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1

ECG-Gated 16MDCT of the Coronary Arteries: Assessment of Image Quality and Accuracy in Detecting Stenoses  

Microsoft Academic Search

OBJECTIVE. The aim of this study was to investigate image quality and diagnostic accu- racy in detecting coronary artery lesions using a 16-MDCT scanner. MATERIALS AND METHODS. Thirty-seven patients (28 men, nine women) under- went unenhanced helical CT and MDCT angiography of the coronary arteries. After patients received oral ?-blocker medication, CT scans were obtained during a single breath-hold with

Martin Heuschmid; Axel Kuettner; Stephen Schroeder; Tobias Trabold; Anja Feyer; Marcus D. Seemann; Ronald Kuzo; Claus D. Claussen; Andreas F. Kopp

2

High-quality 3-D coronary artery imaging on an interventional C-arm x-ray system  

SciTech Connect

Purpose: Three-dimensional (3-D) reconstruction of the coronary arteries during a cardiac catheter-based intervention can be performed from a C-arm based rotational x-ray angiography sequence. It can support the diagnosis of coronary artery disease, treatment planning, and intervention guidance. 3-D reconstruction also enables quantitative vessel analysis, including vessel dynamics from a time-series of reconstructions. Methods: The strong angular undersampling and motion effects present in gated cardiac reconstruction necessitate the development of special reconstruction methods. This contribution presents a fully automatic method for creating high-quality coronary artery reconstructions. It employs a sparseness-prior based iterative reconstruction technique in combination with projection-based motion compensation. Results: The method is tested on a dynamic software phantom, assessing reconstruction accuracy with respect to vessel radii and attenuation coefficients. Reconstructions from clinical cases are presented, displaying high contrast, sharpness, and level of detail. Conclusions: The presented method enables high-quality 3-D coronary artery imaging on an interventional C-arm system.

Hansis, Eberhard; Carroll, John D.; Schaefer, Dirk; Doessel, Olaf; Grass, Michael [Philips Technologie GmbH Forschungslaboratorien, Roentgenstrasse 24-26, 22335 Hamburg (Germany); Department of Medicine, Division of Cardiology, Health Sciences Center, University of Colorado, Denver, Colorado 80262 (United States); Philips Technologie GmbH Forschungslaboratorien, Roentgenstrasse 24-26, 22335 Hamburg (Germany); Institute of Biomedical Engineering, University of Karlsruhe, Kaiserstr. 12, 76131 Karlsruhe (Germany); Philips Technologie GmbH Forschungslaboratorien, Roentgenstrasse 24-26, 22335 Hamburg (Germany)

2010-04-15

3

Patient Characteristics as Predictors of Image Quality and Diagnostic Accuracy of MDCT Compared With Conventional Coronary Angiography for Detecting Coronary Artery Stenoses: CORE-64 Multicenter International Trial  

PubMed Central

OBJECTIVE The purpose of the study was to investigate patient characteristics associated with image quality and their impact on the diagnostic accuracy of MDCT for the detection of coronary artery stenosis. MATERIALS AND METHODS Two hundred ninety-one patients with a coronary artery calcification (CAC) score of ? 600 Agatston units (214 men and 77 women; mean age, 59.3 ± 10.0 years [SD]) were analyzed. An overall image quality score was derived using an ordinal scale. The accuracy of quantitative MDCT to detect significant (? 50%) stenoses was assessed using quantitative coronary angiography (QCA) per patient and per vessel using a modified 19-segment model. The effect of CAC, obesity, heart rate, and heart rate variability on image quality and accuracy were evaluated by multiple logistic regression. Image quality and accuracy were further analyzed in subgroups of significant predictor variables. Diagnostic analysis was determined for image quality strata using receiver operating characteristic (ROC) curves. RESULTS Increasing body mass index (BMI) (odds ratio [OR] = 0.89, p < 0.001), increasing heart rate (OR = 0.90, p < 0.001), and the presence of breathing artifact (OR = 4.97, p ? 0.001) were associated with poorer image quality whereas sex, CAC score, and heart rate variability were not. Compared with examinations of white patients, studies of black patients had significantly poorer image quality (OR = 0.58, p = 0.04). At a vessel level, CAC score (10 Agatston units) (OR = 1.03, p = 0.012) and patient age (OR = 1.02, p = 0.04) were significantly associated with the diagnostic accuracy of quantitative MDCT compared with QCA. A trend was observed in differences in the areas under the ROC curves across image quality strata at the vessel level (p = 0.08). CONCLUSION Image quality is significantly associated with patient ethnicity, BMI, mean scan heart rate, and the presence of breathing artifact but not with CAC score at a patient level. At a vessel level, CAC score and age were associated with reduced diagnostic accuracy.

Dewey, Marc; Vavere, Andrea L.; Arbab-Zadeh, Armin; Miller, Julie M.; Sara, Leonardo; Cox, Christopher; Gottlieb, Ilan; Yoshioka, Kunihiro; Paul, Narinder; Hoe, John; de Roos, Albert; Lardo, Albert C.; Lima, Joao A.; Clouse, Melvin E.

2012-01-01

4

Renal arteries (image)  

MedlinePLUS

A renal angiogram is a test used to examine the blood vessels of the kidneys. The test is performed ... main vessel of the pelvis, up to the renal artery that leads into the kidney. Contrast medium ...

5

Image quality analyzer  

NASA Astrophysics Data System (ADS)

Image quality analyzer (IQA) which used as device for efficiency analysis of adaptive optics application is described. In analyzer marketed possibility estimations quality of images on three different criterions of quality images: contrast, sharpnesses and the spectral criterion. At present given analyzer is introduced on Big Solar Vacuum Telescope in stale work that allows at observations to conduct the choice of the most contrasting images of Sun. Is it hereinafter planned use the analyzer in composition of the ANGARA adaptive correction system.

Lukin, V. P.; Botugina, N. N.; Emaleev, O. N.; Antoshkin, L. V.; Konyaev, P. A.

2012-07-01

6

Comparison of image quality and radiation dose in computed tomography angiography of the peripheral arteries using tube voltage of 80kV versus 100kV.  

PubMed

OBJECTIVE: To compare the image quality and dose of radiation in two groups of patients undergoing CT angiography of the lower limbs, one with tube voltage of 80kV and the other with tube voltage of 100kV. MATERIAL AND METHODS: We performed CT angiography of the lower limbs in 60 patients with suspected peripheral arterial disease. Patients were randomly assigned to one of two groups; in one group, CT angiography was performed using a tube voltage of 80kV, whereas in the other it was performed using 100kV. The remaining acquisition parameters were the same in both groups. The images were analyzed by quantifying vascular density (VD) and noise (N) and by calculating the quotients density/noise (QVDN) and contrast/noise (QCN). Two radiologists working independently evaluated the subjective quality of the images. We calculated the estimated effective dose (EED) based on the dose-length product (DLP). RESULTS: In the group studied at 80kV, VD was significantly higher (462.5UH±95.6 vs. 372UH±100.9; P<.001), QVDN was significantly higher (241.9±48.1 vs. 194.3±49.6; P<.001), and there were trends toward higher N (21.3UH±13 vs. 16.3UH±3.5; P=.098) and toward higher QCN (21.4±12.1 vs. 22.9±9.1; P=.15). No significant differences were found in the subjective quality of the images. The EED was significantly lower in the group studied at 80kV (4.73mSv±1.1 vs. 9.6mSv±2.2; P<.001). CONCLUSION: Using 80kV instead of 100kV for CT angiography of the lower limbs reduces the dose of radiation without affecting the diagnostic efficacy of the study. PMID:23276715

Oca Pernas, R; Delgado Sánchez-Gracián, C; Tardáguila de la Fuente, G; Fernández Del Valle, A; Silva Priegue, N; González Vázquez, M; Trinidad López, C

2012-12-28

7

SSA Image Quality Modeling  

NASA Astrophysics Data System (ADS)

This paper evaluates the ITIQUE image quality modeling framework for SSA applications. Based on Bovik and Sheik’s VIF metric, ITIQUE evaluates the Shannon mutual information (MI) at multiple spatial scales between a pristine object and the image output from a detailed image formation chain simulation. Integrating the MI at each spatial scale and applying a calibration offset produces a prediction of NIIRS image quality indicating the level of interpretation tasks that could be supported. The model enables prediction of NIIRS quality obtainable as dependent on image collection conditions and image system design including both hardware and processing algorithms. The ITIQUE framework could facilitate concept evaluation and engineering design by quantitatively relating image formation performance directly in terms of end end-user mission needs. Previous work focused on overhead imagery of terrestrial scenes and linear processing only. This paper considers ground-based imaging of SSA targets and extends the previous study to include non-linear processing. A range of turbulence strengths and SNRs are included. ITIQUE predictions are shown to match well to results from a human visual assessment study in which a panel of human observers rated NIIRS quality of the same imagery.

Luna, C.; Gerwe, D.; Calef, B.

2010-09-01

8

Image quality assessment on image haze removal  

Microsoft Academic Search

In the hazy weather, the image of outdoor scene is degraded by suspended particles. Recently, great progresses have been made on single image haze removal. Therefore an accurate quality metric is required. Although image quality assessment has been extensively studied these past few decades, few methods can be applied in this area since there is no reference image. This paper

Shuai Fang; Jingrong Yang; Jiqing Zhan; Hongwu Yuan; Ruizhong Rao

2011-01-01

9

Image quality measurements in radiology.  

PubMed

Image quality measurement methods are reviewed and difficulties in various approaches are highlighted. The main emphasis of the paper is on objective image quality measurements, however, subjective assessment methods are also discussed briefly. PMID:16461535

Tapiovaara, M

2006-02-03

10

Image Quality Measures for Fingerprint Image Enhancement  

Microsoft Academic Search

Fingerprint image quality is an important factor in the perf ormance of Automatic Fingerprint Identification Systems(AFIS). It is used to evaluate the system performance, assess enrollment acceptability, and evaluate fingerprint sensors. This paper presents a novel methodology for fingerp rint image quality measurement. We propose limited ring-wedge spectral measure to estimate the global fingerprint image features, and inhomogeneity with d

Chaohong Wu; Sergey Tulyakov; Venu Govindaraju

2006-01-01

11

High Suited Carotid Artery Stenosis and Imaging  

Microsoft Academic Search

A stenosis of the internal carotid artery is typically irregular and approximately up to two centimeters distal the bifurcation.\\u000a However, this is not what it is meant here. The so-called “high suited carotid artery stenoses” are different with respect\\u000a to imaging procedure, more diagnosis, and particulary in treatment planning, and are a little bit complex than the stenoses\\u000a just around

B. Butz

12

Spatially adaptive image quality metrics for perceptual image quality assessment  

NASA Astrophysics Data System (ADS)

The problem of objective image quality assessment has been known for couple of decades but with emerging multimedia technologies it becomes very important. This paper presents an approach to predict perceived quality of compressed images while incorporating real visual attention coordinates. Information about the visual attention is not usually taken into account in models for image quality assessment. Impact of the region of interest on estimation accuracy of a simple image quality metric has been investigated in our previous papers. The gaze coordinates were calculated using calibrated electro-oculogram records of human observers while watching a number of test images. This paper further investigates this idea using data from more observers. Obtained mean opinion scores of perceived image quality and eye tracking data were used to verify potential improvement of assessment accuracy for a simple image quality metric.

Fliegel, Karel

2009-08-01

13

[Imaging quality evaluation of computational imaging spectrometry].  

PubMed

As a novel imaging spectrometry, computational imaging spectrometry (CIS) has the advantages of high throughput, snapshot imaging etc. However, there is little research on imaging quality evaluation of CIS system. In the present paper, a quantitive evaluation method for imaging quality of CIS system was presented. ISO 12233 chart was used as the objective source, and then imaging and reconstruction of the spatial-spectral information was provided. Calculating modulation transfer functions (MTFs) for the reconstructed images was considered as the criterion of the imaging quality evaluation of CIS system. The result shows that MTFs for single-frame sampling decrease rapidly with the aliasing spectral number increasing. When the number of the aliasing spectra is 9, MTF for the reconstructed image decreases by 50% compared to the original scene. This work helps better understand the pros and cons of CIS system and arrange the aliasing spectral number reasonably to reconstruct the object scene precisely. PMID:24059216

Qian, Lu-Lu; Xiangli, Bin; Lü, Qun-Bo; Zhou, Zhi-Liang; Fu, Qiang

2013-07-01

14

Coronary artery imaging system using gated tomosynthesis  

SciTech Connect

A method is described of imaging a blood vessel such as a coronary artery. The steps comprise: providing radiation source means and radiation detector means on opposing sides of a target area and of administering a contrast agent intravenously; gating the radiation source means based on a selected time using an electrocardiogram to obtain detector signals indicative of views through the target area; and tomosynthesisly combining the detector signals to provide a planar image through the target area, the planar image being generally perpendicular to the path of radiation through the target area.

Macovski, A.

1987-05-05

15

Objective measurements of image quality.  

PubMed

Tissue harmonic imaging (THI) and compound imaging have been reported clinically to improve contrast resolution, tissue differentiation and overall image quality. However, there have been limited studies to date to quantify objectively the improvements in image quality achieved with these new imaging techniques. The aim of this study was to quantify differences in image quality that exist between conventional B-mode imaging, harmonic imaging, compound imaging and harmonic compound imaging. An ATL HDI 5000 scanner with three probes (C5-2, L7-4 and L12-5) was tested with two different types of test object, the Gammex-RMI model 404 GS LE and the Gammex-RMI 403 GS LE. The measurement limitations associated with subjective analysis methods were not present in this study because an automated image analysis program was used to determine the image quality parameters. Therefore, subtle differences between the four imaging modes could be detected. Significant improvements in lateral resolution and slice thickness as a function of depth were found with THI. Contrast resolution and anechoic target detection improved with compound imaging, and harmonic compound imaging improved lateral resolution, slice thickness as a function of depth and contrast resolution. PMID:14998675

Browne, Jacinta E; Watson, Amanda J; Gibson, Nicholas M; Dudley, Nicholas J; Elliott, Alex T

2004-02-01

16

Automatic segmentation of artery wall in coronary IVUS images: a probabilistic approach  

Microsoft Academic Search

Intravascular ultrasound images represent a unique tool to analyze the morphology of arteries and vessels (plaques, restenosis, etc.). The poor quality of these images makes unsupervised segmentation based on traditional segmentation algorithms (such as edge or ridge\\/valley detection) fail to achieve the expected results. Here, the authors present a probabilistic flexible template to separate different regions in the image. In

D. Gil; P. Radeva; J. Saludes; J. Mauri

2000-01-01

17

Image quality concepts for PACS  

NASA Astrophysics Data System (ADS)

The complexity of modern Picture Archiving and Communication Systems (PACS) confronts the potential user with a bewildering array of specifications, of which those effecting image quality are of primary importance. This paper reviews some of the basic concepts of PACS image acquisition and display and the relationship of the specifications for each to image quality. The key parameters of images quality for image digitization devices are spatial resolution, dynamic range, pixel accuracy and signal to noise ratio. On the output side critical factors are brightness, spatial and contrast resolution, stability, and uniformity. The concept of frame buffer depth vs. display depth for CRT monitors is reviewed, and the correspondence of CRT images to film based images is discussed. The principles of sampling theory and the Nyquist limit are also discussed. Through an understanding of the concepts presented in this paper, the PACS user (or potential user) will be in a better position to evaluate PACS for his/her clinical application.

Glicksman, Robert A.; Prior, Fred W.

1994-05-01

18

A universal image quality index  

Microsoft Academic Search

We propose a new universal objective image quality index, which is easy to calculate and applicable to various image processing applications. Instead of using traditional error summation methods, the proposed index is designed by modeling any image distortion as a combination of three factors: loss of correlation, luminance distortion, and contrast distortion. Although the new index is mathematically defined and

Zhou Wang; Alan C. Bovik

2002-01-01

19

Adaptive image kernels for maximising image quality  

NASA Astrophysics Data System (ADS)

This paper discusses a novel image noise reduction strategy based on the use of adaptive image filter kernels. Three adaptive filtering techniques are discussed and a case study based on a novel Adaptive Gaussian Filter is presented. The proposed filter allows the noise content of the imagery to be reduced whilst preserving edge definition around important salient image features. Conventional adaptive filtering approaches are typically based on the adaptation of one or two basic filter kernel properties and use a single image content measure. In contrast, the technique presented in this paper is able to adapt multiple aspects of the kernel size and shape automatically according to multiple local image content measures which identify pertinent features across the scene. Example results which demonstrate the potential of the technique for improving image quality are presented. It is demonstrated that the proposed approach provides superior noise reduction capabilities over conventional filtering approaches on a local and global scale according to performance measures such as Root Mean Square Error, Mutual Information and Structural Similarity. The proposed technique has also been implemented on a Commercial Off-the-Shelf Graphical Processing Unit platform and demonstrates excellent performance in terms of image quality and speed, with real-time frame rates exceeding 100Hz. A novel method which is employed to help leverage the gains of the processing architecture without compromising performance is discussed.

Bamber, David C.; Page, Scott F.; Bolsover, Matthew; Hickman, Duncan; Smith, Moira I.; Kimber, Paul K.

2010-04-01

20

Pulmonary artery thrombus detection by magnetic resonance imaging.  

PubMed

We report a patient in whom cardiac magnetic resonance imaging detected a clinically unsuspected pulmonary artery thromboembolus. Follow-up MRI after surgical removal of the thromboembolus showed normal pulmonary arteries. This case illustrates the potential utility of MRI in the detection and follow-up of central pulmonary artery thromboembolism. PMID:2909340

Szucs, R A; Rehr, R B; Tatum, J L

1989-01-01

21

Why is image quality assessment so difficult?  

Microsoft Academic Search

Image quality assessment plays an important role in various image processing applications. A great deal of effort has been made in recent years to develop objective image quality metrics that correlate with perceived quality measurement. Unfortunately, only limited success has been achieved. In this paper, we provide some insights on why image quality assessment is so difficult by pointing out

Zhou Wang; Alan C. Bovik; Ligang Lu

2002-01-01

22

Coronary artery remodeling in non-contrast CT images  

NASA Astrophysics Data System (ADS)

A significant cause of coronary artery disease is the coronary atherosclerosis which leads to stenosis of coronary arteries. It has been shown in recent studies, using intravascular ultrasound and contrast-enhanced CT, that early atherosclerosis causes positive coronary artery remodeling, defined as increases in the cross-sectional area. It is hypothesized that detection of artery remodeling using non-contrast CT can be an important factor in sub-clinical assessment of cardiac risk for asymptomatic subjects. However, measuring remodeling in coronary arteries in non-contrast CT images is a challenging task because coronary arteries are small and the intensity of coronary arteries is similar to that of surrounding tissues. Automatic segmentation algorithms that have been successful in segmenting coronary arteries in contrast-enhanced images do not perform well. To overcome these difficulties, we developed an interactive application to enable effective measurement of coronary artery remodeling in non-contrast CT images. This application is an extension to the 3D Slicer image analysis platform. It allows users to visualize and trace the centerline of arteries in cross sectional views. The artery centerlines are displayed in a three dimensional view overlaid on the original image volume and color-coded according to the artery labels. Using this 3D artery model, the user can sample the cross-sectional area of the arteries at selected points for remodeling assessment. Initial validation has demonstrated the effectiveness of this method. A pilot study also showed positive correlation of large coronary artery remodeling with highest lifetime risks. Further evaluation is underway using larger study size and more measurement points.

Xu, Haiyong; Zheng, Mingna; Yang, Yanhua; Carr, J. Jeffery; Ge, Yaorong

2012-02-01

23

Survey of Aerial Image Quality Assessment Methods.  

National Technical Information Service (NTIS)

The accuracy of photogrammetric mapping, as well as the reliability of image interpretation, strongly depend upon the quality of the images used. It is therefore important to assess or describe image quality. Different areas of application and various met...

A. Boberg

1989-01-01

24

Fovea based image quality assessment  

Microsoft Academic Search

Humans are the ultimate receivers of the visual information contained in an image, so the reasonable method of image quality assessment (IQA) should follow the properties of the human visual system (HVS). In recent years, IQA methods based on HVS-models are slowly replacing classical schemes, such as mean squared error (MSE) and Peak Signal-to-Noise Ratio (PSNR). IQA-structural similarity (SSIM) regarded

Anan Guo; Debin Zhao; Shaohui Liu; Guangyao Cao

2010-01-01

25

Fovea based image quality assessment  

NASA Astrophysics Data System (ADS)

Humans are the ultimate receivers of the visual information contained in an image, so the reasonable method of image quality assessment (IQA) should follow the properties of the human visual system (HVS). In recent years, IQA methods based on HVS-models are slowly replacing classical schemes, such as mean squared error (MSE) and Peak Signal-to-Noise Ratio (PSNR). IQA-structural similarity (SSIM) regarded as one of the most popular HVS-based methods of full reference IQA has apparent improvements in performance compared with traditional metrics in nature, however, it performs not very well when the images' structure is destroyed seriously or masked by noise. In this paper, a new efficient fovea based structure similarity image quality assessment (FSSIM) is proposed. It enlarges the distortions in the concerned positions adaptively and changes the importances of the three components in SSIM. FSSIM predicts the quality of an image through three steps. First, it computes the luminance, contrast and structure comparison terms; second, it computes the saliency map by extracting the fovea information from the reference image with the features of HVS; third, it pools the above three terms according to the processed saliency map. Finally, a commonly experimental database LIVE IQA is used for evaluating the performance of the FSSIM. Experimental results indicate that the consistency and relevance between FSSIM and mean opinion score (MOS) are both better than SSIM and PSNR clearly.

Guo, Anan; Zhao, Debin; Liu, Shaohui; Cao, Guangyao

2010-07-01

26

Linear Discriminants and Image Quality  

Microsoft Academic Search

The use of linear discriminant functions, and particularly a discriminant function derived from the work of Harold Hotelling, as a means of assessing image quality is reviewed. The relevant theory of ideal or Bayesian observers is briefly reviewed, and the circumstances under which this observer reduces to a linear discriminant are discussed. The Hotelling oberver is suggested as a linear

Harrison H. Barrett; T. Gooley; K. Girodias; Jannick P. Rolland; T. White; J. Yao

1991-01-01

27

[Application of objective image quality measures on CT image].  

PubMed

Computed tomography (CT) is an essential imaging modality. To solve the problem caused by increasing radiation exposure from CT scanner and to elevate the image quality, we aimed to apply the general objective image quality methods in CT image quality evaluation. After analyzing the perceptual features of CT image, we tested several popular objective image quality metrics, which focus on the similar perceptual features, on the CT image of phantom and animals. Experiments for verifying the feasibility were carried out. Compared with the subjective ratings from two professional radiation physicians, the complex wavelet-based structural similarity metric presents the better prediction results of the image quality. PMID:21604502

Liu, Mingna; Wang, Qian; Yang, Xin; Zhn, Ming

2011-04-01

28

Objective Quality Assessment of Noised Stereoscopic Images  

Microsoft Academic Search

Stereoscopic images have been widely studied in recent years from a technical point of view, but the related quality assessment does not follow this enthusiasm. An objective quality assessment method for serious noised stereoscopic images is proposed. It is based on 2D quality evaluation and the characteristics of stereoscopic images. The disparity map for stereoscopic image pairs is an important

Yinghua Shen; Chaohui Lu; Pin Xu; Lili Xu

2011-01-01

29

Atherosclerosis of internal carotid artery (image)  

MedlinePLUS

The build-up of plaque in the internal carotid artery may lead to narrowing and irregularity of ... narrowing worsens, pieces of plaque in the internal carotid artery can break free, travel to the brain ...

30

Image quality with array spectrometers  

NASA Astrophysics Data System (ADS)

We present data on the image quality achieved with the near IR array spectrometer cooled grating spectrometer 4 (CGS4) on the UK IR telescope (UKIRT) on Mauna Kea. A design spot size of 30 micrometers was specified for CGS4, to maintain acceptable image quality with both the 58 by 62 pixel array with which it is currently equipped and the 256 by 256 array which CGS4 was also designed to accommodate. Details are given of the design, construction and alignment method which allow linear tolerances of 50 micrometers and angular tolerances of 25 mrad to be met and maintained at cryogenic temperatures. The instrumental flexure is also discussed. Both laboratory spectra and those taken at the telescope illustrate that design spot sizes of 30 micrometers have been achieved in the near IR. It will be demonstrated that the theoretical resolution of the instrument is attained for resolving powers from approximately 200 to 20,000.

Ramsay Howat, Suzanne K.; Wright, Gillian S.; Mountain, C. Matt; Montgomery, David; Atad-Ettedgui, Eli I.

1994-06-01

31

[Quality control of laser imagers].  

PubMed

Multiformat imagers based on laser systems are used for documentation in an increasing number of investigations. The specific problems of quality control are explained and the persistence of film processing in these imager systems of different configuration with (Machine 1: 3M-Laser-Imager-Plus M952 with connected 3M Film-Processor, 3M-Film IRB, X-Rax Chemical Mixer 3M-XPM, 3M-Developer and Fixer) or without (Machine 2: 3M-Laser-Imager-Plus M952 with separate DuPont-Cronex Film-processor, Kodak IR-Film, Kodak Automixer, Kodak-Developer and Fixer) connected film processing unit are investigated. In our checking based on DIN 6868 and ONORM S 5240 we found persistence of film processing in the equipment with directly adapted film processing unit according to DIN and ONORM. The checking of film persistence as demanded by DIN 6868 in these equipment could therefore be performed in longer periods. Systems with conventional darkroom processing comparatively show plain increased fluctuation, and hence the demanded daily control is essential to guarantee appropriate reaction and constant quality of documentation. PMID:1457474

Winkelbauer, F; Ammann, M; Gerstner, N; Imhof, H

1992-11-01

32

Image quality enhancement by moving the image sensor  

Microsoft Academic Search

A full-color image is obtained from the interpolated RGB images by use of an appropriate demosaicing algorithms but some interpolation errors can not be avoidable. In this paper, new image capturing system is proposed which has an actuator to move the image sensor in two-axis and very simple image reconstruction algorithm, and can enhance the image quality since it does

Dong-Ki Min; Hoon-Sang Oh

2008-01-01

33

Dry versus conventional laser imagers: film properties and image quality.  

PubMed

The authors compared image quality and stability with a dry laser imager versus a conventional wet laser imager. Hard copies of 56 magnetic resonance imaging and computed tomographic studies were analyzed for gray-scale distribution and temperature stability. Results with the dry laser imager did not reach the quality of results with a wet laser imager, but the performance and ecologic criteria were sufficient to make use of this technique advantageous. PMID:10207495

Gahleitner, A; Kreuzer, S; Schick, S; Nowotny, R; Breitenseher, M; Solar, P; Czerny, C; Lang, T; Imhof, H

1999-03-01

34

Visual Importance Pooling for Image Quality Assessment  

Microsoft Academic Search

Recent image quality assessment (IQA) metrics achieve high correlation with human perception of image quality. Naturally, it is of interest to produce even better results. One promising method is to weight image quality measurements by visual importance. To this end, we describe two strategies-visual fixation-based weighting, and quality-based weighting. By contrast with some prior studies we find that these strategies

Anush Krishna Moorthy; Alan Conrad Bovik

2009-01-01

35

Image quality assessment in the low quality regime  

NASA Astrophysics Data System (ADS)

Traditionally, image quality estimators have been designed and optimized to operate over the entire quality range of images in a database, from very low quality to visually lossless. However, if quality estimation is limited to a smaller quality range, their performances drop dramatically, and many image applications only operate over such a smaller range. This paper is concerned with one such range, the low-quality regime, which is defined as the interval of perceived quality scores where there exists a linear relationship between the perceived quality scores and the perceived utility scores and exists at the low-quality end of image databases. Using this definition, this paper describes a subjective experiment to determine the low-quality regime for databases of distorted images that include perceived quality scores but not perceived utility scores, such as CSIQ and LIVE. The performances of several image utility and quality estimators are evaluated in the low-quality regime, indicating that utility estimators can be successfully applied to estimate perceived quality in this regime. Omission of the lowestfrequency image content is shown to be crucial to the performances of both kinds of estimators. Additionally, this paper establishes an upper-bound for the performances of quality estimators in the LQR, using a family of quality estimators based on VIF. The resulting optimal quality estimator indicates that estimating quality in the low-quality regime is robust to exact frequency pooling weights, and that near-optimal performance can be achieved by a variety of estimators providing that they substantially emphasize the appropriate frequency content.

Pinto, Guilherme O.; Hemami, Sheila S.

2012-02-01

36

Infrared image quality evaluation method without reference image  

NASA Astrophysics Data System (ADS)

Since infrared image quality depends on many factors such as optical performance and electrical noise of thermal imager, image quality evaluation becomes an important issue which can conduce to both image processing afterward and capability improving of thermal imager. There are two ways of infrared image quality evaluation, with or without reference image. For real-time thermal image, the method without reference image is preferred because it is difficult to get a standard image. Although there are various kinds of methods for evaluation, there is no general metric for image quality evaluation. This paper introduces a novel method to evaluate infrared image without reference image from five aspects: noise, clarity, information volume and levels, information in frequency domain and the capability of automatic target recognition. Generally, the basic image quality is obtained from the first four aspects, and the quality of target is acquired from the last aspect. The proposed method is tested on several infrared images captured by different thermal imagers. Calculate the indicators and compare with human vision results. The evaluation shows that this method successfully describes the characteristics of infrared image and the result is consistent with human vision system.

Yue, Song; Ren, Tingting; Wang, Chengsheng; Lei, Bo; Zhang, Zhijie

2013-09-01

37

Objective image quality measure derived from digital image power spectra  

NASA Astrophysics Data System (ADS)

An objective image quality measure based on the digital image power spectrum of normally acquired arbitrary scenes is developed. This image quality measure, which does not require imaging either designed targets or a constant scene, utilizes the previously known invariance property for the power spectra of arbitrary scenes. The measure incorporates a representation of the human visual system, a novel approach to account for directional differences in perspective (scale) for obliquely acquired scenes, and a filter developed to account for imaging system noise as specifically evidenced in the image power spectra. The primary application is to assess the quality of digital images relevant to the image task of detection, recognition, and identification of man-made objects from softcopy displayed versions of visible spectral region digital aerial images. Experimental verification is presented demonstrating very good correlation (r = 0.9) of this objective quality measure with visual quality assessments.

Nill, Norman B.; Bouzas, Brian H.

1992-04-01

38

ECG-synchronized DSA exposure control: improved cervicothoracic image quality  

SciTech Connect

An electrocardiogram (ECG)-synchronized x-ray exposure sequence was used to acquire digital subtraction angiographic (DSA) images during 13 arterial injection studies of the aortic arch or carotid bifurcations. These gated images were compared with matched ungated DSA images acquired using the same technical factors, contrast material volume, and patient positioning. Subjective assessments by five experienced observers of edge definition, vessel conspicuousness, and overall diagnostic quality showed overall preference for one of the two acquisition methods in 69% of cases studied. Of these, the ECG-synchronized exposure series were rated superior in 76%. These results, as well as the relatively simple and inexpensive modifications required, suggest that routine use of ECG exposure control can facilitate improved arterial DSA evaluations of suspected cervicothoracic vascular disease.

Kelly, W.M.; Gould, R.; Norman, D.; Brant-Zawadzki, M.; Cox, L.

1984-10-01

39

[Arterial switch operation for transposition of the great arteries with situs inversus and mirror image dextrocardia].  

PubMed

We report a successful arterial switch operation for complete transposition of great arteries with atrial and visceral situs inversus totalis and mirror image dextrocardia in a 12-day-old infant girl. The aorta was located left side-by-side to the pulmonary trunk with a single coronary artery (mirror image of 1RLCx). After French maneuver, the posterior circumference of the neo-aorta was reconstructed. Then the coronary button was transplanted into the neo-aorta with a trap door technique carefully avoiding any twist and over-stretch. The neo-pulmonary trunk was reconstructed with an autologous pericardial patch and sutured to the longitudinal incision made into the left central pulmonary artery. The baby was discharged from hospital and has been doing well without any morbidity relating myocardial ischemia. PMID:22940657

Uchida, Hiroaki; Nemoto, Shintaro; Ozawa, Hideki; Sasaki, Tomoyasu; Motohashi, Yoshikazu; Katsumata, Takahiro; Inoue, Nao; Kishi, Kanta; Okumura, Kenichi; Mori, Yasuhiko

2012-09-01

40

Dynamic diffuse optical tomography imaging of peripheral arterial disease  

PubMed Central

Peripheral arterial disease (PAD) is the narrowing of arteries due to plaque accumulation in the vascular walls. This leads to insufficient blood supply to the extremities and can ultimately cause cell death. Currently available methods are ineffective in diagnosing PAD in patients with calcified arteries, such as those with diabetes. In this paper we investigate the potential of dynamic diffuse optical tomography (DDOT) as an alternative way to assess PAD in the lower extremities. DDOT is a non-invasive, non-ionizing imaging modality that uses near-infrared light to create spatio-temporal maps of oxy- and deoxy-hemoglobin in tissue. We present three case studies in which we used DDOT to visualize vascular perfusion of a healthy volunteer, a PAD patient and a diabetic PAD patient with calcified arteries. These preliminary results show significant differences in DDOT time-traces and images between all three cases, underscoring the potential of DDOT as a new diagnostic tool.

Khalil, Michael A.; Kim, Hyun K.; Kim, In-Kyong; Flexman, Molly; Dayal, Rajeev; Shrikhande, Gautam; Hielscher, Andreas H.

2012-01-01

41

Process perspective on image quality evaluation  

NASA Astrophysics Data System (ADS)

The psychological complexity of multivariate image quality evaluation makes it difficult to develop general image quality metrics. Quality evaluation includes several mental processes and ignoring these processes and the use of a few test images can lead to biased results. By using a qualitative/quantitative (Interpretation Based Quality, IBQ) methodology, we examined the process of pair-wise comparison in a setting, where the quality of the images printed by laser printer on different paper grades was evaluated. Test image consisted of a picture of a table covered with several objects. Three other images were also used, photographs of a woman, cityscape and countryside. In addition to the pair-wise comparisons, observers (N=10) were interviewed about the subjective quality attributes they used in making their quality decisions. An examination of the individual pair-wise comparisons revealed serious inconsistencies in observers' evaluations on the test image content, but not on other contexts. The qualitative analysis showed that this inconsistency was due to the observers' focus of attention. The lack of easily recognizable context in the test image may have contributed to this inconsistency. To obtain reliable knowledge of the effect of image context or attention on subjective image quality, a qualitative methodology is needed.

Leisti, Tuomas; Halonen, Raisa; Kokkonen, Anna; Weckman, Hanna; Mettänen, Marja; Lensu, Lasse; Ritala, Risto; Oittinen, Pirkko; Nyman, Göte

2008-01-01

42

LGPS: Phase Based Image Quality Assessment Metric  

Microsoft Academic Search

Phase map of the images captures the most fundamental cognitive features and thus is widely used in various digital image processing tasks. In this paper, we propose the Log Gabor Phase Similarity (LGPS), a novel full reference image quality assessment metrics based on measuring of similarities between phases in log Gabor transform domain. Phase can capture any changes in image

Guangtao Zhai; Wenjun Zhang; Yi Xu; Weisi Lin

2007-01-01

43

JPEG2000 Still Image Coding Quality.  

PubMed

This work demonstrates the image qualities between two popular JPEG2000 programs. Two medical image compression algorithms are both coded using JPEG2000, but they are different regarding the interface, convenience, speed of computation, and their characteristic options influenced by the encoder, quantization, tiling, etc. The differences in image quality and compression ratio are also affected by the modality and compression algorithm implementation. Do they provide the same quality? The qualities of compressed medical images from two image compression programs named Apollo and JJ2000 were evaluated extensively using objective metrics. These algorithms were applied to three medical image modalities at various compression ratios ranging from 10:1 to 100:1. Following that, the quality of the reconstructed images was evaluated using five objective metrics. The Spearman rank correlation coefficients were measured under every metric in the two programs. We found that JJ2000 and Apollo exhibited indistinguishable image quality for all images evaluated using the above five metrics (r?>?0.98, p?image quality of the JJ2000 and Apollo algorithms is statistically equivalent for medical image compression. PMID:23589187

Chen, Tzong-Jer; Lin, Sheng-Chieh; Lin, You-Chen; Cheng, Ren-Gui; Lin, Li-Hui; Wu, Wei

2013-10-01

44

Cognitive issues in image quality measurement  

NASA Astrophysics Data System (ADS)

Designers of imaging systems, image processing algorithms, etc., usually take for granted that methods for assessing perceived image quality produce unbiased estimates of the viewers' quality impression. Quality judgments, however, are affected by the judgment strategies induced by the experimental procedures. In this paper the results of two experiments are presented illustrating the influence judgment strategies can have on quality judgments. The first experiment concerns contextual effects due to the composition of the stimulus sets. Subjects assessed the sharpness of two differently composed sets of blurred versions of one static image. The sharpness judgments for the blurred images present in both stimulus sets were found to be dependent on the composition of the set as well as the scaling technique employed. In the second experiment subjects assessed either the overall quality or the overall impairment of manipulated and standard JPEG-coded images containing two main artifacts. The results indicate a systematic different between the quality and impairment judgments that could be interpreted as instruction-based different weighting of the two artifacts. Again, some influence of scaling techniques was observed. The results of both experiments underscore the important role judgment strategies play in the psychophysical evaluation of image quality. Ignoring this influence on quality judgments may lead to invalid conclusions about the viewers' impression of image quality.

de Ridder, Huib

2001-01-01

45

Phase congruency assesses hyperspectral image quality  

NASA Astrophysics Data System (ADS)

Blind image quality assessment (QA) is a tough task especially for hyperspectral imagery which is degraded by noise, distortion, defocus, and other complex factors. Subjective hyperspectral imagery QA methods are basically measured the degradation of image from human perceptual visual quality. As the most important image quality measurement features, noise and blur, determined the image quality greatly, are employed to predict the objective hyperspectral imagery quality of each band. We demonstrate a novel no-reference hyperspectral imagery QA model based on phase congruency (PC), which is a dimensionless quantity and provides an absolute measure of the significance of feature point. First, Log Gabor wavelet is used to calculate the phase congruency of frequencies of each band image. The relationship between noise and PC can be derived from above transformation under the assumption that noise is additive. Second, PC focus measure evaluation model is proposed to evaluate blur caused by different amounts of defocus. The ratio and mean factors of edge blur level and noise is defined to assess the quality of each band image. This image QA method obtains excellent correlation with subjective image quality score without any reference. Finally, the PC information is utilized to improve the quality of some bands images.

Shao, Xiaopeng; Zhong, Cheng

2012-10-01

46

Imaging in childhood arterial ischaemic stroke  

Microsoft Academic Search

There remains a misconception that arterial ischaemic stroke (AIS) is a rare childhood disorder. Approximately 2–6\\/100,000\\u000a children are affected annually, and it is one of the top ten causes of childhood death. Following the ictus, up to 25% of\\u000a children will have a recurrence, and two thirds of children will have a long-term disability with considerable socio-economic\\u000a burden. The established

Brynmor P. Jones; Vijya Ganesan; Dawn E. Saunders; W. “Kling” Chong

2010-01-01

47

Color image quality metric for realistic image rendition  

NASA Astrophysics Data System (ADS)

Realistic image rendition, concerning on color constancy and lightness, is usually qualified by subjective evaluation, involving uncertainly psychophysical course. Whether common objective image quality metrics can be adopted to evaluate the rendition results is studied in this paper. Several common objective image quality metrics such as RMES, PSNR, and a newly universal one named Q metric are introduced. Experiments show that it's applicable to take images under standard lighting conditions (e.g. D65) as reference images, which is necessary for objective assessment. Experiment results confirm that introduced objective image quality metrics can help to evaluate the lightness and color constancy ability of images, in case of taking images under standard lights as reference images.

Xiao, Man-jun; Chen, Si-Ying; Ni, Guo-qiang

2008-03-01

48

Image quality evaluation of light field photography  

Microsoft Academic Search

Light field photography captures 4D radiance information of a scene. Digital refocusing and digital correction of aberrations could be done after the photograph is taken. However, capturing 4D light field is costly and tradeoffs between different image quality metrics should be made and evaluated. This paper explores the effects of light field photography on image quality by quantitatively evaluating some

Qiang Fu; Zhiliang Zhou; Yan Yuan; Bin Xiangli

2011-01-01

49

Image quality of figured multilayered optics  

SciTech Connect

The reflectivity and resolution of a multilayer structure is strongly affected by the roughness at the interfaces between two successive layers and by the amount that the constituent materials will diffuse into one another at the interfaces. Performance is also affected by the variations in individual layer thicknesses and by inhomogeneities in the materials. These deviations from the ideal multilayer will also affect the quality of the image from a figured multilayer optical element. The theory used to model the effects of non-ideal multilayers on the image quality of figured optics will be discussed. The relationship between image quality and multilayer structure quality will be illustrated with several examples.

Peterson, B.G.; Knight, L.V.; Pew, H.K.

1985-01-01

50

Simultaneous Bilateral Magnetic Resonance Imaging of the Femoral Arteries in Peripheral Arterial Disease Patients  

PubMed Central

Purpose To image the femoral arteries in peripheral arterial disease (PAD) patients using a bilateral receive coil. Materials and Methods An eight-channel surface coil array for bilateral MRI of the femoral arteries at 3T was constructed and evaluated. Results The bilateral array enabled imaging of a 25-cm segment of the superficial femoral arteries (SFA) from the profunda to the popliteal. The array provided improved the signal-to-noise ratio (SNR) at the periphery and similar SNR in the middle of a phantom compared to three other commercially available coils (4-channel torso, quadrature head, whole body). Multicontrast bilateral images of the in vivo SFA with 1 mm inplane resolution made it possible to directly compare lesions in the index SFA to the corresponding anatomical site in the contralateral vessel without repositioning the patient or coil. A set of bilateral time-of-flight, T1-weighted, T2-weighted, and proton density-weighted images was acquired in a clinically acceptable exam time of ?45 minutes. Conclusion The developed bilateral coil is well suited for monitoring dimensional changes in atherosclerotic lesions of the SFA.

Brown, Ryan; Karmonik, Christof; Brunner, Gerd; Lumsden, Alan; Ballantyne, Christie; Johnson, Shawna; Wang, Yi; Morrisett, Joel

2013-01-01

51

Quality assurance for diagnostic imaging equipment  

SciTech Connect

This report addresses factors that influence production of an image. It contains the necessary information to enable the imaging physician to report the diagnostic findings to the referring physician. Some of these factors are human, other are inherent to technique and equipment. The subject of the report is quality assurance, i.e., all of the management practices instituted by the imaging physician, to assure highest quality medical care, but an essential element of quality assurance is quality control. The first three sections are concerned with quality assurance in general and the remainder with quality control in specific circumstances. This report provides a systematic approach to procedures which can ensure that the physician and the imaging facility consistently achieve their optimal performance. This in turn, ensures that there is optimal use of radiation and that radiation exposures to patient and staff are maintained at a level consistent with the principles of optimization of radiation protection espoused by the NCRP.

Not Available

1988-01-01

52

Image guidance for robotic minimally invasive coronary artery bypass  

Microsoft Academic Search

A novel system for image guidance in totally endoscopic coronary artery bypass (TECAB) is presented. Key requirement is the availability of 2D–3D registration techniques that can deal with non-rigid motion and deformation. Image guidance for TECAB is mainly required before the mechanical stabilisation of the heart, when the most dominant source of misregistration is the deformation and non-rigid motion of

Michael Figl; Daniel Rueckert; David J. Hawkes; Roberto Casula; Mingxing Hu; Ose Pedro; Dong Ping Zhang; Graeme P. Penney; Fernando Bello; Philip J. Edwards

2010-01-01

53

Image Guidance for Robotic Minimally Invasive Coronary Artery Bypass  

Microsoft Academic Search

A novel system for image guidance in totally endoscopic coronary artery bypass (TECAB) is presented. Key requirement is the\\u000a availability of 2D-3D registration techniques that can deal with non-rigid motion and deformation. Image guidance for TECAB\\u000a is mainly required before the mechanical stabilization of the heart, thus the most dominant source of non-rigid deformation\\u000a is the motion of the beating

Michael Figl; Daniel Rueckert; David J. Hawkes; Roberto Casula; Mingxing Hu; Ose Pedro; Dong Ping Zhang; Graeme P. Penney; Fernando Bello; Philip J. Edwards

2008-01-01

54

Dobutamine Stress Myocardial Perfusion Imaging in Coronary Artery Disease  

Microsoft Academic Search

The accurate noninvasive diagnosis and functional evaluation of coronary artery disease is an important step in selecting the appropriate management strategy. Dobutamine stress myocar- dial perfusion imaging is an alternative to exercise in patients with limited exercise capacity. In many centers, the test is performed on patients who have a contraindication for vasodi- lator stress testing. Recent studies have shown

Abdou Elhendy; Jeroen J. Ba; Don Poldermans

55

NMR (Nuclear Magnetic Resonance) Imaging of Human Coronary Arteries.  

National Technical Information Service (NTIS)

Nuclear magnetic resonance imaging (MRI) is being studied as a method to detect the presence of atherosclerotic lesions in the coronary arteries of humans in a totally non-invasive manner, and to characterize the anatomic features of these lesions. For th...

L. Kaufman L. Crooks C. Higgins J. Hale

1984-01-01

56

Role of radionuclide cardiac imaging in coronary artery bypass surgery  

SciTech Connect

The main applications of cardiac nuclear imaging in coronary artery bypass surgery include: patient selection, prediction of improvement in resting LV function after revascularization, diagnosis of perioperative myocardial infarction, assessment of the results of revascularization, evaluation of new or recurrent symptoms, and in risk stratification. Proper understanding of which test to be used, when, and why may be important to optimize patient management.

Iskandrian, A.S.; Heo, J.; Mostel, E.

1987-01-01

57

Does resolution really increase image quality?  

Microsoft Academic Search

A general trend in the CMOS image sensor market is for increasing resolution (by having a larger number of pixels) while keeping a small form factor by shrinking photosite size. This article discusses the impact of this trend on some of the main attributes of image quality. The first example is image sharpness. A smaller pitch theoretically allows a larger

Christel-Loïc Tisse; Frédéric Guichard; Frédéric Cao

2008-01-01

58

Estimation error in image quality measurements  

Microsoft Academic Search

The development and adoption of standard image quality measurement and analysis methods have helped both the evaluation of competing imaging products and in technologies. Inherent in the interpretation of results from any particular evaluation, however, are the variation of the method itself, the sampling of test images, equipment, and test conditions. Here we take a statistical approach to measurement variation,

Peter D. Burns

2011-01-01

59

Comparably improved health-related quality of life after total arterial revascularization versus conventional coronary surgery—Copenhagen arterial revascularization randomized patency and outcome trial  

Microsoft Academic Search

Objective: We compared health-related quality of life up to 11 months after coronary artery bypass grafting using total arterial revascularization versus conventional coronary surgery. Methods: In this randomized single-center trial, 161 patients underwent total arterial revascularization using single or bilateral internal thoracic artery (ITA) and radial artery grafts versus 170 patients conventionally revascularized using left ITA and saphenous vein grafts.

Sune Damgaard; Jens T. Lund; Nikolaj B. Lilleør; Mario J. Perko; Jan K. Madsen; Daniel A. Steinbrüchel

2011-01-01

60

Quality of life improves after renal artery stenting.  

PubMed

Although treatment of renal artery stenosis (RAS) with stents has been shown to improve blood pressure (BP) and renal function in some patients, little is known about the effect on health-related quality of life. A composite quality of life survey was administered in a cross-sectional cohort fashion to 149 patients presenting with angiographically and hemodynamically confirmed RAS either before (baseline, n = 37) or after (follow-up, n = 112) stent revascularization. BP, renal function, and antihypertensive medication use were also assessed. Systolic BP was lower in the revascularized patients (166 +/- 23 vs. 153 +/- 26, p < .01). The Short Form-36 Physical Component Summary (PCS) scores were higher (better) in revascularized patients (37 +/- 9 vs. 31 +/- 9, p < .01), whereas Mental Component Summary scores were equivalent (49 +/- 13 vs. 51 +/- 11, p = ns). Sleep dysfunction scores were lower (better) in the revascularized patients (32 +/- 26 vs. 48 +/- 32, p < .001), whereas self-reported appetite was higher (better; 62% +/- 29% vs. 73% +/- 27%,p < .05). After matching for age and gender, Short Form-36 PCS remained higher in the revascularized cohort (37 +/- 8 vs. 32 +/- 8, p < .05). Importantly, in multivariate analysis, revascularization was the most significant determinant of a higher PCS score (r2 = .07, beta = 5.21, p < .01). The current data suggest that renal artery stenting may improve health-related quality of life in patients with renovascular disease. PMID:17003252

Kennedy, David J; Burket, Mark W; Khuder, Sadik A; Shapiro, Joseph I; Topp, Robert V; Cooper, Christopher J

2006-10-01

61

MDCT-imaging of peripheral arterial disease  

Microsoft Academic Search

With the design and development of advanced computed tomography (CT) techniques and applications, like the newest generation of 16-detector-row CTs, CT angiography of the lower limb becomes a feasible tool for imaging peripheral vascular disease. Due to several advantages, compared with conventional digital subtraction angiography (DSA), including minimal invasiveness, CT angiography competes against diagnostic DSA in several clinical situations. 16-DCT

Tobias F Jakobs; Bernd J Wintersperger; Christoph R Becker

2004-01-01

62

Three-dimensional color Doppler imaging of the carotid artery  

NASA Astrophysics Data System (ADS)

Stroke is the third leading cause of death in the United States. It is caused by ischemic injury to the brain, usually resulting from emboli from atherosclerotic plaques. The carotid bifurcation in humans is prone to atherosclerotic disease and is a site where emboli may originate. Currently, carotid stenoses are evaluated by non-invasive duplex Doppler ultrasound, with preoperative verification by intra-arterial angiography. We have developed a system that uses a color Doppler ultrasound imaging system to acquire in-vivo 3-D color Doppler images of the human carotid artery, with the aim of increasing the diagnostic accuracy of ultrasound and decreasing the use of angiography for verification. A clinical TL Ultramark 9 color Doppler ultrasound system was modified by mounting the hand-held ultrasound scan head on a motor-driven translation stage. The stage allows planar ultrasound images to be acquired over 45 mm along the neck between the clavicle and the mandible. A 3- D image is acquired by digitizing, in synchrony with the cardiac cycle, successive color ultrasound video images as the scan head is stepped along the neck. A complete volume set of 64 frames, comprising some 15 megabytes of data, requires approximately 2 minutes to acquire. The volume image is reformatted and displayed on a Sun 4/360 workstation equipped with a TAAC-1 graphics accelerator. The 3-D image may be manipulated in real time to yield the best view of blood flow in the bifurcation.

