Radiophotoluminescent Glass Research Articles

Response of a Radiophotoluminescence Glass Dosimeter to Low Energy X-rays Necessary for Mammography

Response of a Radiophotoluminescence Glass Dosimeter to Low Energy X-rays Necessary for Mammography

Clinical application of radiophotoluminescent glass dosimeter for dose verification of prostate HDR procedure

High dose rate brachytherapy (HDR-BT) is one of the many modalities for prostate cancer treatment. Due to the nature of HDR-BT, in vivo dosimetry is feasible and can be used to verify consistent dose delivery. In order to validate a dose verification system for HDR-BT prostate cancer treatment, a radiophotoluminescent glass dosimeter (RPLGD) was used and the measurements were compared with those from a thermoluminescent dosimeter. The RPLGD shows many advantages in HDR-BT dose measurement, such as repeatability, stability, and small effective size. These advantages make the RPLGD a superior option for use as a dosimeter in HDR-BT. The results described here show that the difference between the measured dose and the treatment planned dose is less than 5%. A Monte Carlo simulation for the dose was performed using Monte Carlo N -particle to investigate position error. This study concludes that the RPLGD is a promising and reliable dosimeter for HDR-BT in vivo dosimetry with clinically acceptable accuracy.

Dosimertry characteristics and performance comparisons: Environmental radiophotoluminescent glass dosemeters versus thermoluminescent dosemeters

This paper describes the dosimetry characteristic comparison of environmental radiophotoluminescent glass dosemeter (RPLGD) and thermoluminescent dosemeter (TLD) systems employed at the Institute of Nuclear Energy Research (INER, Taiwan). The luminescence centers of TLD disappeared by reading process, and repetition of measurement is impossible. RPLGDs can be repeatedly read and keep the luminescence centers for a long time. The RPLGD fading is about 1% within 30 days after being exposed to ionizing radiation. Environmental cumulative doses measured by a RPLGD and a TLD were compared at the same monitoring points of INER during two years. The sensitivity of TLD decreased with gradual loss due to fading at higher temperatures. The difference between results obtained by RPLGD and TLD is discussed mainly with respect to the dependence on the ambient temperature. In addition, this research also refers to the American National Standard Institute (ANSI) Draft Standard N13.29 (1996) to organize the environmental dosimetry performance tests of the INER's RPLGDs and the TLDs. The results mean that both kinds of dosemeters can meet the performance test criteria. An accreditation procedure for the institutes which provide the environmental dosimetry services in Taiwan was suggested based on the comparison results of these two dosimetry systems.

A comparison of the dosimetric characteristics of a glass rod dosimeter and a thermoluminescent dosimeter for mailed dosimeter

A radiophotoluminescent glass rod dosimeter (RPL-GRD) system has recently become commercially available. The purpose of this study was to investigate the dosimetric characteristics (reproducibility, linearity, fading, energy dependence and angular dependence) of the RPL-GRD for a mailed dosimeter and to compare it with LiF-TLD powder. In this study, the model GD-301 GRD and TLD-700 were powder type used. All measurements with the exception of angular dependence were performed in a water phantom using a holder stand. The RPL-GRD has better reproducibility than the TLD for the Co-60 beam as well as for the clinical photon beam. The RPL-GRD signal was linear as a function of applied dose in the range of 0.5–3 Gy for the Co-60 gamma rays. The fading of the RPL-GRD after a received dose of 2 Gy was initially found to be within 1.7% for five months. The energy dependence of both dosimeters was found to be less than 1.6% for photon beams, but was less than 5.0% for electron beams, which was in agreement with published data. The angular dependence of the RPL-GRD was measured to be approximately 1.4% for angles ranging ±90° from the beam axis using a spherical polystyrene phantom. The measurements comparing RPL-GRD and TLD dosimetric characteristics demonstrated that the RPL-GRD is suitable for mailed dosimetry in a quality assurance (QA) audit program.

Feasibility study of radiophotoluminescent glass rod dosimeter postal dose intercomparison for high energy photon beam

A radiophotoluminescent glass rod dosimeter (GRD) system has recently become commercially available. In this study we evaluated whether the GRD would be suitable for external dosimetric audit program in radiotherapy. For this purpose, we introduced a methodology of the absorbed dose determination with the GRD by establishing calibration coefficient and various correction factors (non-linearity dose response, fading, energy dependence and angular dependence). A feasibility test of the GRD postal dose intercomparison was also performed for eight high photon beams by considering four radiotherapy centers in Korea. In the accuracy evaluation of the GRD dosimetry established in this study, we obtained within 1.5% agreements with the ionization chamber dosimetry for the 60Co beam. It was also observed that, in the feasibility study, all the relative deviations were smaller than 3%. Based on these results, we believe that the new GRD system has considerable potential to be used for a postal dose audit program.

