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1.
J Agric Food Chem ; 67(41): 11408-11419, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31556290

RESUMO

In this study, the effects of 2-O-ß-d-glucopyranosyl-l-ascorbic acid (AA-2ßG), a natural ascorbic acid derivative from the fruits of Lycium barbarum, on treating the dextran sulfate sodium (DSS)-induced colitis in mice were investigated. The results revealed that AA-2ßG had palliating effects on DSS-induced inflammatory bowel disease (IBD) in terms of slowing down the trends of body weight and solid fecal mass loss, reducing colitis disease activity index, improving serum physiological and biochemical indicators, increasing colon length, blocking proinflammatory cytokines, and increasing tight junction proteins. Additionally, AA-2ßG treatment could promote the production of short-chain fatty acids and modulate the composition of the gut microbiota. The key bacteria related to IBD were found to be Porphyromonadaceae, Prevotellaceae, Rikenellaceae, Parasutterella, Parabacteroides, and Clostridium. The results indicated that AA-2ßG might treat IBD through the regulation of gut microbiota, suggesting that AA-2ßG has the potential to be used as a dietary supplement in the treatment of IBD.


Assuntos
Ácido Ascórbico/administração & dosagem , Colite/tratamento farmacológico , Microbioma Gastrointestinal/efeitos dos fármacos , Lycium/química , Extratos Vegetais/administração & dosagem , Animais , Ácido Ascórbico/química , Bactérias/classificação , Bactérias/efeitos dos fármacos , Bactérias/genética , Bactérias/isolamento & purificação , Colite/genética , Colite/imunologia , Colite/microbiologia , Citocinas/genética , Citocinas/imunologia , Sulfato de Dextrana/efeitos adversos , Modelos Animais de Doenças , Frutas/química , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação
2.
Med Image Anal ; 57: 136-148, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31302510

RESUMO

A new method is proposed to quantify the myocardial motion from both 2D C(ine)-MRI and T(agged)-MRI sequences. The tag pattern offers natural landmarks within the image that makes it possible to accurately quantify the motion within the myocardial wall. Therefore, several methods have been proposed for T-MRI. However, the lack of salient features within the cardiac wall in C-MRI hampers local motion estimation. Our method aims to ensure the local intensity and shape features invariance during motion through the iterative minimization of a cost function via a random walk scheme. The proposed approach is evaluated on realistic simulated C-MRI and T-MRI sequences. The results show more than 53% improvements on displacement estimation, and more than 24% on strain estimation for both C-MRI and T-MRI sequences, as compared to state-of-the-art cardiac motion estimators. Preliminary experiments on clinical data have shown a good ability of the proposed method to detect abnormal motion patterns related to pathology. If those results are confirmed on large databases, this would open up the possibility for more accurate diagnosis of cardiac function from standard C-MRI examinations and also the retrospective study of prior studies.

3.
Ecotoxicol Environ Saf ; 180: 202-207, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31096125

RESUMO

Fluoroquinolones (FQs) are extensively used in humans and animals, which have aroused wide attention due to the emergence of FQ resistant bacteria and frequent detection in water, sediment and organism. However, little information is available about the bioconcentration and tissue distribution of FQs in fish. In the present study, we investigated the uptake and depuration of eight FQs (balofloxacin (BAL), enoxacin (ENO), enrofloxacin (ENR), fleroxacin (FLE), lomefloxacin (LOM), moxifloxacin (MOX), ofloxacin (OFL), sparfloxacin (SPA)) in common carp under controlled laboratory conditions. The results showed that all target FQs could accumulate in fish tissues, and had a similar tendency over time during the whole uptake and depuration periods. The uptake rate constant (k1), depuration rate constant (k2) and half-lives (t1/2) were in the ranges of 0.007-3.599 L/(kg·d), 0.051-0.283 d-1 and 2.4-10.7 d, respectively. The ranges of bioconcentration factors (BCFs) were 0.24-39.55 L/kg, 0.21-24.97 L/kg and 0.04-1.07 L/kg in liver, kidney and muscle, respectively. BCFs of eight FQs decreased in the order: MOX > ENR > ENO ≈ BAL ≈ FLE ≈ OFL ≈ LOM ≈ SPA, which may be correlated with the substituents at positions 7 and 8 of the basic quinolone nucleus and the metabolic capacity. Besides, BCFs were relative with pH-adjusted distribution coefficient (log D), suggesting that molecular status of ionizable compounds strongly influenced the bioconcentration processes. The present study provides important insights for understanding the bioconcentration and tissues distribution of FQs.


