Advancing Near-Infrared Light Sources: Enhancing Chromium Emission through Cation Substitution in Ultra-Broadband Near-Infrared Phosphors

The growing interest in the use of near-infrared (NIR) radiation for spectroscopy, optical communication, and medical applications spanning both NIR-I (700-900 nm) and NIR-II (900-1700 nm) has driven the need for new NIR light sources. NIR phosphor-converted light-emitting diodes (pc-LEDs) are expected to replace traditional lamps mainly due to their high efficiency and compact design. Broadband NIR phosphors activated by Cr3+ and Cr4+ have attracted significant research interest, offering emission across a wide range from 700 to 1700 nm. In this work, we synthesized a series of Sc2(1-x)Ga2xO3:Cr3+/4+ materials (x = 0-0.2) with broadband NIR-I (Cr3+) and NIR-II (Cr4+) emission. We observed a substantial increase in the intensity of Cr3+ (approximately 77 times) by incorporating Ga3+ ions. Additionally, our investigation revealed that energy transfer occurred between Cr3+ and Cr4+ ions. Configuration diagrams are presented to elucidate the behavior of Cr3+ and Cr4+ ions within the Sc2O3 matrix. We also observed a phase transition at a pressure of 20.2 GPa, resulting in a new unknown phase where Cr3+ luminescence exhibited a high-symmetry environment. Notably, this study presents the pressure-induced shift of NIR Cr4+ luminescence in Sc2(1-x)Ga2xO3:Cr3+/4+. The linear shifts were estimated at 83 ± 3 and 61 ± 6 cm-1/GPa before and after the phase transition. Overall, our findings shed light on the synthesis, luminescent properties, temperature, and high-pressure behavior within the Sc2(1-x)Ga2xO3:Cr3+/4+ materials. This research contributes to the understanding and potential applications of these materials in the development of efficient NIR light sources and other optical devices.

Hidden Hexavalent Chromium Ions with Subtle Structural Evolution in Near-Infrared Phosphors

Cr-doped inorganic materials are pivotal in developing near-infrared optical materials; however, multivalent Cr ions and their respective distribution in the materials remain ambiguous. Herein, a series of Li(Sc1-xInx)O2:Cr phosphors containing both Cr3+/Cr6+ ions are prepared. High-resolution synchrotron X-ray diffraction (XRD) reveals two similar phases in Li(Sc1-xInx)O2. Raman spectra further confirm distinct scattering patterns for the two end-member compositions, corroborating the findings from the synchrotron XRD analysis. Cr K-edge X-ray absorption near-edge structure and extended X-ray absorption fine structure demonstrate that most Cr ions in the as-prepared samples are Cr6+, while Cr3+ becomes dominant after washing with water. Moreover, the source and distribution of Cr3+ and Cr6+ ions in the as-prepared and washed samples are revealed through X-ray fluorescence and X-ray excited optical luminescence techniques, which indicate that Cr6+ ions aggregate within the sample, while Cr3+ ions are evenly distributed. Photoluminescence, decay curves, and line shape analyses are implemented to resolve the electron-lattice interactions, and the corresponding mechanisms are provided to explain the asymmetry between photoluminescence and photoluminescence excitation spectra. Overall, this study provides valuable insights into the distribution of low-concentration multivalence ions in solid-state materials and offers a deeper understanding of the approaches to precisely resolve the subtle changes in the crystal structure.

Lanthanide ions (Eu3+, Er3+, Pr3+) as luminescence and charge carrier centers in Sr2TiO4

A series of strontium orthotitanate (Sr₂TiO₄) samples doped with 2% of a mole of europium, praseodymium, and erbium were obtained using the solid-state synthesis method. The X-ray diffraction (XRD) technique confirms the phase purity of all samples and the lack of the influence of dopants at a given concentration on the structure of materials. The optical properties indicate, in the case of Sr₂TiO₄:Eu³⁺, two independent emission (PL) and excitation (PLE) spectra attributed to the Eu³⁺ ions at sites with different symmetries: low - excited at 360 nm and high - excited at 325 nm, while, for Sr₂TiO₄:Er³⁺ and Sr₂TiO₄:Pr³⁺, the emission spectra do not depend on the excitation wavelength. The measurements of X-ray photoemission spectroscopy (XPS) indicate the presence of only one type of charge compensation mechanism, which is based on the creation of strontium vacancies in all cases. This suggests that the different charge compensation mechanisms cannot easily explain the presence of Eu³⁺ at two non-equivalent crystal sites. The photocurrent excitation (PCE) spectroscopy investigations, that have not been reported in the literature so far, show that among all the studied dopants, only Pr³⁺ can promote the electrons to the conduction band and give rise to electron conductivity. The results collected from the PLE and PCE spectra allowed us to find the location of the ground states of lanthanides(II)/(III) in the studied matrix.