Application of a glass rod detector for the output factor measurement in the CyberKnife

A radiophotoluminescent glass rod detector has recently become commercially available. We evaluated the feasibility of the commercial glass rod as a new detector for measuring output factors in the CyberKnife. The glass rod detector was irradiated in a water phantom using a holder stand, which was specially designed for this study. The holder was composed of a PMMA tube with an attached vertical bar for the glass rod detector. The measured output factors obtained with the glass rod detector were compared with measurements made with a pinpoint ionization chamber, a diode, and a radiochromic film. The measured relative output factors obtained with the glass rod detector agreed with other detectors within 1.0% for collimator sizes larger than 20 mm. However, it was observed that the differences between the output factors measured with the glass rod detector and those obtained with the pinpoint chamber increased rapidly as the collimator size decreased. The relative output factors measured with the diode were consistently higher than those obtained using other detectors for the collimators sizes less than 10 mm in diameter. The glass rod detector results were in good agreement with those obtained from the radiochromic EBT film over the entire range of collimator sizes.

In Vivo Dosimetry of High-Dose-Rate Interstitial Brachytherapy in the Pelvic Region: Use of a Radiophotoluminescence Glass Dosimeter for Measurement of 1004 Points in 66 Patients With Pelvic Malignancy

To perform the largest in vivo dosimetry study for interstitial brachytherapy yet to be undertaken using a new radiophotoluminescence glass dosimeter (RPLGD) in patients with pelvic malignancy and to study the limits of contemporary planning software based on the results. Sixty-six patients with pelvic malignancy were treated with high-dose-rate interstitial brachytherapy, including prostate (n = 26), gynecological (n = 35), and miscellaneous (n = 5). Doses for a total of 1004 points were measured by RPLGDs and calculated with planning software in the following locations: rectum (n = 549), urethra (n = 415), vagina (n = 25), and perineum (n = 15). Compatibility (measured dose/calculated dose) was analyzed according to dosimeter location. The compatibility for all dosimeters was 0.98 +/- 0.23, stratified by location: rectum, 0.99 +/- 0.20; urethra, 0.96 +/- 0.26; vagina, 0.91 +/- 0.08; and perineum, 1.25 +/- 0.32. Deviations between measured and calculated doses for the rectum and urethra were greater than 20%, which is attributable to the independent movements of these organs and the applicators. Missing corrections for inhomogeneity are responsible for the 9% negative shift near the vaginal cylinder (specific gravity = 1.24), whereas neglect of transit dose contributes to the 25% positive shift in the perineal dose. Dose deviation of >20% for nontarget organs should be taken into account in the planning process. Further development of planning software and a real-time dosimetry system are necessary to use the current findings and to achieve adaptive dose delivery.

Development and physical characteristics of a novel compound radiophotoluminescent glass dosimeter

The thermoluminescent dosimeters (TLDs) are widely used for measuring the radiation dose. However, the luminescence centers of TLD disappeared by reading process, and then repetition of measurement is impossible. Radiophotoluminescent glass dosimeters (RPLGDs) can be repeatedly read and keep the luminescence centers for a long time. When machine errors occurred, RPLGD data can be re-analyzed to ensure the reliability of measurement results. Our previous study revealed that the RPLGD is one of the most important radiation dose measurement instruments as compared with TLD. Nevertheless, this RPLGD cannot measure the neutron dose. The aims of this study are to develop the novel compound of RPLGD to detect neutrons, and investigate their physical characteristics. In this study, some series self-fabricated glass dosimeters were prepared from reagent powders of AgCl, AgNO 3 , AgPO 3 , Al ( OH ) 3 , NaPO 3 , Na 2 CO 3 , Na 3 PO 4 and P 2 O 5 . Based on this study, we found that the absorption spectra of irradiated glass wavelength maxima typically occurred in the 300–350 nm. Moreover, 0.1 mol% of sliver consist in our newly developed RPLGD showed the highest gamma ray detection sensitivity. The development of a novel compound RPLGD progress will be continuously improved in our laboratory.

