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2.
Int J Radiat Oncol Biol Phys ; 106(3): 604-611, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-32014151

RESUMO

PURPOSE: Steep dose falloff outside of tumors is a hallmark of stereotactic radiosurgery (SRS) and radiation therapy (SRT). Dose gradient index (DGI) quantifies the dose drop off. Tables of DGIs versus target volumes have been published for body sites, but none is available for brain. This study recommends guidelines for DGIs for brain SRS/SRT treatments based on clinical CyberKnife (CK) cases. METHODS AND MATERIALS: Four hundred ninety-five plans for patients with central nervous system tumors treated with CK at our institution between March 2015 and May 2018 were analyzed. The CK treatment planning system MultiPlan was used for planning. SRS/SRT plans were stratified into 6 groups by tumor size (Group I [0-1 cm3], II [1.0-3.0 cm3], III [3.0-5.0 cm3], IV [5.0-10.0 cm3], V [10.0-15.0 cm3], and VI [15.0-40.0 cm3]). Ideal and minimally acceptable DGIs were determined for each size group. To evaluate the effect of target shape on DGI criteria, the plans were divided into 4 target shape groups: (1) homogeneous shape (circular), (2) adjacent to radiosensitive organs at risk (adjacent), (3) irregularly shaped (irregular), and (4) multiple target plans (multilesion). The mean for each target size group was defined as the ideal DGI. Minimally acceptable DGI criteria are specified to reject the lowest 10% of cases. RESULTS: The minimal acceptable DGIs were 83 (Group I), 72 (II), 65 (III), 58 (IV), 52 (V), and 35 (VI). The ideal DGI is designated to evaluate SRS/SRT plans for homogeneous circular lesions, whereas minimal DGI is chosen to assess the plans for irregular, adjacent to organs at risk, and multilesions. SRS/SRT plans with higher DGI values are correlated with lower irradiated normal tissue volumes. CONCLUSIONS: This study provides a table of DGIs for brain SRS/SRT treatments as a tool for assessing the quality of intracranial SRS/SRT plans. DGI guidelines support SRS/SRT planning that results in lower risk of radionecrosis.


Assuntos
Neoplasias Encefálicas/radioterapia , Órgãos em Risco/efeitos da radiação , Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Neoplasias Encefálicas/diagnóstico por imagem , Guias como Assunto , Humanos , Órgãos em Risco/diagnóstico por imagem , Tolerância a Radiação , Radiocirurgia/efeitos adversos , Dosagem Radioterapêutica , Radioterapia Conformacional/efeitos adversos , Espalhamento de Radiação
3.
Chem Commun (Camb) ; 56(11): 1717-1720, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31942593

RESUMO

A novel sensor array based on a (+)AuNP/AuNC nanocomposite was constructed for the selective discrimination of 10 types of Gram-negative bacteria (including 3 types of antibiotic-resistant strains) at a low concentration level of OD600 = 0.015. By recognizing the triple optical patterns of Gram-negative bacteria with the assistance of LDA, the sensor array is able to group the bacteria with respect to their species to each other.


Assuntos
Técnicas de Tipagem Bacteriana/métodos , Bactérias Gram-Negativas/isolamento & purificação , Nanopartículas Metálicas/química , Análise por Conglomerados , Análise Discriminante , Ouro/química , Bactérias Gram-Negativas/classificação , Bactérias Gram-Positivas/classificação , Bactérias Gram-Positivas/isolamento & purificação , Humanos , Nanocompostos/química , Espalhamento de Radiação , Espectrometria de Fluorescência , Urina/microbiologia , Vancomicina/química
4.
Int J Radiat Oncol Biol Phys ; 106(2): 440-448, 2020 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-31928642

