Photoluminescence and thermoluminescence dosimetry properties of Ag/Y co-doped ZnO nanophosphor for radiation measurements.

This work explores the thermoluminescence (TL) and photoluminescence (PL) properties of Ag/Y co-doped zinc oxide (ZnO) nanophosphor. The proposed dosimeter was prepared by the coprecipitation method and sintered at temperatures from 400°C to 1000°C in an air atmosphere. Raman spectroscopy was studied to investigate the structural features of this composition. The new proposed dosimeter revealed two peaks at 150°C and 175°C with a small shoulder at high temperature (225°C). The PL spectrum showed strong green emissions between 500 to 550 nm. The Raman spectrum showed many bands related to the interaction between ZnO, silver (Ag), and yttrium oxide (Y2 O3 ). The rising sintering temperature enhanced the TL glow curve intensity. The Ag/Y co-doped ZnO nanophosphor showed an excellent linearity index within a dose from 1 to 4 Gy. The minimum detectable dose (MDD) of the Ag/Y co-doped ZnO nanopowder (pellets) equaled 0.518 mGy. The main TL properties were achieved in this work as follows: thermal fading (37% after 45 days at 1 and 4 Gy), optical fading (53% after 1 h and 68% after 6 h by exposure to sunlight), effective atomic number (27.6), and energy response (flat behavior from 0.1 to 1.3 MeV). Finally, the proposed material shows promising results nominated to be used for radiation measurements.

Influence of disinfection methods used in hospitals on monitoring personal dose of external irradiation during COVID-19 / 中国辐射卫生

@#<b>Objective</b> To study whether the disinfection methods for thermoluminescence dosimeters used by major hospitals during the COVID-19 pandemic had an impact on monitoring personal dose of external irradiation, and to screen for the disinfection procedures suitable for use during the pandemic. <b>Methods</b> Hospitals with fever clinics during the epidemic in Shandong Province were selected from March to October 2020, we investigated the disinfection methods as well as the types and frequency of use of disinfection supplies used for thermoluminescence dosimeters during the pandemic in hospitals. Simulations were performed in experimental and control groups. <b>Results</b> The average doses measured by the disc dosimeter with different disinfection methods and the control group were 0.92-0.99 mSv and 0.98 mSv, respectively, and the deviation was ≤ 6%. The average doses measured by the glass tube dosimeter with different disinfection methods and the control group were 0.20-0.22 and 0.21, respectively, and the deviation was ≤ 5%. <b>Conclusion</b> The results showed that the commonly used disinfection methods had no influence on personal dose monitoring, but some disinfection measures were not suitable for dosimeters.

Dose Variations Using an X-Ray Cabinet to Establish in vitro Dose-Response Curves for Biological Dosimetry Assays.

In biological dosimetry, dose-response curves are essential for reliable retrospective dose estimation of individual exposure in case of a radiation accident. Therefore, blood samples are irradiated in vitro and evaluated based on the applied assay. Accurate physical dosimetry of the irradiation performance is a critical part of the experimental procedure and is influenced by the experimental setup, especially when X-ray cabinets are used. The aim of this study was to investigate variations and pitfalls associated with the experimental setups used to establish calibration curves in biological dosimetry with X-ray cabinets. In this study, irradiation was performed with an X-ray source (195 kV, 10 mA, 0.5 mm Cu filter, dose rate 0.52 Gy/min, 1st and 2nd half-value layer = 1.01 and 1.76 mm Cu, respectively, average energy 86.9 keV). Blood collection tubes were irradiated with a dose of 1 Gy in vertical or horizontal orientation in the center of the beam area with or without usage of an additional fan heater. To evaluate the influence of the setups, physical dose measurements using thermoluminescence dosimeters, electron paramagnetic resonance dosimetry and ionization chamber as well as biological effects, quantified by dicentric chromosomes and micronuclei, were compared. This study revealed that the orientation of the sample tubes (vertical vs. horizontal) had a significant effect on the radiation dose with a variation of -41% up to +49% and contributed to a dose gradient of up to 870 mGy inside the vertical tubes due to the size of the sample tubes and the associated differences in the distance to the focal point of the tube. The number of dicentric chromosomes and micronuclei differed by ~30% between both orientations. An additional fan heater had no consistent impact. Therefore, dosimetric monitoring of experimental irradiation setups is mandatory prior to the establishment of calibration curves in biological dosimetry. Careful consideration of the experimental setup in collaboration with physicists is required to ensure traceability and reproducibility of irradiation conditions, to correlate the radiation dose and the number of aberrations correctly and to avoid systematical bias influencing the dose estimation in the frame of biological dosimetry.

