These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Total Bolus Extraction Method Improves Arterial Image Quality in Dynamic CTAs Derived from Whole-Brain CTP Data  

PubMed Central

Background and Purposes. The 320-detector row CT scanner enables visualization of whole-brain hemodynamic information (dynamic CT angiography (CTA) derived from CT perfusion scans). However, arterial image quality in dynamic CTA (dCTA) is inferior to arterial image quality in standard CTA. This study evaluates whether the arterial image quality can be improved by using a total bolus extraction (ToBE) method. Materials and Methods. DCTAs of 15 patients, who presented with signs of acute cerebral ischemia, were derived from 320-slice CT perfusion scans using both the standard subtraction method and the proposed ToBE method. Two neurointerventionalists blinded to the scan type scored the arterial image quality on a 5-point scale in the 4D dCTAs in consensus. Arteries were divided into four categories: (I) large extradural, (II) intradural (large, medium, and small), (III) communicating arteries, and (IV) cerebellar and ophthalmic arteries. Results. Quality of extradural and intradural arteries was significantly higher in the ToBE dCTAs than in the standard dCTAs (extradural P = 0.001, large intradural P < 0.001, medium intradural P < 0.001, and small intradural P < 0.001). Conclusion. The 4D dCTAs derived with the total bolus extraction (ToBE) method provide hemodynamic information combined with improved arterial image quality as compared to standard 4D dCTAs. PMID:25136600

Ghariq, Elyas; Mendrik, Adriënne M.; Willems, Peter W. A.; Joemai, Raoul M. S.; Ghariq, Eidrees; Vonken, Evert-jan; van Osch, Matthias J. P.; van Walderveen, Marianne A. A.

2014-01-01

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

Ultrasound image quality evaluation  

Microsoft Academic Search

The objective of this work was to evaluate the image quality of two different ultrasound image scanners before and after de-speckle filtering. The evaluation was made by statistical and texture analysis, as well as by optical perception by two vascular experts on 20 ultrasound images of carotid artery. The de-speckled filters used were based on: (i) local statistics, (ii) homogeneous

C. Loizou; C. S. Pattichis; R. Istepanian; M. Pantziaris; E. Kyriakou; T. Tyllis; A. Nicolaides

2003-01-01

4

256-Slice CT Angiographic Evaluation of Coronary Artery Bypass Grafts: Effect of Heart Rate, Heart Rate Variability and Z-Axis Location on Image Quality  

PubMed Central

Purpose The objective of this study is to assess the effect of heart rate, heart rate variability and z-axis location on coronary artery bypass graft (CABG) image quality using a 256-slice computed tomography (CT) scanner. Methods A total of 78 patients with 254 CABG (762 graft segments) were recruited to undergo CABG assessment with 256-slice CT and prospective ECG-gating. Two observers rated graft segments for image quality on a 5-point scale. Quantitative measurements were also made. Logistic and cumulative link mixed models were used to assess the predictors of graft image quality. Results Graft image quality was judged as diagnostic (scores 5 (excellent), 4 (good) and 3 (moderate)) in 96.6% of the 762 segments. Interobserver agreement was excellent (kappa ?0.90). Graft image quality was not affected by heart rate level. However, high heart rate variability was associated with an important and significant image quality deterioration (odds ratio 4.31; p ?=? 0.036). Distal graft segments had significantly lower image quality scores than proximal segments (p ? 0.02). Significantly higher noise was noted at the origin of the mammary grafts (p ?=? 0.001), owing to streak artifacts from the shoulders. Conclusion CABG imaging with 270-msec rotation 256-slice CT and prospective ECG-gating showed an adequate image quality in 96.6% of graft segments, and an excellent interobserver agreement. Graft image quality was not influenced by heart rate level. Image quality scores were however significantly decreased in patients with high heart rate variability, as well as in distal graft segments, which are closer to the heart. PMID:24637891

Gramer, Bettina M.; Diez Martinez, Patricia; Chin, Anne S.; Sylvestre, Marie-Pierre; Larrivée, Sandra; Stevens, Louis-Mathieu; Noiseux, Nicolas; Soulez, Gilles; Rummeny, Ernst J.; Chartrand-Lefebvre, Carl

2014-01-01

5

Prospective versus retrospective ECG-gated 64-detector coronary CT angiography for evaluation of coronary artery bypass graft patency: comparison of image quality, radiation dose and diagnostic accuracy  

Microsoft Academic Search

We aimed to evaluate image quality, radiation dose and diagnostic accuracy of coronary CT angiography (CCTA) with a prospectively\\u000a gated transverse-axial scan (PGT) compared with a retrospectively gated helical scan (RGH), using a 64-slice scanner in patients\\u000a who underwent coronary artery bypass graft (CABG). Of the 131 consecutive patients that underwent CABG using 64-slice multidetector\\u000a row computed tomography during 2008,

Jae Hwan Lee; Eun Ju Chun; Sang Il Choi; Mani Vembar; Cheong Lim; Kay-Hyun Park; Dong-Ju Choi

6

Coronary artery disease (image)  

MedlinePLUS

... through these arteries is critical for the heart. Coronary artery disease usually results from the build-up of fatty material and plaque, a condition called atherosclerosis. As the ... blood to the heart can slow or stop, causing chest pain (stable ...

7

Ultrasonic Imaging Of Deep Arteries  

NASA Technical Reports Server (NTRS)

Swept-frequency sound replaces pulsed sound. Ultrasonic medical instrument produces images of peripheral and coronary arteries with resolutions higher and at depths greater than attainable by previous ultrasonic systems. Time-delay-spectrometry imager includes scanning, image-processing, and displaying equipment. It sweeps in frequency from 0 to 10 MHz in 20 ms, pauses for 5 ms, and repeats sweep. Intended for use in noninvasive detection and measurement of atherosclerotic lesions.

Rooney, James A.; Heyser, Richard C.; Lecroissette, Dennis H.

1990-01-01

8

Prospectively versus Retrospectively ECG-Gated 256-Slice CT Angiography to Assess Coronary Artery Bypass Grafts — Comparison of Image Quality and Radiation Dose  

PubMed Central

Objective In this retrospective non-randomized cohort study, the image quality and radiation dose were compared between prospectively electrocardiogram (ECG)-gated axial (PGA) and retrospectively ECG-gated helical (RGH) techniques for the assessment of coronary artery bypass grafts using 256-slice CT. Methods We studied 124 grafts with 577 segments in 64 patients with a heart rate (HR) <85 bpm who underwent CT coronary angiography (CTCA); 34 patients with RGH-CTCA and 30 patients with PGA-CTCA. The image quality of the bypass grafts was assessed by a 5-point scale (1?=?excellent to 5?=?non-diagnostic) for each segment (proximal anastomosis, proximal, middle, distal course of graft body, and distal anastomosis). Other objective image quality indices such as noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) were assessed. Radiation doses were also compared. Results Patient characteristics of the two groups were well matched except HR. The HR of the PGA group was lower than that of the RGH group (62.0±5.0 vs. 65.7±7.4). For both groups, over 90% of segments received excellent or good image quality scores and none was non-evaluative. The image quality generally degraded as graft segment approached to distal anastomosis regardless of techniques and graft types. Image quality scores of the PGA group were better than those of the RGH group (1.51±0.53 vs. 1.73±0.62; p<0.001). There was no significantly difference of objective image quality between two techniques, and the effective radiation dose was significantly lower in the PGA group (7.0±1.2 mSv) than that of the RGH group (20.0±4.6 mSv) (p<0.001), with a 65.0% dose reduction. Conclusions Following bypass surgery, 256-slice PGA-CTCA is superior to RGH-CTCA in limiting the radiation dose and obtaining better image quality for bypass grafts. PMID:23145126

Lee, Yi-Wei; Yang, Ching-Ching; Mok, Greta S. P.; Law, Wei-Yip; Su, Cheng-Tau; Wu, Tung-Hsin

2012-01-01

9

Coronary artery wall imaging.  

