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2.
JNMA J Nepal Med Assoc ; 59(240): 795-798, 2021 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-34508490

RESUMO

Intracanal separation of nickel titanium files hinders complete shaping, cleaning, and filling of the root canal system and ultimately influences the endodontic treatment outcome. In this case report, we presented a successful broken instrument retrieval from the middle third of the mesiobuccal root canal of tooth #30 with the assistance of cone-beam computed tomograpgy based preoperative computer-assisted simulation, micro-trepan bur and micro-tube from Micro-Retrieve & Repair system and dental operative microscope. The involved tooth was then successfully cleaned, shaped and obturated followed by coronal restoration. At the three-year follow-up, tooth #30 was asymptomatic and functioned well without radiographic changes. The present case provides an example to show the robustness of computer-assisted technology in dental procedures and to show how the combination of advanced techniques can facilitate root canal therapy.


Assuntos
Dente Molar , Preparo de Canal Radicular , Computadores , Humanos , Dente Molar/diagnóstico por imagem , Dente Molar/cirurgia , Tratamento do Canal Radicular , Tomografia
3.
Comput Intell Neurosci ; 2021: 3766877, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34531908

RESUMO

In the image reconstruction of the electrical capacitance tomography (ECT) system, the application of the total least squares theory transforms the ill-posed problem into a nonlinear unconstrained minimization problem, which avoids calculating the matrix inversion. But in the iterative process of the coefficient matrix, the ill-posed problem is also produced. For the effect on the final image reconstruction accuracy of this problem, combined with the principle of the ECT system, the coefficient matrix is targeted and updated in the overall least squares iteration process. The new coefficient matrix is calculated, and then, the regularization matrix is corrected according to the adaptive targeting singular value, which can reduce the ill-posed effect. In this study, the total least squares iterative method is improved by introducing the mathematical model of EIV to deal with the errors in the measured capacitance data and coefficient matrix. The effect of noise interference on the measurement capacitance data is reduced, and finally, the high-quality reconstructed images are calculated iteratively.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Capacitância Elétrica , Análise dos Mínimos Quadrados , Tomografia
4.
BMC Ophthalmol ; 21(1): 339, 2021 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-34544392

RESUMO

BACKGROUND: In vivo corneal biomechanics evaluation has been used to help screen early keratoconus in recent years. This study is to evaluate the value of a Scheimpflug-based biomechanical analyser combined with tomography in detecting subclinical keratoconus by distinguishing normal eyes from frank keratoconus (KC) and forme frusta keratoconus (FFKC) eyes in Chinese patients. METHODS: Study design: diagnostic test. This study included 31 bilateral frank keratoconus patients, 27 unilateral clinically manifesting keratoconus patients with very asymmetric eyes, and 79 control subjects with normal corneas. Corneal morphological and biomechanical parameters were measured using a Pentacam HR and a Corvis ST (OCULUS, Wetzlar, Germany). The diagnostic ability of computed parameters reflecting corneal biomechanical and morphological traits [including the Belin-Ambrósio deviation index (BAD_D), the Corvis biomechanical index (CBI) and the tomographic and biomechanical index (TBI)] was determined using receiver operating characteristic (ROC) curve analysis and compared by the DeLong test. Additionally, the area under the curve (AUC), the best cut-off values, and the Youden index for each parameter were reported. A novel corneal stiffness parameter, the stress-strain index (SSI), was also compared between KC, FFKC and normal eyes. RESULTS: Every morphological and biomechanical index analysed in this study was significantly different among KC, FFKC and normal eyes (P = 0.000). The TBI was most valuable in detecting subclinical keratoconus (FFKC eyes), with an AUC of 0.928 (P = 0.000), and both forms of corneal ectasia (FFKC and frank KC eyes), with an AUC of 0.966 (P = 0.000). The sensitivity and specificity of the TBI was 97.5 and 77.8 % in detecting FFKC and 97.5 and 89.7 % in detecting any KC, respectively, with a cut-off value of 0.375. The morphological index BAD_D and the biomechanical index CBI were also very useful in distinguishing eyes with any KC from normal eyes, with AUCs of 0.965 and 0.934, respectively. The SSI was significantly different between KC, FFKC and normal eyes (P = 0.000), indicating an independent decrease in corneal stiffness in KC eyes. CONCLUSIONS: The combination of a Scheimpflug-based biomechanical analyser and tomography could increase the accuracy in detecting subclinical keratoconus in Chinese patients. The TBI was the most valuable index for detecting subclinical keratoconus, with a high sensitivity and specificity. Evaluation of corneal biomechanical properties in refractive surgery candidates could be helpful for recognizing potential keratoconic eyes and increasing surgical safety.


