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1.
APL Bioeng ; 5(2): 026101, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33834156

RESUMO

Detection of early osteoarthritis to stabilize or reverse the damage to articular cartilage would improve patient function, reduce disability, and limit the need for joint replacement. In this study, we investigated nondestructive photon-processing spectral computed tomography (CT) for the quantitative measurement of the glycosaminoglycan (GAG) content compared to destructive histological and biochemical assay techniques in normal and osteoarthritic tissues. Cartilage-bone cores from healthy bovine stifles were incubated in 50% ioxaglate (Hexabrix®) or 100% gadobenate dimeglumine (MultiHance®). A photon-processing spectral CT (MARS) scanner with a CdTe-Medipix3RX detector imaged samples. Calibration phantoms of ioxaglate and gadobenate dimeglumine were used to determine iodine and gadolinium concentrations from photon-processing spectral CT images to correlate with the GAG content measured using a dimethylmethylene blue assay. The zonal distribution of GAG was compared between photon-processing spectral CT images and histological sections. Furthermore, discrimination and quantification of GAG in osteoarthritic human tibial plateau tissue using the same contrast agents were demonstrated. Contrast agent concentrations were inversely related to the GAG content. The GAG concentration increased from 25 µg/ml (85 mg/ml iodine or 43 mg/ml gadolinium) in the superficial layer to 75 µg/ml (65 mg/ml iodine or 37 mg/ml gadolinium) in the deep layer of healthy bovine cartilage. Deep zone articular cartilage could be distinguished from subchondral bone by utilizing the material decomposition technique. Photon-processing spectral CT images correlated with histological sections in healthy and osteoarthritic tissues. Post-imaging material decomposition was able to quantify the GAG content and distribution throughout healthy and osteoarthritic cartilage using Hexabrix® and MultiHance® while differentiating the underlying subchondral bone.

2.
Front Plant Sci ; 11: 159, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32174941

RESUMO

Breeding higher yielding forage species is limited by current manual harvesting and visual scoring techniques used for measuring or estimation of biomass. Automation and remote sensing for high throughput phenotyping has been used in recent years as a viable solution to this bottleneck. Here, we focus on using RGB imaging and deep learning for white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) yield estimation in a mixed sward. We present a new convolutional neural network (CNN) architecture designed for semantic segmentation of dense pasture and canopies with high occlusion to which we have named the local context network (LC-Net). On our testing data set we obtain a mean accuracy of 95.4% and a mean intersection over union of 81.3%, outperforming other methods we have found in the literature for segmenting clover from ryegrass. Comparing the clover/vegetation fraction for visual coverage and harvested dry-matter however showed little improvement from the segmentation accuracy gains. Further gains in biomass estimation accuracy may be achievable through combining RGB with complimentary information such as volumetric data from other sensors, which will form the basis of our future work.

3.
Org Lett ; 20(13): 3784-3787, 2018 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-29944380

RESUMO

This letter describes the one-step conversion of heteroatom-substituted potassium organotrifluoroborates (KRBF3) to metal monoorganoborohydrides (MRBH3) using alkali metal aluminum hydrides. The method tolerates a variety of functional groups, expanding MRBH3 diversity. Hydride removal with Me3SiCl in the presence of dimethylaminopyridine (DMAP) affords the organoborane·DMAP (RBH2·DMAP) adducts.

4.
J Appl Clin Med Phys ; 19(2): 287-297, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29411524

RESUMO

In this paper, we present a method that uses a combination of experimental and modeled data to assess properties of x-ray beam measured using a small-animal spectral scanner. The spatial properties of the beam profile are characterized by beam profile shape, the angular offset along the rotational axis, and the photon count difference between experimental and modeled data at the central beam axis. Temporal stability of the beam profile is assessed by measuring intra- and interscan count variations. The beam profile assessment method was evaluated on several spectral CT scanners equipped with Medipix3RX-based detectors. On a well-calibrated spectral CT scanner, we measured an integral count error of 0.5%, intrascan count variation of 0.1%, and an interscan count variation of less than 1%. The angular offset of the beam center ranged from 0.8° to 1.6° for the studied spectral CT scanners. We also demonstrate the capability of this method to identify poor performance of the system through analyzing the deviation of the experimental beam profile from the model. This technique can, therefore, aid in monitoring the system performance to obtain a robust spectral CT; providing the reliable quantitative images. Furthermore, the accurate offset parameters of a spectral scanner provided by this method allow us to incorporate a more realistic form of the photon distribution in the polychromatic-based image reconstruction models. Both improvements of the reliability of the system and accuracy of the volume reconstruction result in a better discrimination and quantification of the imaged materials.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador/métodos , Modelos Teóricos , Tomógrafos Computadorizados , Tomografia Computadorizada por Raios X/instrumentação , Tomografia Computadorizada por Raios X/métodos , Humanos
5.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 8): 1140-1142, 2017 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-28932423

RESUMO

The title compound, C19H17BF3P {alternative name: triphen-yl[(tri-fluoro-boran-yl)meth-yl]phosphanium}, was formed by the reaction of tri-phenyl-phosphine with potassium iodo-methyl-tri-fluoro-borate. The mol-ecule features a nearly staggered conformation along the P-C bond and a less than staggered conformation along the C-B bond. In the crystal, weak C-H⋯F hydrogen bonds between the meta-phenyl C-H groups and the tri-fluoro-borate B-F groups form chains of R22(16) rings along [100]. These chains are are further stabilized by weak C-H⋯π inter-actions. A weak intra-molecular C-H⋯F hydrogen bond is also observed.