Assuntos
Antibacterianos/farmacocinética , Carpas/metabolismo , Fluoroquinolonas/farmacocinética , Animais , Distribuição Tecidual
4.
MAGMA ; 32(4): 407-422, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30903326

RESUMO

OBJECTIVE: Diffusion tensor magnetic resonance imaging (DT-MRI, or DTI) is a promising technique for invasively probing biological tissue structures. However, DTI is known to suffer from much longer acquisition time with respect to conventional MRI and the problem is worsened when dealing with in vivo acquisitions. Therefore, faster DTI for both ex vivo and in vivo scans is highly desired. MATERIALS AND METHODS: This paper proposes a new compressed sensing (CS) reconstruction method that employs local low-rank (LLR) model and three-dimensional (3D) total variation (TV) constraint to reconstruct cardiac diffusion-weighted (DW) images from highly undersampled k-space data. The LLR model takes the set of DW images corresponding to different diffusion gradient directions as a 3D image volume and decomposes the latter into overlapping 3D blocks. Then, the 3D blocks are stacked as two-dimensional (2D) matrix. Finally, low-rank property is applied to each block matrix and the 3D TV constraint to the 3D image volume. The underlying constrained optimization problem is finally solved using the first-order fast method. The proposed method is evaluated on real ex vivo cardiac DTI data as a prerequisite to in vivo cardiac DTI applications. RESULTS: The results on real human ex vivo cardiac DTI images demonstrate that the proposed method exhibits lower reconstruction errors for DTI indices, including fractional anisotropy (FA), mean diffusivities (MD), transverse angle (TA), and helix angle (HA), compared to existing CS-based DTI image reconstruction techniques. CONCLUSION: The proposed method provides better reconstruction quality and more accurate DTI indices in comparison with the state-of-the-art CS-based DW image reconstruction methods.

5.
Med Biol Eng Comput ; 57(6): 1353-1366, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30790122

RESUMO

During robot-assisted percutaneous puncture surgery, a bevel-tipped needle is inserted into a fiber-structured soft tissue, which has transverse isotropic mechanical properties. Tissue rupture may lead to needle bending and insertion error. Therefore, analysis of the mechanics of rupture events in transverse isotropic space is essential for the precise control of needle motion. We analyzed the needle stiffness force and the cutting force, both related to rupture events, which are caused by contact deformation and tissue cutting, respectively. A modified model based on a homogeneous elastic half-space contact force model was used to describe the variation in the stiffness force of the needle. An energy-based maximum stiffness force model was proposed to predict the surface rupture for a needle that is inserted at different orientations. A model for the cutting force was presented based on a solid mechanics theory of unidirectional fiber-reinforced composite material to analyze the effect of the needle tip pose on the cutting force. Experiments on porcine muscle confirmed that the stiffness force and the cutting force were clearly influenced by the insertion orientation angle. The developed models could predict the stiffness force and the cutting force during needle insertion into the transverse isotropic tissue. This method provides a foundation for predicting needle deflection in the transverse isotropic space. Graphical abstract Force modeling for needle insertion in transverse isotropic soft tissue.


