Use of Commercially Available Optically Stimulated Luminescence Dosimeter As Extremity Dose Estimator.

In 2009, Idaho National Laboratory (INL) transitioned to an external dosimetry program using optically stimulated luminescent (OSL) technology. This process led to the introduction of the Landauer, Inc., nanoDot dosimeter and MicroStar reader to INL's radiological control program. At the time, a small, self-contained, single chip OSL dosimeter that could be easily read in the field was recognized as having many potential applications for a radiological control program. The ability to achieve a realistic extremity-dose estimate in the field shortly following work where significant exposure is expected is a much sought-after capability at INL. It was proposed to employ the Landauer nanoDot dosimeter as a supplemental extremity monitor as an alternative to time-motion dose analyses based on direct radiation measurements, which had proven to be inaccurate and operationally inefficient. Additionally, this process does not involve the nanoDot in the US Department of Energy Laboratory Accreditation Program (DOELAP) process, which significantly reduces operational complexity. A dose conversion value for the nanoDot dosimeter was derived from direct comparisons with a DOELAP-accredited extremity dosimeter. The geometry or placement of the nanoDot relative to the accredited extremity dosimeter was kept as proximate as possible to best replicate the expected results from the accredited extremity dosimeter. Upon implementation, the nanoDot has proven to be effective in providing reasonable and timely extremity-dose estimates for operational control.

Surface and near-surface dose measurements at beam entry and exit in a 1.5 T MR-Linac using optically stimulated luminescence dosimeters.

The objective of this study is to measure surface and near-surface dose at entry and exit surfaces in a 1.5 T MR-Linac (Elekta AB, Stockholm, Sweden) using optically stimulated luminescence dosimeters (OSLDs). OSLDs were expected to be useful for measuring surface dose in a strong magnetic field because they can be taped to undersides to measure exit dose, and their dose response have been shown to be reasonably insensitive to variations in beam angle, beam energy, and magnetic fields. The surface and near-surface dose at the entry and exit of a 20 cm thick solid water phantom was measured with OSLDs for 5 × 5, 10 × 10, and 22 × 22 cm2 field sizes. The solid water phantom was elevated off the couch top to produce an air gap of 3.7 cm so as to observe the electron return effect (ERE) near the beam exit surface. Measurement depths ranged from surface to 15 mm deep from entry and exit surfaces. The phantom dose distribution was also computed in the Monaco (Elekta AB, Stockholm, Sweden) Monte Carlo treatment planning system (TPS). For the 5 × 5, 10 × 10, and 22 × 22 cm2 field sizes the surface dose at depth 0 mm was extrapolated from OSLD measurements to be 10.9%, 12.0%, and 13.5%. The surface entry dose was found to be far less field size-dependent compared to a conventional linac, likely due to a lack of electronic contamination due to the strong magnetic field perpendicular to the beam. The ERE effect was observed in the measurements near the exit surface of the phantom, and was in close agreement with the TPS calculation.

CHARACTERISATION AND EVALUATION OF AL2O3:C-BASED OPTICALLY STIMULATED LUMINESCENT DOSEMETER SYSTEM FOR DIAGNOSTIC X-RAYS: PERSONAL AND IN VIVO DOSIMETRY.

This study characterises and evaluates an Al2O3:C-based optically stimulated luminescent dosemeter (OSLD) system, commercially known as the nanoDot™ dosemeter and the InLight® microStar reader, for personal and in vivo dose measurements in diagnostic radiology. The system characteristics, such as dose linearity, reader accuracy, reproducibility, batch homogeneity, energy dependence and signal stability, were explored. The suitability of the nanoDot™ dosemeters was evaluated by measuring the depth dose curve, in vivo dose measurement and image perturbation. The nanoDot™ dosemeters were observed to produce a linear dose with ±2.8% coefficient variation. Significant batch inhomogeneity (8.3%) was observed. A slight energy dependence (±6.1%) was observed between 60 and 140 kVp. The InLight® microStar reader demonstrated good accuracy and a reproducibility of ±2%. The depth dose curve measured using nanoDot™ dosemeters showed slightly lower responses than Monte Carlo simulation results. The total uncertainty for a single dose measurement using this system was 11%, but it could be reduced to 9.2% when energy dependence correction was applied.

