Thermoluminescent Measurements Research Articles

A novel silicon PIN photodiode device for radiation exposure monitoring in dental CBCT

This paper presents a versatile and cost-effective system for the monitoring of X-ray exposure during dental cone beam computed tomography procedures based on silicon PIN photodiode detectors. The system, developed and implemented at the University of Pisa's School of Engineering, underwent characterization under a range of operational conditions focusing on full field-of-view 3D protocols used in adult patient examinations. This study was facilitated by the Azienda Ospedaliero Universitaria Pisana, which provided access to a Planmeca ProMax 3D Classic scanner for the research. During the investigation, photodiodes were placed both on the surface and inside an Alderson RANDO phantom head to assess the dose delivered to regions near radiation-sensitive areas such as the salivary glands, thyroid, eye lens, and laryngopharynx. The evaluation process spanned a spectrum of tube voltages, ranging from 60 to 90 kVp, and tube currents, extending up to 16 mA, to ensure a broad and thorough analysis. Furthermore, to reinforce the effectiveness of the silicon photodiodes' measurement capabilities, calibrated GR-200 A-type thermoluminescent dosimeters were positioned within the phantom head inserts to serve as a reference point. Complementing this setup, PCXMC Rotation 2.0 simulations were conducted to further the efficacy of the monitoring system, particularly tailored to the specific dental CBCT protocols being investigated. In conclusion, while the research revealed a generally consistent correlation across PCXMC simulations, photodiode readings, and thermoluminescent dosimeter measurements, it is important to note that a direct comparison was not exactly possible due to limitations in the size and positioning of the systems. Variations up to 20–35% were observed, primarily due to the different positioning of the dosimeters and the unique physical and operational traits of the different measurement methods employed. Nevertheless, the development of an affordable, easily deployable, and scalable dosimetry monitoring system may provide a substantial contribution to enhancing patient safety in dental radiology and aid in the optimization of diagnostic X-ray protocols.

Structural and magneto-optical investigations of citrate sol–gel derived barium hexaferrite nanocrystalline powder

Magneto-optical measurements enable the identification of Fe2+ and Fe3+ in the R and S blocks of BaFe12O19 M-hexaferrite powder obtained by sol-gel processing, followed by thermal annealing at 900 C for 3 hours. The ferromagnetic phase is evidenced by the spin-majority configuration (Fe3+) due to their unpaired electrons between d-d orbitals, while the Fe2+ in the low spin possesses diamagnetic behavior strongly dependent on the surrounded crystal field. Additionally, the irradiation with gamma rays changes the ratio between Fe2+/Fe3+, mainly on the surface of BaFe12O19 nanocrystals. These changes were confirmed by X-ray Photoelectron Spectroscopy measurements, in which the concentration of Fe2+ increased from 69% to 82%, while the one of Fe3+ decreased from 31% to 18%. he thermoluminescent measurements reveal the same changes of Fe3+ in Fe2+ by electron capturing during irradiation, which is released as a red emission after recombination processes. The changes are explained by the increasing of some Fe-O bonds along the c-axis, mainly due to breaking a part of these bonds. The X-ray analysis confirms the changing of the parameters for the BaFe12O19 hexagonal structure.

The Effect of a Yb Co-Dopant on the Blue Upconversion and Thermoluminescent Emission of SrLaAlO4:Yb3+,Tm3+ Phosphors