Single Crystalline Films of Ce3+-Doped Y3MgxSiyAl5-x-yO12 Garnets: Crystallization, Optical, and Photocurrent Properties

This research focuses on LPE growth, and the examination of the optical and photovoltaic properties of single crystalline film (SCF) phosphors based on Ce³⁺-doped Y₃Mg_xSi_yAl_5-x-yO₁₂ garnets with Mg and Si contents in x = 0-0.345 and y = 0-0.31 ranges. The absorbance, luminescence, scintillation, and photocurrent properties of Y₃Mg_xSi_yAl_5-x-yO₁₂:Ce SCFs were examined in comparison with Y₃Al₅O₁₂:Ce (YAG:Ce) counterpart. Especially prepared YAG:Ce SCFs with a low (x, y < 0.1) concentration of Mg²⁺ and Mg²⁺-Si⁴⁺ codopants also showed a photocurrent that increased with rising Mg²⁺ and Si⁴⁺ concentrations. Mg²⁺ excess was systematically present in as-grown Y₃Mg_xSi_yAl_5-x-yO₁₂:Ce SCFs. The as-grown SCFs of these garnets under the excitation of α-particles had a low light yield (LY) and a fast scintillation response with a decay time in the ns range due to producing the Ce⁴⁺ ions as compensators for the Mg²⁺ excess. The Ce⁴⁺ dopant recharged to the Ce³⁺ state after SCF annealing at T > 1000 °C in a reducing atmosphere (95%N₂ + 5%H₂). Annealed SCF samples exhibited an LY of around 42% and similar scintillation decay kinetics to those of the YAG:Ce SCF counterpart. The photoluminescence studies of Y₃Mg_xSi_yAl_5-x-yO₁₂:Ce SCFs provide evidence for Ce³⁺ multicenter formation and the presence of an energy transfer between various Ce³⁺ multicenters. The Ce³⁺ multicenters possessed variable crystal field strengths in the nonequivalent dodecahedral sites of the garnet host due to the substitution of the octahedral positions by Mg²⁺ and the tetrahedral positions by Si⁴⁺. In comparison with YAG:Ce SCF, the Ce³⁺ luminescence spectra of Y₃Mg_xSi_yAl_5-x-yO₁₂:Ce SCFs greatly expanded in the red region. Using these beneficial trends of changes in the optical and photocurrent properties of Y₃Mg_xSi_yAl_5-x-yO₁₂:Ce garnets as a result of Mg²⁺ and Si⁴⁺ alloying, a new generation of SCF converters for white LEDs, photovoltaics, and scintillators could be developed.

Energetic structure of Sm3+ luminescence centers in Sr2TiO4

A luminescent material based on the strontium orthotitanate (Sr₂TiO₄) matrix doped with 1% of a mole of samarium was obtained using the typical solid-state synthesis method under a neutral atmosphere of nitrogen. The sample was investigated using powder X-ray diffraction (XRD) and several luminescence techniques to study the phase composition, luminescence properties as well as to determine the position of the energetic states of Sm³⁺ in relation to the valence and conduction bands of Sr₂TiO₄. The XRD result shows that the product of the synthesis is pure Sr₂TiO₄. From the PL spectra, it can be seen that the phosphor can be effectively excited at 409 and 342 nm to emit significantly different emission spectra. The luminescence obtained under 409 nm excitation is typical of Sm³⁺ in Sr₂TiO₄ and attributed to the nonsymmetrical luminescent center (A-center). In contrast, the luminescence obtained under excitation at 342 nm originates from the symmetrical center (B-center) and has not been reported in the literature so far. The presence of the two emission centers related to Sm³⁺ ions in the Sr₂TiO₄ matrix characterized by only one crystallographic site of Sr²⁺ was explained by considering the different ways of charge compensation: Sm³⁺ in the A-center via strontium vacancy (V''_sr), and Sm³⁺ in the B-center via Ti³⁺ (Ti'_Ti).