MCP-based detectors: calibration and first photon radiation measurements.

Detectors based on microchannel plates (MCPs) are used to detect radiation from free-electron lasers. Three MCP detectors have been developed by JINR for the European XFEL (SASE1, SASE2 and SASE3 lines). These detectors are designed to operate in a wide dynamic range from the level of spontaneous emission to the SASE saturation level (between a few nJ up to 25 mJ), in a wide wavelength range from 0.05 nm to 0.4 nm for SASE1 and SASE2, and from 0.4 nm to 4.43 nm for SASE3. The detectors measure photon pulse energies with an anode and a photodiode. The photon beam image is observed with an MCP imager with a phosphor screen. At present, the SASE1 and SASE3 MCP detectors are commissioned with XFEL beams. Calibration and first measurements of photon radiation in multibunch mode are performed with the SASE1 and SASE3 MCPs. The MCP detector for SASE2 and its electronics are installed in the XFEL tunnel, technically commissioned, and are now ready for acceptance tests with the X-ray beam.

OPTICALLY STIMULATED LUMINESCENCE OF LiF:Mg,Cu,P POWDER-INFLUENCE OF THERMAL TREATMENT.

It was recently found that LiF:Mg,Cu,P, which is a very well-known thermoluminescent (TL) material, exhibits also quite substantial optically stimulated luminescence (OSL). In the present work a study on the influence of thermal treatment on the LiF:Mg,Cu,P OSL intensity has been performed. The results revealed that the well-known 'gold standard' of 240°C annealing is not appropriate for OSL measurements. The annealing at lower temperatures produced significantly higher OSL intensity. The highest enhancement of the OSL signal, reaching 95% (compared to the initial signal after standard annealing at 240°C/10 min) was obtained after annealing at about 190-200°C/30 min. The OSL emission spectrum of LiF:Mg,Cu,P was also measured and found to be peaked at 360 nm.

Response of TL and OSL passive personal dosimetry systems in poly-energetic and multi-directional photon radiation fields.

The aim of this paper is to examine the energy and angular responses of thermoluminescent dosimeters containing either MTS-N (LiF:Mg,Ti) or MCP-N (LiF:Mg,Cu,P) detector materials, and of the InLight optically stimulated luminescent dosimeters containing Al2O3:C detectors. Ten radiation qualities, with mean energies ranging from 24 keV to 1.25 MeV, and five angles of incidence, between 0° and 80°, were used for this purpose. The dosimeter response measure of quality were the IEC 62387 requirements. The experimental results show that the MTS-N-based and the InLight dosimeters performed in line with the standard's criteria. On the other hand, the MCP-N-based dosimeters exhibited a pronounced under-response around the energy of 120 keV, which resulted in deviations from the standard's conditions for both the energy and angular responses.

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

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 × 15 mm [Formula: see text]) 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 (4.9% 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.

Radiation dose measurements in a dental orthopantogram unit using indigenously developed optically stimulated luminescence dosimeters.

Dental orthopantogram (OPG)/cone beam computed tomography (CBCT) scanners are gaining popularity due to their 3D imaging with multiplanar view that provides clinical benefits over conventional dental radiography systems. Dental OPG/CBCT provides optimal visualization of adjacent overlaying anatomical structures that will be superpositioned in any single projection. The characteristics of indigenously developed optically stimulated luminescence dosimeters, namely, aluminium oxide doped with carbon (Al2 O3 :C), lithium magnesium phosphate doped with terbium and boron (LiMgPO4 :Tb,B) and lithium calcium aluminium fluoride doped with europium and yttrium (LiCaAlF6 :Eu,Y) were evaluated for their use in dental dosimetry. The dose-response of these dosimeters was studied at X-ray energies 60 kV, 70 kV and 81 kV. Radiation doses were also measured using Gafchromic film for comparison. Radiation dose was measured at eight different locations of a polymethyl methacrylate (PMMA) head phantom including eyes. The optically stimulated luminescence (OSL) sensitivity of LiMgPO4 :Tb,B is about 1.5 times and LiCaAlF6 :Eu, is about 20 times higher than the sensitivity of Al2 O3 :C. It was found that measured radiation doses by the three optically stimulated luminescence dosimeters (OSLDs) and Gafchromic film in the occipital region (back side) of a PMMA phantom, were consistent but variations in dose at other locations were significantly higher. The three OSLDs used in this study were found to be suitable for radiation dose measurement in dental units.