Evaluating photoneutron dose equivalents for lung cancer using PMMA phantoms undergoing 15 MV IMRT.

BACKGROUND: According to statistics of the Ministry of Health and Welfare in 2017, the second leading cause of death in Taiwan was lung cancer. OBJECTIVE: Routine treatment planning does not consider photoneutron dose equivalent (PNDE) of patient induced secondary radiation resulting from primary exposure of lung cancer. However, such treatment is potentially important for improving estimates of health risks. METHODS: This study used 10, 30, 50, 70, and 90 kg of polymethylmethacrylate (PMMA) phantoms as patient to measure PNDE varying anatomical area during lung cancer of intensity modulated radiotherapy (IMRT) treatment. Paired thermoluminescent dosimeters (TLD-600 and 700) were calibrated using university reactor neutrons. TLDs were inserted into phantom which was closely corresponded of the represented tissues or organs. RESULTS: Neutron doses (ND) of organ or tissue (N⁢DT) were determined in these phantoms using paired TLDs approach. The risks of incurring fatal secondary malignancies, maximum statistical and total errors were estimated. Evaluated PNDE ranged from 0.80 ± 0.12 to 0.56 ± 0.08 mSv/Gy for these phantoms. CONCLUSION: The estimated N⁢DT decreased with increasing distance that is from the central axis. Evaluated PNDE and N⁢D𝑠𝑘𝑖𝑛 for these phantoms were discussed. This investigation also identified secondary risks associated with PNDE relating to radiation protection.

Evaluating environmental radiations of the tomotherapy facility by optimizing full factorial design of the TLD technique.

BACKGROUND: In the last 40 years, the number of deaths due to cancer has been the highest in TaiwanOBJECTIVE: To optimize the readout system of the thermoluminescent dosimeter (TLD)-100H, the radiation rates among the Tomotherapy (TOMO) facility of the Department of Radiology Oncology of Chung Shan Medical University Hospital (CSMUH) were calculated with a 32 full factorial design (FFD). METHODS: A ten-month survey of the facility was employed using the sensitive and accurate TLD method. The TLD system was optimized for maximum temperature, heat rate, and preheat temperature of Harshaw 3500 reader. Eight analyzed groups with different factors were tested. RESULTS: The TOMO facility had significantly different radiation rates. The farther away from the gantry head, environmental radiation rates. The half value layer (HVL) was also determined. These results were compared with published. No significant contributions of environmental gamma radiations were detected except in the treatment room. CONCLUSIONS: Those were far below the occupational doses recommended by ICRP 60.

Experimental study on measurement of short pulsed and high-dose-rate X-ray by therapeutic grade ionization chamber / 中华放射医学与防护杂志

Objective:To investigate the application of therapeutic grade ionization chamber to rapid measurement of short pulsed and high-dose-rate X-ray.Methods:The half-value layer of pulsed X-ray caused by an electron accelerator was measured by interpolation method and its equivalent energy was estimated. The cumulative doses from a certain amount of pulsed radiation at different distances in the same direction around the equipment were compared using the therapeutic grade ionization chamber and thermoluminescence measurement method . The relationship between the measurement result by using ionization chamber dosimeter and the distances away from source was analyzed. The cumulative doses from a certain amount of pulsed radiation at the same location at different frequencies were compared.Results:In working condition, 100 pulses of radiation were received accumulatively at 1 to 12 meters away from the outer wall of the equipment. The range of air Kerma was 0.08-9.65 mGy measured by using thermoluminescence dometers and 0.08 - 9.85 mGy using the ionization chamber dosimeters, respectively. The difference between both is within 10%. At different frequencies (1-10 Hz), there was no significant difference in X-ray air Kerma from 100 pulses measured by ionization chamber dosimeter at 2 m away from the front of the equipment ( P>0.05). Conclusions:The therapeutic grade ionization chamber dosimeter can be used for the rapid measurement of short pulsed X-ray radiation dose in the range of dose rates and pulse frequencies involved in the experimental accelerator device.