Comparisons of dosimetric properties between GD-300 series of radiophotoluminescent glass detectors and GR-200 series of thermoluminescent detectors

In order to compare the dosimetric properties of two kinds of solid state detectors used for monitoring external exposures, experiments were performed for the GD-300 series of radiophotoluminescent glass detectors (RPLGD) and the GR-200 series of thermoluminescent detectors (TLD). X-rays and 137Cs and 60Co γ-rays were used to irradiate the RPLGDs and TLDs, their dose linearity, uniformity/reproducibility of signal, fading effect and energy dependence were compared. Both kinds of the detectors have generally good dosimetric properties. The dose linearity and energy dependence of the GD-351 dosimeters and the TLDs are nearly the same, but the RPLGD is much better than the TLD in terms of the uniformity and fading effect.

X-ray microbeam measurement with radiophotoluminescent glass plate for single cell irradiation

A commercially available radiophotoluminescent (RPL) glass dosimeter was used for the profile measurement of an X-ray microbeam. The X-ray microbeam of 10 μ m diameter was produced by a microfocus X-ray tube and a glass capillary. An RPL glass plate of 1 mm thickness was irradiated with the X-ray microbeam. After the irradiation, the RPL image for the X-ray microbeam on the glass plate was observed with a conventional fluorescence microscope. In the RPL image analysis, the RPL photons around 600 nm wavelength were detected by exposure to UV photons in the wavelength range from 330 to 380 nm. The profile of the X-ray microbeam was well measured with the RPL glass dosimeter and the RPL intensity was proportional to the X-ray fluence. Normal human fibroblasts cells, AG01522B, were grown on the RPL glass plate for single cell irradiation. A pre-selected living cell was irradiated by the X-ray microbeam and the absorbed dose was estimated to be about 3 Gy. After the irradiation, the targeting cell was stained with anti- γ -H2AX antibody, Alexa Fluor ® 488 and propidium iodide, to visualize the effects on DNA double strand breaks in the nucleus of the cell. In fluorescence microscopy, foci in the nucleus corresponding to the phosphorylation of serine 139 of H2AX and the X-ray beam spot were simultaneously observed at the position of the targeting cell.

Characterisation of radiophotoluminescent dosimeters for environmental monitoring

Solid state dosimetry systems, including the early radiophotoluminescent (RPL) glass dosimeters, were investigated for application in environmental monitoring. RPL systems are under permanent development. The following dosimetric characteristics of the recently developed SC-1 flat RPL glass dosimeters with FGD-202 reader for environmental dosimetry were investigated: uniformity/batch homogeneity, reproducibility, linearity, detection threshold, energy dependence in air, on phantom and in water as well as the light sensitivity. All characteristics investigated fulfil the requirements of the IEC 61066:2006 Standard for personal and environmental dosimetry [IEC, International Electrotechnical Commission, 2006. Thermoluminescence dosimetry systems for personal and environmental monitoring. CEI/IEC International Standard 61066:2006]. It was found, that while the dosimeter is not sensitive for light because of automatic manipulation, the glass element itself could be used for 254 nm UV irradiation measurement. The UV light sensitivity differs for unirradiated and irradiated glass element. The authors recommend to extend the IEC Standard for personal and environmental monitoring also for RPL (and other) passive solid state dosimeters.

Response of radiophotoluminescent dosimeters to neutrons

Radiophotoluminescent (RPL) glass dosimeter type SC-1 has been studied with respect to use it as a photon dosimeter in mixed neutron + gamma fields. SC-1 is composed of the flat glass element placed in a plastic capsule. Energy compensation tin filters to all directions shield the glass card in the capsule. This type of dosimeter was primarily designed for the measurements of photon dose and for use in environmental monitoring around nuclear plants and for accident dosimetry. For a gamma dosimeter to be useful in a mixed neutron + gamma field it is desirable that the neutron sensitivity is small and accurately known. The response has been characterized for 14.5 MeV neutrons, 238Pu–Be spectra and thermal neutrons. The results show that the plastic holder has an influence to the response. The comparison with TLD-700 shows lower responses for neutrons for all spectra investigated. The relative low neutron sensitivity of RPL dosimeter type SC-1 enables its use for photon dosimetry in the mixed neutron + gamma fields.

5510 POSTER Heparanase expression in the differentiation of follicular thyroid lesions: from laboratory to clinical practice

A radiophotoluminescent glass rod detector has recently become commercially available. We evaluated the feasibility of the commercial glass rod as a new detector for measuring output factors in the CyberKnife. The glass rod detector was irradiated in a water phantom using a holder stand, which was specially designed for this study. The holder was composed of a PMMA tube with an attached vertical bar for the glass rod detector. The measured output factors obtained with the glass rod detector were compared with measurements made with a pinpoint ionization chamber, a diode, and a radiochromic film. The measured relative output factors obtained with the glass rod detector agreed with other detectors within 1.0% for collimator sizes larger than 20 mm. However, it was observed that the differences between the output factors measured with the glass rod detector and those obtained with the pinpoint chamber increased rapidly as the collimator size decreased. The relative output factors measured with the diode were consistently higher than those obtained using other detectors for the collimators sizes less than 10 mm in diameter. The glass rod detector results were in good agreement with those obtained from the radiochromic EBT film over the entire range of collimator sizes.