Calibration and Statistical Performance of Al2O3: C Optically Stimulated Luminescent Dosimeters With and Without Annealing Using a 137Cs Source.

A series of experiments were conducted using commercially available Al2O3:C optically stimulated luminescent dosimeters to provide a technical basis for their precise calibration and statistical performance at irradiated air kerma doses between 0.02 mGy and 5 mGy using Cs. This study examines the dose response linearity, studies the background signal for annealed dosimeters, and compares the statistical performance of dosimeters that were annealed and not annealed prior to their irradiation and readout. The average and standard deviation for the response of groups of dosimeters annealed and nonannealed prior to their irradiation were determined at each delivered dose. The batch of dosimeters that were annealed prior to their irradiation exhibited a coefficient of variation in its mean dose response below 10% when using three or more irradiation trials at each delivered air kerma dose between 0.02 mGy and 5 mGy. The reader calibration factor was calculated using the response of the annealed batch of dosimeters and was determined to be 756 ± 7 photomultiplier tube counts per mGy. Best estimates of the individual sensitivity factors were determined to be between 0.79 and 1.12 for the annealed batch of dosimeters. The minimum number of irradiations required to accurately determine the sensitivity factor of each individual dosimeter is reported with the recommended reader and dosimeter calibration procedures.

Calibration strategies for use of the nanoDot OSLD in CT applications.

Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor-provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60 Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer-type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80-140 kVp, and with measurements at a range of positions). When calibrated using the vendor-recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor-provided calibration approach. These techniques provide high precision for OSLD-based measurements in a CT environment.

OSL PROPERTIES IN VARIOUS FORMS OF KCl AND NaCl SAMPLES AFTER EXPOSURE TO IONIZING RADIATION.

The aim of this work was to investigate the optically-stimulated luminescence (OSL) properties of potassium chloride (KCl) and its potential use in radiation dosimetry. The optimal condition for OSL readout with blue light stimulation were designated using a commercially available Risø TL/OSL reader. KCl was studied in three sample forms: crystals, powder and pellets. The following OSL characteristics were determined: signal reproducibility, OSL measurement-induced sensitivity changes, temperature dependence of OSL and signal stability over time. The results show a high reproducibility of KCl samples and strong sensitivity changes, which can be corrected for by using a test-dose. The long-term OSL studies confirmed the occurrence of both inverse fading and fading phenomena in KCl. In addition, a comparison with corresponding measurements using sodium chloride (NaCl) were carried out. Although it was confirmed that NaCl is more suitable for dosimetry, there might be benefits of combining NaCl with KCl for more accurate absorbed dose determinations.

OSL dosimeters for dental panoramic radiography.

The aim of the present work is to determine dosimetric characteristics of commercial optically stimulated luminescence dosimeter (OSLD) to estimate equivalent dose in the patient undergoing panoramic radiography procedure. Digital panoramic unit "Instrumentarium OP200D" was used. OSL dosimeters were optically bleached before any exposure procedure. InLight™ OSL nanodosimeters were placed on the thyroid surface between the head and neck. The exposure parameters for all measurements was standard value consisted in 66 kV, 5 mA, and 14.1 s. Standard size field of view (FOV) scanning mode was used. Dosimeters were calibrated for the air kerma. Reported male adult equivalent doses from 21 to 45 µSv for each scanning for standard size field of view (FOV). Meanwhile reported female adult equivalent doses from 28 to 75 µSv for standard size field of view (FOV) considering all heights. The lowest equivalent dose (21 µSv) was observed in the male thyroid gland surface (S) position for medium height. The highest equivalent dose (75 µSv) was for female small height in the right parotid surface (R) position. In conclusion, the results demonstrate that OSL dosimeters are appropriate in vivo dosimetry system for dental panoramic dose measurements.

CHARACTERIZATION AND PERFORMANCE TESTS OF A NEW OSL/TL PERSONAL DOSEMETER FOR INDIVIDUAL MONITORING.

