Glass Rod Dosimeter Research Articles

Erratum to: A metallic buildup cap for glass rod dosimeters in radiotherapeutic in vivo dosimetry

Erratum to: A metallic buildup cap for glass rod dosimeters in radiotherapeutic in vivo dosimetry

A metallic buildup cap for glass rod dosimeters in radiotherapeutic in vivo dosimetry

In vivo measurement of radiotherapeutic doses is an important procedure for ensuring the accuracy of radiation treatments. The glass rod dosimeter is a known dosimeter for in vivo dosimetry, which has high reproducibility and low dependencies with respect to major radiotherapeutic conditions. A hemispherical buildup cap made of brass was fabricated to avoid a large measurement error owing to the partial lack of buildup effect during the measurement on the patient's skin. The correction factors (CFs) were experimentally obtained and verified using a Monte Carlo simulation. A clinical trial was performed with 117 patients. As a result, the measured CF was consistent with the simulation by a 2.3% error, and the mean errors of each site were within 2%. The total mean error was 1.84%, with a standard deviation of 1.39%. To conclude, this methodology can provide high accuracy and convenience in radiotherapeutic in vivo measurements.

Observation of morphological abnormalities in silkworm pupae after feeding 137CsCl-supplemented diet to evaluate the effects of low dose-rate exposure

Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, morphological abnormalities in lepidopteran insects, such as shrinkage and/or aberration of wings, have been reported. Butterflies experimentally exposed to radiocesium also show such abnormalities. However, because of a lack of data on absorbed dose and dose–effect relationship, it is unclear whether these abnormalities are caused directly by radiation. We conducted a low dose-rate exposure experiment in silkworms reared from egg to fully developed larvae on a 137CsCl-supplemented artificial diet and estimated the absorbed dose to evaluate morphological abnormalities in pupal wings. We used 137CsCl at 1.3 × 103 Bq/g fresh weight to simulate 137Cs contamination around the FDNPP. Absorbed doses were estimated using a glass rod dosimeter and Monte Carlo particle transport simulation code PHITS. Average external absorbed doses were approximately 0.24 (on diet) and 0.016 mGy/day (near diet); the average internal absorbed dose was approximately 0.82 mGy/day. Pupal wing structure is sensitive to radiation exposure. However, no significant differences were observed in the wing-to-whole body ratio of pupae between the 137CsCl-exposure and control groups. These results suggest that silkworms are insensitive to low dose-rate exposure due to chronic ingestion of high 137Cs at a high concentration.

Experimental Study of In-vivo Dosimetry Using Glass Rod Dosimeters to Minimize the Initialization

In-vivo dosimetry, in which small detector elements are attached to a patient’s body, is an important technique for directly evaluating radiation treatment doses. The glass rod dosimeter (GRD) possesses several advantages over alternatives, which makes it one of the most useful detectors for in-vivo dosimetry. However, because the GRD initialization process requires a prolonged exposure at very high temperatures, as well as subsequent gradual quenching, each measurement takes approximately a day to complete. Therefore, we investigated the reliability of a GRD used repeatedly without initialization processes to improve efficiency. Ten doses of 0.5 Gy were delivered and read using three GRD elements. Then, the same procedure was performed for doses of 1.0 Gy. A readout error of less than 2% was maintained for up to three irradiation doses. However, the fluctuations in the readout data increased significantly as the number of irradiation doses increased. In addition, we discovered that the combined uncertainty of the readouts was influenced more heavily by the cumulative amount of irradiation than it was by the number of doses. Our results should provide guidance for accurate and efficient GRD use.

Secondary cancer-incidence risk estimates for external radiotherapy and high-dose-rate brachytherapy in cervical cancer: phantom study.