Assuntos
Ceratocone , Fenômenos Biomecânicos , China/epidemiologia , Córnea , Topografia da Córnea , Humanos , Ceratocone/diagnóstico , Curva ROC , Tomografia
5.
Comput Biol Med ; 137: 104835, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34508976

RESUMO

The world is significantly affected by infectious coronavirus disease (covid-19). Timely prognosis and treatment are important to control the spread of this infection. Unreliable screening systems and limited number of clinical facilities are the major hurdles in controlling the spread of covid-19. Nowadays, many automated detection systems based on deep learning techniques using computed tomography (CT) images have been proposed to detect covid-19. However, these systems have the following drawbacks: (i) limited data problem poses a major hindrance to train the deep neural network model to provide accurate diagnosis, (ii) random choice of hyperparameters of Convolutional Neural Network (CNN) significantly affects the classification performance, since the hyperparameters have to be application dependent and, (iii) the generalization ability using CNN classification is usually not validated. To address the aforementioned issues, we propose two models: (i) based on a transfer learning approach, and (ii) using novel strategy to optimize the CNN hyperparameters using Whale optimization-based BAT algorithm + AdaBoost classifier built using dynamic ensemble selection techniques. According to our second method depending on the characteristics of test sample, the classifier is chosen, thereby reducing the risk of overfitting and simultaneously produced promising results. Our proposed methodologies are developed using 746 CT images. Our method obtained a sensitivity, specificity, accuracy, F-1 score, and precision of 0.98, 0.97, 0.98, 0.98, and 0.98, respectively with five-fold cross-validation strategy. Our developed prototype is ready to be tested with huge chest CT images database before its real-world application.


Assuntos
COVID-19 , Humanos , Redes Neurais de Computação , SARS-CoV-2 , Tomografia , Tomografia Computadorizada por Raios X
6.
Methods Enzymol ; 657: 365-383, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34353495

RESUMO

Photochromic proteins and photoswitching optoacoustics (OA) are a promising combination, that allows OA imaging of even small numbers of cells in whole live animals and thus can facilitate a more wide-spread use of OA in life-science and preclinical research. The concept relies on exploiting the modulation achieved by the photoswitching to discriminate the agents' signal from the non-modulating background. Here we share our analysis approaches that can be readily used on data generated with commercial OA tomography imaging instrumentation allowing-depending on the used photoswitching agent and sample-routine visualizations of as little as several hundreds of transgene labeled cells per imaging volume in the live animal.


Assuntos
Técnicas Fotoacústicas , Animais , Tomografia , Tomografia Computadorizada por Raios X
7.
Rev Assoc Med Bras (1992) ; 67(2): 297-301, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34406257