In this study, we described the structural, morphological, optical, photoluminescence, and thermoluminescence properties of SrLaAlO4:Tm3+,Yb3+ (SLAO:Tm,Yb) blue-emitting phosphors made by combustion synthesis and a post-annealing treatment at 1200 °C. The Yb co-dopant concentration was varied (1.0, 3.0, 5.0, and 6.0 mol%) while the Tm dopant concentration was fixed at 5 mol%. According to the X-ray diffraction patterns, all the samples presented the pure tetragonal phase of SrLaAlO4. Scanning electron microscopy analysis showed that the SLAO powders had morphologies of irregular or bar grains with average sizes in the range of 0.5–1.07 µm. Photoluminescence emission under 980 nm excitation showed an intense blue emission peak at 481 nm. The phosphors also emitted red light at 654 nm and a prominent NIR emission at 801 nm. All those emissions correspond to 1G4 → 3H6, 1G4 → 3H4 and 3H4 → 3H6 transitions of Tm3+. The SLAO:Tm,Yb phosphors synthesized with 3.0 mol.% of the Yb co-dopant showed the highest emission intensity in the visible/near-infrared (NIR) range (400–800 nm), and its CIE coordinates corresponded to the blue color (0.19368, 0.15826). Additionally, thermoluminescence emissions were recorded for the SLAO:Tm,Yb phosphors. The samples were previously irradiated with UV wavelengths of 265 nm, 365 nm, and 385 nm prior to the thermoluminescent measurements. After this, the kinetic parameters such as frequency factors, activation energy (E), and order of kinetics were calculated using the Chen method. The thermoluminiscent emissions demonstrated that the SLAO:Yb,Tm phosphors can be used for UV dosimetry.

Simplified method for determining dose to a non-water phantom through the use of ND,w and IAEA TRS 483 for the GammaPod.

GammaPod, a breast stereotactic radiosurgery device, utilizes 25 rotating Co-60 sources to deliver highly conformal dose distributions. The GammaPod system requires that reference dosimetry be performed in a specific vendor-supplied poly-methylmethacrylate (PMMA) phantom. The nonstandard nature of GammaPod dosimetry, in both the phantom material and machine-specific reference (msr), prohibits use of the American Association of Physicists in Medicine Task Group 51 (TG-51) protocol. This study proposes a practical method using TRS 483 to make the reference dosimetry procedure simpler and to reduce overall uncertainties. The dose to PMMA (DPMMA) is determined under msr conditions using TRS 483 with an Exradin A1SL chamber placed in a PMMA phantom. The conversion factor, which converts from the dose-to-water (Dw) in broad-beam Co-60 reference geometry to DPMMA in the msr small field Co-60 (Qmsr) geometry, is derived using the Monte Carlo simulations and procedure described in TRS 483. The new conversion factor value for an Exradin A1SL chamber is 0.974. When combined with ND,w, DPMMA differs by 0.5% from the TG-21/Nx method and 0.2% from the IROC values. Uncertainty decreased from 2.2% to 1.6%. We successfully implemented TRS 483 reference dosimetry protocols utilizing ND,w for the GammaPod in the PMMA phantom. These results show not only agreement between measurements performed with the previously published method and independent thermoluminescent dosimetry measurements but also reductions in uncertainty. This also provides readers with a pathway to develop their own IAEA TRS 483 factor for any new small field machine that may be developed.

COMPARISON OF ORGAN ABSORBED DOSES IN WHOLE-BODY COMPUTED TOMOGRAPHY SCANS OF PAEDIATRIC AND ADULT PATIENT MODELS ESTIMATED BY DIFFERENT METHODS.

This study aimed to identify the uncertainty in estimations of organ absorbed dose using dedicated software by comparing with corresponding doses measured in physical phantoms. The comparison was performed for whole-body computed tomography (CT) obtained as part of positron emission tomography. Whole-body CT scans provide an advantage in terms of comparison because all organs are in the primary beam of the irradiated area. Organ doses estimated by the different software programs (CT-Expo, VirtualDose and NCICT) were compared by thermoluminescent detector measurements in anthropomorphic phantoms in 1-y-old, 5-y-old and adult patients. Differences were within ~15% in 12 major organs. However, differences of ~30% were observed in organs located at slightly different positions in the computational models compared to the physical phantoms. All investigated programs were deemed suitable for accurate estimation of organ absorbed dose.

Validation of the MC-GPU Monte Carlo code against the PENELOPE/penEasy code system and benchmarking against experimental conditions for typical radiation qualities and setups in interventional radiology and cardiology