PubMed

Like X-Ray contrast angiography, MR coronary angiograms show the vessel lumens rather than the vessels themselves. Consequently, outward remodeling of the vessel wall, which occurs in subclinical coronary disease before luminal narrowing, cannot be seen. The current gold standard for assessing the coronary vessel wall is intravascular ultrasound, and more recently, optical coherence tomography, both of which are invasive and use ionizing radiation. A noninvasive, low-risk technique for assessing the vessel wall would be beneficial to cardiologists interested in the early detection of preclinical disease and for the safe monitoring of the progression or regression of disease in longitudinal studies. In this review article, the current state of the art in MR coronary vessel wall imaging is discussed, together with validation studies and recent developments.J. Magn. Reson. Imaging. © 2014 Wiley Periodicals, Inc. PMID:25303707

Keegan, Jennifer

2014-10-01

10

Quality-aware images  

Microsoft Academic Search

We propose the concept of quality-aware image, in which certain extracted features of the original (high-quality) image are embedded into the image data as invisible hidden messages. When a distorted version of such an image is received, users can decode the hidden messages and use them to provide an objective measure of the quality of the distorted image. To demonstrate

Zhou Wang; Guixing Wu; Hamid Rahim Sheikh; Eero P. Simoncelli; En-Hui Yang; Alan Conrad Bovik

2006-01-01

11

Image quality evaluation  

Microsoft Academic Search

This paper is devoted to subjective and objective tests of image quality. The images were processed using different compressing algorithms (JPEG, KLT, Lura-wavelet) with compression ratio up to 100. After decompression they were tested on the quality changes. At first the subjective image quality test (DSCQS) was used. Then the objective quality test using the metric based on the human

Martin Bernas

2002-01-01

12

Location of foot arteries using infrared images  

NASA Astrophysics Data System (ADS)

In this work are presented the results of localization of foot arteries, in a young group of participants by using infrared thermal images, these are the dorsal, posterior tibial and anterior tibial arteries. No inclusion criteria were considered, that causes that no strong statistical data about the influence of the age in the arterial localization. It was achieved to solve the confusion when veins present a heat distribution similar to the artery and in the position of this. it contributes to enhance the rate of location of arteries. In general it is possible to say that the use of infrared thermal images is a good technique to find the foot arteries and can be applied in its characterization in a future. The procedure proposed is a non-invasive technique, and in certain fashion does not requires specialized personnel to achieve locate the arteries. It is portable, safe, and relatively economical.

Villasenor-Mora, Carlos; González-Vega, Arturo; Martín Osmany Falcón, Antonio; Benítez Ferro, Jesús Francisco Guillemo; Córdova Fraga, Teodoro

2014-11-01

13

Photoacoustic imaging of carotid artery atherosclerosis  

NASA Astrophysics Data System (ADS)

We introduce a method for photoacoustic imaging of the carotid artery, tailored toward detection of lipid-rich atherosclerotic lesions. A common human carotid artery was obtained at autopsy, embedded in a neck mimicking phantom and imaged with a multimodality imaging system using interstitial illumination. Light was delivered through a 1.25-mm-diameter optical probe that can be placed in the pharynx, allowing the carotid artery to be illuminated from within the body. Ultrasound imaging and photoacoustic signal detection is achieved by an external 8-MHz linear array coupled to an ultrasound imaging system. Spectroscopic analysis of photoacoustic images obtained in the wavelength range from 1130 to 1250 nm revealed plaque-specific lipid accumulation in the collagen structure of the artery wall. These spectroscopic findings were confirmed by histology.

Kruizinga, Pieter; van der Steen, Antonius F. W.; de Jong, Nico; Springeling, Geert; Robertus, Jan Lukas; van der Lugt, Aad; van Soest, Gijs

2014-11-01

14

Image Quality Evaluation in Security Imaging Systems  

Microsoft Academic Search

The subjective image quality of image or video information is a crucial item in security imaging systems. During the last five years our lab has tested and verified various approaches to the image compression for security purposes and the evaluation of subjective image quality. In the paper we discuss selected important facts related to the subjective image quality evaluation and

Milos Klima; Petr Pata; Karel Fliegel; Pavel Hanzlik

2007-01-01

15

Image quality evaluation using generalized natural image  

Microsoft Academic Search

Most image quality metrics are derived from feature values of specified test charts. However, such test charts can explain only a small portion of the comprehensive performances on image quality of imaging systems. Thus, designers of imaging systems need to check every possible type of natural image to verify the performance even if they check every image quality factor by

Kenji Kagitani

2008-01-01

16

Image quality evaluation of infrared image  

Microsoft Academic Search

According to the imaging procedure an infrared picture include an object image, a background image and a noise image. The object image and the background image are main body of an infrared image; noise image is the disturbance on the main body. This paper discusses the infrared image quality from three aspects: information capacity, image detail and pseudo-s\\/n ratio, it

Chun-mei Xu; Gang Li; Wengang Hu; Wei Zhang

2005-01-01

17

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

18

Noninvasive imaging of anomalous coronary arteries  

Microsoft Academic Search

Anomalous coronary arteries are a rare but recognized cause of myocardial ischemia and sudden death. Most patients with coronary anomalies remain asymptomatic because the anomaly either does not produce any symptoms during life or the first manifestation is sudden death. Noninvasive imaging plays crucial role in diagnosis of the potentially life threatening coronary anomalies.

Umair R. Qamar; Mutahir U. Khan; Ijaz A. Khan

2007-01-01

19

Thermal Imaging of the Superficial Temporal Artery: An Arterial Pulse Recovery Model  

E-print Network

. A multresolution wavelet-based signal analy- sis approach is used to extract the arterial pulse waveform, which limitation was the validation of the results. The reported arterial pulse wave- forms agreed with the groundThermal Imaging of the Superficial Temporal Artery: An Arterial Pulse Recovery Model Sergey Y

Farag, Aly A.

20

Imaging Food Quality Flemming Mller  

E-print Network

Imaging Food Quality Flemming Møller Kongens Lyngby 2012 IMM-PHD-2012-288 #12;Technical University Imaging and spectroscopy have long been established methods for food quality control both the image data to predict or visualise food quality. A range of different food quality parameters

21

Segmentation of Retinal Arteries in Adaptive Optics Images  

E-print Network

Segmentation of Retinal Arteries in Adaptive Optics Images Nicolas Lermé, Florence Rossant for automatically segmenting the walls of retinal arteries in adaptive optics images. To the best of our knowledge. INTRODUCTION The diseases affecting the retinal blood vessels of small diameter ( 150µm) such as arterial

Paris-Sud XI, Université de

22

Segmentation of Retinal Arteries in Adaptive Optics Images  

E-print Network

Segmentation of Retinal Arteries in Adaptive Optics Images Nicolas Lermé, Florence Rossant--In this paper, we present a method for automatically segmenting the walls of retinal arteries in adaptive optics, ap- proximate parallelism, retina imaging. I. INTRODUCTION Arterial hypertension (AH) and diabetic

Boyer, Edmond

23

An ultrasonic scanning system for arterial imaging  

NASA Technical Reports Server (NTRS)

A transcutaneous system for real-time imaging of arteries is described. A transducer probe containing three linear arrays of elements scans tissues within the element Fresnel zones. Each element is multiplexed in turn to a pulsed Doppler processor to permit real-time visualizations of moving targets. Applications of the motion-indicating B-scans are discussed, with special attention to problems in transcutaneous measurement of blood flow.

Hottinger, C. F.; Meindl, J. D.

1973-01-01

24

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

2012-03-01

25

Coronary MR Angiography Revealed: How to Optimize Image Quality.  

