Optically Stimulated Luminescent Response of the LiMgPO4 Silicone Foils to Protons and Its Dependence on Proton Energy.

Modern radiotherapy (RT) techniques, such as proton therapy, require more and more sophisticated dosimetry methods and materials. One of the newly developed technologies is based on flexible sheets made of a polymer, with the embedded optically stimulated luminescence (OSL) material in the form of powder (LiMgPO4, LMP) and a self-developed optical imaging setup. The detector properties were evaluated to study its potential application in the proton treatment plan verification for eyeball cancer. The data showed a well-known effect of lower luminescent efficiency of the LMP material response to proton energy. The efficiency parameter depends on a given material and radiation quality parameters. Therefore, the detailed knowledge of material efficiency is crucial in establishing a calibration method for detectors exposed to mixed radiation fields. Thus, in the present study, the prototype of the LMP-based silicone foil material was tested with monoenergetic uniform proton beams of various initial kinetic energies constituting the so-called spread-out Bragg peak (SOBP). The irradiation geometry was also modelled using the Monte Carlo particle transport codes. Several beam quality parameters, including dose and the kinetic energy spectrum, were scored. Finally, the obtained results were used to correct the relative luminescence efficiency response of the LMP foils for monoenergetic and spread-out proton beams.

Magnetic particle based MRI thermometry at 0.2 T and 3 T.

This study provides insight into the advantages and disadvantages of using ferrite particles embedded in agar gel phantoms as MRI temperature indicators for low-magnetic field scanners. We compare the temperature-dependent intensity of MR images at low-field (0.2 T) to those at high-field (3.0 T). Due to a shorter T1 relaxation time at low-fields, MRI scanners operating at 0.2 T can use shorter repetition times and achieve a significant T2⁎ weighting, resulting in strong temperature-dependent changes of MR image brightness in short acquisition times. Although the signal-to-noise ratio for MR images at 0.2 T MR is much lower than at 3.0 T, it is sufficient to achieve a temperature measurement uncertainty of about ±1.0 °C at 37 °C for a 90 µg/mL concentration of magnetic particles.

Influence of Elevated Temperature on Color Centers in LiF Crystals and Their Photoluminescence.

The radiation-induced photoluminescence (PL) of LiF has found its way into many applications for the detection and imaging of ionizing radiation. In this work, the influence of thermal treatment at temperatures up to 400 °C on absorption and PL emission spectra as well as fluorescent nuclear tracks in irradiated LiF crystals was investigated. It was found that carrying out PL measurements with the crystals kept at the temperature of about 80 °C leads to a considerable increase in luminescence emission of F3+ color centers at 525 nm. This enhancement of PL intensity allows for the microscopic imaging of the fluorescent nuclear tracks using only F3+ emission, which is not possible at room temperature. It was also found that heating the irradiated crystals before measurement at temperatures from 100 °C to 200 °C increases the concentration of F3+ centers. However, the related enhancement of PL emission is insufficient in terms of enabling the observation of the fluorescent tracks in this part of the spectrum. In the case of the main PL emission at 670 nm related to F2 centers, the thermal treatment at around 290 °C substantially increases the intensity of fluorescent tracks. This effect, however, was found to occur only at low fluences of alpha particles (up to about 109 cm-2); therefore, it is barely visible in the emission spectrum and not noticeable in the absorption spectrum.

Tibial shaft fractures in children: flexible intramedullary nailing in growing children especially weighing 50 kg (110 lbs) or more.