RESUMO

PURPOSE: Recent studies suggest that ultrahigh-dose-rate, "FLASH," electron radiation therapy (RT) decreases normal tissue damage while maintaining tumor response compared with conventional dose rate RT. Here, we describe a novel RT apparatus that delivers FLASH proton RT (PRT) using double scattered protons with computed tomography guidance and provide the first report of proton FLASH RT-mediated normal tissue radioprotection. METHODS AND MATERIALS: Absolute dose was measured at multiple depths in solid water and validated against an absolute integral charge measurement using a Faraday cup. Real-time dose rate was obtained using a NaI detector to measure prompt gamma rays. The effect of FLASH versus standard dose rate PRT on tumors and normal tissues was measured using pancreatic flank tumors (MH641905) derived from the KPC autochthonous PanCa model in syngeneic C57BL/6J mice with analysis of fibrosis and stem cell repopulation in small intestine after abdominal irradiation. RESULTS: The double scattering and collimation apparatus was dosimetrically validated with dose rates of 78 ± 9 Gy per second and 0.9 ± 0.08 Gy per second for the FLASH and standard PRT. Whole abdominal FLASH PRT at 15 Gy significantly reduced the loss of proliferating cells in intestinal crypts compared with standard PRT. Studies with local intestinal irradiation at 18 Gy revealed a reduction to near baseline levels of intestinal fibrosis for FLASH-PRT compared with standard PRT. Despite this difference, FLASH-PRT did not demonstrate tumor radioprotection in MH641905 pancreatic cancer flank tumors after 12 or 18 Gy irradiation. CONCLUSIONS: We have designed and dosimetrically validated a FLASH-PRT system with accurate control of beam flux on a millisecond time scale and online monitoring of the integral and dose delivery time structure. Using this system, we found that FLASH-PRT decreases acute cell loss and late fibrosis after whole-abdomen and focal intestinal RT, whereas tumor growth inhibition is preserved between the 2 modalities.


Assuntos
Órgãos em Risco/efeitos da radiação , Terapia com Prótons/instrumentação , Lesões Experimentais por Radiação/prevenção & controle , Proteção Radiológica/instrumentação , Radioterapia Guiada por Imagem/instrumentação , Abdome/efeitos da radiação , Animais , Proliferação de Células/efeitos da radiação , Desenho de Equipamento/métodos , Estudos de Viabilidade , Feminino , Fibrose , Raios gama , Intestino Delgado/patologia , Intestino Delgado/efeitos da radiação , Camundongos , Camundongos Endogâmicos C57BL , Tratamentos com Preservação do Órgão/instrumentação , Tratamentos com Preservação do Órgão/métodos , Órgãos em Risco/patologia , Neoplasias Pancreáticas/radioterapia , Terapia com Prótons/métodos , Proteção Radiológica/métodos , Radiometria/métodos , Radioterapia Guiada por Imagem/métodos , Espalhamento de Radiação , Células-Tronco/efeitos da radiação , Tomografia Computadorizada por Raios X
5.
Br J Radiol ; 93(1107): 20190428, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31556333

RESUMO

Proton and ion beam therapy has been introduced in the Lawrence Berkeley National Laboratory in the mid-1950s, when protons and helium ions have been used for the first time to treat patients. Starting in 1972, the scientists at Berkeley also were the first to use heavier ions (carbon, oxygen, neon, silicon and argon ions). The first clinical ion beam facility opened in 1994 in Japan and since then, the interest in radiotherapy with light ion beams has been increasing slowly but steadily, with 13 centers in clinical operation in 2019. All these centers are using carbon ions for clinical application.The article outlines the differences in physical properties of various light ions as compared to protons in view of the application in radiotherapy. These include the energy loss and depth dose properties, multiple scattering, range straggling and nuclear fragmentation. In addition, the paper discusses differences arising from energy loss and linear energy transfer with respect to their biological effects.Moreover, the paper reviews briefly the existing clinical data comparing protons and ions and outlines the future perspectives for the clinical use of ions like oxygen and helium.


Assuntos
Radioterapia com Íons Pesados , Transferência Linear de Energia , Neoplasias/radioterapia , Terapia com Prótons , Absorção de Radiação , Algoritmos , Carbono/uso terapêutico , Hélio/uso terapêutico , Humanos , Oxigênio/uso terapêutico , Projetos Piloto , Radiobiologia , Dosagem Radioterapêutica , Espalhamento de Radiação
6.
Br J Radiol ; 93(1107): 20190578, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31868523

