Original Spatial Resolution Research Articles

Refinamento de imagens termais do Landsat 5 - TM com base em classes de NDVI

O objetivo desse estudo foi avaliar um método simplificado, baseado em classes de NDVI para refinamento das imagens de temperatura da superfície (Ts), obtidas pelo sensor TM do Landsat 5 referentes aos anos de 2005 e 2006. Para tanto, foram propostos e comparados três modelos de refinamento baseados no método de regressão linear. Os erros percentuais e erros médios quadráticos obtidos com a utilização dos modelos avaliados foram, respectivamente, da ordem de 0,37% e 1,38 ºC, enquanto o modelo original apresentou erro médio quadrático da ordem de 1,32 ºC. Foram constatados que os erros obtidos com as calibrações realizadas não influenciaram significativamente nos valores médios das imagens termais, e que os resultados contribuíram substancialmente para a melhoria da resolução espacial das mesmas. O refinamento permitiu ainda a identificação precisa de alvos da superfície e a identificação de feições não detectáveis na resolução original. Isto evidencia que o método simplificado sugerido neste estudo, permite um refinamento preciso com uma forma de obtenção mais simples em relação ao modelo original.

Validating “Image box”-a new approach to multicentre radiology reviews using a web-based image review system: study protocol.

Objectives: To validate the use of “Imagebox”- a web-based image review system for large scale multicentre trials. Patients and Methods: As part of the multicentre trial ‘Prospective study of Outcomes in Sporadic versus Hereditary breast cancer (POSH) study’ mammograms were collected and digitised. Software was created allowing digitised mammograms to be viewed from any location with internet access. Two validation studies were performed. Firstly phantom studies using line-pairs (1–20 lpmm -1 ) to assess spatial resolution and the CDMAM 3.4 phantom were used to assess the visibility of gold discs for contrast detail .Secondly a comparison was made between the scoring of 77 patients’ original diagnostic analogue mammograms from 29 hospitals and the corresponding web images. Films and web images were scored by one experienced breast radiologist according to the BIRADS classification. At least 8 weeks elapsed between scoring images from the same patient. Results: The original analogue spatial resolution was 20 lpmm -1 and web resolution of the same image reduced at 8.9 lpmm -1 . Contrast detail assessment demonstrated analogue and web images with near concordance and the image quality factor, IQF inv for the web was reduced but within the 95% confidence interval of the original mammograms. BIRADS final assessment showed good agreement between the analogue and the identical web images (Kappa 0.82). Conclusion: The overall reduction in spatial resolution did not adversely affect the quality of the diagnostic image on “Imagebox”. This may be due to its functionality, specifically the high magnification zoom which enhances diagnostic interpretation. Imagebox is a promising solution to address the logistical challenges for large breast imaging reviews and has further potential for education and self assessment.

A super resolution approach for spectral unmixing of remote sensing images

It is well known that coarse spatial resolution is an important factor for the occurrence of mixed pixels in remote sensing images, and conventional approaches for spectral unmixing adopt various techniques on spectral dimension only in a fixed spatial resolution. In this article, a super resolution (SR) approach for spectral unmixing is proposed, based on the assumption that increasing the spatial resolution helps to retrieve the composition of a pixel. Firstly, a remote sensing image is downscaled into an SR image using example-based kernel ridge regression (EBKRR). Secondly, the SR image is classified using supervised hard classification, and then the class map is decomposed into thematic class layers. Thirdly, the thematic class layers are upscaled into the original spatial resolution with an averaging operation, and the abundance maps are finally derived. In two simulated data-based experiments and one ground data-based experiment, this approach was compared with linear spectral mixture analysis (LSMA) and artificial neural network (ANN)-based spectral unmixing methods. The accuracy assessment indicated that the SR approach outperformed LSMA and ANN under measurements of mean absolute error and absolute bias in the three experiments.

A remote desktop-based telemedicine system

We describe the construction of an almost cost-free telemedicine system using a remote desktop and the public internet system. Using this system, real-time images in Digital Imaging and Communication in Medicine (DICOM) format were observed with their original spatial resolution without any delay. The system is secure for the protection of personal information. There is no risk of viral infection to either the host or the viewer’s computer. No specific license, contract or initial investment is necessary. This system may partially alleviate the present shortage of specialists.