Interventional procedures are associated with potentially high radiation doses to the skin. The 2013/59/EURATOM Directive establishes that the equipment used for interventional radiology must have a device or a feature informing the practitioner of relevant parameters for assessing patient dose at the end of the procedure. Monte Carlo codes of radiation transport are considered to be one of the most reliable tools available to assess doses. However, they are usually too time consuming for use in clinical practice. This work presents the validation of the fast Monte Carlo code MC-GPU for application in interventional radiology. MC-GPU calculations were compared against the well-validated Monte Carlo simulation code PENELOPE/penEasy by simulating the organ dose distribution in a voxelized anthropomorphic phantom. In a second phase, the code was compared against thermoluminescent measurements performed on slab phantoms, both in a calibration laboratory and at a hospital. The results obtained from the two simulation codes show very good agreement, differences in the output were within 1%, whereas the calculation time on the MC-GPU was 2500 times shorter. Comparison with measurements is of the order of 10%, within the associated uncertainty. It has been verified that MC-GPU provides good estimates of the dose when compared to PENELOPE program. It is also shown that it presents very good performance when assessing organ doses in very short times, less than one minute, in real clinical set-ups. Future steps would be to simulate complex procedures with several projections.

Effect of Ge:Si ratio and charging energy on carriers trapping in Y2(Ge,Si)O5:Pr powders observed with thermoluminescence methods

Oxyorthosilicates have long history in luminescent applications e.g. as phosphors, scintillators and in emerging technologies like luminescence thermometry. In this study we report detailed research on the thermoluminescent (TL) properties of Y2(Gex,Si1-x)O5:Pr. Despite regular TL measurements, Tmax-Tstop, initial rise analysis, fading, decay of persistent luminescence, and dose effect are presented and analyzed. The possibility to deliberately manage the electron trap depths adjusting the Ge/Si ratio is explored. Glow curve of each composition consists of two main TL peaks. In the (Ge,Si) solid continuous distribution of trap energies is observed. Strong thermoluminescence is observed from all compositions after charging with X-ray radiation. Efficiency of charging traps with UV-C photons (fitting the 4f→5d1 transition energy) lowers systematically as the Si content increases. A growing coupling of the excited 5d1 level of Pr3+ and the host conduction band with the increase of Ge content is responsible for this effect. A scheme of the TL-related processes is presented using the vacuum referred binding energy (VRBE) approach for all the Y2(Gex,Si1-x)O5:Pr phosphors.

Synthesis, luminescent and dosimetric properties of Li2B4O7:Cu,Ag,Tm

This work reports the preparation of a new thermoluminescent (TL) material obtained by doping the host salt of lithium borate with copper, silver and thulium ions (Li2B4O7:Cu, Ag, Tm). With the obtained material, sintered dosimeters in form of discs were made and exposed to gamma radiation from a 60Co source. It was found that these dosimeters show a sensitivity of approximately 40% of that shown by the commercial dosimeter TLD-100 (LiF:Mg,Ti). The thermally stimulated luminescence of the prepared material showed a linear response with dose for gamma radiation in the dose range from 0.001 to 50 Gy. Its luminescent signal remains constant during 24 h after irradiation, exhibiting a better behaviour than the commercial dosimeter TLD-800 (Li2B4O7:Mn) which decreases up to 60% of its original signal in the same period. The lower detection limit was determined to be equal to 0.1 mGy and TL measurements showed repeatability within 2.5%. The kinetic parameters were determined using several methods. The variable heating rate method showed the lowest energy value E of the main peak (peak 1). Initial rise and peak shape methods showed intermediate values whereas the deconvolution method showed the highest energy value E, using heating rates of 1, 2, 6 and 10 K/s. Results obtained from the morphology, crystallography, Raman spectroscopy and photoluminescence are also reported. These results suggest that this new thermoluminescent detector could be a promising material to use in clinical dosimetry applications.

Dosimetry evaluation of the GammaPod stereotactic radiosurgery device based on established AAPM and IAEA protocols.