Picot, Paul A.; Rickey, Daniel W.; Mitchell, J. Ross; Rankin, Richard N.; Fenster, Aaron

1991-05-01

63

End-to-end image quality assessment  

NASA Astrophysics Data System (ADS)

An innovative computerized benchmarking approach (US Patent pending Sep 2011) based on extensive application of photometry, geometrical optics, and digital media using a randomized target, for a standard observer to assess the image quality of video imaging systems, at different day time, and low-light luminance levels. It takes into account, the target's contrast and color characteristics, as well as the observer's visual acuity and dynamic response. This includes human vision as part of the "extended video imaging system" (EVIS), and allows image quality assessment by several standard observers simultaneously.

Raventos, Joaquin

2012-05-01

64

Computerized assessment and tracking of cardiac angiographic image quality  

NASA Astrophysics Data System (ADS)

With the rising prominence of filmless and quantitative imaging technologies in modern cardiac catheterization laboratories, new approaches to assessing angiographic image quality (AIQ) are required. This paper describes a system of radiographic phantom modules and associated digital image analysis software for assessing and tracking the inherent low contrast AIQ of a particular image chain as well as its suitability for quantitative coronary arteriography (QCA) analysis. The system uses two phantom modules in conjunction with a patient simulation apparatus. Computer software operates on digital radiographic images of the phantoms and extracts a number of parameters characterizing the imaging performance of the particular image chain. An arterial phantom module is used to evaluate angiographic imaging performance relating to QCA and an orthogonal array of small bronze ball bearings is used to derive AIQ parameters that complement standard manual measurements. In addition to passively monitoring AIQ, this new approach has the benefit of enabling active compensation for variability in AIQ and its effect on QCA results from one image chain to the next.

Lefree, Michelle T.; Krus, Daniel L.; Sitomer, Joseph

1998-07-01

65

Image Quality Metrics for Color CRT Displays.  

National Technical Information Service (NTIS)

This study explores several different image quality metrics currently employed by the visual display community in the context of color CRT display technology. The specific techniques included in the study are the Modulation Transfer Function, the Contrast...

R. J. Beaton W. W. Farley

1994-01-01

66

Image quality and wafer level optics  

NASA Astrophysics Data System (ADS)

Increasing demand from consumers to integrate camera modules into electronic devices, such as cell phones, has driven the cost of camera modules down very rapidly. Now that most cell phones include at least one camera, consumers are starting to ask for better image quality - without compromising on the cost. Wafer level optics has emerged over the past few years as an innovative technology enabling simultaneous manufacturing of thousands of lenses, at the wafer level. Using reflow-compatible materials to manufacture these lenses permits a reduction in the cost and size of camera module, thus answering the market demand for lowering the cost. But what about image quality? The author will present image quality analysis that was conducted for both VGA and megapixel camera resolutions. Comparison between conventional camera modules and wafer level camera modules shows wafer level technology brings equivalent, if not better, image quality performance compared to conventional camera modules.

Dagan, Y.; Humpston, G.

2010-04-01

67

Rendered virtual view image objective quality assessment  

NASA Astrophysics Data System (ADS)

The research on rendered virtual view image (RVVI) objective quality assessment is important for integrated imaging system and image quality assessment (IQA). Traditional IQA algorithms cannot be applied directly on the system receiver-side due to interview displacement and the absence of original reference. This study proposed a block-based neighbor reference (NbR) IQA framework for RVVI IQA. Neighbor views used for rendering are employed for quality assessment in the proposed framework. A symphonious factor handling noise and interview displacement is defined and applied to evaluate the contribution of the obtained quality index in each block pair. A three-stage experiment scheme is also presented to testify the proposed framework and evaluate its homogeneity performance when comparing to full reference IQA. Experimental results show the proposed framework is useful in RVVI objective quality assessment at system receiver-side and benchmarking different rendering algorithms.

Lu, Gang; Li, Xiangchun; Zhang, Yi; Peng, Kai

2013-08-01

68

Steganalysis using image quality metrics  

Microsoft Academic Search

Abstract: We present techniques for steganalysis of images thathave been potentially subjected to steganographic algorithms, bothwithin the passive warden and active warden frameworks. Our hypothesisis that steganographic schemes leave statistical evidencethat can be exploited for detection with the aid of image qualityfeatures and multivariate regression analysis. To this effect imagequality metrics have been identified based on the analysis of variance(ANOVA)

Ismail Avcibas; Nasir D. Memon; Bülent Sankur

2003-01-01

69

Image quality metrics for color CRT displays  

NASA Astrophysics Data System (ADS)

This study explores several different image quality metrics currently employed by the visual display community in the context of color CRT display technology. The specific techniques included in the study are the Modulation Transfer Function, the Contrast Threshold/Sensitivity Function, the Modulation Transfer Function Area, the Integrated Contrast Sensitivity metric, and the Square-Root Integral metric. These metrics include and are based on visual psychometric data and suggest that operator performance may be predicted from the objective, image quality data.

Beaton, Robert J.; Farley, Willard W.

1994-08-01

70

Image quality evaluation using moving targets  

NASA Astrophysics Data System (ADS)

The basic concept of testing a digital imaging device is to reproduce a known target and to analyze the resulting image. This semi-reference approach can be used for various different aspects of image quality. Each part of the imaging chain can have an influence on the results: lens, sensor, image processing and the target itself. The results are valid only for the complete system. If we want to test a single component, we have to make sure that we change only one and keep all others constant. When testing mobile imaging devices, we run into the problem that hardly anything can be manually controlled by the tester. Manual exposure control is not available for most devices, the focus cannot be influenced and hardly any settings for the image processing are available. Due to the limitations in the hardware, the image pipeline in the digital signal processor (DSP) of mobile imaging devices is a critical part of the image quality evaluation. The processing power of the DSPs allows sharpening, tonal correction and noise reduction to be non-linear and adaptive. This makes it very hard to describe the behavior for an objective image quality evaluation. The image quality is highly influenced by the signal processing for noise and resolution and the processing is the main reason for the loss of low contrast, _ne details, the so called texture blur. We present our experience to describe the image processing in more detail. All standardized test methods use a defined chart and require, that the chart and the camera are not moved in any way during test. In this paper, we present our results investigating the influence of chart movement during the test. Different structures, optimized for different aspects of image quality evaluation, are moved with a defined speed during the capturing process. The chart movement will change the input for the signal processing depending on the speed of the target during the test. The basic theoretical changes in the image will be the introduction of motion blur. With the known speed and the measured exposure time, we can calculate the theoretical motion blur. We compare the theoretical influence of the motion blur with the measured results. We use different methods to evaluate image quality parameter vs. motion speed of the chart. Slanted edges are used to obtain a SFR and to check for image sharpening. The aspect of texture blur is measured using dead leaves structures. The theoretical and measured results are plotted against the speed of the chart and allow an insight into the behavior of the DSP.

Artmann, Uwe

2013-03-01

71

Correlative magnetic resonance imaging in the evaluation of aortic and pulmonary artery abnormalities  

SciTech Connect

Magnetic resonance imaging (MRI) yields excellent quality images of the cardiovascular system utilizing the inherent natural contrast between flowing blood and the surrounding anatomic structures. To evaluate the clinical usefulness of MRI in the noninvasive diagnosis of large vessel disorders, the authors have performed MRI on 40 pts with either aortic or pulmonary artery abnormalities (18 thoracic or abdominal aortic aneurysms, 8 aorto-occlusive disease, 6 dissecting aneurysms, 4 Marfan's syndrome, 2 pulmonary artery aneurysms 1 pulmonary artery occlusion, 1 aortic coarctation). Images were obtained in the transverse, coronal and sagital body planes utilizing a 0.6T superconductive magnet. Cardiac and/or respiratory gating was employed in most cases. Correlation was made for all studies with conventional or digital subtraction angiography, computed tomography, and/or ultrasound. The diagnostic information obtained by MRI equaled or exceeded that obtained by other imaging techniques except for the few cases where cardiac arrhythmias precluded adequate gated acquisition. All aneurysms and their relationships to adjacent structures were readily demonstrated as were the presence or absence of mural thrombi and dissecting intimal flaps. Angiographically demonstrated atherosclerotic plaques and luminal stenoses were seen by MRI in all patients without arrhythmias. The authors concluded that MRI is a powerful noninvasive diagnostic aid in the delineation of large vessel disorders, especially where knowledge of anatomic interrelationships can guide surgical or other interventional planning.

Risius, B.; O'Donnell, J.K.; Geisinger, M.A.; Zelch, M.G.; George, C.R.; Graor, R.A.; Moodie, D.S.

1985-05-01

72

Functional magnetic resonance imaging in renal artery stenosis  

Microsoft Academic Search

Renal artery stenosis (RAS) is the leading cause of secondary hypertension. Magnetic resonance (MR) imaging and in particular\\u000a MR angiography have evolved into important diagnostic tools for the detection and grading of RAS due to the lack of ionizing\\u000a radiation and nephrotoxic contrast agent. This review describes state-of-the-art MR angiographic techniques and introduces\\u000a the reader to current concepts of RAS

S. O. Schoenberg; J. R. Rieger; H. J. Michaely; H. Rupprecht; W. Samtleben; M. F. Reiser

2006-01-01

73

Magnetic resonance imaging in the assessment of coronary artery disease  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is gaining importance in cardiology as the noninvasive test of choice for patients with a\\u000a multitude of cardiovascular problems. Recently, cardiovascular MRI has emerged as an important noninvasive diagnostic modality\\u000a in the assessment of coronary artery disease. Because of its superior spatial resolution, integration of qualitative and quantitative\\u000a methodology, and excellent reproducibility, MRI has advantages over

Tarang Ray; Robert W. Biederman; Mark Doyle; Sunil Mankad

2005-01-01

74

Image Quality in Sampled Data Systems.  

National Technical Information Service (NTIS)

The paper deals with aliasing, an important effect of one-and two-dimensional sampling on image quality. Aliasing changes the normal criteria of utility of the modulation transfer function (MTF) as a measure of system quality. Aliasing can be eliminated b...

A. F. Milton F. A. Rosell L. M. Biberman O. H. Schade R. Legault

1971-01-01

75

Image quality measures and their performance  

Microsoft Academic Search

A number of quality measures are evaluated for gray scale image compression. They are all bivariate, exploiting the differences between corresponding pixels in the original and degraded images. It is shown that although some numerical measures correlate well with the observers' response for a given compression technique, they are not reliable for an evaluation across different techniques. A graphical measure

Ahmet M. Eskicioglu; Paul S. Fisher

1995-01-01

76

Color image processing for date quality evaluation  

Microsoft Academic Search

Many agricultural non-contact visual inspection applications use color image processing techniques because color is often a good indicator of product quality. Color evaluation is an essential step in the processing and inventory control of fruits and vegetables that directly affects profitability. Most color spaces such as RGB and HSV represent colors with three-dimensional data, which makes using color image processing

Dah Jye Lee; James K. Archibald

2010-01-01

77

Imaging and management of atherosclerotic renal artery stenosis.  

PubMed

Renal artery stenosis (RAS) causes chronic, progressive ischaemic nephropathy and is the most common cause of secondary hypertension. Radiology plays a large part in the diagnosis, with a variety of imaging techniques available. Each has relative advantages and disadvantages depending on each unique clinical setting. We discuss and illustrate the range of diagnostic methods and interventional techniques for diagnosis and management of RAS and review the current evidence base for endovascular therapy compared with optimal medical management. Knowledge of the relative merits of the various forms of imaging and treatment will guide decision making in the multidisciplinary setting. PMID:23317970

Sarkodieh, J E; Walden, S H; Low, D

2013-01-11

78

Noncontrast MR Angiography for Comprehensive Assessment of Abdominopelvic Arteries using Quadruple Inversion-Recovery Preconditioning and 3D balanced Steady-State Free Precession Imaging  

PubMed Central

Purpose To develop a non-contrast MR angiography (MRA) method for comprehensive evaluation of abdominopelvic arteries in a single 3D acquisition. Materials and Methods A non-contrast MRA (NC MRA) pulse sequence was developed using 4 inversion-recovery (IR) pulses and 3D balanced steady-state free precession (b-SSFP) readout to provide arterial imaging from renal to external iliac arteries. Respiratory triggered, high spatial resolution (1.3 × 1.3 × 1.7 mm3) non-contrast angiograms were obtained in seven volunteers and ten patients referred for gadolinium-enhanced MRA (CE MRA). Images were assessed for diagnostic quality by two radiologists. Quantitative measurements of arterial signal contrast were also performed. Results NC MRA imaging was successfully completed in all subjects in 7.0 ± 2.3 minutes. In controls, image quality of NC MRA averaged 2.79 ± 0.39 on a scale of 0 to 3, where 3 is maximum. Image quality of NC MRA (2.65 ± 0.41) was comparable to that of CE MRA (2.9 ± 0.32) in all patients. Contrast ratio measurements in patients demonstrated that NC MRA provides arterial contrast comparable to source CE MRA images with adequate venous and excellent background tissue suppression. Conclusion The proposed non-contrast MRA pulse sequence provides high quality visualization of abdominopelvic arteries within clinically feasible scan times.

Atanasova, Iliyana P.; Kim, Daniel; Lim, Ruth P.; Storey, Pippa; Kim, Sooah; Guo, Hua; Lee, Vivian S.

2011-01-01

79

Image quality measures for hierarchical decomposition of a shoeprint image  

Microsoft Academic Search

In an automated shoeprint classification and retrieval system, several practical difficulties exist hindering the effectiveness of shoeprint classification, such as device-dependent noise, distortions, and incompleteness. This makes it desirable to estimate the quality of a shoeprint image before it is fed into the process of feature extraction. It helps the system decide the types of image denoising, enhancement, and restoration

H. Su; A. Bouridane; D. Crookes

2006-01-01

80

Color image processing for date quality evaluation  

NASA Astrophysics Data System (ADS)

Many agricultural non-contact visual inspection applications use color image processing techniques because color is often a good indicator of product quality. Color evaluation is an essential step in the processing and inventory control of fruits and vegetables that directly affects profitability. Most color spaces such as RGB and HSV represent colors with three-dimensional data, which makes using color image processing a challenging task. Since most agricultural applications only require analysis on a predefined set or range of colors, mapping these relevant colors to a small number of indexes allows simple and efficient color image processing for quality evaluation. This paper presents a simple but efficient color mapping and image processing technique that is designed specifically for real-time quality evaluation of Medjool dates. In contrast with more complex color image processing techniques, the proposed color mapping method makes it easy for a human operator to specify and adjust color-preference settings for different color groups representing distinct quality levels. Using this color mapping technique, the color image is first converted to a color map that has one color index represents a color value for each pixel. Fruit maturity level is evaluated based on these color indices. A skin lamination threshold is then determined based on the fruit surface characteristics. This adaptive threshold is used to detect delaminated fruit skin and hence determine the fruit quality. The performance of this robust color grading technique has been used for real-time Medjool date grading.

Lee, Dah Jye; Archibald, James K.

2010-01-01

81

Perceptual image quality and telescope performance ranking  

NASA Astrophysics Data System (ADS)

Launch Vehicle Imaging Telescopes (LVIT) are expensive, high quality devices intended for improving the safety of vehicle personnel, ground support, civilians, and physical assets during launch activities. If allowed to degrade from the combination of wear, environmental factors, and ineffective or inadequate maintenance, these devices lose their ability to provide adequate quality imagery to analysts to prevent catastrophic events such as the NASA Space Shuttle, Challenger, accident in 1986 and the Columbia disaster of 2003. A software tool incorporating aberrations and diffraction that was developed for maintenance evaluation and modeling of telescope imagery is presented. This tool provides MTF-based image quality metric outputs which are correlated to ascent imagery analysts' perception of image quality, allowing a prediction of usefulness of imagery which would be produced by a telescope under different simulated conditions.

Lentz, Joshua K.; Harvey, James E.; Marshall, Kenneth H.; Salg, Joseph; Houston, Joseph B.

2010-08-01

82

Analysis of the general image quality equation  

NASA Astrophysics Data System (ADS)

The general image quality equation (GIQE) [Leachtenauer et al., Appl. Opt. 36, 8322-8328 (1997)] is an empirical formula for predicting the quality of imagery from a given incoherent optical system in terms of the National Imagery Interpretability Rating Scale (NIIRS). In some scenarios, the two versions of the GIQE (versions 3.0 and 4.0) yield significantly different NIIRS predictions. We compare visual image quality assessments for simulated imagery with GIQE predictions and analyze the physical basis for the GIQE terms in an effort to determine the proper coefficients for use with Wiener-filtered reconstructions of Nyquist and oversampled imagery in the absence of aberrations. Results indicate that GIQE 3.0 image quality predictions are more accurate than those from GIQE 4.0 in this scenario.

Thurman, Samuel T.; Fienup, James R.

2008-05-01

83

Imaging the Vessel Wall in Major Peripheral Arteries using Susceptibility Weighted Imaging  

PubMed Central

Purpose To demonstrate a novel contrast mechanism for imaging the vessel wall and vessel wall calcification using susceptibility weighted imaging (SWI). Materials and Methods 18 subjects were imaged with multi-detector computed tomography (MDCT) and high resolution SWI at 3T. The SWI imaging parameters were optimized to allow for the best visualization of the femoral artery lumen and the arterial wall in magnitude and phase images, respectively. SWI filtered phase data were used to evaluate the diamagnetic susceptibility of vessel wall and of putative vessel wall calcification. Imaging was performed using TE = 15.6 ms (in-phase for fat); TR = 25 ms, FA = 10°, BW = 80 Hz/pixel, resolution = 0.5mm ×0.5mm in-plane and 1.0mm through-plane, an acquisition matrix of 512 × 384 × 64 (for read, phase and slice-select directions) and a total scan time of 8 minutes. Results Nineteen calcifications were identified in CT and SWI and they correlated well in both size and position. The contrast-to-noise ratio between the blood signal in the lumen of the artery and arterial wall was 11.7:1 and 7.4:1 in magnitude and in phase images, respectively. Conclusion SWI provides a novel means to visualize vessel wall and recognize the presence of calcification.

Yang, Qi; Liu, Jiantao; Barnes, Samuel R.S.; Wu, Zhen; Li, Kuncheng; Neelavalli, Jaladhar; Hu, Jiani; Haacke, E. Mark

2009-01-01

84

ImageHealth: Quality Assurance for Large FITS Images  

NASA Astrophysics Data System (ADS)

ImageHealth (IH) is a c program that makes use of standard CFITSIO routines to examine, in an automated fashion, .FITS images with any number of extensions, find objects within those images, and determine basic parameters of those images (stellar flux, background counts, FWHM, and ellipticity, along with sky background counts) in order to provide a snapshot of the quality of those images. A variety of python wrappers have also been written to test large numbers of such images and compare the results of ImageHealth to other image analysis programs, such as SourceExtractor. Additional IH-related tools will be made available in the future. Efforts are now focused on an implementation of IH specifically for the Dark Energy Camera; we do not envision providing support for the instrument-independent version of the code offered here though comments, questions, and feedback are welcome.

Kuehn, Kyler; Hupe, Ryan

2012-06-01

85

Time trends of chest pain symptoms and health related quality of life in coronary artery disease  

Microsoft Academic Search

BACKGROUND: There is at present a lack of knowledge of time trends in health related quality of life (HRQL) in common patients with coronary artery disease (CAD) treated in ordinary care. The objective of this study is to assess and compare time trends of health related quality of life (HRQL) and chest pain in patients with coronary artery disease. METHODS:

Anna Kiessling; Peter Henriksson

2007-01-01

86

Multiimage formatting: effect on scintillation image quality  

SciTech Connect

Multiimage formatters designed for use with scintillation cameras allow convenient presentation of as many as 90 images on a single film. Three different multiimagers (Searle Microdot 3132, Toshiba Gamma Imager GMI-04A, and Matrix Multi-imager 4) were evaluated with phantoms. Image quality was not equivalent in all positions on the resultant film, and was unacceptable in some cases. Individual laboratories should be aware of the potential loss of diagnostic information when using multiimage formatters and should evaluate their devices for this potential problem.

Fajman, W.A.; Sarper, R.

1982-10-01

87

Definition of Fingerprint Scanner Image Quality Specifications by Operational Quality  

Microsoft Academic Search

This paper analyzes two recently released image quality specifications for single-finger scanners and proposes three new specifications targeted to different types of applications. A comparison of the potential effects on fingerprint recognition accuracy of the various specifications is carried out using an approach based on the definition of \\

A. Alessandroni; Raffaele Cappelli; Matteo Ferrara; Davide Maltoni

2008-01-01

88

Indium-111 labeled leukocyte imaging following hepatic artery embolization  

SciTech Connect

The use of In-111 labeled leukocytes for abscess localization is becoming well established. The first report of In-111 imaging following hepatic embolization is presented. A 45-year-old man with adenocarcinoma of the colon and metastatic liver disease was treated for intractable pain using particulate embolization of the hepatic artery. In-111 leukocyte imaging was performed to rule out abscess formation. The distribution of the labeled leukocytes demonstrated hepatic uptake commensurate with Tc-99m sulfur colloid (SC) images. Areas of embolization did not accumulate tracer. Pathologic examination at autopsy correlated with the distribution of the labeled leukocytes. Thus, therapeutic embolization did not alter the normal distribution of this tracer in functional hepatic tissue.

Witte, R.J.; Petersen, R.J.; Augustine, S.C.; Elson, J.D.

1986-05-01

89

Quality indicators of image-based overlay  

NASA Astrophysics Data System (ADS)

A new method for indicating the image quality of overlay measurement is proposed in this paper. Due to the constraint of the overlay control tolerance, the overlay metrology requirement has become very stringent. Current indicators such as the total measurement uncertainty (TMU) are insufficient to guarantee a good overlay measurement. This paper describes two quality indicators, the contrast index (CI) and the asymmetry index (AI). The CI is a crucial quality indicator that affects the overlay accuracy greatly. The AI, based on an imaging process with modified cross-correlation operation, shows alignment mark robustness in both the x and the y directions. For determination of the best recipe, the box-in-box overlay marks are measured to obtain the images with different conditions. The conventional TMU indicators are used first to sieve out the better choices. Then the CI and AI can help to judge whether the overlay results are reliable and can be applied to monitoring of process variations.

Chen, Yen-Liang; Huang, Jacky; Lee, Rita; Wang, Chen-Ming; Ke, Chih-Ming; Gau, Tsai-Sheng

2012-03-01

90

Myocardial perfusion imaging with technetium-99m sestamibi SPECT in the evaluation of coronary artery disease  

SciTech Connect

Technetium-99m (Tc-99m) sestamibi is a new myocardial perfusion imaging agent that offers significant advantages over thallium-201 (Tl-201) for myocardial perfusion imaging. The results of the current clinical trials using acquisition and processing parameters similar to those for Tl-201 and a separate (2-day) injection protocol suggest that Tc-99m sestamibi and Tl-201 single photon emission computed tomography (SPECT) provide similar information with respect to detection of myocardial perfusion defects, assessment of the pattern of defect reversibility, overall detection of coronary artery disease (CAD) and detection of disease in individual coronary arteries. Tc-99m sestamibi SPECT appears to be superior to Tc-99m sestamibi planar imaging because the former provides a higher defect contrast and is more accurate for detection of disease in individual coronary arteries. Research is currently under way addressing optimization of acquisition and processing of Tc-99m sestamibi studies and development of quantitative algorithms for detection and localization of CAD and sizing of transmural and nontransmural myocardial perfusion defects. It is expected that with the implementation of the final results of these new developments, further significant improvement in image quality will be attained, which in turn will further increase the confidence in image interpretation. Development of algorithms for analysis of end-diastolic myocardial images may allow better evaluation of small and nontransmural myocardial defects. Furthermore, gated studies may provide valuable information with respect to regional myocardial wall motion and wall thickening. With the implementation of algorithms for attenuation and scatter correction, the overall specificity of Tc-99m sestamibi SPECT should improve significantly. 32 references.

Maddahi, J.; Kiat, H.; Van Train, K.F.; Prigent, F.; Friedman, J.; Garcia, E.V.; Alazraki, N.; DePuey, E.G.; Nichols, K.; Berman, D.S. (Cedars-Sinai Medical Center, Los Angeles, CA (USA))

1990-10-16

91

Comparative imaging study in ultrasound, MRI, CT, and DSA using a multimodality renal artery phantom  

SciTech Connect

Purpose: A range of anatomically realistic multimodality renal artery phantoms consisting of vessels with varying degrees of stenosis was developed and evaluated using four imaging techniques currently used to detect renal artery stenosis (RAS). The spatial resolution required to visualize vascular geometry and the velocity detection performance required to adequately characterize blood flow in patients suffering from RAS are currently ill-defined, with the result that no one imaging modality has emerged as a gold standard technique for screening for this disease. Methods: The phantoms, which contained a range of stenosis values (0%, 30%, 50%, 70%, and 85%), were designed for use with ultrasound, magnetic resonance imaging, x-ray computed tomography, and x-ray digital subtraction angiography. The construction materials used were optimized with respect to their ultrasonic speed of sound and attenuation coefficient, MR relaxometry (T{sub 1},T{sub 2}) properties, and Hounsfield number/x-ray attenuation coefficient, with a design capable of tolerating high-pressure pulsatile flow. Fiducial targets, incorporated into the phantoms to allow for registration of images among modalities, were chosen to minimize geometric distortions. Results: High quality distortion-free images of the phantoms with good contrast between vessel lumen, fiducial markers, and background tissue to visualize all stenoses were obtained with each modality. Quantitative assessments of the grade of stenosis revealed significant discrepancies between modalities, with each underestimating the stenosis severity for the higher-stenosed phantoms (70% and 85%) by up to 14%, with the greatest discrepancy attributable to DSA. Conclusions: The design and construction of a range of anatomically realistic renal artery phantoms containing varying degrees of stenosis is described. Images obtained using the main four diagnostic techniques used to detect RAS were free from artifacts and exhibited adequate contrast to allow for quantitative measurements of the degree of stenosis in each phantom. Such multimodality phantoms may prove useful in evaluating current and emerging US, MRI, CT, and DSA technology.

King, Deirdre M.; Fagan, Andrew J.; Moran, Carmel M.; Browne, Jacinta E. [Medical Ultrasound Physics and Technology Group, School of Physics, Dublin Institute of Technology, Dublin 8 (Ireland); Centre for Advanced Medical Imaging (CAMI), St James's Hospital, Dublin 8 (Ireland); Department of Medical Physics, University of Edinburgh, Edinburgh EH16 4TJ (United Kingdom); Medical Ultrasound Physics and Technology Group, School of Physics, Dublin Institute of Technology, Dublin 8 (Ireland)

2011-02-15

92

Guides to Quality in Visual Resource Imaging  

NSDL National Science Digital Library

On July 17, the Research Libraries Group (RLG), Digital Libraries Federation (DLF), and the Council on Library and Information Resources announced a new set of five guides to the technical and planning aspects of digital imaging of visual resources. As the official press release notes, "this new Web-based reference is designed to serve the growing community of museums, archives, and research libraries that are turning to digital conversion to provide greater access to their visual resources as well as to help preserve the original materials." The guides include "Planning a Digital Imaging Project"; "Selecting a Scanner"; "Imaging Systems: the Range of Factors Affecting Image Quality"; "Measuring Quality of Digital Masters"; and "File Formats for Digital Masters." All are offered in HTML format, and users's comments are encouraged for future updates.

93

Analysis of the general image quality equation  

Microsoft Academic Search

The general image quality equation (GIQE) [Leachtenauer et al., Appl. Opt. 36, 8322-8328 (1997)] is an empirical formula for predicting the quality of imagery from a given incoherent optical system in terms of the National Imagery Interpretability Rating Scale (NIIRS). In some scenarios, the two versions of the GIQE (versions 3.0 and 4.0) yield significantly different NIIRS predictions. We compare

Samuel T. Thurman; James R. Fienup

2008-01-01

94

Analysis of the general image quality equation  

Microsoft Academic Search

The general image quality equation (GIQE) (Leachtenauer et al., Appl. Opt. 36, 8322-8328 (1997)) is an empirical formula for predicting the quality of imagery from a given incoherent optical system in terms of the National Imagery Interpretability Rating Scale (NIIRS). In some scenarios, the two versions of the GIQE (versions 3.0 and 4.0) yield significantly different NIIRS predictions. We compare

Samuel T. Thurman; James R. Fienup

2008-01-01

95

Augmented reality image guidance for minimally invasive coronary artery bypass  

NASA Astrophysics Data System (ADS)

We propose a novel system for image guidance in totally endoscopic coronary artery bypass (TECAB). A key requirement is the availability of 2D-3D registration techniques that can deal with non-rigid motion and deformation. Image guidance for TECAB is mainly required before the mechanical stabilization of the heart, thus the most dominant source of non-rigid deformation is the motion of the beating heart. To augment the images in the endoscope of the da Vinci robot, we have to find the transformation from the coordinate system of the preoperative imaging modality to the system of the endoscopic cameras. In a first step we build a 4D motion model of the beating heart. Intraoperatively we can use the ECG or video processing to determine the phase of the cardiac cycle. We can then take the heart surface from the motion model and register it to the stereo-endoscopic images of the da Vinci robot using 2D-3D registration methods. We are investigating robust feature tracking and intensity-based methods for this purpose. Images of the vessels available in the preoperative coordinate system can then be transformed to the camera system and projected into the calibrated endoscope view using two video mixers with chroma keying. It is hoped that the augmented view can improve the efficiency of TECAB surgery and reduce the conversion rate to more conventional procedures.

Figl, Michael; Rueckert, Daniel; Hawkes, David; Casula, Roberto; Hu, Mingxing; Pedro, Ose; Zhang, Dong Ping; Penney, Graeme; Bello, Fernando; Edwards, Philip

2008-04-01

96

Quantitative metrics to evaluate image quality for computed radiographic images  

NASA Astrophysics Data System (ADS)

Traditional methods of evaluating a computed radiography (CR) imaging system's performance (e.g. the noise power spectrum (NPS), the modulation transfer function (MTF), the detective quantum efficiency (DQE) and contrast-detail analysis) were adapted in order to evaluate the feasibility of identifying a quantitative metric to evaluate image quality for digital radiographic images. The addition of simulated patient scattering media when acquiring the images to calculate these parameters altered their fundamental meaning. To avoid confusion with other research they were renamed the clinical noise power spectrum (NPSC), the clinical modulation transfer function (MTFC), the clinical detective quantum efficiency (DQEC) and the clinical contrast detail score (CDSC). These metrics were then compared to the subjective evaluation of radiographic images of an anthropomorphic phantom representing a one-year old pediatric patient. Computer algorithms were developed to implement the traditional mathematical procedures for calculating the system performance parameters. In order to easily compare these three metrics, the integral up to the system Nyquist frequency was used as the final image quality metric. These metrics are identified as the INPSC, the IMTFC and the IDQEC respectively. A computer algorithm was also developed, based on the results of the observer study, to determine the threshold contrast to noise ratio (CNRT) for objects of different sizes. This algorithm was then used to determine the CDSC by scoring images without the use of observers. The four image quality metrics identified in this study were evaluated to determine if they could distinguish between small changes in image acquisition parameters e.g., current-time product and peak-tube potential. All of the metrics were able to distinguish these small changes in at least one of the image acquisition parameters, but the ability to digitally manipulate the raw image data made the identification of a broad indicator of image quality not possible. The contrast-detail observer study revealed important information about how the noise content in an image affects the low-contrast detectability of different sized objects. Since the CNRT for each object size in the contrast-detail phantoms was almost independent of the exposure level, the minimum CNRT that would be necessary for an object of that size to be 'visible' in a clinical image was identified. Finally, in order to determine more refined CNRT values (due to possible observer biases from the physical construction of the contrast-detail phantoms available for this study) the design of new contrast detail phantoms is proposed.

Pitcher, Christopher D.

97

Subjective matters: from image quality to image psychology  

NASA Astrophysics Data System (ADS)

From the advent of digital imaging through several decades of studies, the human vision research community systematically focused on perceived image quality and digital artifacts due to resolution, compression, gamma, dynamic range, capture and reproduction noise, blur, etc., to help overcome existing technological challenges and shortcomings. Technological advances made digital images and digital multimedia nearly flawless in quality, and ubiquitous and pervasive in usage, provide us with the exciting but at the same time demanding possibility to turn to the domain of human experience including higher psychological functions, such as cognition, emotion, awareness, social interaction, consciousness and Self. In this paper we will outline the evolution of human centered multidisciplinary studies related to imaging and propose steps and potential foci of future research.

Fedorovskaya, Elena A.; De Ridder, Huib

2013-03-01

98

Health-related quality of life in patients with pulmonary arterial hypertension  

Microsoft Academic Search

BACKGROUND: Improved outcomes with expanding treatment options for patients with pulmonary arterial hypertension present the opportunity to consider additional end-points in approaching therapy, including factors that influence health-related quality of life. However, comparatively little is known about health-related quality of life and its determinants in patients with pulmonary arterial hypertension. METHODS: Health-related quality of life was evaluated in a cross

Darren B Taichman; Jennifer Shin; Laryssa Hud; Christine Archer-Chicko; Sandra Kaplan; Jeffery S Sager; Robert Gallop; Jason Christie; John Hansen-Flaschen; Harold Palevsky

2005-01-01

99

FFDM image quality assessment using computerized image texture analysis  

NASA Astrophysics Data System (ADS)

Quantitative measures of image quality (IQ) are routinely obtained during the evaluation of imaging systems. These measures, however, do not necessarily correlate with the IQ of the actual clinical images, which can also be affected by factors such as patient positioning. No quantitative method currently exists to evaluate clinical IQ. Therefore, we investigated the potential of using computerized image texture analysis to quantitatively assess IQ. Our hypothesis is that image texture features can be used to assess IQ as a measure of the image signal-to-noise ratio (SNR). To test feasibility, the "Rachel" anthropomorphic breast phantom (Model 169, Gammex RMI) was imaged with a Senographe 2000D FFDM system (GE Healthcare) using 220 unique exposure settings (target/filter, kVs, and mAs combinations). The mAs were varied from 10%-300% of that required for an average glandular dose (AGD) of 1.8 mGy. A 2.5cm2 retroareolar region of interest (ROI) was segmented from each image. The SNR was computed from the ROIs segmented from images linear with dose (i.e., raw images) after flat-field and off-set correction. Image texture features of skewness, coarseness, contrast, energy, homogeneity, and fractal dimension were computed from the Premium ViewTM postprocessed image ROIs. Multiple linear regression demonstrated a strong association between the computed image texture features and SNR (R2=0.92, p<=0.001). When including kV, target and filter as additional predictor variables, a stronger association with SNR was observed (R2=0.95, p<=0.001). The strong associations indicate that computerized image texture analysis can be used to measure image SNR and potentially aid in automating IQ assessment as a component of the clinical workflow. Further work is underway to validate our findings in larger clinical datasets.

Berger, Rachelle; Carton, Ann-Katherine; Maidment, Andrew D. A.; Kontos, Despina

2010-03-01

100

Color Doppler Imaging of an Ulnar Artery Perforator Forearm Flap for Resurfacing Finger Defects.  

PubMed

BACKGROUND: Fingertip defect reconstruction with various free perforator flaps has been widely reported. We recommend a technique of using color Doppler imaging to locate ulnar artery perforator. And we used a free mesioforearm flap based on ulnar artery perforator for the reconstruction of fingertip defect. PATIENTS AND METHODS: Since 2010, 7 fingertip defect cases have been repaired at our hospital using free mesioforearm flaps, based on the ulnar artery perforator. The free flap was designed according to Doppler detection. The flap contained perforator vessels and cutaneous nerves. The donor site was directly sutured or skin grafted. RESULTS: All 7 flaps survived with good quality and esthetic contours and grasp function of the hand was satisfactory. They were evaluated by 2-point discrimination, with 5 cases with neurorrhaphy of 6 to 8 mm and 2 cases without neurorrhaphy of 10 to 12 mm. CONCLUSIONS: Ultrasound is a suitable method for preoperatively locating the vascular pedicle. The free mesioforearm flap based on ulnar artery perforator is a good option to repair fingertip defect. PMID:23657043

Shen, Xiang-Qian; Shen, Hui; Xu, Ji-Hua; Wu, Shou-Cheng; Chen, Qiang; Chen, Bo

2013-05-01

101

Segmentation of arteries in MPRAGE images of the ventral medial prefrontal cortex  

PubMed Central

A method for removing arteries that appear bright with intensities similar to white matter in Magnetized Prepared Rapid Gradient Echo images of the ventral medial prefrontal cortex is described. The fast marching method is used to generate a curve within the artery. Then, the largest connected component is selected to segment the artery which is used to mask the image. The surface reconstructed from the masked image yielded cortical thickness maps similar to those generated by manually pruning the arteries from surfaces reconstructed from the original image. The method may be useful in masking vasculature in other cortical regions.

Penumetcha, N.; Jedynak, B.; Hosakere, M.; Ceyhan, E.; Botteron, K.N.; Ratnanather, J.T.

2010-01-01

102

Segmentation of arteries in MPRAGE images of the ventral medial prefrontal cortex.  

PubMed

A method for removing arteries that appear bright with intensities similar to white matter in Magnetized Prepared Rapid Gradient Echo images of the ventral medial prefrontal cortex is described. The Fast Marching method is used to generate a curve within the artery. Then, the largest connected component is selected to segment the artery which is used to mask the image. The surface reconstructed from the masked image yielded cortical thickness maps similar to those generated by manually pruning the arteries from surfaces reconstructed from the original image. The method may be useful in masking vasculature in other cortical regions. PMID:17964757

Penumetcha, N; Jedynak, B; Hosakere, M; Ceyhan, E; Botteron, K N; Ratnanather, J T

2007-10-26

103

Does resolution really increase image quality?  

NASA Astrophysics Data System (ADS)

A general trend in the CMOS image sensor market is for increasing resolution (by having a larger number of pixels) while keeping a small form factor by shrinking photosite size. This article discusses the impact of this trend on some of the main attributes of image quality. The first example is image sharpness. A smaller pitch theoretically allows a larger limiting resolution which is derived from the Modulation Transfer Function (MTF). But recent sensor technologies (1.75?m, and soon 1.45?m) with typical aperture f/2.8 are clearly reaching the size of the diffraction blur spot. A second example is the impact on pixel light sensitivity and image sensor noise. For photonic noise, the Signal-to-Noise-Ratio (SNR) is typically a decreasing function of the resolution. To evaluate whether shrinking pixel size could be beneficial to the image quality, the tradeoff between spatial resolution and light sensitivity is examined by comparing the image information capacity of sensors with varying pixel size. A theoretical analysis that takes into consideration measured and predictive models of pixel performance degradation and improvement associated with CMOS imager technology scaling, is presented. This analysis is completed by a benchmarking of recent commercial sensors with different pixel technologies.

Tisse, Christel-Loïc; Guichard, Frédéric; Cao, Frédéric

2008-03-01

104

Image quality assessment based on edge  

NASA Astrophysics Data System (ADS)

The research on image quality assessment (IQA) has been become a hot topic in most area concerning image processing. Seeking for the efficient IQA model with the neurophysiology support is naturally the goal people put the efforts to pursue. In this paper, we argue that comparing the edges position of reference and distorted image can well measure the image structural distortion and become an efficient IQA metric, while the edge is detected from the primitive structures of image convolving with LOG filters. The proposed metric is called NSER that has been designed following a simple logic based on the cosine distance of the primitive structures and two accessible improvements. Validation is taken by comparison of the well-known state-of-the-art IQA metrics: VIF, MS-SSIM, VSNR over the six IQA databases: LIVE, TID2008, MICT, IVC, A57, and CSIQ. Experiments show that NSER works stably across all the six databases and achieves the good performance.

Mou, Xuanqin; Zhang, Min; Xue, Wufeng; Zhang, Lei

2011-01-01

105

Results of Fingerprint Image Quality Experiments.  

National Technical Information Service (NTIS)

A series of experiments were conducted to determine the variation in the scores developed using a matching algorithm designated as the M-82 for mating fingerprints of different image quality that had been read by the Automatic Fingerprint Reader System (A...

R. T. Moore

1981-01-01

106

Naturalness and interestingness of test images for visual quality evaluation  

NASA Astrophysics Data System (ADS)

Balanced and representative test images are needed to study perceived visual quality in various application domains. This study investigates naturalness and interestingness as image quality attributes in the context of test images. Taking a top-down approach we aim to find the dimensions which constitute naturalness and interestingness in test images and the relationship between these high-level quality attributes. We compare existing collections of test images (e.g. Sony sRGB images, ISO 12640 images, Kodak images, Nokia images and test images developed within our group) in an experiment combining quality sorting and structured interviews. Based on the data gathered we analyze the viewer-supplied criteria for naturalness and interestingness across image types, quality levels and judges. This study advances our understanding of subjective image quality criteria and enables the validation of current test images, furthering their development.

Halonen, Raisa; Westman, Stina; Oittinen, Pirkko

2011-01-01

107

Automatic determination of the artery vein ratio in retinal images  

NASA Astrophysics Data System (ADS)

A lower ratio between the width of the arteries and veins (Arteriolar-to-Venular diameter Ratio, AVR) on the retina, is well established to be predictive of stroke and other cardiovascular events in adults, as well as an increased risk of retinopathy of prematurity in premature infants. This work presents an automatic method that detects the location of the optic disc, determines the appropriate region of interest (ROI), classifies the vessels in the ROI into arteries and veins, measures their widths and calculates the AVR. After vessel segmentation and vessel width determination the optic disc is located and the system eliminates all vessels outside the AVR measurement ROI. The remaining vessels are thinned, vessel crossing and bifurcation points are removed leaving a set of vessel segments containing centerline pixels. Features are extracted from each centerline pixel that are used to assign them a soft label indicating the likelihood the pixel is part of a vein. As all centerline pixels in a connected segment should be the same type, the median soft label is assigned to each centerline pixel in the segment. Next artery vein pairs are matched using an iterative algorithm and the widths of the vessels is used to calculate the AVR. We train and test the algorithm using a set of 25 high resolution digital color fundus photographs a reference standard that indicates for the major vessels in the images whether they are an artery or a vein. We compared the AVR values produced by our system with those determined using a computer assisted method in 15 high resolution digital color fundus photographs and obtained a correlation coefficient of 0.881.

Niemeijer, Meindert; van Ginneken, Bram; Abràmoff, Michael D.

2010-03-01

108

Quantification issues in arterial spin labeling perfusion magnetic resonance imaging.  

PubMed

Arterial spin labeling (ASL) perfusion magnetic resonance imaging has gained wide acceptance for its value in clinical and neuroscience applications during recent years. Its capability for noninvasive and absolute perfusion quantification is a key characteristic that makes ASL attractive for many clinical applications. In the present review, we discuss the main parameters or factors that affect the reliability and accuracy of ASL perfusion measurements. Our secondary goal was to outline potential solutions that may improve the reliability and accuracy of ASL in clinical settings. It was found that, through theoretical analyses, flow quantification is most sensitive to tagging efficiency and estimation of the equilibrium magnetization of blood signal (M(0b)). Variations of blood T1 have a greater effect on perfusion quantification than variations of tissue T1. Arterial transit time becomes an influential factor when it is longer than the postlabeling delay time. The T2's of blood and tissue impose minimal effects on perfusion calculation at field strengths equal to or lower than 3.0 T. Subsequently, we proposed various approaches for in vivo estimation or calibration of the above parameters, such as the use of phase-contrast magnetic resonance imaging for calibration of the labeling efficiency as well as the use of inversion recovery TrueFISP (true fast imaging with steady-state precession) sequence for blood T1 mapping. We also list representative clinical cases in which implicit assumptions for ASL perfusion quantification may be violated, such as the venous outflow effect in children with sickle cell disease. Finally, an optimal imaging protocol including in vivo measurements of several critical parameters was recommended for clinical ASL studies. PMID:21613872

Wu, Wen-Chau; St Lawrence, Keith S; Licht, Daniel J; Wang, Danny J J

2010-04-01

109

Spatial orientation of cross-sectional images of coronary arteries: point of view in intracoronary imaging  

PubMed Central

Background In studies where cross-sectional images of coronary arteries obtained with different imaging modalities are compared, the importance of correct co-localization and matching of images along the coronary artery longitudinal axis is obvious. However, it appears neglected that correct spatial orientation of the cross-sectional plane may not be obtainable just by rotating the images to ensure co-localization of identifiable landmarks such as sidebranches. A cross-section has two sides, one facing proximally and the other distally, and pairs of images reconstructed corresponding to these opposite points of view are mirror images of each other and not superimposable. This may be difficult if not impossible to recognize and unrecognized it will give rise to flawed results in the development and validation of imaging technologies aimed at plaque characterization (tissue mapping). We determined the imagined point of view for three commercially available intracoronary imaging systems used by invasive cardiologists and illustrate its importance in imaging modality validation. Methods and Results We made an asymmetric phantom and investigated it with two different intravascular ultrasound (IVUS) systems and one optical coherence tomography (OCT) system. The asymmetry of the phantom allowed determination of the spatial orientation of the cross-sectional images. On all tested systems, an observer should imagine herself/himself standing proximal to the cross-section when looking at the intravascular images. Conclusions The tested intracoronary imaging modalities displayed cross-sectional images with a spatial orientation corresponding to a proximal point of view. Knowledge of the spatial orientation is mandatory when comparing and validating different imaging modalities aimed at plaque characterization.

2012-01-01

110

Quality evaluation for compressed medical images: Diagnostic Accuracy  

Microsoft Academic Search

We examined in the previous chapter several common computable measures of image quality, as well as subjective quality ratings. While these quality measures are useful in many ways, for medical images one wishes a quality measure to take proper account of the diagnostic purpose of the image. The ROC methodology discussed in the previous chapter is one approach to this.

Pamela Cosman; Robert Gray; Richard Olshen

111

Evaluation of Stereoscopic Images: Beyond 2D Quality  

Microsoft Academic Search

Perceived image quality is a standard evaluation concept for 2D imaging systems. When applied to stereoscopic 3D imaging systems, however, it does not incorporate the added value of stereoscopic depth. Higher level evaluation concepts (natural- ness and viewing experience) are proposed that are sensitive to both image quality and stereoscopic depth. A 3D Quality Model is constructed in which such

Marc Lambooij; Wijnand IJsselsteijn; Don G. Bouwhuis; Ingrid Heynderickx

2011-01-01

112

Color image quality prediction models for color hard copy  

Microsoft Academic Search

Color image quality prediction models for two typical documents used as input for color copying machines have been developed to relate subjective image quality ratings to physical image quality metrics using stepwise multiple regression analysis. The typical documents consist of colored map and portrait images. The models were consistent with technical knowledge and achieved high correlation between predicted ratings and

Toshihiko Inagaki; T. Miyagi; S. Sasahara; T. Matsuzaki; T. Gotoh

1994-01-01

113

No-reference image quality metric based on image classification  

NASA Astrophysics Data System (ADS)

In this article, we present a new no-reference (NR) objective image quality metric based on image classification. We also propose a new blocking metric and a new blur metric. Both metrics are NR metrics since they need no information from the original image. The blocking metric was computed by considering that the visibility of horizontal and vertical blocking artifacts can change depending on background luminance levels. When computing the blur metric, we took into account the fact that blurring in edge regions is generally more sensitive to the human visual system. Since different compression standards usually produce different compression artifacts, we classified images into two classes using the proposed blocking metric: one class that contained blocking artifacts and another class that did not contain blocking artifacts. Then, we used different quality metrics based on the classification results. Experimental results show that each metric correlated well with subjective ratings, and the proposed NR image quality metric consistently provided good performance with various types of content and distortions.

Choi, Hyunsoo; Lee, Chulhee

2011-12-01

114

Physical measures of image quality in mammography  

NASA Astrophysics Data System (ADS)

A recently introduced method for quantitative analysis of images of the American College of Radiology (ACR) mammography accreditation phantom has been extended to include signal- to-noise-ratio (SNR) measurements, and has been applied to survey the image quality of 54 mammography machines from 17 hospitals. Participants sent us phantom images to be evaluated for each mammography machine at their hospital. Each phantom was loaned to us for obtaining images of the wax insert plate on a reference machine at our institution. The images were digitized and analyzed to yield indices that quantified the image quality of the machines precisely. We have developed methods for normalizing for the variation of the individual speck sizes between different ACR phantoms, for the variation of the speck sizes within a microcalcification group, and for variations in overall speeds of the mammography systems. In terms of the microcalcification SNR, the variability of the x-ray machines was 40.5% when no allowance was made for phantom or mAs variations. This dropped to 17.1% when phantom variability was accounted for, and to 12.7% when mAs variability was also allowed for. Our work shows the feasibility of practical, low-cost, objective and accurate evaluations, as a useful adjunct to the present ACR method.