Assuntos
Agulhas , Especificidade de Órgãos , Punções , Animais , Fenômenos Biomecânicos , Elasticidade , Modelos Teóricos , Suínos
6.
Artigo em Inglês | MEDLINE | ID: mdl-30402780

RESUMO

Vegetable and fruit waste (VFW) is becoming a heavy burden of municipal waste disposal because of its huge amount, but it is a potentially valuable resource that can be developed into high value products such as methane. Conventional anaerobic digestion processes are not suitable for solving the problem of easy acidification of VFW. Thus, a two-stage laboratory-scale anaerobic digestion system was assembled for waste reduction and biogas production of VFW in the mesophilic temperatures. The biphasic system consists of a 70-L leach bed reactor (LBR) and a 35-L continuous stirred tank reactor (CSTR). Water is sprinkled over the material to enhance the extraction process of acidification phase. The leachate was then transferred to the CSTR for biogas production. Batch digestion was lasted 120 h until no biogas was produced. Leachate with a volatile fatty acid (VFA) concentration of 7.6 g/L was obtained within 10 h. The results showed that overall 70.9% of the volatile solids (VS) was removed in the solid-phase system. Over 90% of VFAs were reduced in the methanogenic reactor, and it has been observed that the maximum biogas production rate was 51.26 mL/(d gVS). The maximum methane concentration in the produced biogas was 71%.

7.
Sci Rep ; 8(1): 3070, 2018 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-29449666

RESUMO

Forests play an important role as carbon sinks by sequestrating carbon through photosynthesis. Thinning treatments have large impacts on carbon storage, in addition to strengthening quality and quantity of plantations. This study analyzed the effects of different thinning treatments on carbon stocks in both individual trees and stands of Taiwania (Taiwania cryptomerioides) plantations. Repeated field measurements and allometric equations were used to calculate total C storage and sequestration rates of live trees. The results of this study showed that the total carbon stock of stands with thinning treatments was less than that of the non-thinned stands. The non-thinned 23-year old stands had an estimated carbon stock of 96.8 Mg C ha-1, which is higher than the carbon stock found in either medium- (84.1 Mg C ha-1) or heavily-thinned (74.7 Mg C ha-1) treatment plots of the same age. If the objective of Taiwania plantations was to store large amounts of carbon in the young growth stage, without regard to the initial rate of storage, a better option is no-thinning. However, the medium thinned forests seem to be more promising for carbon sequestration than the no-thinned forests if a longer period is considered.

8.
Phys Med Biol ; 62(21): 8197-8209, 2017 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-28914609

RESUMO

The aim of this work was to investigate the effect of multiple perfusion components on the pseudo-diffusion coefficient D * in the bi-exponential intravoxel incoherent motion (IVIM) model. Simulations were first performed to examine how the presence of multiple perfusion components influences D *. The real data of livers (n = 31), spleens (n = 31) and kidneys (n = 31) of 31 volunteers was then acquired using DWI for in vivo study and the number of perfusion components in these tissues was determined together with their perfusion fraction and D *, using an adaptive multi-exponential IVIM model. Finally, the bi-exponential model was applied to the real data and the mean, standard variance and coefficient of variation of D * as well as the fitting residual were calculated over the 31 volunteers for each of the three tissues and compared between them. The results of both the simulations and the in vivo study showed that, for the bi-exponential IVIM model, both the variance of D * and the fitting residual tended to increase when the number of perfusion components was increased or when the difference between perfusion components became large. In addition, it was found that the kidney presented the fewest perfusion components among the three tissues. The present study demonstrated that multi-component perfusion is a main factor that causes high variance of D * and the bi-exponential model should be used only when the tissues under investigation have few perfusion components, for example the kidney.