RESUMO

OBJECTIVES: Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy that combines the benefits of proton therapy with the remarkable normal tissue preservation observed with the use of submillimetric spatially fractionated beams. This promising technique has been implemented at the Institut Curie-Proton therapy centre (ICPO) using a first prototype of a multislit collimator. The purpose of this work was to develop a Monte Carlo-based dose calculation engine to reliably guide preclinical studies at ICPO. METHODS: The whole "Y1"-passive beamline at the ICPO, including pMBRT implementation, was modelled using the Monte Carlo GATE v. 7.0 code. A clinically relevant proton energy (100 MeV) was used as starting point. Minibeam generation by means of the brass collimator used in the first experiments was modelled. A virtual source was modelled at the exit of the beamline nozzle and outcomes were compared with dosimetric measurements performed with EBT3 gafchromic films and a diamond detector in water. Dose distributions were recorded in a water phantom and in rat CT images (7-week-old male Fischer rats). RESULTS: The dose calculation engine was benchmarked against experimental data and was then used to assess dose distributions in CT images of a rat, resulting from different irradiation configurations used in several experiments. It reduced computational time by an order of magnitude. This allows us to speed up simulations for in vivo trials, where we obtained peak-to-valley dose ratios of 1.20 ± 0.05 and 6.1 ± 0.2 for proton minibeam irradiations targeting the tumour and crossing the rat head. Tumour eradication was observed in the 67 and 22% of the animals treated respectively. CONCLUSION: A Monte Carlo dose calculation engine for pMBRT implementation with mechanical collimation has been developed. This tool can be used to guide and interpret the results of in vivo trials. ADVANCES IN KNOWLEDGE: This is the first Monte Carlo dose engine for pMBRT that is being used to guide preclinical trials in a clinical proton therapy centre.


Assuntos
Dosimetria Fotográfica/métodos , Método de Monte Carlo , Terapia com Prótons/métodos , Animais , Benchmarking , Masculino , Órgãos em Risco , Imagens de Fantasmas , Terapia com Prótons/instrumentação , Hipofracionamento da Dose de Radiação , Lesões por Radiação/prevenção & controle , Dosagem Radioterapêutica , Ratos , Ratos Endogâmicos F344 , Espalhamento de Radiação
7.
Talanta ; 206: 120228, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514892

RESUMO

The asymmetric flow field-flow fractionation (AF4) coupled on-line with elemental (inductively coupled plasma-mass spectrometry, ICP-MS) and molecular (fluorescence and UV) detection has been investigated as a powerful tool for the characterization of bioinorganic nano-conjugates. In this study, we described methods for the characterization of biotin-antibody complexes bioconjugated with streptavidin quantum dots (QDs-SA-b-Ab). Operating parameters of AF4 separation technique were optimized and two procedures are proposed using a channel thickness of 350 µm and 500 µm. The use of a 500 µm spacer allowed to achieve an efficient AF4 separation of the QDs-SA-b-Ab complexes from the excess of individual species used in the bioconjugation that was required for a proper characterization of the bioconjugates. Optimization of the AF4 allowed a separation resolution good enough to isolate the QDs-SA-b-Ab bioconjugates from the free excess of b-Ab and QD-SA. The efficiency of the bioconjugation process could be then calculated, obtaining a value of 86% for a 1 QDs-SA: 5 b-Ab bioconjugation ratio. In addition, sample recovery around 90% was achieved.


Assuntos
Pontos Quânticos/análise , Água/química , Anticorpos/química , Biotina/química , Compostos de Cádmio/análise , Compostos de Cádmio/química , Fluorescência , Fracionamento por Campo e Fluxo/métodos , Limite de Detecção , Espectrometria de Massas/métodos , Pontos Quânticos/química , Espalhamento de Radiação , Compostos de Selênio/análise , Compostos de Selênio/química , Estreptavidina/química , Sulfetos/análise , Sulfetos/química , Compostos de Zinco/análise , Compostos de Zinco/química
8.
Radiol Med ; 124(12): 1281-1295, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31792703

RESUMO

The physical principles of dual-energy computed tomography (DECT) are as old as computed tomography (CT) itself. To understand the strengths and the limits of this technology, a brief overview of theoretical basis of DECT will be provided. Specific attention will be focused on the interaction of X-rays with matter, on the principles of attenuation of X-rays in CT toward the intrinsic limits of conventional CT, on the material decomposition algorithms (two- and three-basis-material decomposition algorithms) and on effective Rho-Z methods. The progresses in material decomposition algorithms, in computational power of computers and in CT hardware, lead to the development of different technological solutions for DECT in clinical practice. The clinical applications of DECT are briefly reviewed in relation to the specific algorithms.