The GammaPod is a novel dedicated prone breast stereotactic radiosurgery (SRS) device recently developed at the University of Maryland Medical Center. This device utilizes multiple rotating Co-60 sources to create highly conformal dose distributions for breast treatments, including boosts, partial breast irradiation, or presurgery SRS. However, due to its small field sizes and nonstandard geometry, existing calibration protocols cannot be directly applied. In this study, we adapt and implement the American Association of Physicists in Medicine Task Group 21 (TG-21) and International Atomic Energy Agency (IAEA) Technical Report Series 483 (TRS 483) protocols for reference dose measurements for the GammaPod. This represents the first published dosimetric investigation GammaPod and is meant to serve as a reference to future users commissioning and calibrating these devices. Reference dose measurements were performed following the TG-21/IAEA TRS 483 protocols using an ADCL-calibrated Exradin A1SL thimble chamber in a polymethyl methacrylate (PMMA) breast-mimicking phantom. Monte Carlo calculations and measurements were also performed in water to determine chamber-specific quality conversion factor converting reference field size (fref ) to machine-specific field sizes (fmsr ) (25-mm) as well as , the conversion factor from the (fmsr ) to the clinical field size (fclin ) (15mm). Verification was performed using the thermoluminescent dosimeter remote monitoring service from the Imaging and Radiation Oncology Core (IROC) in Houston, TX. The (fref ) to (fmsr ) chamber-specific factor was 0.992 while the (fmsr ) to (fclin ) chamber-specific factor was 1.014. The radiation absorbed dose to water measured in the PMMA phantom based on the TG-21/IAEA TRS 483 formalism agreed with IROC values to within 1% and 2% for the 25- and 15-mm collimators, respectively. We successfully implemented the TG-21 and TRS 483 reference dosimetry protocols for the GammaPod. These results show agreement between measurements performed with different reference dosimetry protocols and independent thermoluminescent measurements.

Thermoluminescence and persistent luminescence of Tb3+ activated CaYAl3O7

Persistent emission (more than 1.5 h) was observed in Tb3+-doped CaYAl3O7 (CYAM) samples after X-ray or UVC excitation. Thermoluminescent (TL) emission spectra showed that Tb3+ emission is responsible for the TL emission signal, indicating a mechanism with a single recombination and luminescence centre. The shape of TL peaks showed overlap of peaks, and thus more than one trapping centre, and this result was confirmed through Tm x TSTOP analysis. TL measurements as function of doses revealed that the TL peak positions do not change with increasing doses of UVC irradiation, which means that all TL peaks can be well described by first-order kinetics. The initial rise method was used to determine the activation energies, whereas E (eV) x Tstop plot showed a distribution of activation energy ranging from 1.1 to 1.3 eV. These depth traps were assigned to intrinsic defects in the host. Possible mechanisms were discussed considering the 4f ground state of Tb3+ and oxygen vacancies as recombination and trapping centres, respectively.

Оценка индекса дозы при использовании протоколов сканирования компьютерной томографии в коническом пучке для пациентов детского возраста

Purpose: Cone-beam computed tomography (CBCT) is an indispensable procedure for accurate patient positioning during radiation therapy (RT) in many clinical cases. However, the patients get an additional dose using CBCT. This dose is neither therapeutic nor diagnostic. It is very difficult to obtain the reliable information about the dose distribution within the patient using the CBCT. Despite this, there is a need to control the additional dose for the pediatric patients and reduce it. There are different approaches of imaging dose evaluation. Most accurate methods are based on the Monte-Carlo calculation and thermoluminescent dosimeters-based measurements. However, the implementation of these methods is complex and cumbersome, that makes impossible their application in routine clinical practice. The evaluation of dose indexes is an accessible and convenient alternative. The purpose of this study is evaluation of the cone beam computed tomography dose indexes for different imaging protocols and object sizes. Material and methods: The technique based on absolute and relative dose measurements for CBCT was used in this study. Absolute dose measurements were performed at the periphery and center of the FREEPOINT (CIRS) phantom using the Farmer type chamber FC65-P for each CBCT protocols. FREEPOINT (20 cm height, 30 cm width, 30 cm length) was used for imitation big chest and pelvis. Inner insert (16 cm diameter) of the phantom was used for imitation head, small chest and pelvis. The dose profiles were measured using I’mRT MatriXX (IBA) and analyzed by OmniPro-I’mRT software, dose indexes DLP (dose–length product) were calculated. Results: The dose indexes were identified for five protocols corresponding three scanning areas (Head and Neck, Chest and Pelvis). The dose indexes were 51.82 and 90.25 mGy×cm using Head and Neck S20 and Head and Neck M20 protocols respectively. The lowest dose index was obtained 13.28 mGy×cm for Fast Head and Neck S20. It was established that the scanning object size strongly affects on the dose index values and, as result, on the absorbed dose within the patient. The dose indexes were 305.42 and 187.53 mGy×cm using scanning protocol Chest M20 for small and big phantoms respectively. The similar results were obtained for scanning protocol Pelvis M15. The highest dose index was obtained 846.93 mGy×cm for the small phantom, while the dose index was 563.79 mGy×cm for the big phantom. The necessity of several clinical protocols to scan different areas was shown. Using of the Pelvis M15 protocol for head scanning may increase the additional point dose 96 times in comparison with Fast Head and Neck S20 protocol. Conclusion: The dose indexes were evaluated taking into account the size of the scanning object for different imaging protocols. Routine use of CBCT in clinical practice requires a sensible choice of the scanning protocol based on the results of the dose index estimation.