Assuntos
Imagem de Difusão por Ressonância Magnética/métodos , Processamento de Imagem Assistida por Computador/métodos , Movimento/fisiologia , Perfusão , Humanos , Rim , Fígado , Masculino , Baço
9.
EJNMMI Res ; 7(1): 11, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28130689

RESUMO

BACKGROUND: This study aimed to compare one state-of-the-art deep learning method and four classical machine learning methods for classifying mediastinal lymph node metastasis of non-small cell lung cancer (NSCLC) from 18F-FDG PET/CT images. Another objective was to compare the discriminative power of the recently popular PET/CT texture features with the widely used diagnostic features such as tumor size, CT value, SUV, image contrast, and intensity standard deviation. The four classical machine learning methods included random forests, support vector machines, adaptive boosting, and artificial neural network. The deep learning method was the convolutional neural networks (CNN). The five methods were evaluated using 1397 lymph nodes collected from PET/CT images of 168 patients, with corresponding pathology analysis results as gold standard. The comparison was conducted using 10 times 10-fold cross-validation based on the criterion of sensitivity, specificity, accuracy (ACC), and area under the ROC curve (AUC). For each classical method, different input features were compared to select the optimal feature set. Based on the optimal feature set, the classical methods were compared with CNN, as well as with human doctors from our institute. RESULTS: For the classical methods, the diagnostic features resulted in 81~85% ACC and 0.87~0.92 AUC, which were significantly higher than the results of texture features. CNN's sensitivity, specificity, ACC, and AUC were 84, 88, 86, and 0.91, respectively. There was no significant difference between the results of CNN and the best classical method. The sensitivity, specificity, and ACC of human doctors were 73, 90, and 82, respectively. All the five machine learning methods had higher sensitivities but lower specificities than human doctors. CONCLUSIONS: The present study shows that the performance of CNN is not significantly different from the best classical methods and human doctors for classifying mediastinal lymph node metastasis of NSCLC from PET/CT images. Because CNN does not need tumor segmentation or feature calculation, it is more convenient and more objective than the classical methods. However, CNN does not make use of the import diagnostic features, which have been proved more discriminative than the texture features for classifying small-sized lymph nodes. Therefore, incorporating the diagnostic features into CNN is a promising direction for future research.

10.
Phys Med Biol ; 61(24): 8640-8663, 2016 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-27880739

RESUMO

Cine-MRI is widely used for the analysis of cardiac function in clinical routine, because of its high soft tissue contrast and relatively short acquisition time in comparison with other cardiac MRI techniques. The gray level distribution in cardiac cine-MRI is relatively homogenous within the myocardium, and can therefore make motion quantification difficult. To ensure that the motion estimation problem is well posed, more image features have to be considered. This work is inspired by a method previously developed for color image processing. The monogenic signal provides a framework to estimate the local phase, orientation, and amplitude, of an image, three features which locally characterize the 2D intensity profile. The independent monogenic features are combined into a 3D matrix for motion estimation. To improve motion estimation accuracy, we chose the zero-mean normalized cross-correlation as a matching measure, and implemented a bilateral filter for denoising and edge-preservation. The monogenic features distance is used in lieu of the color space distance in the bilateral filter. Results obtained from four realistic simulated sequences outperformed two other state of the art methods even in the presence of noise. The motion estimation errors (end point error) using our proposed method were reduced by about 20% in comparison with those obtained by the other tested methods. The new methodology was evaluated on four clinical sequences from patients presenting with cardiac motion dysfunctions and one healthy volunteer. The derived strain fields were analyzed favorably in their ability to identify myocardial regions with impaired motion.


Assuntos
Algoritmos , Cardiopatias/patologia , Coração/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Imagem Cinética por Ressonância Magnética/métodos , Movimento/fisiologia , Contração Miocárdica/fisiologia , Idoso , Feminino , Coração/diagnóstico por imagem , Cardiopatias/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Cardiovasculares
11.
Magn Reson Med ; 76(5): 1594-1603, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27747940