Chromium Ion Pair Luminescence: A Strategy in Broadband Near-Infrared Light-Emitting Diode Design

Portable near-infrared (NIR) light sources are in high demand for applications in spectroscopy, night vision, bioimaging, and many others. Typical phosphor designs feature isolated Cr³⁺ ion centers, and it is challenging to design broadband NIR phosphors based on Cr³⁺-Cr³⁺ pairs. Here, we explore the solid-solution series SrAl_11.88-xGa_xO₁₉:0.12Cr³⁺ (x = 0, 2, 4, 6, 8, 10, and 12) as phosphors featuring Cr³⁺-Cr³⁺ pairs and evaluate structure-property relations within the series. We establish the incorporation of Ga within the magentoplumbite-type structure at five distinct crystallographic sites and evaluate the effect of this incorporation on the Cr³⁺-Cr³⁺ ion pair proximity. Electron paramagnetic measurements reveal the presence of both isolated Cr³⁺ and Cr³⁺-Cr³⁺ pairs, resulting in NIR luminescence at approximately 650-1050 nm. Unexpectedly, the origin of broadband NIR luminescence with a peak within the range 740-820 nm is related to the Cr³⁺-Cr³⁺ ion pair. We demonstrate the application of the SrAl_5.88Ga₆O₁₉:0.12Cr³⁺ phosphor, which possesses an internal quantum efficiency of ∼85%, a radiant flux of ∼95 mW, and zero thermal quenching up to 500 K. This work provides a further understanding of spectral shifts in phosphor solid solutions and in particular the application of the magentoplumbites as promising next-generation NIR phosphor host systems.

Sex Differences in Lung Imaging and SARS-CoV-2 Antibody Responses in a COVID-19 Golden Syrian Hamster Model

In the coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more severe outcomes are reported in males than in females, including hospitalizations and deaths. Animal models can provide an opportunity to mechanistically interrogate causes of sex differences in the pathogenesis of SARS-CoV-2. Adult male and female golden Syrian hamsters (8 to 10 weeks of age) were inoculated intranasally with 105 50% tissue culture infective dose (TCID50) of SARS-CoV-2/USA-WA1/2020 and euthanized at several time points during the acute (i.e., virus actively replicating) and recovery (i.e., after the infectious virus has been cleared) phases of infection. There was no mortality, but infected male hamsters experienced greater morbidity, losing a greater percentage of body mass, developed more extensive pneumonia as noted on chest computed tomography, and recovered more slowly than females. Treatment of male hamsters with estradiol did not alter pulmonary damage. Virus titers in respiratory tissues, including nasal turbinates, trachea, and lungs, and pulmonary cytokine concentrations, including interferon-β (IFN-β) and tumor necrosis factor-α (TNF-α), were comparable between the sexes. However, during the recovery phase of infection, females mounted 2-fold greater IgM, IgG, and IgA responses against the receptor-binding domain of the spike protein (S-RBD) in both plasma and respiratory tissues. Female hamsters also had significantly greater IgG antibodies against whole-inactivated SARS-CoV-2 and mutant S-RBDs as well as virus-neutralizing antibodies in plasma. The development of an animal model to study COVID-19 sex differences will allow for a greater mechanistic understanding of the SARS-CoV-2-associated sex differences seen in the human population. IMPORTANCE Men experience more severe outcomes from coronavirus disease 2019 (COVID-19) than women. Golden Syrian hamsters were used to explore sex differences in the pathogenesis of a human isolate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). After inoculation, male hamsters experienced greater sickness, developed more severe lung pathology, and recovered more slowly than females. Sex differences in disease could not be reversed by estradiol treatment in males and were not explained by either virus replication kinetics or the concentrations of inflammatory cytokines in the lungs. During the recovery period, antiviral antibody responses in the respiratory tract and plasma, including to newly emerging SARS-CoV-2 variants, were greater in female than in male hamsters. Greater lung pathology during the acute phase combined with lower antiviral antibody responses during the recovery phase of infection in males than in females illustrate the utility of golden Syrian hamsters as a model to explore sex differences in the pathogenesis of SARS-CoV-2 and vaccine-induced immunity and protection.