Chakraborty, Dev P.

1996-04-01

115

Image guidance for robotic minimally invasive coronary artery bypass.  

PubMed

A novel system for image guidance in totally endoscopic coronary artery bypass (TECAB) is presented. Key requirement is the availability of 2D-3D registration techniques that can deal with non-rigid motion and deformation. Image guidance for TECAB is mainly required before the mechanical stabilisation of the heart, when the most dominant source of misregistration is the deformation and non-rigid motion of the heart. To augment the images in the endoscope of the da Vinci robot, we have to find the transformation from the coordinate system of the preoperative imaging modality to the system of the endoscopic cameras. In a first step we build a 4D motion model of the beating heart. Intraoperatively we can use the ECG or video processing to determine the phase of the cardiac cycle, as well as the heart and respiratory frequencies. We then take the heart surface from the motion model and register it to the stereo endoscopic images of the da Vinci robot resp. of a validation system using photo-consistency. To take advantage of the fact that there is a whole image sequence available for registration, we use the different phases together to get the registration. We found the similarity function to be much smoother when using more phases. This also showed promising behaviour in convergence tests. Images of the vessels available in the preoperative coordinate system can then be transformed to the camera system and projected into the calibrated endoscope view using two video mixers with chroma keying. It is hoped that the augmented view can improve the efficiency of TECAB surgery and reduce the conversion rate to more conventional procedures. PMID:19773147

Figl, Michael; Rueckert, Daniel; Hawkes, David; Casula, Roberto; Hu, Mingxing; Pedro, Ose; Zhang, Dong Ping; Penney, Graeme; Bello, Fernando; Edwards, Philip

2009-09-20

116

A non-invasive study of alterations of the carotid artery with age using ultrasound images.  

PubMed

A region-based method for measurement of arterial diameter to find out the elasticity of the vessel is proposed in this paper. Arterial segments are studied by using images obtained through ultrasound scanning in B-mode. Pulsatile changes of the common carotid artery during diastole and systole are computed. To achieve this, thinned segmentation is done by suitably adjusting the contrast of the image. The diameter changes of the artery wall from the centre of artery are calculated. Fifty-three normal subjects with age group 20-40 years are taken for measurement. Measured diameter is plotted as a graph and pulsatile changes of the artery are obtained. Since no atherosclerotic lesions are detected in the studied subjects, it is suggested that the common carotid artery is a highly compliant artery with a strong alteration of viscoelastic properties with age. PMID:16960743

Balasundaram, Jayanthi K; Banu, R S D Wahida

2006-08-08

117

Fusion imaging: Combined visualization of 3D reconstructed coronary artery tree and 3D myocardial scintigraphic image in coronary artery disease  

Microsoft Academic Search

Background: In patients with coronary artery disease, coronary angiography is performed for assessment of epicardial coronary artery stenoses. In addition, myocardial scintigraphy is commonly used to evaluate regional myocardial perfusion. These two-dimensional (2D) imaging modalities are typically reviewed through a subjective, visual observation by a physician. Even though on the analysis of 2D display scintigraphic myocardial perfusion segments are arbitrarily

Thomas H. Schindler; Nobuhisa Magosaki; Michael Jeserich; Uwe Oser; Thomas Krause; Richard Fischer; Ernst Moser; Egbert Nitzsche; Manfred Zehender; Hanjörg Just; Ulrich Solzbach

1999-01-01

118

Automatic Active Contour-Based Segmentation and Classification of Carotid Artery Ultrasound Images.  

PubMed

In this paper, we present automatic image segmentation and classification technique for carotid artery ultrasound images based on active contour approach. For early detection of the plaque in carotid artery to avoid serious brain strokes, active contour-based techniques have been applied successfully to segment out the carotid artery ultrasound images. Further, ultrasound images might be affected due to rotation, scaling, or translational factors during acquisition process. Keeping in view these facts, image alignment is used as a preprocessing step to align the carotid artery ultrasound images. In our experimental study, we exploit intima-media thickness (IMT) measurement to detect the presence of plaque in the artery. Support vector machine (SVM) classification is employed using these segmented images to distinguish the normal and diseased artery images. IMT measurement is used to form the feature vector. Our proposed approach segments the carotid artery images in an automatic way and further classifies them using SVM. Experimental results show the learning capability of SVM classifier and validate the usefulness of our proposed approach. Further, the proposed approach needs minimum interaction from a user for an early detection of plaque in carotid artery. Regarding the usefulness of the proposed approach in healthcare, it can be effectively used in remote areas as a preliminary clinical step even in the absence of highly skilled radiologists. PMID:23417308

Chaudhry, Asmatullah; Hassan, Mehdi; Khan, Asifullah; Kim, Jin Young

2013-02-16

119

Quality of Life Improvement after Robotically Assisted Coronary Artery Bypass Grafting  

Microsoft Academic Search

Objectives: Coronary artery bypass grafting (CABG) is associated with long rehabilitation periods and slow quality of life (QOL) improvement. Totally endoscopic coronary artery bypass grafting (TECAB) can be performed using robotic technology and remote access perfusion. The aim of this study was to evaluate whether TECAB leads to accelerated QOL improvement as compared to standard CABG. Methods: We included 120

Nikolaos Bonaros; Thomas Schachner; Dominik Wiedemann; Armin Oehlinger; Elisabeth Ruetzler; Gudrun Feuchtner; Christian Kolbitsch; Corinna Velik-Salchner; Guy Friedrich; Othmar Pachinger; Guenther Laufer; Johannes Bonatti

2009-01-01

120

Rapid and complete coronary arterial tree visualization with magnetic resonance imaging: feasibility and diagnostic performance  

Microsoft Academic Search

Aims Current imaging of the coronary arteries with magnetic resonance coronary angiography (MRCA) is restricted to limited coverage of the coronary arterial tree and requires complex planning. We present and evaluate a rapid, single-scan MRCA approach with complete coverage of the coronary arterial tree. Methods and results Fifty-five consecutive patients with suspected coronary artery disease underwent free-breathing, navigator-gated MRCA using

Cosima Jahnke; Ingo Paetsch; Kay Nehrke; Bernhard Schnackenburg; Rolf Gebker; Eckart Fleck; Eike Nagel

2005-01-01

121

Synchrotron radiation dichromographic imaging of the extra- and intracranial arterial circulations and choroid plexus  

NASA Astrophysics Data System (ADS)

This communication proposes the use of synchrotron radiation based k-edge dichromographic imaging for the simultaneous study of the extracranial and intracranial arterial circulations following a single peripheral intravenous injection of a contrast agent. This approach can provide images of the vertebral arteries, the common, external and internal carotid arteries, as well as the intracranial arteries, during a single scanning procedure, lasting only a few seconds, requiring an X-ray exposure on the order of about 30mGy/image. The method has specific advantages for the evaluation of the perfusion of the choroid plexus.

Rubenstein, E.

2002-05-01

122

Image quality evaluation of light field photography  

NASA Astrophysics Data System (ADS)

Light field photography captures 4D radiance information of a scene. Digital refocusing and digital correction of aberrations could be done after the photograph is taken. However, capturing 4D light field is costly and tradeoffs between different image quality metrics should be made and evaluated. This paper explores the effects of light field photography on image quality by quantitatively evaluating some basic criteria for an imaging system. A simulation approach was first developed by ray-tracing a designed light field camera. A standard testing chart followed by ISO 12233 was provided as the input scene. A sequence of light field raw images were acquired and processed by light field rendering methods afterwards. Through-focus visual resolution and MTF were calculated and analyzed. As a comparison, the same tests were taken for the same main lens system as the results of conventional photography. An experimental light field system was built up and its performance was tested. This work helps better understanding the pros and cons of light field photography in contrast with conventional imaging methods and perceiving the way to optimize the joint digital-optical design of the system.

Fu, Qiang; Zhou, Zhiliang; Yuan, Yan; Xiangli, Bin

2011-01-01

123

Cross-Sectional Imaging in a Case of Adventitial Cystic Disease of the Popliteal Artery  

SciTech Connect

Adventitial cystic disease of the popliteal artery is an unusual condition of uncertain etiology, in which a mucin-containing cyst forms in the wall of the artery and produces lower extremity claudication, typically in young and middle-aged men. A diagnosis of adventitial cystic disease of the popliteal artery was made preoperatively in a 47-year-old man by means of several imaging modalities, including angiography, magnetic resonance imaging, and ultrasound. The pathological findings confirmed the suggested diagnosis.

Ricci, Paolo; Panzetti, Claudio; Mastantuono, Marco; Bassetti, Erica [Department of Radiology, 2nd-3rd Chair, University of Rome 'La Sapienza', viale Regina Elena 324, I-00161 Rome (Italy); Iascone, Clemente; Ragonesi, Barbara [Department of Surgery, University of Rome 'La Sapienza', viale Regina Elena 324, I-00161 Rome (Italy); Bernucci, Paola; Gallo, Pietro [Department of Experimental Medicine and Pathology, University of Rome 'La Sapienza', viale Regina Elena 324, I-00161 Rome (Italy); Rossi, Plinio [Department of Radiology, 2nd-3rd Chair, University of Rome 'La Sapienza', viale Regina Elena 324, I-00161 Rome (Italy)

1999-01-15

124

Image-Based Computational Fluid Dynamics Modeling in Realistic Arterial Geometries  

Microsoft Academic Search

Local hemodynamics are an important factor in atherosclerosis, from the development of early lesions, to the assessment of stroke risk, to determining the ultimate fate of a mature plaque. Until recently, our understanding of arterial fluid dynamics and their relationship to atherosclerosis was limited by the use of idealized or averaged artery models. Recent advances in medical imaging, computerized image

David A. Steinman

2002-01-01

125

Accuracy of Computational Hemodynamics in Complex Arterial Geometries Reconstructed from Magnetic Resonance Imaging  

Microsoft Academic Search

Purpose: Combining computational blood flow modeling with three-dimensional medical imaging provides a new approach for studying links between hemodynamic factors and arterial disease. Although this provides patient-specific hemodynamic information, it is subject to several potential errors. This study quantifies some of these errors and identifies optimal reconstruction methodologies. Methods: A carotid artery bifurcation phantom of known geometry was imaged using

J. A. Moore; D. A. Steinman; D. W. Holdsworth; C. R. Ethier

1999-01-01

126

Imaging Investigation of a Giant Splenic Artery Aneurysm  

Microsoft Academic Search

Splenic artery aneurysms represent approximately 60% of visceral arterial aneurysms. Their incidence at autopsy is 0.02 — 2 % in all age groups and rises to 10.4% above the age of 60. Although splenic artery aneurysms are the most common visceral aneurysms, giant splenic artery aneurysms >10 cm in diameter have rarely been reported. A recent review of the literature

Marianna Vlychou; Constantinos Kokkinis; Sotiria Stathopoulou; Constantinos Tsilikas; Olga Lazoura; Adamantia Petinelli; Paraskevi Papadaki; Ioannis Fezoulidis

2008-01-01

127

Optical coherence tomography and hyperspectral imaging of vascular recovery in a model of peripheral arterial disease  

NASA Astrophysics Data System (ADS)

Peripheral arterial disease (PAD) leads to an increased risk of myocardial infarction and stroke, increased mortality, and reduced quality of life. The mouse hind limb ischemia (HLI) model is the most commonly used system for studying the mechanisms of collateral vessel formation and for testing new PAD therapies, but there is a lack of techniques for acquiring physiologically-relevant, quantitative data intravitally in this model. In this work, non-invasive, quantitative optical imaging techniques were applied to the mouse HLI model over a time course. Optical coherence tomography (OCT) imaged changes in blood flow (Doppler OCT) and microvessel morphology (speckle variance OCT) through the skin of haired mice with high resolution. Hyperspectral imaging was also used to quantify blood oxygenation. In ischemic limbs, blood oxygenation in the footpad was substantially reduced after induction of ischemia followed by complete recovery by three weeks, consistent with standard measures. Three dimensional images of the vasculature distal to vessel occlusion acquired with speckle variance OCT revealed changes in OCT flow signal and vessel morphology. Taken together, OCT and hyperspectral imaging enable intravital acquisition of both functional and morphological data which fill critical gaps in understanding structure-function relationships that contribute to recovery in the mouse HLI model. Therefore, these optical imaging methods hold promise as tools for studying the mechanisms of vascular recovery and evaluating novel therapeutic treatments in preclinical studies.

Poole, Kristin M.; Sit, Wesley W.; Tucker-Schwartz, Jason M.; Duvall, Craig L.; Skala, Melissa C.

128

Assessment of artery dilation by using image registration based on spatial features  

NASA Astrophysics Data System (ADS)

The use of affine image registration based on normalized mutual information (NMI) has recently been proposed by Frangi et al. as an automatic method for assessing brachial artery flow mediated dilation (FMD) for the characterization of endothelial function. Even though this method solves many problems of previous approaches, there are still some situations that can lead to misregistration between frames, such as the presence of adjacent vessels due to probe movement, muscle fibres or poor image quality. Despite its widespread use as a registration metric and its promising results, MI is not the panacea and can occasionally fail. Previous work has attempted to include spatial information into the image similarity metric. Among these methods the direct estimation of ?-MI through Minimum Euclidean Graphs allows to include spatial information and it seems suitable to tackle the registration problem in vascular images, where well oriented structures corresponding to vessel walls and muscle fibres are present. The purpose of this work is twofold. Firstly, we aim to evaluate the effect of including spatial information in the performance of the method suggested by Frangi et al. by using ?-MI of spatial features as similarity metric. Secondly, the application of image registration to long image sequences in which both rigid motion and deformation are present will be used as a benchmark to prove the value of ?-MI as a similarity metric, and will also allow us to make a comparative study with respect to NMI.

Oubel, Estanislao; Neemuchwala, Huzefa; Hero, Alfred; Boisrobert, Loic; Laclaustra, Martin; Frangi, Alejandro F.

2005-04-01

129

Image quality assessment and human visual system  

NASA Astrophysics Data System (ADS)

This paper summaries the state-of-the-art of image quality assessment (IQA) and human visual system (HVS). IQA provides an objective index or real value to measure the quality of the specified image. Since human beings are the ultimate receivers of visual information in practical applications, the most reliable IQA is to build a computational model to mimic the HVS. According to the properties and cognitive mechanism of the HVS, the available HVS-based IQA methods can be divided into two categories, i.e., bionics methods and engineering methods. This paper briefly introduces the basic theories and development histories of the above two kinds of HVS-based IQA methods. Finally, some promising research issues are pointed out in the end of the paper.

Gao, Xinbo; Lu, Wen; Tao, Dacheng; Li, Xuelong

2010-07-01

130

Objective Image Quality Metrics: Applications for Partially Compensated Images of Space Objects.  

National Technical Information Service (NTIS)

Digital image reconstruction tasks currently require human intervention for a subjective evaluation of image quality. A method for unsupervised measurement of digital image quality is desired. This research investigated various parameters (metrics) that c...

D. J. Lee

1993-01-01

131

Optimization of background suppression for arterial spin labeling perfusion imaging  

PubMed Central

Object To present an algorithm for optimization of background suppression pulse timing for arterial spin labeling (ASL) perfusion imaging. Materials and methods An algorithm for optimization of background suppression pulse timing is proposed. Numerical optimization of timing of the background suppression pulses is investigated in both constrained and unconstrained ASL sequences. The performance of the parameters from the algorithm is evaluated in phantom and also in vivo in five human subjects. Results The background signal is suppressed to less than 1% across a broad range of T1s with a modest number of inversion pulses using the timings acquired from the numerical optimization algorithm proposed in this study. The performance of the parameters from the algorithm is also confirmed in vivo. Conclusion Successful background suppression over a broad range of tissues is achievable. Values for optimal pulse timing in both pulsed and continuous ASL studies are reported to facilitate sequence design with different labeling parameters.

Maleki, Nasim; Dai, Weiying; Alsop, David C.

2013-01-01

132

Ultrasound image quality assessment: a framework for evaluation of clinical image quality  

NASA Astrophysics Data System (ADS)

Improvement of ultrasound images should be guided by their diagnostic value. Evaluation of clinical image quality is generally performed subjectively, because objective criteria have not yet been fully developed and accepted for the evaluation of clinical image quality. Based on recommendation 500 from the International Telecommunication Union - Radiocommunication (ITU-R) for such subjective quality assessment, this work presents equipment and a methodology for clinical image quality evaluation for guiding the development of new and improved imaging. The system is based on a BK-Medical 2202 ProFocus scanner equipped with a UA2227 research interface, connected to a PC through X64-CL Express camera link. Data acquisition features subject data recording, loading/saving of exact scanner settings (for later experiment reproducibility), free access to all system parameters for beamformation and is applicable for clinical use. The free access to all system parameters enables the ability to capture standardized images as found in the clinic and experimental data from new processing or beamformation methods. The length of the data sequences is only restricted by the memory of the external PC. Data may be captured interleaved, switching between multiple setups, to maintain identical transducer, scanner, region of interest and recording time on both the experimental- and standardized images. Data storage is approximately 15.1 seconds pr. 3 sec sequence including complete scanner settings and patient information, which is fast enough to get sufficient number of scans under realistic operating conditions, so that statistical evaluation is valid and reliable.

Hemmsen, Martin Christian; Petersen, Mads Møller; Nikolov, Svetoslav Ivanov; Nielsen, Michael Backmann; Jensen, Jørgen Arendt

2010-03-01

133

Image quality analysis and low dose dental CT  

Microsoft Academic Search

Due to the rapid increase of the number of computed tomography examinations for dental purposes we are facing the problem of dose reduction without loss of image quality. The purpose of this work is to investigate the image quality variation in relation to scan parameters that affect dose. Subjective evaluations and quantitative measurements of image quality indices were performed on

S. D. Bianchi; O. Rampado; L. Luberto; A. F. Genovesio; C. C. Bianchi; R. Ropolo

2005-01-01

134

Statistical evaluation of no-reference image visual quality metrics  

Microsoft Academic Search

A task of no-reference visual quality metric verification is considered. A test set that contains 500 JPEG format images having different distortions is created. The results of experiments carried out by 316 volunteer observers to evaluate visual quality of images are presented. The experiments allowed obtaining mean opinion scores (MOS) based on averaging the evaluations. Several non-reference image visual quality

Nikolay Ponomarenko; Oleg Eremeev; Vladimir Lukin; Karen Egiazarian

2010-01-01

135

A robust eye localization method for low quality face images  

Microsoft Academic Search

Eye localization is an important part in face recognition system, because its precision closely affects the performance of face recognition. Although various methods have already achieved high precision on the face images with high quality, their precision will drop on low quality images. In this paper, we propose a robust eye localization method for low quality face images to improve

Dong Yi; Zhen Lei; Stan Z. Li

2011-01-01

136

Quality evaluation model of coded stereoscopic color image  

NASA Astrophysics Data System (ADS)

To consider the quality of service for stereoscopic image through the network, it is necessary to develop a quality evaluation method for coded stereoscopic image. We propose a quality evaluation model of the coded stereoscopic color image. This evaluation model considers not only the distortions of the edge region and smooth region but also the texture features of the left image. In addition, this model takes into account the disparity information between the left and right images. Instead of the disparity compensated coded image, we employ the JPEG coded image for the subjective assessment test. As the results, the evaluation model is useful for coded stereoscopic image.

Horita, Yuukou; Kawai, Yoshinao; Minami, Yohko; Murai, Tadakuni

2000-05-01

137

Wavelet-based image fusion and quality assessment  

NASA Astrophysics Data System (ADS)

Recent developments in satellite and sensor technologies have provided high-resolution satellite images. Image fusion techniques can improve the quality, and increase the application of these data. This paper addresses two issues in image fusion (a) the image fusion method and (b) corresponding quality assessment. Firstly, a multi-band wavelet-based image fusion method is presented, which is a further development of the two-band wavelet transformation. This fusion method is then applied to a case study to demonstrate its performance in image fusion. Secondly, quality assessment for fused images is discussed. The objectives of image fusion include enhancing the visibility of the image and improving the spatial resolution and the spectral information of the original images. For assessing quality of an image after fusion, we define the aspects to be assessed initially. These include, for instance, spatial and spectral resolution, quantity of information, visibility, contrast, or details of features of interest. Quality assessment is application dependant; different applications may require different aspects of image quality. Based on this analysis, a set of qualities is classified and analyzed. These sets of qualities include (a) average grey value, for representing intensity of an image, (b) standard deviation, information entropy, profile intensity curve for assessing details of fused images, and (c) bias and correlation coefficient for measuring distortion between the original image and fused image in terms of spectral information.

Shi, Wenzhong; Zhu, Changqing; Tian, Yan; Nichol, Janet

2005-03-01

138

Second harmonic imaging improves sensitivity of dobutamine stress echocardiography for the diagnosis of coronary artery disease  

Microsoft Academic Search

Objective Our purpose was to assess the value of second harmonic imaging compared with fundamental imaging for the diagnosis of coronary artery disease during dobutamine stress echocardiography. Patients and Methods Sixty-four patients underwent dobutamine stress echocardiography with both fundamental imaging and second harmonic imaging. Coronary angiography was performed within 3 months. Ischemia was defined as new or worsening wall motion

Fabiola B. Sozzi; Don Poldermans; Jeroen J. Bax; Eric Boersma; Wim B. Vletter; Abdou Elhendy; Alberico Borghetti; Jos R. T. C. Roelandt

2001-01-01

139

Diagnostic and prognostic value of non-invasive imaging in known or suspected coronary artery disease  

Microsoft Academic Search

The role of non-invasive imaging techniques in the evaluation of patients with suspected or known coronary artery disease (CAD) has increased exponentially over the past decade. The traditionally available imaging modalities, including nuclear imaging, stress echocardiography and magnetic resonance imaging (MRI), have relied on detection of CAD by visualisation of its functional consequences (i.e. ischaemia). However, extensive research is being

J. D. Schuijf; D. Poldermans; L. J. Shaw; J. W. Jukema; H. J. Lamb; A. de Roos; W. Wijns; E. E. van der Wall; J. J. Bax

2006-01-01

140

Contrast imaging and gene delivery through the combined use of novel cationic liposomal microbubbles and ultrasound in rat carotid arteries  

PubMed Central

Introduction Lipid-coated cationic microbubbles represent a new class of agents with both diagnostic and therapeutic applications. The main goal of this study was to evaluate the efficiency of gene transfer through the combined use of microbubbles and ultrasound in rat carotid arteries. Furthermore, we assessed whether the cationic liposomal microbubbles could allow long-term enhanced imaging, comparing with SonoVue®. Material and methods Normal rat carotid arteries were imaged after intravenous bolus injections of 0.5 ml/kg of two contrast agents (SonoVue® and the cationic liposomal microbubbles). Forty Sprague-Dawley rats were divided into 5 groups according to ultrasound parameters and were treated with or without microbubbles. All rats were sacrificed after being transfected for 2 days. The level of protein expression was determined by western blot analysis. Results The enhancing time of self-made microbubbles was much longer than that of SonoVue® in rat carotid arteries (p < 0.05). The results of the western blot analysis revealed that the expression of SR-BI DNA in the carotid artery was highest in the SR-BI + US/CLM group (p < 0.05). Conclusions These results suggest that the novel cationic liposomal microbubbles enhance image quality over a longer period than does SonoVue®. Additionally, the combination of ultrasound and this new type of microbubble can act synergistically to increase SR-BI DNA transfection.

Liu, Fang; Huang, Yunxia; Guo, Wei; Rui, Mengjie; Xu, Yuhong; Hu, Bing

2013-01-01

141

A relationship between slide quality and image quality in whole slide imaging (WSI).  

PubMed

This study examined the effect of tissue section thickness and consistency--parameters outside the direct control of the imaging devices themselves--on WSI capture speed and image quality. Preliminary data indicates that thinner, more consistent tissue sectioning (such as those produced by automated tissue sectioning robots) results in significantly faster WSI capture times and better image quality. A variety of tissue types (including human breast, mouse embryo, mouse brain, etc.) were sectioned using an (AS-200) Automated Tissue Sectioning System (Kurabo Industries, Osaka Japan) at thicknesses from 2 - 9 microm (at one microm intervals) and stained with H&E by a standard method. The resulting slides were imaged with 5 different WSI devices (ScanScope CS, Aperio, CA; iScan, BioImagene, CA; DX40, DMetrix, AZ; NanoZoomer, Hamamatsu Photonics K.K., Japan; Mirax Scan, Carl Zeiss Inc., Germany) with sampling periods of 0.43 - 0.69 microm/pixel. Slides with different tissue thicknesses were compared for image quality, appropriate number of focus points, and overall scanning speed. Thinner sections (i.e. 3 microm sections versus 7 microm) required significantly fewer focus points and had significantly lower (10-15%) capture times. Improvement was seen with all devices and tissues tested. Furthermore, a panel of experienced pathologist judged image quality to be significantly better (for example, with better apparent resolution of nucleoli) with the thinner sections. Automated tissue sectioning is a very new technology; however, the AS-200 seems to be able to produce thinner, more consistent, flatter sections than manual methods at reasonably high throughput. The resulting tissue sections seem to be easier for a WSI system's focusing systems to deal with (compared to manually cut slides). Teaming an automated tissue-sectioning device with a WSI device shows promise in producing faster WSI throughput with better image quality. PMID:18673500

Yagi, Yukako; Gilbertson, John R

2008-07-15

142

Neurological Outcome and Quality of Life after Stroke due to Vertebral Artery Dissection  

Microsoft Academic Search

Background: Vertebral artery dissection is a well-recognized cause of posterior circulation stroke for which there is relatively little information on long-term outcomes. Quality of life (QOL) is an important patient-centred outcome measure. Methods: Stroke due to vertebral artery dissection was conservatively defined by neuroimaging documentation. Thirty sequential cases were identified based on a retrospective database and chart review with prospective

Diana Czechowsky; Michael D. Hill

2002-01-01

143

Association between sleep quality and arterial blood pressure among Chinese nonagenarians/centenarians  

PubMed Central

Summary Background There is association between sleep quality and arterial blood pressure, but it is still unclear if the association also exists in the very elderly. We examined the individual association between sleep quality and arterial blood pressure among the very elderly. Material/Methods The present study analyzed data from a survey that was conducted on all residents aged 90 years or older in a district with 2,311,709 inhabitants in 2005. Sleep quality was measured using The Pittsburgh Sleep Quality Index (PSQI). Results The subjects included in the statistical analysis were 216 men and 444 women. There were no significant differences in sleep quality scores, sleep latency, and sleep efficiency percentage and prevalence of poor sleep quality between subjects with and without hypertension. None of the differences in systolic blood pressure, diastolic blood pressure, and prevalence of hypertension, systolic hypertension and diastolic hypertension among subjects with well, fairly and poor sleep quality were significant. Multiple logistic regressions showed that unadjusted and adjusted Odds Ratio (ORs) of poor sleep quality for increased risk for hypertension were significant. Conclusions Among very elderly subjects, there was no association between sleep quality and arterial blood pressure.

Ji-Rong, Yue; Hui, Wang; Chang-Quan, Huang; Bi-Rong, Dong

2012-01-01

144

Gadolinium-Enhanced MR Imaging in the Evaluation of Uterine Fibroids Treated with Uterine Artery Embolization  

Microsoft Academic Search

OBJECTIVE . The purpose of this study was to determine whether tumor volume reduc- tion can be predicted by the infarction rate of uterine fibroids as seen on gadolinium-enhanced MR images obtained immediately after uterine artery embolization. MATERIALS AND METHODS . In our study, 36 women with symptomatic uterine fi- broids successfully underwent uterine artery embolization. Unenhanced and enhanced MR

Tetsuya Katsumori; Kazuhiro Nakajima; Mitsukuni Tokuhiro

145

Image-Based Computational Fluid Dynamics Modeling in Realistic Arterial Geometries  

Microsoft Academic Search

Local hemodynamics are an important factor in ath- erosclerosis, from the development of early lesions, to the as- sessment of stroke risk, to determining the ultimate fate of a mature plaque. Until recently, our understanding of arterial fluid dynamics and their relationship to atherosclerosis was limited by the use of idealized or averaged artery models. Recent advances in medical imaging,

DAVID A. STEINMAN

2002-01-01

146

Image quality assessment using the singular value decomposition theorem  

NASA Astrophysics Data System (ADS)

In objective image quality metrics, one of the most important factors is the correlation of their results with the perceived quality measurements. In this paper, a new method is presented based on comparing between the structural properties of the two compared images. Based on the mathematical concept of the singular value decomposition (SVD) theorem, each matrix can be factorized to the products of three matrices, one of them related to the luminance value while the two others show the structural content information of the image. A new method to quantify the quality of images is proposed based on the projected coefficients and the left singular vector matrix of the disturbed image based on the right singular vector matrix of the original image. To evaluate this performance, many tests have been done using a widespread subjective study involving 779 images of the Live Image Quality Assessment Database, Release 2005. The objective results show a high rate of correlation with subjective quality measurements.

Mansouri, Azadeh; Aznaveh, Ahmad Mahmoudi; Torkamani-Azar, Farah; Jahanshahi, J. Afshar

2009-03-01

147

Quality assessment for spectral domain optical coherence tomography (OCT) images  

PubMed Central

Retinal nerve fiber layer (RNFL) thickness, a measure of glaucoma progression, can be measured in images acquired by spectral domain optical coherence tomography (OCT). The accuracy of RNFL thickness estimation, however, is affected by the quality of the OCT images. In this paper, a new parameter, signal deviation (SD), which is based on the standard deviation of the intensities in OCT images, is introduced for objective assessment of OCT image quality. Two other objective assessment parameters, signal to noise ratio (SNR) and signal strength (SS), are also calculated for each OCT image. The results of the objective assessment are compared with subjective assessment. In the subjective assessment, one OCT expert graded the image quality according to a three-level scale (good, fair, and poor). The OCT B-scan images of the retina from six subjects are evaluated by both objective and subjective assessment. From the comparison, we demonstrate that the objective assessment successfully differentiates between the acceptable quality images (good and fair images) and poor quality OCT images as graded by OCT experts. We evaluate the performance of the objective assessment under different quality assessment parameters and demonstrate that SD is the best at distinguishing between fair and good quality images. The accuracy of RNFL thickness estimation is improved significantly after poor quality OCT images are rejected by automated objective assessment using the SD, SNR, and SS.

Liu, Shuang; Paranjape, Amit S.; Elmaanaoui, Badr; Dewelle, Jordan; Rylander, H. Grady; Markey, Mia K.; Milner, Thomas E.

2010-01-01

148

Quality Improvement Guidelines for Uterine Artery Embolization for Symptomatic Leiomyomata  

SciTech Connect

Uterine artery embolization (UAE) is assuming an important role in the treatment of women with symptomatic uterine leiomyomata worldwide. The following guidelines, which have been jointly published with the Society of Interventional Radiology in the Journal of Vascular and Interventional Radiology, are intended to ensure the safe practice of UAE by identifying the elements of appropriate patient selection, anticipated outcomes, and recognition of possible complications and their timely address.

Hovsepian, David M. [Mallinckrodt Institute of Radiology, Division of Vascular and Interventional Radiology (United States)], E-mail: hovsepiand@mir.wustl.edu; Siskin, Gary P. [Albany Medical College, Department of Vascular Radiology (United States); Bonn, Joseph [Thomas Jefferson University Hospital, Department of Radiology (United States)] (and others)

2004-08-15

149

Image reconstruction and image quality evaluation for a dual source CT scanner.  

PubMed

The authors present and evaluate concepts for image reconstruction in dual source CT (DSCT). They describe both standard spiral (helical) DSCT image reconstruction and electrocardiogram (ECG)-synchronized image reconstruction. For a compact mechanical design of the DSCT, one detector (A) can cover the full scan field of view, while the other detector (B) has to be restricted to a smaller, central field of view. The authors develop an algorithm for scan data completion, extrapolating truncated data of detector (B) by using data of detector (A). They propose a unified framework for convolution and simultaneous 3D backprojection of both (A) and (B) data, with similar treatment of standard spiral, ECG-gated spiral, and sequential (axial) scan data. In ECG-synchronized image reconstruction, a flexible scan data range per measurement system can be used to trade off temporal resolution for reduced image noise. Both data extrapolation and image reconstruction are evaluated by means of computer simulated data of anthropomorphic phantoms, by phantom measurements and patient studies. The authors show that a consistent filter direction along the spiral tangent on both detectors is essential to reduce cone-beam artifacts, requiring truncation of the extrapolated (B) data after convolution in standard spiral scans. Reconstructions of an anthropomorphic thorax phantom demonstrate good image quality and dose accumulation as theoretically expected for simultaneous 3D backprojection of the filtered (A) data and the truncated filtered (B) data into the same 3D image volume. In ECG-gated spiral modes, spiral slice sensitivity profiles (SSPs) show only minor dependence on the patient's heart rate if the spiral pitch is properly adapted. Measurements with a thin gold plate phantom result in effective slice widths (full width at half maximum of the SSP) of 0.63-0.69 mm for the nominal 0.6 mm slice and 0.82-0.87 mm for the nominal 0.75 mm slice. The visually determined through-plane (z axis) spatial resolution in a bar pattern phantom is 0.33-0.36 mm for the nominal 0.6 mm slice and 0.45 mm for the nominal 0.75 mm slice, again almost independent of the patient's heart rate. The authors verify the theoretically expected temporal resolution of 83 ms at 330 ms gantry rotation time by blur free images of a moving coronary artery phantom with 90 ms rest phase and demonstrate image noise reduction as predicted for increased reconstruction data ranges per measurement system. Finally, they show that the smoothness of the transition between image stacks acquired in different cardiac cycles can be efficiently controlled with the proposed approach for ECG-synchronized image reconstruction. PMID:19175144

Flohr, T G; Bruder, H; Stierstorfer, K; Petersilka, M; Schmidt, B; McCollough, C H

2008-12-01

150

Simultaneous automatic arteries-veins separation and cerebral blood flow imaging with single-wavelength laser speckle imaging  

NASA Astrophysics Data System (ADS)

Automatic separation of arteries and veins in optical cerebral cortex images is important in clinical practice and preclinical study. In this paper, a simple but effective automatic artery-vein separation method which utilizes single-wavelength coherent illumination is presented. This method is based on the relative temporal minimum reflectance analysis of laser speckle images. The validation is demonstrated with both theoretic simulations and experimental results applied to the rat cortex. Moreover, this method can be combined with laser speckle contrast analysis so that the artery-vein separation and blood flow imaging can be simultaneously obtained using the same raw laser speckle images data to enable more accurate analysis of changes of cerebral blood flow within different tissue compartments during functional activation, disease dynamic, and neurosurgery, which may broaden the applications of laser speckle imaging in biology and medicine.

Feng, Nengyun; Qiu, Jianjun; Li, Pengcheng; Sun, Xiaoli; Yin, Cui; Luo, Weihua; Chen, Shangbin; Luo, Qingming

2011-08-01

151

Unusual Malignant Coronary Artery Anomaly: Results of Coronary Angiography, MR Imaging, and Multislice CT  

SciTech Connect

We report the case of a man with an uncommon anomaly of the origin and course of the left coronary artery. Clinical, coronary angiography, magnetic resonance imaging, and multislice computed tomography findings of this intermittently symptomatic 49 year-old patient with the rare anomaly of his left coronary artery stemming from the right sinus of Valsalva and taking an interarterial and intraseptal course are presented. The diagnostic value of the different imaging modalities is discussed.

Apitzsch, Jonas, E-mail: apitzsch@rad.rwth-aachen.d [RWTH Aachen University, Department of Diagnostic Radiology (Germany); Kuehl, Harald P. [RWTH Aachen University, Department of Cardiology (Germany); Muehlenbruch, Georg; Mahnken, Andreas H. [RWTH Aachen University, Department of Diagnostic Radiology (Germany)

2010-04-15

152

Carotid and vertebral artery dissections: clinical aspects, imaging features and endovascular treatment  

Microsoft Academic Search

Extracranial arterial dissections are a recognised cause of stroke, particularly in young adults. Clinical diagnosis may be\\u000a difficult, and the classical triad of symptoms is uncommon. Imaging plays a pivotal role in the diagnosis of extracranial\\u000a arterial dissections, and this review provides a detailed discussion of the relative merits and limitations of currently available\\u000a imaging modalities. Conventional arteriography has been

Christine M. Flis; H. Rolf Jäger; Paul S. Sidhu

2007-01-01

153

Transorbital Color Doppler Flow Imaging of the Carotid Siphon and Major Arteries at the Base of the Brain  

Microsoft Academic Search

PURPOSE: To describe and evaluate an application of sonography, transorbital color Doppler flow imaging of the carotid siphon and major intracranial arteries, and to compare it with transtemporal color Doppler flow imaging. METHODS: The carotid siphon and major arteries at the base of the brain of 50 healthy volunteers were screened using the transorbital color Doppler flow sonography. These arteries

Han-Hwa Hu; Cheau-Lin Luo; Wen-Yung Sheng; Michael Mu-Huo Teng; Wen-Jang Wong; Yun-On Luk

154

Requirements for imaging vulnerable plaque in the coronary artery using a coded aperture imaging system  

NASA Astrophysics Data System (ADS)

A coded aperture1 plate was employed on a conventional gamma camera for 3D single photon emission computed tomography (SPECT) imaging on small animal models. The coded aperture design was selected to improve the spatial resolution and decrease the minimum detectable activity (MDA) required to image plaque formation in the APoE (apolipoprotein E) gene deficient mouse model when compared to conventional SPECT techniques. The pattern that was tested was a no-two-holes-touching (NTHT) modified uniformly redundant array (MURA) having 1,920 pinholes. The number of pinholes combined with the thin sintered tungsten plate was designed to increase the efficiency of the imaging modality over conventional gamma camera imaging methods while improving spatial resolution and reducing noise in the image reconstruction. The MDA required to image the vulnerable plaque in a human cardiac-torso mathematical phantom was simulated with a Monte Carlo code and evaluated to determine the optimum plate thickness by a receiver operating characteristic (ROC) yielding the lowest possible MDA and highest area under the curve (AUC). A partial 3D expectation maximization (EM) reconstruction was developed to improve signal-to-noise ratio (SNR), dynamic range, and spatial resolution over the linear correlation method of reconstruction. This improvement was evaluated by imaging a mini hot rod phantom, simulating the dynamic range, and by performing a bone scan of the C-57 control mouse. Results of the experimental and simulated data as well as other plate designs were analyzed for use as a small animal and potentially human cardiac imaging modality for a radiopharmaceutical developed at Bristol-Myers Squibb Medical Imaging Company, North Billerica, MA, for diagnosing vulnerable plaques. If left untreated, these plaques may rupture causing sudden, unexpected coronary occlusion and death. The results of this research indicated that imaging and reconstructing with this new partial 3D algorithm improved the SNR, spatial resolution, dynamic range of 4:1 to 6:1, and decreased the MDA required at the site of a plaque by twofold in comparison with other nuclear medicine imaging methods. Recommendations to increase the field of view (FOV) along with a better imaging geometry would enable placement of larger objects (human heart included) within the fully encoded FOV while improving spatial resolution, magnification factors, and efficiency. Further improvements to the algorithm and imaging system may enable novel vulnerable plaque imaging and early detection of coronary artery disease. 1See definitions beginning on page xvii.

Tozian, Cynthia

155

Managed Care Features Affecting Quality for Coronary Artery Disease (CAD).  

National Technical Information Service (NTIS)

Managed care profoundly changed medical care in the US, yet the impact of these changes on the quality of care remains unclear. The primary aim of this study was to determine the aspects of managed care that impact evidence-based quality of care markers a...

E. R. DeLong

2003-01-01

156

Cross-sectional imaging for diagnosis and clinical outcome prediction of acute basilar artery thrombosis.  

PubMed

Basilar artery occlusion is a potentially fatal condition and imaging findings can be subtle. Prompt diagnosis is vital, as recognition may lead to therapeutic recanalization that may improve functional outcome and survival. Furthermore, cross-sectional imaging signs may help predict eventual outcome and, therefore, guide which patients should be subjected to aggressive treatment. Computed tomography (CT) signs include a hyperdense basilar artery that has a high specificity, accuracy, positive and negative predictive value. Evidence regarding the prognostic significance of the hyperdense basilar artery sign is conflicting. Early magnetic resonance imaging (MRI) features include loss of flow void, seen as increased signal intensity within the basilar artery on T2-weigted images and identification of acute thrombus, seen as intermediate signal on T1-weighted images. MRI sequences are more sensitive for early detection of acute ischaemia or infarction, ideally with diffusion-weighted imaging (DWI). Both CT and MR angiography are sensitive for detection of acute thrombus, seen as a filling defect or occlusion. These are the non-invasive imaging techniques of choice to confirm diagnosis, with perhaps the speed and accessibility of CT angiography resulting in this technique being valuable in the acute setting. Several new scoring systems based on arterial segmentation rather than global volume assessment using CT angiography source images and DWI have shown early promise in the prediction of eventual clinical outcome in order to isolate those patients who may benefit from therapeutic recanalization. PMID:21402376

Mortimer, A M; Saunders, T; Cook, J-L

2011-03-12

157

Coronary Artery Calcifications: A Critical Assessment of Imaging Techniques  

Microsoft Academic Search

The presence of coronary artery calcifications is a distinct marker of atherosclerosis and the severity of calcifications is claimed to reflect a patient’s individual plaque burden. Calcium deposits can be detected non-invasively by cardiac computed tomography (CT). This enables detection of coronary artery disease in a subclinical stage, description of the extent of the disease and risk estimation of future

Alexander Lembcke

2007-01-01

158

Low-noise Imaging System with CMOS Sensor for High-Quality Imaging  

Microsoft Academic Search

Image sensors are widely used in the high-volume markets of digital still cameras and camcorders. In recent years, mobile phones with cameras have employed CMOS image sensors because of their low power consumption and single power supply. Initially, CMOS image sensors were inexpensive and provided poor imaging performance. However, more recently, some CMOS image sensors have achieved high-quality imaging performance

Hirofumi Sumi

2006-01-01

159

Improving the Blanco Telescope's delivered image quality  

NASA Astrophysics Data System (ADS)

The V. M. Blanco 4-m telescope at Cerro Tololo Inter-American Observatory is undergoing a number of improvements in preparation for the delivery of the Dark Energy Camera. The program includes upgrades having potential to deliver gains in image quality and stability. To this end, we have renovated the support structure of the primary mirror, incorporating innovations to improve both the radial support performance and the registration of the mirror and telescope top end. The resulting opto-mechanical condition of the telescope is described. We also describe some improvements to the environmental control. Upgrades to the telescope control system and measurements of the dome environment are described in separate papers in this conference.

Abbott, Timothy M. C.; Montane, Andrés; Tighe, Roberto; Walker, Alistair R.; Gregory, Brooke; Smith, R. Christopher; Cisternas, Alfonso

2010-07-01

160

Autofluorescence maps of atherosclerotic human arteries - A new technique in medical imaging  

SciTech Connect

A new medical imaging technique for arterial walls based on laser-induced autofluorescence spectroscopy is reported. The internal surface of isolated arteries with or without atherosclerosis is irradiated with an argon ion laser (458 nm) and the peak intensity of the excited autofluorescence spectrum is related to the composition of the arterial wall. The higher autofluorescence intensity in the range between approximately 480 and 630 nm for grossly calcified tissue compared to normal or noncalcified atherosclerotic tissue is used to produce maps of the arterial wall. These images delineate the calcified areas of the sample with good spatial resolution. If this technique can be adapted to the endoscopic visualization of arteries in vivo (angioscopy), it could become an important tool for the diagnosis of atherosclerosis and for the monitoring of atheroma ablation during laser angioplasty.

Sartori, M.; Sauerbrey, R.; Kubodera, S.; Tittel, F.K.; Roberts, R.; Henry, P.D.

1987-10-01

161

A perceptual quality metric for color-interpolated images  

NASA Astrophysics Data System (ADS)

An objective image quality metric can be used to compare the output of different image processing algorithms, but objective measures are not always well correlated with subjective image quality assessment; the latter implies the use of human observers, thus objective methods able to emulate the Human Visual System (HVS) better than the classical measures are preferred. In this paper a full reference objective metric, based on perceptual criteria and oriented to demosaiced images is proposed. This technique is useful to evaluate the quality of the interpolation techniques implemented in the image processing pipeline of different Digital Still Cameras (DSC).

Guarneri, Ivana; Guarnera, Mirko; Bosco, Angelo; Santoro, Gaetano

2004-10-01

162

Effect of Bismuth Breast Shielding on Radiation Dose and Image Quality in Coronary CT Angiography  

PubMed Central

Background Coronary computed tomographic angiography (CCTA) is associated with high radiation dose to the female breasts. Bismuth breast shielding offers the potential to significantly reduce dose to the breasts and nearby organs, but the magnitude of this reduction and its impact on image quality and radiation dose have not been evaluated. Methods Radiation doses from CCTA to critical organs were determined using metal-oxide-semiconductor field-effect transistors positioned in a customized anthropomorphic whole-body dosimetry verification phantom. Image noise and signal were measured in regions of interest (ROIs) including the coronary arteries. Results With bismuth shielding, breast radiation dose was reduced 46–57% depending on breast size and scanning technique, with more moderate dose reduction to the heart, lungs, and esophagus. However, shielding significantly decreased image signal (by 14.6 HU) and contrast (by 28.4 HU), modestly but significantly increased image noise in ROIs in locations of coronary arteries, and decreased contrast-to-noise ratio by 20.9%.. Conclusions While bismuth breast shielding can significantly decrease radiation dose to critical organs, it is associated with an increase in image noise, decrease in contrast-to-noise, and changes tissue attenuation characteristics in the location of the coronary arteries.

Einstein, Andrew J.; Elliston, Carl D.; Groves, Daniel W.; Cheng, Bin; Wolff, Steven D.; Pearson, Gregory D. N.; Peters, M. Robert; Johnson, Lynne L.; Bokhari, Sabahat; Johnson, Gary W.; Bhatia, Ketan; Pozniakoff, Theodore; Brenner, David J.

2011-01-01

163

Food quality assessment by NIR hyperspectral imaging  

NASA Astrophysics Data System (ADS)

Near infrared reflectance (NIR) spectroscopy is well established in the food industry for rapid compositional analysis of bulk samples. NIR hyperspectral imaging provides new opportunities to measure the spatial distribution of components such as moisture and fat, and to identify and measure specific regions of composite samples. An NIR hyperspectral imaging system has been constructed for food research applications, incorporating a SWIR camera with a cooled 14 bit HgCdTe detector and N25E spectrograph (Specim Ltd, Finland). Samples are scanned in a pushbroom mode using a motorised stage. The system has a spectral resolution of 256 pixels covering a range of 970-2500 nm and a spatial resolution of 320 pixels covering a swathe adjustable from 8 to 300 mm. Images are acquired at a rate of up to 100 lines s-1, enabling samples to be scanned within a few seconds. Data are captured using SpectralCube software (Specim) and analysed using ENVI and IDL (ITT Visual Information Solutions). Several food applications are presented. The strength of individual absorbance bands enables the distribution of particular components to be assessed. Examples are shown for detection of added gluten in wheat flour and to study the effect of processing conditions on fat distribution in chips/French fries. More detailed quantitative calibrations have been developed to study evolution of the moisture distribution in baguettes during storage at different humidities, to assess freshness of fish using measurements of whole cod and fillets, and for prediction of beef quality by identification and separate measurement of lean and fat regions.

Whitworth, Martin B.; Millar, Samuel J.; Chau, Astor

2010-04-01

164

Quality of life after radiofrequency ablation combined with transcatheter arterial chemoembolization for hepatocellular carcinoma: comparison with transcatheter arterial chemoembolization alone  

Microsoft Academic Search

Objective  Comprehensive studies are scarce with regard to the quality of life (QOL) of hepatocellular carcinoma (HCC) patients after\\u000a transcatheter arterial chemoembolization (TACE) and\\/or radiofrequency ablation (RFA) treatment. The purpose of this study\\u000a was to examine the impact of TACE alone and that of the TACE followed by RFA (TACE–RFA) on QOL in HCC patients.\\u000a \\u000a \\u000a \\u000a Methods  QOL was measured using the Functional

Yan-Bin Wang; Min-Hua Chen; Kun Yan; Wei Yang; Ying Dai; Shan-Shan Yin

2007-01-01

165

Impact of waiting time on the quality of life of patients awaiting coronary artery bypass grafting  

Microsoft Academic Search

Background: A lack of resources has created waiting lists for many elective surgical procedures within Canada's universal health care system. Coronary artery by- pass grafting (CABG) for the treatment of atherosclerotic ischemic heart disease is one of these affected surgical procedures. We studied the impact of waiting times on the quality of life of patients awaiting CABG. Methods: A prospective

John Sampalis; Stella Boukas; Moishe Liberman; Tracey Reid; Gilles Dupuis

166

Impact of a history of diabetes mellitus on quality of life after coronary artery bypass grafting  

Microsoft Academic Search

Aim: To describe the improvement in various aspects of quality of life (QoL) after coronary artery bypass grafting (CABG), in relation to a previous history of diabetes mellitus. Patients: All patients from western Sweden who underwent CABG between 1988 and 1991 without simultaneous valve surgery. Methods: Patients were approached with three questionnaires: The Physical Activity Score, the Nottingham Health Profile

J. Herlitz; H. Sjoland; M. Haglid; B. W. Karlson; K. Caidahl; I. Wiklund; M. Hartford; T. Karlsson

1997-01-01

167

Image quality assessment method in intelligent transportation systems  

NASA Astrophysics Data System (ADS)

In modern ITS (Intelligent Transportation Systems), the close shot images captured by camera are used to precise recognition of information of vehicles such as VLP (vehicle license plate), VS(vehicle shape) , VBC(vehicle body color) and etc. The precise recognition of vehicle information seriously depends upon quality of images captured by camera. The assessment of image quality is a meaningful work, which can be used to monitor the working state and adjust the control parameters of camera, further more can guide the recognition of information of vehicle. This paper proposes a novel content-based method of assessing images quality for close shot ones in ITS . The method is objective image quality assessment without reference image, which is point to single image. The assessment includes distortion type and distortion amount. Experiments show the method is valid and robust.