RESUMO

PURPOSE: A generalized intravoxel incoherent motion (IVIM) model, called the GIVIM, was proposed to better account for complex perfusion present in the tissues having various vessels and flow regimes, such as the liver. THEORY AND METHODS: The notions of continuous pseudodiffusion variable as well as perfusion fraction density function were introduced to describe the presence of multiple perfusion components in a voxel. The mean and standard deviation of Gaussian perfusion fraction density function were then used to define two new parameters, the mean pseudodiffusivity ( D¯) and pseudodiffusion dispersion (σ). The GIVIM model was evaluated by testing whether or not it can reflect hepatic perfusion difference caused by flow-compensated imaging sequences having different diffusion times. Also, D¯ was compared with D* in the standard IVIM model. RESULTS: The values of both D* and D¯ decreased after flow compensation and further decreased when shortening diffusion time. D¯ exhibited reduced variance in comparison with D*. In addition, σ also showed its sensitivity to hepatic perfusion difference caused by the flow-compensated imaging sequences. CONCLUSION: The GIVIM model has the ability to better describe multicomponent perfusion without lengthening acquisition time and knowing in advance the number and/or the variety of perfusion components. Magn Reson Med 76:1594-1603, 2016. © 2015 International Society for Magnetic Resonance in Medicine.


Assuntos
Interpretação de Imagem Assistida por Computador/métodos , Circulação Hepática/fisiologia , Fígado/diagnóstico por imagem , Fígado/fisiologia , Angiografia por Ressonância Magnética/métodos , Modelos Biológicos , Algoritmos , Simulação por Computador , Humanos , Aumento da Imagem/métodos , Imagem Tridimensional/métodos , Fígado/irrigação sanguínea , Modelos Estatísticos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
12.
Technol Health Care ; 24 Suppl 2: S593-9, 2016 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-27163322

RESUMO

Diffusion tensor magnetic resonance (DTMR) imaging and diffusion tensor imaging (DTI) have been widely used to probe noninvasively biological tissue structures. However, DTI suffers from long acquisition times, which limit its practical and clinical applications. This paper proposes a new Compressed Sensing (CS) reconstruction method that employs joint sparsity and rank deficiency to reconstruct cardiac DTMR images from undersampled k-space data. Diffusion-weighted images acquired in different diffusion directions were firstly stacked as columns to form the matrix. The matrix was row sparse in the transform domain and had a low rank. These two properties were then incorporated into the CS reconstruction framework. The underlying constrained optimization problem was finally solved by the first-order fast method. Experiments were carried out on both simulation and real human cardiac DTMR images. The results demonstrated that the proposed approach had lower reconstruction errors for DTI indices, including fractional anisotropy (FA) and mean diffusivities (MD), compared to the existing CS-DTMR image reconstruction techniques.


Assuntos
Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Coração , Processamento de Imagem Assistida por Computador/métodos , Algoritmos , Humanos
13.
J Environ Biol ; 37(2): 305-12, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27097452

RESUMO

Extracellular polymer substance (EPS) is an important substance in sludge dewatering process and can be divided into slime, loosely bound EPS(LB-EPS) and tightly bound EPS(TB-EPS). The major components in different EPS layers in mechanical dewatered sludge (sample D) and sludge from thickening tank (sample U) were analyzed in the study. Results showed that, for all sludge samples, protein content in slime was much higher than that in LB-EPS and TB-EPS. In addition, from the results of total EPS content in four sludge samples (U: 98.68 mg gvss⁻¹, US (sample U+SDS): 135.27 mg gvss⁻¹, D:138.16 mg gvss⁻¹, DS:211.21 mg gvss⁻¹), it was found that sodium dodecyl sulfate (SDS) extracted more EPS content from sludge, which proved that SDS might cause substantial release of EPS, especially PN from sludge. Increase PS content in LB-EPS, and TB-EPS as addition of SDS, implied sensibility of cells in sludge to SDS. Differential Scanning Calorimetry found that bound water proportion in four different sludge samples ranged as follows: as D>DS>US>U. Results from other analytical techniques,such as FTIR and NMR, were also given the supported proof for the distribution changes of EPS and bound water.