Assuntos
Algoritmos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tecnologia Radiológica/métodos , Tomografia Computadorizada por Raios X/métodos , Feminino , Humanos , Masculino , Espalhamento de Radiação , Raios X
9.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 75(12): 1420-1425, 2019.
Artigo em Japonês | MEDLINE | ID: mdl-31866640

RESUMO

In radiography with anti-scatter grid, it is important to make sure that the X-ray beam direct exactly perpendicular to the grid plane. However, it is so difficult to ensure in mobile radiography. An optical sight to ensure X-ray alignment in mobile radiography with anti-scatter grid was devised. The device measures the X-ray beam angle respect to the grid plane by utilizing collimator-lamp. Computed radiography of water phantom on inclined bedding with anti-scatter grid (6 : 1) were done by aid of devised optical sight 20 times. The result showed that the average alignment error of the radiographies by aid of devised optical sight was within 1°, and the maximum error was<2°.


Assuntos
Invenções , Intensificação de Imagem Radiográfica , Imagens de Fantasmas , Radiografia , Radiografia Torácica , Espalhamento de Radiação , Raios X
10.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 75(12): 1426-1436, 2019.
Artigo em Japonês | MEDLINE | ID: mdl-31866641

RESUMO

In monitor unit (MU) independent verification by calculation for irregular field (MLC field) using multileaf collimator in X-ray therapy, it has become common to use collimator scatter factor (Sc) and phantom scatter factor (Sp) instead of total scatter factor (Sc, p). It is usually expressed as Sc, p (A)=Sc (A)×Sp (A), and the field size A is considered but the depth d is not. Sc is data of in-air output, and measure with a mini-phantom at constant depth to remove electron contamination. On the other hand, Sp is obtained from measurement data of Sc, p and Sc, and can be expressed as Sc, p (d, A)=Sc (constant depth, A)×Sp (d, A) at an arbitrary depth d, thus Sp depends on the depth of Sc, p. Therefore, Sp needs to consider depth. In addition, a linear accelerator equipped with the tertiary MLC has two field sizes, that are collimator field by upper and lower collimators and MLC field by tertiary MLC below them. In MU independent verification by calculation, it is often used that the estimated value of Sp obtained by converting MLC field to equivalent square field and referring to data of Sp in square field. To convert the MLC field to equivalent square field, a conversion formula from sector radius r to equivalent square field L by Clarkson's sector integration (Clarkson method) is used. In this study, using 24 types of MLC fields to evaluate estimation accuracy due to the difference of conversion formula in Clarkson method, we estimated value of Sp using r=0.5611L of B-Clarkson method and using r=0.5580L of A-Clarkson method. And the difference with the measured value of Sp obtained by measuring Sc, p and Sc in the same MLC fields was compared. While, to evaluate estimation accuracy due to the different depths using these Clarkson methods, the difference between estimated value and measured value of Sp similarly obtained at depth of 5, 10 and 15 cm was compared. As results, estimated value of Sp using A-Clarkson method than using B-Clarkson method was close to measured value, and it was the same trend at depth of 5, 10 and 15 cm. Therefore, it was suggested that estimation accuracy of Sp by A-Clarkson method is higher than B-Clarkson method when verifying beams with different depths in MU independent verification by calculation for MLC field.


Assuntos
Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador , Espalhamento de Radiação , Fator de Crescimento de Hepatócito , Radiometria , Dosagem Radioterapêutica
12.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 75(11): 1297-1307, 2019.
Artigo em Japonês | MEDLINE | ID: mdl-31748455

RESUMO

PURPOSE: When working on fluoroscopy and patient assistance in a healthcare facility, workers need to understand how to properly protect scattered radiation. In this study, we examined a four-dimensional visualization method to make it easy to understand the spread of scattered radiation visually, and proposed its application to radiation protection education. METHODS: We constructed the X-ray room, X-ray CT room, and angiography room using Particle Heavy Ion Transport code System (PHITS), and calculated the scattered radiation distribution when the patient was irradiated with X-rays. The three-dimensional distribution of each moment was continuously displayed to create a four-dimensional distribution. Using the created data, we conducted radiation protection education including exercises to make the students confirm the scatter distribution from any direction. The effectiveness of the scattered radiation visualization data was evaluated by a questionnaire. RESULTS: The position of assistance for standing chest radiograph was less scattered radiation at the side and below the patient. As a result of the questionnaire, this education has confirmed the effect of attracting attention about radiation protection. The fourdimensional visualization allowed students to understand the behavior of radiation and the source of scattered radiation. CONCLUSION: Visualization of three- and four-dimensional scattered radiation distribution in the radiological examination room can intuitively enhance the understanding of the invisible radiation spread and appropriate aids.