TLD environmental monitoring of new scanner facilities at the Nuclear Medicine Department of the Taiwan Medical University Hospital.

OBJECTIVE: Single-photon emission computed tomography (SPECT) as well as dual energy X-ray absorptiometry (DXA) scanners were designed in July 2018 at the Nuclear Medicine Department (NM), of the Taiwan Medical University Hospital. These scanners emit substantial X-rays from the target, which are tungsten, iron. Therefore, patients undergoing SPECT and DXA diagnosis, in addition to medical personnel, are exposed to undesirable photon leakage. METHODS: Following administration of radiopharmaceuticals, patients become radioactive sources; thus, it is necessary to evaluate a possible increase in the environmental gamma exposure rates in the NM as a result of the operation of the new scanners. A three month evaluation of environmental radiation in the NM was performed using the accurate and sensitive TLD-100H approach, which gives an error rate less than 10%. RESULTS: Detected exposure radiation rates in the NM ranged from 0.12 ± 0.02 to 1.00 ± 0.15 mSv per month, indicating that the imaging room had significantly different radiation rates. The results were compared with previous results, and no significant contribution to the enhancement of environmental gamma radiation was detected, which remained far below the occupational dose recommended by ICRP 60. The minimum detectable dose (MDD) for environmental radiation is also discussed herein to demonstrate the reliability of TLD-100H. CONCLUSION: Recommendations were sent to the authorities of AEC-ROC to implement actions that could reduce doses at these high-dose locations to meet the ALARA principle.

Evaluation of Breast Cancer Radiation Therapy Techniques in Outfield Organs of Rando Phantom with Thermoluminescence Dosimeter.

BACKGROUND: Given the importance of scattered and low doses in secondary cancer caused by radiation treatment, the point dose of critical organs, which were not subjected to radiation treatment in breast cancer radiotherapy, was measured. OBJECTIVE: The purpose of this study is to evaluate the peripheral dose in two techniques of breast cancer radiotherapy with two energies. MATERIAL AND METHODS: Eight different plans in two techniques (conventional and conformal) and two photon energies (6 and 15 MeV) were applied to Rando Alderson Phantom's DICOM images. Nine organs were contoured in the treatment planning system and specified on the phantom. To measure the photon dose, forty-eight thermoluminescence dosimeters (MTS700) were positioned in special places on the above nine organs and plans were applied to Rando phantom with Elekta presice linac. To obtain approximately the same dose distribution in the clinical organ volume, a wedge was used on planes with an energy of 6 MeV photon. RESULTS: Point doses in critical organs with 8 different plans demonstrated that scattering in low-energy photon is greater than high-energy photon. In contrast, neutron contamination in high-energy photon is not negligible. Using the wedge and shield impose greater scattering and neutron contamination on patients with low-and high-energy photon, respectively. CONCLUSION: Deciding on techniques and energies required for preparing an acceptable treatment plan in terms of scattering and neutron contamination is a key issue that may affect the probability of secondary cancer in a patient.

[Radiation Dose of Body Surface at Sensitive Organs and Its Protective Precaution in Head CT Scanning:Initial Experience.]

OBJECTIVES: To investigate the radiation dose of body surface at sensitive organs using different protective precaution in head CT scanning. METHODS: The standard phantom received head routine sequence scanning with dual-source computed tomography.The phantoms were scanned with three different protective precaution:group A (without protective clothing),group B (wearing lead collar and cover lead clothes),group C (wearing lead collar and clothes without cuffs).The thermoluminescence dosimeters (TLD) was placed on the body surface corresponding to sensitive organs to measure radiation dose. RESULTS: The volume of CT dose index (CTDIvol) and dose length product (DLP) in group A,B and C were same,44.06 mGy and 634 mGy×cm,respectively.There was no statistic significant difference between group A,B and C of radiation dose in non-protective region (P=0.712).The radiation dose in the neck region under the cover of lead collar in group A,B and C were (2.57 ± 0.65) mGy,(2.30 ± 1.10) mGy and (2.48 ± 0.90) mGy,respectively,without statistic significant difference between groups (P=0.816).However,the radiation dose in abdominal region of group A was (0.66±0.37) mGy,which was significantly higher than that of group B [(0.18 ± 0.18) mGy] and group C [(0.18±0.16) mGy],The radiation dose in dorsal region of group A was (0.55±0.43) mGy,which was significantly higher than that of group B [(0.28±0.22) mGy],while that of group C [(0.14±0.12) mGy] was significantly lower than group B. CONCLUSIONS: Compared to traditional lead coverage,lead collar and cloth can decrease the radiation dose of body surface and sensitive organs in head scan with dual source CT.