Tunable NIR long persistent luminescence and discovery of trap-distribution-dependent excitation enhancement in transition metal doped weak-crystal-field CaZnGe2O6

A long persistent phosphor (LPP) CaZnGe2O6: Cr3+ has been rationally designed and successfully fabricated. The weak crystal field surrounding Cr3+ activator enables an afterglow emission band 700–1200 nm almost covering the biological transparency window. In this work, a feasible route of Mn2+ codoping is suggested to precisely control the spectral shape, which further meets the demand of wide range and steady response to different photo-detectors in the biological transparency window. An interestingly synchronous improvement of persistent duration of Cr3+ and Mn2+ emission center is discovered in this process. Meanwhile, this codoping technique also achieves the enhancement of afterglow-excitation intensity. The design approach employed here inherently involves the ingenious engineering for combining the isolated traps in Cr3+, Mn2+ singly doped LPP, and for forming a continuous-distribution trap in Cr3+, Mn2+ co-doped LPP according to the thermoluminescent measurement. The highlighted redeployment of trap distribution will opens a vista of potential avenues for LPP design, afterglow mechanism analysis and functionalized application of bio imaging.

Charge carrier traps in tris-(8-hydroxyquinoline) aluminum

Thermoluminescent measurements between 40 and 300C revealed two traps in the irradiated Alq3 powder synthetized from Al(OH)3, at 0.8 and 1.1eV below the conduction band. These two traps have been assigned with the Alq3 facial and meridional isomers and the trapping process stand for a long time after the switching off the irradiation source. The spectra recorded an hour after switching recover 60% from the photoluminescence and also decreasing the TL signals. A theoretical model was proposed in order to explain the trapping and de-trapping processes in both meridional and facial Alq3 isomers based on the XPS measurements for the HOMO, LUMO, ionization potential and optical bandgap, completed with the DFT calculated parameters and similar experimental results concerning the evidences of the triplet states in Alq3 compound.

TLD measurements and Monte Carlo calculations of head and neck organ and effective doses for cone beam computed tomography using 3D Accuitomo 170.

In dentistry, the use of cone beam CT has steadily increased over the last few years. The aim of this study was to measure organ doses and to perform dose calculations based on Monte Carlo (MC) simulations to work out a basis for full three-dimensional (3D) dose calculations for any patient examination performed with the machine used in this study. TLD-100 LiF detectors were placed at 71 measurement positions on the surface and within a RT-Humanoid phantom to cover all relevant radiosensitive organs and tissues. Three examinations with different protocols were performed with the 3D Accuitomo® and dose calculations with MC simulations were carried out for the same three protocols using the EGSnrc MC transport code system. Field of views of 140 × 100, 80 × 50 and 40 × 40 mm2 were selected, the mean organ doses were measured as 5.2, 2.75 and 1.5 mGy and the effective doses were determined as 250, 97 and 48 µSv. For the MC simulation of organ doses and the thermoluminescent dosemeter measurements, an overall agreement within ±10.1% (two standard deviations) was achieved. The measured dose values for 3D Accuitomo® were about a factor 2 lower when compared with conventional CT examinations. Reliable results for the organ doses as well as effective dose values were achieved with thermoluminescent dosemeter measurements in the RT-Humanoid phantom. This study provides the basis for the application of MC simulations for further dose determinations of cone beam CT machines. The MC calculation may therefore be a valuable tool to support the dentists in the evaluation of the trade-off between additional information that may be relevant to the choice of therapy and the additional dose given to the patient.