Assuntos
Proteção Radiológica , Realidade Virtual , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Espalhamento de Radiação
13.
Anal Chim Acta ; 1087: 121-130, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31585560

RESUMO

Protein misfolding and aggregation are the common mechanisms in a variety of aggregation-dependent diseases. The compromised proteins often assemble into toxic, accumulating amyloid-like structures of various lengths and their toxicity can also be transferred both in vivo and in vitro a prion-like behavior. The characterization of protein interactions, degradation and conformational dynamics in biological systems still represents an analytical challenge in the prion-like protein comprehension. In our work, we investigated the nature of a transferable cytotoxic agent, presumably a misfolded protein, through the coupling of a multi-detector, non-destructive separation platform based on hollow-fiber flow field-flow fractionation with imaging and downstream in vitro tests. After purification with ion exchange chromatography, the transferable cytotoxic agentwas analyzed with Atomic Force Microscopy and statistical analysis, showing that the concentration of protein dimers and low n-oligomer forms was higher in the cytotoxic sample than in the control preparation. To assess whether the presence of these species was the actual toxic and/or self-propagating factor, we employed HF5 fractionation, with UV and Multi-Angle Light Scattering detection, to define proteins molar mass distribution and abundance, and fractionate the sample into size-homogeneous fractions. These fractions were then tested individually in vitro to investigate the direct correlation with cytotoxicity. Only the later-eluted fraction, which contains high-molar mass aggregates, proved to be toxic onto cell cultures. Moreover, it was observed that the selective transfer of toxicity also occurs for one lower-mass fraction, suggesting that two different mechanisms, acute and later induced toxicity, are in place. These results strongly encourage the efficacy of this platform to enable the identification of protein toxicants.


Assuntos
Proteínas Amiloidogênicas/análise , Príons/análise , Agregados Proteicos , Proteínas Amiloidogênicas/isolamento & purificação , Proteínas Amiloidogênicas/toxicidade , Linhagem Celular Tumoral , Cromatografia por Troca Iônica , Fracionamento por Campo e Fluxo , Humanos , Luz , Microscopia de Força Atômica , Tamanho da Partícula , Príons/isolamento & purificação , Príons/toxicidade , Espalhamento de Radiação
14.
Environ Pollut ; 255(Pt 2): 113304, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31586909

RESUMO

Suitable methods and fit-for-purpose techniques are required to allow characterization of carbon-based nanomaterials (CB-NMs) in complex matrices. In this study, two methods were developed; a method for extraction and characterization of CB-NMs in biological media and a method for fractionation of natural organic matter (NOM) coated CB-NMs in environmental matrices. The former method was developed by extracting carbon nanotubes (CNTs: sized 0.75 × 3000 nm) and nanoplastics (sized 60, 200 and 600 nm) from eggshells and characterizing the extracted CB-NMs in terms of particle size distribution using asymmetrical flow field-flow fractionation (AF4) coupled with multi-angle light scattering (MALS). The latter method was developed using AF4-MALS to fraction NOM-coated CNT (sized 0.75 × 3000 nm) and nanoplastics (sized 60, 200 and 300 nm) in a simulated natural surface water and provide information about the size distribution of the CB-NM-NOM complexes. The developed AF4-MALS method successfully fractioned the CB-NM-NOM complexes based on hydrodynamic size and provided the size distribution of the complexes. The NOM corona did not shift significantly the median size of the CB-NMs. It influenced however the size distribution of the nanoplastics and CNTs. The sample preparation method failed to extract the CNTs (recovery < 20%) from the matrices of the eggshells while being successful for extracting the nanoplastics (recoveries > 60%). The AF4-MALS fractogram showed that the extraction method did not significantly influence the size distribution of the nanoplastics of 60 and 200 nm size, whereas the peak of 600 nm nanoplastics shifted towards a smaller hydrodynamic size. In conclusion, the developed sample preparation method followed by the developed AF4-MALS method can be applied for extraction, separation and characterization of CB-NMs in biological and environmental matrices. Thus, the methods have a high potential to be methods of choice to investigate CB-NMs in future studies.