Study of real-time measurements of occupational staff's eye lens doses by direct-reading dosimeters in interventional procedures / 中华放射医学与防护杂志

Objective To establish the methods for measuring the dose to occupational staff's eye lens in interventional procedures with direct-reading dosimeters,and to realize the real-time monitoring of eye lens dose and warning for high dose rate,thus providing the scientific basis of the staff radiological protection in interventional procedures.Methods Direct-reading dosimeters were calibrated with personal dose equivalent HP (3).The eye lens doses for occupational staff in different kinds of interventional procedures were measured by the devices with both single-and double X-ray tubes.The data obtained fromthe direct-reading dosimeters was compared to those obtained from TLDs.Results Direct-reading dosimeters showed good linear fitting with the calibration of HP (3),and the coefficients of variation were lower than 5％.The average eye lens HP (3) for the main operator in coronary arteriography and stent implantation in brain obtained by direct-reading dosimeters were 12.0 and 24.5 μSv,respectively,whereas those obtained by TLDs were 11.9 and 22.7 μSv,respectively.The direct-reading dosimeters gave similar t~nds as TLDs do so.The direct-reading dosimeters were able to provide eye lens HP (3) in each individual interventional procedure,and to monitor the real-time dose rate as well.Conclusions The calibration of HP (3) and the data gained by direct-reading dosimeters are reliable.Therefore,the methods for real-time measurement of eye lens dose for occupational staff in interventional procedures are successfully established.

Thermally stimulated luminescence glow curve structure of ß-irradiated CaB4O7:Dy.

Thermally stimulated luminescence glow curves of CaB4O7:Dy samples after ß-irradiation showed glow peaks at ~335, 530 and 675 K, with a heating rate of 2 K/s. The main peak at 530 K was analyzed using the Tmax-Tstop method and was found to be composed of at least five overlapping glow peaks. A curve-fitting program was used to perform computerized glow curve deconvolution (CGCD) analysis of the complex peak of the dosimetric material of interest. The kinetic parameters, namely activation energy (E) and frequency factor (s), associated with the main glow peak of CaB4O7:Dy at 520 K were evaluated using peak shape (PS) and isothermal luminescence decay (ILD) methods. In addition, the kinetics was determined to be first order (b =1) by applying the additive dose method. The activation energies and frequency factors obtained using PS and ILD methods are calculated to be 0.72 and 0.72 eV and 8.76 × 10(5) and 1.44 × 10(6) /s, respectively.

Monitoring of radiation dose to medical staff during 125I seeds loading / 中华放射医学与防护杂志

Objective To analyze the dose of radiation to medical staff during 125I seeds loading Methods The radiation dose at different distances was measured by using thermoluminescence dosimeters (TLD),and the safe range for medical person was calculated.The doses and annual accumualive doses to the medical staff were estimated.Results The dose attenuation rates were 77.61％,98.04％,98.79％,99.30％,99.71％ and 100％ at distance of 10,20,30,40,50 and 100 cm from seeds tank,respectively.The dose to fingertips,chest,lens and thyroid of doctor were 51.08,35.50,34.73 and 33.78 μGy,and the annual dose reached 12.77,8.88,8.68 and 8.45 mGy when the number of annual operations was 250.The attenuation rate was 79.60％ and 28.36％ of inside and outside lead glass,respectively.Conclusions The radiation is undetectable at 100 cm away from seeds tank in the process of loading of 125I seeds,and lead glass is necessary for radiation protection.