Assuntos
Polímeros/química , Esgotos/química , DNA/química , Proteínas , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Eliminação de Resíduos Líquidos
14.
Phys Med Biol ; 61(5): 1888-903, 2016 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-26864039

RESUMO

Diffusion magnetic resonance imaging (dMRI) is a non-invasive method currently available for cardiac fiber tracking. However, accurate and efficient cardiac fiber tracking is still a challenge. This paper presents a probabilistic cardiac fiber tracking method based on particle filtering. In this framework, an adaptive sampling technique is presented to describe the posterior distribution of fiber orientations by adjusting the number and status of particles according to the fractional anisotropy of diffusion. An observation model is then proposed to update the weight of particles by rotating diffusion tensor from the primary eigenvector to a given fiber orientation while keeping the shape of the tensor invariant. The results on human cardiac dMRI show that the proposed method is robust to noise and outperforms conventional streamline and particle filtering techniques.


Assuntos
Algoritmos , Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Cardiopatias/patologia , Coração/fisiologia , Modelos Estatísticos , Anisotropia , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Reconhecimento Automatizado de Padrão/métodos , Rotação
15.
PLoS One ; 11(2): e0150161, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26919477

RESUMO

Orientation distribution functions (ODFs) are widely used to resolve fiber crossing problems in high angular resolution diffusion imaging (HARDI). The characteristics of the ODFs are often assessed using a visual criterion, although the use of objective criteria is also reported, which are directly borrowed from classic signal and image processing theory because they are intuitive and simple to compute. However, they are not always pertinent for the characterization of ODFs. We propose a more general paradigm for assessing the characteristics of ODFs. The idea consists in regarding an ODF as a three-dimensional (3D) point cloud, projecting the 3D point cloud onto an angle-distance map, constructing an angle-distance matrix, and calculating metrics such as length ratio, separability, and uncertainty. The results from both simulated and real data show that the proposed metrics allow for the assessment of the characteristics of ODFs in a quantitative and relatively complete manner.


Assuntos
Imagem de Tensor de Difusão/métodos , Processamento de Imagem Assistida por Computador/métodos , Animais , Encéfalo/anatomia & histologia , Simulação por Computador , Imagem de Tensor de Difusão/estatística & dados numéricos , Macaca/anatomia & histologia , Conceitos Matemáticos , Razão Sinal-Ruído
16.
Phys Med Biol ; 60(21): 8417-36, 2015 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-26464329

RESUMO

Diffusion tensor imaging and high angular resolution diffusion imaging are often used to analyze the fiber complexity of tissues. In these imaging techniques, the most commonly calculated metric is anisotropy, such as fractional anisotropy (FA), generalized anisotropy (GA), and generalized fractional anisotropy (GFA). The basic idea underlying these metrics is to compute the deviation from free or spherical diffusion. However, in many cases, the question is not really to know whether it concerns spherical diffusion. Instead, the main concern is to describe and quantify fiber complexity such as fiber crossing in a voxel. In this context, it would be more direct and effective to compute the deviation from a single fiber bundle instead of a sphere. We propose a new metric, called PEAM (PEAnut Metric), which is based on computing the deviation of orientation diffusion functions (ODFs) from a single fiber bundle ODF represented by a peanut. As an example, the proposed PEAM metric is used to classify intravoxel fiber configurations. The results on simulated data, physical phantom data and real brain data consistently showed that the proposed PEAM provides greater accuracy than FA, GA and GFA and enables parallel and complex fibers to be better distinguished.