Wang, Bangping; You, Jian; Xiao, Yijun; Wang, Feng

2007-11-01

168

Influence of affective image content on subjective quality assessment.  

PubMed

Image quality assessment (IQA) enables distortions introduced into an image (e.g., through lossy compression or broadcast) to be measured and evaluated for severity. It is unclear to what degree affective image content may influence this process. In this study, participants (n=25) were found to be unable to disentangle affective image content from objective image quality in a standard IQA procedure (single stimulus numerical categorical scale). We propose that this issue is worthy of consideration, particularly in single stimulus IQA techniques, in which a small number of handpicked images, not necessarily representative of the gamut of affect seen in true broadcasting, and unrated for affective content, serve as stimuli. PMID:23201952

van der Linde, Ian; Doe, Rachel M

2012-09-01

169

Ultrasound Imaging of Upper Extremity Arteries: Clinical Applications  

Microsoft Academic Search

\\u000a The objectives of this chapter are to review applications and describe protocols of duplex ultrasound arterial mapping (DUAM)\\u000a of the upper extremities. A literature search revealed multiple arterial applications of duplex ultrasound in the upper extremity.\\u000a Situations in which ultrasound may replace arteriography or other techniques actually employed are also mentioned.The examples\\u000a cited expand the role of the noninvasive vascular

Sergio X. Salles-Cunha

170

Ultrasound Imaging of Upper Extremity Arteries: Clinical Applications  

Microsoft Academic Search

The objectives of this chapter are to review applications and describe protocols of duplex ultrasound arterial mapping (DUAM)\\u000a of the upper extremities. A literature search revealed multiple arterial applications of duplex ultrasound in the upper extremity.\\u000a Situations in which ultrasound may replace arteriography or other techniques actually employed are also mentioned. The examples\\u000a cited expand the role of the noninvasive

Sergio X. Salles-Cunha

171

Coronary Artery Imaging with Contrast-Enhanced MDCT: Extracardiac Findings  

Microsoft Academic Search

OBJECTIVE. The purpose of our study was to evaluate the incidence of extracardiac find- ings on contrast-enhanced MDCT of the coronary arteries and to assess the effect of different field-of-view settings. SUBJECTS AND METHODS. Patients with suspected coronary artery disease (n = 166) were examined with contrast-enhanced MDCT (16 × 0.75 mm focused on the heart) during injection of contrast

Sabine Haller; Christoph Kaiser; Peter Buser; Georg Bongartz; Jens Bremerich

2006-01-01

172

Multiresolution Approach for Noncontact Measurements of Arterial Pulse Using Thermal Imaging  

NASA Astrophysics Data System (ADS)

This chapter presents a novel computer vision methodology for noncontact and nonintrusive measurements of arterial pulse. This is the only investigation that links the knowledge of human physiology and anatomy, advances in thermal infrared (IR) imaging and computer vision to produce noncontact and nonintrusive measurements of the arterial pulse in both time and frequency domains. The proposed approach has a physical and physiological basis and as such is of a fundamental nature. A thermal IR camera was used to capture the heat pattern from superficial arteries, and a blood vessel model was proposed to describe the pulsatile nature of the blood flow. A multiresolution wavelet-based signal analysis approach was applied to extract the arterial pulse waveform, which lends itself to various physiological measurements. We validated our results using a traditional contact vital signs monitor as a ground truth. Eight people of different age, race and gender have been tested in our study consistent with Health Insurance Portability and Accountability Act (HIPAA) regulations and internal review board approval. The resultant arterial pulse waveforms exactly matched the ground truth oximetry readings. The essence of our approach is the automatic detection of region of measurement (ROM) of the arterial pulse, from which the arterial pulse waveform is extracted. To the best of our knowledge, the correspondence between noncontact thermal IR imaging-based measurements of the arterial pulse in the time domain and traditional contact approaches has never been reported in the literature.

Chekmenev, Sergey Y.; Farag, Aly A.; Miller, William M.; Essock, Edward A.; Bhatnagar, Aruni

173

Interpretation of SPECT/CT myocardial perfusion images: common artifacts and quality control techniques.  

PubMed

Nuclear medicine has long played an important role in the noninvasive evaluation of known or suspected coronary artery disease. The development of single photon emission computed tomography (SPECT) led to improved assessments of myocardial perfusion, and the use of electrocardiographic gating made accurate measurements of ventricular wall motion, ejection fractions, and ventricular volumes possible. With the use of hybrid SPECT/computed tomography (CT) scanning systems, the cardiac functional parameters can be measured in a single imaging session. These recent advances in imaging technology have not only enhanced image quality but also improved diagnostic sensitivity and specificity in the detection of clinically relevant coronary artery disease. The CT-based attenuation maps obtained with hybrid SPECT/CT systems also have been useful for improving diagnostic accuracy. However, when attenuation correction and other advanced image data postprocessing techniques are used, unexpected artifacts may arise. The artifacts most commonly encountered are related to the characteristics either of the technology or of the patient. Thus, close attention to the details of acquisition protocols, processing techniques, and image interpretation is needed to ensure high diagnostic quality in myocardial perfusion studies. PMID:22084188

Dvorak, Ryan A; Brown, Richard K J; Corbett, James R

174

Analyzing rendition quality of fine details of MPEG4 image  

Microsoft Academic Search

A solution to the problem of analyzing the rendition quality of fine details of color images on the basis of objective criteria\\u000a is proposed. The results of experimental estimation of MPEG-4 image quality obtained by software analyzer are given.

S. V. Sai

2008-01-01

175

Improvement in image quality of computed radiography systems for mammography  

Microsoft Academic Search

The image quality of three experimental computed radiography (CR) mammography systems was compared through the measurement of commonly accepted image-quality metrics such as modulation transfer function (MTF) and detective quantum efficiency (DQE). The design and configuration of the scanners in the three systems were different in that they had different signal extraction strategies for each storage phosphor screen. Efforts were

Chang-Ying Joseph Yang; Weidong Huang

2008-01-01

176

Telepresence and Video Games: The Impact of Image Quality  

Microsoft Academic Search

This study investigates the impact of video game image quality on telepresence. Past research has demonstrated positive associations between television image quality and presence and video game technology and presence. No study to date, however, has examined the presence effects of video games played in high definition, which is becoming increasingly common due to the diffusion of new TV technologies

Cheryl Campanella Bracken; Paul Skalski

2009-01-01

177

Meat Quality Evaluation by Hyperspectral Imaging Technique: An Overview  

Microsoft Academic Search

During the last two decades, a number of methods have been developed to objectively measure meat quality attributes. Hyperspectral imaging technique as one of these methods has been regarded as a smart and promising analytical tool for analyses conducted in research and industries. Recently there has been a renewed interest in using hyperspectral imaging in quality evaluation of different food

Gamal Elmasry; Douglas F. Barbin; Da-Wen Sun; Paul Allen

2012-01-01

178

Meat Quality Evaluation by Hyperspectral Imaging Technique: an overview  

Microsoft Academic Search

During last two decades, a number of methods have been developed to objectively measure meat quality attributes. Hyperspectral imaging technique as one of these methods has been regarded as a smart and promising analytical tool for analyses conducted in research and industries. Recently there have been renewed interests in using hyperspectral imaging in quality evaluation of different food products. The

Gamal Elmasry; Douglas F. Barbin; Da-Wen Sun; Paul Allen

2011-01-01

179

Quality of the Radiographic Image in Paper Radiography.  

National Technical Information Service (NTIS)

The quality of the radiographic image was investigated by the use of standard ISO wire Image Quality Indicators and ASTM Penetrameters. 10, 20, and 30 mm thick welds on alumunium and steel plates were radiographed using X-ray machines with voltages from 3...

J. C. Domanus H. M. El Fouly

1981-01-01

180

Influence of image acquisition settings on radiation dose and image quality in coronary angiography by 320-detector volume computed tomography: the CORE320 pilot experience.  

PubMed

The objective of this study was to investigate the impact of image acquisition settings and patients' characteristics on image quality and radiation dose for coronary angiography by 320-row computed tomography (CT). CORE320 is a prospective study to investigate the diagnostic performance of 320-detector CT for detecting coronary artery disease and associated myocardial ischemia. A run-in phase in 65 subjects was conducted to test the adequacy of the computed tomography angiography (CTA) acquisition protocol. Tube current, exposure window, and number of cardiac beats per acquisition were adjusted according to subjects' gender, heart rate, and body mass index (BMI). Main outcome measures were image quality, assessed by contrast/noise measurements and qualitatively on a 4-point scale, and radiation dose, estimated by the dose-length-product. Average heart rate at image acquisition was 55.0±7.3 bpm. Median Agatston calcium score was 27.0 (interquartile range 1-330). All scans were prospectively triggered. Single heart beat image acquisition was obtained in 61 of 65 studies (94%). Sixty-one studies (94%) and 437 of 455 arterial segments (96%) were of diagnostic image quality. Estimated radiation dose was significantly greater in obese (5.3±0.4 mSv) than normal weight (4.6±0.3 mSv) or overweight (4.7±0.3 mSv) subjects (P<0.001). BMI was the strongest factor influencing image quality (odds ratio=1.457, P=0.005). The CORE320 CTA image acquisition protocol achieved a good balance between image quality and radiation dose for a 320-detector CT system. However, image quality in obese subjects was reduced compared to normal weight subjects, possibly due to tube voltage/current restrictions mandated by the study protocol. PMID:23185678

Yoneyama, Kihei; Vavere, Andrea L; Cerci, Rodrigo; Ahmed, Rukhsar; Arai, Andrew E; Niinuma, Hiroyuki; Rybicki, Frank J; Rochitte, Carlos E; Clouse, Melvin E; George, Richard T; Lima, Joao A C; Arbab-Zadeh, Armin

2012-06-25

181

Influence of image acquisition settings on radiation dose and image quality in coronary angiography by 320-detector volume computed tomography: the CORE320 pilot experience  

PubMed Central

The objective of this study was to investigate the impact of image acquisition settings and patients' characteristics on image quality and radiation dose for coronary angiography by 320-row computed tomography (CT). CORE320 is a prospective study to investigate the diagnostic performance of 320-detector CT for detecting coronary artery disease and associated myocardial ischemia. A run-in phase in 65 subjects was conducted to test the adequacy of the computed tomography angiography (CTA) acquisition protocol. Tube current, exposure window, and number of cardiac beats per acquisition were adjusted according to subjects' gender, heart rate, and body mass index (BMI). Main outcome measures were image quality, assessed by contrast/noise measurements and qualitatively on a 4-point scale, and radiation dose, estimated by the dose-length-product. Average heart rate at image acquisition was 55.0±7.3 bpm. Median Agatston calcium score was 27.0 (interquartile range 1–330). All scans were prospectively triggered. Single heart beat image acquisition was obtained in 61 of 65 studies (94%). Sixty-one studies (94%) and 437 of 455 arterial segments (96%) were of diagnostic image quality. Estimated radiation dose was significantly greater in obese (5.3±0.4 mSv) than normal weight (4.6±0.3 mSv) or overweight (4.7±0.3 mSv) subjects (P<0.001). BMI was the strongest factor influencing image quality (odds ratio=1.457, P=0.005). The CORE320 CTA image acquisition protocol achieved a good balance between image quality and radiation dose for a 320-detector CT system. However, image quality in obese subjects was reduced compared to normal weight subjects, possibly due to tube voltage/current restrictions mandated by the study protocol.

Yoneyama, Kihei; Vavere, Andrea L.; Cerci, Rodrigo; Ahmed, Rukhsar; Arai, Andrew E.; Niinuma, Hiroyuki; Rybicki, Frank J.; Rochitte, Carlos E.; Clouse, Melvin E.; George, Richard T.; Lima, Joao A.C.; Arbab-Zadeh, Armin

2012-01-01

182

Noninvasive ergonovine maleate provocative testing for coronary artery spasm: the need for routine thallium-201 imaging  

SciTech Connect

We administered ergonovine and used both electrocardiographic monitoring and thallium-/sup 201/ (/sup 201/Tl) imaging to detect reversible ischemia in 100 patients. Patients already established as having coronary artery spasm and those with nonbypassed, proximal, high-grade coronary artery stenosis were excluded. No complication occurred in any patient. The use of thallium imaging in addition to electrocardiographic monitoring resulted in a higher degree of sensitivity than did ECG monitoring alone. Fourteen patients demonstrated evidence of coronary artery spasm as documented by /sup 201/Tl imaging but of the 14, significant ECG changes occurred in only 50%, and classic ST segment elevation in 21%. Thus, in carefully selected patients the noninvasive provocation of coronary spasm can be accomplished safely, but ECG monitoring must be combined with thallium-/sup 201/ imaging to achieve an acceptable degree of sensitivity.

Shanes, J.G.; Krone, R.J.; Fisher, K.; Shah, B.; Eisenkramer, G.; Humphrey, J.R.

1983-01-01

183

Is image quality a function of contrast perception?  

NASA Astrophysics Data System (ADS)

In this retrospective we trace in broad strokes the development of image quality measures based on the study of the early stages of the human visual system (HVS), where contrast encoding is fundamental. We find that while presenters at the Human Vision and Electronic Imaging meetings have frequently strived to find points of contact between the study of human contrast psychophysics and the development of computer vision and image quality algorithms. Progress has not always been made on these terms, although indirect impact of vision science on more recent image quality metrics can be observed.

Haun, Andrew M.; Peli, Eli

2013-03-01

184

Improvement in image quality of computed radiography systems for mammography  

NASA Astrophysics Data System (ADS)

The image quality of three experimental computed radiography (CR) mammography systems was compared through the measurement of commonly accepted image-quality metrics such as modulation transfer function (MTF) and detective quantum efficiency (DQE). The design and configuration of the scanners in the three systems were different in that they had different signal extraction strategies for each storage phosphor screen. Efforts were also made to improve the image quality through changes in phosphor layers, phosphor particle morphology, particle size distribution, and phosphor binder ratio. The effects on overall image quality as a result of these improvements were demonstrated on these systems. It was found that there were significant variations in system MTF and DQE, depending on how the CR system was configured. Higher system MTF does not always lead to higher DQE. Screen designs as well as scanning strategies need to be taken into consideration in order to achieve image quality improvements for the application of mammography.

Yang, Chang-Ying Joseph; Huang, Weidong

2008-04-01

185

Continuous arterial positron monitor for quantitation in PET imaging.  

PubMed

Quantitative measures of physiologic function with PET require continuous monitoring of arterial positron isotope concentration. A device has been developed that automates this process. This device has advantages over manual sampling techniques with syringes since fewer personnel are required, measurements are less error prone, and more continuous measures of arterial positron concentration are available. A constant flow infusion/withdrawal pump withdraws blood from the radial artery through a catheter connected to 0.5 mm inner diameter teflon tubing. This tubing is wrapped around a 50 mm thick by 50 mm diameter NaI(T1) crystal that is interfaced to a photomultiplier tube (PMT) and encased in a cylindrical lead shield. This crystal detects 511 Kev photons that result from positron annihilation. The device sensitivity is greater than 240 (cts/sec)/(microCi/ml) corresponding to a peak activity of approximately 10,000 cts/sec for a 50 mCi bolus injection in an adult. The system dynamic response has been measured and the true arterial input function is recovered by deconvolution. The system has been used clinically for more than 400 human PET studies and has been a reliable continuous monitor of arterial positron concentration. PMID:2252609

Nelson, A D; Muzic, R F; Miraldi, F; Muswick, G J; Leisure, G P; Voelker, W

1990-01-01

186

Minimum average-cost path for real time 3D coronary artery segmentation of CT images.  

PubMed

In this paper, we propose a Minimum Average-cost Path (MACP) model for segmenting 3D coronary arteries by minimizing the average edge cost along path in discrete 4D graph constructed by image voxels and associated radii. Prim's Minimum Spanning Tree method is used for efficient optimization of the MACP model. The centerline and the radii of the cross sections of the coronary artery are extracted simultaneously during the optimization. The method does not need any image preprocessing steps and has been intensively validated as an effective approach with the Rotterdam Coronary Artery Algorithm Evaluation Framework. The computational cost of the proposed method is particularly low (7.467 seconds per segment, 18.5mm/s on average), which makes real time segmentation of coronary artery possible. Shortcut problem, which is a classic issue of the minimal path techniques, can also be overcome by the proposed method. PMID:22003729

Zhu, Ning; Chung, Albert C S

2011-01-01

187

Image quality enhancement in AMOLED microdisplay for mobile projectors  

Microsoft Academic Search

Data driving techniques and circuits to enhance the image quality of the 0.4-inch diagonal VGA AMOLED on silicon substrate have been proposed. The uniformity of a displayed image can be severely degraded by the random offset voltages of the data drivers. The color shift due to the differential OLED material aging is another well-known concern. To alleviate these image quality

Byong-Deok Choi; In-Su Park; Jong-Seok Kim; Sung-Jin Lee; Byung Bae

2011-01-01

188

Practical quality control procedures for digital imaging projects  

Microsoft Academic Search

Abstract Purpose,– Formal quality review processes are a necessary,part of any digital imaging,workflow. This article illustrates a set of quality review processes implemented,in the Indiana University Digital Library Program’s Digital Media and Image Center. Design\\/methodology\\/approach,– A methodology,for automatic,batch review of large numbers,of images is presented, along with rationale and procedures for supplemental visual review. The initial stages of an effort

Jenn Riley; Kurt Whitsel

2005-01-01

189

Quality image metrics for synthetic images based on perceptual color differences  

Microsoft Academic Search

Due to the improvement of image rendering processes, and the increasing importance of quantitative comparisons among synthetic color images, it is essential to define perceptually based metrics which enable to objectively assess the visual quality of digital simulations. In response to this need, this paper proposes a new methodology for the determination of an objective image quality metric, and gives

Stephane Albin; Gilles Rougeron; Bernard Péroche; Alain Trémeau

2002-01-01

190

The influence of different technique factors on image quality of chest radiographs as evaluated by modified CEC image quality criteria  

Microsoft Academic Search

The Commission of the European Communities (CEC) research project ''Predictivity and optimisation in medical radiation protection'' addressed fundamental operational limitations in existing radiation protection mechanisms. The first part of the project aimed at investigating (1) whether the CEC image quality criteria could be used for optimization of a radiographic process and (2) whether significant differences in image quality based on

B LANHEDE; MB ATH; S KHEDDACHE; P SUND; L BJORNELD; M WIDELL; A ALMEN; J BESJAKOV; S MATTSSON; A TINGBERG; W PANZER; M ZANKL

191

The effects of piston error on image quality of synthetical aperture optical imaging system  

NASA Astrophysics Data System (ADS)

The relationship between image quality and piston errors of synthetical aperture optical imaging system has been studied. An active segmented cophasing imaging system and its Zemax simulation model were set up. Diversity piston errors were introduced and the corresponding MTF were calculated with the Zemax simulation model. Simulation experiments have been carried out with the cophasing imaging system, and the results are coincident with the simulated results. The results show that image quality changes with the increase of the piston error periodically if the piston error is smaller than the coherent length of the light source, and the image quality becomes the worst if the piston error is an odd multiple of ?.

Zhang, Jun; Zhao, Weirui; Yang, Feng; Zhang, Lifang

2012-11-01

192

Coronary Artery Bypass Grafting is Associated With Excellent Long-Term Survival and Quality of Life: A Prospective Cohort Study  

Microsoft Academic Search

Background. We investigated the long-term outcome of coronary artery bypass grafting both in terms of survival and quality of life. Methods. Ten-year postsurgery survival was collated on patients undergoing coronary artery bypass grafting from 1994 to 1996, and quality of life was assessed using EQ-5D and a quality-of-life thermometer. We analyzed data from 1,180 patients. Mean age was 61 years,

Joel Dunning; Julian R. L. Waller; Barbara Smith; Sue Pitts; Simon W. H. Kendall; Khalid Khan

193

Regional brand image and perceived wine quality: the consumer perspective  

Microsoft Academic Search

Purpose – The overall aim of this study is to examine the regional brand image of selected California wine regions and the effect of that image on consumers' quality perceptions when included on wine labels. It also seeks to examine the importance of regional brand image with respect to information other than place-of-origin provided on the wine labels. Finally, the

Ray Johnson; Johan Bruwer

2007-01-01

194

Enhancing the low quality images using Unsupervised Colour Correction Method  

Microsoft Academic Search

Underwater images are affected by reduced contrast and non-uniform colour cast due to the absorption and scattering of light in the aquatic environment. This affects the quality and reliability of image processing and therefore colour correction is a necessary pre-processing stage. In this paper, we propose an Unsupervised Colour Correction Method (UCM) for underwater image enhancement. UCM is based on

Kashif Iqbal; Michael Odetayo; Anne E. James; Rosalina Abdul Salam; Abdullah Zawawi Talib

2010-01-01

195

Steganalysis of Watermarking Techniques using Image Quality Metrics  

Microsoft Academic Search

In this paper, we present techniques for steganalysis of images that have been potentially subjected to a watermarking algorithm. Our hypothesis is that a particular watermarking scheme leaves statistical evidence or structure that can be exploited for detection with the aid of proper selection of image features and multivariate regression analysis. We use some sophisticated image quality metrics as the

Nasir Memon; Bülent Sankur

196

The primary research on image color quality evaluation  

Microsoft Academic Search

The image color and vision quality evaluation plays a very important role in the algorithm design and their optimizations of image reconstruction processing. As human eyes are the last receivers for image information, we build a general evaluation model on the HVS (human visual system) and HCPM (human color perception model). According to the psychology and physiology experiments and color

Tao Jing; Yubin Xia; Lei Yan

2000-01-01

197

The simulation of adaptive optical image even and pulse noise and research of image quality evaluation  

NASA Astrophysics Data System (ADS)

As optical image becomes more and more important in adaptive optics area, and adaptive optical telescopes play a more and more important role in the detection system on the ground, and the images we get are so many that we need find a suitable method to choose good quality images automatically in order to save human power, people pay more and more attention in image's evaluation methods and their characteristics. According to different image degradation model, the applicability of different image's quality evaluation method will be different. Researchers have paid most attention in how to improve or build new method to evaluate degraded images. Now we should change our way to take some research in the models of degradation of images, the reasons of image degradation, and the relations among different degraded images and different image quality evaluation methods. In this paper, we build models of even noise and pulse noise based on their definition and get degraded images using these models, and we take research in six kinds of usual image quality evaluation methods such as square error method, sum of multi-power of grey scale method, entropy method, Fisher function method, Sobel method, and sum of grads method, and we make computer software for these methods to use easily to evaluate all kinds of images input. Then we evaluate the images' qualities with different evaluation methods and analyze the results of six kinds of methods, and finally we get many important results. Such as the characteristics of every method for evaluating qualities of degraded images of even noise, the characteristics of every method for evaluating qualities of degraded images of pulse noise, and the best method to evaluate images which affected by tow kinds of noise both and the characteristics of this method. These results are important to image's choosing automatically, and this will help we to manage the images we get through adaptive optical telescopes base on the ground.

Wen, Changli; Xu, Yuannan; Xu, Rong; Liu, Changhai; Men, Tao; Niu, Wei

2013-09-01

198

High resolution in vivo intra-arterial imaging with optical coherence tomography  

Microsoft Academic Search

Background—Optical coherence tomo- graphy (OCT) is a new method of catheter based micron scale imaging. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than sound waves. Objective—To demonstrate the ability of OCT to perform high resolution imaging of arterial tissue in vivo. Methods—OCT imaging of the abdominal aorta of New Zealand white rabbits was performed

J G Fujimoto; S A Boppart; G J Tearney; B E Bouma; C Pitris; M E Brezinski

199

Examples of subjective image quality enhancement in multimedia  

NASA Astrophysics Data System (ADS)

The subjective image quality is an important issue in all multimedia imaging systems with a significant impact onto QoS (Quality of Service). For long time the image fidelity criterion was widely applied in technical systems esp. in both television and image source compression fields but the optimization of subjective perception quality and fidelity approach (such as the minimum of MSE) are very different. The paper presents an experimental testing of three different digital techniques for the subjective image quality enhancement - color saturation, edge enhancement, denoising operators and noise addition - well known from both the digital photography and video. The evaluation has been done for extensive operator parameterization and the results are summarized and discussed. It has been demonstrated that there are relevant types of image corrections improving to some extent the subjective perception of the image. The above mentioned techniques have been tested for five image tests with significantly different image characteristics (fine details, large saturated color areas, high color contrast, easy-to-remember colors etc.). The experimental results show the way to optimized use of image enhancing operators. Finally the concept of impressiveness as a new possible expression of subjective quality improvement is presented and discussed.

Klíma, Miloš; Pazderák, Ji?í; Fliegel, Karel

2007-10-01

200

A framework for automated coronary artery tracking of low axial resolution multi slice CT images  

NASA Astrophysics Data System (ADS)

Low axial resolution data such as multi-slice CT(MSCT) used for coronary artery disease screening must balance the potential loss in image clarity, detail and partial volume effects with the benefits to the patient such as faster acquisition time leading to lower dose exposure. In addition, tracking of the coronary arteries can aid the location of objects contained within, thus helping to differentiate them from similar in appearance, difficult to discern neighbouring regions. A fully automated system has been developed to segment and track the main coronary arteries and visualize the results. Automated heart isolation is carried out for each slice of an MSCT image using active contour methods. Ascending aorta and artery root segmentation is performed using a combination of active contours, morphological operators and geometric analysis of coronary anatomy to identify a starting point for vessel tracking. Artery tracking and backtracking employs analysis of vessel position combined with segmented region shape analysis to obtain artery paths. Robust, accurate threshold parameters are calculated for segmentation utilizing Gaussian Mixture Model fitting and analysis. The low axial resolution of our MSCT data sets, in combination with poor image clarity and noise presented the greatest challenge. Classification techniques such as shape analysis have been utilized to good effect and our results to date have shown that such deficiencies in the data can be overcome, further promoting the positive benefits to patients.

Wu, Jing; Ferns, Gordon; Giles, John; Lewis, Emma

2011-03-01

201

Safety of Intravenous Fibrinolysis in Imaging-Confirmed Single Penetrator Artery Infarcts  

PubMed Central

Background Hemorrhagic transformation (HT) after fibrinolytic therapy may be less common in patients with acute cerebral ischemia confined to single penetrator artery (SPA) territories than in patients with large artery ischemia. However, prior investigations of HT diagnosed small vessel ischemia based on lacunar clinical syndromes, an approach known to yield misdiagnosis in one-third to one-half of cases. Methods Consecutive intravenous t-PA treated patients in a prospectively maintained hospital registry were analyzed. Patients were classified as having SPA ischemia if they had imaging evidence of: 1) deep location, 2) diameter ?1.5 cm, and 3) distribution in a single penetrator territory, regardless of presenting clinical syndrome. Lacunar clinical syndrome was defined according to the Oxfordshire Community Stroke Project classification. Results Among 93 intravenous t-PA-treated patients, mean age was 71.5, 62.4% were female, and median pretreatment NIHSS score was 14. Single penetrator artery ischemia was imaged in 13 (14.0%) and large artery ischemia in 75 (80.6%), with no visualized ischemic injury in 5 (5.4%). Lacunar clinical syndromes were present in 23 (24.7%), including 10 with SPA ischemia and 9 with large artery ischemia. No patient with imaging-confirmed SPA infarcts experienced any hemorrhagic transformation, while any radiologic HT occurred in 29.3% of large artery infarcts, p = 0.03. Symptomatic ICH occurred in 0% of SPA infarcts vs. 4.0% of large artery infarcts. Conclusion HT after lytic therapy in imaging-confirmed SPA infarcts is uncommon. Imaging demonstration of ischemia confined to a SPA territory better identifies this population at low risk of hemorrhagic complications than clinical lacunar syndromes.

Lee, Soo Joo; Saver, Jeffrey L.; Liebeskind, David S.; Ali, Latisha; Ovbiagele, Bruce; Kim, Doojin; Vespa, Paul; Froehler, Michael; Tenser, Matthew; Gadhia, Jignesh; Starkman, Sidney

2011-01-01

202

Automatic segmentation of the lumen of the carotid artery in ultrasound B-mode images  

NASA Astrophysics Data System (ADS)

A new algorithm is proposed for the segmentation of the lumen and bifurcation boundaries of the carotid artery in B-mode ultrasound images. It uses the hipoechogenic characteristics of the lumen for the identification of the carotid boundaries and the echogenic characteristics for the identification of the bifurcation boundaries. The image to be segmented is processed with the application of an anisotropic diffusion filter for speckle removal and morphologic operators are employed in the detection of the artery. The obtained information is then used in the definition of two initial contours, one corresponding to the lumen and the other to the bifurcation boundaries, for the posterior application of the Chan-vese level set segmentation model. A set of longitudinal B-mode images of the common carotid artery (CCA) was acquired with a GE Healthcare Vivid-e ultrasound system (GE Healthcare, United Kingdom). All the acquired images include a part of the CCA and of the bifurcation that separates the CCA into the internal and external carotid arteries. In order to achieve the uppermost robustness in the imaging acquisition process, i.e., images with high contrast and low speckle noise, the scanner was adjusted differently for each acquisition and according to the medical exam. The obtained results prove that we were able to successfully apply a carotid segmentation technique based on cervical ultrasonography. The main advantage of the new segmentation method relies on the automatic identification of the carotid lumen, overcoming the limitations of the traditional methods.

Santos, André M. F.; Tavares, Jão. Manuel R. S.; Sousa, Luísa; Santos, Rosa; Castro, Pedro; Azevedo, Elsa

2013-02-01

203

Carotid artery and aortic arch imaging with ECG gating in DSA  

SciTech Connect

New computer software for gated digital subtraction angiography imaging was used to study 57 patients over 3 months. Better mask registration on isolated sets of systolic and diastolic images improved image quality. Detail of vessel outline and lesion was better than that seen on nongated images.

Francis, D.A.; Sheldon, J.J.; Soila, K.; Tobias, J.

1985-06-01

204

Lower use of carotid artery imaging at minority-serving hospitals  

PubMed Central

Objective: We determined whether site of care explains a previously identified racial disparity in carotid artery imaging. Methods: In this retrospective cohort study, data were obtained from a chart review of veterans hospitalized with ischemic stroke at 127 Veterans Administration hospitals in 2007. Extensive exclusion criteria were applied to obtain a sample who should have received carotid artery imaging. Minority-serving hospitals were defined as the top 10% of hospitals ranked by the proportion of stroke patients who were black. Population level multivariate logistic regression models with adjustment for correlation of patients in hospitals were used to calculate predictive probabilities of carotid artery imaging by race and minority-service hospital status. Bootstrapping was used to obtain 95% confidence intervals (CIs). Results: The sample consisted of 1,534 white patients and 628 black patients. Nearly 40% of all black patients were admitted to 1 of 13 minority-serving hospitals. No racial disparity in receipt of carotid artery imaging was detected within nonminority serving hospitals. However, the predicted probability of receiving carotid artery imaging for white patients at nonminority-serving hospitals (89.7%, 95% CI [87.3%, 92.1%]) was significantly higher than both white patients (78.0% [68.3%, 87.8%] and black patients (70.5% [59.3%, 81.6%]) at minority-serving hospitals. Conclusions: Underuse of carotid artery imaging occurred most often among patients hospitalized at minority-serving hospitals. Further work is required to explore why site of care is a mechanism for racial disparities in this clinically important diagnostic test.

Keyhani, Salomeh; Ofner, Susan; Williams, Linda S.; Hebert, Paul L.; Ordin, Diana L.; Bravata, Dawn M.

2012-01-01

205

Quality criteria for simulator images - A literature review  

Microsoft Academic Search

Quality criteria are presented for each of about 30 different outside-world image features of computer-generated image systems on vehicle simulators (e.g., airplane, tank, ship). Criteria derived are based on a literature review. In addition to purely physical properties related to image presentation (e.g., field size, contrast ratio, update frequency), attention is paid to image content (e.g., number of polygons, surface

Pieter Padmos; Maarten V. Milders

1992-01-01

206

No-reference image quality assessment using visual codebooks.  

PubMed

The goal of no-reference objective image quality assessment (NR-IQA) is to develop a computational model that can predict the human-perceived quality of distorted images accurately and automatically without any prior knowledge of reference images. Most existing NR-IQA approaches are distortion specific and are typically limited to one or two specific types of distortions. In most practical applications, however, information about the distortion type is not really available. In this paper, we propose a general-purpose NR-IQA approach based on visual codebooks. A visual codebook consisting of Gabor-filter-based local features extracted from local image patches is used to capture complex statistics of a natural image. The codebook encodes statistics by quantizing the feature space and accumulating histograms of patch appearances. This method does not assume any specific types of distortions; however, when evaluating images with a particular type of distortion, it does require examples with the same or similar distortion for training. Experimental results demonstrate that the predicted quality score using our method is consistent with human-perceived image quality. The proposed method is comparable to state-of-the-art general-purpose NR-IQA methods and outperforms the full-reference image quality metrics, peak signal-to-noise ratio and structural similarity index on the Laboratory for Image and Video Engineering IQA database. PMID:22410336

Ye, Peng; Doermann, David

2012-03-06

207

Three-Dimensional Coronary Artery Microscopy by Intracoronary Optical Frequency Domain Imaging  

PubMed Central

Objectives We present the first clinical experience with intracoronary optical frequency domain imaging (OFDI) in human patients. Background Intracoronary optical coherence tomography (OCT) is a catheter-based optical imaging modality that is capable of providing microscopic (?7-?m axial resolution, ?30-?m transverse resolution), cross-sectional images of the coronary wall. Although the use of OCT has shown substantial promise for imaging coronary microstructure, blood attenuates the OCT signal, necessitating prolonged, proximal occlusion to screen long arterial segments. OFDI is a second-generation form of OCT that is capable of acquiring images at much higher frame rates. The increased speed of OFDI enables rapid, 3-dimensional imaging of long coronary segments after a brief, nonocclusive saline purge. Methods Volumetric OFDI images were obtained in 3 patients after intracoronary stent deployment. Imaging was performed in the left anterior descending and right coronary arteries with the use of a nonocclusive saline purge rates ranging from 3 to 4 ml/s and for purge durations of 3 to 4 s. After imaging, the OFDI datasets were segmented using previously documented criteria and volume rendered. Results Good visualization of the artery wall was obtained in all cases, with clear viewing lengths ranging from 3.0 to 7.0 cm at pullback rates ranging from 5 to 20 mm/s. A diverse range of microscopic features were identified in 2 and 3 dimensions, including thin-capped fibroatheromas, calcium, macrophages, cholesterol crystals, bare stent struts, and stents with neointimal hyperplasia. There were no complications of the OFDI procedure. Conclusions Our results demonstrate that OFDI is a viable method for imaging the microstructure of long coronary segments in patients. Given its ability to provide microscopic information in a practical manner, this technology may be useful for studying human coronary pathophysiology in vivo and as a clinical tool for guiding the management of coronary artery disease. (J Am Coll Cardiol Img 2008;1:752–61)

Tearney, Guillermo J.; Waxman, Sergio; Shishkov, Milen; Vakoc, Benjamin J.; Suter, Melissa J.; Freilich, Mark I.; Desjardins, Adrien E.; Oh, Wang-Yul; Bartlett, Lisa A.; Rosenberg, Mireille; Bouma, Brett E.

2010-01-01

208

Image quality improvement in inspection systems using double integrator illumination  

NASA Astrophysics Data System (ADS)

The most annoying problem accompanying production of high-fidelity pattern images in mask defect inspection systems is the generation of virtual images in the imaging process. The focused image pattern on the image acquisition sensor has two images, one true and one virtual. The virtual images are generated under Kohler's illumination using an integrator. The theoretical cause of this virtual image is the periodicity of the integrator. The improvement of image quality gives the mask defect inspection system higher defect detection sensitivity. To reduce virtual images, the double integrator method is applied to the illumination optics. By adopting the double integrator illumination method, virtual images disappear in the imaging field. Further, since this also lowers the power density at bright spots, the interference of lenses in working environments at the aperture stop position between objective imaging lenses is greatly reduced. This paper reports a method by which the ill effects of image quality improvement in the mask defect inspection system can be dramatically reduced. The simulation results when this method is applied to an advanced mask defect inspection system are shown.

Takada, Akira; Suzuki, Hitoshi; Tojo, Toru; Shibuya, Masato

2007-03-01

209

Laser ablation and the need for intra-arterial imaging  

Microsoft Academic Search

In 48 patients with severe claudication due to a total obstruction of the femoropopliteal artery, percutaneous recanalization was attempted with a 2.2 mm diameter rounded sapphire contact probe in conjunction with a continuous wave Nd:YAG laser. In eight patients the contact probe laser catheter took a subintimal course that could not be redressed. Laser recanalization needs high-resolution diagnostic information on

C. Borst; R. Rienks; W. P. T. M. Mali; L. van Erven

1989-01-01

210

Association between obesity and health-related quality of life in patients with coronary artery disease  

Microsoft Academic Search

Background and Objective:In patients with coronary artery disease (CAD), obesity is paradoxically associated with better survival (the ‘obesity paradox’). Our objective was to determine whether this counterintuitive relationship extends to health-related quality of life (HRQOL) outcomes.Design:Cross-sectional observational study.Subjects:All adults undergoing coronary angiography residing in Alberta, Canada between January 2003 and March 2006 in the Alberta Provincial Project for Outcome Assessment

A Oreopoulos; R Padwal; F A McAlister; J Ezekowitz; A M Sharma; K Kalantar-Zadeh; G C Fonarow; C M Norris

2010-01-01

211

Quality of life in patients with coronary artery disease and the impact of depression  

Microsoft Academic Search

Depression has been shown to be a risk factor for the development of coronary artery disease, and also is associated with\\u000a greater risk of mortality in patients with coronary disease. Treatment of depression may or may not prove to alter depression\\u000a as a risk factor, but improving the quality of life (QOL) of patients with coronary disease also should be

J. Robert Swenson

2004-01-01

212

Impact of coronary artery bypass grafting on various aspects of quality of life  

Microsoft Academic Search

Objective: To prospectively study the improvement in quality of life (QoL) after coronary artery bypass surgery (CABG). Patients and Methods: Consecutive patients (n=2121) who underwent CABG at Sahlgrenska University Hospital between 1988 and 1991 received 3 questionnaires for the study of QoL: the Physical Activity Score, the Nottingham Health Profile and the Psychological General Well-being Index, which were responded both

Helén Sjöland; Kenneth Caidahl; Ingela Wiklund; Maria Haglid; Marianne Hartford; Björn W Karlson; Thomas Karlsson; Johan Herlitz

1997-01-01

213

Perceived image quality of MPEG-2 stereoscopic sequences  

NASA Astrophysics Data System (ADS)

Image quality of stereoscopic video sequences were assessed by non-expert viewers, using a subjective assessment method, as described in ITU-R Recommendation 500. Three 10-second stereo sequences, in the ITU-R 601 format, were assessed. Using a standard MPEG-2 codec, images of the left-eye views of each sequence were compressed independently of the right-eye views, at bit rates of 1, 2, 3, and 6 Mb/s. Twenty-six viewers rated the overall image quality for various combinations of the compressed left- and right-eye views. Viewers also rated non- stereo sequences, which consisted of images of the right-eye views for both eyes. Ratings of overall image quality were between 60 - 70 units, corresponding to a label of 'good,' except when the severity of artifacts presented to one eye was large, i.e., when the bit rate was below 3 Mb/s. When there was a mismatch in quality of inputs to the two eyes, ratings of overall perceived quality fell halfway between ratings of quality for the left-eye input and the right-eye input. Interestingly, ratings of image quality for stereo sequences were equal to non-stereo sequences, except at the lowest bit rate tested (1 Mb/s).

Tam, Wa James; Stelmach, Lew B.

1997-06-01

214

Pseudo no reference image quality metric using perceptual data hiding  

NASA Astrophysics Data System (ADS)

Regarding the important constraints due to subjective quality assessment, objective image quality assessment has recently been extensively studied. Such metrics are usually of three kinds, they might be Full Reference (FR), Reduced Reference (RR) or No Reference (NR) metrics. We focus here on a new technique, which recently appeared in quality assessment context: data-hiding-based image quality metric. Regarding the amount of data to be transmitted for quality assessment purpose, watermarking based techniques are considered as pseudo noreference metric: A little overhead due to the embedded watermark is added to the image. Unlike most existing techniques, the proposed embedding method exploits an advanced perceptual model in order to optimize both the data embedding and extraction. A perceptually weighted watermark is embedded into the host image, and an evaluation of this watermark allows to assess the host image's quality. In such context, the watermark robustness is crucial; it must be suffciently robust to be detected after very strong distortions, but it must also be suffciently fragile to be degraded along with the host image. In other words, the watermark distortion must be proportional to the image's distortion. Our work is compared to existing standard RR and NR metrics in terms of both the correlation with subjective assessment and of data overhead induced by the mark.

Ninassi, Alexandre; Le Callet, Patrick; Autrusseau, Florent

2006-02-01

215

Changes in health-related quality of life and functional capacity following coronary artery bypass graft surgery  

Microsoft Academic Search

Objective: Improvement in survival and quality of life are the primary indications for coronary artery bypass graft (CABG) operations. Among elderly patients the main goal of surgery is not necessarily to prolong life, but to improve the health-related quality of life. Factors associated with mortality and morbidity following CABG surgery have been well defined, but the quality of life and

Otso Järvinen; Timo Saarinen; Juhani Julkunen; Heini Huhtala; Matti R. Tarkka

2003-01-01

216

Carotid Artery Stenosis: Optimization of CT Angiography with a Combination of Shaded Surface Display and Source Images  

Microsoft Academic Search

PURPOSE: To evaluate the accuracy of CT angiography of occlusive disease of the carotid arteries using three-dimensional surface-rendered images alone and in conjunction with display of axial source images. METHODS: Forty-eight symptomatic patients had conventional angiography followed by CT angiography within 24 hours. Images of 96 carotid arteries were acquired using contrast-enhanced spiral CT. Image postprocessing was performed on a

Zsuzsanna Papp; Mahendra Patel; Manzar Ashtari; Masashi Takahashi; Jacques Goldstein; William Maguire; Peter G. Herman

1997-01-01

217

On the visual quality enhancement of super-resolution images  

NASA Astrophysics Data System (ADS)

Super-resolution (SR) is the process of obtaining a higher resolution image from a set of lower resolution (LR) blurred and noisy images. One may, then, envision a scenario where a set of LR images is acquired with a sensor on a moving platform. In such a case, an SR image can be reconstructed in an area of sufficient overlap between the LR images which generally have a relative shift with respect to each other by subpixel amounts. The visual quality of the SR image is affected by many factors such as the optics blur, the inherent signalto- noise ratio of the system, quantization artifacts, the number of scenels (scene elements) i.e., the number of overlapped images used for SR reconstruction within the SR grid and their relative arrangement. In most cases of microscanning, the subpixel shifts between the LR images are pre-determined: hence the number of the scenels within the SR grid and their relative positions with respect to each other are known and, as a result, can be used in obtaining the reconstructed SR image with high quality. However, the LR images may have relative shifts that are unknown. This random pattern of subpixel shifts can lead to unpleasant visual quality, especially at the edges of the reconstructed SR image. Also, depending on the available number of the LR images and their relative positions, it may be possible to produce SR only along a single dimension diagonal, horizontal or vertical and use interpolation in the orthogonal dimension because there isn't sufficient information to produce a full 2D image. We investigate the impact of the number of overlapped regions and their relative arrangement on the quality of the SR images, and propose a technique that optimally allocates the available LR scenels to the SR grid in order to minimize the expected unpleasant visual artifacts.

Yousef, Amr Hussein; Li, Jiang; Karim, Mohammad

2011-09-01

218

Biomarker, Imaging and Quality of LIfe Studies Funding Program (BIQSFP)  

Cancer.gov

Funded Cooperative Groups (CGs) and funded Community Clinical Oncology Program (CCOP) Research Bases are invited to apply for funding to support essential biomarker, imaging, and quality of life studies which are associated with clinical trial concepts.

219

No-reference image quality measurement for low-resolution images  

NASA Astrophysics Data System (ADS)

No-reference measurement for image quality, where an original error-free image is not provided as reference, plays an important role in image processing and analysis. This paper mainly investigates three no-reference image-quality metrics, which are based on the standard deviation, the maximum, and the mean of the magnitude of the intensity gradient of pixels. Each measurement metric is critically accessed using low resolution gray-scale images, which are acquired by unmanned aerial vehicles cruising over the city and aim to disclose the movement of vehicles such as a semi -truck, light colored cars, and dark colored cars, etc. The experimental results demonstrate that, compared to alternative schemes, the standard deviation based metric provides a more accurate measurement about the quality of images. In addition, standard deviation based scheme demonstrates superior correlation with alternative schemes to measure the quality of images.

Sanderson, Josh; Liang, Yu

2013-05-01

220

Image-based modeling of the hemodynamics in cerebral arterial trees  

NASA Astrophysics Data System (ADS)

Knowledge of the hemodynamics in normal arterial trees of the brain is important to better understand the mechanisms responsible for the initiation and progression of cerebrovascular diseases. Information about the baseline values of hemodynamic variables such as velocity magnitudes, swirling flows, wall shear stress, pressure drops, vascular resistances, etc. is important for characterization of the normal hemodynamics and comparison with pathological states such as aneurysms and stenoses. This paper presents image-based computational hemodynamics models of cerebral arterial trees constructed from magnetic resonance angiography (MRA) images. The construction of large models of cerebral arterial trees is challenging because of the following main reasons: a) it is necessary to acquire high resolution angiographic images covering the entire brain, b) it is necessary to construct topologically correct and geometrically accurate watertight models of the vasculature, and c) the models typically result in large computational grids which make the calculations computationally demanding. This paper presents a methodology to model the hemodynamics in the brain arterial network that combines high resolution MRA at 3T, a vector representation of the vascular structures based on semi-manual segmentation, and a novel algorithm to solve the incompressible flow equations efficiently in tubular geometries. These techniques make the study of the hemodynamics in the cerebral arterial network practical.

Mut, Fernando; Wright, Susan; Putman, Christopher; Ascoli, Giorgio; Cebral, Juan

2009-02-01

221

Objective Quality Assessment Measurement for Typhoon Cloud Image Enhancement  

Microsoft Academic Search

There are kinds of enhancement methods for satellite image, however, visual quality of them are basically assessed by human\\u000a eyes. This can result in wrong identification. This will result in wrong prediction for center and intensity of the typhoon.\\u000a It is necessary to find an objective measure to evaluate the visual quality for enhanced typhoon cloud image. In order to

Changjiang Zhang; Juan Lu; Jinshan Wang

2009-01-01

222

Quantification and characterisation of arteries in retinal images  

Microsoft Academic Search

A computerised system is presented for the automatic quantification of blood vessel topography in retinal images. This system utilises digital image processing techniques to provide more reliable and comprehensive information for the retinal vascular network. It applies strategies and algorithms for measuring vascular trees and includes methods for locating the centre of a bifurcation, detecting vessel branches, estimating vessel diameter,

Xiaohong W. Gao; Anil A. Bharath; Alice V. Stanton; Alun D. Hughes; Neil Chapman; Simon A. Thom

2000-01-01

223

Continuous assessment of time-varying image quality  

NASA Astrophysics Data System (ADS)

For the optimization of digital imaging systems it is crucial to known how parameter settings affect the perceptual quality of displayed images. This calls for valid techniques for assessing image quality. Here, we studied continuous assessment of the instantaneous quality impression of long image sequences. Initially, we concentrated on the measuring method. Subjects were instructed to indicate quality by mooing a slider along a graphical scale. With a sequence consisting of time-variably blurred stills the temporal characteristics of continuous scaling could be separated from the relation between blur and quality impression. The temporal behavior can be explained by a causal linear time-filter. Subsequently, we extended the method to real video. In order to check the validity of continuous scaling, perceived quality of the video at any moment in time was measured by partitioning the video in short fragments and evaluating the quality of each fragment separately. The image material was MPEG-2 coded at 2 Mbit/s. The relation between the time-quality curves from the continuous assessment and the instantaneous ratings of the fragments is described by the same time-filter as found previously. This filter indicates a delay of 1 second, and suggests that subjects can monitor image quality variations almost instantaneously. With these experiments, we have shown that it is possible to measure quality of video sequences continuously in a consistent way. As confirmed in a third experiment, the results of continuous assessment give the possibility to select relevant material for further analysis, for instance by standard ITU/R methods.

Hamberg, Roelof; de Ridder, Huib

1997-06-01

224

Flow and distension in the carotid artery from magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Hemodynamic conditions in the carotid artery may be associated with progression of carotid artery (CA) disease and with the risk of stroke. A methodology for objective measurement of distension (DCA) and blood-flow (QCA) waveform from phase-contrast (PC) magnetic resonance (MR) imaging is presented. Measurement of DCA is obtained using a modified Hough Transform (mHT) applied to the magnitude-component of the PC MR. The mHT is based on the optimization of an objective function which is the sum of the gradient magnitude of the image sampled at 10° increments around the circle using bilinear interpolation. The mHT detects the boundary of the vessel in the cross-sectional image at 0.05-pixel resolution. Measurement of QCA is obtained by integration of the image intensity in the phase-component of the PC MR within the circular region detected by the mHT.