Currently the gold standard in surgical treatment of displaced tibial shaft fractures in children with open growth cartilage is elastic stable intramedullary nailing (ESIN). The purpose of this study is the analysis of indications, complications, and duration of treatment using intramedullary flexible nails in children who are still growing but especially weighing 50 kg or more. Hospital records from 2017 to 2020 were retrospectively reviewed to identify the children from 4 to 17 years of age with displaced tibial shaft fractures admitted to the hospital. Only children with open growth cartilage, with a minimum of 6 months of follow-up and complete clinical data, were included. Studies of 91 children xwere analyzed. The average patient age at the time of the injury was 10.88 ± 2.82 years. In the entire group, 31.9% children weighed 50 kg or more, and 68.1% of the children were below this weight. All children were treated using ESIN. The mean time to nail removal was 8.4 ± 4.09 months in the whole group of children stabilized with ESIN. There were no differences in the two groups depending on the weight ( P = 0.637). Only two adverse events were observed. This study demonstrates that the use of ESIN in displaced tibial shaft fractures in growing children weighing 50 kg or more is acceptable and safe. The discussion to be made is whether it is still an acceptable method of treatment for this type of fracture due to the progressive obesity epidemic in children and adolescents.

Infrared Stimulated Luminescence of Ce3+ Doped YAG Crystals.

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements.

Development of the Composite Thermoluminescent Detectors Based on the Single Crystalline Films and Crystals of Perovskite Compounds.

This work is dedicated to the development of new types of composite thermoluminescent detectors based on the single crystalline films of Ce-doped GdAlO3 perovskite and Mn-doped YAlO3 and (Lu0.8Y0.2)AlO3:Mn perovskites as well as Ce and Pr-doped YAlO3 single crystal substrates. These detectors were obtained using the Liquid Phase Epitaxy growth method from the melt solution based on the PbO-B2O3 fluxes. Such composite detectors can by applied for the simultaneous registration of different components of mixed ionization fluxes using the differences between the thermoluminescent glow curves, recorded from the film and crystal parts of epitaxial structures. For creation of the new composite detectors, we considered using, for the film and crystal components of epitaxial structures (i) the different perovskite matrixes doped with the same type of activator or (ii) the same perovskite host with various types of activators. The thermoluminescent properties of the different types of epitaxial structures based on the abovementioned films and crystal substrates were examined in the conditions of ß-particles and X-ray excitation with aim of determination of the optimal combination of perovskites for composite detectors. It was shown that, among the structures with all the studied compositions, the best properties for the simultaneous thermoluminescent detection of α- and X-rays were the GdAlO3:Ce film/YAlO3:Ce crystal epitaxial structure.

Application of the LPE-Grown LuAG: Ce Film/YAG Crystal Composite Thermoluminescence Detector for Distinguishing the Components of the Mixed Radiation Field.

Single-crystalline films (SCFs) of the LuAG: Ce garnet grown using the liquid-phase epitaxy method onto YAG single-crystal (SC) substrates were investigated for possible applications as composite thermoluminescent (TL) detectors. Such detectors may help to register the different components of ionizing radiation fields with various penetration depths, e.g., heavy charged particles and gamma or beta rays. It was found that the TL signal of LuAG: Ce SCF sufficiently differs from that of the YAG substrate concerning both the temperature and wavelength of emissions. Furthermore, even by analyzing TL glow curves, it was possible to distinguish the difference between weakly and deeply penetrating types of radiation. Within a test involving the exposure of detectors with the mixed alpha/beta radiations, the doses of both components were determined with an accuracy of a few percent.

Electron Beam Radiation as a Safe Method for the Sterilization of Aceclofenac and Diclofenac-The Usefulness of EPR and 1H-NMR Methods in Determination of Molecular Structure and Dynamics.