Assuntos
Monitoramento Ambiental , Nanotubos de Carbono/química , Plásticos/química , Fracionamento por Campo e Fluxo , Luz , Tamanho da Partícula , Espalhamento de Radiação , Água
15.
Sensors (Basel) ; 19(20)2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31600932

RESUMO

Immunoassays have been widely used in scientific research and clinical diagnosis due to their versatile detection capability and high specificity. Immunoagglutination assays are kinds of immunoassay, which can simply and rapidly measure the concentration of analytes. In this work, we developed a low-cost micro-volume nephelometric system for quantitative immunoagglutination assays. We used off-the-shelf components to build the system, and the total cost of key components is only about 20 US dollars. The total detection volume in our system was as low as 3 µL, which could significantly reduce the reagent cost and required sample volume. We further evaluated the system performance via the immunoagglutination assay to measure the concentration of C-reactive protein, a plasma protein with levels rising in response to inflammation. The results demonstrated that our system could measure the concentration of analytes with relatively high sensitivity and precision within four minutes, and has high potential to be applied for clinical diagnostic tests.


Assuntos
Testes de Aglutinação/economia , Custos e Análise de Custo , Imunoensaio/economia , Nefelometria e Turbidimetria/economia , Proteína C-Reativa/análise , Humanos , Imagem Tridimensional , Espalhamento de Radiação
16.
Mol Biotechnol ; 61(11): 860-872, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31531759

RESUMO

Angiogenesis is a biological process finely tuned by a plethora of pro- and anti-angiogenic molecules, among which vascular endothelial growth factors (VEGFs). Their biological activity is expressed through the interaction with three cognate receptor tyrosine kinases, VEGFR1, 2, and 3. VEGFR2 is the primary regulator of angiogenesis. Ligand-induced VEGFR2 dimerization and activation depend on direct ligand binding to extracellular domains 2 and 3 of receptor and in the establishment of interactions between proximal membrane domains. VEGFR2 domain 7 has been shown to play a crucial role in receptor dimerization and regulation, therefore, representing a convenient target for the allosteric modulation of VEGFR2 activity. The ability to prepare a functional VEGFR2D7 domain represents the starting point to the development of novel VEGFR2 binders acting as allosteric inhibitors of receptor activity. Here, we describe a robust and efficient procedure for the preparation in E. coli of the VEGFR2 domain 7. The protein was obtained with a good yield and was properly folded. It was investigated in a biochemical and structural study, providing information on its conformational arrangement and in solution properties.


Assuntos
Receptor 2 de Fatores de Crescimento do Endotélio Vascular/biossíntese , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/genética , Regulação Alostérica , Dicroísmo Circular , Escherichia coli/metabolismo , Espectroscopia de Ressonância Magnética , Domínios Proteicos/genética , Dobramento de Proteína , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Espalhamento de Radiação , Espectrometria de Fluorescência , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/química , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/isolamento & purificação
17.
Artigo em Japonês | MEDLINE | ID: mdl-31548465

RESUMO

OBJECTIVES: The aim of this study was to evaluate an influence of post-processing scatter correction in portable abdominal radiography using a low ratio anti-scatter grid (grid). METHODS: To assess tube voltage on portable abdominal radiography, a burger phantom was used to measure for inverse of image quality figure (IQFinv). For evaluation of the influence on using or not the grid, IQFinv were measured. Abdominal phantom radiographies were assessed subjectively, in random order, by six radiologic technologists. The radiographies were performed without scatter correction [IG (-)] and with scatter correction at equivalent for grid ratio 6 [IG (6)] and 8 [IG (8)]. RESULTS: There was no significant decrease in IQFinv with 75 and 80 kV in comparison of 70 kV. Even processing scatter correction, IQFinv with using the grid was significantly higher than that without using the grid. The ability to detect nasogastric tube and stomach gas were significantly better in the scatter correction. Deviation index for IG (6) and IG (8) were significantly lower than that of IG (-). DISCUSSION: Portable abdominal radiographies will be improved image quality by utilizing scatter correction, although, it is necessary to consider the scatter correction processing as this may significant decrease deviation index in the practical situation. CONCLUSION: The post-processing scatter correction should be useful for detection nasogastric tube and stomach gas in portable abdominal radiography.