Yim, Peter J.; Demarco, J. K.

2004-04-01

225

Diffusion weighted imaging reversibility in the brainstem following successful recanalization of acute basilar artery occlusion.  

PubMed

Acute basilar artery occlusion (ABAO) is a devastating disease that can produce significant brainstem injury. Pretreatment diffusion weighted imaging (DWI) demonstrating extensive brainstem involvement has been shown to predict a poor outcome regardless of reperfusion. This case report describes a patient presenting with coma secondary to ABAO. MRI at presentation demonstrated significant DWI abnormality in the majority of the bilateral pons. The basilar artery was endovascularly recanalized 8 h after stroke onset, and the patient had a marked clinical recovery with no deficit at 3 months. Follow-up imaging revealed significant reversal of the pontine lesion. This finding of brainstem DWI reversibility cautions against the use of DWI to select ABAO patients for intra-arterial stroke therapy. The degree of apparent diffusion coefficient reduction on pretreatment MRI may not adequately identify which DWI abnormal brainstem tissue is potentially reversible. PMID:21990621

Yoo, Albert J; Hakimelahi, Reza; Rost, Natalia S; Schaefer, Pamela W; Hirsch, Joshua A; González, R Gilberto; Rabinov, James D

2010-06-04

226

Objective image quality assessment based on support vector regression.  

PubMed

Objective image quality estimation is useful in many visual processing systems, and is difficult to perform in line with the human perception. The challenge lies in formulating effective features and fusing them into a single number to predict the quality score. In this brief, we propose a new approach to address the problem, with the use of singular vectors out of singular value decomposition (SVD) as features for quantifying major structural information in images and then support vector regression (SVR) for automatic prediction of image quality. The feature selection with singular vectors is novel and general for gauging structural changes in images as a good representative of visual quality variations. The use of SVR exploits the advantages of machine learning with the ability to learn complex data patterns for an effective and generalized mapping of features into a desired score, in contrast with the oft-utilized feature pooling process in the existing image quality estimators; this is to overcome the difficulty of model parameter determination for such a system to emulate the related, complex human visual system (HVS) characteristics. Experiments conducted with three independent databases confirm the effectiveness of the proposed system in predicting image quality with better alignment with the HVS's perception than the relevant existing work. The tests with untrained distortions and databases further demonstrate the robustness of the system and the importance of the feature selection. PMID:20100674

Narwaria, Manish; Lin, Weisi

2010-01-22

227

The use of the general image quality equation in the design and evaluation of imaging systems  

NASA Astrophysics Data System (ADS)

The design of any modern imaging system is the end result of many trade studies, each seeking to optimize image quality within real world constraints such as cost, schedule and overall risk. The National Imagery Interpretability Rating Scale (NIIRS) is a useful measure of image quality, because, by characterizing the overall interpretability of an image, it combines into one metric those contributors to image quality to which a human interpreter is most sensitive. The main drawback to using a NIIRS rating as a measure of image quality in engineering trade studies is the fact that it is tied to the human observer and cannot be predicted from physical principles and engineering parameters alone. The General Image Quality Equation (GIQE) of Leachtenauer et al. 1997 [Appl. Opt. 36, 8322-8328 (1997)] is a regression of actual image analyst NIIRS ratings vs. readily calculable engineering metrics, and provides a mechanism for using the expected NIIRS rating of an imaging system in the design and evaluation process. In this paper, we will discuss how we use the GIQE in conjunction with The Aerospace Corporation's Parameterized Image Chain Analysis & Simulation SOftware (PICASSO) to evaluate imager designs, taking a hypothetical high resolution commercial imaging system as an example.

Cota, Steve A.; Florio, Christopher J.; Duvall, David J.; Leon, Michael A.

2009-08-01

228

Study of digital mammographic equipments by phantom image quality.  

PubMed

Nowadays, the digital radiographic equipments are replacing the traditional film-screen equipments and it is necessary to update the parameters to guarantee the quality of the process. Contrast-detail phantoms are applied to digital radiography to study the threshold contrast-detail sensitivity at operation conditions of the equipment. The phantom that is studied in this work is CDMAM 3.4. One of the most extended indexes to measure the image quality in an objective way is the image quality figure (IQF). The aim of this work is to study the image quality of different images contrast-detail phantom CDMAM 3.4, carrying out the automatic detection of the contrast-detail combination and to establish a parameter which characterize in an objective way the mammographic image quality. This is useful to compare images obtained at different digital mammographic equipments to study the functioning of the equipments that facilitates the evaluation of image contrast and detail resolution. PMID:17946081

Mayo, P; Rodenas, F; Verdú, G; Campayo, J M; Villaescusa, J I

2006-01-01

229

Distal Embolization After Stenting of the Vertebral Artery: Diffusion-Weighted Magnetic Resonance Imaging Findings  

SciTech Connect

Purpose. We retrospectively evaluated our experience with stenting of the vertebral artery in an effort to determine the risk of distal embolization associated with the procedure. Methods. Between June 2000 and May 2005, 35 patients with 38 stenting procedures for atherosclerotic disease of the vertebral origin in our institution were identified. The average age of the patients was 60.3 years (range 32-76 years). Sixteen of these patients (with 18 stents) had MR imaging of the brain with diffusion-weighted imaging and an apparent diffusion coefficient map within 2 days before and after procedure. Results. On seven of the 16 postprocedural diffusion-weighted MR images, a total of 57 new hyperintensities were visible. All these lesions were focal in nature. One patient demonstrated a new diffusion-weighted imaging abnormality in the anterior circulation without MR evidence of posterior circulation ischemia. Six of 16 patients had a total of 25 new lesions in the vertebrobasilar circulation in postprocedural diffusion-weighted MR images. One patient in this group was excluded from the final analysis because the procedure was complicated by basilar rupture during tandem stent deployment in the basilar artery. Hence, new diffusion-weighted imaging abnormalities were noted in the vertebrobasilar territory in 5 of 15 patients after 17 stenting procedures, giving a 29% rate of diffusion-weighted imaging abnormalities per procedure. No patient with bilateral stenting had new diffusion-weighted imaging abnormalities. Conclusion. Stenting of stenoses of the vertebral artery origin may be associated with a significant risk of asymptomatic distal embolization. Angiography, placement of the guiding catheter, inflation of the stent balloon, and crossing the lesion with guidewires or balloon catheters may potentially cause distal embolization. Further studies to evaluate measures to increase the safety of vertebral artery stenting, such as the use of distal protection devices or short-term postprocedural anticoagulation, should be considered for patients with clear indications for this procedure.

Canyigit, Murat [Hacettepe University School of Medicine, Department of Radiology (Turkey); Arat, Anil [Baylor College of Medicine, Department of Radiology (United States)], E-mail: anilarat@netscape.net; Cil, Barbaros E.; Turkbey, Baris; Saatci, Isil; Cekirge, Saruhan; Balkanci, Ferhun [Hacettepe University School of Medicine, Department of Radiology (Turkey)

2007-04-15

230

Improved image quality with Bayesian image processing in digital mammography  

Microsoft Academic Search

Recent developments in digital detectors have led to investigating the importance of grids in mammography. We propose to examine the use Bayesian Image Estimation (BIE) as a software means of removing scatter post acquisition and to compare this technique to a grid. BIE is an iterative, non- linear statistical estimation technique that reduces scatter content while improving CNR. Images of

Alan H. Baydush; Carey E. Floyd

2000-01-01

231

Hyperspectral laser-induced fluorescence imaging for assessing apple quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Chlorophyll fluorescence is useful for assessing fruit postharvest quality and condition. The objective of this research was to investigate the potential of using hyperspectral imaging to measure laser induced fluorescence for assessing apple fruit quality. A blue laser of 408 nm was used as an exci...

232

A study of the most important image quality measures  

Microsoft Academic Search

At the present time there are several statistical computer measures in existence that can be used to quantify the gain or loss of image quality. The challenge consists in guaranteeing that these measures may be reliable for a given goal. This paper presents a study and comparison between several commonly used quality measures (power signal to noise ratio, root mean

Rogerio M. Kinape; Mardson F. Amorim

2003-01-01

233

Novel Approach for 3-D Reconstruction of Coronary Arteries From Two Uncalibrated Angiographic Images  

Microsoft Academic Search

Three-dimensional reconstruction of vessels from digital X-ray angiographic images is a powerful technique that compensates for limitations in angiography. It can provide physicians with the ability to accurately inspect the complex arterial network and to quantitatively assess disease induced vascular alterations in three dimensions. In this paper, both the projection principle of single view angiography and mathematical modeling of two

Jian Yang; Yongtian Wang; Yue Liu; Songyuan Tang; Wufan Chen

2009-01-01

234

Diffusion weighted imaging reversibility in the brainstem following successful recanalization of acute basilar artery occlusion  

Microsoft Academic Search

Acute basilar artery occlusion (ABAO) is a devastating disease that can produce significant brainstem injury. Pretreatment diffusion weighted imaging (DWI) demonstrating extensive brainstem involvement has been shown to predict a poor outcome regardless of reperfusion. This case report describes a patient presenting with coma secondary to ABAO. MRI at presentation demonstrated significant DWI abnormality in the majority of the bilateral

Albert J Yoo; Reza Hakimelahi; Natalia S Rost; Pamela W Schaefer; Joshua A Hirsch; R Gilberto González; James D Rabinov

2010-01-01

235

Knowledge-Based 3D Segmentation and Reconstruction of Coronary Arteries Using CT Images.  

National Technical Information Service (NTIS)

An approach for the 3D segmentation and reconstruction of human left coronary arteries using angio-CT images is presented in this paper. Each voxel in the 3D dataset is assumed to belong to one of the three homogeneous regions: blood, myocardium, and lung...

Y. Yang A. Tannenbaum D. Giddens

2004-01-01

236

Objective quality assessment of tone-mapped images.  

PubMed

Tone-mapping operators (TMOs) that convert high dynamic range (HDR) to low dynamic range (LDR) images provide practically useful tools for the visualization of HDR images on standard LDR displays. Different TMOs create different tone-mapped images, and a natural question is which one has the best quality. Without an appropriate quality measure, different TMOs cannot be compared, and further improvement is directionless. Subjective rating may be a reliable evaluation method, but it is expensive and time consuming, and more importantly, is difficult to be embedded into optimization frameworks. Here we propose an objective quality assessment algorithm for tone-mapped images by combining: 1) a multiscale signal fidelity measure on the basis of a modified structural similarity index and 2) a naturalness measure on the basis of intensity statistics of natural images. Validations using independent subject-rated image databases show good correlations between subjective ranking score and the proposed tone-mapped image quality index (TMQI). Furthermore, we demonstrate the extended applications of TMQI using two examples-parameter tuning for TMOs and adaptive fusion of multiple tone-mapped images. PMID:23047872

Yeganeh, Hojatollah; Wang, Zhou

2012-10-02

237

USOFT: An Ultrasound Image Analysis Software for Beef Quality Research  

Microsoft Academic Search

Iowa State University has developed technology for an objective evaluation of beef quality by predicting the percentage of intramuscular fat (IMFAT) in live animals using ultrasound scans. For further research, development, and evaluation of this technology, a personal-computer based image analysis software, named USOFT, has been developed. USOFT is designed to facilitate analysis of images collected from a scan session.

Viren Amin; Doyle Wilson; Gene Rouse

1997-01-01

238

A Display Simulation Toolbox for Image Quality Evaluation  

Microsoft Academic Search

The output of image coding and rendering algorithms are presented on a diverse array of display devices. To evaluate these algorithms, image quality metrics should include more information about the spatial and chromatic properties of displays. To understand how to best incorporate such display information, we need a computational and empirical framework to characterize displays. Here we describe a set

Joyce Farrell; Gregory Ng; Xiaowei Ding; Kevin Larson; Brian Wandell

2008-01-01

239

Methods for improving image quality in whole body PET scanning  

Microsoft Academic Search

The authors discuss optimization of some of the scanning parameters for whole-body positron emission tomography (PET) imaging to achieve best possible image quality. The detection efficiency of the PET system can be improved by using more coincidence plane combinations in addition to the conventional direct and cross planes. The effect of acquiring an additional set of coincidence planes with a

Magnus Dahlbom; Dan-Chu Yu; Simon R. Cherry; Arion Chatziioannou; Edward J. Hoffman

1992-01-01

240

Raman chemical imaging technology for food safety and quality evaluation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Raman chemical imaging combines Raman spectroscopy and digital imaging to visualize composition and morphology of a target. This technique offers great potential for food safety and quality research. Most commercial Raman instruments perform measurement at microscopic level, and the spatial range ca...

241

Image Quality Assessment: From Error Measurement to Structural Similarity  

Microsoft Academic Search

Objective methods for assessing perceptual im- age quality traditionally attempt to quantify the visibility of errors (dierences) between a distorted image and a ref- erence image using a variety of known properties of the hu- man visual system. Under the assumption that human visual perception is highly adapted for extracting structural information from a scene, we introduce an alternative com-

Zhou Wang; Alan C. Bovik; Hamid R. Sheikh; Eero P. Simoncelli

2004-01-01

242

A patient image-based technique to assess the image quality of clinical chest radiographs  

NASA Astrophysics Data System (ADS)

Current clinical image quality assessment techniques mainly analyze image quality for the imaging system in terms of factors such as the capture system DQE and MTF, the exposure technique, and the particular image processing method and processing parameters. However, when assessing a clinical image, radiologists seldom refer to these factors, but rather examine several specific regions of the image to see whether the image is suitable for diagnosis. In this work, we developed a new strategy to learn and simulate radiologists' evaluation process on actual clinical chest images. Based on this strategy, a preliminary study was conducted on 254 digital chest radiographs (38 AP without grids, 35 AP with 6:1 ratio grids and 151 PA with 10:1 ratio grids). First, ten regional based perceptual qualities were summarized through an observer study. Each quality was characterized in terms of a physical quantity measured from the image, and as a first step, the three physical quantities in lung region were then implemented algorithmically. A pilot observer study was performed to verify the correlation between image perceptual qualities and physical quantitative qualities. The results demonstrated that our regional based metrics have promising performance for grading perceptual properties of chest radiographs.

Lin, Yuan; Samei, Ehsan; Luo, Hui; Dobbins, James T., III; McAdams, H. Page; Wang, Xiaohui; Sehnert, William J.; Barski, Lori; Foos, David H.

2011-03-01

243

Magnetic resonance imaging of perfusion using spin inversion of arterial water.  

PubMed Central

A technique has been developed for proton magnetic resonance imaging (MRI) of perfusion, using water as a freely diffusable tracer, and its application to the measurement of cerebral blood flow (CBF) in the rat is demonstrated. The method involves labeling the inflowing water proton spins in the arterial blood by inverting them continuously at the neck region and observing the effects of inversion on the intensity of brain MRI. Solution to the Bloch equations, modified to include the effects of flow, allows regional perfusion rates to be measured from an image with spin inversion, a control image, and a T1 image. Continuous spin inversion labeling the arterial blood water was accomplished, using principles of adiabatic fast passage by applying continuous-wave radiofrequency power in the presence of a magnetic field gradient in the direction of arterial flow. In the detection slice used to measure perfusion, whole brain CBF averaged 1.39 +/- 0.19 ml.g-1.min-1 (mean +/- SEM, n = 5). The technique's sensitivity to changes in CBF was measured by using graded hypercarbia, a condition that is known to increase brain perfusion. CBF vs. pCO2 data yield a best-fit straight line described by CBF (ml.g-1.min-1) = 0.052pCO2 (mm Hg) - 0.173, in excellent agreement with values in the literature. Finally, perfusion images of a freeze-injured rat brain have been obtained, demonstrating the technique's ability to detect regional abnormalities in perfusion. Images

Williams, D S; Detre, J A; Leigh, J S; Koretsky, A P

1992-01-01

244

Quantitative image quality evaluation of MR images using perceptual difference models  

PubMed Central

The authors are using a perceptual difference model (Case-PDM) to quantitatively evaluate image quality of the thousands of test images which can be created when optimizing fast magnetic resonance (MR) imaging strategies and reconstruction techniques. In this validation study, they compared human evaluation of MR images from multiple organs and from multiple image reconstruction algorithms to Case-PDM and similar models. The authors found that Case-PDM compared very favorably to human observers in double-stimulus continuous-quality scale and functional measurement theory studies over a large range of image quality. The Case-PDM threshold for nonperceptible differences in a 2-alternative forced choice study varied with the type of image under study, but was ?1.1 for diffuse image effects, providing a rule of thumb. Ordering the image quality evaluation models, we found in overall Case-PDM ? IDM (Sarnoff Corporation) ? SSIM [Wang et al. IEEE Trans. Image Process. 13, 600–612 (2004)] > mean squared error ? NR [Wang et al. (2004) (unpublished)] > DCTune (NASA) > IQM (MITRE Corporation). The authors conclude that Case-PDM is very useful in MR image evaluation but that one should probably restrict studies to similar images and similar processing, normally not a limitation in image reconstruction studies.

Miao, Jun; Huo, Donglai; Wilson, David L.

2008-01-01

245

Effect of optical aberrations on image quality and visual performance  

NASA Astrophysics Data System (ADS)

In addition to the effects of diffraction, retinal image quality in the human eye is degraded by optical aberrations. Although the paraxial geometric optics description of defocus consists of a simple blurred circle whose size determines the extent of blur, in reality the interactions between monochromatic and chromatic aberrations create a complex pattern of retinal image degradation. My thesis work hypothesizes that although both monochromatic and chromatic optical aberrations in general reduce image quality from best achievable, the underlying causes of retinal image quality degradation are characteristic of the nature of the aberration, its interactions with other aberrations as well as the composition of the stimulus. To establish a controlled methodology, a computational model of the retinal image with various levels of aberrations was used to create filters equivalent to those produced by real optical aberrations. Visual performance was measured psychophysically by using these special filters that separately modulated amplitude and phase in the retinal image. In order to include chromatic aberration into the optical interactions, a computational polychromatic model of the eye was created and validated. The model starts with monochromatic wavefront maps and derives a composite white light point-spread function whose quality was assessed using metrics of image quality. Finally, in order to assess the effectiveness of simultaneous multifocal intra-ocular lenses in correcting the eye's optical aberrations, a polychromatic computational model of a pseudophakic eye was constructed. This model incorporated the special chromatic properties unique to an eye corrected with hybrid refractive-diffractive optical elements. Results showed that normal optical aberrations reduced visual performance not only by reducing image contrast but also by altering the phase structure of the image. Longitudinal chromatic aberration had a greater effect on image quality in isolation than in the presence of monochromatic aberrations. Also, the diffractive optical element was found to improve polychromatic image quality in a pseudophakic eye by chromatic correction. My thesis work shows that in order to obtain maximal improvement in image quality, it is important to correct both monochromatic and chromatic aberrations.

Ravikumar, Sowmya

246

Surface Roughness Detection of Arteries via Texture Analysis of Ultrasound Images for Early Diagnosis of Atherosclerosis  

PubMed Central

There is a strong research interest in identifying the surface roughness of the carotid arterial inner wall via texture analysis for early diagnosis of atherosclerosis. The purpose of this study is to assess the efficacy of texture analysis methods for identifying arterial roughness in the early stage of atherosclerosis. Ultrasound images of common carotid arteries of 15 normal mice fed a normal diet and 28 apoE?/? mice fed a high-fat diet were recorded by a high-frequency ultrasound system (Vevo 2100, frequency: 40 MHz). Six different texture feature sets were extracted based on the following methods: first-order statistics, fractal dimension texture analysis, spatial gray level dependence matrix, gray level difference statistics, the neighborhood gray tone difference matrix, and the statistical feature matrix. Statistical analysis indicates that 11 of 19 texture features can be used to distinguish between normal and abnormal groups (p<0.05). When the 11 optimal features were used as inputs to a support vector machine classifier, we achieved over 89% accuracy, 87% sensitivity and 93% specificity. The accuracy, sensitivity and specificity for the k-nearest neighbor classifier were 73%, 75% and 70%, respectively. The results show that it is feasible to identify arterial surface roughness based on texture features extracted from ultrasound images of the carotid arterial wall. This method is shown to be useful for early detection and diagnosis of atherosclerosis.

Niu, Lili; Qian, Ming; Yang, Wei; Meng, Long; Xiao, Yang; Wong, Kelvin K. L.; Abbott, Derek; Liu, Xin; Zheng, Hairong

2013-01-01

247

Surface Roughness Detection of Arteries via Texture Analysis of Ultrasound Images for Early Diagnosis of Atherosclerosis.  

PubMed

There is a strong research interest in identifying the surface roughness of the carotid arterial inner wall via texture analysis for early diagnosis of atherosclerosis. The purpose of this study is to assess the efficacy of texture analysis methods for identifying arterial roughness in the early stage of atherosclerosis. Ultrasound images of common carotid arteries of 15 normal mice fed a normal diet and 28 apoE(-/-) mice fed a high-fat diet were recorded by a high-frequency ultrasound system (Vevo 2100, frequency: 40 MHz). Six different texture feature sets were extracted based on the following methods: first-order statistics, fractal dimension texture analysis, spatial gray level dependence matrix, gray level difference statistics, the neighborhood gray tone difference matrix, and the statistical feature matrix. Statistical analysis indicates that 11 of 19 texture features can be used to distinguish between normal and abnormal groups (p<0.05). When the 11 optimal features were used as inputs to a support vector machine classifier, we achieved over 89% accuracy, 87% sensitivity and 93% specificity. The accuracy, sensitivity and specificity for the k-nearest neighbor classifier were 73%, 75% and 70%, respectively. The results show that it is feasible to identify arterial surface roughness based on texture features extracted from ultrasound images of the carotid arterial wall. This method is shown to be useful for early detection and diagnosis of atherosclerosis. PMID:24146940

Niu, Lili; Qian, Ming; Yang, Wei; Meng, Long; Xiao, Yang; Wong, Kelvin K L; Abbott, Derek; Liu, Xin; Zheng, Hairong

2013-10-17

248

Quality evaluation of extra high quality images based on key assessment word  

NASA Astrophysics Data System (ADS)

An all encompassing goal of our research is to develop an extra high quality imaging system which is able to convey a high level artistic impression faithfully. We have defined a high order sensation as such a high level artistic impression, and it is supposed that the high order sensation is expressed by the combination of the psychological factor which can be described by plural assessment words. In order to pursue the quality factors that are important for the reproduction of the high order sensation, we have focused on the image quality evaluation of the extra high quality images using the assessment words considering the high order sensation. In this paper, we have obtained the hierarchical structure between the collected assessment words and the principles of European painting based on the conveyance model of the high order sensation, and we have determined a key assessment word 'plasticity' which is able to evaluate the reproduction of the high order sensation more accurately. The results of the subjective assessment experiments using the prototype of the developed extra high quality imaging system have shown that the obtained key assessment word 'plasticity' is the most appropriate assessment word to evaluate the image quality of the extra high quality images quasi-quantitatively.

Kameda, Masashi; Hayashi, Hidehiko; Akamatsu, Shigeru; Miyahara, Makoto M.

2001-06-01

249

Evaluation of patients with coronary artery disease. IQ-SPECT protocol in myocardial perfusion imaging: Preliminary results.  

PubMed

Quantification of myocardial perfusion scintigraphy is often performed to assist physicians in detecting coronary artery disease (CAD). Modern software and hardware packages provide improvements able to shorten scan time and/or reduce administered activity, without compromising image quality in radionuclide myocardial perfusion imaging (MPI). Recently, multifocal collimators were introduced with dedicated reconstruction software, named IQ-SPECT, able to shorten considerably scan time. The aim of our study was to compare this new protocol to the already validated standard ones. Patients, methods: We enrolled 43 patients with suspected or diagnosed CAD. All patients underwent a two-days protocol radionuclide myocardial perfusion scan at rest and after a standard stress test (exercise or dipyridamole) after administering 99mTc-tetrofosmin. Images were acquired on a 2-head gamma camera and reconstructed with attenuation correction. All the images were scored using a 17-segments model by three experienced physicians, blind to clinical data and to acquisition and processing modality. Results, conclusion: No significant differences were recorded in perfusion scores on paired t-test and Wilcoxon among the full-time images reconstructed with standard protocol or IQ-SPECT, both overall on a 17-segments evaluation and when considering different territories of distribution. MPI with IQ-SPECT protocol can be acquired at about a quarter scan time without disagreement compared to full time scan acquisition performed with standard protocols. PMID:23703588

Caobelli, F; Pizzocaro, C; Paghera, B; Guerra, U P

2013-05-24

250

Relationship of subjective ratings of image quality and observer performance  

NASA Astrophysics Data System (ADS)

The relationship between radiologists' perception of image quality and their actual performance was assessed. If the two variables are strongly correlated, the easier obtained perception of quality index might be used as a prerequisite test to determine if a ROC study is justified. One-hundred seventy cases were evaluated for the presence or absence of interstitial disease and nodules by nine readers using seven display modes. Each reader also assigned each image a mode- specific perceived quality rating using a 5-category ordinal scale. Average perceived quality was highest for conventional film. It was slightly poorer for the subsets of cases with interstitial disease and for cases classified independently as 'subtle.' Trend tests indicated a relationship between area under the ROC curves (Az) and perceived image quality for nodules. For interstitial disease, the relationship was weaker and of borderline statistical significance. The subjective image quality index was related to the area under the ROC curve, but the average difference between pairs of display modes was not a good predictor of difference in actual observer performances. A subjective quality index may have limited usefulness in screening differences between modalities prior to the performance of a ROC study.

Rockette, Howard E.; Johns, Christopher M.; Weissman, Jane L.; Holbert, J. Michael; Sumkin, Jules H.; King, Jill L.; Gur, David

1997-04-01

251

Trans-illuminated laser speckle imaging of collateral artery blood flow in ischemic mouse hindlimb.  

PubMed

ABSTRACT. The mouse ischemic hindlimb model is used widely for studying collateral artery growth (i.e., arteriogenesis) in response to increased shear stress. Nonetheless, precise measurements of regional shear stress changes along individual collateral arteries are lacking. Our goal is to develop and verify trans-illumination laser speckle flowmetry (LSF) for this purpose. Studies of defibrinated bovine blood flow through tubes embedded in tissue-mimicking phantoms indicate that trans-illumination LSF better maintains sensitivity with an increasing tissue depth when compared to epi-illumination, with an ?50% reduction in the exponential decay of the speckle velocity signal. Applying trans-illuminated LSF to the gracilis muscle collateral artery network in vivo yields both improved sensitivity and reduced noise when compared to epi-illumination. Trans-illuminated LSF images reveal regional differences in collateral artery blood velocity after femoral artery ligation and are used to measure an ?2-fold increase in the shear stress at the entrance regions to the muscle. We believe these represent the first direct measurements of regional shear stress changes in individual mouse collateral arteries. The ability to capture deeper vascular signals using a trans-illumination configuration for LSF may expand the current applications for LSF, which could have bearing on determining how shear stress magnitude and direction regulate arteriogenesis. PMID:24045691

Meisner, Joshua K; Niu, Jacqueline; Sumer, Suna; Price, Richard J

2013-09-01

252

Improved CT image quality using a new fully physical imaging chain  

Microsoft Academic Search

This paper describes the image quality improvements achieved by developing a new fully physical imaging chain. The key enablers for this imaging chain are a new scatter correction technique and an analytic computation of the beam hardening correction for each detector. The new scatter correction technique uses off-line Monte Carlo simulations to compute a large database of scatter kernels representative

Jens Wiegert; Matthias Bertram; Steffen Wiesner; Richard Thompson; Kevin M. Brown; Thomas Morton; Tsvi Katchalski; Yoad Yagil

2010-01-01

253

Method for image quality monitoring on digital television networks  

NASA Astrophysics Data System (ADS)

This paper presents a method designed to monitor image quality. The emphasis is given here to the monitoring in digital television broadcasting networks, in order for the providers to ensure a 'user-oriented' Quality of Service. Most objective image quality assessment methods are technically very difficult to apply in this context because of bandwidth limitations. We propose a parametric, reduced reference method that relies on the evaluation of characteristic coding and transmission impairments with a set of features. We show that quality can be predicted with a satisfying correlation to a subjective evaluation by the combination of several impairment features in an appropriate model. The method has been implemented and tested in a range of situations on simulated and real DVB networks. This allows to conclude on the usefulness of the approach and our future developments for quality of service monitoring in digital television.

Bretillon, Pierre; Baina, Jamal; Jourlin, Michel; Goudezeune, Gabriel

1999-11-01

254

Total Quality Can Help Your District's Image.  

ERIC Educational Resources Information Center

|Describes how educators in the Pearl River School District, Pearl River, New York, have implemented Total Quality Management (TQM) principles to evaluate and improve their effectiveness. Includes two charts that depict key indicators of financial and academic performance and a seven-year profile of the district's budget, enrollment, diploma rate,…

Cokeley, Sandra

1996-01-01

255

Arterial cross-section measurements from dual energy transvenous coronary angiography images  

SciTech Connect

The synchrotron based coronary angiography project at the National Synchrotron Light Source obtains images of coronary arteries using the digital subtraction technique after a distal venous injection of an iodine contrast agent. It allows two areal mass densities to be calculated from these images; one of the iodine and one of the water. Analysis procedures have been developed to arrive at these areal mass densities with corrections to the values being made for detector cross-talk and beam harmonics. From the iodine mass density distribution the relative arterial cross-section area is determined by a line integration across the arterial feature. Results will be given for an iodine tube phantom showing that the relative area of a feature whose lateral dimensions are smaller than the detector pixel resolution can be determined to a few percent. Also, results will be shown from a human image, showing the relative area of the right coronary artery mapped through a region of a previous stenosis subsequently treated by balloon angioplasty. Finally, limitation of the technique and plans to validate and improve the analysis will be discussed.

Chapman, D. [Brookhaven National Laboratory, Upton, NY (United States); Schulze, C. [ESRF, Grenoble (France)

1994-05-01

256

Vertebral artery dissection diagnosed by non-invasive magnetic resonance imaging.  

PubMed

A forty-year-old man developed right-sided neck discomfort whilst cycling to work. On admission to hospital he was found to have signs of bilateral cerebellar dysfunction. Magnetic resonance imaging of the brain demonstrated bilateral areas of cerebellar infarction. Doppler ultrasound of the vertebral arteries was abnormal and non-invasive gradient echo time of flight magnetic resonance angiography confirmed the clinical diagnosis of vertebral artery dissection. The patient was anticoagulated for a period of three months and made a full recovery. PMID:11060916

Cawood, T J; Dyker, A G; Adams, F G

2000-08-01

257

The influence of software filtering in digital mammography image quality  

NASA Astrophysics Data System (ADS)

Breast cancer is one of the most frequently diagnosed cancers among women. Several techniques have been developed to help in the early detection of breast cancer such as conventional and digital x-ray mammography, positron and single-photon emission mammography, etc. A key advantage in digital mammography is that images can be manipulated as simple computer image files. Thus non-dedicated commercially available image manipulation software can be employed to process and store the images. The image processing tools of the Photoshop (CS 2) software usually incorporate digital filters which may be used to reduce image noise, enhance contrast and increase spatial resolution. However, improving an image quality parameter may result in degradation of another. The aim of this work was to investigate the influence of three sharpening filters, named hereafter sharpen, sharpen more and sharpen edges on image resolution and noise. Image resolution was assessed by means of the Modulation Transfer Function (MTF).In conclusion it was found that the correct use of commercial non-dedicated software on digital mammograms may improve some aspects of image quality.

Michail, C.; Spyropoulou, V.; Kalyvas, N.; Valais, I.; Dimitropoulos, N.; Fountos, G.; Kandarakis, I.; Panayiotakis, G.

2009-05-01

258

Quantitative helmet-mounted display system image quality model  

NASA Astrophysics Data System (ADS)

Honeywell has developed a quantitative image quality model for the Helmet Mounted Display (HMD) electro-optical systems that will predict the optical performance and image quality of a given system configuration. The linear systems model includes modules for the image intensifier objective, image intensifier tube, fiber optic faceplates and tapers, charge coupled device (CCD) camera, liquid crystal display (LCD) or CRT image source, relay optics, electronic filtering and preprocessing, and a perception model for the eye. Sine wave and square wave system response are predicted via modulation transform function (MTF) calculations as well as the maximum resolution and a measurement of just noticeable differences (jnd's) as perceived by the human eye. The model will allow the system designer to quickly and inexpensively evaluate complex systems tradeoffs and modifications to advanced HMD systems.

Nelson, Scott A.; Cox, J. Allen

1992-10-01

259

Characterization of the image quality in neutron radioscopy  

NASA Astrophysics Data System (ADS)

Neutron radioscopy, or dynamic neutron radiography, is a non-destructive testing method, which has made big steps in the last years. Depending on the neutron flux, the object and the detector, for single events a time resolution down to a few milliseconds is possible. In the case of repetitive processes the object can be synchronized with the detector and better statistics in the image can be reached by adding radiographies of the same phase with a time resolution down to 100 ?s. By stepwise delaying the trigger signal a radiography movie can be composed. Radiography images of a combustion engine and an injection nozzle were evaluated quantitatively by different methods trying to characterize the image quality of an imaging system. The main factors which influence the image quality are listed and discussed.

Brunner, J.; Engelhardt, M.; Frei, G.; Gildemeister, A.; Lehmann, E.; Hillenbach, A.; Schillinger, B.

2005-04-01

260

Coolant quality for magnetic resonance imaging systems  

Microsoft Academic Search

As radiologists demand increased power, speed and duty cycle from their magnetic resonance imaging (MRI) systems, thermal management of the gradient sub-system becomes more challenging. A heat exchanger in the MRI system cools heat-generating components by pumping water through hollow copper tubing, which also carries high electrical currents. Water is used as a coolant because of its high specific heat

Julie Wong; Garron K Morris

2008-01-01

261

Developing Matlab scripts for image analysis and quality assessment  

NASA Astrophysics Data System (ADS)

Image processing is a very helpful tool in many fields of modern sciences that involve digital imaging examination and interpretation. Processed images however, often need to be correlated with the original image, in order to ensure that the resulting image fulfills its purpose. Aside from the visual examination, which is mandatory, image quality indices (such as correlation coefficient, entropy and others) are very useful, when deciding which processed image is the most satisfactory. For this reason, a single program (script) was written in Matlab language, which automatically calculates eight indices by utilizing eight respective functions (independent function scripts). The program was tested in both fused hyperspectral (Hyperion-ALI) and multispectral (ALI, Landsat) imagery and proved to be efficient. Indices were found to be in agreement with visual examination and statistical observations.

Vaiopoulos, A. D.

2011-10-01

262

A model utilizing artificial neural network for perceptual image quality assessment in image compression algorithms  

NASA Astrophysics Data System (ADS)

The demand of an accurate objective image quality assessment tool is important in modern multimedia systems. Image coding algorithms introduce highly structured coding artifacts and distortions. In this paper, we present a novel approach to predict the perceived image quality. Properties of the Human Visual System (HVS) were exploited to select a set of suitable metrics. These metrics are extracted while comparing the reference and distorted image. Mutual Information (MI) and Principal Component Analysis (PCA) were used to obtain an optimal set of objective features that best describe the perceived image quality in respect to subjective scores from human observers. The impairment feature vector is forwarded to the Artificial Neural Network (ANN) where the features are combined and the predicted quality score is computed. Parameters of the ANN are adjusted using Mean Opinion Scores (MOS) obtained from the group of assessors. It is shown that the proposed image quality assessment model can achieve high correlation with the subjective image quality ratings. Possible incorporation of the model into a perceptual image-coding algorithm is proposed. Such a system is capable to ensure that only visually important information is encoded and consequently that the required communication bandwidth is minimized.

Fliegel, Karel

2006-09-01

263

Body image and quality of life in a Spanish population  

PubMed Central

Purpose The aim of the current study was to analyze the psychometric properties, factor structure, and internal consistency of the Spanish version of the Body Image Quality of Life Inventory (BIQLI-SP) as well as its test–retest reliability. Further objectives were to analyze different relationships with key dimensions of psychosocial functioning (ie, self-esteem, presence of psychopathological symptoms, eating and body image-related problems, and perceived stress) and to evaluate differences in body image quality of life due to gender. Patients and methods The sample comprised 417 students without any psychiatric history, recruited from the Pablo de Olavide University and the University of Seville. There were 140 men (33.57%) and 277 women (66.43%), and the mean age was 21.62 years (standard deviation = 5.12). After obtaining informed consent from all participants, the following questionnaires were administered: BIQLI, Eating Disorder Inventory-2 (EDI-2), Perceived Stress Questionnaire (PSQ), Self-Esteem Scale (SES), and Symptom Checklist-90-Revised (SCL-90-R). Results The BIQLI-SP shows adequate psychometric properties, and it may be useful to determine the body image quality of life in different physical conditions. A more positive body image quality of life is associated with better self-esteem, better psychological wellbeing, and fewer eating-related dysfunctional attitudes, this being more evident among women. Conclusion The BIQLI-SP may be useful to determine the body image quality of life in different contexts with regard to dermatology, cosmetic and reconstructive surgery, and endocrinology, among others. In these fields of study, a new trend has emerged to assess body image-related quality of life.

Lobera, Ignacio Jauregui; Rios, Patricia Bolanos

2011-01-01

264

Evaluation of image quality in computed radiography based mammography systems  

NASA Astrophysics Data System (ADS)

Mammography is the most widely accepted procedure for the early detection of breast cancer and Computed Radiography (CR) is a cost-effective technology for digital mammography. We have demonstrated that CR mammography image quality is viable for Digital Mammography. The image quality of mammograms acquired using Computed Radiography technology was evaluated using the Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE). The measurements were made using a 28 kVp beam (RQA M-II) using 2 mm of Al as a filter and a target/filter combination of Mo/Mo. The acquired image bit depth was 16 bits and the pixel pitch for scanning was 50 microns. A Step-Wedge phantom (to measure the Contrast-to-noise ratio (CNR)) and the CDMAM 3.4 Contrast Detail phantom were also used to assess the image quality. The CNR values were observed at varying thickness of PMMA. The CDMAM 3.4 phantom results were plotted and compared to the EUREF acceptable and achievable values. The effect on image quality was measured using the physics metrics. A lower DQE was observed even with a higher MTF. This could be possibly due to a higher noise component present due to the way the scanner was configured. The CDMAM phantom scores demonstrated a contrast-detail comparable to the EUREF values. A cost-effective CR machine was optimized for high-resolution and high-contrast imaging.

Singh, Abhinav; Bhwaria, Vipin; Valentino, Daniel J.

2011-03-01

265

Image quality with current adaptive optics instruments  

NASA Astrophysics Data System (ADS)

From natural guide star adaptive optics data, we study the properties of the on-axis point spread function and discuss the performance of adaptive optics images. A close relation between the full width half maximum and the Strehl ratio is shown. The ultimate exploitation of adaptive optics images requires the deconvolution and therefore the calibration of the point spread function. This calibration is commonly made by sequentially observing a point source close to the astronomical target. In the partial correction regime, the calibration mismatch is the main source of noise or bias in the deconvolution process and it is mainly induced by the varying seeing conditions. Complementary techniques like near-sighted deconvolution, speckle and rebinning are briefly reviewed. Based on observations made at ESO and SOR.

Tessier, E.

1997-11-01

266

Skeletal muscle microvascular flow in progressive peripheral artery disease: Assessment with continuous arterial spin-labeling perfusion magnetic resonance imaging  

PubMed Central

Structured Abstract Objectives We present the novel application of continuous arterial spin-labeling (CASL) magnetic resonance imaging (MRI) for the measurement of calf muscle perfusion in subjects with progressive peripheral arterial disease (PAD). Background PAD is largely considered to be a disease of conduit vessels. The impact of PAD upon microvascular flow in the end-organ, muscle, remains unknown. CASL is a noninvasive MRI method capable of measuring microvascular flow and may assist in our understanding of the impact of PAD upon the microvasculature. Methods Forty subjects with varying degrees of PAD and seventeen age-matched PAD-free subjects were recruited and underwent measurement of the ankle-to-brachial index (ABI) and CASL. Peak hyperemic flow (PHF) and time-to-peak (TTP) were computed and assessed as a function of ABI and calf muscle group. Results ABI dependence was found in both PHF (p = 0.04) and TTP (p < 10?4). While TTP responded almost immediately to increasing PAD severity, PHF was preserved until subjects fell into cateogory-2 and even longer in the soleus muscle. Conclusions CASL flow measurements correlate with disease state as measured by ABI, and also demonstrate preserved microvascular flow reserve in the presence of early to intermediate vascular disease.

Wen-Chau, Wu; Mohler, Emile; Ratcliffe, Sarah J.; Wehrli, Felix W.; Detre, John A.; Floyd, Thomas F

2009-01-01

267

Optimizing radiation dose and image quality  

Microsoft Academic Search

Radiation exposure is a critical issue in multidetector CT (MDCT) particularly since fast MDCT scanners have become widely\\u000a available, and the method has been proposed as a noninvasive diagnostic tool for an increasing number of clinical applications.\\u000a Additional features of MDCT imaging affecting individual dose are related to the inappropriate use of scanners caused by practices\\u000a such as scanning beyond

Carlo Catalano; Marco Francone; Adriano Ascarelli; Matteo Mangia; Ilaria Iacucci; Roberto Passariello

2007-01-01

268

Automatic localization of intimal and adventitial carotid artery layers with noninvasive ultrasound: a novel algorithm providing scan quality control.  

PubMed

Transcutaneous ultrasound measurements of common carotid artery (CCA) diameter and intima-media thickness (IMT) give insight on arterial dynamics and anatomy, both correlating well with atherosclerosis and risk of cardiovascular disease. We propose a novel automatic algorithm to estimate CCA diameter and IMT in ultrasound (US) images, based on separate analysis of anterior and posterior CCA walls and able to distinguish internal (intima-intima) and external (adventitia-adventitia) diameter. The method combines off-line signal- and image-processing techniques to accommodate echo images acquired at a frame rate of 30 Hz and composed directly from RF data, circumventing digital video-grabbing. Segmentation consists of automatic CCA recognition, followed by adventitial delineation performed with a sustain-attack filter with exponentially decaying reference functions. Intimal delineation is then based on the multiscale anisotropic barycenter (MAB), which is an extension of a known delineation method involving the "first order absolute central moment" of the echo amplitude. An automatic measure of the quality of the US beam incidence for each wall is superimosed on the CCA contour overlays for visual feedback. Validation is carried out on 36 US CCA acquisitions from 12 healthy volunteers, as well as on synthetic US images. Results indicate good accuracy on synthetic US images (within 1.3% for diameter and 3% for IMT). The in vivo intra-recording beat-to-beat variations are on average lower than 50 microm for external diameter and IMT, and lower than 100 microm for internal diameter. A comparison with a commercial device (ART.LAB system) shows that the proposed algorithm performs better in terms of inter-recording precision. The beam incidence control significantly improves the repeatability of IMT estimates, and motivates sonographers actively to maintain a proper scan plane throughout the acquisition to minimize the incidence of confounding factors. The method is clinically viable, providing robust estimates of CCA internal and external diameter and IMT waveforms for both CCA walls, even at a low B-mode update rate of 30 Hz. PMID:20172448

Rossi, Alessandro C; Brands, Peter J; Hoeks, Arnold P G

2010-03-01

269

Utility of Perfusion-Weighted CT Imaging in Acute Middle Cerebral Artery Stroke Treated With Intra-Arterial Thrombolysis Prediction of Final Infarct Volume and Clinical Outcome  

Microsoft Academic Search

Background and Purpose—The goal of this study was to evaluate the utility of perfusion-weighted CT (PWCT) in predicting final infarct volume and clinical outcome in patients with acute middle cerebral artery (MCA) stroke. Methods—Twenty-two consecutive patients with MCA stem occlusion who underwent intra-arterial thrombolysis within 6 hours of stroke onset had noncontrast CT and CT angiography with whole-brain PWCT imaging

Michael H. Lev; Alan Z. Segal; Jeffery Farkas; Syeda T. Hossain; Christopher Putman; George J. Hunter; Ronald Budzik; Gordon J. Harris; Ferdinando S. Buonanno; Mustapha A. Ezzeddine; Yuchiao Chang; Walter J. Koroshetz; R. Gilberto Gonzalez; Lee H. Schwamm

270

Relationship between functional exercise capacity and general quality of life in nonsurgical patients with lower-extremity peripheral arterial disease  

Microsoft Academic Search

The purpose of this study was to examine the relationship between functional exercise capacity and general quality of life in patients with lower-extremity peripheral arterial disease (PAD) whose conditions are managed without surgical intervention and to establish new ways of measuring functional exercise capacity and general quality of life in this population. This descriptive survey examined 29 nonsurgical patients with

H. Charles Bauman; Heather M. Arthur

1997-01-01

271

The effect of treatment on health-related quality of life in patients with hypertension and renal artery stenosis  

Microsoft Academic Search

The quality of life in patients with hypertension is considered to be impaired mainly by side effects of antihypertensive drug therapy. Since balloon angioplasty for renal artery stenosis has a medication-sparing effect, it may lead to an improvement in quality of life. The objective of the study is to compare the effect of antihypertensive drug therapy and balloon angioplasty on

P Krijnen; B C van Jaarsveld; M G M Hunink; J D F Habbema

2005-01-01

272

EFFECT OF A HEALTH EDUCATION PROGRAM ON QUALITY OF LIFE IN PATIENTS UNDERGOING CORONARY ARTERY BYPASS SURGERY  

Microsoft Academic Search

Quality of life has emerged as an important concept and outcome in health and health care. This study was performed to evaluate the ability of the health education program to improve quality of life of patients with coronary artery bypass graft surgery (CABG). In pre operation period, 70 patients were randomized in two groups, experimental and control group (35 patients

G. Babaee; M. Keshavarz; A. Hidarnia; M. Shayegan

273

Knowledge-based 3D segmentation and reconstruction of coronary arteries using CT images.  

PubMed

An approach for the 3D segmentation and reconstruction of human left coronary arteries using angio-CT images is presented in This work. Each voxel in the 3D dataset is assumed to belong to one of the three homogeneous regions: blood, myocardium, and lung. A priori knowledge of the regions is introduced via Bayes' rule. Posterior probabilities obtained using Bayes' rule are anisotropically smoothed, and the 3D segmentation is obtained via MAP classifications of the smoothed posteriors. An active contour model is then applied to extract the coronary arteries from the rest of the volumetric data with subvoxel accuracy. The geometric model of the left coronary arteries obtained in this work may be used to provide accurate boundary conditions for hemodynamic simulations, or to provide objective measurements of clinically relevant parameters such as lumen sizes in a 3D sense. PMID:17272022

Yang, Yan; Tannenbaum, Allen; Giddens, Don; Coulter, Wallace

2004-01-01

274

Objective image quality measurement by local spatial?frequency wavelet analysis  

Microsoft Academic Search

An essential determinant of the value of surrogate digital images is their quality. Image quality measurement has become crucial for most image processing applications. Over the past years, there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image

G. Y. Luo

2006-01-01

275

Noninvasive determination of local wavespeed and distensibility of the femoral artery by comb-excited Fourier velocity-encoded magnetic resonance imaging: Measurements on athletic and nonathletic human subjects  

Microsoft Academic Search

Summary The local distensibility of arteries is of interest because distensibility varies from artery to artery, may be altered by disease to different extents in different arteries, and may be modified by physiological or pharmacological means. Using magnetic resonance imaging (MRI) we have measured local arterial wavespeed in the femoral artery in healthy human subjects and calculated local arterial distensibility.

Maria Tarnawski; Gerard Cybulski; Denis Doorly; Charles Dumoulin; Robert Darrow; Colin Caro

1994-01-01

276

Intravascular Ultrasound Imaging of Peripheral Arteries as an Adjunct to Balloon Angioplasty and Atherectomy  

SciTech Connect

This article reviews many of the applications of intravascular ultrasound (US) imaging for peripheral arterial diseases. In vitro studies demonstrate an excellent correlation between ultrasound measurements of lumen and plaque crossectional area compared with histologic sections. In vivo clinical studies reveal the enhanced diagnostic capabilities of this technology compared with angiography. Intravascular US imaging can provide valuable information on the degree, eccentricity, and histologic type of stenosis before intervention, and on the morphological changes in the arterial wall and the extent of excision after intervention. Intravascular US may also serve as a superior index for gauging the diameter of balloon, stent, laser probe, and/or atherectomy catheter appropriate for a proposed intervention. Significant new insights into the mechanisms of balloon angioplasty and atherectomy have been established by intravascular US findings. Intravascular US imaging has been shown to be a more accurate method than angiography for determining the cross-sectional area of the arterial lumen, and for assessing severity of stenosis. Quantitative assessment of the luminal cross-sectional area after the balloon dilatation should be more accurate than angiography as intimal tears or dissections produced by the dilatation may not be accurately evaluated with angiography. At the present time, intravascular US is still a controversial imaging technique. Outcome studies are currently being organized to assess the clinical value and cost effectiveness of intravascular ultrasound in the context of these interventional procedures.