Evaluating the exposure dose of 320-row area detector computed tomography and its reliability in the measurement of bone defect in alveolar cleft

ObjectiveThe usefulness of computed tomography (CT) for measuring bone defect volume in the alveolar cleft has attracted considerable attention in recent years. Moreover, 320-row area detector CT (320-ADCT) is currently widely utilized. This technology helps to acquire smooth three-dimensional images, with a reduced exposure dose and improved image resolution, similar to those of dental cone-beam CT (CBCT). We compared the exposure dose of 320-ADCT with that of dental CBCT, and analyzed the reliability of a volumetric method for measuring bone defects in the alveolar cleft using 320-ADCT, both experimentally and clinically. MethodsWe performed thermoluminescent dosimeter measurements using an anthropomorphic RANDO phantom. Additionally, we evaluated the reproducibility of the volumetric measurement method for the bone defective volume using CT images of simulated bone defects in pigs. In addition, we evaluated the inter-rater reliability of the volumetrically measured values of bone defects in 20 patients with a unilateral cleft. ResultsThe exposure doses of 320-row area detector CT and CBCT were similar. The errors of volumetric values between calculated and actual bone defects created in pigs were up to 7.6%. Inter-rater reliability of the calculated volumes of bone defect was evaluated as high, according to Bland–Altman analysis. ConclusionsCT examination with a low exposure dose and precise analysis is feasible without the use of highly specialized dental CBCT.

ESTABLISHMENT OF RADIATION DOSES FOR PEDIATRIC X-RAY EXAMINATIONS IN A LARGE PEDIATRIC HOSPITAL IN TURKEY.

Pediatric patients are more sensitive to ionizing radiation when compared with adults. The aim of this study was to evaluate the radiation doses for some common pediatric x-ray examinations performed with various digital radiography systems. Quality control tests of the digital radiography systems were carried out according to international published protocols before the pediatric dose measurements. Radiation dose measurement was performed by using the x-ray tube outputs and thermoluminescent dosimeter dose measurement methods. In the present study, radiation doses were assessed for 247 chest, 230 pelvis, 194 skull and 73 abdomen x-ray examinations and in total 744 pediatric patients doses were measured. Pediatric patients were classified into four age groups 0-1, 1-5, 5-10 and 10-15 years as given by European Commission guidance. Effective doses were determined for each examination using a PCXMC 2.0 Monte Carlo program. The mean measured entrance skin doses for the age interval 1-5 years and AP projection by using tube output measurement methods were 149 µGy for chest, 304 µGy for pelvis, 387 µGy for skull and 199 µGy for abdomen examinations. The radiation dose results obtained in this study were in the range of the published results in the literature.

Small field depth dose profile of 6 MV photon beam in a simple air-water heterogeneity combination: A comparison between anisotropic analytical algorithm dose estimation with thermoluminescent dosimeter dose measurement.

To establish trends of estimation error of dose calculation by anisotropic analytical algorithm (AAA) with respect to dose measured by thermoluminescent dosimeters (TLDs) in air-water heterogeneity for small field size photon. TLDs were irradiated along the central axis of the photon beam in four different solid water phantom geometries using three small field size single beams. The depth dose profiles were estimated using AAA calculation model for each field sizes. The estimated and measured depth dose profiles were compared. The over estimation (OE) within air cavity were dependent on field size (f) and distance (x) from solid water-air interface and formulated as OE = - (0.63 f + 9.40) x2+ (-2.73 f + 58.11) x + (0.06 f2 - 1.42 f + 15.67). In postcavity adjacent point and distal points from the interface have dependence on field size (f) and equations are OE = 0.42 f2 - 8.17 f + 71.63, OE = 0.84 f2 - 1.56 f + 17.57, respectively. The trend of estimation error of AAA dose calculation algorithm with respect to measured value have been formulated throughout the radiation path length along the central axis of 6 MV photon beam in air-water heterogeneity combination for small field size photon beam generated from a 6 MV linear accelerator.

Development and Validation of a Small Animal Immobilizer and Positioning System for the Study of Delivery of Intracranial and Extracranial Radiotherapy Using the Gamma Knife System.