PubMed

Magnetic resonance (MR) imaging of the coronary arteries has been challenging, owing to the small size of the vessels and the complex motion caused by cardiac contraction and respiration. Free-breathing, whole-heart coronary MR angiography has emerged as a method that can provide visualization of the entire coronary arterial tree within a single 3-dimensional acquisition. Although coronary MR angiography is noninvasive and without radiation exposure, acquisition of high-quality coronary images is operator dependent and is generally more difficult than computed tomographic angiography. This article explains how to optimize acquisition of coronary MR angiography for reliable assessment of coronary artery disease. PMID:25476680

Ishida, Masaki; Sakuma, Hajime

2015-02-01

26

Foveated wavelet image quality index  

Microsoft Academic Search

The human visual system {(HVS)} is highly non-uniform in sampling, coding, processing and understanding. The spatial resolution of the {HVS} is highest around the point of fixation (foveation point) and decreases rapidly with increasing eccentricity. Currently, most image quality measurement methods are designed for uniform resolution images. These methods do not correlate well with the perceived foveated image quality. Wavelet

Zhou Wang; Alan C. Bovik; Ligang Lu; J. Kouloheris

2001-01-01

27

Comprehensive data visualization for high resolution endovascular carotid arterial wall imaging  

NASA Astrophysics Data System (ADS)

Carotid angioplasty and stenting is a minimally invasive endovascular procedure that may benefit from in vivo high resolution imaging for monitoring the physical placement of the stent and potential complications. The purpose of this pilot study was to evaluate the ability of optical coherence tomography to construct high resolution 2D and 3D images of stenting in porcine carotid artery. Four Yorkshire pigs were anaesthetized and catheterized. A state-of-the-art optical coherence tomography (OCT) system and an automated injector were used to obtain both healthy and stented porcine carotid artery images. Data obtained were then processed for visualization. The state-of-the-art OCT system was able to capture high resolution images of both healthy and stented carotid arteries. High quality 3D images of healthy and stented carotid arteries were constructed, clearly depicting vessel wall morphological features, stent apposition and thrombus formation over the inserted stent. The results demonstrate that OCT can be used to generate high quality 3D images of carotid arterial stents for accurate diagnosis of stent apposition and complications under appropriate imaging conditions.

Cheng, Kyle H. Y.; Sun, Cuiru; Cruz, Juan P.; Marotta, Thomas R.; Spears, Julian; Montanera, Walter J.; Thind, Aman; Courtney, Brian; Standish, Beau A.; Yang, Victor X. D.

2012-05-01

28

Evaluation of image quality  

NASA Technical Reports Server (NTRS)

This presentation outlines in viewgraph format a general approach to the evaluation of display system quality for aviation applications. This approach is based on the assumption that it is possible to develop a model of the display which captures most of the significant properties of the display. The display characteristics should include spatial and temporal resolution, intensity quantizing effects, spatial sampling, delays, etc. The model must be sufficiently well specified to permit generation of stimuli that simulate the output of the display system. The first step in the evaluation of display quality is an analysis of the tasks to be performed using the display. Thus, for example, if a display is used by a pilot during a final approach, the aesthetic aspects of the display may be less relevant than its dynamic characteristics. The opposite task requirements may apply to imaging systems used for displaying navigation charts. Thus, display quality is defined with regard to one or more tasks. Given a set of relevant tasks, there are many ways to approach display evaluation. The range of evaluation approaches includes visual inspection, rapid evaluation, part-task simulation, and full mission simulation. The work described is focused on two complementary approaches to rapid evaluation. The first approach is based on a model of the human visual system. A model of the human visual system is used to predict the performance of the selected tasks. The model-based evaluation approach permits very rapid and inexpensive evaluation of various design decisions. The second rapid evaluation approach employs specifically designed critical tests that embody many important characteristics of actual tasks. These are used in situations where a validated model is not available. These rapid evaluation tests are being implemented in a workstation environment.

Pavel, M.

1993-01-01

29

Imaging of the carotid artery vulnerable plaque.  

PubMed

Atherosclerosis involving the carotid arteries has a high prevalence in the population worldwide. This condition is significant because accidents of the carotid artery plaque are associated with the development of cerebrovascular events. For this reason, carotid atherosclerotic disease needs to be diagnosed and those determinants that are associated to an increased risk of stroke need to be identified. The degree of stenosis typically has been considered the parameter of choice to determine the therapeutical approach, but several recently published investigations have demonstrated that the degree of luminal stenosis is only an indirect indicator of the atherosclerotic process and that direct assessment of the plaque structure and composition may be key to predict the development of future cerebrovascular ischemic events. The concept of "vulnerable plaque" was born, referring to those plaque's parameters that concur to the instability of the plaque making it more prone to the rupture and distal embolization. The purpose of this review is to describe the imaging characteristics of "vulnerable carotid plaques." PMID:23912494

Saba, Luca; Anzidei, Michele; Marincola, Beatrice Cavallo; Piga, Mario; Raz, Eytan; Bassareo, Pier Paolo; Napoli, Alessandro; Mannelli, Lorenzo; Catalano, Carlo; Wintermark, Max

2014-06-01

30

Image quality metrics for the evaluation of print quality  

Microsoft Academic Search

Image quality metrics have become more and more popular in the image processing community. However, so far, no one has been able to define an image quality metric well correlated with the percept for overall image quality. One of the causes is that image quality is multi-dimensional and complex. One approach to bridge the gap between perceived and calculated image

Marius Pedersen; Nicolas Bonnier; Jon Y. Hardeberg; Fritz Albregtsen

2011-01-01

31

Arterial transit time imaging with flow encoding arterial spin tagging (FEAST)  

Microsoft Academic Search

Arterial spin labeling (ASL) perfusion imaging provides direct and absolute measurement of cerebral blood flow (CBF). Arte- rial transit time is a related physiological parameter reflecting the duration for the labeled spins to reach the brain region of interest. Most of the existing ASL approaches to assess arterial transit time rely on multiple measurements at various postla- beling delay times,

Jiongjiong Wang; David C. Alsop; Hee Kwon Song; Joseph A. Maldjian; Kathy Tang; Alana E. Salvucci; John A. Detre

2003-01-01

32

Crowdsourcing subjective image quality evaluation  

Microsoft Academic Search

Subjective tests are generally regarded as the most reliable and definitive methods for assessing image quality. Nevertheless, laboratory studies are time consuming and expensive. Thus, researchers often choose to run informal studies or use objective quality measures, producing results which may not correlate well with human perception. In this paper we propose a cost-effective and convenient subjective quality measure called

Flávio Ribeiro; Dinei A. F. Florencio; Vitor H. Nascimento

2011-01-01

33

Segmentation of coronary arteries from CT angiography images  

NASA Astrophysics Data System (ADS)

We present an automated method for delineation of coronary arteries from Cardiac CT Angiography (CTA) images. Coronary arteries are narrow blood vessels and when imaged using CTA, appear as thin cylindrical structures of varying curvature. This appearance is often affected by heart motion and image reconstruction artifacts. Moreover, when an artery is diseased, it may appear as a non-continuous structure of widely varying width and image intensity. Defining the boundaries of the coronary arteries is an important and necessary step for further analysis and diagnosis of coronary disease. For this purpose, we developed a method using cylindrical structure modeling. For each vessel segment a best fitting cylindrical template is found. By applying this technique sequentially along the vessel, its entire volume can be reconstructed. The algorithm is seeded with a manually specified starting point at the most distal discernible portion of an artery and then it proceeds iteratively toward the aorta. The algorithm makes necessary corrections to account for CTA image artifacts and is able to perform in diseased arteries. It stops when it identifies the vessels junction with the aorta. Five cardiac 3D CT angiography studies were used for algorithm validation. For each study, the four longest visually discernible branches of the major coronary arteries were evaluated. Central axes obtained from our automated method were compared with ground truth markings made by an experienced radiologist. In 75% of the cases, our algorithm was able to extract the entire length of the artery from single initialization.

Fotin, Sergei V.; Reeves, Anthony P.; Cham, Matthew D.; Henschke, Claudia I.; Yankelevitz, David F.

2007-03-01

34

"Mirror-Image" Bilateral Giants: Intracavernous Carotid Artery Aneurysms  

PubMed Central

Summary The literature on the incidence of "mirror image" bilateral giant intracavernous aneurysms, their symptoms and their association with other entities is reviewed, with a brief comment on their evolution and treatment. A case of "mirror image" bilateral giant intracavernous aneurysms in a 76-year-old man who presented a sudden diplopia with pupillary sparing is reported. A CT scan showed parasellar images and dolichomega circle of Willis arteries that enhanced with endovenous contrast. MRI and angiography disclose bilateral aneurysms in detail, associated with an anomalous origin of the left common carotid artery and bilateral renal artery stenosis. PMID:20569579

Díaz, M.B.; Mercado, F.C.; Lemme Plaghos, L.A.