Diclofenac (DC) [2-(2,6-Dichloroanilino)phenyl]acetic acid,) and aceclofenac (AC) 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl]oxyacetic acid in substantia were subjected to ionizing radiation in the form of a beam of high-energy electrons from an accelerator in a standard sterilization dose of 25 kGy and higher radiation doses (50-400 kGy). We characterized non-irradiated and irradiated samples of DC and AC by using the following methods: organoleptic analysis (color, form), spectroscopic (IR, NMR, EPR), chromatographic (HPLC), and others (microscopic analysis, capillary melting point measurement, differential scanning calorimetry (DSC)). It was found that a absorbed dose of 50 kGy causes a change in the color of AC and DC from white to cream-like, which deepens with increasing radiation dose. No significant changes in the FT-IR spectra were observed, while no additional peaks were observed in the chromatograms, indicating emerging radio-degradation products (25 kGy). The melting point determined by the capillary method was 153.0 °C for AC and 291.0 °C for DC. After irradiation with the dose of 25 kGy for AC, it did not change, for DC it decreased by 0.5 °C, while for the dose of 400 kGy it was 151.0 °C and 286.0 °C for AC and DC, respectively. Both NSAIDs exhibit high radiation stability for typical sterilization doses of 25-50 kGy and are likely to be sterilized with radiation at a dose of 25 kGy. The influence of irradiation on changes in molecular dynamics and structure has been observed by 1H-NMR and EPR studies. This study aimed to determine the radiation stability of DC and AC by spectrophotometric, thermal and chromatographic methods. A standard dose of irradiation (25 kGy) was used to confirm the possibility of using this dose to obtain a sterile form of both NSAIDs. Higher doses of radiation (50-400 kGy) have been performed to explain the changes in DC and AC after sterilization.

APTES-Modified SBA-15 as a Non-Toxic Carrier for Phenylbutazone.

Improvement of the bioavailability of poorly soluble medicinal substances is currently one of the major challenges for pharmaceutical industry. Enhancing the dissolution rate of those drugs using novel methods allows to increase their bioavailability. In recent years, silica-based mesoporous materials have been proposed as drug delivery systems that augment the dissolution rate. The aim of this study was to analyse the influence of phenylbutazone adsorption on SBA-15 on its dissolution rate. Moreover, we examined the cytotoxicity of the analyzed silica. The material was characterized by SEM, TEM, DSC, 1H-NMR, XRD, and FT-IR. The phenylbutazone did not adsorb on unmodified SBA-15, while the adsorption on APTES-modified SBA-15 resulted in 50.43 mg/g of loaded phenylbutazone. Phenylbutazone adsorbed on the APTES-modified SBA-15 was then released in the hydrochloric acidic medium (pH 1.2) and phosphate buffer (pH 7.4) and compared to the dissolution rate of the crystalline phenylbutazone. The release profiles of the amorphous form of adsorbed phenylbutazone are constant in different pH, while the dissolution rate of the crystalline phenylbutazone depends on the pH. The cytotoxicity assays were performed using the Caco-2 cell line. Our results indicate that the analyzed material ensured phenylbutazone adsorption in an amorphous state inside the mesopores and increased its dissolution rate in various pH levels. Furthermore, the cytotoxicity assay proved safety of studied material. Our study demonstrated that APTES-modified SBA-15 can serve as a non-toxic drug carrier that improves the bioavailability of phenylbutazone.

Composite Detectors Based on Single-Crystalline Films and Single Crystals of Garnet Compounds.

This manuscript summarizes recent results on the development of composite luminescent materials based on the single-crystalline films and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of mixed ionization fluxes, as well as scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation/TL materials based on Ce3+-, Pr3+-, and Sc3+-doped Lu3Al5O12 garnets, as well as Ce3+-doped Gd3-xAxAl5-yGayO12 mixed garnets, where A = Lu or Tb; x = 0-1; y = 2-3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals, and epitaxial structures of these garnet compounds using absorption, cathodoluminescence, and photoluminescence. The scintillation and TL properties of the developed materials under α- and ß-particles and γ-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

Improved solubility of lornoxicam by inclusion into SBA-15: Comparison of loading methods.