6.
AJR Am J Roentgenol ; 209(5): 1088-1092, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28834448

RESUMO

OBJECTIVE: We aimed to determine whether multienergy spectral photon-counting CT could distinguish between clinically relevant calcium crystals at clinical x-ray energy ranges. Energy thresholds of 15, 22, 29, and 36 keV and tube voltages of 50, 80, and 110 kVp were selected. Images were analyzed to assess differences in linear attenuation coefficients between various concentrations of calcium hydroxyapatite (54.3, 211.7, 808.5, and 1169.3 mg/cm3) and calcium oxalate (2000 mg/cm3). CONCLUSION: The two lower concentrations of hydroxyapatite were distinguishable from oxalate at all energy thresholds and tube voltages, whereas discrimination at higher concentrations depended primarily on the energy thresholds used. Multienergy spectral photon-counting CT shows promise for distinguishing these calcium crystals.


Assuntos
Oxalato de Cálcio , Durapatita , Tomografia Computadorizada por Raios X , Imagens de Fantasmas , Fótons
7.
Australas Phys Eng Sci Med ; 40(2): 297-303, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28220403

RESUMO

Spectral computed tomography (CT) is an up and coming imaging modality which shows great promise in revealing unique diagnostic information. Because this imaging modality is based on X-ray CT, it is of utmost importance to study the radiation dose aspects of its use. This study reports on the implementation and evaluation of a Monte Carlo simulation tool using TOPAS for estimating dose in a pre-clinical spectral CT scanner known as the MARS scanner. Simulated estimates were compared with measurements from an ionization chamber. For a typical MARS scan, TOPAS estimated for a 30 mm diameter cylindrical phantom a CT dose index (CTDI) of 29.7 mGy; CTDI was measured by ion chamber to within 3% of TOPAS estimates. Although further development is required, our investigation of TOPAS for estimating MARS scan dosimetry has shown its potential for further study of spectral scanning protocols and dose to scanned objects.


Assuntos
Simulação por Computador , Método de Monte Carlo , Doses de Radiação , Radiometria/instrumentação , Tomografia Computadorizada por Raios X/instrumentação , Animais , Humanos , Íons , Camundongos , Imagens de Fantasmas , Polimetil Metacrilato/química , Raios X
8.
Eur Radiol ; 27(1): 384-392, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27165137

RESUMO

OBJECTIVES: To quantify iodine uptake in articular cartilage as a marker of glycosaminoglycan (GAG) content using multi-energy spectral CT. METHODS: We incubated a 25-mm strip of excised osteoarthritic human tibial plateau in 50 % ionic iodine contrast and imaged it using a small-animal spectral scanner with a cadmium telluride photon-processing detector to quantify the iodine through the thickness of the articular cartilage. We imaged both spectroscopic phantoms and osteoarthritic tibial plateau samples. The iodine distribution as an inverse marker of GAG content was presented in the form of 2D and 3D images after applying a basis material decomposition technique to separate iodine in cartilage from bone. We compared this result with a histological section stained for GAG. RESULTS: The iodine in cartilage could be distinguished from subchondral bone and quantified using multi-energy CT. The articular cartilage showed variation in iodine concentration throughout its thickness which appeared to be inversely related to GAG distribution observed in histological sections. CONCLUSIONS: Multi-energy CT can quantify ionic iodine contrast (as a marker of GAG content) within articular cartilage and distinguish it from bone by exploiting the energy-specific attenuation profiles of the associated materials. KEY POINTS: • Contrast-enhanced articular cartilage and subchondral bone can be distinguished using multi-energy CT. • Iodine as a marker of glycosaminoglycan content is quantifiable with multi-energy CT. • Multi-energy CT could track alterations in GAG content occurring in osteoarthritis.


Assuntos
Cartilagem Articular/diagnóstico por imagem , Glicosaminoglicanos/análise , Iodo/farmacocinética , Osteoartrite/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Meios de Contraste/farmacocinética , Dissecação , Humanos , Osteoartrite/patologia , Imagens de Fantasmas , Tíbia/diagnóstico por imagem
9.
MD Advis ; 3(2): 4-5, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21246908
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