2006-01-01

35

Retinal Image Quality During Accommodation  

PubMed Central

Purpose We asked if retinal image quality is maximum during accommodation, or sub-optimal due to accommodative error, when subjects perform an acuity task. Methods Subjects viewed a monochromatic (552nm), high-contrast letter target placed at various viewing distances. Wavefront aberrations of the accommodating eye were measured near the endpoint of an acuity staircase paradigm. Refractive state, defined as the optimum target vergence for maximising retinal image quality, was computed by through-focus wavefront analysis to find the power of the virtual correcting lens that maximizes visual Strehl ratio. Results Despite changes in ocular aberrations and pupil size during binocular viewing, retinal image quality and visual acuity typically remain high for all target vergences. When accommodative errors lead to sub-optimal retinal image quality, acuity and measured image quality both decline. However, the effect of accommodation errors of on visual acuity are mitigated by pupillary constriction associated with accommodation and binocular convergence and also to binocular summation of dissimilar retinal image blur. Under monocular viewing conditions some subjects displayed significant accommodative lag that reduced visual performance, an effect that was exacerbated by pharmacological dilation of the pupil. Conclusions Spurious measurement of accommodative error can be avoided when the image quality metric used to determine refractive state is compatible with the focusing criteria used by the visual system to control accommodation. Real focusing errors of the accommodating eye do not necessarily produce a reliably measurable loss of image quality or clinically significant loss of visual performance, probably because of increased depth-of-focus due to pupil constriction. When retinal image quality is close to maximum achievable (given the eye’s higher-order aberrations), acuity is also near maximum. A combination of accommodative lag, reduced image quality, and reduced visual function may be a useful sign for diagnosing functionally-significant accommodative errors indicating the need for therapeutic intervention. PMID:23786386

López-Gil, N.; Martin, J.; Liu, T.; Bradley, A.; Díaz-Muñoz, D.; Thibos, L.

2013-01-01

36

Intravascular Optical Imaging Technology for Investigating the Coronary Artery  

PubMed Central

There is an ever-increasing demand for new imaging methods that can provide additional information about the coronary wall to better characterize and stratify high-risk plaques, and to guide interventional and pharmacologic management of patients with coronary artery disease. While there are a number of imaging modalities that facilitate the assessment of coronary artery pathology, this review paper focuses on intravascular optical imaging modalities that provide information on the microstructural, compositional, biochemical, biomechanical, and molecular features of coronary lesions and stents. The optical imaging modalities discussed include angioscopy, optical coherence tomography, polarization sensitive-optical coherence tomography, laser speckle imaging, near-infrared spectroscopy, time-resolved laser induced fluorescence spectroscopy, Raman spectroscopy, and near-infrared fluorescence molecular imaging. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in the evaluation of the coronary artery in the future. PMID:21920342

Suter, Melissa J.; Nadkarni, Seemantini K.; Weisz, Giora; Tanaka, Atsushi; Jaffer, Farouc A.; Bouma, Brett E.; Tearney, Guillermo J.

2012-01-01

37

Quality assessment for hyperspectral imaging  

NASA Astrophysics Data System (ADS)

Image quality assessment is an essential value judgement approach for many applications. Multi & hyper spectral imaging has more judging essentials than grey scale or RGB imaging and its image quality assessment job has to cover up all-around evaluating factors. This paper presents an integrating spectral imaging quality assessment project, in which spectral-based, radiometric-based and spatial-based statistical behavior for three hyperspectral imagers are jointly executed. Spectral response function is worked out based on discrete illumination images and its spectral performance is deduced according to its FWHM and spectral excursion value. Radiometric response ability of different spectral channel under both on-ground and airborne imaging condition is judged by SNR computing based upon local RMS extraction and statistics method. Spatial response evaluation of the spectral imaging instrument is worked out by MTF computing with slanted edge analysis method. Reported pioneering systemic work in hyperspectral imaging quality assessment is carried out with the help of several domestic dominating work units, which not only has significance in the development of on-ground and in-orbit instrument performance evaluation technique but also takes on reference value for index demonstration and design optimization for instrument development.

Chen, Yuheng; Chen, Xinhua; Zhou, Jiankang; Shen, Weimin

2014-11-01

38

Foveated wavelet image quality index  

NASA Astrophysics Data System (ADS)

The human visual system (HVS) is highly non-uniform in sampling, coding, processing and understanding. The spatial resolution of the HVS is highest around the point of fixation (foveation point) and decreases rapidly with increasing eccentricity. Currently, most image quality measurement methods are designed for uniform resolution images. These methods do not correlate well with the perceived foveated image quality. Wavelet analysis delivers a convenient way to simultaneously examine localized spatial as well as frequency information. We developed a new image quality metric called foveated wavelet image quality index (FWQI) in the wavelet transform domain. FWQI considers multiple factors of the HVS, including the spatial variance of the contrast sensitivity function, the spatial variance of the local visual cut-off frequency, the variance of human visual sensitivity in different wavelet subbands, and the influence of the viewing distance on the display resolution and the HVS features. FWQI can be employed for foveated region of interest (ROI) image coding and quality enhancement. We show its effectiveness by using it as a guide for optimal bit assignment of an embedded foveated image coding system. The coding system demonstrates very good coding performance and scalability in terms of foveated objective as well as subjective quality measurement.

Wang, Zhou; Bovik, Alan C.; Lu, Ligang; Kouloheris, Jack L.

2001-12-01

39

Subjective image quality evaluation in security imaging systems  

Microsoft Academic Search

The subjective image quality of image or video information is a crucial item in security imaging systems. During last five years our lab has tested and verified various approaches to the image compression for security purposes and the evaluation of subjective image quality. In the paper, we have discussed selected important facts related to the subjective image quality evaluation and

M. Klima; P. Pata; K. Fliegel; P. Hanzlik

2005-01-01

40

Objective measurements of distorted image quality evaluation  

Microsoft Academic Search

Measurement of the quality of distorted image still remains an important issue. In this paper, we propose a new objective measurement, denoted as image quality score (IQS) that better matches the visual information fidelity (VIF) than using fundamental image quality measurements. IQS can be used to measure the quality of gray scale image in different distortion types such as blurring,

R. Sakuldee; S. Udomhunsakul

2008-01-01

41

Computerized measurement of mammographic display image quality  

Microsoft Academic Search

Since the video monitor is widely believed to be the weak link in the imaging chain, it is critical, to include it in the total image quality evaluation. Yet, most physical measurements of mammographic image quality are presently limited to making measurements on the digital matrix, not the displayed image. A method is described to quantitatively measure image quality of

Dev P. Chakraborty; Mahesh Sivarudrappa; Hans Roehrig

1999-01-01

42

Despeckle filtering software toolbox for ultrasound imaging of the common carotid artery.  

PubMed

Ultrasound imaging of the common carotid artery (CCA) is a non-invasive tool used in medicine to assess the severity of atherosclerosis and monitor its progression through time. It is also used in border detection and texture characterization of the atherosclerotic carotid plaque in the CCA, the identification and measurement of the intima-media thickness (IMT) and the lumen diameter that all are very important in the assessment of cardiovascular disease (CVD). Visual perception, however, is hindered by speckle, a multiplicative noise, that degrades the quality of ultrasound B-mode imaging. Noise reduction is therefore essential for improving the visual observation quality or as a pre-processing step for further automated analysis, such as image segmentation of the IMT and the atherosclerotic carotid plaque in ultrasound images. In order to facilitate this preprocessing step, we have developed in MATLAB(®) a unified toolbox that integrates image despeckle filtering (IDF), texture analysis and image quality evaluation techniques to automate the pre-processing and complement the disease evaluation in ultrasound CCA images. The proposed software, is based on a graphical user interface (GUI) and incorporates image normalization, 10 different despeckle filtering techniques (DsFlsmv, DsFwiener, DsFlsminsc, DsFkuwahara, DsFgf, DsFmedian, DsFhmedian, DsFad, DsFnldif, DsFsrad), image intensity normalization, 65 texture features, 15 quantitative image quality metrics and objective image quality evaluation. The software is publicly available in an executable form, which can be downloaded from http://www.cs.ucy.ac.cy/medinfo/. It was validated on 100 ultrasound images of the CCA, by comparing its results with quantitative visual analysis performed by a medical expert. It was observed that the despeckle filters DsFlsmv, and DsFhmedian improved image quality perception (based on the expert's assessment and the image texture and quality metrics). It is anticipated that the system could help the physician in the assessment of cardiovascular image analysis. PMID:24560276