Korogi, Yukunori; Hirai, Toshinori; Takahashi, Mutsumasa [Department of Radiology, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto 860 (Japan)

1996-11-15

277

Sexuality and Body Image After Uterine Artery Embolization and Hysterectomy in the Treatment of Uterine Fibroids: A Randomized Comparison  

PubMed Central

In this paper the effect of uterine artery embolization (UAE) on sexual functioning and body image is investigated in a randomized comparison to hysterectomy for symptomatic uterine fibroids. The EMbolization versus hysterectoMY (EMMY) trial is a randomized controlled study, conducted at 28 Dutch hospitals. Patients were allocated hysterectomy (n = 89) or UAE (n = 88). Two validated questionnaires (the Sexual Activity Questionnaire [SAQ] and the Body Image Scale [BIS]) were completed by all patients at baseline, 6 weeks, and 6, 12, 18, and 24 months after treatment. Repeated measurements on SAQ scores revealed no differences between the groups. There was a trend toward improved sexual function in both groups at 2 years, although this failed to reach statistical significance except for the dimensions discomfort and habit in the UAE arm. Overall quality of sexual life deteriorated in a minority of cases at all time points, with no significant differences between the groups (at 24 months: UAE, 29.3%, versus hysterectomy, 23.5%; p = 0.32). At 24 months the BIS score had improved in both groups compared to baseline, but the change was only significant in the UAE group (p = 0.009). In conclusion, at 24 months no differences in sexuality and body image were observed between the UAE and the hysterectomy group. On average, both after UAE and hysterectomy sexual functioning and body image scores improved, but significantly so only after UAE.

Volkers, Nicole A.; Bartholomeus, Wouter; de Blok, Sjoerd; Birnie, Erwin; Reekers, Jim A.; Ankum, Willem M.

2007-01-01

278

Sexuality and Body Image After Uterine Artery Embolization and Hysterectomy in the Treatment of Uterine Fibroids: A Randomized Comparison  

SciTech Connect

In this paper the effect of uterine artery embolization (UAE) on sexual functioning and body image is investigated in a randomized comparison to hysterectomy for symptomatic uterine fibroids. The EMbolization versus hysterectoMY (EMMY) trial is a randomized controlled study, conducted at 28 Dutch hospitals. Patients were allocated hysterectomy (n = 89) or UAE (n 88). Two validated questionnaires (the Sexual Activity Questionnaire [SAQ] and the Body Image Scale [BIS]) were completed by all patients at baseline, 6 weeks, and 6, 12, 18, and 24 months after treatment. Repeated measurements on SAQ scores revealed no differences between the groups. There was a trend toward improved sexual function in both groups at 2 years, although this failed to reach statistical significance except for the dimensions discomfort and habit in the UAE arm. Overall quality of sexual life deteriorated in a minority of cases at all time points, with no significant differences between the groups (at 24 months: UAE, 29.3%, versus hysterectomy, 23.5%; p = 0.32). At 24 months the BIS score had improved in both groups compared to baseline, but the change was only significant in the UAE group (p = 0.009). In conclusion, at 24 months no differences in sexuality and body image were observed between the UAE and the hysterectomy group. On average, both after UAE and hysterectomy sexual functioning and body image scores improved, but significantly so only after UAE.

Hehenkamp, Wouter J. K. [Academic Medical Centre Amsterdam, Department of Gynaecology (Netherlands)], E-mail: w.j.k.hehenkamp@amc.uva.nl; Volkers, Nicole A. [Academic Medical Centre Amsterdam, Department of Radiology (Netherlands); Bartholomeus, Wouter [Academic Medical Centre Amsterdam, Faculty of Medicine (Netherlands); Blok, Sjoerd de [Onze Lieve Vrouwe Gasthuis, Amsterdam, Department of Gynaecology (Netherlands); Birnie, Erwin [Academic Medical Centre Amsterdam, Public Health Epidemiology (Netherlands); Reekers, Jim A. [Academic Medical Centre Amsterdam, Department of Radiology (Netherlands); Ankum, Willem M. [Academic Medical Centre Amsterdam, Department of Gynaecology (Netherlands)

2007-09-15

279

In vivo high-resolution structural imaging of large arteries in small rodents using two-photon laser scanning microscopy  

Microsoft Academic Search

In vivo (molecular) imaging of the vessel wall of large arteries at subcellular resolution is crucial for unraveling vascular pathophysiology. We previously showed the applicability of two-photon laser scanning microscopy (TPLSM) in mounted arteries ex vivo. However, in vivo TPLSM has thus far suffered from in-frame and between-frame motion artifacts due to arterial movement with cardiac and respiratory activity. Now,

Remco T. A. Megens; Sietze Reitsma; Lenneke Prinzen; Mirjam G. A. Oude Egbrink; Wim Engels; Peter J. A. Leenders; Ellen J. L. Brunenberg; Koen D. Reesink; Ben J. A. Janssen; Bart M. Ter Haar Romeny; Dick W. Slaaf; Marc A. M. J. van Zandvoort

2010-01-01

280

Fast Tomography: A Study Of Image Quality  

SciTech Connect

We present tomographic slices of fast X-ray computed microtomography, focusing on one hand on the comparison of scans with identical scan time but varying experimental settings, on the other hand on comparing scans with total scan times that are two orders of magnitude apart. We show that streaks in the Fourier-space of the transformed images appear when the number of projections is reduced. These streaks exhibit spacing by the same angle as the one that is covered by the sample during the exposure time of one projection. Further a method for the estimation of information loss in fast scans is presented.

Waske, A.; Rahn, H.; Odenbach, S. [Chair of Magnetofluiddynamics, Institute of Fluid Dynamics, TU Dresden, George-Baehr-Str. 3, 01062 Dresden (Germany)

2010-04-06

281

Lens designs with extreme image quality features  

NASA Astrophysics Data System (ADS)

In order to best assess the importance of new technologies to optical design, it is useful to consider what the limits are to what can be done with `old' technologies. That may show where something new is needed to overcome the limitations of existing optical designs. This article will give a survey of some remarkable high-performance designs, some of which are extremely simple, and most of which only use technology that has already been around for decades. Each of these designs has some limitation that would be nice to overcome. One new technology that will probably revolutionize optical design will be curved surfaces on image chips.

Shafer, David

2013-02-01

282

Investigation of perceptual attributes for mobile display image quality  

NASA Astrophysics Data System (ADS)

Large-scale psychophysical experiments are carried out on two types of mobile displays to evaluate the perceived image quality (IQ). Eight perceptual attributes, i.e., naturalness, colorfulness, brightness, contrast, sharpness, clearness, preference, and overall IQ, are visually assessed via categorical judgment method for various application types of test images, which were manipulated by different methods. Their correlations are deeply discussed, and further factor analysis revealed the two essential components to describe the overall IQ, i.e., the component of image detail aspect and the component of color information aspect. Clearness and naturalness are regarded as two principal factors for natural scene images, whereas clearness and colorfulness were selected as key attributes affecting the overall IQ for other application types of images. Accordingly, based on these selected attributes, two kinds of empirical models are built to predict the overall IQ of mobile displays for different application types of images.

Gong, Rui; Xu, Haisong; Wang, Qing; Wang, Zhehong; Li, Haifeng

2013-08-01

283

Determination of the quantitative thallium imaging variables that optimize detection of coronary artery disease  

SciTech Connect

Although quantification of exercise thallium images has been previously reported, the relative value of different imaging variables for detection of coronary artery disease has not been analyzed in a large group of patients with cardiac catheterization data. Regional initial thallium uptake, redistribution and clearance on thallium study were measured in 325 patients also undergoing cardiac catheterization (281 patients with and 44 patients without coronary artery disease). Normal values were defined in 55 other clinically normal subjects. When five myocardial segments were analyzed in each view, the respective values for sensitivity and specificity were 95 and 50% for initial thallium uptake, 60 and 87% for redistribution and 74 and 66% for clearance. Initial thallium uptake was the most sensitive but least specific (p less than 0.001), whereas redistribution was the least sensitive and most specific (p less than 0.001). Using stepwise logistic regression analysis, the best correlate of coronary artery disease was initial thallium uptake. Addition of redistribution to a mathematical model of the probability of coronary artery disease did not alter sensitivity, but increased specificity from 50 to 70% (p less than 0.001). Once initial uptake and redistribution were considered, myocardial thallium clearance provided no additional improvement in the correlation. Excluding the two basal segments in each view from the analysis increased the specificity from 70 to 80% (p less than 0.001) without affecting sensitivity. Of the 15 patients (5%) with coronary disease not detected using this approach, none had left main disease and 10 (67%) had one vessel disease. A combination of variables derived from quantification of exercise thallium images provides a superior sensitivity and specificity for the detection of coronary artery disease compared with the use of a single variable.

Kaul, S.; Boucher, C.A.; Newell, J.B.; Chesler, D.A.; Greenberg, J.M.; Okada, R.D.; Strauss, H.W.; Dinsmore, R.E.; Pohost, G.M.

1986-03-01

284

NOTE: Measurement of hepatic arterial flow using phase contrast magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Flow measurements through the hepatic artery were performed using retrospectively gated phase contrast magnetic resonance imaging in 22 patients. In 13 patients where three consecutive measurements of hepatic arterial flow were made, the average intra-subject coefficient of variation was 10.0% (range 2.7-21.2%). The measured blood flow was significantly higher in the eight patients where it was expected that there would be a high hepatic arterial flow compared to nine patients where it was expected that there would be a normal hepatic arterial flow based on the patients pathology (435 ml min-1 versus 235 ml min-1, difference = 200 ml min-1, 95% confidence intervals on difference = 73-327 ml min-1, p < 0.05, independent t-test). Phase correction was performed by fitting a quadratic surface to stationary tissue. The average blood flow correction due to phase correction was 6.3% (20.9 ml min-1) with a range of 0.8% (1 ml min-1) to 15.0% (70.0 ml min-1). Flow measurements through the hepatic artery can be performed, but care must be taken to minimize pixel size and localize accurately.

Wilson, Daniel J.; Ridgway, John P.; Evans, J. Anthony; Robinson, Philip

2009-10-01

285

Are image quality metrics adequate to evaluate the quality of geometric objects?  

NASA Astrophysics Data System (ADS)

Geometric objects are often represented by many millions of triangles or polygons, which limits the ease with which they can be transmitted and displayed electronically. This has lead to the development of many algorithms for simplifying geometric models, and to the recognition that metrics are required to evaluate their success. The goal is to create computer graphic renderings of the object that do not appear to be degraded to a human observer. The perceptual evaluation of simplified objects is a new topic. One approach has been to sue image-based metrics to predict the perceived degradation of simplified 3D models. Since that 2D images of 3D objects can have significantly different perceived quality, depending on the direction of the illumination, 2D measures of image quality may not adequately capture the perceived quality of 3D objects. To address this question, we conducted experiments in which we explicitly compared the perceived quality of animated 3D objects and their corresponding 2D still image projections. Our results suggest that 2D judgements do not provide a good predictor of 3D image quality, and identify a need to develop 'object quality metrics.'

Rogowitz, Bernice E.; Rushmeier, Holly E.

2001-06-01

286

High quality image compression for rockets and satellites  

NASA Astrophysics Data System (ADS)

Installed communication systems for the more recent imagery rockets and satellites generally do not have sufficient data link bandwidth to allow imagery transmission. High quality image compression can alleviate this problem since 5 to 10 times more image data can be transmitted over existing communication systems. Researchers at Utah State University have developed a high quality image compression algorithm which has been denoted as statistically lossless. This algorithm combines the good features of the well known vector quantization (VQ) compression and lossless compression. Results are presented in this paper in which different scientific imagery collection systems have been processed using the algorithm. In order to implement this algorithm, a CMOS VLSI chip has been produced which allows a VQ compression system to process 512 x 512 pixel images at a rate of 30 frames per second.

Harris, Richard W.; Budge, Scott E.; Israelson, Paul D.; Sojka, Jan J.; Roark, William

287

Arterial input function derived from pairwise correlations between PET-image voxels.  

PubMed

A metabolite corrected arterial input function is a prerequisite for quantification of positron emission tomography (PET) data by compartmental analysis. This quantitative approach is also necessary for radioligands without suitable reference regions in brain. The measurement is laborious and requires cannulation of a peripheral artery, a procedure that can be associated with patient discomfort and potential adverse events. A non invasive procedure for obtaining the arterial input function is thus preferable. In this study, we present a novel method to obtain image-derived input functions (IDIFs). The method is based on calculation of the Pearson correlation coefficient between the time-activity curves of voxel pairs in the PET image to localize voxels displaying blood-like behavior. The method was evaluated using data obtained in human studies with the radioligands [(11)C]flumazenil and [(11)C]AZ10419369, and its performance was compared with three previously published methods. The distribution volumes (VT) obtained using IDIFs were compared with those obtained using traditional arterial measurements. Overall, the agreement in VT was good (?3% difference) for input functions obtained using the pairwise correlation approach. This approach performed similarly or even better than the other methods, and could be considered in applied clinical studies. Applications to other radioligands are needed for further verification. PMID:23571279

Schain, Martin; Benjaminsson, Simon; Varnäs, Katarina; Forsberg, Anton; Halldin, Christer; Lansner, Anders; Farde, Lars; Varrone, Andrea

2013-04-10

288

Magnetic resonance imaging of peripheral vascular disease. The state of the artery.  

PubMed

Peripheral vascular disease is a term often used to describe the manifestation of atherosclerosis below the bifurcation of the abdominal aorta. Peripheral atherosclerosis is a major cause of morbidity in the developed countries and 2% of adults in late middle age have intermittent claudication, which is severe enough in some patients to warrant hospital admission. The disease produces problems either by reducing blood flow or by the release of emboli from ulcerated plaques. The morphology and composition of arterial segments containing atheroma is of considerable importance. Plaques of different morphology have different effects on the arterial wall, such as the potential for thrombosis and the effect of arterial spasm. The lipid content may also affect the propensity for fissuring, ulceration, and thrombosis. In addition to discrete atherotic lesions, a localized and generalized sclerosis occurs. Sclerosis, or stiffness, can be demonstrated in experimental disease in animals and in man, and regression leads to reduced stiffness. Magnetic resonance imaging promises a comprehensive assessment of peripheral atherosclerosis noninvasively and without the use of ionizing radiation. Atheroma can be imaged directly, its size can be measured, its shape can be described, its lipid content can be assessed, and its effects upon vascular hemodynamics can be studied. In addition, arterial compliance, pulse wave velocity, and the pattern of flow within the vessel can be studied. It is thus a potential tool not only for the detection of disease but also for studying its natural history, risk factors, and the effects of pharmacological or surgical interventions. PMID:10147795

Mohiaddin, R H

1992-09-01

289

Quality image metrics for synthetic images based on perceptual color differences.  

PubMed

Due to the improvement of image rendering processes, and the increasing importance of quantitative comparisons among synthetic color images, it is essential to define perceptually based metrics which enable to objectively assess the visual quality of digital simulations. In response to this need, this paper proposes a new methodology for the determination of an objective image quality metric, and gives an answer to this problem through three metrics. This methodology is based on the LLAB color space for perception of color in complex images, a modification of the CIELab1976 color space. The first metric proposed is a pixel by pixel metric which introduces a local distance map between two images. The second metric associates, to a pair of images, a global value. Finally, the third metric uses a recursive subdivision of the images to obtain an adaptative distance map, rougher but less expensive to compute than the first method. PMID:18249719

Albin, Stephane; Rougeron, Gilles; Péroche, Bernard; Trémeau, Alain

2002-01-01

290

Robustness of visual image quality measures against various monochromatic aberrations  

NASA Astrophysics Data System (ADS)

We examine the correlation between subjective performance and objective image quality metrics, and show that an appropriately defined partial integral of the instrumentation modulation transfer function (MTF), called MTFa, gives the best correlation with available psycho-physical data, including those obtained by other investigators. The Strehl ratio and the radius that encircles 84% of the point-spread-function energy also show that some correlation with subjective performance, but have considerable limitations. These results begin to make real the possibility that the image quality of visual instruments may be characterized by a single figure of merit within the isoplanatic patch, for all types of monochromatic aberrations.

Mouroulis, Pantazis Z.; Cheng, Xiaoxue

1994-08-01

291

A Perceptually Relevant MSE-Based Image Quality Metric.  

PubMed

Image quality metrics (IQMs), such as the mean squared error (MSE) and the structural similarity index (SSIM), are quantitative measures to approximate perceived visual quality. In this paper, through analyzing the relationship between the MSE and the SSIM under an additive noise distortion model, we propose a perceptually relevant MSE-based IQM, MSE-SSIM, which is expressed in terms of the variance of the source image and the MSE between the source and distorted images. Evaluations on three publicly available databases (LIVE, CSIQ, and TID2008) show that the proposed metric, despite requiring less computation, compares favourably in performance to several existing IQMs. In addition, due to its simplicity, MSE-SSIM is amenable for the use in a wide range of image and video tasks that involve solving an optimization problem. As an example, MSE-SSIM is used as the objective function in designing a Wiener filter that aims at optimizing the perceptual visual quality of the output. Experimental results show that the images filtered with a MSE-SSIM-optimal Wiener filter have better visual quality than those filtered with a MSE-optimal Wiener filter. PMID:24057005

Tan, Hui Li; Li, Zhengguo; Tan, Yih Han; Rahardja, Susanto; Yeo, Chuohuo

2013-11-01

292

Temporal image capture and display characterization for metrics for moving image quality  

NASA Astrophysics Data System (ADS)

Temporal measures of display performance are important for depiction of still images, and are even more critical for depiction of moving images (video). In addition to the flicker and crawling patterns that occasionally appear when certain colors/grayscales and patterns are displayed (e.g. DMD/plasma temporal modulation), moving images are susceptible to a host of time-based artifacts (visible defects) such as motion blur, color breakup, image distortion, and incorrect depiction of object motion. Accuracy of temporal representation can be affected by temporal compression (e.g. motion prediction) in the image data handling, and by the operation of the display system (e.g. scaling algorithm). It is widely known that well-presented motion imagery can offer both improved quality and improved interpretability compared to comparable still imagery (for example a freeze frame of a video), provided that timing characteristics are accurately reproduced. Because of the importance of display characteristics, positional measurement of the physical light output of the display is a necessary addition to measurement of image component motion in the video data file. The NIST Motion Image Quality Project team is adapting its method of sequential image capture with external hardware timestamp (Electronic Imaging 2003), to make precision measurements of the temporal characteristics of displays. Hardware measurements are being combined with subjective evaluation of video content and image file analysis, to produce a new model for moving image quality and interpretability, which will serve as a guide both for content creation and for display design.

Roberts, John W.; Hinton, Alma; Carr, Tanya; Fanning, Edward

2004-05-01

293

Comparison of exercise electrocardiography and quantitative thallium imaging for one-vessel coronary artery disease  

SciTech Connect

The relative value of exercise electrocardiography and computer analyzed thallium-201 imaging was compared in 124 patients with 1-vessel coronary artery disease (CAD). Of these, 78 had left anterior descending (LAD), 32 right and 14 left circumflex (LC) CAD. In patients with no previous myocardial infarction (MI), thallium imaging was more sensitive than the electrocardiogram (78% vs 64%, p less than 0.01), but in patients with previous MI, sensitivity was similar. Further, thallium imaging was more sensitive only in LAD and LC disease. Redistribution was compared with ST-segment depression as a marker of ischemia. Only in patients with prior MI (76% vs 44%, p less than 0.01) and only in LC and right CAD did redistribution occur more often than ST depression. Thallium imaging was more accurate in localizing stenoses than the electrocardiogram (p less than 0.001), but did not always correctly predict coronary anatomy. Septal thallium defects were associated with LAD disease in 84%, inferior defects with right CAD in 40% and posterolateral lesion defects with LC CAD in 22%. The results indicate the overall superiority of thallium imaging in 1-vessel CAD compared with exercise electrocardiography; however, there is a wide spectrum of extent and location of perfusion defects associated with each coronary artery. Thallium imaging complements coronary angiography by demonstrating the functional impact of CAD on myocardial perfusion.

Kaul, S.; Kiess, M.; Liu, P.; Guiney, T.E.; Pohost, G.M.; Okada, R.D.; Boucher, C.A.

1985-08-01

294

Radiation dose and image quality for paediatric interventional cardiology  

NASA Astrophysics Data System (ADS)

Radiation dose and image quality for paediatric protocols in a biplane x-ray system used for interventional cardiology have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-20 cm of PMMA). Images from fluoroscopy (low, medium and high) and cine modes have been archived in digital imaging and communications in medicine (DICOM) format. Signal-to-noise ratio (SNR), figure of merit (FOM), contrast (CO), contrast-to-noise ratio (CNR) and high contrast spatial resolution (HCSR) have been computed from the images. Data on dose transferred to the DICOM header have been used to test the values of the dosimetric display at the interventional reference point. ESAK for fluoroscopy modes ranges from 0.15 to 36.60 µGy/frame when moving from 4 to 20 cm PMMA. For cine, these values range from 2.80 to 161.10 µGy/frame. SNR, FOM, CO, CNR and HCSR are improved for high fluoroscopy and cine modes and maintained roughly constant for the different thicknesses. Cumulative dose at the interventional reference point resulted 25-45% higher than the skin dose for the vertical C-arm (depending of the phantom thickness). ESAK and numerical image quality parameters allow the verification of the proper setting of the x-ray system. Knowing the increases in dose per frame when increasing phantom thicknesses together with the image quality parameters will help cardiologists in the good management of patient dose and allow them to select the best imaging acquisition mode during clinical procedures.

Vano, E.; Ubeda, C.; Leyton, F.; Miranda, P.

2008-08-01

295

Perfusion and Diffusion-Weighted MR Imaging Guided Therapy of Vertebral Artery Dissection: Intraarterial Thrombolysis through an Occipital Vertebral Anastomosis  

Microsoft Academic Search

Summary: Management of arterial dissections can be par- ticularly challenging. We report a case of vertebral artery dissection in which perfusion- and diffusion-weighted MR imaging findings suggested the presence of salvageable tissue, despite that the patient had symptoms for more than 40 hours. Direct access to the distal vascular territory was unattainable, and the presence of collateral circulation through an

Lucas Restrepo; Gustavo Pradilla; Rafael Llinas; Norman J. Beauchamp

296

[The findings of computed tomography (CT) and magnetic resonance imaging (MRI) in pulmonary arterial hypertension].  

PubMed

Technical advances of multidetector-row computed tomography(MDCT) and magnetic resonance imaging(MRI) made these modalities more important in the evaluation and for differential diagnosis of pulmonary arterial hypertension (PAH). The advantages of CT and MRI are noninvasive examination, wide field of view, excellent reproducibility, high spatial resolution and 3-dimensional (3-D) reconstruction images. Morphological changes of the PAH, which are right ventricular hypertrophy and dilatation of main and central pulmonary artery(PA), right ventricle, right atria, superior and inferior vena cava, and coronary sinus, are depicted well by these modalities. The 3-D CT and MR angiography can depict peripheral and central PA, and pulmonary veins, which are important information of the cause of PAH. Myocardial changes of PAH can be detected by gadolinium delayed enhancement of MRI. CT and MRI are promising method to diagnose and manage the PAH in future. PMID:19051729

Koito, Hitoshi

2008-11-01

297

Arterial Spin Label Imaging of Acute Ischemic Stroke and Transient Ischemic Attack  

PubMed Central

Since acute ischemic stroke and transient ischemic attack (TIA) are fundamentally disruptions of brain hemodynamics, neuroimaging of brain perfusion might be expected to be of clinical utility. Recently, a noncontrast method of measuring CBF using arterial spin labeling (ASL) has become feasible in the clinical setting. It has advantages when compared to dynamic susceptibility contrast (DSC) bolus contrast perfusion-weighted imaging (PWI) that include lack of exposure to gadolinium-based contrast materials, improved quantitation, and decreased sensitivity to susceptibility artifacts and motion. Drawbacks of ASL include reduced signal-to-noise (SNR) and high sensitivity to arterial transit delays. While deleterious for quantitative perfusion measurements, the sensitivity of ASL to late arriving blood can be beneficial to visualize collateral flow. This chapter will discuss ASL imaging findings in patients presenting with acute ischemic stroke and TIA, focusing on typical appearances, common artifacts, and comparisons with bolus contrast PWI.

Zaharchuk, Greg

2011-01-01

298

Processor quality assurance using digital imaging.  

PubMed

The purpose of this study was to develop and test a computer imaging method for assessing longitudinal processor variability. A technique called adaptive histogram equalization was used to test deviation in automatic processing when a test film is compared with a time-temperature processed standard at two different kVp's and film speeds. In a 14-day study we found that the density ranges for the standard film did not change, while the density range of the automatically processed films changed by a factor of two. These results suggest that if automatic processing is to be used for films taken as part of a longitudinal study-for example, subtraction-then processor variation can potentially lead to incorrect inference of bone gain or loss. PMID:9167431

Goren, A D; Dunn, S M; Van der Stelt, P F

1997-04-01

299

Non-traumatic vascular emergencies: imaging and intervention in acute arterial conditions  

Microsoft Academic Search

.   Methods of imaging and intervention in acute non-traumatic vascular arterial conditions has changed substantially during\\u000a recent years. Computed tomography, MRI angiography and, more recently, intravascular ultrasonography (IVUS) have replaced\\u000a to a large extent conventional diagnostic angiography. An increasing number of patients are treated by endovascular interventions\\u000a and numerous new treatment methods have been evaluated. Technical development of new equipment

Wojciech Cwikiel; Mehran Midia; David Williams

2002-01-01

300

Interactive Guidance by Image Overlay in Robot Assisted Coronary Artery Bypass  

Microsoft Academic Search

\\u000a We present an original visual guidance system in the especially difficult context of robot assisted coronary artery bypass\\u000a graft. The overlay of a preoperative coronary tree model on the endoscopic images is initialized to help the surgeon to locate\\u000a himself. Then the surgeon points some landmarks observed in the operating field during the motion of the endoscope. The overlay\\u000a is

Fabien Mourgues; Thierry Viéville; Volkmar Falk; Ève Coste-manière

2003-01-01

301

Imaging of aortopulmonary collateral arteries with high-resolution multidetector CT  

Microsoft Academic Search

Background  Precise visualization of the pulmonary vasculature is mandatory for adequate treatment of patients with pulmonary atresia and ventricular septal defect (PA-VSD). Aortopulmonary collateral arteries (APCs) can be visualized by selective injections of contrast agent in the catheterization laboratory.Objective  To evaluate multidetector CT (MDCT) and different image postprocessing methods for analysis of complex pulmonary blood supply in patients with PA-VSD.Materials and methods  Eight

Gerald F. Greil; Max Schoebinger; Axel Kuettner; Juergen F. Schaefer; Florian Dammann; Claus D. Claussen; Michael Hofbeck; Hans-Peter Meinzer; Ludger Sieverding

2006-01-01

302

Characterization of distensibility, plaque burden, and composition of the atherosclerotic carotid artery using magnetic resonance imaging  

PubMed Central

Purpose: Arterial distensibility is a marker that can measure vessel wall functional and structural changes resulting from atherosclerosis with applications including estimation of mechanical properties of the wall. We sought to assess the feasibility of using magnetic resonance imaging (MRI) to include wall distensibility in the characterization of atherosclerotic carotid arteries and to analyze the relationship between distensibility and morphological and compositional plaque features. Methods: Five healthy volunteers were imaged with a multiple-slice CINE MR sequence twice, within 24 h, to determine the interscan reproducibility of distensibility measurements. Twenty-one subjects with >15% carotid stenosis and the five healthy volunteers were imaged using a multicontrast carotid MRI protocol to characterize arterial wall morphology and composition. Normalized wall index (wall area/total vessel area), maximum wall thickness and, if present, percentages of wall area occupied by calcification and lipid-rich necrotic core were determined. A multiple-slice CINE MR sequence was added to the multicontrast protocol to measure the distensibility coefficient (DC) at several locations spanning the bifurcation. The intraclass correlation coefficient (ICC) and the coefficient of variation were used to assess the reproducibility of DC measurements made on the healthy subjects. The DC was compared between arterial segments and between the healthy and diseased groups. Furthermore, within the diseased group, DC was correlated to plaque morphology and composition at each location as well as that averaged over the plaque. Results: Distensibility measurements were highly reproducible: ICC (95% confidence interval) was 0.998 (0.96–1.0) for the common carotid segment and 0.990 (0.92–1.0) for the internal carotid segment. In healthy volunteers, we found significantly higher distensibility in the common segment of the carotid artery compared to the internal carotid segment (mean ± SD = 4.56 ± 1.02 versus 3.56 ± 1.32 × 10?5/Pa; p < 0.05). However, no segmental differences were seen in the diseased group (3.25 ± 1.84 versus 3.26 ± 1.60 × 10?5/Pa; p = 0.607). Location-to-location changes in DC were not found to correlate to changes in the local plaque morphology or composition nor were average DC found to be associated with aggregate plaque features. Conclusions: These results demonstrate the feasibility of MRI to measure distensibility in the carotid artery and to presumably detect changes in distensibility due to age and/or disease. The results suggest that the effect of atherosclerosis on local distensibility may not strongly depend upon the specific underlying plaque features in mild to moderate stenotic carotid lesions though more diffuse or nonlocal changes in arterial distensibility could not be ruled out.

Canton, Gador; Hippe, Daniel S.; Sun, Jie; Underhill, Hunter R.; Kerwin, William S.; Tang, Dalin; Yuan, Chun

2012-01-01

303

Perceived Image Quality Improvements from the Application of Image Deconvolution to Retinal Images from an Adaptive Optics Fundus Imager  

NASA Astrophysics Data System (ADS)

Aim: The objective of this project was to apply an image restoration methodology based on wavefront measurements obtained with a Shack-Hartmann sensor and evaluating the restored image quality based on medical criteria.Methods: Implementing an adaptive optics (AO) technique, a fundus imager was used to achieve low-order correction to images of the retina. The high-order correction was provided by deconvolution. A Shack-Hartmann wavefront sensor measures aberrations. The wavefront measurement is the basis for activating a deformable mirror. Image restoration to remove remaining aberrations is achieved by direct deconvolution using the point spread function (PSF) or a blind deconvolution. The PSF is estimated using measured wavefront aberrations. Direct application of classical deconvolution methods such as inverse filtering, Wiener filtering or iterative blind deconvolution (IBD) to the AO retinal images obtained from the adaptive optical imaging system is not satisfactory because of the very large image size, dificulty in modeling the system noise, and inaccuracy in PSF estimation. Our approach combines direct and blind deconvolution to exploit available system information, avoid non-convergence, and time-consuming iterative processes. Results: The deconvolution was applied to human subject data and resulting restored images compared by a trained ophthalmic researcher. Qualitative analysis showed significant improvements. Neovascularization can be visualized with the adaptive optics device that cannot be resolved with the standard fundus camera. The individual nerve fiber bundles are easily resolved as are melanin structures in the choroid. Conclusion: This project demonstrated that computer-enhanced, adaptive optic images have greater detail of anatomical and pathological structures.

Soliz, P.; Nemeth, S. C.; Erry, G. R. G.; Otten, L. J.; Yang, S. Y.

304

Quantitative optical imaging of vascular response in vivo in a model of peripheral arterial disease.  

PubMed

The mouse hind limb ischemia (HLI) model is well established for studying collateral vessel formation and testing therapies for peripheral arterial disease, but there is a lack of quantitative techniques for intravitally analyzing blood vessel structure and function. To address this need, non-invasive, quantitative optical imaging techniques were developed to assess the time-course of recovery in the mouse HLI model. Hyperspectral imaging and optical coherence tomography (OCT) were used to non-invasively image hemoglobin oxygen saturation and microvessel morphology plus blood flow, respectively, in the anesthetized mouse after induction of HLI. Hyperspectral imaging detected significant increases in hemoglobin saturation in the ischemic paw as early as 3 days after femoral artery ligation (P < 0.01), and significant increases in distal blood flow were first detected with OCT 14 days postsurgery (P < 0.01). Intravital OCT images of the adductor muscle vasculature revealed corkscrew collateral vessels characteristic of the arteriogenic response to HLI. The hyperspectral imaging and OCT data significantly correlated with each other and with laser Doppler perfusion imaging (LDPI) and tissue oxygenation sensor data (P < 0.01). However, OCT measurements acquired depth-resolved information and revealed more sustained flow deficits following surgery that may be masked by more superficial measurements (LDPI, hyperspectral imaging). Therefore, intravital OCT may provide a robust biomarker for the late stages of ischemic limb recovery. This work validates non-invasive acquisition of both functional and morphological data with hyperspectral imaging and OCT. Together, these techniques provide cardiovascular researchers an unprecedented and comprehensive view of the temporal dynamics of HLI recovery in living mice. PMID:23955718

Poole, Kristin M; Tucker-Schwartz, Jason M; Sit, Wesley W; Walsh, Alex J; Duvall, Craig L; Skala, Melissa C

2013-08-16

305

Improved quality of reconstructed images through sifting of data in statistical image reconstruction  

NASA Astrophysics Data System (ADS)

The U.S. Air Force employs adaptive optics systems to produce images of exo-atmospheric objects. Typically, a large set of short exposure images are collected, re-centered to compensate for random image motion, averaged together to improve the signal to noise ratio, and then processed to form a reconstructed image. It is known that some short exposure images will be better than others, so some researchers have suggested that image quality can be improved by selecting a subset of the short exposure images according to some quality criterion, and then processing the average of this subset to form a single, high quality image. This thesis investigates the statistical implications of using frame selection as a post-processing technique to enhance images of exo-atmospheric objects measured by Air Force adaptive optics systems. The results demonstrate that frame selection narrows the optical system point spread function, which reduces image blurring, and increases the frequency spectrum signal to noise ratio, particularly in the mid-frequency range. For extended objects, the technique is light level dependent: for a 1 meter adaptive optics telescope, frame selection will yield an increase in signal to noise ratio for objects brighter than visual magnitude +2.3.

Stoudt, Craig A.

1993-12-01

306

Visual factors and image analysis in the encoding of high-quality still images  

NASA Astrophysics Data System (ADS)

In the encoding of high quality images beyond current standards, a reexamination of issues in the representation, processing and encoding problems is needed. The fundamental reason for that change of emphasis is that the image representation, sampling density, color and motion parameters are no longer given by accepted practices or standards and, thus, require study. Some basic issues that should be reconsidered are as follows: (1) The theoretical or limiting information content of images viewed at a fixed viewing distance, as the scanning grid becomes denser and denser. This limit is determined fundamentally by the properties of the human visual system. In particular, attention must be given to the representation of very high quality color images, an issue that is currently poorly handled in television engineering practice. (2) The display or output in print or on other media of high quality color images. Since the possibility now exists of using an output device which has a resolution substantially higher than the representation or scanning grid, the interpolation of images to take advantage of this higher output grid becomes an important issue. Common approaches to interpolation are not suited to maintain high image quality. (3) With increasing resolution, the critical image information to the perception of high quality occurs, in general, in a few portions of the image, and is associated to definite image structures, such as edges, streaks, corners, and texture. It may therefore be important, for both encoding and interpolation purposes, to perform some image analysis that will detect the presence of a structure of interest, and determine accordingly the most effective encoding or processing strategy. In this paper, we examine briefly each of these issues, establish some preliminary results, and illustrate some of the issues and approaches to these problems. The purpose of this paper is to cast the problem formulations in broad terms and then follow with a few specific results and a discussion.

Algazi, V. Ralph; Reed, Todd R.; Ford, Gary E.; Estes, Robert R.

1991-11-01

307

Sharpness metric for no-reference image visual quality assessment  

NASA Astrophysics Data System (ADS)

This paper presents a novel sharpness metric for color images. The proposed metric can be used for no-reference assessment of image visual quality. The metric basically relies on local power of wavelet transform high-frequency coefficients. It also takes into account possibility of presence of macrophotography and portrait photography effects in an image where the image part (usually central one) in sharp whilst the remained part (background) is smeared. Such effects usually increase subjective evaluation of image visual quality by humans. The effects are taken into consideration by joint analysis of wavelet coefficients with largest and smallest squared absolute values. Besides, we propose a simple mechanism for blocking artifact accounting (if an image is compressed by JPEG) and compensation of this factor contribution. Finally, the proposed sharpness metric is calculated in color space YCbCr as a weighted sum of sharpness components. Weight optimization has shown that a weight for intensity component Y is to be considerably smaller than weights for color components Cb and Cr. Optimization of weights for all stages of sharpness metric calculation is carried out for specialized database NRTID that contains 500 test images with previously determined MOS (Mean Opinion Score). Spearman rank order correlation coefficient (SROCC) determined for the designed sharpness metric and MOS is used as optimization criterion. After optimization, it reaches 0.71. This is larger than for other known available no-reference metrics considered at verification stage.

Ponomarenko, Nikolay N.; Lukin, Vladimir V.; Eremeev, Oleg I.; Egiazarian, Karen O.; Astola, Jaakko T.

2012-02-01

308

DIANE stationary neutron radiography system image quality and industrial applications  

NASA Astrophysics Data System (ADS)

The SODERN neutron radiography laboratory has operated since February 1993 using a sealed tube generator (GENIE 46). An experimental programme of characterization (dosimetry, spectroscopy) has confirmed the expected performances concerning: neutron flux intensity, neutron energy range, residual gamma flux. Results are given in a specific report [2]. This paper is devoted to the image performance reporting. ASTM and specific indicators have been used to test the image quality with various converters and films. The corresponding modulation transfer functions are to be determined from image processing. Some industrial applications have demonstrated the capabilities of the system: corrosion detection in aircraft parts, ammunitions filling testing, detection of polymer lacks in sandwich steel sheets, detection of moisture in a probe for geophysics, residual ceramic cores imaging in turbine blades. Various computerized electronic imaging systems will be tested to improve the industrial capabilities.

Cluzeau, S.; Huet, J.; Le Tourneur, P.

1994-05-01

309

3D volume-selective turbo spin echo for carotid artery wall imaging with navigator detection of swallowing  

Microsoft Academic Search

Purpose: To improve 3D volume-selective turbo spin echo (TSE) carotid artery wall imaging by incorporating naviga- tors to reduce artifacts caused by swallowing. Materials and Methods: Images were acquired on a Sie- mens Magnetom Sonata 1.5T scanner. 3D volume-selective TSE scans of the carotid arteries were acquired in six healthy volunteers. A cross-pair navigator placed on the back of the

Lindsey A. Crowe; Jennifer Keegan; Peter D. Gatehouse; Raad H. Mohiaddin; Anitha Varghese; Karen Symmonds; Timothy M. Cannell; Guang Zhong Yang; David N. Firmin

2005-01-01

310

Continuous image writer with improved image quality for high-accuracy optical patterning  

NASA Astrophysics Data System (ADS)

We report on the development of a production tool for fast optical maskless patterning. The Continuous Image Writer (CIW) combines the advantages of direct writing by using a programmable mask with the advantages of conventional optical lithography by using the same lithographic process for image formation in photoresist. An electronically programmable Spatial Light Modulator (SLM) is imaged into the substrate by passing a demagnifying Fourier optics. The use of short pulses of a KrF excimer laser allows the imaging of the extended image field of the SLM without stopping the substrate carrying stage during exposure. This results in short writing times. Based on the experiences with a production-like prototype of the CIW we have investigated the various contributions to image quality such as address grid, stitching errors, and SLM quality. This paper describes a method for achieving a critical dimension performance well suited for the generation of photomask and wafer patterns for present and future technology nodes.

Paufler, Joerg; Brunn, Stefan; Koerner, Tim

2001-04-01

311

Imaging findings and transcatheter arterial chemoembolization of hepatic malignancy with right atrial embolus in 46 patients  

PubMed Central

AIM: To analyze the imaging findings of hepatic malignancy with right atrial (RA) embolus. METHODS: Forty-six patients with an embolus in the RA were diagnosed, including 44 patients with hepatocellular carcinoma (HCC), 1 patient with cholangiocellular carcinoma and 1 patient with hepatic carcinoma metastasis. The diagnosis was confirmed by clinical examination, serum ?-fetoprotein and imaging. Seventeen patients underwent transcatheter arterial chemoembolization (TACE). RESULTS: On enhancement computer tomography (CT) or magnetic resonance (MR) imaging, a nodular filling defect in the RA could be easily found, with a slight enhancement in the arterial phase. The coronal images of CT or MR showed the extent of lesion. Lipiodol entered the embolus after TACE, hence reducing the speed of embolus growth. There was a survival benefit for patients receiving anticancer treatment. CONCLUSION: Patients with HCC, showing a filling defect of the inferior vena cava (IVC), hepatic vein (HV) and RA on images, can be diagnosed with RA embolus. Encroachment of the RA is very rare in patients with hepatic malignancies. Furthermore, a prolongation of survival time is found in those patients who underwent TACE.

Cheng, Hong-Yan; Wang, Xiao-Yan; Zhao, Guo-Li; Chen, Dong

2008-01-01

312

Recovery of reversed basilar artery flow as seen by transcranial sonography and MRA source images for vertebral dissection.  

PubMed

The dissection of the intracranial vertebral artery (VAD) is a common cause of young age brain stem stroke. VAD can be detected by conventional angiography, but there is yet no agreement on the most effective tool to use for the detection of VAD. Here, we report a patient with VAD, who was diagnosed with an intimal flap within the left vertebral artery by the magnetic resonance angiography (MRA) source images. Transcranial Doppler (TCD) showed a reversed flow in the basilar artery. After 4 months, TCD and transcranial color-coded Doppler (TCCD) confirmed a normal anterograde flow of the vertebro-basilar arteries. PMID:18318795

Lee, Sung Ik; Yang, Hyun Duk; Son, Il Hong; Han, Sun Jung

2007-12-21

313

Simultaneous Analysis and Quality Assurance for Diffusion Tensor Imaging  

PubMed Central

Diffusion tensor imaging (DTI) enables non-invasive, cyto-architectural mapping of in vivo tissue microarchitecture through voxel-wise mathematical modeling of multiple magnetic resonance imaging (MRI) acquisitions, each differently sensitized to water diffusion. DTI computations are fundamentally estimation processes and are sensitive to noise and artifacts. Despite widespread adoption in the neuroimaging community, maintaining consistent DTI data quality remains challenging given the propensity for patient motion, artifacts associated with fast imaging techniques, and the possibility of hardware changes/failures. Furthermore, the quantity of data acquired per voxel, the non-linear estimation process, and numerous potential use cases complicate traditional visual data inspection approaches. Currently, quality inspection of DTI data has relied on visual inspection and individual processing in DTI analysis software programs (e.g. DTIPrep, DTI-studio). However, recent advances in applied statistical methods have yielded several different metrics to assess noise level, artifact propensity, quality of tensor fit, variance of estimated measures, and bias in estimated measures. To date, these metrics have been largely studied in isolation. Herein, we select complementary metrics for integration into an automatic DTI analysis and quality assurance pipeline. The pipeline completes in 24 hours, stores statistical outputs, and produces a graphical summary quality analysis (QA) report. We assess the utility of this streamlined approach for empirical quality assessment on 608 DTI datasets from pediatric neuroimaging studies. The efficiency and accuracy of quality analysis using the proposed pipeline is compared with quality analysis based on visual inspection. The unified pipeline is found to save a statistically significant amount of time (over 70%) while improving the consistency of QA between a DTI expert and a pool of research associates. Projection of QA metrics to a low dimensional manifold reveal qualitative, but clear, QA-study associations and suggest that automated outlier/anomaly detection would be feasible.

Lauzon, Carolyn B.; Asman, Andrew J.; Esparza, Michael L.; Burns, Scott S.; Fan, Qiuyun; Gao, Yurui; Anderson, Adam W.; Davis, Nicole; Cutting, Laurie E.; Landman, Bennett A.

2013-01-01

314

Elastographic image quality vs. tissue motion in vivo.  

PubMed

Elastography is a noninvasive method of imaging tissue elasticity using standard ultrasound equipment. In conventional elastography, axial strain elastograms are generated by cross-correlating pre- and postcompression digitized radio frequency (RF) echo frames acquired from the tissue before and after a small uniaxial compression, respectively. The time elapsed between the pre- and the postcompression frames is referred to as the interframe interval. For in vivo elastography, the interframe interval is critical because uncontrolled physiologic motion such as heartbeat, muscle motion, respiration and blood flow introduce interframe decorrelation that reduces the quality of elastograms. To obtain a measure of this decorrelation, in vivo experimental data (from human livers and thyroids) at various interframe intervals were obtained from 20 healthy subjects. To further examine the effect of the different interframe intervals on the elastographic image quality, the experimental data were also used in combination with elastographic simulation data. The deterioration of elastographic image quality was objectively evaluated by computing the area under the strain filter (SF) at a given resolution. The experimental results of this study demonstrate a statistical exponential behavior of the temporal decay of the echo signal cross-correlation amplitudes from the in vivo tissues due to uncontrollable motion. The results also indicate that the dynamic range and height of the SF are reduced at increased interframe intervals, suggesting that good objective image quality may be achieved provided only that a high frame rate is maintained in elastographic applications. PMID:16785007

Chandrasekhar, R; Ophir, J; Krouskop, T; Ophir, K

2006-06-01

315

Image quality, space-qualified UV interference filters  

NASA Astrophysics Data System (ADS)

The progress during the contract period is described. The project involved fabrication of image quality, space-qualified bandpass filters in the 200-350 nm spectral region. Ion-assisted deposition (IAD) was applied to produce stable, reasonably durable filter coatings on space compatible UV substrates. Thin film materials and UV transmitting substrates were tested for resistance to simulated space effects.

Mooney, Thomas A.

1992-09-01

316

Retinal Image Quality and Postnatal Visual Experience during Infancy  

PubMed Central

Studies of animal models have demonstrated that abnormal visual experience can lead to abnormal visual development. The provision of normal optical experience for human infants and children requires an understanding of their typical retinal image quality in the natural dynamic environment. The literature related to this topic is reviewed.

Candy, T. Rowan; Wang, Jingyun; Ravikumar, Sowmya

2009-01-01

317

Using borehole images to quantify reservoir quality and stratigraphic distribution  

SciTech Connect

Understanding the distribution of good-quality reservoir rock in a prospective formation is essential to improved reserves computation and maximized production. High-resolution borehole images provide a rapid and efficient method to evaluate reservoir quality over extended sequences. Microconductivity curves from images are evaluated using modal analysis on histograms to establish specific populations. These populations are assigned to electrofacies, which are discriminated using other logs and core data to generate a lithofacies column. Net pay, or sand counts, are computed based on the distribution of log-derived lithofacies. Reservoir distribution is based on the integration of structural and stratigraphic image analyses. This method is applied to two different reservoirs, the first example is of a well developed, valley-fill sequence comprising thick, stacked fluvial-deltaic channel sands. These sands are over 100 ft thick, have >20% porosity, and over 200 md permeability. The distribution and thickness of optimum quality reservoir is random, however. The second example is of multiple, small scale, depositional units between 3 in. and 24 in., which have 15% porosity with >500 md permeability. The net thickness and exact position of high-quality reservoir intervals is not apparent from standard logs, but becomes clear after image analysis.

Roestenburg, J.W. (Schlumberger Geophysics Nusantara, Jakarta (Indonesia))

1994-07-01

318

The influence of consumer's event quality perception on destination image  

Microsoft Academic Search

Purpose – The purpose of this study is to examine the theoretical relationship between event quality perceptions of an international sport event and the host city's destination image. Design\\/methodology\\/approach – Reliability and validity of the measurement scale were established through a confirmatory factor analysis (CFA), Cronbach's alpha analyses, and intercorrelation analyses. A structural equation model (SEM) test with maximum likelihood

Kae Sung Moon; May Kim; Yong Jae Ko; Daniel P. Connaughton; Jeoung Hak Lee

2011-01-01

319

Imaging-based treatment selection for intravenous and intra-arterial stroke therapies: a comprehensive review  

PubMed Central

Reperfusion therapy is the only approved treatment for acute ischemic stroke. The current approach to patient selection is primarily based on the time from stroke symptom onset. However, this algorithm sharply restricts the eligible patient population, and neglects large variations in collateral circulation that ultimately determine the therapeutic time window in individual patients. Time alone is unlikely to remain the dominant parameter. Alternative approaches to patient selection involve advanced neuroimaging methods including MRI diffusion-weighted imaging, magnetic resonance and computed tomography perfusion imaging and noninvasive angiography that provide potentially valuable information regarding the state of the brain parenchyma and the neurovasculature. These techniques have now been used extensively, and there is emerging evidence on how specific imaging data may result in improved clinical outcomes. This article will review the major studies that have investigated the role of imaging in patient selection for both intravenous and intra-arterial therapies.

Yoo, Albert J; Pulli, Benjamin; Gonzalez, R Gilberto

2011-01-01

320

Therapeutic response assessment of transcatheter arterial chemoembolization for hepatocellular carcinoma: ultrasonography, CT and MR imaging.  

PubMed

Two randomized controlled trials identified that transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) shows a significant survival benefit compared with controls, after a long-term controversy. Thus, TACE is the current standard of care for patients presenting with multinodular HCC. Monitoring tumor response to TACE is part of the clinical management of HCC patients. Imaging, including ultrasonography, computed tomography and magnetic resonance imaging, has an important role in assessing therapeutic effects earlier and more objectively. Imaging assessment needs to detect not only a reduction in overall tumor load but also a reduction in viable tumor. Here, we give an overview of the current status of the imaging assessment of HCC response to TACE. PMID:23428860

Minami, Yasunori; Kudo, Masatoshi

2013-02-20

321

An improved structural similarity for image quality assessment  

NASA Astrophysics Data System (ADS)

Objective quality assessment has been widely used in image processing for its convenience. Usually human eyes are the terminal of observing images, so many researchers have been studing the objective image quality evaluation method based on Human Visual System (HVS) for decades. Although many methods have been proposed, most of them are based on error sensitivity and are not better than simple PSNR (MSE). Recently the Structural Similarity (SSIM) based on images' structural information is proposed, in which the philosophy is that the HVS is highly adapted to extract structural information from the viewing field, and simulation results have proved it is better than PSNR MSE). By deeply studing SSIM, we find it fails to measure the blurred images with a lot of flat regions and has some shortcomings in its equation. Based on this we propose an improved objective quality assessment method which is called as Gradient-based Structural Similarity (GSSIM). Experiment results show that GSSIM is more consistent with HVS than SSIM and PSNR (MSE).