RESUMO

OBJECTIVE: COVID-19 can cause lung damage and may present with pneumonia in patients. In the present study, the correlation between the severity of pneumonia and electrocardiography parameters of COVID-19 were examined. METHODS: A total of 93 COVID-19 patients and a control group consisting of 62 volunteers were studied. Computed thorax tomography evaluation was performed; each lung was divided into three zones. For each affected zone, scores were given. The main computed thorax tomography patterns were described in line with the terms defined by the Fleischner Society and peer reviewed literature on viral pneumonia. We compared Computed thorax tomography of patients with corrected QT (QTc) and P wave dispersion (Pd) time. RESULTS: There is a significant difference between the patient and control groups in terms of QTc values (413.5±28.8 msec vs. 395.6±16.7 msec p<0.001). Likewise, the Pd value of the patient group is statistically significantly higher than that of the control group (50.0±9.6 ms computed thorax tomography ec vs. 41.3±5.8 msec p<0.001). In the patient group, a reverse correlation was detected between computed thorax tomography score and Pd value according to partial correlation coefficient analysis (correlation coefficient: -0.232, p=0.027). In the patient group, the correlation between computed thorax tomography score and QTc value was similarly determined according to partial correlation coefficient analysis (Correlation coefficient:0.224, p=0.017). CONCLUSIONS: COVID-19 prolongs QTc and P wave dispersion values; and as the severity of pneumonia increases, QTc value increases. However, whereas the severity of pneumonia increases, P wave dispersion value decreases.


Assuntos
COVID-19 , Eletrocardiografia , Humanos , SARS-CoV-2 , Tomografia
8.
Sensors (Basel) ; 21(16)2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34450940

RESUMO

In this paper, the possibility of using nonlinear ultrasonic guided waves for early-life material degradation in metal plates is investigated through both computational modeling and study. The analysis of the second harmonics of Lamb waves in a free boundary aluminum plate, and the internal resonance conditions between the Lamb wave primary modes and the second harmonics are investigated. Subsequently, Murnaghan's hyperelastic model is implemented in a finite element (FE) analysis to study the response of aluminum plates subjected to a 60 kHz Hanning-windowed tone burst. Different stages of material degradation are reflected as the changes in the third order elastic constants (TOECs) of the Murnaghan's model. The reconstructed degradations match the actual ones well across various degrees of degradation. The effects of several relevant factors on the accuracy of reconstructions are also discussed.


Assuntos
Ondas Ultrassônicas , Vibração , Animais , Simulação por Computador , Análise de Elementos Finitos , Ovinos , Tomografia
9.
Sensors (Basel) ; 21(16)2021 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-34451007

RESUMO

Non-destructive tests are strongly required in engineering applications for monitoring civil structures. The use of compared and integrated innovative approaches based on geophysical methodologies represents an effective tool for the characterization and monitoring of reinforced concrete (RC) structures. Therefore, the main aim of the work was to improve the knowledge on the potentiality and limitations of the Ground Penetrating Radar (GPR) and the Electrical Resistivity Tomography (ERT) with electrodes disposed both on the surface and in the boreholes. The work approach was adopted on an analog model of a reinforced concrete frame built ad hoc at the Hydrogeosite Laboratory (CNR-IMAA), where simulated experiments on full-size physical models are defined. Results show the ability of an accurate use of GPR to reconstruct the rebar dispositions and detect in detail possible constructive defects, both highlighting the lack of reinforcements into the nodes and providing useful information about the safety assessment of the realized structure. The results of the ERT method defined the necessity to develop ad-hoc electrical resistivity methods to support the characterization and monitoring of buried foundation structures for civil engineering applications. Finally, the paper introduces a new approach based on the use of cross-hole ERTs (CHERTs) for the engineering structure monitoring, able to reduce the uncertainties usually affecting the indirect results.


Assuntos
Laboratórios , Radar , Eletricidade , Tomografia
10.
Methods Enzymol ; 657: 301-330, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34353492

RESUMO

In this chapter, we highlight the advantages of multispectral optoacoustic tomography (MSOT) technique and the activatable photoacoustic probes in the biomedical field, and give a brief introduction to enzyme-activated probes for disease diagnosis and therapeutic outcome evaluation. We also present a detailed description of the procedures for the synthesis of an activatable small molecule probe C1X-OR1 and confirmation of its specific response to alkaline phosphatase in solution and cells. With MSOT, the liposomal C1X-OR1 can be utilized for detection of hepatic ALP as well as for in vivo diagnosis of drug-induced liver injury in a three-dimensional manner.


