of radiopharmaceutical solution were evaluated in 19 organs. It was found that 78.2% of the effective dose in PET/CT examinations comes from the CT scan. With an activity of 3.33 MBq/kg, 18F-FDG contributes 21.8% of the final effective dose.

    关键词： Patient dosimetry,PET/CT,Computed tomography

    更新于2025-09-23 15:23:52

  • Observation of strong thermally transferred optically stimulated luminescence (TT-OSL) in BeO

    摘要： This work reports the observation of strong thermally transferred optically stimulated luminescence (TT-OSL) signal of BeO OSL ceramic detectors. If the detector is irradiated and the OSL signal is measured for a prolonged time (bleached), subsequent OSL measurements result in zero signal. If the same detector, however, is heated to temperatures in the 225 – 335 °C range (at 5 °C/s), subsequent OSL measurements at room temperature result in an intense signal, even without additional irradiation. The TT-OSL is maximum for a pre-heating to 275 °C (if heated linearly at 5 °C/s), reaching a value of 56 % of the original OSL signal. Both OSL and TT-OSL are reproducible (~3 % standard deviation) and linear with dose over the dose range investigated (up to 100 mGy). The shape of the OSL and TT-OSL curves are essentially identical. A possible explanation for this phenomenon is the thermally stimulated transfer of trapped charges from optically inactive traps to optically active traps responsible for the OSL signal. Correlation between the OSL, TT-OSL and the thermoluminescence (TL) peaks suggests the trapping centers associated with the TL peak at ~310 °C/s (at 5 °C/s) as the source of the trapped charges. These results have implication for the re-estimation of the OSL signal in BeO detectors accidentally exposed to light. Not only they provide further evidence that the material is not completely reset simply by bleaching (optical stimulation), but open a new line of investigation into the underlying TL/OSL mechanisms in BeO.

    关键词： thermoluminescence,optically stimulated luminescence,BeO,thermally transferred optically stimulated luminescence,luminescence dosimetry,recuperation

    更新于2025-09-23 15:23:52

  • Development of a 2D dosimeter using the optically stimulated luminescence of NaMgF3:Eu with CCD camera readout

    摘要： A two-dimensional (2D) dosimeter has been developed using tissue-equivalent NaMgF3:Eu as a radiation-sensing material. The bulk compound shows optically stimulated luminescence (OSL) after irradiation in the form of 359 nm Eu2+ emission and where the OSL stimulation occurs at wavelengths above 400 nm. The OSL integrated intensity is shown to be linear up to at least 100 Gy when stimulated with 445 nm light. When the OSL is detected using a thermoelectrically cooled CCD camera, 2D X-ray images can be obtained and the measured intensity is proportional to the total radiation dose. NaMgF3:Eu can be incorporated into epoxy to produce imaging films and both the bulk compound and a film are characterised using the 2D setup. The noise equivalent dose in 2D for the film is determined to be 14 mGy. The modulation transfer function (MTF) is determined and the spatial resolution at MTF = 0.2 is 2.9 lp/mm for the bulk material and 1.25 lp/mm for the film. Our results show that NaMgF3:Eu has potential in the field of 2D dosimetry, where the response to radiation is linear to high doses, sensitive to low doses, and doses can be resolved with a spatial resolution below 1 mm.

    关键词： fluoroperovskite,optically stimulated luminescence,dosimetry,NaMgF3

    更新于2025-09-23 15:23:52

  • Application of TG-100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator

    摘要： Purpose: A new type of linear accelerator (linac) was recently introduced into the market by a major manufacturer. Our institution is one of the early users of this pre-assembled and pre-configured dual-layer MLC, ring-gantry linac – HalcyonTM (1st version). We performed a set of full acceptance testing and commissioning (ATC) measurements for three Halcyon machines and compared the measured data with the standard beam model provided by the manufacturer. The ATC measurements were performed following the guidelines given in different AAPM protocols as well as guidelines provided by the manufacturer. The purpose of the present work was to perform a risk assessment of the ATC process for this new type of linac and investigate whether the results obtained from this analysis could potentially be used as a guideline for improving the design features of this type of linac. Methods: AAPM’s TG100 risk assessment methodology was applied to the ATC process. The acceptance testing process relied heavily on the use of a manufacturer-supplied phantom and the automated analysis of EPID images. For the commissioning process, a conventional measurement setup and process (e.g. use of water tank for scanning) was largely used. ATC was performed using guidelines recommended in various AAPM protocols (e.g. TG-106, TG-51) as well as guidelines provided by the manufacturer. Six medical physicists were involved in this study. Process maps, process steps and failure modes (FMs) were generated for the ATC procedures. Failure Modes and Effects Analysis (FMEA) were performed following the guidelines given in AAPM TG-100 protocol. The top 5 and top 10 highest-ranked FMs were identified for the acceptance and commissioning procedures respectively. Quality control measures were suggested to mitigate these FMs. Results: A total of 38 steps and 88 FMs were identified for the entire ATC process. 14 steps and 34 FMs arose from acceptance testing. The top 5 FMs that were identified could potentially be mitigated by the manufacturer. For commissioning, a total of 24 steps and 54 potential FMs were identified. The use of separate measurement tools that are not machine-integrated has been identified as a cause for the higher number of steps and FMs generated from the conventional ATC approach. More than half of the quality control measures recommended for both acceptance and commissioning could potentially be incorporated by the manufacturer in the design of the Halcyon machine. Conclusion: This paper presents the results of Failure Modes and Effects Analysis and quality control measures to mitigate the failure modes for the acceptance testing and commissioning process for Halcyon machine. Unique FMs that result from the differences in the ATC guidelines provided by the vendor and current conventional protocols, and the challenges of performing the ATC due to the new linac features and ring-gantry design were highlighted for the first time. The FMs identified in the present work along with the suggested quality control measures, could potentially be used to improve the design features of future ring-gantry type of linacs that are likely to be pre-assembled, pre-configured, and heavily reliant on automation and image-guidance.