Rubrene Thin Films with Viably Enhanced Charge Transport Fabricated by Cryo-Matrix-Assisted Laser Evaporation

Among organic semiconductors, rubrene (RB; C₄₂H₂₈) is of rapidly growing interest for the development of organic and hybrid electronics due to exceptionally long spin diffusion length and carrier mobility up to 20 cm²V⁻¹s⁻¹ in single crystals. However, the fabrication of RB thin films resembling properties of the bulk remains challenging, mainly because of the RB molecule’s twisted conformation. This hinders the formation of orthorhombic crystals with strong π–π interactions that support the band transport. In this work, RB films with a high crystalline content were fabricated by matrix-assisted laser evaporation and the associated structure, composition, and transport properties are investigated. Enhanced charge transport is ascribed to the crystalline content of the film. Spherulitic structures are observed on top of an amorphous RB layer formed in the initial deposition stage. In spherulites, orthorhombic crystals dominate, as confirmed by X-ray diffraction and the absorption and Raman spectra. Surprisingly, nanowires several microns in length are also detected. The desorption/ionization mass and X-ray photoelectron spectra consistently show minimal material decomposition and absence of RB peroxides. The observed carrier mobility up to 0.13 cm²V⁻¹s⁻¹, is close to the technologically accepted level, making these rubrene films attractive for spintronic and optoelectronic applications.

Formation and Near-Infrared Emission of CsPbI3 Nanoparticles Embedded in Cs4PbI6 Crystals

Cs₄PbI₆, as a rarely investigated member of the Cs₄PbX₆ (X is a halogen element) family, has been successfully synthesized at low temperatures, and the synthetic conditions have been optimized. Metal iodides such as LiI, KI, NiI₂, CoI₂, and ZnI₂, as additives, play an important role in enhancing the formation of the Cs₄PbI₆ microcrystals. ZnI₂ with the lowest dissociation energy is the most efficient additive to supply iodide ions, and its amount of addition has also been optimized. Strong red to near-infrared (NIR) emission properties have been detected, and its optical emission centers have been identified to be numerous embedded perovskite-type α-CsPbI₃ nanocrystallites (∼5 nm in diameter) based on investigations of temperature- and pressure-dependent photoluminescent properties. High-resolution transmission electron microscopy was used to detect these hidden nanoparticles, although the material was highly beam-sensitive and confirmed a "raisin bread"-like structure of the Cs₄PbI₆ crystals. A NIR mini-LED for the biological application has been successfully fabricated using as-synthesized Cs₄PbI₆ crystals. This work provides information for the future development of infrared fluorescent nanoscale perovskite materials.

Sex differences in lung imaging and SARS-CoV-2 antibody responses in a COVID-19 golden Syrian hamster model

In the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more severe outcomes are reported in males compared with females, including hospitalizations and deaths. Animal models can provide an opportunity to mechanistically interrogate causes of sex differences in the pathogenesis of SARS-CoV-2. Adult male and female golden Syrian hamsters (8-10 weeks of age) were inoculated intranasally with 10 ⁵ TCID ₅₀ of SARS-CoV-2/USA-WA1/2020 and euthanized at several time points during the acute (i.e., virus actively replicating) and recovery (i.e., after the infectious virus has been cleared) phases of infection. There was no mortality, but infected male hamsters experienced greater morbidity, losing a greater percentage of body mass, developing more extensive pneumonia as noted on chest computed tomography, and recovering more slowly than females. Treatment of male hamsters with estradiol did not alter pulmonary damage. Virus titers in respiratory tissues, including nasal turbinates, trachea, and lungs, and pulmonary cytokine concentrations, including IFNb and TNFa, were comparable between the sexes. However, during the recovery phase of infection, females mounted two-fold greater IgM, IgG, and IgA responses against the receptor-binding domain of the spike protein (S-RBD) in both plasma and respiratory tissues. Female hamsters also had significantly greater IgG antibodies against whole inactivated SARS-CoV-2 and mutant S-RBDs, as well as virus neutralizing antibodies in plasma. The development of an animal model to study COVID-19 sex differences will allow for a greater mechanistic understanding of the SARS-CoV-2 associated sex differences seen in the human population.