We propose a personal dosemeter based on the combination of thermoluminescence (TL) and optically stimulated luminescence (OSL) detectors employing the advantages of both techniques. The new OSL/TL dosemeter using a badge manufactured in a 3D printer was tested for assessment of photon doses in simulated and actual situations of exposure. Additionally, Brazilian national performance tests adapted to the new dosemeter were run as well as the performance tests of international standards on the passive dosimetry systems. The results showed the advantages of combined OSL and TL techniques when using the three different configurations of detector combination, Al2O3/BeO, BeO/CaSO4 and Al2O3/LiF. The dosemeter allowed corrections for radiation energy without the necessity of attenuation filters, the evaluation of single and accumulated doses and the triple check of the dose values. Further, the performance tests were consistent with national and international requirements, showing the viability of application of the new dosemeter to the assessment of equivalent doses.

Investigation and Implementation of Commercially Available Optically Stimulated Luminescence Dosimeters for Use in Fixed Nuclear Accident Dosimeter Systems.

Idaho National Laboratory transitioned from an external dosimetry system reliant on thermoluminescent dosimeters to one that uses optically stimulated luminescence dosimeters in 2010. This change not only affected the dosimeters worn by personnel, but those found in the nuclear-accident dosimeters used across Idaho National Laboratory. The elimination of on-site use and processing of thermoluminescent dosimeters impacted Idaho National Laboratory's ability to process nuclear-accident dosimeters in a timely manner. This change in processes drove Idaho National Laboratory to develop an alternative method for fixed nuclear-accident dosimeter gamma-dose analyses. This new method was driven by the need to establish a simple, cost-effective, and rapid-turnaround alternative to the thermoluminescent-dosimeter-based fixed nuclear-accident dosimeter system. An adaptation of existing technologies proved to be the most efficient path to this end. The purpose of this article is to delineate the technical basis for replacing the thermoluminescent dosimeter contained within the Idaho National Laboratory fixed nuclear-accident dosimeter system with optically stimulated luminescence-based Landauer, Inc., nanoDot dosimeters.

Characterization of nanoDot optically stimulated luminescence detectors and high-sensitivity MCP-N thermoluminescent detectors in the 40-300 kVp energy range.

PURPOSE: To investigate empirically the energy dependence of the detector response of two in vivo luminescence detectors, LiF:Mg,Cu,P (MCP-N) high-sensitivity TLDs and Al2 O3 :C OSLDs, in the 40-300-kVp energy range in the context of in vivo surface dose measurement. As these detectors become more prevalent in clinical and preclinical in vivo measurements, knowledge of the variation in the empirical dependence of the measured response of these detectors across a wide spectrum of beam qualities is important. METHOD: We characterized a large range of beam qualities of three different kilovoltage x-ray units: an Xstrahl 300 Orthovoltage unit, a Precision x-Ray X-RAD 320ix biological irradiator, and a Varian On-Board Imaging x-ray unit. The dose to water was measured in air according to the AAPM's Task Group 61 protocol. The OSLDs and TLDs were irradiated under reference conditions on the surface of a water phantom to provide full backscatter conditions. To assess the change in sensitivity in the long term, we separated the in vivo dosimeters of each type into an experimental and a reference group. The experimental dosimeters were irradiated using the kilovoltage x-ray units at each beam quality used in this investigation, while the reference group received a constant 10 cGy irradiation at 6 MV from a Varian clinical linear accelerator. The individual calibration of each detector was verified in cycles where both groups received a 10 cGy irradiation at 6 MV. RESULTS: The nanoDot OSLDs were highly reproducible, with ±1.5% variation in response following >40 measurement cycles. The TLDs lost ~20% of their signal sensitivity over the course of the study. The relative light output per unit dose to water of the MCP-N TLDs did not vary with beam quality for beam qualities with effective energies <50 keV (~150 kVp/6 mm Al). At higher energies, they showed a reduced (~75-85%) light output per unit dose relative to 6 MV x rays. The nanoDot OSLDs exhibited a very strong (120-408%) dependency of the light output relative to 6 MV x rays. Variations up to 15% between different x-ray units with equivalent effective energies were also observed. CONCLUSIONS: While convenient for clinical use, nanoDot OSLDs exhibit a strong variation in their measured light output per unit dose relative to 6 MV in the 40-300 kV x-ray range. This variability differs unit-to-unit, limiting their effective use for in vivo dosimetry applications in the kilovoltage x-ray energy range. MCP-N TLDs offer a much more stable response, but suffer from variations in sensitivity over time dependent on radiation history, which requires careful experimental handling.