An increasing proportion of new medicinal substances are poorly soluble in water. Adsorption on mesoporous silicas increases their bioavailability when administered orally. Loading method determines adsorption either on the surface in crystalline state or inside the mesopores in amorphus form. The aim of this study was to compare two methods (adsorption equilibrium and solvent evaporation) of lornoxicam adsorption on SBA-15 and APTES-modified SBA-15 in terms of drug adsorption site. Additionally, we investigated the drug release profiles at different pH and cytotoxicity of the analysed mesoporous materials. The materials were characterized by a number of physicochemical techniques including X-ray diffraction, nitrogen adsorption/desorption techniques, differential scanning calorimetry, thermogravimetric analysis, scanning and transmission electron microscopy, infrared spectroscopy and 1H NMR. Lornoxicam was loaded on the studied materials and released in the media (HCl pH 1.2, phosphate buffers pH 6.8 and 7.4). The cytotoxicity assays of APTES-modified SBA-15 were performed on CaCo-2 human colon cancer cell line. We proved that adsorption equilibrium method is a more advantageous method of loading. It ensures drug adsorption in an amorphous state inside the mesopores. The solvent evaporation method, despite a greater amount of loaded drug, results in drug adsorption in a crystalline state on the silica surface. In drug release studies a greater amount of lornoxicam is released from modified materials compared to crystalline lornoxicam. Cytotoxicity study proved the safety of APTES-modified silica. We concluded that APTES-modified SBA-15 is applicable as an effective and non-toxic carrier for the poorly soluble drug lornoxicam. The adsorption equilibrium method should be the preferred loading method. It enables the adsorption of sparingly soluble substances inside the mesoproes and enhances bioavailability of oral pharmaceutical forms.

Modification of the Release of Poorly Soluble Sulindac with the APTES-Modified SBA-15 Mesoporous Silica.

The effectiveness of oral drug administration is related to the solubility of a drug in the gastrointestinal tract and its ability to penetrate the biological membranes. As most new drugs are poorly soluble in water, there is a need to develop novel drug carriers that improve the dissolution rate and increase bioavailability. The aim of this study was to analyze the modification of sulindac release profiles in various pH levels with two APTES ((3-aminopropyl)triethoxysilane)-modified SBA-15 (Santa Barbara Amorphous-15) silicas differing in 3-aminopropyl group content. Furthermore, we investigated the cytotoxicity of the analyzed molecules. The materials were characterized by differential scanning calorimetry, powder X-ray diffraction, scanning and transmission electron microscopy, proton nuclear magnetic resonance and Fourier transformed infrared spectroscopy. Sulindac loaded on the SBA-15 was released in the hydrochloric acidic medium (pH 1.2) and phosphate buffers (pH 5.8, 6.8, and 7.4). The cytotoxicity studies were performed on Caco-2 cell line. The APTES-modified SBA-15 with a lower adsorption capacity towards sulindac released the drug in a less favorable manner. However, both analyzed materials improved the dissolution rate in acidic pH, as compared to crystalline sulindac. Moreover, the SBA-15, both before and after drug adsorption, exhibited insignificant cytotoxicity towards Caco-2 cells. The presented study evidenced that SBA-15 could serve as a non-toxic drug delivery system that enhances the dissolution rate of sulindac and improves its bioavailability.

3D Dosimetry Based on LiMgPO4 OSL Silicone Foils: Facilitating the Verification of Eye-Ball Cancer Proton Radiotherapy.

A direct verification of the three-dimensional (3D) proton clinical treatment plan prepared for tumor in the eyeball, using the Eclipse Ocular Proton Planning system (by Varian Medical Systems), has been presented. To achieve this, a prototype of the innovative two-dimensional (2D) circular silicone foils, made of a polymer with the embedded optically stimulated luminescence (OSL) material in powder form (LiMgPO4), and a self-developed optical imaging system, consisting of an illuminating light source and a high-sensitive CCD camera has been applied. A specially designed lifelike eyeball phantom has been used, constructed from 40 flat sheet LMP-based silicone foils stacked and placed together behind a spherical phantom made by polystyrene, all to reflect the curvature of the real eyeball. Two-dimensional OSL signals were captured and further analyzed from each single silicone foil after irradiation using a dedicated patient collimator and a 58.8 MeV modulated proton beam. The reconstructed 3D proton depth dose distribution matches very well with the clinical treatment plan, allowing for the consideration of the new OSL system for further 3D dosimetry applications within the proton radiotherapy area.