Broadband NaK2Li[Li3SiO4]4:Ce Alkali Lithosilicate Blue Phosphors

Phosphors with a rigid and symmetrical structure are urgently needed. The alkali lithosilicate family (A[Li₃SiO₄]) has been extensively studied with a narrow emission band due to its unique cuboid-coordinated environment and rigid structure. However, here we demonstrate for the first time Ce-doped NaK₂Li[Li₃SiO₄]₄ phosphors with a broad emission band, a high internal quantum efficiency (85.6%), and excellent thermal stability. Photoluminescence indicates the Ce's preference to occupy the Na⁺ site, leading to a strong blue color emission with peak maxima at 417 and 450 nm. Temperature- and pressure-dependent photoluminescence reveals thermal stability and a phase transition. Moreover, the X-ray absorption near-edge structure reveals the mixing of Ce³⁺ and Ce⁴⁺ in the materials; this result differs from that of Eu²⁺-doped A[Li₃SiO₄] phosphors. The charge compensation process is then proposed to explain this difference. This study not only provides insights into Ce-doped UCr₄C₄-type phosphors but also explains the charge compensation mechanism of the aliovalent doping process.

Study of persistent luminescence and thermoluminescence in SrSi2N2O2:Eu2+,M3+ (M = Ce, Dy, and Nd)

The process of persistent luminescence or glow-in-the-dark, the delayed emission of light of irradiated substances, has long fascinated researchers, who have made efforts to explain the underlying physical phenomenon as well as put it to practical use. However, persistent luminescence is an elusive and difficult process, both in terms of controlling or altering its properties, as well as providing a quantitative description. In this paper, we used SrSi₂N₂O₂:Eu²⁺ as a model persistent phosphor, characterized by the broad distribution of structural defects and exhibiting long-lasting Eu²⁺ luminescence that is visible for a few minutes after switching off UV light. We investigated the persistent luminescence process by two complementary methods, namely, thermoluminescence and temperature-dependent persistent luminescence decay measurements. Analysis of experimental data allowed us to determine the depth distribution of traps, and allowed us to distinguish two different mechanisms by which the emission is delayed. The first, the temperature-dependent mechanism, is related to trap activation, while the second, temperature-independent mechanism is related to carrier migration. Finally, we employed the strategy of the co-doping of the phosphor SrSi₂N₂O₂:Eu²⁺,M³⁺ (M = Ce, Nd, Dy) to modify the persistent luminescence properties.

Endovascular treatment of complex diseases of the thoracic aorta-10 years single centre experience

BACKGROUND

Introduction of invasive endovascular techniques constituted a real a breakthrough in the treatment of aortic aneurysm dissection and rupture. We assessed the effectiveness and safety of thoracic endovascular aortic repair (TEVAR) in patients with thoracic aortic pathologies.

METHODS

Between 2007 and 2017, 118 patients with thoracic aortic pathology underwent TEVAR. Among them, 20 (16.9%) patients required hybrid procedures. Stent grafts indication were thoracic aortic aneurysm in 46 (39.0%) patients, type B dissection in 68 (57.6%) patients and other indications in 4 (3.3%). Procedural success rate, in-hospital and late mortality and morbidity were evaluated.

RESULTS

The patients were followed-up for a mean of 55 months (range, 6-118 months). The technical success rate was 96%. Five patients died during the first 30 days after procedure (mortality 4.2%), four due to ischemic stroke followed by multi-organ failure and another one hemodynamically significant type I endoleak. Most of them were noted in the first years of our study. Five others died during post-discharged period. Four patients developed neurological complications, including stroke (n=2; 1.7%) and paraparesis (n=2; 1.7%). There were 6 (5.1%) primary (5 type I and 1 type II) and 3 (2.5%) secondary endoleaks (1 type I and 2 type III). Secondary interventions were required in 8 subjects. There was one case of stent collapse and two retrograde aortic dissection.

CONCLUSIONS

Treatment of descending aortic diseases by using stent graft implantation has become the method of choice, decreasing the risk of open surgery, especially in patients with severe clinical state and comorbidities. However, effectiveness and safety may be achieved by experience team.