Assuntos
Doença Hepática Induzida por Substâncias e Drogas/diagnóstico por imagem , Técnicas Fotoacústicas , Fosfatase Alcalina , Fígado , Sondas Moleculares , Tomografia/métodos
11.
Sensors (Basel) ; 21(16)2021 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-34451077

RESUMO

Bedside imaging of ventilation and perfusion is a leading application of 2-D medical electrical impedance tomography (EIT), in which dynamic cross-sectional images of the torso are created by numerically solving the inverse problem of computing the conductivity from voltage measurements arising on electrodes due to currents applied on electrodes on the surface. Methods of reconstruction may be direct or iterative. Calderón's method is a direct reconstruction method based on complex geometrical optics solutions to Laplace's equation capable of providing real-time reconstructions in a region of interest. In this paper, the importance of accurate modeling of the electrode location on the body is demonstrated on simulated and experimental data, and a method of including a priori spatial information in dynamic human subject data is presented. The results of accurate electrode modeling and a spatial prior are shown to improve detection of inhomogeneities not included in the prior and to improve the resolution of ventilation and perfusion images in a human subject.


Assuntos
Algoritmos , Tomografia , Impedância Elétrica , Eletrodos , Humanos , Perfusão
12.
Theranostics ; 11(16): 7813-7828, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34335966

RESUMO

Non-invasive monitoring of hemodynamic tumor responses to chemotherapy could provide unique insights into the development of therapeutic resistance and inform therapeutic decision-making in the clinic. Methods: Here, we examined the longitudinal and dynamic effects of the common chemotherapeutic drug Taxotere on breast tumor (KPL-4) blood volume and oxygen saturation using eigenspectra multispectral optoacoustic tomography (eMSOT) imaging over a period of 41 days. Tumor vascular function was assessed by dynamic oxygen-enhanced eMSOT (OE-eMSOT). The obtained in vivo optoacoustic data were thoroughly validated by ex vivo cryoimaging and immunohistochemical staining against markers of vascularity and hypoxia. Results: We provide the first preclinical evidence that prolonged treatment with Taxotere causes a significant drop in mean whole tumor oxygenation. Furthermore, application of OE-eMSOT showed a diminished vascular response in Taxotere-treated tumors and revealed the presence of static blood pools, indicating increased vascular permeability. Conclusion: Our work has important translational implications and supports the feasibility of eMSOT imaging for non-invasive assessment of tumor microenvironmental responses to chemotherapy.


Assuntos
Neoplasias da Mama/metabolismo , Hemodinâmica/fisiologia , Tomografia Óptica/métodos , Animais , Neoplasias da Mama/diagnóstico por imagem , Linhagem Celular Tumoral , Docetaxel/farmacologia , Feminino , Hemodinâmica/efeitos dos fármacos , Humanos , Hipóxia/metabolismo , Camundongos , Camundongos SCID , Oxigênio/metabolismo , Técnicas Fotoacústicas/métodos , Tomografia/métodos , Tomografia Computadorizada por Raios X/métodos , Microambiente Tumoral/fisiologia
13.
Kyobu Geka ; 74(8): 606-609, 2021 Aug.
Artigo em Japonês | MEDLINE | ID: mdl-34334603

RESUMO

A 51-year-old man was diagnosed as having mitral valve regurgitation( MR). Transesophageal echocardiography revealed severe MR due to A2 prolapse. We decided to perform a mitral valve plasty (MVP). The length of an artificial chord was estimated by measuring the distance from the anterior and posterior papillary muscles to A2 on cardiac computed tomography (CT). The operation was performed with a median sternotomy. The leaflet prolapse lesion was localized in A2, and one torn chord was revealed. Polytetrafluoroethylene sutures were fixed to the papillary muscle, and markings were performed. After fixing the artificial chord to A2 in the predicted length before the operation, a leakage test was performed. We confirmed that the MR had disappeared. The postoperative course was good, and no MR was detected upon postoperative echocardiography. Preoperative prediction of the artificial chord length using cardiac CT is useful because it can be adjusted relatively easily.