Loizou, Christos P; Theofanous, Charoula; Pantziaris, Marios; Kasparis, Takis

2014-04-01

43

Adaptive fingerprint image enhancement with fingerprint image quality analysis  

E-print Network

images is heavily dependent on the quality of the fingerprint images. In order to improve the performance an adaptive preprocessing method to improve image quality appropriately. The preprocessing is performed afterAdaptive fingerprint image enhancement with fingerprint image quality analysis Eun-Kyung Yun, Sung

Cho, Sung-Bae

44

Development of photoacoustic radar imaging for endoscopy (coronary artery) diagnosis A novel intravascular imager technology of fatty acids in arteries responsible for heart disease and  

E-print Network

Development of photoacoustic radar imaging for endoscopy (coronary artery) diagnosis A novel intravascular imager technology of fatty acids in arteries responsible for heart disease and stroke is being and detectors capable of scanning circumferentially (tomographically) the inside of an artery around a full

45

Process perspective on image quality evaluation  

Microsoft Academic Search

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

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

2008-01-01

46

Imaging Biomarkers for Intra-arterial Stroke Therapy  

PubMed Central

Despite high rates of early revascularization with intra-arterial stroke therapy, the clinical efficacy of this approach has not been clearly demonstrated. Neuroimaging biomarkers will be useful in future trials for patient selection and for outcomes evaluation. To identify patients who are likely to benefit from intra-arterial therapy, the combination of vessel imaging, infarct size quantification and degree of neurologic deficit appears critical. Perfusion imaging may be useful in specific circumstances, but requires further validation. For measuring treatment outcomes, surrogate biomarkers that appear suitable are angiographic reperfusion as measured by the modified Thrombolysis in Cerebral Infarction scale and final infarct volume. PMID:24932316

Berkhemer, Olvert A.; Kamalian, Shervin; González, R. Gilberto; Majoie, Charles B. L. M.; Yoo, Albert J.

2014-01-01

47

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. PMID:21598344

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

2013-01-01

48

Molecular analysis of arterial remodeling: a novel application of infrared imaging  

NASA Astrophysics Data System (ADS)

Arterial remodeling, i.e. changes in size and/or structure of arteries, plays an important role in vascular disease. Conflicting findings have been reported as to whether an abundance of collagen causes inward or outward remodeling, phenomena that result in either a smaller or larger lumen, respectively. We hypothesize that the amount, type and quality of collagen influence the remodeling response. Here, we create mechanical injury to the rat carotid artery using a balloon catheter, and this leads to inward remodeling. Treatment of the artery with Connective Tissue Growth Factor (CTGF) causes outward remodeling. We investigated the arterial composition in injured CTGF-treated and non-CTGF-treated and sham CTGF-treated and non-CTGF treated arteries 14 days post-injury (n = 7-8 per group) using infrared imaging. A Perkin Elmer Spotlight Spectrum 300 FT-IR microscope was used for data collection. Cross-sections of paraffinembedded arteries were scanned at 2 cm-1 spectral resolution with spatial resolution of 6.25 ?m/pixel, and data analyzed using Malvern Instruments ISys 5.0. Post-injury, we found a nearly 50% reduction in the average 1338/AM2 area ratio (correlated to collagen helical integrity). The most dramatic change was a 600% increase in the 1660/1690 peak height ratio, which has previously been related to collagen crosslink maturity. In all cases, CTGF treatment resulted in the observed changes in peak parameters normalized back to control values. Overall, these preliminary studies demonstrate that infrared imaging can provide insight into the underlying molecular changes that contribute to arterial disease.

Herman, Brad C.; Kundi, Rishi; Yamanouchi, Dai; Kent, K. Craig; Liu, Bo; Pleshko, Nancy

2009-02-01

49

Quality Constrained Compression Using DWT Based Image Quality Metric  

E-print Network

of visual quality as well as estimates the post-compression quality of an image efficiently. Based, both the compression ratios and the qualities of the compressed images have to be considered. An ideal maintaining a good visual quality. In reality, it is always objective in measuring the compression ratio

Zheng, Yuan F.

50

Quantitative image analysis of histological sections of coronary arteries  

NASA Astrophysics Data System (ADS)

The study of coronary arteries has evolved from examining gross anatomy and morphology to scrutinizing micro-anatomy and cellular composition. Technological advances such as high- resolution digital microscopes and high precision cutting devices have allowed examination of coronary artery morphology and pathology at micron resolution. We have developed a software toolkit to analyze histological sections. In particular, we are currently engaged in examining normal coronary arteries in order to provide the foundation for study of remodeled tissue. The first of two coronary arteries was stained for elastin and collagen. The second coronary artery was sectioned and stained for cellular nuclei and smooth muscle. High resolution light microscopy was used to image the sections. Segmentation was accomplished initially with slice- to-slice thresholding algorithms. These segmentation techniques choose optimal threshold values by modeling the tissue as one or more distributions. Morphology and image statistics were used to further differentiate the thresholded data into different tissue categories therefore refine the results of the segmentation. Specificity/sensitivity analysis suggests that automatic segmentation can be very effective. For both tissue samples, greater than 90% specificity was achieved. Summed voxel projection and maximum intensity projection appear to be effective 3-D visualization tools. Shading methods also provide useful visualization, however it is important to incorporate combined 2-D and 3-D displays. Surface rendering techniques (e.g. color mapping) can be used for visualizing parametric data. Preliminary results are promising, but continued development of algorithms is needed.

Holmes, David R., III; Robb, Richard A.

2000-06-01

51

Degraded Character Recognition by Image Quality Evaluation  

Microsoft Academic Search

The character image quality plays an important role in degraded character recognition which could tell the recognition difficulty. This paper proposed a novel approach to degraded character recognition by three kinds of independent degradation sources. It is composed of two stems: character image quality evaluation, character recognition. Firstly, it presents the dual-evaluation to evaluate the image quality of the input

Chunmei Liu

2010-01-01

52

Pocket-size imaging devices allow for reliable bedside screening for femoral artery access site complications.  

PubMed

The aim of this study was to validate pocket-size imaging devices (PSIDs) as a fast screening tool for detecting complications after femoral artery puncture. Forty patients undergoing femoral artery puncture for arterial access related to percutaneous coronary intervention were enrolled. Twenty-four hours after percutaneous coronary intervention, the involved inguinal region was assessed with PSIDs enabling 2-D gray-scale and color Doppler imaging. Subsequently, examination with a stationary high-end ultrasound system was performed to verify the findings of bedside examination in all patients. In 37 patients, PSID imaging had good diagnostic quality. False aneurysms (one asymptomatic) occurred in four patients, and all were recognized during bedside screening with PSID. One case of femoral artery thrombosis was confirmed with PSID and during standard ultrasonographic examination. Physical examination augmented with the quick bedside PSID examination had a sensitivity of 100% and specificity of 91%. PSID facilitated rapid bedside detection of serious access site complications in the vast majority of patients, including asymptomatic cases. PMID:25308945

Filipiak-Strzecka, Dominika; Michalski, B?a?ej; Kasprzak, Jaros?aw D; Lipiec, Piotr

2014-12-01

53

Intraoperative imaging techniques to assess coronary artery bypass graft patency.  