This study was designed to estimate radiation‐induced secondary cancer risks from high‐dose‐rate (HDR) brachytherapy and external radiotherapy for patients with cervical cancer based on measurements of doses absorbed by various organs. Organ doses from HDR brachytherapy and external radiotherapy were measured using glass rod dosimeters. Doses to out‐of‐field organs were measured at various locations inside an anthropomorphic phantom. Brachytherapy‐associated organ doses were measured using a specialized phantom that enabled applicator insertion, with the pelvis portion of the existing anthropomorphic phantom replaced by this new phantom. Measured organ doses were used to calculate secondary cancer risk based on Biological Effects of Ionizing Radiation (BEIR) VII models. In both treatment modalities, organ doses per prescribed dose (PD) mostly depended on the distance between organs. The locations showing the highest and lowest doses were the right kidney (external radiotherapy: 215.2 mGy; brachytherapy: 655.17 mGy) and the brain (external radiotherapy: 15.82 mGy; brachytherapy: 2.49 mGy), respectively. Organ doses to nearby regions were higher for brachytherapy than for external beam therapy, whereas organ doses to distant regions were higher for external beam therapy. Organ doses to distant treatment regions in external radiotherapy were due primarily to out‐of‐field radiation resulting from scattering and leakage in the gantry head. For brachytherapy, the highest estimated lifetime attributable risk per 100,000 population was to the stomach (88.6), whereas the lowest risks were to the brain (0.4) and eye (0.4); for external radiotherapy, the highest and lowest risks were to the thyroid (305.1) and brain (2.4). These results may help provide a database on the impact of radiotherapy‐induced secondary cancer incidence during cervical cancer treatment, as well as suggest further research on strategies to counteract the risks of radiotherapy‐associated secondary malignancies.PACS number(s): 87.52.‐g, 87.52.Px, 87.53.Dq, 87.53.Jw

Validation of fluence-based 3D IMRT dose reconstruction on a heterogeneous anthropomorphic phantom using Monte Carlo simulation.

In this study, we evaluated the performance of a three‐dimensional (3D) dose verification system, COMPASS version 3, which has a dedicated beam models and dose calculation engine. It was possible to reconstruct the 3D dose distributions in patient anatomy based on the measured fluence using the MatriXX 2D array. The COMPASS system was compared with Monte Carlo simulation (MC), glass rod dosimeter (GRD), and 3DVH, using an anthropomorphic phantom for intensity‐modulated radiation therapy (IMRT) dose verification in clinical neck cases. The GRD measurements agreed with the MC within 5% at most measurement points. In addition, most points for COMPASS and 3DVH also agreed with the MC within 5%. The COMPASS system showed better results than 3DVH for dose profiles due to individual adjustments, such as beam modeling for each linac. Regarding the dose‐volume histograms, there were no large differences between MC, analytical anisotropic algorithm (AAA) in Eclipse treatment planning system (TPS), 3DVH, and the COMPASS system. However, AAA underestimated the dose to the clinical target volume and Rt‐Parotid slightly. This is because AAA has some problems with dose calculation accuracy. Our results indicated that the COMPASS system offers highly accurate 3D dose calculation for clinical IMRT quality assurance. Also, the COMPASS system will be useful as a commissioning tool in routine clinical practice for TPS.PACS number: 87.55.Qr, 87.56.Fc, 87.61.Bj

A dosimetry method for low dose rate brachytherapy by EGS5 combined with regression to reflect source strength shortage

The post-implantation dosimetry for brachytherapy using Monte Carlo calculation by EGS5 code combined with the source strength regression was investigated with respect to its validity. In this method, the source strength for the EGS5 calculation was adjusted with the regression, so that the calculation would reproduce the dose monitored with the glass rod dosimeters (GRDs) on a water phantom. The experiments were performed, simulating the case where one of two 125I sources of Oncoseed 6711 was lacking strength by 4–48%. As a result, the calculation without regression was in agreement with the GRD measurement within 26–62%. In this case, the shortage in strength of a source was neglected. By the regression, in order to reflect the strength shortage, the agreement was improved up to 17–24%. This agreement was also comparable with accuracy of the dose calculation for single source geometry reported previously. These results suggest the validity of the dosimetry method proposed in this study.

Reading Deviations of Glass Rod Dosimeters Using Different Pre-processing Methods for Radiotherapeutic in-vivo Dosimetry

†† ‡ ‡ , † ‡ The experimental verification of treatment planning on the treatment spot is the ultimate method to assure quality of radiotherapy, so in-vivo skin dose measurement is the essential procedure to confirm treatment dose. In this study, glass rod dosimeter (GRD), which is a kind of photo-luminescent based dosimeters, was studied to produce a guideline to use GRDs in vivo dosimetry for quality assurance of radiotherapy. The pre-processing procedure is essential to use GRDs. This is a heating operation for stabilization. Two kinds of pre-processing methods are recommended by manufacturer: a heating method (70 degree, 30 minutes) and a waiting method (room temperature, 24 hours). We equally irradiated 1.0 Gy to 20 GRD elements, and then different preprocessing were performed to 10 GRDs each. In heating method, reading deviation of GRDs at same time were relatively high, but the deviation was very low as time went on. In waiting method, the deviation among GRDs was low, but the deviation was relatively high as time went on. The meaningful difference was found between mean reading values of two pre-processing methods. Both methods present mean dose deviation under 5%, but the relatively high effect by reading time was observed in waiting method. Finally, GRD is best to perform in-vivo dosimetry in the viewpoint of accuracy and efficiency, and the understanding of how pre-processing affect the accuracy is asked to perform most accurate in-vivo dosimetry. The further study is asked to acquire more stable accuracy in spite of different irradiation conditions for GRD usage.