An Efficient, Affordable Optically Stimulated Luminescent (OSL) Annealer.

Optically stimulated luminescent (OSL) dosimeters are devices used for measuring doses of ionizing radiation. Signal is stored within an OSL material so that when stimulated with light, light of a specific wavelength is emitted in proportion to the integrated ionizing radiation dose. Each interrogation of the material results in the loss of a small fraction of signal, thus allowing multiple interrogations leading to more accurate measurements of dose. In order to reuse a dosimeter, the residual signals from prior doses must be taken into account and subtracted from current readings, adding uncertainty to any future measurements. To reduce these errors when they become large, it is desirable to completely clear the stored signal or anneal the dosimeter. Traditionally, heating the material has accomplished this. In a commercially available dosimeter badge system, the OSL material Al2O3:C is incorporated into a plastic slide that would melt at the necessary high temperatures, which can reach 900 °C, required for annealing. Fortunately, due to the material's high sensitivity to light, OSLs can be optically annealed instead. In order to do this, an affordable OSL dosimeter annealer was designed with inexpensive, exchangeable blue, green, and white high intensity light-emitting diodes (LEDs). Several dosimeters were repeatedly annealed for recorded intervals and then read out. A single dosimeter was partially annealed through repeated interrogations with the LED array from a commercial reader. The signal loss due to the exposure to each light was analyzed to determine the practicality and efficiency of each color. The rate and extent of signal loss was dependent not only on the spectrum of annealing light but on the initial signal levels as well. These findings suggest that blue LEDs are the most promising for effective and rapid clearing of the OSL material Al2O3:C.

In vivo dosimetry with optically stimulated luminescent dosimeters for conformal and intensity-modulated radiation therapy: A 2-year multicenter cohort study.

PURPOSE: Optically stimulated luminescent dosimeters (OSLDs) are utilized for in vivo dosimetry (IVD) of modern radiation therapy techniques such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Dosimetric precision achieved with conventional techniques may not be attainable. In this work, we measured accuracy and precision for a large sample of clinical OSLD-based IVD measurements. METHODS AND MATERIALS: Weekly IVD measurements were collected from 4 linear accelerators for 2 years and were expressed as percent differences from planned doses. After outlier analysis, 10,224 measurements were grouped in the following way: overall, modality (photons, electrons), treatment technique (3-dimensional [3D] conformal, field-in-field intensity modulation, inverse-planned IMRT, and VMAT), placement location (gantry angle, cardinality, and central axis positioning), and anatomical site (prostate, breast, head and neck, pelvis, lung, rectum and anus, brain, abdomen, esophagus, and bladder). Distributions were modeled via a Gaussian function. Fitting was performed with least squares, and goodness-of-fit was assessed with the coefficient of determination. Model means (µ) and standard deviations (σ) were calculated. Sample means and variances were compared for statistical significance by analysis of variance and the Levene tests (α = 0.05). RESULTS: Overall, µ ± σ was 0.3 ± 10.3%. Precision for electron measurements (6.9%) was significantly better than for photons (10.5%). Precision varied significantly among treatment techniques (P < .0001) with field-in-field lowest (σ = 7.2%) and IMRT and VMAT highest (σ = 11.9% and 13.4%, respectively). Treatment site models with goodness-of-fit greater than 0.90 (6 of 10) yielded accuracy within ±3%, except for head and neck (µ = -3.7%). Precision varied with treatment site (range, 7.3%-13.0%), with breast and head and neck yielding the best and worst precision, respectively. Placement on the central axis of cardinal gantry angles yielded more precise results (σ = 8.5%) compared with other locations (range, 10.5%-11.4%). CONCLUSIONS: Accuracy of ±3% was achievable. Precision ranged from 6.9% to 13.4% depending on modality, technique, and treatment site. Simple, standardized locations may improve IVD precision. These findings may aid development of patient-specific tolerances for OSLD-based IVD.

Image reconstruction algorithm for optically stimulated luminescence 2D dosimetry using laser-scanned Al2O3:C and Al2O3:C,Mg films.