The Temporal Aliasing Formulas for the Tandem Mission of Jason-1 and TOPEX/Poseidon

Abstract The temporal aliasing formulas are derived for the Tandem Mission of Jason-1 and the Ocean Topography Experiment (TOPEX)/Poseidon. Previously, aliasing formulas were derived for a single satellite or a constellation of coordinated satellites, wherein the coordination is such that the collective samplings appear as if they were carried out by a single satellite. In this vein, Jason-1 and TOPEX/Poseidon are coordinated spatially but not temporally. The problem is treated as a general problem about the temporal phasing between any two satellites that are coordinated spatially so that the Tandem Mission is just one special case, whereas the temporally coordinated case is another special case. The present results do agree with the formulas for a constellation of coordinated satellites when the temporal phasing yields temporal coordination, as they should. The benefit of temporal coordination shows itself as having a higher spatial resolution for temporally aliased features. The physical implication is twofold. First, a high-frequency and low-wavenumber feature (e.g., the barotropic Rossby waves) has a better chance of being aliased as a low-frequency and higher-wavenumber feature in a perfectly coordinated mission than it has in the Tandem Mission. Second, in a perfectly coordinated mission, a high-frequency and high-wavenumber feature could be aliased as a low-frequency and high-wavenumber feature rather than as a low-frequency and low-wavenumber feature in the Tandem Mission. Despite the extreme mathematical complexity, the physical case is rather intuitive. Namely, the two satellites need temporal coordination to work as one in fending off temporal aliasing. Without it, the two satellites behave as two independent satellites, thus each reverting to their original (i.e., lower) spatial resolution capability in dealing with temporal aliasing.

QualIM®: software para treinamento na interpretação de imagens médicas digitais

OBJETIVO: Foi desenvolvido um software denominado QualIM® - Qualificação de Imagens Médicas para treinamento de profissionais na interpretação de exames digitais de mamografias utilizando ferramentas de manipulação de imagens, em monitores específicos, classificadas em BI-RADS®. MATERIAIS E MÉTODOS: O sistema, desenvolvido em Delphi 7, armazena as respostas da interpretação de imagens mamográficas durante o treinamento e compara aos dados inseridos denominados "padrão-ouro". O sistema contém imagens de computed radiography, direct radiography e digitalizadas. O software converte as imagens do computed radiography e direct radiography para o formato TIFF, mantendo as resoluções espacial e de contraste originais. Profissionais em treinamento manipulam o realce da imagem utilizando ferramentas de software (zoom, inversão, réguas digitais, outras). Dependendo da complexidade, são apresentadas até oito incidências mamográficas, seis imagens de ultra-som e duas de anatomopatológico. RESULTADOS: O treinamento iniciou em 2007 e atualmente faz parte do programa de residência em radiologia. O software compõe o texto, de forma automática, das informações inseridas pelo profissional, baseado nas categorias BI-RADS, e compara com a base de dados. CONCLUSÃO: O software QualIM é uma ferramenta digital de ensino que auxilia profissionais no reconhecimento de padrões visuais de uma imagem mamográfica, bem como na interpretação de exames mamográficos, utilizando a classificação BI-RADS.

Multi‐sensor data fusion and comparison of total column ozone

With many remote‐sensing instruments onboard satellites exploring the Earth's atmosphere, most data are processed to gridded daily maps. However, differences in the original spatial, temporal, and spectral resolution—as well as format, structure, and temporal and spatial coverage—make the data merging, or fusion, difficult. NASA Goddard Earth Sciences Data and Information Services Center (GES‐DISC) has archived several data products for various sensors in different formats, structures, and multi‐temporal and spatial scales for ocean, land, and atmosphere. In this investigation using Earth science data sets from multiple sources, an attempt was made to develop an optimal technique to merge the atmospheric products and provide interactive, online analysis tools for the user community. The merged/fused measurements provide a more comprehensive view of the atmosphere and improve coverage and accuracy, compared with a single instrument dataset. This paper describes ways of merging/fusing several NASA Earth Observing Systems (EOS) remote‐sensing datasets available at GES‐DISC. The applicability of various methods was investigated for merging total column ozone to implement these methods into Giovanni, the online interactive analysis tool developed by GES‐DISC. Ozone data fusion of MODerate resolution Imaging Spectrometer (MODIS) Terra and Aqua Level‐3 daily data sets was conducted, and the results were found to provide better coverage. Weighted averaging of Terra and Aqua data sets, with the consequent interpolation through the remaining gaps using Optimal Interpolation (OI), also was conducted and found to produce better results. Ozone Monitoring Instrument (OMI) total column ozone is reliable and provides better results than Atmospheric Infrared Sounder (AIRS) and MODIS. However, the agreement among these instruments is reasonable. The correlation is high (0.88) between OMI and AIRS total column ozone, while the correlation between OMI and MODIS Terra/Aqua fused total column ozone is 0.79.