SU-FF-T-179: Dosimetric Evaluation of Radiophotoluminescent Glass Rod Detector; Measurement of Output Factors in Water for Cyberknife Stereotactic Radiosurgery System

Purpose: To evaluate the feasibility of the radiophotoluminescent glass rod detector (GRD) as a new dosimeter for measurement of the output factor in water for Cyberknife SRS system. Method and Materials: In this study, GRD‐301 glass rod dosimeter and FGD‐1000 automatic reader are used. The output factor measurements with the GRD were compared with those with a PTW 60008 p‐type silicon diode detector, PTW 31006 pinpoint chamber and a Gafchromic film (Type MD‐55). The output measured with GRD, pinpoint chamber and diode was performed at a depth of 1.5 cm in water phantom. The GRD was irradiated in a water phantom using a holder stand, which was custom designed for this study. The holder is composed of the PMMA tube with a hole for GRD at 1.5 cm from its top. The center of the GRD was set to be the center of the radiation field by aligning with a point laser built into the LINAC. The film was placed at the depth in the polystyrene phantom at which the maximum dose was achieved. Results: The measured output factors with four dosimeters show very similar results except for three smallest collimators (5, 7.5 and 10 mm). The mean value of the output factor for GRD in the 5 mm collimator is 0.705. The pinpoint chamber output is approximately 11% lower than the corresponding GRD values at the 5 mm collimator. The GRD output is 11% and 4.1% lower than pinpoint chamber and diode, respectively. The GRD results were in good agreement with those from the Gafchromic film for almost all the collimators.Conclusion: The GRD represented a high accuracy dosimeter for small field dosimetry. Future study will be devoted to investigate for possibility of using GRD for quality assurance audit program of stereotactic radiosurgery units.

Synthesis and physical characteristics of radiophotoluminescent glass dosimeters

The radiophotoluminescent glass dosimeter (RPLGD) was developed in the late 1950s while the reading technology was not sensitive enough to measure the low radiation dose and glass element sensitivity to radiation was also quite low. In recent years, the development of the pulsed UV laser excitation method which has high measurement accuracy was applied to the RPLGD. In comparison with the thermoluminescent dosimeter, the advantages of the RPLGD are good reproducibility of readout values, long stability, low energy dependence, better dose linearity and capability of repeatable readouts. It could be one of the most important radiation dose measurement instruments in the near future. Hence, some important physical characteristics of glass dosimeters including reproducibility of readout values, dose linearity, accumulative dose measurement, energy dependence and angular dependence were explored. In this study, four series of glass dosimeters were prepared from reagent powders of Na 3 PO 4 , Na 2 CO 3 , Al ( OH ) 3 , AgCl, and P 2 O 3 . It is necessary to develop the novel compound of RPLGD to measure radiation dose.

Comparison on characteristics of radiophotoluminescent glass dosemeters and thermoluminescent dosemeters

The radiophotoluminescent glass dosemeter (RPLGD) system is applicable for measurement of radiation dose of X rays and gamma rays by using radiophotoluminescent glass (silver-activated phosphate glass). When the radiophotoluminescent glass is exposed to ionizing radiation, stable luminescent centres are created. During pulsed ultraviolet laser excitation (337.1 nm) in the reader, the centres emit a radiation induced orange fluorescent light (600-700 nm). This phenomenon is called radiophotoluminescence. This study compared the RPLGD system with lithium fluoride (LiF) thermoluminescence dosimetry system and the results of the study revealed that the RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments.

A radiophotoluminescent glass plate system for medium-sized field dosimetry

A two-dimensional radiophotoluminescent system for medium-sized field dosimetry has been developed using a silver-activated phosphate glass plate with a dimension of 120mm×120mm×1mm and a readout unit comprising a UV excitation lamp and a CCD imager. A dose ranging from 0 to 400 cGy, provided by a 6 MV x-ray beam, was delivered to the glass plate oriented perpendicularly to the beam and positioned in a water phantom at a depth of 10 cm, where the center of the glass plate coincided with the linac isocenter. After the dose delivery, the glass plate was placed in the readout system. The CCD output intensity increased linearly with the applied dose. The angular dependence of response on the direction of radiation incidence was measured by rotating the glass plate in the water phantom, indicating that the output remained constant up to 75° from perpendicular incident direction, followed by a steep reduction down to 85% at an angle of 90°. A lateral dose distribution resulting from a 60mm×60mm irradiation was compared between the glass plate and an x-ray film having had the same exposure, showing that the glass plate and the x-ray film led to identical dose distributions. The dose reproducibility for a glass plate and the sensitivity variation among different glass plates were also evaluated.