Methylparaben-induced decrease in collagen production and viability of cultured human dermal fibroblasts

Parabens owing to their many advantageous properties are widely applied in cosmetics, food products and pharmaceuticals. However, recent research results have shown that they possess the ability to accumulate in the human body and exert many adverse effects. In this study, the impact of methylparaben (MP) as the most frequently used preservative in cosmetics, on human dermal fibroblasts and collagen production was evaluated. In cells treated with 0.01, 0.03 and 0.05% MP a dose-dependent decrease in collagen biosynthesis was revealed, which was positively correlated with the activity of prolidase responsible for the recovery of proline. Consequently, the concentration of total collagen secreted into the medium was markedly diminished. A similar reduction in expression of the major skin collagen type I at both the protein and mRNA level as well as collagen type III and VI at the mRNA level was also detected. The decrease in the collagen level may result not only from the reduced synthesis but also increased degradation owing to MP-induced activation of pro-MMP-2 (72 kDa). The increase in activity of MMP-2 (66 kDa) was accompanied by a reduction in the inhibitory activity of TIMP-2. In addition, an inhibitory effect of MP on cell survival and proliferation was revealed in this study. The increased expression and nuclear translocation of caspase-3 as well as increased Bax and decreased Bcl-2 expression may suggest MP-induced cell apoptosis. In summary, we have provided new data on the adverse effects of methylparaben on human dermal fibroblasts and the main structural protein of the skin. Further studies on the mechanisms responsible for its action are in progress. Copyright © 2017 John Wiley & Sons, Ltd.

Endovascular treatment of renal artery occlusion caused by aortic stentgraft migration

Renal function impairment during interventional procedures became a real clinical problem. Contrast related nephropathy is the most common cause of renal failure, however, the procedure-related technical troubles may cause unexpected renal dysfunction.Technical failure of EVAR resulting in acute renal dysfunction is presented. The postprocedural occlusion of the right renal artery was treated in chimney technique. Early reintervention allowed the kidney preservation and renal function restoration. It is impossible to avoid all the complications following treatment of aortic aneurysm, but they can be anticipated and comprehensively treated in collaboration with other specialists.

Patient radiation exposure during carotid artery stenting

Objectives

The main purpose of this study was to document the radiation doses to patients during carotid stenting.

Material and method

Fluoroscopy and exposure time, air kerma and dose-area product during carotid artery stenting in 160 patients were retrospectively reviewed with regard to body mass index, degree of stenosis and use of cerebral protection devices.

Results

Total air kerma was lower than 0.5 Gy in 80%, 0.5–1 Gy in 17% and higher than 1 Gy (maximum 1.2) in 3% of patients. Mean total dose-area product value for carotid stenting was 54 Gy cm2. The mean air kerma (fluoroscopy), air kerma (exposure), total air kerma and dose-area product (fluoroscopy), dose-area product (exposure), total dose-area product of patients with body mass index within the range 25–29.9 and with body mass index >30 were significantly increased compared to that of patients with body mass index 18–24.9 (H = 40.2, df = 2; p = 0.0000001 and p = 0.000003, respectively).

Conclusion

Carotid artery stenting is a relatively safe radiological procedure in terms of the radiation dose acquired by the patient. The main factors contributing to possible radiation overdosing are body mass index value and complexity of the carotid lesion. Proper preoperative planning in obese and complicated patients may reduce the fluoroscopy time and contribute to reduced dose acquisition.

Clinical factors increasing radiation doses to patients undergoing long-lasting procedures: abdominal stent-graft implantation

Background

An important negative factor of EVAR is the radiation acquired during long-lasting procedures. The aim of the study was to document the radiation doses of EVAR and to discuss potential reasons for prolongation of radiological procedures.

Material/Methods

Dose-area product (DAP) (Gy cm²) and air kerma (AK) (Gy) obtained during EVAR from 92 patients were analyzed retrospectively in regards to body mass index (BMI), angulations of aneurysm neck, length of aneurysm neck and occurrence of tortuosity of iliac arteries.

Results

Total AK for fluoroscopy differed significantly between normal BMI (373 mGy) and BMI 25–29.9 (1125 mGy) or BMI >30 (1085 mGy). Iliac artery tortuosities >45° and short aneurysm necks caused higher doses of total AK (1097 mGy and 1228 mGy, respectively) than iliac artery tortuosities <45° and long aneurysm necks (605 mGy and 720 mGy, respectively).