Intrinsic and Dopant-Related Luminescence of Undoped and Tb Plus Tm Double-Doped Lithium Magnesium Phosphate (LiMgPO4, LMP) Crystals.

In this work, the luminescence properties of undoped, Tm3+ doped, and Tb3+ plus Tm3+ double-doped crystals of the lithium magnesium phosphate (LiMgPO4, LMP) compound were investigated. The crystals under study were grown from melt using the micro-pulling-down method. The intrinsic and dopant-related luminescence of these crystals were studied using cathodo-, radio-, photo-, and thermoluminescence methods. Double doping with Tb3+ and Tm3+ ions was analyzed as these dopants are expected to exhibit an opposite trapping nature, namely to create the hole and electron-trapping sites, respectively. The spectra measured for the undoped samples revealed three prominent broad emission bands with maxima at around 3.50, 2.48, and 1.95 eV, which were associated with intrinsic structural defects within the studied compound. These were expected due to the anion vacancies forming F+-like centers while trapping the electrons. The spectra measured for Tb and Tm double-doped crystals showed characteristic peaks corresponding to the 4f-4f transitions of these dopants. A simplified model of a recombination mechanism was proposed to explain the temperature dependence of the measured thermally stimulated luminescence spectra. It seems that at low temperatures (below 300 °C), the charge carriers were released from 5D3-related Tb3+ trapping sites and recombination took place at Tm-related sites, giving rise to the characteristic emission of Tm3+ ions. At higher temperatures, above 300 °C, the electrons occupying the Tm3+-related trapping sites started to be released, and recombination took place at 5D4-related Tb3+ recombination centers, giving rise to the characteristic emission of Tb3+ ions. The model explains the temperature dependence observed for the luminescence emission from double-doped LiMgPO4 crystals and may be fully applicable for the consideration of emissions of other double-doped compounds.

MICRODOSIMETRIC UNDERSTANDING OF DOSE RESPONSE AND RELATIVE EFFICIENCY OF THERMOLUMINESCENCE DETECTORS.

LiF:Mg,Ti detectors show relative efficiency η for heavy charged particles significantly lower than one. It was for a long time not recognised that η varies also for electron energies and, as a consequence for photons. For LiF:Mg,Cu,P detectors measured photon energy response was named 'anomalous' because it differed significantly from the ratio of photon absorption coefficients. The decrease of η was explained as a microdosimetric effect due to local saturation of trapping centres around the electron track. For TLD-100 it was noticed by Horowitz that the measured photon energy response disagrees with the ratio of absorption coefficient by about 10%. It was demonstrated that a fraction of the TL signal in LiF:Mg,Ti is generated in the supralinear dose-response range, due to the high local doses generated by photon-induced tracks. Prediction of TL efficiency is particularly important in space dosimetry and in dosimetry of therapeutic beams like protons or carbon ions.

Uniformity of Thermoluminescence and Optically Stimulated Luminescence Signals Over the Length of Doped LiMgPO4 Crystal Rods Grown by Micro-Pulling-Down Method.

The purpose of this work was to systematically assess the distribution of thermoluminescence (TL) and optically stimulated luminescence (OSL) properties along the length of crystals grown by the micro-pulling-down method, in relation to the microstructure and distribution of activators. We analyzed lithium magnesium phosphate (LiMgPO4; LMP) crystals doped with terbium (Tb; 0.8 mol%) or with a combination of thulium (Tm; 0.8 mol% or 1.2 mol%) and boron (B; 10 mol%). Crystals of several centimeters in length and 3 mm in diameter were cut into 20-40 slices, depending on length. For each sample, TL glow curves and OSL decay curves were examined. Optical microscopy and scanning electron microscopy were used to assess the microstructure and elemental composition of several selected samples. Two-dimensional TL readouts were performed to identify the areas with higher and lower signal emission. Our study showed that there may be significant differences not only in LMP sensitivity along the crystal's axis but also on the surface of the slice. The distribution of activators varies depending on the type of crystals and strongly affects luminescence properties.