The objective of this work was to develop an image reconstruction algorithm for 2D dosimetry using Al2O3:C and Al2O3:C,Mg optically stimulated luminescence (OSL) films imaged using a laser scanning system. The algorithm takes into account parameters associated with detector properties and the readout system. Pieces of Al2O3:C films (~8 mm × 8 mm × 125 µm) were irradiated and used to simulate dose distributions with extreme dose gradients (zero and non-zero dose regions). The OSLD film pieces were scanned using a custom-built laser-scanning OSL reader and the data obtained were used to develop and demonstrate a dose reconstruction algorithm. The algorithm includes corrections for: (a) galvo hysteresis, (b) photomultiplier tube (PMT) linearity, (c) phosphorescence, (d) 'pixel bleeding' caused by the 35 ms luminescence lifetime of F-centers in Al2O3, (e) geometrical distortion inherent to Galvo scanning system, and (f) position dependence of the light collection efficiency. The algorithm was also applied to 6.0 cm × 6.0 cm × 125 µm or 10.0 cm × 10.0 cm × 125 µm Al2O3:C and Al2O3:C,Mg films exposed to megavoltage x-rays (6 MV) and 12C beams (430 MeV u-1). The results obtained using pieces of irradiated films show the ability of the image reconstruction algorithm to correct for pixel bleeding even in the presence of extremely sharp dose gradients. Corrections for geometric distortion and position dependence of light collection efficiency were shown to minimize characteristic limitations of this system design. We also exemplify the application of the algorithm to more clinically relevant 6 MV x-ray beam and a 12C pencil beam, demonstrating the potential for small field dosimetry. The image reconstruction algorithm described here provides the foundation for laser-scanned OSL applied to 2D dosimetry.

INTEGRATED CIRCUITS FROM MOBILE PHONES AS POSSIBLE EMERGENCY OSL/TL DOSIMETERS.

In this article, optically stimulated luminescence (OSL) data are presented from integrated circuits (ICs) extracted from mobile phones. The purpose is to evaluate the potential of using OSL from components in personal electronic devices such as smart phones as a means of emergency dosimetry in the event of a large-scale radiological incident. ICs were extracted from five different makes and models of mobile phone. Sample preparation procedures are described, and OSL from the IC samples following irradiation using a (90)Sr/(90)Y source is presented. Repeatability, sensitivity, dose responses, minimum measureable doses, stability and fading data were examined and are described. A protocol for measuring absorbed dose is presented, and it was concluded that OSL from these components is a viable method for assessing dose in the days following a radiological incident.

Evaluation of an X-Ray Dose Profile Derived from an Optically Stimulated Luminescent Dosimeter during Computed Tomographic Fluoroscopy.

The purpose of this study was to evaluate scatter radiation dose to the subject surface during X-ray computed tomography (CT) fluoroscopy using the integrated dose ratio (IDR) of an X-ray dose profile derived from an optically stimulated luminescent (OSL) dosimeter. We aimed to obtain quantitative evidence supporting the radiation protection methods used during previous CT fluoroscopy. A multislice CT scanner was used to perform this study. OSL dosimeters were placed on the top and the lateral side of the chest phantom so that the longitudinal direction of dosimeters was parallel to the orthogonal axis-to-slice plane for measurement of dose profiles in CT fluoroscopy. Measurement of fluoroscopic conditions was performed at 120 kVp and 80 kVp. Scatter radiation dose was evaluated by calculating the integrated dose determined by OSL dosimetry. The overall percent difference of the integrated doses between OSL dosimeters and ionization chamber was 5.92%. The ratio of the integrated dose of a 100-mm length area to its tails (-50 to -6 mm, 50 to 6 mm) was the lowest on the lateral side at 80 kVp and the highest on the top at 120 kVp. The IDRs for different measurement positions were larger at 120 kVp than at 80 kVp. Similarly, the IDRs for the tube voltage between the primary X-ray beam and scatter radiation was larger on the lateral side than on the top of the phantom. IDR evaluation suggested that the scatter radiation dose has a high dependence on the position and a low dependence on tube voltage relative to the primary X-ray beam for constant dose rate fluoroscopic conditions. These results provided quantitative evidence supporting the radiation protection methods used during CT fluoroscopy in previous studies.