Temporal statistical analysis of laser speckle images and its application to retinal blood-flow imaging

Temporal-statistical analysis of laser-speckle image (TS-LSI) preserves the original spatial resolution, in contrast to conventional spatial-statistical analysis (SS-LSI). Concerns have been raised regarding the temporal independency of TS-LSI signals and its insensitivity toward stationary-speckle contamination. Our results from flow phantoms and in vivo rat retinas demonstrated that the TS-LSI signals are temporally statistically independent and TS-LSI minimizes stationary-speckle contamination. The latter is because the stationary speckle is "non-random" and thus non-ergodic where the temporal average of stationary speckle needs not equal its spatial ensemble average. TS-LSI detects blood flow in smaller blood vessels and is less susceptible to stationary-speckle artifacts.

Crop area estimate from original and simulated spatial resolution data and landscape metrics

Images acquired at the same day by the ETM+/Landsat-7 (30 m of spatial resolution) and MODIS/Terra (250 m) sensors were used to estimate areas of three major crops (soybean, sugarcane, and corn) with different landscape patterns in Southeastern Brazil. Majority filtering of ETM + classification results was applied to describe the behavior of 15 selected landscape metrics at distinct simulated spatial resolutions (90, 150, 210 and 270 m). By using regression models, the performance of MODIS and derived metrics to predict adequately the crop area, considering ETM+ data as reference, were analyzed. Results showed that the MODIS instrument overestimated the areas of soybean (15%) and sugarcane (1%), and underestimated the area of corn (12%). Multiple regression results indicated that coarse spatial resolution sensors can be used to predict adequately the area viewed by the 30 m spatial resolution instruments only for crops with low fragmentation pattern such as soybean. These sensors cannot be used to predict the area of corn due to aggregation pixel effects of the less fragmented crops (soybean and sugarcane) over the most fragmented one (corn), as demonstrated by the spatial resolution simulation using majority filtering of the ETM+ image. Landscape metrics improved MODIS area estimates only for sugarcane, as indicated by higher values of R² for multiple than for simple regression. Only a small set of metrics was select to compose the multiple regression models because most of them were not preserved across different spatial resolutions (30 m and 250 m).

A heuristic for the retrieval of objects in video in the framework of the rough indexing paradigm

In this paper, we tackle the problem of matching of objects in video in the framework of the rough indexing paradigm. In this context, the video data are of very low spatial and temporal resolution because they come from partially decoded MPEG compressed streams. This paradigm enables us to achieve our purpose in near real time due to the faster computation on rough data than on original full spatial and temporal resolution video frames. In this context, segmentation of rough video frames is inaccurate and the region features (texture, color, shape) are not strongly relevant. The structure of the objects must be considered in order to improve the robustness of the matching of regions. The problem of object matching can be expressed in terms of region adjacency graph (RAG) matching. Here, we propose a directed acyclic graph (DAG) matching method based on a heuristic in order to approximate object matching. The RAGs to compare are first transformed into DAGs by orienting edges. Then, we compute some combinatoric metrics on nodes in order to classify them by similarity. At the end, a top-down process on DAGs aims to match similar patterns that exist between the two DAGs. The results are compared with those of a method based on relaxation matching.

New tools for visualization and analysis of morphogenesis in spherical embryos

AbstractTexture rendering of three‐dimensional Surface Imaging Microscopy (SIM) date acquired in a fixed late gastrula stage Xenopus laevis embryo. The rendering at center has been section to show the internal surfaces of the blastocoel and archenteron. The surrounding images show central coronal, sagittal, and equitorial sections through the same date. The original SIM spatial resolution was approximately 1.7 microns in each dimension. See Tyszka et al., Developmental Dynamics 234:974–983. © 2006 Wiley‐Liss, Inc.