Pan, Xiao-zhou; Yang, Chun-ling; Xie, Sheng-li

2005-11-01

322

Image quality in conventional chest radiography. Evaluation using the postprocessing tool Diamond View ®  

Microsoft Academic Search

The objective of this work was to evaluate the influence of the postprocessing tool Diamond View® (Siemens AG Medical Solutions, Germany) on image quality in conventional chest radiography. Evaluation of image quality remains a challenge in conventional radiography. Based on the European Commission quality criteria we evaluated the improvement of image quality when applying the new postprocessing tool Diamond View®

Tilo Niemann; Clemens Reisinger; Philipp Rau; Jochen Schwarz; Laura Ruis-Lopez; Georg Bongartz

2010-01-01

323

Automatic image quality assessment for uterine cervical imagery  

NASA Astrophysics Data System (ADS)

Uterine cervical cancer is the second most common cancer among women worldwide. However, its death rate can be dramatically reduced by appropriate treatment, if early detection is available. We are developing a Computer-Aided-Diagnosis (CAD) system to facilitate colposcopic examinations for cervical cancer screening and diagnosis. Unfortunately, the effort to develop fully automated cervical cancer diagnostic algorithms is hindered by the paucity of high quality, standardized imaging data. The limited quality of cervical imagery can be attributed to several factors, including: incorrect instrumental settings or positioning, glint (specular reflection), blur due to poor focus, and physical contaminants. Glint eliminates the color information in affected pixels and can therefore introduce artifacts in feature extraction algorithms. Instrumental settings that result in an inadequate dynamic range or an overly constrained region of interest can reduce or eliminate pixel information and thus make image analysis algorithms unreliable. Poor focus causes image blur with a consequent loss of texture information. In addition, a variety of physical contaminants, such as blood, can obscure the desired scene and reduce or eliminate diagnostic information from affected areas. Thus, automated feedback should be provided to the colposcopist as a means to promote corrective actions. In this paper, we describe automated image quality assessment techniques, which include region of interest detection and assessment, contrast dynamic range assessment, blur detection, and contaminant detection. We have tested these algorithms using clinical colposcopic imagery, and plan to implement these algorithms in a CAD system designed to simplify high quality data acquisition. Moreover, these algorithms may also be suitable for image quality assessment in telemedicine applications.

Gu, Jia; Li, Wenjing

2006-03-01

324

Image quality specification and maintenance for airborne SAR  

NASA Astrophysics Data System (ADS)

Specification, verification, and maintenance of image quality over the lifecycle of an operational airborne SAR begin with the specification for the system itself. Verification of image quality-oriented specification compliance can be enhanced by including a specification requirement that a vendor provide appropriate imagery at the various phases of the system life cycle. The nature and content of the imagery appropriate for each stage of the process depends on the nature of the test, the economics of collection, and the availability of techniques to extract the desired information from the data. At the earliest lifecycle stages, Concept and Technology Development (CTD) and System Development and Demonstration (SDD), the test set could include simulated imagery to demonstrate the mathematical and engineering concepts being implemented thus allowing demonstration of compliance, in part, through simulation. For Initial Operational Test and Evaluation (IOT&E), imagery collected from precisely instrumented test ranges and targets of opportunity consisting of a priori or a posteriori ground-truthed cultural and natural features are of value to the analysis of product quality compliance. Regular monitoring of image quality is possible using operational imagery and automated metrics; more precise measurements can be performed with imagery of instrumented scenes, when available. A survey of image quality measurement techniques is presented along with a discussion of the challenges of managing an airborne SAR program with the scarce resources of time, money, and ground-truthed data. Recommendations are provided that should allow an improvement in the product quality specification and maintenance process with a minimal increase in resource demands on the customer, the vendor, the operational personnel, and the asset itself.

Clinard, Mark S.

2004-08-01

325

Radiologists' confidence in detecting abnormalities on chest images and their subjective judgments of image quality  

NASA Astrophysics Data System (ADS)

The relationship between subjective judgments of image quality for the performance of specific detection tasks and radiologists' confidence level in arriving at correct diagnoses was investigated in two studies in which 12 readers, using a total of three different display environments, interpreted a series of 300 PA chest images. The modalities used were conventional films, laser-printed films, and high-resolution CRT display of digitized images. For the detection of interstitial disease, nodules, and pneumothoraces, there was no statistically significant correlation (Spearman rho) between subjective ratings of quality and radiologists' confidence in detecting these abnormalities. However, in each study, for all modalities and all readers but one, a small but statistically significant correlation was found between the radiologists' ability to correctly and confidently rule out interstitial disease and their subjective ratings of image quality.

King, Jill L.; Gur, David; Rockette, Howard E.; Curtin, Hugh D.; Obuchowski, Nancy A.; Thaete, F. L.; Britton, Cynthia A.; Metz, Charles E.

1991-07-01

326

Comprehensive quality assurance phantom for cardiovascular imaging systems  

NASA Astrophysics Data System (ADS)

With the advent of high heat loading capacity x-ray tubes, high frequency inverter type generators, and the use of spectral shaping filters, the automatic brightness/exposure control (ABC) circuit logic employed in the new generation of angiographic imaging equipment has been significantly reprogrammed. These new angiographic imaging systems are designed to take advantage of the power train capabilities to yield higher contrast images while maintaining, or lower, the patient exposure. Since the emphasis of the imaging system design has been significantly altered, the system performance parameters one is interested and the phantoms employed for the quality assurance must also change in order to properly evaluate the imaging capability of the cardiovascular imaging systems. A quality assurance (QA) phantom has been under development in this institution and was submitted to various interested organizations such as American Association of Physicists in Medicine (AAPM), Society for Cardiac Angiography & Interventions (SCA&I), and National Electrical Manufacturers Association (NEMA) for their review and input. At the same time, in an effort to establish a unified standard phantom design for the cardiac catheterization laboratories (CCL), SCA&I and NEMA have formed a joint work group in early 1997 to develop a suitable phantom. The initial QA phantom design has since been accepted to serve as the base phantom by the SCA&I- NEMA Joint Work Group (JWG) from which a comprehensive QA Phantom is being developed.

Lin, Pei-Jan P.

1998-07-01

327

Arterial embolization hyperthermia: hepatic iron particle distribution and its potential determination by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Arterial embolization hyperthermia (AEH) consists of arterially embolizing liver tumours with ferromagnetic particles that generate hysteretic heating on exposure to an alternating magnetic field. A critical component of AEH is the concentration and distribution of ferromagnetic particles in the normal hepatic parenchyma (NHP), as well as in the tumour tissue. If the distribution of particles in NHP is heterogeneous, with areas of high concentration, then unwanted areas of necrosis may result during AEH. Using an in vivo rabbit liver tumour model, this study showed that hepatic arterial infusion of ferromagnetic particles does indeed result in a heterogeneous distribution of iron in NHP. The radiological technique of magnetic resonance imaging (MRI) was then evaluated as a potential tool for non-invasively and prospectively determining the concentration and distribution of particles within the hepatic tumour and NHP following hepatic arterial infusion. A preliminary in vitro experiment showed that although the concentration of iron within the tumour tissue (1.92-3.50 mg of iron per gram of tissue) was too great to measure, MRI was able to accurately determine the lower iron concentration (0.10-0.53 mg of iron per gram of tissue) in NHP. Further work is needed to evaluate MRI under in vivo conditions. If successful, MRI could become an important component of an emerging novel treatment for advanced hepatic malignancies.

Moroz, Paul; Pardoe, Heath; Jones, Stephen K.; St. Pierre, Timothy G.; Song, Swithin; Gray, Bruce N.

2002-05-01

328

Cross-Sectional Elastic Imaging of Arterial Wall Using Intravascular Ultrasonography  

NASA Astrophysics Data System (ADS)

There have been several studies on the imaging of the distribution of the elasticity of the arterial wall using intravascular ultrasonography (IVUS). In those studies, the elasticity is estimated only during ventricular diastole. However, the viscous characteristics of the smooth muscle in the media of the arterial wall are also included in the strain measured during diastole. Alternatively, during systole, the smooth muscle has an almost purely elastic characteristic. However, the IVUS probe moves greatly due to the arrival of the pulsatile wave at the beginning of the ejection period. Therefore, in this paper, we propose a method to compensate for the movement of the IVUS probe in order to precisely measure the regional change in thickness of the arterial wall during one cardiac cycle. Basic experiments using a silicone rubber tube, in which pulsatile flow is generated by an artificial heart, determined the two-dimensional (2-D) distribution of the regional change in thickness and the elasticity. The obtained incremental elastic modulus coincides with that determined by the static pressure-strain test. Furthermore, in an in vitro experiment performed on an extracted human iliac artery, the 2-D distribution of elasticity is obtained and compared with pathological results.

Mita, Hitoshi; Kanai, Hiroshi; Koiwa, Yoshiro; Ichiki, Masataka; Tezuka, Fumiaki

2001-07-01

329

Hepatocellular carcinoma associated with budd-chiari syndrome: imaging features and transcatheter arterial chemoembolization  

PubMed Central

Background Budd–Chiari syndrome (BCS) often leads to hepatocellular carcinoma (HCC). Transcatheter arterial chemoembolization (TACE) has been increasingly used to treat BCS patients with HCC. The purposes of this study were to illustrate imaging features in BCS patients with HCC, and to analyze the effects of TACE on BCS patients with HCC. Methods 246 consecutive patients with primary BCS were retrospectively studied. 14 BCS patients with HCC were included in this study. BCS were treated with angioplasty and/or stenting, and HCC were managed with TACE. Imaging features on ultrasonography, CT, MRI, and angiography and the serum AFP level were analyzed. Results Inferior vena cava block and stricture of hepatic venous outflow tract more frequently occurred. Portal vein invasion was found in only 2 patients (14.2%). Imaging studies showed that most nodules of HCC were near the edge of liver, irregular, more than 3 cm in diameter, heterogeneous mass and solitary (?3 nodules). HCC in patients associated with BCS was isointense or hypointense in nonenhanced CT images, and exhibited heterogeneous enhancement during the arterial phase and washout during the portal venous phase on enhanced CT and MRI. The serum AFP level significantly declined after TACE treatment. Conclusions BCS patients with inferior vena cava block and stricture of hepatic venous outflow tract seems to be associated with HCC. A single, large, irregular nodule with a peripheral location appears to be HCC. TACE can effectively treat HCC in BCS patients.

2013-01-01

330

Molecular Imaging of Bone Marrow Mononuclear Cell Survival and Homing in Murine Peripheral Artery Disease  

PubMed Central

Introduction Bone marrow mononuclear cell (MNC) therapy is a promising treatment for peripheral artery disease (PAD). This study aims to provide insight into cellular kinetics using molecular imaging following different transplantation methods. Methods and Results MNCs were isolated from F6 transgenic mice (FVB background) that express firefly luciferase (Fluc) and green fluorescence protein (GFP). Male FVB and C57Bl6 mice (n=50) underwent femoral artery ligation and were randomized into 4 groups receiving: (1) single intramuscular (i.m.) injection of 2×106 MNC; (2) four weekly i.m. injections of 5×105 MNC; (3) 2×106 MNCs intravenously (i.v.); and (4) PBS. Cellular kinetics, measured by in vivo bioluminescence imaging (BLI), revealed near-complete donor cell death 4 weeks after i.m. transplantation. Following i.v. transplantation, BLI monitored cells homed in on the injured area in the limb, as well as to the liver, spleen, and bone marrow. Ex vivo BLI showed presence of MNCs in the scar tissue and adductor muscle. However, no significant effects on neovascularisation were observed as monitored by Laser-Doppler-Perfusion-Imaging and histology. Conclusion This is one of the first studies to assess kinetics of transplanted MNCs in PAD using in vivo molecular imaging. MNC survival is short lived and MNCs do not significantly stimulate perfusion in this model.

van der Bogt, Koen E.A.; Hellingman, Alwine A.; Lijkwan, Maarten A.; Bos, Ernst-Jan; de Vries, Margreet R.; Fischbein, Michael P.; Quax, Paul H.; Robbins, Robert C.; Hamming, Jaap F.; Wu, Joseph C.

2013-01-01

331

Automated classification of patients with coronary artery disease using grayscale features from left ventricle echocardiographic images.  

PubMed

Coronary Artery Disease (CAD), caused by the buildup of plaque on the inside of the coronary arteries, has a high mortality rate. To efficiently detect this condition from echocardiography images, with lesser inter-observer variability and visual interpretation errors, computer based data mining techniques may be exploited. We have developed and presented one such technique in this paper for the classification of normal and CAD affected cases. A multitude of grayscale features (fractal dimension, entropies based on the higher order spectra, features based on image texture and local binary patterns, and wavelet based features) were extracted from echocardiography images belonging to a huge database of 400 normal cases and 400 CAD patients. Only the features that had good discriminating capability were selected using t-test. Several combinations of the resultant significant features were used to evaluate many supervised classifiers to find the combination that presents a good accuracy. We observed that the Gaussian Mixture Model (GMM) classifier trained with a feature subset made up of nine significant features presented the highest accuracy, sensitivity, specificity, and positive predictive value of 100%. We have also developed a novel, highly discriminative HeartIndex, which is a single number that is calculated from the combination of the features, in order to objectively classify the images from either of the two classes. Such an index allows for an easier implementation of the technique for automated CAD detection in the computers in hospitals and clinics. PMID:23958645

Acharya, U Rajendra; Sree, S Vinitha; Muthu Rama Krishnan, M; Krishnananda, N; Ranjan, Shetty; Umesh, Pai; Suri, Jasjit S

2013-08-16

332

Quantification of carotid arteries atherosclerosis using 3D ultrasound images and area-preserving flattened maps  

NASA Astrophysics Data System (ADS)

Quantitative measurements of the progression (or regression) of carotid plaque burden are important in monitoring patients and evaluating new treatment options. 3D ultrasound (US) has been used to monitor the progression of carotid artery plaques in symptomatic and asymptomatic patients. Different methods of measuring various ultrasound phenotypes of atherosclerosis have been developed. In this work, we extended concepts used in intima-media thickness (IMT) measurements based on 2D images and introduced a metric called 3D vessel-wall-plus-plaque thickness (3D VWT), which was obtained by computing the distance between the carotid wall and lumen surfaces on a point-by-point basis in a 3D image of the carotid arteries. The VWT measurements were then superimposed on the arterial wall to produce the VWT map. Since the progression of plaque thickness is important in monitoring patients who are at risk for stroke, we also computed the change of VWT by comparing the VWT maps obtained for a patient at two different time points. In order to facilitate the visualization and interpretation of the 3D VWT and VWT-Change maps, we proposed a technique to flatten these maps in an area-preserving manner.

Chiu, Bernard; Egger, Micaela; Spence, J. David; Parraga, Grace; Fenster, Aaron

2008-04-01

333

Image quality assessment based on multiscale geometric analysis.  

PubMed

Reduced-reference (RR) image quality assessment (IQA) has been recognized as an effective and efficient way to predict the visual quality of distorted images. The current standard is the wavelet-domain natural image statistics model (WNISM), which applies the Kullback-Leibler divergence between the marginal distributions of wavelet coefficients of the reference and distorted images to measure the image distortion. However, WNISM fails to consider the statistical correlations of wavelet coefficients in different subbands and the visual response characteristics of the mammalian cortical simple cells. In addition, wavelet transforms are optimal greedy approximations to extract singularity structures, so they fail to explicitly extract the image geometric information, e.g., lines and curves. Finally, wavelet coefficients are dense for smooth image edge contours. In this paper, to target the aforementioned problems in IQA, we develop a novel framework for IQA to mimic the human visual system (HVS) by incorporating the merits from multiscale geometric analysis (MGA), contrast sensitivity function (CSF), and the Weber's law of just noticeable difference (JND). In the proposed framework, MGA is utilized to decompose images and then extract features to mimic the multichannel structure of HVS. Additionally, MGA offers a series of transforms including wavelet, curvelet, bandelet, contourlet, wavelet-based contourlet transform (WBCT), and hybrid wavelets and directional filter banks (HWD), and different transforms capture different types of image geometric information. CSF is applied to weight coefficients obtained by MGA to simulate the appearance of images to observers by taking into account many of the nonlinearities inherent in HVS. JND is finally introduced to produce a noticeable variation in sensory experience. Thorough empirical studies are carried out upon the LIVE database against subjective mean opinion score (MOS) and demonstrate that 1) the proposed framework has good consistency with subjective perception values and the objective assessment results can well reflect the visual quality of images, 2) different transforms in MGA under the new framework perform better than the standard WNISM and some of them even perform better than the standard full-reference IQA model, i.e., the mean structural similarity index, and 3) HWD performs best among all transforms in MGA under the framework. PMID:19447715

Gao, Xinbo; Lu, Wen; Tao, Dacheng; Li, Xuelong

2009-05-12

334

Assessment of single vessel coronary artery disease: results of exercise electrocardiography, thallium-201 myocardial perfusion imaging and radionuclide angiography  

SciTech Connect

The sensitivity of the commonly used stress tests for the diagnosis of coronary artery disease was analyzed in 46 patients with significant occlusion (greater than or equal to 70% luminal diameter obstruction) of only one major coronary artery and no prior myocardial infarction. In all patients, thallium-201 perfusion imaging (both planar and seven-pinhole tomographic) and 12 lead electrocardiography were performed during the same graded treadmill exercise test and radionuclide angiography was performed during upright bicycle exercise. Exercise rate-pressure (double) product was 22,307 +/- 6,750 on the treadmill compared with 22,995 +/- 5,622 on the bicycle (p = NS). Exercise electrocardiograms were unequivocally abnormal in 24 patients (52%). Qualitative planar thallium images were abnormal in 42 patients (91%). Quantitative analysis of the tomographic thallium images were abnormal in 41 patients (89%). An exercise ejection fraction of less than 0.56 or a new wall motion abnormality was seen in 30 patients (65%). Results were similar for the right (n = 11) and left anterior descending (n = 28) coronary arteries while all tests but the planar thallium imaging showed a lower sensitivity for isolated circumflex artery disease (n = 7). The specificity of the tests was 72, 83, 89 and 72% for electrocardiography, planar thallium imaging, tomographic thallium imaging and radionuclide angiography, respectively. The results suggest that exercise thallium-201 perfusion imaging is the most sensitive noninvasive stress test for the diagnosis of single vessel coronary artery disease.

Port, S.C.; Oshima, M.; Ray, G.; McNamee, P.; Schmidt, D.H.

1985-07-01

335

Evaluation of image quality characteristics of reduction image in high resolution liquid crystal display  

NASA Astrophysics Data System (ADS)

With recent developments, digital mammograms can be obtained with a small pixel size, i.e., high resolution; however, the matrix size increases. Therefore, when the image is thinned out, image information is lost when the image is displayed on a liquid crystal display (LCD). To resolve this issue, we have developed a super high resolution liquid crystal display (SHR-LCD) by using a novel resolution enhancement technology for independent subpixel driving (ISD) with three subpixels in each pixel element. However, the lack of image information caused by thinning of the image cannot be ignored because the matrix size of a phase contrast mammogram (PCM) is very large as compared to that of a conventional mammogram. We obtained noise and edge images by using the geometrical layouts of the PCM (7080 x 9480). We measured the Wiener spectrum (WS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) of the images reduced by the nearest-neighbor, bilinear, and bicubic (sharpness and smooth) interpolations. The reduction rate was approximately 0.14. We measured the WS and MTF when the PCM image was displayed on a 5-megapixel (MP) and 15-MP LCD. The bilinear interpolation technique gave the best image quality. The image quality was further improved by using a 15-MP SHR-LCD.

Kimura, Yukiyoshi; Yokoyama, Daigo; Fujita, Naotoshi; Kodera, Yoshie

2011-03-01

336

Reducing the absorbed dose in analogue radiography of infant chest images by improving the image quality, using image processing techniques.  

PubMed

Radiographic inspection is one of the most widely employed techniques for medical testing methods. Because of poor contrast and high un-sharpness of radiographic image quality in films, converting radiographs to a digital format and using further digital image processing is the best method of enhancing the image quality and assisting the interpreter in their evaluation. In this research work, radiographic films of 70 infant chest images with different sizes of defects were selected. To digitise the chest images and employ image processing the two algorithms (i) spatial domain and (ii) frequency domain techniques were used. The MATLAB environment was selected for processing in the digital format. Our results showed that by using these two techniques, the defects with small dimensions are detectable. Therefore, these suggested techniques may help medical specialists to diagnose the defects in the primary stages and help to prevent more repeat X-ray examination of paediatric patients. PMID:21743073

Karimian, A; Yazdani, S; Askari, M A

2011-07-09

337

Effect of exercise supplementation on dipyridamole thallium-201 image quality  

SciTech Connect

To determine the effect of different types of exercise supplementation on dipyridamole thallium image quality, 78 patients were prospectively randomized to one of three protocols: dipyridamole infusion alone, dipyridamole supplemented with isometric handgrip, and dipyridamole with low-level treadmill exercise. Heart-to-lung, heart-to-liver, and heart-to-adjacent infradiaphragmatic activity ratios were generated from anterior images acquired immediately following the test. Additionally, heart-to-total infradiaphragmatic activity was graded semiquantitatively. Results showed a significantly higher ratio of heart to subdiaphragmatic activity in the treadmill group as compared with dipyridamole alone (p less than 0.001) and dipyridamole supplemented with isometric handgrip exercise (p less than 0.001). No significant difference was observed between patients receiving the dipyridamole infusion, and dipyridamole supplemented with isometric handgrip exercise. The authors conclude that low-level treadmill exercise supplementation of dipyridamole infusion is an effective means of improving image quality. Supplementation with isometric handgrip does not improve image quality over dipyridamole alone.

Stern, S.; Greenberg, I.D.; Corne, R. (Health Sciences Centre, Winnipeg, Manitoba (Canada))

1991-08-01

338

TL dosimetry for quality control of CR mammography imaging systems  

NASA Astrophysics Data System (ADS)

The aim of this work is to estimate the average glandular dose with thermoluminescent (TL) dosimetry and comparison with quality imaging in computed radiography (CR) mammography. For a measuring dose, the Food and Drug Administration (FDA) and the American College of Radiology (ACR) use a phantom, so that dose and image quality are assessed with the same test object. The mammography is a radiological image to visualize early biological manifestations of breast cancer. Digital systems have two types of image-capturing devices, full field digital mammography (FFDM) and CR mammography. In Mexico, there are several CR mammography systems in clinical use, but only one system has been approved for use by the FDA. Mammography CR uses a photostimulable phosphor detector (PSP) system. Most CR plates are made of 85% BaFBr and 15% BaFI doped with europium (Eu) commonly called barium flourohalideE We carry out an exploratory survey of six CR mammography units from three different manufacturers and six dedicated X-ray mammography units with fully automatic exposure. The results show three CR mammography units (50%) have a dose greater than 3.0 mGy without demonstrating improved image quality. The differences between doses averages from TLD system and dosimeter with ionization chamber are less than 10%. TLD system is a good option for average glandular dose measurement for X-rays with a HVL (0.35-0.38 mmAl) and kVp (24-26) used in quality control procedures with ACR Mammography Accreditation Phantom.

Gaona, E.; Nieto, J. A.; Góngora, J. A. I. D.; Arreola, M.; Enríquez, J. G. F.

339

No-reference image quality assessment in the spatial domain.  

PubMed

We propose a natural scene statistic-based distortion-generic blind/no-reference (NR) image quality assessment (IQA) model that operates in the spatial domain. The new model, dubbed blind/referenceless image spatial quality evaluator (BRISQUE) does not compute distortion-specific features, such as ringing, blur, or blocking, but instead uses scene statistics of locally normalized luminance coefficients to quantify possible losses of "naturalness" in the image due to the presence of distortions, thereby leading to a holistic measure of quality. The underlying features used derive from the empirical distribution of locally normalized luminances and products of locally normalized luminances under a spatial natural scene statistic model. No transformation to another coordinate frame (DCT, wavelet, etc.) is required, distinguishing it from prior NR IQA approaches. Despite its simplicity, we are able to show that BRISQUE is statistically better than the full-reference peak signal-to-noise ratio and the structural similarity index, and is highly competitive with respect to all present-day distortion-generic NR IQA algorithms. BRISQUE has very low computational complexity, making it well suited for real time applications. BRISQUE features may be used for distortion-identification as well. To illustrate a new practical application of BRISQUE, we describe how a nonblind image denoising algorithm can be augmented with BRISQUE in order to perform blind image denoising. Results show that BRISQUE augmentation leads to performance improvements over state-of-the-art methods. A software release of BRISQUE is available online: http://live.ece.utexas.edu/research/quality/BRISQUE_release.zip for public use and evaluation. PMID:22910118

Mittal, Anish; Moorthy, Anush Krishna; Bovik, Alan Conrad

2012-08-17

340

Intravascular laser speckle imaging catheter for the mechanical evaluation of the arterial wall  

PubMed Central

Laser speckle imaging (LSI) is a novel technique for measuring the mechanical properties of atherosclerotic plaques. In LSI, the decorrelation time constant of speckle intensity fluctuations provides an index of viscoelasticity that is closely related to plaque microstructure and composition. Here, we demonstrate for the first time, the feasibility of conducting LSI in vivo using a prototype 1.5 mm (4.5 Fr) diameter intravascular catheter. Investigation of the catheter performance using human arterial samples ex vivo shows that plaque time constants measured by the LSI catheter correlate well with those measured using a free-space bulk optics system. To demonstrate LSI in vivo, the catheter is interfaced with a portable console for intravascular evaluation in the aorta of a living rabbit. Distinct differences in arterial time constants are identified at normal aortic and stented sites in vivo with intravascular LSI.

Hajjarian, Zeinab; Xi, Jingqun; Jaffer, Farouc A.; Tearney, Guillermo J.; Nadkarni, Seemantini K.

2011-01-01

341

Differentiating atherosclerotic plaque burden in arterial tissues using femtosecond CARS-based multimodal nonlinear optical imaging  

PubMed Central

A femtosecond CARS-based nonlinear optical microscope was used to simultaneously image extracellular structural proteins and lipid-rich structures within intact aortic tissue obtained from myocardial infarction-prone Watanabe heritable hyperlipidemic rabbits (WHHLMI). Clear differences in the NLO microscopic images were observed between healthy arterial tissue and regions dominated by atherosclerotic lesions. In the current ex-vivo study, we present a single parameter based on intensity changes derived from multi-channel NLO image to classify plaque burden within the vessel. Using this parameter we were able to differentiate between healthy regions of the vessel and regions with plaque, as well as distinguish plaques relative to the age of the WHHLMI rabbit.

Mostaco-Guidolin, Leila B.; Sowa, Michael G.; Ridsdale, Andrew; Pegoraro, Adrian F.; Smith, Michael S. D.; Hewko, Mark D.; Kohlenberg, Elicia K.; Schattka, Bernie; Shiomi, Masashi; Stolow, Albert; Ko, Alex C.-T.

2010-01-01

342

Radiation dose in cardiac CT angiography: protocols and image quality.  

PubMed

This paper aims to evaluate the radiation dose exposure of patients submitted to cardiac computed tomography angiography. The effective dose was obtained from the product of dose-length product values and the conversion factor established in the European Working Group for Guidelines on Quality Criteria in CT. The image noise and contrast- and signal-to-noise ratios were obtained for all images. Sixty-four- and 256-slice CT angiographies were used in 211 (68.5 %) and 97 (31.5 %) patients, respectively. The calculated mean effective dose with prospective CT angiography was 6.0±1.0 mSv and the retrospective mode was 8.4±1.2 mSv. The mean image noise values were 38.5±9.5 and 21.4 ± 5.3 for prospective and retrospective modes, respectively. It was observed that the image noise increased by 44.4 % using a prospective mode. Prospective CT angiography reduces radiation dose by ?29 % compared with the retrospective mode, while maintaining diagnostic image quality and the ability to assess obstructions in patients. PMID:23235799

Oliveira, L C G; Gottlieb, I; Rizzi, P; Lopes, R T; Kodlulovich, S

2012-12-12

343

The Relationships Between Regional Arterial Inflammation, Calcification, Risk Factors and Biomarkers - A Prospective FDG PET/CT Imaging Study  

PubMed Central

Background Fluorodeoxyglucose positron emission tomography (FDG PET) imaging of atherosclerosis has been used to quantify plaque inflammation and to measure the effect of plaque stabilizing drugs. Here we explore how atherosclerotic plaque inflammation varies across arterial territories and how it relates to arterial calcification. We also test the hypotheses that the degree of local arterial inflammation measured by PET is correlated with the extent of systemic inflammation and presence of risk factors for vascular disease. Methods and Results Forty-one subjects underwent vascular PET/CT imaging with FDG. All had either vascular disease or multiple risk factors for it. Forty subjects underwent carotid imaging, twenty-seven underwent aortic, twenty-four iliac and thirteen femoral imaging. Thirty-three subjects had a panel of biomarkers analyzed. We found strong associations between FDG uptake in neighboring arteries (left vs. right carotid r=0.91, p<0.001, ascending aorta vs. aortic arch r=0.88, p<0.001). Calcification and inflammation rarely overlapped within arteries – carotid artery FDG uptake vs. calcium score r=?0.42, p=0.03). Carotid artery FDG uptake was greater in those with a history of coronary artery disease (target to background ratio (TBR) 1.83 vs. 1.61, p<0.01), and in males vs. females (TBR 1.83 vs. 1.63, p<0.05). Similar findings were also noted in the aorta and iliac arteries. Subjects with the highest levels of FDG uptake also had the greatest concentrations of inflammatory biomarkers: descending aorta TBR vs. matrix metalloproteinase 3 (MMP 3): r=0.53, p=0.01 and carotid TBR vs. MMP 9: r=0.50, p=0.01. Non-significant positive trends were seen between FDG uptake and levels of interleukin 18, fibrinogen and C-reactive protein. Finally, we found that the atheroprotective biomarker adiponectin was negatively correlated with the degree of arterial inflammation in the descending aorta: r=?0.49, p=0.03). Conclusions This study shows that FDG PET imaging can increase our knowledge of how atherosclerotic plaque inflammation relates to calcification, serum biomarkers and vascular risk factors. Plaque inflammation and calcification rarely overlap, supporting the theory that calcification represents a late, burnt-out stage of atherosclerosis. Inflammation in one arterial territory is associated with inflammation elsewhere, and the degree of local arterial inflammation is reflected in the blood levels of several circulating biomarkers. We suggest that FDG PET imaging could be used as a surrogate marker of both atherosclerotic disease activity and drug effectiveness. Prospective, event driven studies are now underway to determine the role of this technique in clinical risk prediction.

Rudd, James HF; Myers, Kelly S; Bansilal, Sameer; Machac, Josef; Woodward, Mark; Fuster, Valentin; Farkouh, Michael E; Fayad, Zahi A

2011-01-01

344

High-Resolution 3 T MR Microscopy Imaging of Arterial Walls  

SciTech Connect

Purpose. To achieve a high spatial resolution in MR imaging that allows for clear visualization of anatomy and even histology and documentation of plaque morphology in in vitro samples from patients with advanced atherosclerosis. A further objective of our study was to evaluate whether T2-weighted high-resolution MR imaging can provide accurate classification of atherosclerotic plaque according to a modified American Heart Association classification. Methods. T2-weighted images of arteries were obtained in 13 in vitro specimens using a 3 T MR unit (Medspec 300 Avance/Bruker, Ettlingen, Germany) combined with a dedicated MR microscopy system. Measurement parameters were: T2-weighted sequences with TR 3.5 sec, TE 15-120 msec; field of view (FOV) 1.4 x 1.4; NEX 8; matrix 192; and slice thickness 600 {mu}m. MR measurements were compared with corresponding histologic sections. Results. We achieved excellent spatial and contrast resolution in all specimens. We found high agreement between MR images and histology with regard to the morphology and extent of intimal proliferations in all but 2 specimens. We could differentiate fibrous caps and calcifications from lipid plaque components based on differences in signal intensity in order to differentiate hard and soft atheromatous plaques. Hard plaques with predominantly intimal calcifications were found in 7 specimens, and soft plaques with a cholesterol/lipid content in 5 cases. In all specimens, hemorrhage or thrombus formation, and fibrotic and hyalinized tissue could be detected on both MR imaging and histopathology. Conclusion. High-resolution, high-field MR imaging of arterial walls demonstrates the morphologic features, volume, and extent of intimal proliferations with high spatial and contrast resolution in in vitro specimens and can differentiate hard and soft plaques.

Sailer, Johannes, E-mail: johannes.sailer@univie.ac.at; Rand, Thomas [University of Vienna, Department of Angiography and Interventional Radiology (Austria); Berg, Andreas [University of Vienna, Institute for Medical Physics (Austria); Sulzbacher, Irene [University of Vienna, Clinical Institute of Pathology (Austria); Peloschek, P. [University of Vienna, Department of Angiography and Interventional Radiology (Austria); Hoelzenbein, Thomas [University of Vienna, Department of Surgery (Austria); Lammer, Johannes [University of Vienna, Department of Angiography and Interventional Radiology (Austria)

2006-10-15

345

Characterization of image quality and image-guidance performance of a preclinical microirradiator  

SciTech Connect

Purpose: To assess image quality and image-guidance capabilities of a cone-beam CT based small-animal image-guided irradiation unit (micro-IGRT). Methods: A micro-IGRT system has been developed in collaboration with the authors' laboratory as a means to study the radiobiological effects of conformal radiation dose distributions in small animals. The system, the X-Rad 225Cx, consists of a 225 kVp x-ray tube and a flat-panel amorphous silicon detector mounted on a rotational C-arm gantry and is capable of both fluoroscopic x-ray and cone-beam CT imaging, as well as image-guided placement of the radiation beams. Image quality (voxel noise, modulation transfer, CT number accuracy, and geometric accuracy characteristics) was assessed using water cylinder and micro-CT test phantoms. Image guidance was tested by analyzing the dose delivered to radiochromic films fixed to BB's through the end-to-end process of imaging, targeting the center of the BB, and irradiation of the film/BB in order to compare the offset between the center of the field and the center of the BB. Image quality and geometric studies were repeated over a 5-7 month period to assess stability. Results: CT numbers reported were found to be linear (R{sup 2}{>=}0.998) and the noise for images of homogeneous water phantom was 30 HU at imaging doses of approximately 1 cGy (to water). The presampled MTF at 50% and 10% reached 0.64 and 1.35 mm{sup -1}, respectively. Targeting accuracy by means of film irradiations was shown to have a mean displacement error of [{Delta}x,{Delta}y,{Delta}z]=[-0.12,-0.05,-0.02] mm, with standard deviations of [0.02, 0.20, 0.17] mm. The system has proven to be stable over time, with both the image quality and image-guidance performance being reproducible for the duration of the studies. Conclusions: The micro-IGRT unit provides soft-tissue imaging of small-animal anatomy at acceptable imaging doses ({<=}1 cGy). The geometric accuracy and targeting systems permit dose placement with submillimeter accuracy and precision. The system has proven itself to be stable over 2 yr of routine laboratory use (>1800 irradiations) and provides a platform for the exploration of targeted radiation effects in small-animal models.

Clarkson, R.; Lindsay, P. E.; Ansell, S.; Wilson, G.; Jelveh, S.; Hill, R. P.; Jaffray, D. A. [Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada); Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada) and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 1A1 (Canada); Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5 2M9 (Canada); Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada) and Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5S 1A1 (Canada) and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 1A1 (Canada); Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5S 1A1 (Canada) and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 1A1 (Canada)

2011-02-15

346

Measuring image quality performance on image versions saved with different file format and compression ratio  

NASA Astrophysics Data System (ADS)

Digitization of existing documents containing images is an important body of work for many archives ranging from individuals to institutional organizations. The methods and file formats used in this digitization is usually a trade off between budget, file volume size and image quality, while not necessarily in this order. The use of most commons and standardized file formats, JPEG and TIFF, prompts the operator to decide the compression ratio that affects both the final file volume size and the quality of the resulting image version. The evaluation of the image quality achieved by a system can be done by means of several measures and methods, being the Modulation Transfer Function (MTF) one of most used. The methods employed by the compression algorithms affect in a different way the two basic features of the image contents, edges and textures. Those basic features are too differently affected by the amount of noise generated at the digitization stage. Therefore, the target used in the measurement should be related with the features usually presents in general imaging. This work presents a comparison between the results obtained by measuring the MTF of images taken with a professional camera system and saved in several file formats compression ratios. In order to accomplish with the needs early stated, the MTF measurement has been done by two separate methods using the slanted edge and dead leaves targets respectively. The measurement results are shown and compared related with the respective file volume size.

Mitjà, Carles; Escofet, Jaume; Bover, Toni

2012-05-01

347

Edge patterns extracted from natural images and their statistics for reduced-reference image quality assessment  

NASA Astrophysics Data System (ADS)

Image quality assessment (IQA) aims to predict perceived image quality consistently with the corresponding subjective perceptual quality. Searching for features efficiently representing natural images and investigating their statistics are the fundamentals in the task of IQA models design. In this context, we have proposed previously a novel reduced reference (RR) IQA model in which groups of the named edge patterns are good to represent the local distribution of the zero-crossings both for natural images and their distorted counterpart, and then proposed a RR IQA model. In this paper, we focus on the issue of the interesting edge patterns related to natural images, i.e., what are the edge patterns good at representing ZC distribution of natural images? And how should we do to use them for IQA model design? Along those ideas, we extract 39 groups of edge patterns from 110 natural pictures by a defined curvature rule. Combined with error tolerance, the 39 groups of edge patterns can well represent the ZC distribution of both the reference and distortion images. Based on them, a RR IQA model is built on the statistical analysis of the selected edge patterns. Experimental results show that the proposed model works fairly good compared to its competitor.

Shao, Wenting; Mou, Xuanqin

2013-01-01

348

Intravascular ultrasound imaging of angiographically normal coronary arteries: a prospective study in vivo.  

PubMed Central

Intravascular ultrasound imaging (IVUS) was performed to elucidate the discrepancy between clinical history and angiographic findings and to measure the diameter and area of the lumen of the normal left coronary artery in 55 patients who presented with chest pain but had normal coronary angiograms. The left coronary artery (LCA) was scanned with a 4.8F, 20 MHz mechanically rotated ultrasound catheter at 413 sites. Atherosclerotic lesions were identified at 72 (17%) sites in 25 patients. The mean (SD) (range) plaque area was 5.55 (3.56) mm2 (2-26 mm2) and it occupied 28.8 (9.6)% (13-70%) of the coronary cross sectional area. Calcification was detected at 24 (33%) atherosclerotic sites in nine patients. The correlation coefficients for the lumen dimensions measured at normal sites by IVUS and by angiography were r = 0.93 (SEE = 0.43) mm for lumen diameter and r = 0.89 (SEE = 4.27) mm2 for lumen area (both p < 0.001). 16 of the 30 patients in whom no atherosclerotic plaques were detected in the LCA lumen by IVUS had no risk factors of coronary artery disease. The cross sectional area of 90 consecutive images of left main coronary artery (LMCA), proximal left anterior descending coronary artery (proximal LAD), and mid LAD was measured in these 16 subjects. The mean (SEM) areas at end diastole were LMCA 17.33 (7.98) mm2; proximal LAD 13.56 (5.85) mm2; mid LAD 9.75 (4.67) mm2. During the cardiac cycle the cross sectional area changed by 10.2 (4.0)% in the LMCA, by 8.3 (4.7)% in the proximal LAD, and by 9.8 (4.0)% in the mid LAD. In 11 patients with plagues the change in cross sectional area in plague segments (5.8(3.1)%) was significantly lower than in the segments from patients without plagues (p < 0.001). Lumen area reached a maximum in early diastole rather than in late diastole. IVUS can imagine atherosclerotic lesions that are angiographically silent; it also provides detailed information about plague characteristics. The variation in coronary cross sectional area during the cardiac cycle should not be ignored during quantitative analysis. Maximum dimensions in normal segments are reached in early diastole. Further studies are needed to clarify the clinical significance of atherosclerosis detected by IVUS in patients presenting with chest pain but normal coronary angiography. Images

Ge, J.; Erbel, R.; Gerber, T.; Gorge, G.; Koch, L.; Haude, M.; Meyer, J.

1994-01-01

349

Food pattern and quality of life in metabolic syndrome patients who underwent coronary artery bypass grafting in Taiwan  

Microsoft Academic Search

Metabolic syndrome is associated with poor operative outcomes of coronary artery bypass grafting surgery (CABG). A healthy food pattern for metabolic syndrome patients is necessary not only in the initial stage to prevent cardiovascular disease but for those who experience cardiovascular problems and undergo heart surgery. Empirical studies that explore food pattern and quality of life metabolic syndrome patients who

Heng-Hsin Tung; Li-Hua Tseng; Jeng Wei; Cheng-Hsin Lin; Tsae-Jyy Wang; Shu-Yuan Liang

2011-01-01

350

The impact of temporal inaccuracies on 4DCT image quality  

SciTech Connect

Accurate delineation of target volumes is one of the critical components contributing to the success of image-guided radiotherapy treatments and several imaging modalities are employed to increase the accuracy in target identification. Four-dimensional (4D) techniques are incorporated into existing radiation imaging techniques like computed tomography (CT) to account for the mobility of the target volumes. However, these methods in some cases introduce further inaccuracies in the target delineation when further quality assurance measures are not implemented. A source of commonly observed inaccuracy is the misidentification of the respiration cycles and resulting respiration phase assignments used in the construction of the 4D patient model. The aim of this work is to emphasize the importance of optimal respiration phase assignment during the 4DCT image acquisition process and to perform a quantitative assessment of the effect of inaccurate phase assignments on the overall image quality. The accuracy of the phase assignment was assessed by comparison with an independent calculation of the respiration phases. Misplaced phase assignments manifest themselves as deformations and artifacts in reconstructed images. These effects are quantified as volumetric discrepancies in the localization of target objects represented by spherical phantoms. Measurements are performed using a fully programmable motion phantom designed and built at Mayo Clinic (Rochester, MN). Implementation of a case based independent check and correction procedure is also demonstrated with emphasis on the use of this procedure in the clinical environment. Review of clinical 4D scans performed in this institution showed discrepancies in the phase assignments in about 40% of the cases when compared to our independent calculations. It is concluded that for improved image reconstruction, an independent check of the sorting procedure should be performed for each clinical 4DCT case.

Mutaf, Y. D.; Antolak, J. A.; Brinkmann, D. H. [Radiation Oncology Department, Mayo Clinic, 200 1st Street SW. Rochester, Minnesota 55905 (United States)

2007-05-15

351

Impact of hypertension on the accuracy of exercise stress myocardial perfusion imaging for the diagnosis of coronary artery disease  

Microsoft Academic Search

AIMTo compare the accuracy of exercise stress myocardial perfusion single photon emission computed tomography (SPECT) imaging for the diagnosis of coronary artery disease in patients with and without hypertension.METHODSA symptom limited bicycle exercise stress test in conjunction with 99m technetium sestamibi or tetrofosmin SPECT imaging was performed in 332 patients (mean (SD) age, 57 (10) years; 257 men, 75 women)

A Elhendy; R T van Domburg; F B Sozzi; D Poldermans; J J Bax; J R T C Roelandt

2001-01-01

352

Direct comparison of fluorodeoxyglucose positron emission tomography and arterial spin labeling magnetic resonance imaging in Alzheimer’s disease  

Microsoft Academic Search

BackgroundThe utility of fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in Alzheimer’s disease (AD) diagnosis has been well established. Recently, measurement of cerebral blood flow using arterial spin labeling magnetic resonance imaging (ASL-MRI) has shown diagnostic potential in AD, although it has never been directly compared with FDG-PET.

Erik S. Musiek; Yufen Chen; Marc Korczykowski; Babak Saboury; Patricia M. Martinez; Janet S. Reddin; Abass Alavi; Daniel Y. Kimberg; David A. Wolk; Per Julin; Andrew B. Newberg; Steven E. Arnold; John A. Detre

353

A new algorithm for integrated image quality measurement based on wavelet transform and human visual system  

NASA Astrophysics Data System (ADS)

An essential determinant of the value of digital images is their quality. Over the past years, there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image quality. This paper proposes a reliable automatic method for objective image quality measurement by wavelet transform and Human visual system. This way the proposed measure differentiates between the random and signal-dependant distortion, which have different effects on human observer. Performance of the proposed quality measure is illustrated by examples involving images with different types of degradation. The technique provides a means to relate the quality of an image to the interpretation and quantification throughout the frequency range, in which the noise level is estimated for quality evaluation. The experimental results of using this method for image quality measurement exhibit good correlation to subjective visual quality assessments.

Wang, Haihui

2006-01-01

354

System for evaluating the image quality of lenses and cameras  

NASA Astrophysics Data System (ADS)

This paper describes an automatic system for evaluating the photographic resolution from the information maximum. The technical characteristics of the system are presented, along with comparative data on errors in evaluating resolution by visual and informational methods. It is shown that the informational method of evaluating the image quality enhances the accuracy with which the resolution is determined, eliminates the consumption of photographic materials, and decreases the difficulty of the measurement process.

Barteneva, O. A.; Butyaikin, V. I.; Kalugin, D. E.; Reshetkina, I. V.

1994-02-01

355

Aspects of iris image and iris match pair quality  

NASA Astrophysics Data System (ADS)

Iris recognition technology has the potential to broaden to include non-ideal imaging situations, as well as scale to national-level deployments. Hence, the study of population factors, subject intrinsics, and sensing contexts that can individually or collectively impact iris recognition performance assumes increased importance. This presentation summarizes recent research on a number of such "quality variables" and motivates the need for large data sets exhibiting a variety of such non-idealities to adequately characterize performance.

Flynn, Patrick J.; Bowyer, Kevin W.

2010-04-01

356

Label-free imaging of arterial tissues using photonic crystal fiber (PCF) based nonlinear optical microscopic system  

NASA Astrophysics Data System (ADS)

Nonlinear optical (NLO) microscopy provides a minimally invasive optical method for fast molecular imaging at subcellular resolution with 3D sectioning capability in thick, highly scattering biological tissues. In the current study, we demonstrate the imaging of arterial tissue using a nonlinear optical microscope based on photonic crystal fiber and a single femto-second oscillator operating at 800nm. This NLO microscope system is capable of simultaneous imaging extracellular elastin/collagen structures and lipid distribution within aortic tissue obtained from coronary atherosclerosis-prone WHHLMI rabbits (Watanabe heritable hyperlipidemic rabbit-myocardial infarction) Clear pathological differences in arterial lumen surface were observed between healthy arterial tissue and atherosclerotic lesions through NLO imaging.

Ko, Alex C. T.; Ridsdale, Andrew; Pegoraro, Adrian F.; Smith, Michael S. D.; Mostaço-Guidolin, Leila B.; Hewko, Mark D.; Kohlenberg, Elicia M.; Schattka, Bernie J.; Shiomi, Masashi; Stolow, Albert; Sowa, Michael G.

2009-02-01

357

Image-quality assessment method for digital phase-contrast imaging based on two-dimensional power spectral analysis.  

PubMed

With use of the phase shift of X-rays that occurs when they pass through an object, phase-contrast imaging (herein referred to as "phase imaging") can produce images different from those of conventional contact imaging (herein referred to as "conventional imaging"). For this reason, assessment of the image quality based on noise-equivalent quanta (NEQ) and detective quantum efficiency (DQE) which does not include object-based information may not be appropriate for comparison of image quality between phase and conventional images. As an alternative method, we conceived a new image-quality assessment method with images that contain information about an object. First, we constructed images with an object and without an object under the same imaging parameters; then, we obtained two-dimensional power spectra by Fourier transform of those images. Second, we calculated the radial direction distribution function with the power spectra, and the distribution of signal intensity, which we defined as a signal intensity distribution function (SIDF). In this way, differences in image quality were evaluated relatively based on the SIDF of the imaged object. In our study, we first confirmed that phase-imaging evaluation was not appropriate by comparing NEQ and DQE of conventional, magnification, and phase imaging. Further, comparing the image quality of projected plant seeds by employing conventional, magnification, and phase imaging, we found that the phase-imaging method provided a higher image quality regarding edge sharpness than did conventional and magnification imaging. Therefore, based on these results, our image assessment method is considered useful for evaluation of images which include object-based information. PMID:22071600

Matsuo, Satoru; Morishita, Junji; Katafuchi, Tetsuro; Honda, Chika; Fujita, Hiroshi

2011-11-10

358

Effect of fabrication errors on binary optical element imaging quality  

NASA Astrophysics Data System (ADS)

Compared to conventional optical elements, the binary optical element (BOE) can not only revise aberration, but also reduce optical system's weight, miniaturize a system and increase the freedom of system design. Nowadays, we need to improve the manufacturing process before the industrialization of the BOE. However, the fabrication accuracy of BOE affects the imaging quality of the optical system. This paper analyzes the influence of fabrication errors on BOE's diffraction efficiency and transmission wavefront, to guide the processing and tolerance analysis of the optical systems design stage. Generally, in fabrication processes of the multiple-phase step BOE, there are alignment errors, linewidth errors and depth errors for various reasons. Due to the fabrication errors, the diffraction efficiency of the BOE would be reduced, thus stray light is introduced into the system. Besides, BOE graphical structure is also changed, then introduces wavefront aberrations to the optical imaging system, and thereby reduces the imaging quality of the system. Based on scalar diffraction theory, we have come to some conclusions like that the formula of wavefront PTV which can derive the fabrication requirements of alignment accuracy and linewidth accuracy; if 4-step BOE's linewidth errors are controlled within a certain range, diffraction efficiency declines little, however, when the linewidth errors exceed this range, the diffraction efficiency will decline rapidly; the influence of deep and shallow etching depth errors on the diffraction efficiency is equivalent, the influence of multiple etching depth errors on the diffraction efficiency is independent and symmetric, and so on. This article focuses on analyzing the fabrication requirements of BOE based on how the fabrication errors affect the diffraction efficiency and wavefront imaging quality of BOE, then guide the design and fabrication processes of BOE imaging optical systems.