    关键词： new ring-gantry linac,reference dosimetry,TG100,TG-51,Failure Modes and Effects Analysis (FMEA),Acceptance testing and Commissioning

    更新于2025-09-23 15:23:52

  • An algorithmic approach to single probe Cherenkov removal in pulsed X-ray beams

    摘要： Purpose: The removal of Cherenkov light in an optical dosimetry system is an important process to ensure accurate dosimetry without compromising spatial resolution. Many solutions have been presented in the literature, each with advantages and disadvantages. We present a methodology to remove Cherenkov light from a scintillator fibre optic dosimeter in a pulsed megavoltage X-ray beam using the temporal waveform across the pulse. Methods: A sample waveform of Cherenkov light can be measured by exposing only the fibre to the beam. By assuming that the Cherenkov waveform closely matches the intensity of incident radiation, this waveform can be convoluted with the instantaneous scintillation response function to generate an expected scintillation signal. By finding the least-squares fit between these two functions and the experimental data, the estimated Cherenkov contribution can be subtracted off the net signal. This can be applied for arbitrarily complex Cherenkov waveforms (within the 2 ns timing resolution of the data acquisition), and in fact the results suggest more fluctuations in the waveforms provide a better fit to data. Results: Four beam profiles for different field sizes and energies were found with this method. They closely matched references data measured with ionisation chamber with average differences across the beam no more than 4%. Noisy waveforms are assumed to be the primary cause of differences between the analysed scintillator and IC results. We propose methods for improving the results and optimising the data acquisition and analysis processes. Conclusions: These results demonstrate that it is possible and effective with a single probe to use function-fitting of expected data to experimental to remove a complicated Cherenkov signal from the net light signal in pulsed-beam optical dosimetry.

    关键词： x-ray,scintillators,fiber-optic dosimetry,microbeam radiation therapy

    更新于2025-09-23 15:23:52

  • Feasibility Study of the microDiamond Detector for Measurement of Small Field Photon Beam

    摘要： The dosimetry of very small fields is challenging for several reasons including a lack of lateral electronic equilibrium, large dose gradients, and the size of detector in respect to the field size. The objective of this work was to evaluate the suitability of a new commercial synthetic diamond detector, namely, the PTW 60019 microDiamond, for the small field dosimetry in cyberknife photon beams of 6 different collimator size (from 5 mm to 30 mm). Measurements included dose linearity, dose rate dependence, output factors (OF), percentage depth doses (PDD) and off center ratio (OCR). The results were compared to those of pinpoint ionization chamber, diamond detector, microLion liquid Ionization chamber and diode detector. The dose linearity results for the microDiamond detector showed good linearly proportional to dose. The microDiamond detector showed little dose rate dependency throughout the range of 100～600 MU/min, while microLion liquid Ionization chamber showed a significant discrepancy of approximately 5.8%. The OF measured with microDiamond detector agreed within 3.8% with those measured with diode. PDD curves measured with silicon diode and diamond detector agreed well for all the field sizes. In particular, slightly sharper penumbras are obtained by the microDiamond detector, indicating a good spatial resolution. The results obtained confirm that the new PTW 60019 microDiamond detector is suitable candidate for application in small radiation fields dosimetry.

    关键词： Small field,microDiamond detector,Dosimetry

    更新于2025-09-23 15:23:52

  • Image-based Absorbed Dosimetry of Radioisotope

    摘要： An absorbed dose calculation method using a digital phantom is implemented in normal organs. This method cannot be employed for calculating the absorbed dose of tumor. In this study, we measure the S-value for calculating the absorbed dose of each organ and tumor. We inject a radioisotope into a torso phantom and perform Monte Carlo simulation based on the CT data. The torso phantom has lung, liver, spinal, cylinder, and tumor simulated using a spherical phantom. The radioactivity of the actual absorbed dose is measured using the injected dose of the radioisotope, which is Cu-64 73.85 MBq, and detected using a glass dosimeter in the torso phantom. To perform the Monte Carlo simulation, the information on each organ and tumor acquired using the PET/CT and CT data provides anatomical information. The anatomical information is offered above mean value and manually segmented for each organ and tumor. The residence time of the radioisotope in each organ and tumor is calculated using the time activity curve of Cu-64 radioactivity. The S-values of each organ and tumor are calculated based on the Monte Carlo simulation data using the spatial coordinate, voxel size, and density information. The absorbed dose is evaluated using that obtained through the Monte Carlo simulation and the S-value and the residence time in each organ and tumor. The absorbed dose in liver, tumor1, and tumor2 is 4.52E-02, 4.61E-02, and 5.98E-02 mGy/MBq, respectively. The difference in the absorbed dose measured using the glass dosimeter and that obtained through the Monte Carlo simulation data is within 12.3%. The result of this study is that the absorbed dose obtained using an image can evaluate each difference region and size of a region of interest.

    关键词： Absorbed dosimetry,Torso phantom,Cu-64,PET/CT,Glass dosimeter

    更新于2025-09-23 15:23:52