Conclusions

The main factors contributing to a high radiation dose being acquired by patients during EVAR are: BMI >25, tortuosity of iliac arteries >45° and short aneurysm necks.

Patients' radiation doses during thoracic stent-graft implantation: the problem of long-lasting procedures

BACKGROUND

This article investigates patient radiation doses during implantation of thoracic stent-graft. Aortic stengraft implantation can be disturbed by many factors, which, in turn, lead to prolongation of the procedure time and, as a consequence, increase the radiation dose.

METHODS

Measurements of radiation length (fluoroscopy and exposure), air kerma (AK) in grays, and dose-area product in grays·square centimeters were conducted simultaneously in 100 patients. The patients were analyzed retrospectively, regarding their body mass index (BMI), type of aneurysms, number of stent-graft parts, angulation of aorta, and coverage of the left subclavian artery.

RESULTS

Mean total dose-area product value for this kind of treatment was 361 Gy·cm2. This was caused by the fact that total mean AK was high for the cohort analyzed and reached 797 mGy. For 23 patients total AK was between 1 and 2 Gy, and for 3 it exceeded 2 Gy. In the remaining group, the maximal radiation dose was very high and exceeded 3 Gy. The total AK of patients with BMI within the range of 25 to 29.9 kg/m2 and with BMI greater than 30 kg/m2 significantly increased in comparison with the group of patients with BMI between 18 and 24.9 kg/m2 (p=0.00005 and 0.000001, respectively). During the study, a good correlation between AK and fluoroscopy time (r=0.6) and for AK (or dose-area product) and exposure time (r=0.66 or 0.81, respectively) was observed.

CONCLUSIONS

The main factors contributing to a high radiation dose being acquired by patients during thoracic stent-graft were BMI greater than 25 kg/m2, number of parts of the stent-graft, and angulation of the neck of aneurysm exceeding 60 degrees.

Dose-area product to patients during stent-graft treatment of thoracic and abdominal aortic aneurysms

This article is the first investigation that studies patient doses (air kerma and DAP) during digital subtraction angiography (DSA) for stent-graft treatment of both thoracic (TAAs) and abdominal (AAAs) aortic aneurysms. Fluoroscopy and exposure time, air kerma and dose-area product (DAP) were analyzed from 100 patients. In 41% of the analyzed patients total air kerma was between 1-2 Gy and for 7% exceeded 2 Gy. Median DAP values for fluoroscopy were 87.6 (TAAs) and 142.2 (AAAs) (Gy cm2) and for exposure 364.7 and 238.7 (Gy cm2), respectively. A 10-min prolongation of treatment causes about 83 Gy cm increase of DAP for fluoroscopy and 390 Gy cm for each 1 s of exposure. A good correlation between DAP and examination times was found for both exposure (r = 0.78) and fluoroscopy (r = 0.7). Moreover, sex was found to be a differential factor for DAP: DAP values for females were about 25% lower for both clinical procedures. For this kind of treatment the radiation doses were obtained for patients. Total air kerma in this kind of treatment for TAAs might be high and can even reach 4 Gy.

Dose-area product of patients undergoing digital subtraction angiography (DSA): abdominal aorta and lower limb examinations

Complex analysis of the fluoroscopy time, exposure time, air kerma values and dose-area product (DAP) has been carried out for a very large group of patients (655) undergoing digital subtraction angiography (DSA) for abdominal aorta and lower limb examinations. Measurements have been performed for 206 patients with intravenous (IV DSA) and 449 patients with intra-arterial (IA DSA) contrast administration. The results obtained by the two variations of the DSA technique have been compared. Median DAP values for fluoroscopy are 5.4 (IA DSA) and 3.2 (IV DSA) Gy cm and for exposure are 51.7 and 66.3 Gy cm2, respectively. A good correlation between the exposure time and DAP has been found for the two types of examinations: IA DSA (r = 0.78) and IV DSA (r = 0.8). However, the correlation of fluoroscopy time and DAP has been insignificant, and the correlation coefficient is 0.39 for IA DSA and 0.63 for IV DSA. The DAP and the time exposure ratio have been significant factors differentiating these two methods. In fluoroscopy patients obtained higher doses in IA DSA, while in exposure doses were higher in IV DSA. Measurements of DAP can be a simple and accurate method for estimation of the stochastic radiation risk to the patients.