Assuntos
Insuficiência da Valva Mitral , Prolapso da Valva Mitral , Cordas Tendinosas/diagnóstico por imagem , Cordas Tendinosas/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/diagnóstico por imagem , Valva Mitral/cirurgia , Insuficiência da Valva Mitral/diagnóstico por imagem , Insuficiência da Valva Mitral/cirurgia , Prolapso da Valva Mitral/diagnóstico por imagem , Prolapso da Valva Mitral/cirurgia , Politetrafluoretileno , Tomografia , Resultado do Tratamento
14.
World J Gastroenterol ; 27(27): 4441-4452, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34366615

RESUMO

BACKGROUND: Computed tomography colonography (CTC) may be superior to colonoscopy and barium enema for detecting diverticula. However, few studies have used CTC to diagnose diverticula. AIM: To evaluate the current prevalence and distribution of colonic diverticula in Japan using CTC. METHODS: This study was conducted as part of the Japanese National Computed Tomographic Colonography Trial, which included 1181 participants from 14 hospitals in Japan. We analyzed the prevalence and distribution of colonic diverticula and their relationships with age and sex. The relationship between the diverticula and the length of the large intestine was also analyzed. RESULTS: Diverticulosis was present in 48.1% of the participants. The prevalence of diverticulosis was higher in the older participants (P < 0.001 for trend). The diverticula seen in younger participants were predominantly located in the right-sided colon. Older participants had a higher frequency of bilateral type (located in the right- and left-sided colon) diverticulosis (P < 0.001 for trend). The length of the large intestine with multiple diverticula in the sigmoid colon was significantly shorter in those without diverticula (P < 0.001). CONCLUSION: The prevalence of colonic diverticulosis in Japan is higher than that previously reported. The prevalence was higher, and the distribution tended to be bilateral in older participants.


Assuntos
Colonografia Tomográfica Computadorizada , Diverticulose Cólica , Divertículo do Colo , Idoso , Colonoscopia , Diverticulose Cólica/diagnóstico por imagem , Diverticulose Cólica/epidemiologia , Divertículo do Colo/diagnóstico por imagem , Divertículo do Colo/epidemiologia , Humanos , Japão/epidemiologia , Prevalência , Tomografia
15.
Curr Cardiol Rep ; 23(9): 114, 2021 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-34269899

RESUMO

PURPOSE OF REVIEW: The field of transcatheter tricuspid valve interventions (TTVI) is rapidly evolving to meet a well-defined but unmet clinical need. Severe tricuspid regurgitation is common and is associated with significant morbidity and mortality. Surgical options are limited and of high risk. The success of TTVI depends on careful procedural planning, and cardiac computed tomography (CCT) plays an emerging key role. RECENT FINDINGS: TTVI technologies have various targets, including the leaflets, annulus, and venae cavae, along with valve replacement. Based on the planned procedure, CCT allows for device sizing, careful assessment of the access route, and comprehensive analysis of relevant adjacent anatomic structures to enhance procedural safety. It can also evaluate right-sided heart function, and its data can be for fusion imaging and 3D printing. Procedural planning is key to TTVI's success and is highly dependent on high-quality CCT data. This review details the comprehensive roles of CCT, specifics of the dedicated TTVI protocol, and its limitations.


Assuntos
Implante de Prótese de Valva Cardíaca , Insuficiência da Valva Tricúspide , Cateterismo Cardíaco , Humanos , Tomografia , Resultado do Tratamento , Valva Tricúspide/diagnóstico por imagem , Valva Tricúspide/cirurgia , Insuficiência da Valva Tricúspide/diagnóstico por imagem , Insuficiência da Valva Tricúspide/cirurgia
16.
Eur J Radiol ; 142: 109868, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34311155