The purpose of this research is to establish a process of irradiating mice using the Gamma Knife as a versatile system for small animal irradiation and to validate accurate intracranial and extracranial dose delivery using this system. A stereotactic immobilization device was developed for small animals for the Gamma Knife head frame allowing for isocentric dose delivery. Intercranial positional reproducibility of a reference point from a primary reference animal was verified on an additional mouse. Extracranial positional reproducibility of the mouse aorta was verified using 3 mice. Accurate dose delivery was validated using film and thermoluminescent dosimeter measurements with a solid water phantom. Gamma Knife plans were developed to irradiate intracranial and extracranial targets. Mice were irradiated validating successful targeted radiation dose delivery. Intramouse positional variability of the right mandible reference point across 10 micro-computed tomography scans was 0.65 ± 0.48 mm. Intermouse positional reproducibility across 2 mice at the same reference point was 0.76 ± 0.46 mm. The accuracy of dose delivery was 0.67 ± 0.29 mm and 1.01 ± 0.43 mm in the coronal and sagittal planes, respectively. The planned dose delivered to a mouse phantom was 2 Gy at the 50% isodose with a measured thermoluminescent dosimeter dose of 2.9 ± 0.3 Gy. The phosphorylated form of member X of histone family H2A (γH2AX) staining of irradiated mouse brain and mouse aorta demonstrated adjacent tissue sparing. In conclusion, our system for preclinical studies of small animal irradiation using the Gamma Knife is able to accurately deliver intracranial and extracranial targeted focal radiation allowing for preclinical experiments studying focal radiation.

Investigation of conformal and intensity-modulated radiation therapy techniques to determine the absorbed fetal dose in pregnant patients with breast cancer

The aim of this research was to investigate the fetal doses of pregnant patients undergoing conformal radiotherapy or intensity-modulated radiation therapy (IMRT) for breast cancers. An Alderson Rando phantom was chosen to simulate a pregnant patient with breast cancer who is receiving radiation therapy. This phantom was irradiated using the Varian Clinac DBX 600 system (Varian Medical System, Palo Alto, CA) linear accelerator, according to the standard treatment plans of both three-dimensional conformal radiation therapy (3-D CRT) and IMRT techniques. Thermoluminescent dosimeters were used to measure the irradiated phantom׳s virtually designated uterus area. Thermoluminescent dosimeter measurements (in the phantom) revealed that the mean cumulative fetal dose for 3-D CRT is 1.39cGy and for IMRT it is 8.48cGy, for a pregnant breast cancer woman who received radiation treatment of 50Gy. The fetal dose was confirmed to increase by 70% for 3-D CRT and 40% for IMRT, if it is closer to the irradiated field by 5cm. The mean fetal dose from 3-D CRT is 1.39cGy and IMRT is 8.48cGy, consistent with theoretic calculations. The IMRT technique causes the fetal dose to be 5 times more than that of 3-D CRT. Theoretic knowledge concerning the increase in the peripheral doses as the measurements approached the beam was also practically proven.

Preparation of cerium doped calcium pyrophosphate: Study of luminescent behavior

Thermoluminescent (TL) and photoluminescent (PL) band emissions of cerium doped calcium pyrophosphate (Ca2O7P2:Ce3+) were studied. Wet precipitation method was used to synthesize calcium pyrophosphate, doped with Ce3+ (1.0at%) impurities, from orthophosphoric acid and calcium acetate, as raw materials. The effect of temperature annealing at 800 and 900°C was investigated. X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM) were used to characterize both as-precipitated and annealed powders samples. The PL emission spectrum of samples annealed at 900°C displayed characteristics 5d–4f transitions of Ce3+ at 333nm and 360nm. TL measurements were carried out on as-precipitated and annealed samples from room temperature (RT) up to 350°C. The TL results of annealed samples showed complex TL glow curves, a linear response in the absorbed dose range of 0.5–5Gy and a good reproducibility after 10 cycles of irradiation-readout. The complex TL glow curves of annealed samples were analyzed by the methods of Tmax–TStop, Initial Rise (IR) and Computational Glow-Curve Deconvolution (CGCD) assuming a General Order Kinetic (GOK).