Assuntos
Algoritmos , Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Anisotropia
17.
Comput Med Imaging Graph ; 46 Pt 3: 291-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26342757

RESUMO

Fiber tractography techniques in diffusion magnetic resonance imaging have become a primary tool for studying the fiber architecture of biological tissues both noninvasively and in vivo. Streamline tracking, as a simple and efficient tractography technique, is widely used to reconstruct fiber pathways. It is however very sensitive to noisy estimation of local fiber orientations. In this paper, we propose a bundle constrained streamline method to accurately reconstruct multifiber pathways. The method introduces neighboring fiber consistency constraint in the tracking process and reconstructs fiber pathways that have optimal tradeoff between consistency with local fiber orientation estimations and similarity with neighboring fiber segment orientations. Results on synthetic, physical phantom and real human brain DW images show that the proposed method allows regular fiber pathways to be reconstructed and outperforms existing techniques.


Assuntos
Algoritmos , Imagem de Tensor de Difusão/métodos , Interpretação de Imagem Assistida por Computador/métodos , Fibras Nervosas Mielinizadas/ultraestrutura , Reconhecimento Automatizado de Padrão/métodos , Substância Branca/anatomia & histologia , Humanos , Aumento da Imagem/métodos , Aprendizado de Máquina , Sensibilidade e Especificidade
18.
Biomed Opt Express ; 6(7): 2424-34, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-26203371

RESUMO

This paper proposes a multigrid inversion framework for quantitative photoacoustic tomography reconstruction. The forward model of optical fluence distribution and the inverse problem are solved at multiple resolutions. A fixed-point iteration scheme is formulated for each resolution and used as a cost function. The simulated and experimental results for quantitative photoacoustic tomography reconstruction show that the proposed multigrid inversion can dramatically reduce the required number of iterations for the optimization process without loss of reliability in the results.

19.
Eur J Radiol ; 84(2): 312-7, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25487819

RESUMO

OBJECTIVES: In clinical practice, image analysis is dependent on simply visual perception and the diagnostic efficacy of this analysis pattern is limited for mediastinal lymph nodes in patients with lung cancer. In order to improve diagnostic efficacy, we developed a new computer-based algorithm and tested its diagnostic efficacy. METHODS: 132 consecutive patients with lung cancer underwent (18)F-FDG PET/CT examination before treatment. After all data were imported into the database of an on-line medical image analysis platform, the diagnostic efficacy of visual analysis was first evaluated without knowing pathological results, and the maximum short diameter and maximum standardized uptake value (SUVmax) were measured. Then lymph nodes were segmented manually. Three classifiers based on support vector machine (SVM) were constructed from CT, PET, and combined PET-CT images, respectively. The diagnostic efficacy of SVM classifiers was obtained and evaluated. RESULTS: According to ROC curves, the areas under curves for maximum short diameter and SUVmax were 0.684 and 0.652, respectively. The areas under the ROC curve for SVM1, SVM2, and SVM3 were 0.689, 0.579, and 0.685, respectively. CONCLUSION: The algorithm based on SVM was potential in the diagnosis of mediastinal lymph nodes.


Assuntos
Fluordesoxiglucose F18 , Neoplasias Pulmonares/patologia , Linfonodos/diagnóstico por imagem , Linfonodos/patologia , Tomografia por Emissão de Pósitrons , Máquina de Vetores de Suporte , Tomografia Computadorizada por Raios X , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Feminino , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Metástase Linfática/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons/métodos , Curva ROC , Compostos Radiofarmacêuticos , Estudos Retrospectivos
20.
Opt Express ; 22(17): 20500-14, 2014 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-25321256

RESUMO

We present an analytical model of optical fluence for multiple cylindrical inhomogeneities embedded in an otherwise homogeneous turbid medium. The model is based on the diffusion equation and represents the optical fluence distribution inside and outside inhomogeneities as a series of modified Bessel functions. We take into account the interplay between cylindrical inhomogeneities by introducing new boundary conditions on the surface of inhomogeneities. The model is compared with the numerical solution of the diffusion equation with NIRFAST software. The fluences inside the inhomogeneities obtained by the two methods are in close agreement. This permits the use of the model as a forward model for quantitative photoacoustic imaging.

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