PubMed

Graft patency verification is increasingly recognized as an important component of coronary artery bypass grafting. Intuitively, eliminating intraoperative graft failure should reduce cardiac mortality and morbidity in the short term and improve clinical outcome in the long term. Although conventional angiography remains the gold standard technique for assessing graft patency, it is rarely available in the operating room and consequently several other less invasive approaches have been advocated. This article reviews the two currently most commonly used modalities for graft patency assessment, intraoperative fluorescence imaging and transit-time flowmetry, and discusses their value and limitations. Both techniques can reliably detect otherwise unsuspected occluded grafts and this is crucial for internal thoracic arteries because of their prognostic significance. Although neither technology can consistently identify more minor, non-occlusive abnormalities, the intraoperative fluorescence imaging technique seems to be more sensitive and less susceptible to "false positive" images. PMID:17532450

Balacumaraswami, Lognathen; Taggart, David P

2007-06-01

54

Software for CRT image quality evaluation  

Microsoft Academic Search

This paper addresses image quality assessment and image quality maintenance of CRT displays for use as soft copy displays in digital radiology. Software is necessary to generate test patterns and to displays them on CRTs. CCD cameras record the images displayed on the CRTs. Additional software is necessary to analyze those images recorded by the CCD camera. This paper describes

Hans Roehrig; William J. Dallas; Hartwig R. Blume; Mahesh Sivarudrappa

2000-01-01

55

Assessment of coronary artery stenosis by magnetic resonance imaging.  

PubMed Central

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application. Images PMID:8673749

Pennell, D. J.; Bogren, H. G.; Keegan, J.; Firmin, D. N.; Underwood, S. R.

1996-01-01

56

Simulation and validation of arterial ultrasound imaging and blood flow.  

PubMed

We reviewed the simulation and validation of arterial ultrasound imaging and blood flow assessment. The physical process of ultrasound imaging and measurement is complex, especially in disease. Simulation of physiological flow in a phantom with tissue equivalence of soft tissue, vessel wall and blood is now achievable. Outstanding issues are concerned with production of anatomical models, simulation of arterial disease, refinement of blood mimics to account for non-Newtonian behavior and validation of velocity measurements against an independent technique such as particle image velocimetry. String and belt phantoms offer simplicity of design, especially for evaluation of velocity estimators, and have a role as portable test objects. Electronic injection and vibrating test objects produce nonphysiologic Doppler signals, and their role is limited. Computational models of the ultrasound imaging and measurement process offer considerable flexibility in their ability to alter multiple parameters of both the propagation medium and ultrasound instrument. For these models, outstanding issues are concerned with the inclusion of different tissue types, multilayer arteries, inhomogeneous tissues and diseased tissues. PMID:18329162

Hoskins, Peter R

2008-05-01

57

Analysis techniques for coronary arteries and cardiac function using advanced MRI and CT imaging  

E-print Network

Analysis techniques for coronary arteries and cardiac function using advanced MRI and CT imaging angiography is used to assess the coronary arteries due to its high spatial resolution, and MR is used by CT feasible, while new MR techniques increase the spatial resolution imaging the coronary arteries

Greenaway, Alan

58

Imaging of a Renal Artery Aneurysm Detected Incidentally on Ultrasonography  

PubMed Central

Renal artery aneurysms occur with a frequency of less than 1% of the general population. Even if they are usually asymptomatic and incidentally found, they can be complicated with life-threatening conditions like rupture, thrombosis, embolism, or hypertension. Thus, once diagnosed, they should be fully evaluated with further imaging and treated when indicated. We present the case of a patient who was referred for ultrasonography for an unrelated reason. The examination demonstrated a hyperechoic focus near the right kidney. Further imaging workup with MDCT established the diagnosis of a right renal artery aneurysm which was saccular in shape and peripherally calcified. This ring-like calcification was also visible in a KUB radiography which was also performed. After presenting the case, various aspects of this rare entity are discussed. PMID:24963433

Rafailidis, Vasileios; Gavriilidou, Anna; Liouliakis, Christos; Poultsaki, Maria; Theodoridis, Triantafyllos; Charalampidis, Vasileios

2014-01-01

59

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

60

Degradation Based Blind Image Quality Evaluation  

Microsoft Academic Search

\\u000a In this paper, we propose a novel framework for blind image quality evaluation. Unlike the common image quality measures evaluating\\u000a compression or transmission artifacts this approach analyzes the image properties common to non-ideal image acquisition such\\u000a as blur, under or over exposure, saturation, and lack of meaningful information. In contrast to methods used for adjusting\\u000a imaging parameters such as focus

Ville Ojansivu; Leena Lepistö; Martti Ilmoniemi; Janne Heikkilä

2011-01-01

61

Stereoscopic images quality assessment by jointly evaluating image quality and depth perception  

Microsoft Academic Search

Objective quality evaluation of stereoscopic images is useful in three-dimensional television application, and it is difficult to establish a reasonable relationship between objective evaluation and quality score. In this paper, a new stereoscopic image quality assessment method is proposed. In the method, stereoscopic features are first extracted to describe perceptual attributes of image quality and depth perception by singular value

Feng Shao; Shanbo Gu; Gangyi Jiang; Mei Yu

2012-01-01

62

A natural image quality evaluation metric  

Microsoft Academic Search

Reduced-reference (RR) image quality assessment (IQA) metrics evaluate the quality of a distorted (or degraded) image by using some, not all, information of the original (reference) image. In this paper, we propose a novel RR IQA metric based on hybrid wavelets and directional filter banks (HWD). With HWD as a pre-processing stage, the newly proposed metric mainly focuses on subbands

Xuelong Li; Dacheng Tao; Xinbo Gao; Wen Lu

2009-01-01

63

A practice of medical image quality evaluation  

Microsoft Academic Search

This paper is devoted to subjective\\/objective evaluation on medical image quality. A model based on neural network is proposed to mimic radiology doctors' perception. Medical images were compressed by different algorithms such as Dct and wavelet with different compression rate. After decompression, subjective and objective methods are used to evaluate image quality. Subjective rating is given by common person, clinic

Yun Zhou; Duo Chen; Chuan-fu Li; Xiao-ou Li; Huan-qing Feng

2003-01-01

64

Segmentation method of intravascular ultrasound images of human coronary arteries.  

PubMed

The goal of this study was to show the feasibility of a 2D segmentation fast-marching method (FMM) in the context of intravascular ultrasound (IVUS) imaging of coronary arteries. The original FMM speed function combines gradient-based contour information and region information, that is the gray level probability density functions of the vessel structures, that takes into account the variability in appearance of the tissues and the lumen in IVUS images acquired at 40 MHz. Experimental results on 38 in vivo IVUS sequences yielded mean point-to-point distances between detected vessel wall boundaries and manual validation contours below 0.11 mm, and Hausdorff distances below 0.33 mm, as evaluated on 3207 images. The proposed method proved to be robust in taking into account various artifacts in ultrasound images: partial shadowing due to calcium inclusions within the plaque, side branches adjacent to the main artery to segment, the presence of a stent, injection of contrast agent or dissection, as tested on 209 images presenting such artifacts. PMID:24119335

Destrempes, François; Roy Cardinal, Marie-Hélène; Allard, Louise; Tardif, Jean-Claude; Cloutier, Guy

2014-03-01

65

Use of intravascular imaging in managing coronary artery disease.  

PubMed

For many years, coronary angiography has been considered "the gold standard" for evaluating patients with coronary artery disease. However, angiography only provides a planar two-dimensional silhouette of the lumen and is unsuitable for the precise assessment of atherosclerosis. With the introduction of intravascular imaging, direct visualization of the arterial wall is now feasible. Intravascular imaging modalities extend diagnostic information, thereby enabling more precise evaluation of plaque burden and vessel remodeling. Of all technologies, intravascular ultrasound (IVUS) is the most mature and widely used intravascular imaging technique. Optical coherence tomography (OCT) is an evolving technology that has the highest spatial resolution of existing imaging methods, and it is becoming increasingly widespread. These methods are useful tools for planning interventional strategies and optimizing stent deployment, particularly when stenting complex lesions. We strongly support the mandatory use of IVUS for left main percutaneous coronary intervention (PCI). In addition, it can be used to evaluate vascular responses, including neointimal growth and strut apposition, during follow-ups. Adequately powered randomized trials are needed to support IVUS or OCT use in routine clinical practice and to answer whether OCT is superior to IVUS in reducing adverse events when used to guide PCI. The current perception and adoption of innovative interventional devices, such as bioabsorbable scaffolds, will increase the need for intravascular imaging in the future. PMID:24976911