Dosimetric properties of radiophotoluminescent glass detector in low‐energy photon beams

A radiophotoluminescent glass rod dosimeter (RGD) has recently become commercially available. It is being increasingly used for dosimetry in radiotherapy to measure the absorbed dose including scattered low-energy photons on the body surface of a patient and for postal dosimetry audit. In this article, the dosimetric properties of the RGD, including energy dependence of the dose response, reproducibly, variation in data obtained by the RGD for each energy, and angular dependence in low-energy photons, are discussed. An RGD (GD-301, Asahi Techno Glass Corporation, Shizuoka, Japan) was irradiated with monochromatic low-energy photon beams generated by synchrotron radiation at Photon Factory, High Energy Accelerator Research Organization (KEK). The size of GD-301 was 1.5 mm in diameter and 8.5 mm in length and the active dose readout volume being 1 mm diameter and 0.6 mm depth located 0.7 mm from the end of the detector. The energy dependence of the dose response and reproducibility and variation were investigated for RGDs irradiated with a plastic holder and those irradiated without the plastic holder. Response of the RGD was obtained by not only conventional single field irradiation but also bilateral irradiation. Angular dependence of the RGD was measured in the range of 0°-90° for 13, 17, 40, and 80 keV photon beams by conventional single field irradiation. The dose responses had a peak at around 40 keV. For the energy range of less than 25 keV, all dose response curves steeply decreased in comparison with the ratio of mass energy absorption coefficient of the RGD to that of air. As for the reproducibility and variation in data obtained by the RGD, the coefficient of variance increased with decrease in photon energy. Furthermore, the variation for bilateral irradiation was less than that for single field irradiation. Regarding angular dependence of the RGD, for energies of 13 and 17 keV, the response decreased with increase in the irradiation angle, and the minimum values were 93.5% and 86%, respectively. Our results showed the dosimetric properties of the RGD, including the energy dependence of the dose response, reproducibly, variation, and angular dependence in low-energy photons and suggest that the accuracy of the absorbed dose in low-energy photons is affected by the readout method and the distribution of radiophotoluminescence centers in the RGD.

Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT

Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

A dosimetry study of the Oncoseed 6711 using glass rod dosimeters and EGS5 Monte Carlo code in a geometry lacking radiation equilibrium scatter conditions

The aim of this study was to develop a dose calculation method which is applicable to the interseed attenuation and the geometry lacking the equilibrium radiation scatter conditions in brachytherapy. The dose obtained from measurement with a radiophotoluminescent glass rod dosimeter (GRD) was compared to the dose calculated with the Monte Carlo (MC) code "EGS5," using the 125I source structure detailed in by Kennedy et al. The GRDs were irradiated with 125I Oncoseed 6711 in a human head phantom. The phantom was a cylinder made of 2 mm thick PMMA with a diameter of 18 cm and length of 16 cm. Some of the GRD positions were so close to the phantom surface that the backscatter margin was less than 5 cm, insufficient for photons. The EGS5 simulations were found to reproduce the relative dose distributions as measured with the GRDs to within 25% uncertainty in the geometry lacking the equilibrium radiation scatter conditions. The absolute value of the GRD measurement agreed with the American Association of Physicist in Medicine Task Group No 43 Updated Protocol (AAPM-TG43U1) formalism to within 3% of the reference point (r = 1 cm, theta = 90 degrees), where the TG43U1 is especially reliable because of the abundant data accumulation in composing the formalism. The factor to normalize the measured or calculated dose to the TG43U1 estimate at the reference point was evaluated to be 0.97 for the GRD measurement and 1.8 for the MC calculation, which uses the integration of the apparent activity with the time as the amount of disintegration during the irradiation. Also, F(r,theta) and g(r) estimated by this calculation method were consistent with those proposed in the TG43U1. The results of this investigation support the validity of both the MC calculation method and GRD measurement in this study as well as the TG-43U1 formalism. Also, this calculation is applicable to interseed attenuation and the geometry lacking the equilibrium radiation scatter.