RESUMO

PURPOSE: We explored the feasibility and reproducibility of cardiac computed tomography (CCT)-derived left ventricular (LV) global strain in postoperative childrenwith congenital heart disease (CHD) and compared its correlation and agreement with transthoracic echocardiography (TTE). METHODS: Fifty-one patients (28 males, 23 females) were included who underwent clinically indicated retrospective electrocardiography-triggered CCT. and all patients underwent additional TTE on the same day. LV global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) were measured. Correlations of global strains between CCT and TTE were assessed using Pearson's correlation coefficient. Intra-class correlation coefficients (ICC) were used to assess CCT intra-observer and inter-observer reproducibility. RESULTS: GLS and GCS were not significantly different between CCT and TTE (GLS: -23.54 ± 3.24 vs. -23.85 ± 3.72, respectively, p = 0.415; GCS: -28.21 ± 3.55 vs. -28.79 ± 3.69, respectively, p = 0.155). GRS was significantly different between CCT and TTE (60.79 ± 15.11 vs. 41.73 ± 4.27, respectively, p < 0.001). There was good correlation between CCT- and TTE-derived GLS (r = 0.70, p < 0.001) and GCS (r = 0.68, p < 0.001), but GRS showed no correlation between CCT and TTE (r = 0.09, p = 0.54). CCT-derived global strain showed good intra- and inter-observer reproducibility (ICC = 0.86-0.92), except the inter-observer reproducibility for GRS (ICC = 0.77). CONCLUSIONS: CCT was feasible for postoperative evaluation of LV global strain in pediatric patients with CHD with sufficient reproducibility. CCT-derived global strain can provide additional information in selected CHD patients with poor acoustic windows and who are intolerant to or have contraindications for cardiac magnetic resonance.


Assuntos
Cardiopatias Congênitas , Disfunção Ventricular Esquerda , Criança , Ecocardiografia , Feminino , Cardiopatias Congênitas/diagnóstico por imagem , Cardiopatias Congênitas/cirurgia , Humanos , Masculino , Reprodutibilidade dos Testes , Estudos Retrospectivos , Tomografia , Disfunção Ventricular Esquerda/diagnóstico por imagem , Função Ventricular Esquerda
17.
Comput Biol Med ; 135: 104592, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34214941

RESUMO

OBJECTIVE: Anti-gravity straining maneuver (AGSM) helps to reduce the occurrence of gravity-induced visual disturbances and loss of consciousness. An objective assessment of the AGSM is still missing during ground training. This study evaluated the feasibility of using electrical impedance tomography (EIT) to assess the performance of AGSM. METHODS: Eight undergraduates and eight teachers majoring in aerospace medicine were included in the study. An experienced professor from the department of aerospace medicine reviewed the key points of AGSM with each subject. EIT measurement was performed during AGSM. The global and regional ventilation were used to investigate the characteristics of AGSM. The professor and the subjects rated the performance of AGSM according to the maneuver requirements of AGSM (maximum 16 points) before and after reviewing the ventilations from EIT. RESULTS: For global ventilation, the relative depth of gas exchange and duration of exhalation of the teachers were larger than those of the students (p < 0.01), and stability of the teachers was better as well (p < 0.001). No difference in the duration of gas exchange and leakage during exhalation between the teachers and the students was found. For regional ventilation, the teachers had significantly increased ventral ventilation during AGSM implementation (p < 0.001) whereas students did otherwise. Additionally, the differences of rating scores with and without EIT were also significant. Significant reductions were found in rating scores with EIT assessed by the professor (4.5 ± 2.0, p < 0.001) and by the students themselves (3.9 ± 2.2, p < 0.001). The scores were systematically higher when the students rated themselves compared with the professor's rating (p < 0.001 for both with and without EIT). CONCLUSION: These findings demonstrated that EIT could objectively characterize the maneuver details of AGSM, which might provide a potential tool for real-time assessment of AGSM quality in an objective manner.