Assuntos
Intensificação de Imagem Radiográfica , Radiografia Abdominal , Humanos , Imagens de Fantasmas , Radiografia Abdominal/métodos , Radiografia Torácica , Distribuição Aleatória , Espalhamento de Radiação
18.
Appl Opt ; 58(24): 6519-6527, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31503580

RESUMO

We analyze theoretically the effectiveness of homogeneous layer approximations in modeling localized surface plasmon resonance biosensors made of spherical metal nanoparticles coated with biomolecular layers that have radially variable refractive indices. Using an extended Mie theory, we compute the extinction spectrum and peak wavelength of the system and compare them with when effective medium approximations are applied to treat the biomolecular layer as homogeneous. We investigate how the accuracies of the approximations depend on the geometric parameters of the system and the material of the metal nanoparticle. We also derive expressions that can be used to predict if the approximations would accurately predict the spectral position of the peak wavelength.


Assuntos
Algoritmos , Ressonância de Plasmônio de Superfície , Ouro/química , Nanopartículas Metálicas/química , Refratometria , Espalhamento de Radiação , Prata/química
19.
Phys Med ; 65: 157-166, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31494369

RESUMO

Dosimetry protocols for superficial X-rays prescribe the determination of kerma on the surface of a phantom through the use of a backscatter factor (Bw) that accounts for the effect of phantom scatter. Bw values corresponding to full-scatter phantoms are provided by these protocols. In practice, clinical situations arise wherein there is insufficient scattering material downstream, resulting in published Bw values that overestimate the amount of occurring scatter. To provide an accurate dose calculation the backscatter values need to be corrected for any reduction in scattered radiation. Estimating the change of Bw in situations with incomplete backscatter has previously been achieved by direct measurements or Monte Carlo modelling. For increasing the accuracy of clinical dosimetries, we developed a physical model to deduce an algorithm for calculating backscatter factors in situations with reduced downstream scattering medium. The predictions of the model were validated by comparison with published data, Monte Carlo simulations and film-based measurements for beams with a half-value layer of 0.8, 2 and 4 mm Al. Our algorithm accurately predicts the effect of partial scatter conditions with suitable precision. Its reliability, combined with the simplicity of calculation, makes this methodology suitable to be incorporated into routine clinical dosimetry. The algorithm's underlying physical model provides an intuitive understanding of the effects of field size and beam energy on backscatter reduction, permitting a rational management of this effect.


Assuntos
Algoritmos , Método de Monte Carlo , Espalhamento de Radiação , Terapia por Raios X , Imagens de Fantasmas , Radiometria
20.
J Synchrotron Radiat ; 26(Pt 5): 1432-1447, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31490131

RESUMO

The European X-ray Free-Electron Laser (EuXFEL) delivers extremely intense (>1012 photons pulse-1 and up to 27000 pulses s-1), ultrashort (<100 fs) and transversely coherent X-ray radiation, at a repetition rate of up to 4.5 MHz. Its unique X-ray beam parameters enable novel and groundbreaking experiments in ultrafast photochemistry and material sciences at the Femtosecond X-ray Experiments (FXE) scientific instrument. This paper provides an overview of the currently implemented experimental baseline instrumentation and its performance during the commissioning phase, and a preview of planned improvements. FXE's versatile instrumentation combines the simultaneous application of forward X-ray scattering and X-ray spectroscopy techniques with femtosecond time resolution. These methods will eventually permit exploitation of wide-angle X-ray scattering studies and X-ray emission spectroscopy, along with X-ray absorption spectroscopy, including resonant inelastic X-ray scattering and X-ray Raman scattering. A suite of ultrafast optical lasers throughout the UV-visible and near-IR ranges (extending up to mid-IR in the near future) with pulse length down to 15 fs, synchronized to the X-ray source, serve to initiate dynamic changes in the sample. Time-delayed hard X-ray pulses in the 5-20 keV range are used to probe the ensuing dynamic processes using the suite of X-ray probe tools. FXE is equipped with a primary monochromator, a primary and secondary single-shot spectrometer, and a timing tool to correct the residual timing jitter between laser and X-ray pulses.


Assuntos
Lasers , Fotoquímica/instrumentação , Espectrometria por Raios X/instrumentação , Calibragem , Desenho de Equipamento , Fótons , Espalhamento de Radiação , Raios X
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