Radiation exposure of operator performing interventional procedures using a flat panel angiography system: evaluation with photoluminescence glass dosimeters

Using glass rod dosimeters we investigated the radiation dose to the operator performing interventional procedures in 43 patients with the aid of a monoplane flat detector-based angiography system. During the procedures we recorded the number of radiographic frames and the radiographic conditions. After treatment we recorded the fluoroscopy time and the fluoroscopic, radiographic, and total air kerma. To obtain the total operator exposure dose we took measurements at five sites: left orbital fossa, thyroid, left hand, left chest, and pubic symphysis. The mean operator exposure dose to the left hand was higher than at the other sites we measured; it was 387.0, 209.6, 174.3, and 237.1 microGy for the stentgraft, percutaneous transluminal arteriography, transarterial chemoembolization, and hepatic infusion port placement procedures. There was a positive correlation between the fluoroscopic and radiographic air kerma value and the operator exposure dose at the left orbital fossa, thyroid, and left hand. The operator exposure dose correlated with the radiographic and fluoroscopic air kerma. Exposure of the operator's left hand was higher than at the other sites studied.

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.

Measurements of the Relative Output Factors for Radiosurgical CyberKnife Collimators Using a Glass Rod Dosimeter

The purpose of this study was to evaluate the accuracy of a glass rod dosimeter (GRD) for relative output factor measurements in the CyberKnife radiosurgery system. The output factors measured with the GRD were compared to those obtained with an ionization chamber, a diode and a Gafchromic film. The GRD was irradiated in a water phantom using an in-house custom designed holder stand. The relative output factors measured with the four dosimeters showed very similar results for collimator diameters larger than 20 mm. The mean value of the output factors of the GRD for the 5 mm collimator was 0.695. The output factor measured with the ionization chamber was approximately 13.7% lower than the corresponding GRD values for the 5 mm collimator. The diode output factors were 3.1% and 1.9% higher than the GRD for the 5 mm and 7.5 mm collimators, respectively. However, the GRD results were in agreement with the measurements obtained with a Gafchromic film for all of the collimator diameters.

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.

Abdominal CT with Low Tube Voltage: Preliminary Observations about Radiation Dose, Contrast Enhancement, Image Quality, and Noise

To prospectively investigate the effect of low tube voltage on radiation dose, contrast enhancement, image quality, and image noise at abdominal dynamic computed tomography (CT). The institutional review board approved this study. Prior informed consent was obtained from all patients. Forty patients (24 women, 16 men; mean age, 62 years) underwent initial abdominal CT at 120 kV with 100 mL of contrast material (protocol A). Then all patients were randomly assigned to one of two protocols (protocol B, CT at 90 kV with 100 mL contrast material; protocol C, CT at 90 kV with 80 mL contrast material). The CT numbers of their abdominal organs were assessed quantitatively and qualitatively. Statistical analysis was performed by using the two-tailed paired t test, Kruskal-Wallis test, and kappa test of interobserver agreement. The radiation dose was measured with a phantom that consisted of glass-rod dosimeters. Quantitative analysis revealed that protocols B and C yielded significantly better enhancement of the aorta, liver, pancreas, spleen, and kidney than did protocol A (P < .05). With qualitative analysis, the difference among the three protocols in regard to image quality was not significant. At 90 kV versus 120 kV, the radiation dose reduction in the center of the phantom was 56.8% (6.3 vs 14.6 mGy); in the periphery, it was 46.2% (13.6 vs 25.3 mGy). By decreasing the tube voltage, the amount of contrast material can be reduced without image quality degradation. In scans obtained with a low tube voltage, the radiation dose can be reduced as much as 56.8%, and higher contrast material enhancement can be achieved.

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.

Development of a radiophotoluminescent glass plate detector for small field dosimetry

Development of a radiophotoluminescent glass plate detector for small field dosimetry

The application of newly developed glass rod dosimeter in the quality assurance and dosimetric audit of gamma knife

Gamma Knife (GK) is a widely used treatment modality for intra-cranial radiosurgery. The machine is manufactured to a very high precision and is routinely used to treat very small target areas in the vicinity of other eloquent structures e.g. a 4mm target shot for trigeminal neuralgia, where the target abuts the brainstem. The small focal spot at isocenter limits the use of standard dosimetry equipment and to this end we present the use of glass rod dosimeter (GRD) for a variety of GK dose measurements.