Assuntos
Medicina Aeroespacial , Impedância Elétrica , Humanos , Pulmão , Respiração Artificial , Tomografia , Tomografia Computadorizada por Raios X
18.
Sensors (Basel) ; 21(12)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203846

RESUMO

Underlying topography plays an important role in the national economic construction, military security, resource exploration and investigation. Since synthetic aperture radar tomography (TomoSAR) can achieve the three-dimensional imaging of forests, it has been widely used in underlying topography estimation. At present, there are two kinds of TomoSAR based on the applied datasets: single polarimetric TomoSAR (SP-TomoSAR) and fully polarimetric TomoSAR (FP-TomoSAR). However, SP-TomoSAR cannot obtain the underlying topography accurately due to the lack of enough observations. FP-TomoSAR can improve the estimation accuracy of underlying topography. However, it requires high-cost data acquisition for the large-scale application. Thus, this paper proposes the dual polarimetric TomoSAR (DP-TomoSAR) as another suitable candidate to estimate the underlying topography because of its wide swath and multiple polarimetric observations. Moreover, three frequently used spectral estimation algorithms, namely, Beamforming, Capon and MUSIC, are used in DP-TomoSAR. For validation, a series of simulated experiments was carried out, and the airborne P-band multiple polarimetric SAR data over the Lope, Gabon was also acquired to estimate the underlying topography. The results suggest that DP-TomoSAR in HH & HV combination is more suitable to estimate underlying topography over forest areas than other DP combinations. Moreover, the estimation accuracy of DP-TomoSAR is slightly lower than that of FP-TomoSAR but is higher than that of SP-TomoSAR.


Assuntos
Monitoramento Ambiental , Radar , Florestas , Menogaril , Tomografia
19.
Sensors (Basel) ; 21(12)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203992

RESUMO

The extension for high-performance STFT (Short-Time Fourier Transform) algorithm written entirely in Java language for non-parallel computations is presented in the current paper. This solution could compete with the best available and most common algorithms supplied by libraries such as FFTW or JTransform. The main idea was to move complex computations and expensive functions to the program generation phase. Thus, only core and essential operations were executed during the runtime phase. Furthermore, new approach allows to eliminate the necessity for a rearrangement operation that uses the bit-reversal permutation technique. This article presents a brief description of the STFT solution that was worked out as an extension for the original application, in order to increase its efficiency. The solution remains a Stockham algorithm adapted using metaprogramming techniques and entails an additional reduction its execution time. Performance tests and experiments were conducted using a Java Platform and JMH library, which allowed for accurate execution time measurements. Major aspects of the Java VM like warm-up effects were also taken into consideration. Solution was applied into Electrical Capacitance Tomography measurement system in order to measure the material changes during the silo discharging industrial process.


Assuntos
Algoritmos , Tomografia , Análise de Fourier
20.
Sensors (Basel) ; 21(11)2021 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-34205157

RESUMO

Image reconstruction of Magnetic induction tomography (MIT) is an ill-posed problem. The non-linear characteristics lead many difficulties to its solution. In this paper, a method based on a Generative Adversarial Network (GAN) is presented to tackle these barriers. Firstly, the principle of MIT is analyzed. Then the process for finding the global optimum of conductivity distribution is described as a training process, and the GAN model is proposed. Finally, the image was reconstructed by a part of the model (the generator). All datasets are obtained from an eight-channel MIT model by COMSOL Multiphysics software. The voltage measurement samples are used as input to the trained network, and its output is an estimate for image reconstruction of the internal conductivity distribution. The results based on the proposed model and the traditional algorithms were compared, which have shown that average root mean squared error of reconstruction results obtained by the proposed method is 0.090, and the average correlation coefficient with original images is 0.940, better than corresponding indicators of BPNN and Tikhonov regularization algorithms. Accordingly, the GAN algorithm was able to fit the non-linear relationship between input and output, and visual images also show that it solved the usual problems of artifact in traditional algorithm and hot pixels in L2 regularization, which is of great significance for other ill-posed or non-linear problems.


Assuntos
Processamento de Imagem Assistida por Computador , Tomografia , Algoritmos , Condutividade Elétrica , Tomografia Computadorizada por Raios X
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