Application of a radiophotoluminescent glass plate dosimeter for small field dosimetry

We have recently developed a prototypical radiophotoluminescent glass plate dosimeter (GPD) system as a device for small field dosimetry. The purpose of this study is to examine the usefulness of the GPD system for small field dosimetry. The profiles measured with the GPD were evaluated by comparing them to those from Kodak X-Omat V and GAFCROMIC XR type R film dosimeters for 2, 5, 9, and 15 mm circular collimators created by a linear accelerator-based radiosurgery system. The GPD output factors were compared with those of various detectors including an ion chamber, a p-type silicon diode detector, a glass rod dosimeter (GRD), and a diamond detector. The results measured with the GPD were also confirmed by comparing them to those from Monte Carlo simulations. The accuracy of a simulated beam is validated by the excellent agreement between Monte Carlo calculated and measured central axis depth-dose curves for 9- and 15 mm circular collimators using 4- and 10 MV photon beams. The GPD profiles show almost the same full width at half maximum as those of film dosimeters and Monte Carlo simulations at 4- and 10 MV photon beams, but a little narrower penumbrae than the film dosimeters and Monte Carlo simulations. The output factors measured with the GPD are in good agreement with those from a diode detector, a diamond detector, and the GRD with a small active volume and Monte Carlo simulations, except for a very small 2 mm circular collimator. It was found that the GPD is a very useful detector for small field dosimetry.

In vivo dosimetry of high-dose-rate brachytherapy: Study on 61 head-and-neck cancer patients using radiophotoluminescence glass dosimeter

The largest in vivo dosimetry study for interstitial brachytherapy yet examined was performed using new radiophotoluminescence glass dosimeters (RPLGDs). Based on the results, a dose prescription technique achieving high reproducibility and eliminating large hyperdose sleeves was studied. For 61 head-and-neck cancer patients who underwent high-dose-rate interstitial brachytherapy, new RPLGDs were used for an in vivo study. The Paris System was used for implant. An arbitrary isodose surface was selected for dose prescription. Locations of 83 dosimeters were categorized as on target (n = 52) or on nontarget organ (n = 31) and were also scaled according to % basal dose isodose surface (% BDIS). Compatibility (measured dose/calculated dose) was analyzed according to location. The hyperdose sleeve was assessed in terms of prescription surface expressed in % BDIS. The spread of compatibilities was larger for on nontarget organ (1.06 +/- 0.32) than for on target (0.87 +/- 0.17, p = 0.01). Within on target RPLGDs, compatibility on <95% BDIS (0.95 +/- 0.10) was better than on > or =95% BDIS (0.84 +/- 0.18, p = 0.02). The number of patients with diameter of hyperdose sleeve > or =10 mm was increased with a dose prescription to <77% BDIS (p = 0.046). For nontarget organs, the maximal positive deviation was 84% of the calculated dose. Dose prescription is recommended to >77% and <95% BDIS for reproducibility and elimination of excessive hyperdose sleeve. For organs at risk, radioprotection should be considered even when calculated dose seems sufficiently low. Further development of planning software is necessary to prevent overestimation.

電子式積算線量計を放射線監視に適用した場合の測定誤差

An electronic dosimeter can be substituted for thermoluminescent dosimeters (TLDs) and radiophoto-luminescence glass dosimeters (RLPDs) in environmental radiation measurements. The dosimeter used here can record the time variation of the dose. Not only the integrated dose, but also the change of the dose rate can be grasped by means of the dosimeter. The measurement error of the dosimeters was examined. The instrumental error is small, being less than 4%. The systematic sensitivity difference was not recognized. The measurement error of 1μSv, which is the minimum dose for unit recording, was around 9%. At an integrated dose of 15μSv, the measurement error was less than 5%. Therefore, highly precise radiation monitoring is possible without checking individual sensitivity. The lower limit dose for detection, which can judge whether the dose exceeds the background, was 0.21μSv through integrating 1μSv. When irradiation was conducted at 1.05μSv/h for 2h, the data was obtained for an approximate time of irradiation as well as the total dose. The dosimeter is suitable for radiation monitoring around X-ray generators or accelerators, where radiation is generated intermittently.