Wang, Song; Yang, Wei; Wu, Shi-bin

2013-08-01

359

Imaging diagnosis--celiac artery pseudoaneurysm associated with a migrating grass awn.  

PubMed

The ultrasound and computed tomography findings of a retroperitoneal pseudoaneurysm associated with a grass awn are described in a 10-month-old dog. Ultrasound was used to localize the lesion and surrounding reaction as well as to determine its relationship with the celiac artery, but inadequate Doppler settings hindered the diagnosis of its vascular nature. Dual phase CT enabled further characterization, particularly its close relationship with the major retroperitoneal vessels. The imaging examination was fundamental in recommending nonsurgical therapy. The dog died as a consequence of the rupture of this pseudoaneurysm. A grass awn was confirmed. PMID:20973383

Llabrés-Díaz, Francisco J; Brissot, Hervé; Ibarrola, Patricia

360

Reduced reference image quality assessment based on statistics of edge  

NASA Astrophysics Data System (ADS)

Objective Image Quality Assessment (IQA) model investigation is a hot topic in recent times. This paper proposed a novel and efficient universal Reduced Reference (RR) image quality assessment method based upon the statistics of edge discrimination. Firstly, binary edge maps created from the multi-scale wavelet transform modulus maxima were used as the low level feature to discriminate the difference between the reference and distorted image for IQA purpose. Then the gradient operator was applied on the binary map to produce the so called edge pattern map. The histogram of edge pattern map was used to verify the pattern of the edges of reference and distorted image, respectively. The RR features extracted from the histogram was used to discriminate the difference of edge pattern maps, and then form a new RR IQA model. Comparing to the typical RR model (Zhou Wang's method, 2005), only 12 features (96 bits) are needed instead of 18 features (162 bits) in Zhou Wang et al.'s method with better overall performance.

Zhang, Min; Xue, Wufeng; Mou, Xuanqin

2011-01-01

361

Objective assessment of image quality. IV. Application to adaptive optics  

PubMed Central

The methodology of objective assessment, which defines image quality in terms of the performance of specific observers on specific tasks of interest, is extended to temporal sequences of images with random point spread functions and applied to adaptive imaging in astronomy. The tasks considered include both detection and estimation, and the observers are the optimal linear discriminant (Hotelling observer) and the optimal linear estimator (Wiener). A general theory of first- and second-order spatiotemporal statistics in adaptive optics is developed. It is shown that the covariance matrix can be rigorously decomposed into three terms representing the effect of measurement noise, random point spread function, and random nature of the astronomical scene. Figures of merit are developed, and computational methods are discussed.

Barrett, Harrison H.; Myers, Kyle J.; Devaney, Nicholas; Dainty, Christopher

2008-01-01

362

Blood supply of the main bile duct from the caudate artery and medial subsegmental artery of the hepatic artery: Evaluation using images obtained during transcatheter arterial chemoembolization for hepatocellular carcinoma.  

PubMed

AIM: Main bile duct necrosis develops after transcatheter arterial chemoembolization (TACE) through the caudate artery (A1) and medial subsegmental artery (A4) of the hepatic artery in the treatment of hepatocellular carcinoma. The aim of this study was to evaluate the bile duct branch (BD branch) from A1 and A4. METHODS: We evaluated the origin and vascular territory of the BD branch in 11 patients who underwent selective A1 and/or A4 arteriography using arteriograms, cone-beam computed tomography (CBCT) and CT obtained 1 week after TACE. Follow-up CT and/or magnetic resonance imaging were also evaluated. RESULTS: The BD branch arose from the first branch (n?=?4), the second branch (n?=?1), and both the first and second branches (n?=?1) of A1, and from the first branch of A4 (n?=?5). It supplied the bilateral hepatic ducts and common hepatic duct (CHD) (n?=?4), the right hepatic duct (RHD) and CHD (n?=?2), RHD, CHD and common bile duct (n?=?1), the left hepatic duct (LHD) and CHD (n?=?2), and LHD alone (n?=?2). Anastomosis between A1 or A4 and other branches was demonstrated in seven patients. Bile duct stricture developed in all nine patients 2-8 months after TACE of the BD branch and percutaneous transhepatic bile duct drainage and metallic stent placement was required in one because of jaundice. CONCLUSION: The BD branch arises from the proximal portion of A1 and A4 and mainly supplies the hepatic ducts and CHD. PMID:23387506

Miyayama, Shiro; Yamashiro, Masashi; Hashimoto, Masahiro; Hashimoto, Nanako; Ikuno, Masaya; Okumura, Kenichiro; Yoshida, Miki; Matsui, Osamu

2013-01-14

363

Imaging air quality evaluation based on Noise Brightness Ratio & Gompertz Type Diffusion Process  

Microsoft Academic Search

A novel air quality evaluation method, which only uses the surveillance image data, is presented in this paper. Since the intensity change of the Image Quality (IQ) can reflect the photography condition change of a CCD camera, the image can be used to evaluate the trend change of the air quality. In this paper, first a new IQ metric, which

Haoting Liu; Hanqing Lu

2010-01-01

364

Evaluation of scatter effects on image quality for breast tomosynthesis  

SciTech Connect

Digital breast tomosynthesis uses a limited number (typically 10-20) of low-dose x-ray projections to produce a pseudo-three-dimensional volume tomographic reconstruction of the breast. The purpose of this investigation was to characterize and evaluate the effect of scattered radiation on the image quality for breast tomosynthesis. In a simulation, scatter point spread functions generated by a Monte Carlo simulation method were convolved over the breast projection to estimate the distribution of scatter for each angle of tomosynthesis projection. The results demonstrate that in the absence of scatter reduction techniques, images will be affected by cupping artifacts, and there will be reduced accuracy of attenuation values inferred from the reconstructed images. The effect of x-ray scatter on the contrast, noise, and lesion signal-difference-to-noise ratio (SDNR) in tomosynthesis reconstruction was measured as a function of the tumor size. When a with-scatter reconstruction was compared to one without scatter for a 5 cm compressed breast, the following results were observed. The contrast in the reconstructed central slice image of a tumorlike mass (14 mm in diameter) was reduced by 30%, the voxel value (inferred attenuation coefficient) was reduced by 28%, and the SDNR fell by 60%. The authors have quantified the degree to which scatter degrades the image quality over a wide range of parameters relevant to breast tomosynthesis, including x-ray beam energy, breast thickness, breast diameter, and breast composition. They also demonstrate, though, that even without a scatter rejection device, the contrast and SDNR in the reconstructed tomosynthesis slice are higher than those of conventional mammographic projection images acquired with a grid at an equivalent total exposure.

Wu Gang; Mainprize, James G.; Boone, John M.; Yaffe, Martin J. [Imaging Research, Sunnybrook Health Sciences Centre, S-657, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada) and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Department of Radiology, X-ray Imaging Laboratory, U. C. Davis Medical Center, 4701 X Street, Sacramento, California 95817 and Department of Biomedical Engineering, University of California, Davis, California 95616 (United States); Imaging Research, Sunnybrook Health Sciences Centre, S-657, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada) and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada)

2009-10-15

365

Intraoral computed radiography using the Fuji computed radiography imaging plate. Correlation between image quality and reading condition.  

PubMed

The quality of images obtained by a new method of intraoral computed radiography using three types of imaging plates and a drum scanner designed exclusively for use with an imaging plate was investigated. The aperture size for reading of radiographic data from the imaging plate and for film recording was 50, 100, or 150 microns 2. The results indicated that high resolution type imaging plate for mammography produced the best image quality. For each imaging plate, it was also found that the image quality improved as the aperture size was decreased. However, the high resolution type IP even at the aperture size of 100 microns 2 showed diagnostic accuracy as high as the image processing of conventional periapical radiographs. This finding suggests that this new imaging system using an imaging plate at the reading and recording aperture size 100 microns 2 has promise for use in intraoral radiography. PMID:7936596

Kashima, I; Sakurai, T; Matsuki, T; Nakamura, K; Aoki, H; Ishii, M; Kanagawa, Y

1994-08-01

366

Measurement of RBC Velocities in the Rat Pial Arteries with an Image-Intensified High-Speed Video Camera System  

Microsoft Academic Search

The mean centerline red blood cell (RBC) velocity of the rat pial artery was measured using an image-intensified high-speed (1000 frames\\/s) video camera system and RBCs labeled with fluorescein isothiocyanate (FITC). Some investigations measuring RBC velocity have been made in most organs, but the RBC velocity of the pial artery has not yet been measured with this system using FITC

Mami Ishikawa; Eiichi Sekizuka; Katsuyoshi Shimizu; Noriyuki Yamaguchi; Takeshi Kawase

1998-01-01

367

Comparative Imaging Study in Ultrasound MRI, CT and DSA using a MultiModality Renal Artery Phantom  

Microsoft Academic Search

A range of anatomically-realistic multi-modality renal artery phantoms consisting of vessels with varying degrees of stenosis was developed and evaluated using four imaging techniques currently used to detect renal artery stenosis (RAS). The spatial resolution required to visualize vascular geometry and the velocity detection performance required to adequately characterize blood flow in patients suffering from RAS is currently ill-defined, with

Deirdre King; Andrew Fagan; Carmel Moran; Jacinta Browne

2011-01-01

368

Rate Allocation of Equal Image Quality for MPEG4 FGS Video Streaming  

Microsoft Academic Search

This paper proposes a new rate allocation method for MPEG-4 fine granularity scalable (FGS) video streaming, with which the received image quality can be smoothed during the streaming period. Although average bit rate allocation is quite simple, the image's quality changes greatly between frames, which will result in quality fluctuation and degrade the streaming quality. In this paper the bits

Xuejun Zhao; Yuwen He; Shiqiang Yang; Yuzhuo Zhong

2002-01-01

369

Indium-111 platelet imaging for detection of platelet deposition in abdominal aneurysms and prosthetic arterial grafts  

SciTech Connect

Thirty-four platelet imaging studies were performed in 23 patients to determine whether platelet deposition could be detected in patients with vascular aneurysms (18 patients) or in patients in whom Dacron prosthetic grafts had been placed (5 patients). In patients in whom abnormal platelet deposition was detected, the effect of administration of platelet-active drugs on platelet deposition was examined. Of the 18 patients with an aneurysm, 12 had equivocally positive studies on initial imaging and 2 had equivocally positive images. Of five patients with Dacron arterial grafts in place, four had diffuse platelet deposition in the grafts; the fifth patient had a platelet deposition only in a pseudoaneurysm. Eight patients with an abdominal aneurysm and positive or equivocally positive baseline images were restudied during platelet-active drug therapy either with aspirin plus dipyridamole (seven patients) or with sulfinpyrazone (four patients). No patient studied during treatment with aspirin plus dipyridamole had detectably decreased platelet deposition compared with baseline determinations. In contrast, two of four patients studied while receiving sulfinpyrazone showed decreased platelet deposition. Thus, platelet imaging may be of value for studying platelet physiology in vivo and for assessing platelet-active drugs and the thrombogenicity of prosthetic graft materials in human beings.

Ritchie, J.L.; Stratton, J.R.; Thiele, B.; Haminton, G.W.; Warrick, L.N.; Huang, T.W.; Harker, L.A.

1981-04-01

370

Uterine artery embolization: pre- and post-procedural evaluation using magnetic resonance imaging.  

PubMed

Magnetic resonance (MR) imaging has become the preferred method in assessing the uterus and pelvis prior to and following uterine artery embolization (UAE). The multiplanar imaging capabilities, increased spatial and contrast resolution, anatomic detail and assessment of fibroid viability that MR provides over ultrasound allows for accurate pre-treatment planning and post-treatment assessment. The purpose of this article is to demonstrate the use of MR in the selection of patients, anatomic evaluation and procedural planning before UAE, describe the use of MR in evaluating treatment response after UAE and illustrate the use of MR in identifying post-UAE complications. An understanding of these principles is essential in guiding appropriate therapy, determining treatment effectiveness and identifying associated complications before and after UAE. PMID:23471598

Siddiqui, Nasir; Nikolaidis, Paul; Hammond, Nancy; Miller, Frank H

2013-10-01

371

Demonstration of correlations between physical and clinical image quality measures in chest and lumbar spine radiography  

Microsoft Academic Search

Clinical and physical assessments of image quality are compared and the correlation between the two derived. Clinical assessment has been made by a group of expert radiologists who evaluated the fulfillment of the European Image Criteria for chest and lumbar spine radiography; yielding the so-called Image Criteria Score, ICS. Physical measures of image quality were calculated using a Monte Carlo

Michael Sandborg; Anders Tingberg; Patrik Sund; Graham McVey; David Dance; Gudrun Alm Carlsson

2000-01-01

372

Print quality detection of cigarette wrapper based on image processing and bp network  

Microsoft Academic Search

To resolve the problem of the print quality detection of cigarette wrapper online, the paper has proposed a method to detect and diagnose the print quality based on image processing and BP network. Using the feature parameters of the subtraction image between the detected print image and the standard template image, a BP network is applied to classify the prints

Zhengwei Zhu; Yuying Guo

2008-01-01

373

Image fusion quality assessment based on discrete cosine transform and human visual system  

NASA Astrophysics Data System (ADS)

With the rapid development of image fusion technology, image fusion quality evaluation plays a very important guiding role in selecting or designing image fusion algorithms. Objective image quality assessment is an interesting research subject in the field of image quality assessment. The ideal objective evaluation method is consistent with human perceptual evaluation. A new fusion image quality assessment method according with human vision system and discrete cosine transform (DCT) is introduced. Firstly, using the Sobel operator to calculate to gradient images for the source images and fused image, the gradient images are divided into 8×8 blocks and calculating the DCT coefficients for each block, and then based on the characteristics of human visual system, calculates the luminance masking, contrast masking to form the perceptual error matrix between input images and fused images. Finally, weighs the perceptual error matrix using the structural similarity. Experiments demonstrate that the new assessment maintains better consistency with human subjective perception.

Dou, Jianfang; Li, Jianxun

2012-09-01

374

Channelling optics for high quality imaging of sensory hair  

NASA Astrophysics Data System (ADS)

A long distance microscope (LDM) is extended by a lens and aperture array. This newly formed channelling LDM is superior in high quality, high-speed imaging of large field of views (FOV). It allows imaging the same FOV like a conventional LDM, but at improved magnification. The optical design is evaluated by calculations with the ray tracing code ZEMAX. High-speed imaging of a 2 × 2 mm2 FOV is realized at 3.000 frames per second and 1 ?m per pixel image resolution. In combination with flow sensitive hair the optics forms a wall shear stress sensor. The optics images the direct vicinity of twenty-one flow sensitive hair distributed in a quadratic array. The hair consists of identical micro-pillars that are 20 ?m in diameter, 390 ?m in length and made from polydimethylsiloxane (PDMS). Sensor validation is conducted in the transition region of a wall jet in air. The wall shear stress is calculated from optically measured micro-pillar tip deflections. 2D wall shear stress distributions are obtained with currently highest spatiotemporal resolution. The footprint of coherent vortical structures far away from the wall is recovered in the Fourier spectrum of wall shear stress fluctuations. High energetic patterns of 2D wall shear stress distributions are identified by proper orthogonal decomposition (POD).

Skupsch, C.; Klotz, T.; Chaves, H.; Brücker, C.

2012-04-01

375

Intimal Flaps Detected by Optical Frequency Domain Imaging in the Proximal Segments of Native Coronary Arteries.  

PubMed

Background:?The prevalence and clinical sequelae of optical frequency domain imaging (OFDI)-detected intimal flaps caused by vessel trauma or plaque rupture in the proximal native coronary arteries have not been described. Methods and Results:?OFDI investigation was performed following stent implantation in patients with ST-segment elevation myocardial infarction (STEMI). We defined a flap-like structure (FS) as a disruption or discontinuation of the endoluminal vessel surface, and classified as actual flap or artifact. FS in the left main stem, or maximally 20mm distal to the guiding catheter in the proximal right coronary artery were assessed. A total of 8,931 frames in 97 patients were analyzed in a frame-by-frame fashion (0.125-mm interval). OFDI identified 8 FS in 7 patients, none of which was evident angiographically. All FS were left untreated because the operators per protocol were blinded to the OFDI images. A total of 5 FS in 5 patients (5.1%) appeared to be actual flaps in which only the intima was involved (mean distance from guiding catheter: 4.8±2.7mm). The remaining 3 FS in 3 patients were artifacts; namely, residual blood and interface light reflectivity. There were no adverse cardiac events during 6-months follow-up. Conclusions:?In 5.1% of STEMI patients, post-procedural OFDI identified flaps with minimal involvement of the intima in the proximal coronary arteries. A precise interpretation of FS may help decision making to avoid unnecessary procedures. (Clinical Trial Registration Information: ClinicalTrials.gov identifier: NCT01271361.). PMID:23778184

Muramatsu, Takashi; García-García, Hector M; Onuma, Yoshinobu; Zhang, Yao-Jun; Bourantas, Christos V; Diletti, Roberto; Iqbal, Javaid; Radu, Maria D; Ozaki, Yukio; Serruys, Patrick W

2013-06-15

376

Intimal flaps detected by optical frequency domain imaging in the proximal segments of native coronary arteries.  

PubMed

Background:?The prevalence and clinical sequelae of optical frequency domain imaging (OFDI)-detected intimal flaps caused by vessel trauma or plaque rupture in the proximal native coronary arteries have not been described. Methods and Results:?OFDI investigation was performed following stent implantation in patients with ST-segment elevation myocardial infarction (STEMI). We defined a flap-like structure (FS) as a disruption or discontinuation of the endoluminal vessel surface, and classified as actual flap or artifact. FS in the left main stem, or maximally 20mm distal to the guiding catheter in the proximal right coronary artery were assessed. A total of 8,931 frames in 97 patients were analyzed in a frame-by-frame fashion (0.125-mm interval). OFDI identified 8 FS in 7 patients, none of which was evident angiographically. All FS were left untreated because the operators per protocol were blinded to the OFDI images. A total of 5 FS in 5 patients (5.1%) appeared to be actual flaps in which only the intima was involved (mean distance from guiding catheter: 4.8±2.7mm). The remaining 3 FS in 3 patients were artifacts; namely, residual blood and interface light reflectivity. There were no adverse cardiac events during 6-months follow-up. Conclusions:?In 5.1% of STEMI patients, post-procedural OFDI identified flaps with minimal involvement of the intima in the proximal coronary arteries. A precise interpretation of FS may help decision making to avoid unnecessary procedures. (Clinical Trial Registration Information: ClinicalTrials.gov identifier: NCT01271361.)??(Circ J?2013; 77: 2327-2333). PMID:23979567

Muramatsu, Takashi; García-García, Hector M; Onuma, Yoshinobu; Zhang, Yao-Jun; Bourantas, Christos V; Diletti, Roberto; Iqbal, Javaid; Radu, Maria D; Ozaki, Yukio; Serruys, Patrick W

2013-06-15

377

Imaging flow dynamics in murine coronary arteries with spectral domain optical Doppler tomography.  

PubMed

Blood flow in murine epicardial and intra-myocardial coronary arteries was measured in vivo with spectral domain optical Doppler tomography (SD-ODT). Videos at frame rates up to 180 fps were collected and processed to extract phase shifts associated with moving erythrocytes in the coronary arteries. Radial averaging centered on the vessel lumen provided spatial smoothing of phase noise in a single cross-sectional frame for instantaneous peak velocity measurement without distortion of the flow profile. Temporal averaging synchronized to the cardiac cycle (i.e., gating) was also performed to reduce phase noise, although resulting in lower flow profiles. The vessel angle with respect to incident imaging beam was measured with three-dimensional raster scans collected from the same region as the high speed cross-sectional scans. The variability in peak phase measurement was 10-15% from cycle to cycle on a single animal but larger for measurements among animals. The inter-subject variability is attributed to factors related to real physiological and anatomical differences, instrumentation variables, and measurement error. The measured peak instantaneous flow velocity in a ~40-µm diameter vessel was 23.5 mm/s (28 kHz Doppler phase shift). In addition to measurement of the flow velocity, we observed several dynamic features of the vessel and surrounding myocardium in the intensity and phase sequences, including asymmetric vessel deformation and rapid flow reversal immediately following maximum flow, in confirmation of known coronary artery flow dynamics. SD-ODT is an optical imaging tool that can provide in vivo measures of structural and functional information on cardiac function in small animals. PMID:22574259

Hammer, Daniel X; Mujat, Mircea; Ferguson, R Daniel; Iftimia, Nicusor; Escobedo, Daniel; Jenkins, J Travis; Lim, Hyunji; Milner, Thomas E; Feldman, Marc D

2012-03-13

378

Quantitative analysis of dipyridamole-thallium images for the detection of coronary artery disease  

SciTech Connect

To determine if the detection of coronary artery disease by dipyridamole-thallium imaging is improved by quantitative versus qualitative analysis, and combining quantitative variables, 80 patients with chest pain (53 with and 27 without coronary artery disease) who underwent cardiac catheterization were studied. Segmental thallium initial uptake, linear clearance, monoexponential clearance and redistribution were measured from early, intermediate and delayed images acquired in three projections. Normal values were determined from 13 other clinically normal subjects. When five segments per view were used for quantitative analysis, sensitivity and specificity were 87 and 63%, respectively, for uptake, 77 and 67% for linear clearance, 60 and 60% for monoexponential clearance and 62 and 56% for redistribution. Of the four variables, uptake and linear clearance were the most sensitive (p less than 0.01) and specificity did not differ significantly. Using three segments per view, the specificity of uptake increased to 78% without a significant change in sensitivity (85%). With this approach, sensitivity and specificity did not differ from those of qualitative analysis (85 and 78%, respectively). Stepwise logistic regression analysis demonstrated that the best quantitative thallium correlate of the presence of coronary artery disease was a combination variable of ''either abnormal uptake or abnormal linear clearance, or both.'' Using five segments per view, the model's specificity (85%) was greater than that of uptake alone, with similar sensitivity (92%). Using three segments per view, the model's specificity (93%) was greater than that of uptake alone and of qualitative analysis (p less than 0.05), with similar sensitivity (85%).

Ruddy, T.D.; Dighero, H.R.; Newell, J.B.; Pohost, G.M.; Strauss, H.W.; Okada, R.D.; Boucher, C.A.

1987-07-01

379

Image quality degradation by light scattering processes in high performance display devices for medical imaging  

Microsoft Academic Search

This thesis addresses the characterization of light scattering processes that degrade image quality in high performance electronic display devices for digital radiography. Using novel experimental and computational tools, we study the lateral diffusion of light in emissive display devices that causes extensive veiling glare and significant reduction of the physical contrast. In addition, we examine the deleterious effects of ambient

Aldo Badano

1999-01-01

380

Patient dose and image quality from mega-voltage cone beam computed tomography imaging  

SciTech Connect

The evolution of ever more conformal radiation delivery techniques makes the subject of accurate localization of increasing importance in radiotherapy. Several systems can be utilized including kilo-voltage and mega-voltage cone-beam computed tomography (MV-CBCT), CT on rail or helical tomography. One of the attractive aspects of mega-voltage cone-beam CT is that it uses the therapy beam along with an electronic portal imaging device to image the patient prior to the delivery of treatment. However, the use of a photon beam energy in the mega-voltage range for volumetric imaging degrades the image quality and increases the patient radiation dose. To optimize image quality and patient dose in MV-CBCT imaging procedures, a series of dose measurements in cylindrical and anthropomorphic phantoms using an ionization chamber, radiographic films, and thermoluminescent dosimeters was performed. Furthermore, the dependence of the contrast to noise ratio and spatial resolution of the image upon the dose delivered for a 20-cm-diam cylindrical phantom was evaluated. Depending on the anatomical site and patient thickness, we found that the minimum dose deposited in the irradiated volume was 5-9 cGy and the maximum dose was between 9 and 17 cGy for our clinical MV-CBCT imaging protocols. Results also demonstrated that for high contrast areas such as bony anatomy, low doses are sufficient for image registration and visualization of the three-dimensional boundaries between soft tissue and bony structures. However, as the difference in tissue density decreased, the dose required to identify soft tissue boundaries increased. Finally, the dose delivered by MV-CBCT was simulated using a treatment planning system (TPS), thereby allowing the incorporation of MV-CBCT dose in the treatment planning process. The TPS-calculated doses agreed well with measurements for a wide range of imaging protocols.

Gayou, Olivier; Parda, David S.; Johnson, Mark; Miften, Moyed [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, Pennsylvania 15212 and Drexel University College of Medicine, Allegheny Campus, Pittsburgh, Pennsylvania 15212 (United States)

2007-02-15

381

Impact of PVCs noted during coronary calcium scan on image quality and accuracy in subsequent coronary dual-source CT angiography.  

PubMed

The purpose of this study was to investigate the impact of the presence of one or more premature ventricular contractions (PVCs) during coronary calcium score scan (CS) on image quality and accuracy of subsequent dual-source coronary CT angiography (DS CCTA). Fifty-three out of 502 patients showed one or more PVCs during CS and built the study group. Sixty consecutively registered patients with sinus rhythm formed the control group. Two independent, blinded readers classified 1,723 coronary artery segments as being of diagnostic or non-diagnostic image quality. All segments with diagnostic image quality were assessed for the presence for significant coronary artery stenosis. Accuracy was calculated using conventional angiography as standard of reference. The percentage of DS CCTA data sets with diagnostic image quality was significantly lower in the study group (79.2%) compared to the control group (90.6%, P < 0.05). The rate of coronary segment with diagnostic image quality was highly significant lower in the study group (89.5%; n = 723/808) compared to the control group (99.4%; n = 908/915; P < 0.001). However, accuracy did not differ in both groups. Significant correlation between non-diagnostic image quality and mean HR was only found in the study group (P = 0.019). The presence of one or more PVCs during CS does not affect accuracy but impairs image quality of subsequent DS CCTA. Mean HR is a predictor of non-diagnostic data sets only in the study group, suggesting more aggressive HR control could be beneficial. PMID:20835764

Eicher, Wolfgang; Kau, Thomas; Niedermayer, Martin; Senft, Birgit; Sinzig, Maria; Strozyk, Birgit; Hausegger, Klaus Armin

2010-09-11

382

Image quality in optical imaging by time-correlated single photon-counting technique  

NASA Astrophysics Data System (ADS)

Theoretical and experimental investigations on image quality are extremely important in optical imaging in order to better define the role of optical techniques in medical diagnostics. Today time-resolved laser transillumination can be considered a good candidate as an alternative and/or auxiliary technique in medical diagnostic field. The intrinsic quality of an image is related to the concepts of spatial resolution, noise and contrast. A common method to measure these parameters is by using Edge Response Function measurements with a black mask. We investigated these parameters using an experimental apparatus mainly composed by a picosecond solid-state laser and a time-correlated single photon-counting system. The investigated samples were suspensions of Intralipid 10% with distilled water in which a black mask was inserted and bidimensional scanning were performed. The experimental data were analyzed in order to get information on the above-mentioned image quality parameters. For spatial resolution a comparison with random walk predictions has been attempted. The results of this study can be particularly useful in identifying the best working conditions and in improving teh performance of image reconstruction algorithms since the clinical prototypes of optical mammogrpahers nowadays under pre-clinical investigation adopt time-correlated single photon-counting technique.

Mormile, M.; Esposito, R.; Romano, R.; Lepore, M.; Indovina, P. L.

2005-06-01

383

Diagnostic imaging--evaluating image quality using visual grading characteristic (VGC) analysis.  

PubMed

Radiologists are regularly faced with the task of comparing image quality obtained using different imaging systems or settings. Visual grading techniques can be used to evaluate the quality of images by grading the clarity of reproduction of anatomical or pathological structures. The methods, which include "visual grading analysis (VGA)" and the "image criteria (IC) study", are characterised by their attractive simplicity and reliability. Non-parametric rank-invariant statistical methods are suitable techniques for statistical analysis of VGA-data. Båth and Månsson (2007) introduced such a method and termed it "visual grading characteristics (VGC) analysis". This paper gives an overview of the principle together with an example of its use in veterinary radiology. The aim of this review article is to encourage veterinary researchers to apply this method which has proven valuable in the human field. Basically, the method can also be applied for the analysis of other categories of images (e.g. histological sections, cytological smears) in cases where the task is to evaluate features subjectively on the basis of a score, allowing some degree of freedom of decision. Furthermore, the aim of the investigation is not necessarily restricted to quality aspects. Other questions such as the effects of treatment options on the appearance of certain structures can be compared as well. PMID:20461455

Ludewig, Eberhard; Richter, Andreas; Frame, Mairi

2010-05-12

384

Decision theory applied to image quality control in radiology  

PubMed Central

Background The present work aims at the application of the decision theory to radiological image quality control (QC) in diagnostic routine. The main problem addressed in the framework of decision theory is to accept or reject a film lot of a radiology service. The probability of each decision of a determined set of variables was obtained from the selected films. Methods Based on a radiology service routine a decision probability function was determined for each considered group of combination characteristics. These characteristics were related to the film quality control. These parameters were also framed in a set of 8 possibilities, resulting in 256 possible decision rules. In order to determine a general utility application function to access the decision risk, we have used a simple unique parameter called r. The payoffs chosen were: diagnostic's result (correct/incorrect), cost (high/low), and patient satisfaction (yes/no) resulting in eight possible combinations. Results Depending on the value of r, more or less risk will occur related to the decision-making. The utility function was evaluated in order to determine the probability of a decision. The decision was made with patients or administrators' opinions from a radiology service center. Conclusion The model is a formal quantitative approach to make a decision related to the medical imaging quality, providing an instrument to discriminate what is really necessary to accept or reject a film or a film lot. The method presented herein can help to access the risk level of an incorrect radiological diagnosis decision.

Lessa, Patricia S; Caous, Cristofer A; Arantes, Paula R; Amaro, Edson; de Souza, Fernando M Campello

2008-01-01

385

Accommodation stimulus-response function and retinal image quality.  

PubMed

Accommodation stimulus-response function (ASRF) and its relationship to retinal image quality were investigated using a modified wavefront sensor. Ten subjects were presented with six vergence stimuli between 0.17 D and 5 D. For each vergence distance, ocular wavefronts and subjective visual acuity were measured. Wavefronts were analysed for a fixed 3-mm pupil diameter and for natural pupil sizes. Visual Strehl ratio computed in the frequency domain (VSOTF) and retinal images were calculated for each condition tested. Subjective visual acuity was significantly improved at intermediate vergence distances (1D and 2D; p < 0.01), and only decreased significantly at 5 D compared with 0.17 D (p < 0.05). VSOTF magnitude was associated with subjective visual acuity and VSOTF peak location correlated with accommodation error. Apparent accommodation errors due to spherical aberration were highly correlated with accommodation lead and lag for natural pupils (R(2) = 0.80) but not for fixed 3-mm pupils (R(2) < 0.00). The combination of higher-order aberrations and accommodation errors improved retinal image quality compared with accommodation errors or higher order aberrations alone. Pupil size and higher order aberrations play an important role in the ASRF. PMID:16040078

Buehren, Tobias; Collins, Michael J

2005-07-22

386

Image quality evaluation of breast tomosynthesis with synchrotron radiation  

SciTech Connect

Purpose: This study investigates the image quality of tomosynthesis slices obtained from several acquisition sets with synchrotron radiation using a breast phantom incorporating details that mimic various breast lesions, in a heterogeneous background. Methods: A complex Breast phantom (MAMMAX) with a heterogeneous background and thickness that corresponds to 4.5 cm compressed breast with an average composition of 50% adipose and 50% glandular tissue was assembled using two commercial phantoms. Projection images using acquisition arcs of 24 Degree-Sign , 32 Degree-Sign , 40 Degree-Sign , 48 Degree-Sign , and 56 Degree-Sign at incident energy of 17 keV were obtained from the phantom with the synchrotron radiation for medical physics beamline at ELETTRA Synchrotron Light Laboratory. The total mean glandular dose was set equal to 2.5 mGy. Tomograms were reconstructed with simple multiple projection algorithm (MPA) and filtered MPA. In the latter case, a median filter, a sinc filter, and a combination of those two filters were applied on the experimental data prior to MPA reconstruction. Visual inspection, contrast to noise ratio, contrast, and artifact spread function were the figures of merit used in the evaluation of the visualisation and detection of low- and high-contrast breast features, as a function of the reconstruction algorithm and acquisition arc. To study the benefits of using monochromatic beams, single projection images at incident energies ranging from 14 to 27 keV were acquired with the same phantom and weighted to synthesize polychromatic images at a typical incident x-ray spectrum with W target. Results: Filters were optimised to reconstruct features with different attenuation characteristics and dimensions. In the case of 6 mm low-contrast details, improved visual appearance as well as higher contrast to noise ratio and contrast values were observed for the two filtered MPA algorithms that exploit the sinc filter. These features are better visualized at extended arc length, as the acquisition arc of 56 Degree-Sign with 15 projection images demonstrates the highest image reconstruction quality. For microcalcifications, filtered MPA implemented with a combination of median and sinc filters indicates better feature appearance due to efficient suppression of background tissue. The image quality of these features is less sensitive to the acquisition arc. Calcifications with size ranging from 170 to 500 {mu}m, like the ones presently studied, are well identified and visualized for all arcs used. The comparison of single projection images obtained under different beam conditions showed that the use of monochromatic beam can produce an image with higher contrast and contrast to noise ratio compared to an image corresponding to a polychromatic beam even when the latter is acquired with double incident exposure. Conclusions: Filter optimization in respect to the type of feature characteristics is important before the reconstruction. The MPA combined with median and sinc filters results in improved reconstruction of microcalcifications and low-contrast features. The latter are better visualized at extended arc length, while microcalcifications are less sensitive to this acquisition parameter. Use of monochromatic beams may result in tomographic images with higher contrast acquired at lower incident exposures.

Malliori, A.; Bliznakova, K.; Speller, R. D.; Horrocks, J. A.; Rigon, L.; Tromba, G.; Pallikarakis, N. [Department of Medical Physics, Faculty of Medicine, University of Patras, Patras 26500 (Greece); Department of Medical Physics and Bioengineering, University College London, London WVC1E 6BT (United Kingdom); Clinical Physics CAU, St Bartholomew's Hospital, London EC1A 7BE (United Kingdom); INFN, Sezione di Trieste, Trieste 34127 (Italy); ELETTRA, Basovizza, Trieste 34012 (Italy); Department of Medical Physics, Faculty of Medicine, University of Patras, Patras 26500 (Greece)

2012-09-15

387

[3 T MRI imaging methods in the study of contrast-enhanced Adamkiewicz Artery].  

PubMed

Contrast enhanced magnetic resonance angiography (CE-MRA) is a common method for imaging the Adamkiewicz Artery (AKA). Test-bolus imaging methods have long been the mainstream, and recently, a time resolved technique (4D-MRA) is also reported. However, the current rates of detection for both are mixed, and the best method has not been established yet. For AKA, the present rate is 72% left, Th8?L1 91% that exists between, with a vessel diameter of 0.5 to 1.5 mm. Additionally, the AKA branch is known to have large individual differences, and thus, a wide range of high spatial resolution imaging. At our institution from January 2009, a 3 T system is installed, and 4D-MRA (time-resolved angiography with interleaved stochastic trajectories: TWIST) imaging became possible. TWIST is a sequence to balance the temporal resolution and spatial resolution, and is considered optimal for the imaging of AKA. In accordance with this idea, the first group of seven patients was imaged by TWIST, but in all cases, the results were not depicting AKA. In subsequent cases, the technique was changed to a 3D-gradient echo sequence with a Bolus-tracking method (Care bolus), and good results were obtained. In conclusion, AKA TWIST was not thought to depict the relationship between specific parameters. When using TWIST for imaging AKA, we will need to find out why it was not visualized, by examining AKA with simulated vessel phantoms, TWIST and Care Bolus. Furthermore, we report on our visual evaluation of the Retrospective clinical pictures. PMID:21282914

Hirata, Keiya; Takahashi, Masaru; Chikakoshi, Saeko; Nakamura, Eisui; Nishio, Hiroshi

2010-12-20

388

Acoustic radiation force impulse imaging of the mechanical properties of arteries: in vivo and ex vivo results.  

PubMed

We present results of a pilot study of ex vivo and in vivo acoustic radiation force impulse (ARFI) imaging demonstrating measurements of the mechanical properties of the carotid and popliteal arteries. The results were obtained on a modified commercial scanner, providing coregistered B-mode and color Doppler images. 2D and 1D through time images are formed from the measurements of tissues' response to very brief and localized applications of radiation force. The images show good correlation with B-mode and, in ex vivo studies, pathology-based characterizations of vessel geometry and plaque stiffness. In vivo measurements of arterial response during both systole and diastole are presented. We address implementation issues and discuss potential applications of this new vascular imaging method. PMID:15550320

Trahey, Gregg E; Palmeri, Mark L; Bentley, Rex C; Nightingale, Kathryn R

2004-09-01

389

Digital processing to improve image quality in real-time neutron radiography  

NASA Astrophysics Data System (ADS)

Real-time neutron radiography (NTV) has been used for practical applications at the Kyoto University Reactor (KUR). At present, however, the direct image from the TV system is still poor in resolution and low in contrast. In this paper several image improvements are demonstrated, such as a frame summing technique, which are effective in increasing image quality in neutron radiography. Image integration before the A/D converter has a beneficial effect on image quality and the high quality image reveals details invisible in direct images, such as: small holes by a reversed image, defects in a neutron converter screen through a high quality image, a moving object in a contoured image, a slight difference between two low-contrast images by a subtraction technique, and so on. For the real-time application a contouring operation and an averaging approach can also be utilized effectively.

Fujine, Shigenori; Yoneda, Kenji; Kanda, Keiji

1985-01-01

390

A novel technique of image quality objective measurement by wavelet analysis throughout the spatial frequency range  

NASA Astrophysics Data System (ADS)

An essential determinant of the value of surrogate digital images is their quality. Image quality measurement has become crucial for most image processing applications. Over the past years , there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image quality. This paper proposes a reliable automatic method for objective image quality measurement by wavelet analysis throughout the spatial frequency range. This is done by a detailed analysis of an image for a wide range of spatial frequency content, using a combination of modulation transfer function (MTF), brightness, contrast, saturation, sharpness and noise, as a more revealing metric for quality evaluation. A fast lifting wavelet algorithm is developed for computationally efficient spatial frequency analysis, where fine image detail corresponding to high spatial frequencies and image sharpness in regard to lower and mid -range spatial frequencies can be examined and compared accordingly. The wavelet frequency deconstruction is actually to extract the feature of edges in sub-band images. The technique provides a means to relate the quality of an image to the interpretation and quantification throughout the frequency range, in which the noise level is estimated in assisting with quality analysis. The experimental results of using this method for image quality measurement exhibit good correlation to subjective visual quality assessments.

Luo, Gaoyong

2004-10-01

391

Image quality improvements in C-Arm CT (CACT) for liver oncology applications: Preliminary study in rabbits.  

PubMed

Abstract Introduction: C-Arm CT (CACT) is a new imaging modality in liver oncology therapy that allows for the acquisition of 3D images intra-procedurally. CACT has been used to enhance intra-arterial therapies for the liver by improving lesion detection, avoiding non-target embolization, and allowing for more selective delivery of agents. However, one of the limitations of this technology is image artifacts created by respiratory motion. Purpose: To determine in this preliminary study improvements in image acquisition, motion compensation, and high resolution 3D reconstruction that can improve CACT image quality (IQ). Material and methods: Three adult male New Zealand white rabbits were used for this study. First, a control rabbit was used to select the best x-ray acquisition imaging protocol and then two rabbits were implanted with liver tumor to further develop 3D image reconstruction and motion compensation algorithms. Results: The best IQ was obtained using the low 80 kVp protocol with motion compensated reconstruction with high resolution and fast acquisition speed (60 fps, 5 s/scan, and 312 images). Conclusion: IQ improved by: (1) decreasing acquisition time, (2) applying motion-compensated reconstruction, and (3) high resolution 3D reconstruction. The findings of this study can be applied to future animal studies and eventually could be translated into the clinical environment. PMID:23837536

Tacher, Vania; Bhagat, Nikhil; P Rao, Pramod; Lin, Mingde; Schäfer, Dirk; Noordhoek, Niels; Eshuis, Peter; Radaelli, Alessandro; Liapi, Eleni; Grass, Michael; Geschwind, Jean-François

2013-07-09

392

Functional magnetic resonance imaging of awake monkeys: some approaches for improving imaging quality  

PubMed Central

Functional magnetic resonance imaging (fMRI), at high magnetic field strength can suffer from serious degradation of image quality because of motion and physiological noise, as well as spatial distortions and signal losses due to susceptibility effects. Overcoming such limitations is essential for sensitive detection and reliable interpretation of fMRI data. These issues are particularly problematic in studies of awake animals. As part of our initial efforts to study functional brain activations in awake, behaving monkeys using fMRI at 4.7T, we have developed acquisition and analysis procedures to improve image quality with encouraging results. We evaluated the influence of two main variables on image quality. First, we show how important the level of behavioral training is for obtaining good data stability and high temporal signal-to-noise ratios. In initial sessions, our typical scan session lasted 1.5 hours, partitioned into short (<10 minutes) runs. During reward periods and breaks between runs, the monkey exhibited movements resulting in considerable image misregistrations. After a few months of extensive behavioral training, we were able to increase the length of individual runs and the total length of each session. The monkey learned to wait until the end of a block for fluid reward, resulting in longer periods of continuous acquisition. Each additional 60 training sessions extended the duration of each session by 60 minutes, culminating, after about 140 training sessions, in sessions that last about four hours. As a result, the average translational movement decreased from over 500 ?m to less than 80 ?m, a displacement close to that observed in anesthetized monkeys scanned in a 7 T horizontal scanner. Another major source of distortion at high fields arises from susceptibility variations. To reduce such artifacts, we used segmented gradient-echo echo-planar imaging (EPI) sequences. Increasing the number of segments significantly decreased susceptibility artifacts and image distortion. Comparisons of images from functional runs using four segments with those using a single-shot EPI sequence revealed a roughly two-fold improvement in functional signal-to-noise-ratio and 50% decrease in distortion. These methods enabled reliable detection of neural activation and permitted blood-oxygenation-level-dependent (BOLD) based mapping of early visual areas in monkeys using a volume coil. In summary, both extensive behavioral training of monkeys and application of segmented gradient-echo EPI sequence improved signal-to-noise and image quality. Understanding the effects these factors have is important for the application of high field imaging methods to the detection of sub-millimeter functional structures in the awake monkey brain.

Chen, Gang; Wang, Feng; Dillenburger, Barbara C.; Friedman, Robert M.; Chen, Li M.; Gore, John C.; Avison, Malcolm J.; Roe, Anna W.

2011-01-01

393

No-training, no-reference image quality index using perceptual features  

NASA Astrophysics Data System (ADS)

We propose a universal no-reference (NR) image quality assessment (QA) index that does not require training on human opinion scores. The new index utilizes perceptually relevant image features extracted from the distorted image. These include the mean phase congruency (PC) of the image, the entropy of the phase congruencyPC image, the entropy of the distorted image, and the mean gradient magnitude of the distorted image. Image quality prediction is accomplished by using a simple functional relationship of these features. The experimental results show that the new index accords closely with human subjective judgments of diverse distorted images.

Li, Chaofeng; Ju, Yiwen; Bovik, Alan C.; Wu, Xiaojun; Sang, Qingbing

2013-05-01

394

Coronary artery wall imaging in mice using osmium tetroxide and micro-computed tomography (micro-CT)  

SciTech Connect

The high spatial resolution of micro-computed tomography (micro-CT) is ideal for 3D imaging of coronary arteries in intact mouse heart specimens. Previously, micro-CT of mouse heart specimens utilized intravascular contrast agents that hardened within the vessel lumen and allowed a vascular cast to be made. However, for mouse coronary artery disease models, it is highly desirable to image coronary artery walls and highlight plaques. For this purpose, we describe an ex vivo contrast-enhanced micro-CT imaging technique based on tissue staining with osmium tetroxide (OsO{sub 4}) solution. As a tissue-staining contrast agent, OsO{sub 4} is retained in the vessel wall and surrounding tissue during the fixation process and cleared from the vessel lumens. Its high X-ray attenuation makes the artery wall visible in CT. Additionally, since OsO{sub 4} preferentially binds to lipids, it highlights lipid deposition in the artery wall. We performed micro-CT of heart specimens of 5- to 25-week-old C57BL/6 wild-type mice and 5- to 13-week-old apolipoprotein E knockout (apoE{sup -/-}) mice at 10 {mu}m resolution. The results show that walls of coronary arteries as small as 45 {mu}m in diameter are visible using a table-top micro-CT scanner. Similar image clarity was achieved with 1/2000th the scan time using a synchrotron CT scanner. In 13-week-old apoE mice, lipid-rich plaques are visible in the aorta. Our study shows that the combination of OsO{sub 4} and micro-CT permits the visualization of the coronary artery wall in intact mouse hearts.

Pai, Vinay M.; Kozlowski, Megan; Donahue, Danielle; Miller, Elishiah; Xiao, Xianghui; Chen, Marcus Y.; Yu, Zu-Xi; Connelly, Patricia; Jeffries, Kenneth; Wen, Han (NIH)

2012-05-10

395

Delivered image quality budget for the Discovery Channel Telescope  

NASA Astrophysics Data System (ADS)

The Discovery Channel Telescope (DCT) is a 4.3-meter telescope designed for dual optical configurations, featuring an f/6.1, 0.5° FoV, Ritchey-Chretien prescription, and a corrected f/2.3, 2° FoV, prime focus. The DCT is expected to typically deliver sub-arcsecond images, with a telescope and local seeing contribution of <0.28" FWHM at the R-C focus and <0.38" FWHM at the prime focus. The Delivered Image Quality (DIQ) budget considers errors from design residuals, manufacturing, environmental effects, and control system limitations. We present an overview of the analytical methods used, including sensitivity analysis for determining collimation effects, and a summary of contributors to the overall system performance.

Smith, Byron; Manuel, Anastacia

2010-07-01

396

Superhigh-quality color image TV system TELAN  

NASA Astrophysics Data System (ADS)

Among the shortcomings of TV system of high sharpness is that fact that the problem of increasing of noise suppression is not solved jet. In the digital TV the problem of increasing image sharpness is not solved. Their common shortcoming is their bad compatibility with existing systems of standard TV and very high complicativeness and cost. The perspective alternative to such systems is TELAN TV system of high quality. This system is free from above mentioned defects. TELAN system by receiving signals from existing standard transmitters provides improving of image sharpness to the level that is limited only by solving ability of cathode ray- tube and provides additional suppression of high frequency hindrances to 20 dB. Cost of such system practically doesn't distinguish from existing today television technic. Such results may be achieved by using psycho-physiological surplusment of analog video signals.

Antonov, Alexander A.

1998-09-01

397

Image quality improvement of an achromatic DSPI interferometer  

NASA Astrophysics Data System (ADS)

The authors develop a special configuration of a digital speckle pattern interferometer using a custom diffractive optical element. The resulting interferometer is sensitive only to the in-plane radial displacement component. The area of interest is double illuminated by light diffracted from a special diffractive optical element in such a way that the interference fringe is not wavelength dependent. The authors present in this paper different strategies for improving image quality of the fringe patterns exploring wavelength and coherence properties. The results of the different approaches are presented and compared.

Viotti, Matias R.; Albertazzi G., Armando

2012-09-01

398

An accurate iris location method for low quality iris images  

NASA Astrophysics Data System (ADS)

Iris location plays an important role in iris recognition system. Traditional iris location methods based on canny operator and integro-differential operator are affected by reflections, illumination inconsistency and eyelash. In this paper, we introduce an accurate iris location method for low quality iris images. First, a reflection removal method is used to interpolate the specular reflection. Then, we utilize Probable boundary (Pb) edge detection operator to detect papillary boundary with a lower interference point. Moreover, we optimize the Hough transform to obtain high accuracy result. Experimental results demonstrate that the location results of the proposed method are more accurate than other methods.

Wang, Ning; Li, Qiong; Abd El-Latif, Ahmed A.; Zhang, Tiejun; Peng, Jialiang

2012-04-01

399

STIS-13 CCD Spectroscopic Image Quality and ACQ Tests  

NASA Astrophysics Data System (ADS)

Check image quality along the 52x0.1 slit in combination with the G230LB grating. The target star will be positioned at several positions along the slit including 52X0.1 {nominal center position}, 52X0.1E1 {CTE position} and 51X0.1D1 {MAMA acquisitions near low background for FUV MAMA}. Positioning of the target will be done utilizing PATTERN and offsets of 0.1 arcseconds between five positions. Sufficient targets will be selected, and contingency visits prepared, to allow this activity to occur any time during the BEA period.;

Gull, Theodore

2008-07-01

400

An automated system for numerically rating document image quality  

SciTech Connect

As part of the Department of Energy document declassification program, the authors have developed a numerical rating system to predict the OCR error rate that they expect to encounter when processing a particular document. The rating algorithm produces a vector containing scores for different document image attributes such as speckle and touching characters. The OCR error rate for a document is computed from a weighted sum of the elements of the corresponding quality vector. The predicted OCR error rate will be used to screen documents that would not be handled properly with existing document processing products.

Cannon, M.; Kelly, P. [Los Alamos National Lab., NM (United States); Iyengar, S.S.; Brener, N. [Louisiana State Univ., Baton Rouge, LA (United States)

1997-04-01