Jegere, Sanda; Narbute, Inga; Erglis, Andrejs

2014-06-26

66

Use of intravascular imaging in managing coronary artery disease  

PubMed Central

For many years, coronary angiography has been considered “the gold standard” for evaluating patients with coronary artery disease. However, angiography only provides a planar two-dimensional silhouette of the lumen and is unsuitable for the precise assessment of atherosclerosis. With the introduction of intravascular imaging, direct visualization of the arterial wall is now feasible. Intravascular imaging modalities extend diagnostic information, thereby enabling more precise evaluation of plaque burden and vessel remodeling. Of all technologies, intravascular ultrasound (IVUS) is the most mature and widely used intravascular imaging technique. Optical coherence tomography (OCT) is an evolving technology that has the highest spatial resolution of existing imaging methods, and it is becoming increasingly widespread. These methods are useful tools for planning interventional strategies and optimizing stent deployment, particularly when stenting complex lesions. We strongly support the mandatory use of IVUS for left main percutaneous coronary intervention (PCI). In addition, it can be used to evaluate vascular responses, including neointimal growth and strut apposition, during follow-ups. Adequately powered randomized trials are needed to support IVUS or OCT use in routine clinical practice and to answer whether OCT is superior to IVUS in reducing adverse events when used to guide PCI. The current perception and adoption of innovative interventional devices, such as bioabsorbable scaffolds, will increase the need for intravascular imaging in the future. PMID:24976911

Jegere, Sanda; Narbute, Inga; Erglis, Andrejs

2014-01-01

67

Quality Metrics Evaluation of Hyperspectral Images  

NASA Astrophysics Data System (ADS)

In this paper, the quality metrics evaluation on hyperspectral images has been presented using k-means clustering and segmentation. After classification the assessment of similarity between original image and classified image is achieved by measurements of image quality parameters. Experiments were carried out on four different types of hyperspectral images. Aerial and spaceborne hyperspectral images with different spectral and geometric resolutions were considered for quality metrics evaluation. Principal Component Analysis (PCA) has been applied to reduce the dimensionality of hyperspectral data. PCA was ultimately used for reducing the number of effective variables resulting in reduced complexity in processing. In case of ordinary images a human viewer plays an important role in quality evaluation. Hyperspectral data are generally processed by automatic algorithms and hence cannot be viewed directly by human viewers. Therefore evaluating quality of classified image becomes even more significant. An elaborate comparison is made between k-means clustering and segmentation for all the images by taking Peak Signal-to-Noise Ratio (PSNR), Mean Square Error (MSE), Maximum Squared Error, ratio of squared norms called L2RAT and Entropy. First four parameters are calculated by comparing the quality of original hyperspectral image and classified image. Entropy is a measure of uncertainty or randomness which is calculated for classified image. Proposed methodology can be used for assessing the performance of any hyperspectral image classification techniques.

Singh, A. K.; Kumar, H. V.; Kadambi, G. R.; Kishore, J. K.; Shuttleworth, J.; Manikandan, J.

2014-11-01

68

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

69

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

70

A psychovisually-based image quality evaluator for JPEG images  

Microsoft Academic Search

We propose an algorithm for evaluating the quality of JPEG compressed images, called the psychovisually-based image quality evaluator (PIQE), which measures the severity of artifacts produced by JPEG compression. The PIQE evaluates the image quality using two psychovisually-based fidelity criteria: blockiness and similarity. The blockiness is an index that measures the patterned square artifact created as a by-product of the

R. W. Chan; P. B. Goldsmith

2000-01-01

71

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

72

Arterial Tortuosity Syndrome: An Approach through Imaging Perspective  

PubMed Central

This pictorial illustration demonstrates various aspects of arterial tortuosity syndrome (ATS) obtained predominantly from a multiple detector computed tomography (MDCT) examination of a patient. In addition, a comprehensive review of typical multi-modality imaging observations in patients with ATS is presented along with a description of a few imaging signs. Non-invasively obtained, conclusive information is required in patients with ATS in view of the fragile vascular structures involved. An amazing wealth of information can be obtained by reviewing the volumetric data sets of MDCT examination. In the context of incomplete clinical information or remote reading of radiographic examination with inadequate clinical details, ability to “image data mine” the hidden, unexplored information may be vastly useful. The role of MDCT as a single modality of evaluation in ATS is highlighted. PMID:25250193

Bhat, Venkatraman

2014-01-01

73

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

Microsoft Academic Search

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

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

2010-01-01

74

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

75

Quality of Life in Women with Coronary Artery Disease  

PubMed Central

Background: Coronary artery disease (CAD) as a chronic disease can affect physical, mental, and social aspects of health as well as the perception of wellbeing. Advanced treatments of the disease emphasize on functionality and quality of life (QOL). Objectives: The present study aimed to investigate the QOL and its related factors among women with CAD. Patients and Methods: This was a descriptive cross-sectional study conducted on 200 women with CAD, referring to the Heart Clinic of Shahid Rajaei Cardiovascular Center in Tehran, Iran. The participants were selected by convenient sampling method. Data were collected using the Persian version of Ferrans and Powers QOL index (QLI) cardiac version and then analyzed using descriptive statistics and statistical tests (independent t-test, one-way ANOVA, and Scheffe’s test). Results: The mean score of overall QOL was 16.91 ± 3.54, ranging between 7.17-27.63. Regarding the instrument subscales, the mean scores were as follows: health and functioning: 15.48 ± 4.32, social and economic: 16.18 ± 3.65, psychological/spiritual: 18.04 ± 4.36, and familial: 20.12 ± 4.57. There was a significant relationship between QOL and marital status (P = 0.004), education (P = 0.007), income (P < 0.001) and disease duration (P = 0.047). However, there was no significant association between QOL and age, job and comorbidity. Conclusions: Based on the findings, participants had average levels of overall QOL. Some domains showed the need to improve QOL of women with CAD. Results of the present study revealed the necessity of designing and performing educational and supportive interventions to improve the QOL in women with CAD, especially among patients with low socio-economic status. PMID:25237559

Ghasemi, Elham; Mohammad Aliha, Jaleh; Bastani, Farideh; Haghani, Hamid; Samiei, Niloufar

2014-01-01

76

Direct Characterization of Arterial Input Functions by Fluorescence Imaging of Exposed Carotid Artery to Facilitate Kinetic Analysis  

PubMed Central

Purpose With the goal of facilitating tracer kinetic analysis in small-animal planar fluorescence imaging, an experimental method for characterizing tracer arterial input functions is presented. The proposed method involves exposing the common carotid arteries by surgical dissection, which can then be imaged directly during tracer injection and clearance. Procedures Arterial concentration curves of IRDye-700DX-carboxylate, IRDye-800CW-EGF, and IRDye-800CW conjugated to anti-EGFR Affibody are recovered from athymic female mice (n=12) by directly imaging exposed vessels. Images were acquired with two imaging protocols: a slow-kinetics approach (temporal resolution=45 s) to recover the arterial curves from two tracers simultaneously, and a fast-kinetics approach (temporal resolution=500 ms) to characterize the first-pass peak of a single tracer. Arterial input functions obtained by the carotid imaging technique, as well as plasma curves measured by blood sampling were fit with a biexponential pharmacokinetic model. Results Pharmacological fast- and slow-phase rate constants recovered with the proposed method were 0.37±0.26 and 0.007±0.001 min?1, respectively, for the IRDye700DX-C. For the IRDye800CW-EGF, the rate constants were 0.11±0.13 and 0.003±0.002 min?1. These rate constants did not differ significantly from those calculated previously by blood sampling, as determined by an F test; however, the between-subject variability was four times lower for arterial curves recovered using the proposed technique, compared with blood sampling. Conclusions The proposed technique enables the direct characterization of arterial input functions for kinetic analysis. As this method requires no additional instrumentation, it is immediately deployable in commercially available planar fluorescence imaging systems. PMID:24420443

Elliott, Jonathan T.; Tichauer, Kenneth M.; Samkoe, Kimberley S.; Gunn, Jason R.; Sexton, Kristian J.; Pogue, Brian W.