Thermoluminescence Enhancement of LiMgPO4 Crystal Host by Tb3+ and Tm3+ Trivalent Rare-Earth Ions Co-doping.

We investigated the influence of terbium and thulium trivalent rare-earth (RE) ions co-doping on the luminescent properties enhancement of LiMgPO4 (LMP) crystal host. The studied crystals were grown from the melt by micro-pulling-down (MPD) technique. Luminescent properties of the obtained crystals were investigated by thermoluminescence (TL) method. The most favorable properties and the highest luminescence enhancement were measured for Tb and Tm double doped crystals. A similar luminescence level can be also obtained for Tm, B co-doped samples. In this case, however, the low-temperature TL components have a significant contribution. The measured luminescent spectra showed a typical emission of Tb3+ and Tm3+ ions of an opposite trapping nature, namely the holes and electron-trapping sites, respectively. The most prominent transitions of 5D4 → 7F3 (550 nm for Tb3+) and 1D2 → 3F4 (450 nm for Tm3+) were observed. It was also found that Tb3+ and Tm3+ emissions show temperature dependence in the case of double doped LMP crystal sample, which was not visible in the case of the samples doped with a single RE dopant. At a low temperature range (up to around 290 °C) Tm3+ emission was dominant. At higher temperatures, the electrons occupying Tm3+ sites started to be released giving rise to emissions from Tb-related recombination centers, and emissions from Tm3+ centers simultaneously decreased. At the highest temperatures, emission took place from Tb3+ recombination centers, but only from deeper 5D4 level-related traps which had not been emptied at a lower temperature range.

OSL dosimetric properties and efficiency of Brazilian natural calcium fluoride pellets.

Calcium fluoride (CaF2), in both natural and synthetic forms, has been exhaustively studied and explored as thermoluminescent (TL) detector. However its sensitivity to ambient light points to the applicability of CaF2 as OSL (Optically Stimulated Luminescence) detector, increasing the research about its luminescent properties. Although some properties to employ CaF2 detectors with OSL technique have been already demonstrated, there is a lack of some essential information as the OSL response to different types and energy of ionizing radiation. In order to extend the use of Brazilian natural CaF2 with OSL technique, we evaluated the efficiency and dosimetric properties of cold pressed CaF2:NaCl pellets. The CaF2 detectors presented good reproducibility and negligible fading of the signal over one month after irradiation. The dose response using OSL, TL and residual TL showed linear behavior for different radiation beams (protons, photons and alpha and beta particles), being equivalent to the results obtained with BeO and MTS (LiF) detectors through OSL and TL technique respectively. Moreover, differences were observed in OSL efficiency according the beam type and energy; CaF2 detectors presented a higher OSL and TL sensitivities to protons, photons and beta particles than to alpha particles. The energy response to photons obtained using OSL and residual TL intensities present an over response at lower photon energy similar to TL energy response. In addition, differences in the OSL curve shapes were observed according to radiation type and energy, pointing to the possibility of applying this material in mixed radiation fields and to estimate average LET (Linear Energy Transfer).

High-Dose TL Dosimetry of Reactor Neutrons.

Radiation dose was measured with set of TL dosimeters during checkout of neutron radiation hardness of the ORTEC preamplifier type 142A in the experiment at the MARIA nuclear reactor at the National Centre for Nuclear Research (NCBJ), Otwock-Swierk, Poland. Different types of LiF-based TL detectors have been used for measurements in order to evaluate neutron and non-neutron components of the radiation field in the reactor channel during exposure and to check their relevancy for dose measurements in the reactor environment. For high-dose evaluation a new Ultra-High-Temperature Ratio (UHTR) method established for highly sensitive LiF:Mg,Cu,P detectors has been applied. Neutron fluence evaluated from TL measurements was in good agreement with one calculated using neutron flux data during the experiment.