Specific versus Nonspecific Brain Activity in a Parametric N-Back Task

In this study functional magnetic resonance imaging (fMRI) was used to examine cerebral activity patterns in relation to increasing mental load of a working memory task. Aim of the experiment was to distinguish nonspecific task-related processes from specific workload processes analytically. Twelve healthy volunteers engaged in a spatial n-back task with four levels. FMRI data were acquired with the 3D-PRESTO pulse sequence. Analysis entailed a two-step multiple regression algorithm, which was specifically designed to measure and separate load-sensitive and load-insensitive activity simultaneously, while preserving the original high spatial resolution of the fMRI signal. Load-sensitive and load-insensitive activity was found in both dorsolateral-prefrontal and parietal cortex, predominantly bilaterally, and in the anterior cingulate. As expected, the left primary sensorimotor cortex showed predominantly load-insensitive activity. Load-sensitive activity reflects specific working memory functions, such as temporary retention and manipulation of information, while load-insensitive activity reflects supportive functions, such as visual orientation, perception, encoding, and response selection and execution. Good performance was correlated with a large area of load-sensitive activity in anterior cingulate, and with a small area of load-insensitive activity in the right parietal cortex. The findings indicate that nonspecific and specific working memory processes colocalize and are represented in multiple frontal and parietal regions. Implication of this analytical strategy for application in research on psychiatric disorders is discussed.

Wavelet Analysis of Dynamic PET Data: Application to the Parametric Imaging of Benzodiazepine Receptor Concentration

Receptor density and ligand affinity can be assessed using positron emission tomography (PET). Biological parameters (Bmax′, k1, k2, kon/VR, koff) are estimated using a compartmental model and a multi-injection protocol. Parametric imaging of the ligand–receptor model has been shown to be of special interest to study certain brain disorders. However, the low signal-to-noise ratio in kinetic curves at the pixel level hampers an adequate estimation of model parameters during the optimization procedure. For this reason, mapping requires a spatial filter, resulting in a loss of resolution. Filtering the kinetic curves in the frequency domain using the Fourier transform is not appropriate, because of difficulties in choosing a correct and efficient cutoff frequency. A wavelet-based filter is more appropriate to such tracer kinetics. The purpose of this study is to build up parametric images at the pixel level while conserving the original spatial resolution, using wavelet-based filtering. Data from [11C]flumazenil studies, mapping the benzodiazepine receptor density, were used. An invertible discrete wavelet transform was used to calculate the time–frequency signals of the time–concentration PET curves on a pixel-by-pixel basis. Kinetic curves observed from large regions of interest in high and low receptor-density regions were used to calibrate the threshold of wavelet coefficients. The shrunken wavelet coefficients were then transformed back to the original domain in order to obtain the filtered PET signal. Maps of all binding parameters were obtained at the pixel level with acceptable coefficients of variation of less than 30% for the Bmax′ parameter in most of the gray matter. A strong correlation between model parameter estimates using the usual regions of interest and parametric imaging was observed for all model parameters (r = 0.949 for the parameter Bmax′). We conclude that wavelet-based filters are useful for building binding parameter maps without loss of the original spatial resolution of the PET scanner. The use of the wavelet-based filtering method can be extended far beyond the multi-injection protocol. It is likely to be also effective for other dynamic PET studies.

Real-time two-dimensional surface profile measurement in a sinusoidal phase-modulating laser diode interferometer

A real-time 2-D surface profile measurement system is described. In this system, a laser diode and a 2-D charge-coupled device image sensor are used as a light source and a photodetector, respectively. The phase is detected from the sinusoidal phase-modulating interference signal using the high-speed electrical circuit. The time required for phase detection is 20 ms for 50 x 40 measuring points. Because the phases can be obtained for even and odd fields of the image sensor, the original spatial resolution of the image sensor is not reduced in this system. Repeatability of the measurement is -14 nm, rms.

シンチスキャナのコリメータの統計誤差による分解性能低下とInformation Densityの関係

Because the detector of Scintiscanner is moving at all time over scintiscanning, the measurement time at any scanning point is very short. Therefore, a statistical error have influence on the spatial resolution of the scintigraphy. The statistical error is represented as next equation that is a function of the Information Density. [numerical formula] The FWHM which is obtained by actual Tsuyatsucanning is compared with the calculated FWHM both best and worst that may be obtained by the statistical error. We showed a result that a optical resolution of scintigraphy is deteriorated by the statistical error about the rate of little more than the statistical error from the original spatial resolution of the collimator.