2014-01-01

77

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

78

Peripheral Artery Wall Imaging Using Contrast-Enhanced, Susceptibility Weighted Phase Imaging  

PubMed Central

Purpose To demonstrate improved delineation of peripheral artery wall in susceptibility weighted imaging (SWI) phase images by utilizing gadolinium contrast agent. Materials and methods Superficial femoral arteries were imaged using high resolution SWI in 11 healthy volunteers before, and after injection of gadopentetate dimeglumine. Two post-contrast scans started 1 min and 11 mins after injection respectively. Eight out of the 11 volunteers also underwent double-inversion-recovery (DIR) turbo-spin-echo (TSE) scans. The same resolution and matrix size were used between SWI and TSE studies, and TSE locations were matched to SWI images. Arterial lumen-wall phase difference and phase contrast-to-noise ratio (CNR) were measured and compared between pre- and post-contrast SWI measurements. The lumen and wall areas measured on both TSE and matching SWI images were respectively analyzed for agreement. Another 2 volunteers participated in a double-echo gradient-echo study. Results were compared to SWI. Results By injecting gadolinium contrast agent, phase difference changed by 54.5% and ?1.6%, and phase CNR changed by 85.7% and 27.0%, for the 1st and 2nd post-contrast scans respectively. Morphological measurements showed insignificant difference between TSE and SWIs based on paired t-tests; good agreements in Bland-Altman plots were achieved. The double-echo gradient-echo study had similar phase measurements as SWI. Conclusion Contrast-enhanced phase imaging improves artery wall delineation in SWI of peripheral artery wall. Contrast-enhanced SWI is a promising vessel wall imaging technique. PMID:22261774

Liu, Qi; Fan, Zhaoyang; Yang, Qi; Li, Debiao

2011-01-01

79

An Edge Weighted RS image Quality Evaluation Method  

Microsoft Academic Search

The approaches for remote sensing (RS) image quality evaluation can be categorized by two different criteria. One is the subjective image quality testing based on many observers. The other is the objective image quality testing based on mathematical calculation. Compared with the subjective method, objective image quality testing is easier for implementation. However, the traditional objective image quality evaluation models,

Qin Lu; Liebo Du; Xuemin Xiao

2008-01-01

80

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

81

Pulmonary artery anatomy in congenital heart disease with decreased pulmonary blood flow by magnetic resonance imaging  

Microsoft Academic Search

We performed magnetic resonance imaging (MRI) in 65 patients (ages 8 days to 17 years old) with congenital heart disease accompanied by pulmonary atresia or stenosis, who had not undergone radical or functional repair of the heart to assess the usefulness of MRI in evaluating the pulmonary artery (PA) tree and calculating the diameter of the pulmonary arteries. Imaging was

Koichiro Niwa; Mika Uchishiba; Hiroyuki Aotsuka; Shigeru Tateno; Kimimasa Tobita; Hiromichi Hamada; Tadashi Fujiwara; Kozo Matsuo

1997-01-01

82

Visualization of Coronary Wall Atherosclerosis in Asymptomatic Subjects and Patients with Coronary Artery Disease Using Magnetic Resonance Imaging  

Microsoft Academic Search

BackgroundMagnetic resonance imaging (MRI) is sensitive to early atherosclerotic changes such as positive remodeling in patients with coronary artery disease (CAD). We assessed prevalence, quality, and extent of coronary atherosclerosis in a group of healthy subjects compared to patients with confirmed CAD.MethodologyTwenty-two patients with confirmed CAD (15M, 7F, mean age 60.4±10.4 years) and 26 healthy subjects without history of CAD

Suzanne C. Gerretsen; M. Eline Kooi; Alfons G. Kessels; Simon Schalla; Marcus Katoh; Rob J. van der Geest; Warren J. Manning; Johannes Waltenberger; Jos M. A. van Engelshoven; Rene M. Botnar; Tim Leiner

2010-01-01

83

Image quality metrics for volumetric laser displays  

NASA Astrophysics Data System (ADS)

This paper addresses the extensions to the image quality metrics and related human factors research that are needed to establish the baseline standards for emerging volume display technologies. The existing and recently developed technologies for multiplanar volume displays are reviewed with an emphasis on basic human visual issues. Human factors image quality metrics and guidelines are needed to firmly establish this technology in the marketplace. The human visual requirements and the display design tradeoffs for these prototype laser-based volume displays are addressed and several critical image quality issues identified for further research. The American National Standard for Human Factors Engineering of Visual Display Terminal Workstations (ANSIHFS-100) and other international standards (ISO, DIN) can serve as a starting point, but this research base must be extended to provide new image quality metrics for this new technology for volume displays.

Williams, Rodney D.; Donohoo, Daniel

1991-08-01

84

Blood vessel classification into arteries and veins in retinal images  

NASA Astrophysics Data System (ADS)

The prevalence of diabetes is expected to increase dramatically in coming years; already today it accounts for a major proportion of the health care budget in many countries. Diabetic Retinopathy (DR), a micro vascular complication very often seen in diabetes patients, is the most common cause of visual loss in working age population of developed countries today. Since the possibility of slowing or even stopping the progress of this disease depends on the early detection of DR, an automatic analysis of fundus images would be of great help to the ophthalmologist due to the small size of the symptoms and the large number of patients. An important symptom for DR are abnormally wide veins leading to an unusually low ratio of the average diameter of arteries to veins (AVR). There are also other diseases like high blood pressure or diseases of the pancreas with one symptom being an abnormal AVR value. To determine it, a classification of vessels as arteries or veins is indispensable. As to our knowledge despite the importance there have only been two approaches to vessel classification yet. Therefore we propose an improved method. We compare two feature extraction methods and two classification methods based on support vector machines and neural networks. Given a hand-segmentation of vessels our approach achieves 95.32% correctly classified vessel pixels. This value decreases by 10% on average, if the result of a segmentation algorithm is used as basis for the classification.

Kondermann, Claudia; Kondermann, Daniel; Yan, Michelle

2007-03-01

85

Toward clinically relevant standardization of image quality.  

PubMed

In recent years, notable progress has been made on standardization of medical image presentations in the definition and implementation of the Digital Imaging and Communications in Medicine (DICOM) Grayscale Standard Display Function (GSDF). In parallel, the American Association of Physicists in Medicine (AAPM) Task Group 18 has provided much needed guidelines and tools for visual and quantitative assessment of medical display quality. In spite of these advances, however, there are still notable gaps in the effectiveness of DICOM GSDF to assure consistent and high-quality display of medical images. In additions the degree of correlation between display technical data and diagnostic usability and performance of displays remains unclear. This article proposes three specific steps that DICOM, AAPM, and ACR may collectively take to bridge the gap between technical performance and clinical use: (1) DICOM does not provide means and acceptance criteria to evaluate the conformance of a display device to GSDF or to address other image quality characteristics. DICOM can expand beyond luminance response, extending the measurable, quantifiable elements of TG18 such as reflection and resolution. (2) In a large picture archiving and communication system (PACS) installation, it is critical to continually track the appropriate use and performance of multiple display devices. DICOM may help with this task by adding a Device Service Class to the standard to provide for communication and control of image quality parameters between applications and devices, (3) The question of clinical significance of image quality metrics has rarely been addressed by prior efforts. In cooperation with AAPM, the American College of Radiology (ACR), and the Society for Computer Applications in Radiology (SCAR), DICOM may help to initiate research that will determine the clinical consequence of variations in image quality metrics (eg, GSDF conformance) and to define what constitutes image quality from a diagnostic perspective. Implementation of these three initiatives may further the reach and impact of DICOM toward quality medicine. PMID:15551103

Samei, Ehsan; Rowberg, Alan; Avraham, Ellie; Cornelius, Craig

2004-12-01

86

Quality Improvement Guidelines for Uterine Artery Embolization for Symptomatic Leiomyomata  

Microsoft Academic Search

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,

David M. Hovsepian; Gary P. Siskin; Joseph Bonn; John F. Cardella; Timothy W. I. Clark; Leo E. Lampmann; Donald L. Miller; Reed A. Omary; Jean-Pierre Pelage; Dheeraj Rajan; Marc S. Schwartzberg; Richard B. Towbin; Woodruff J. Walker; David Sacks

2004-01-01

87

Perceptual image quality and telescope performance ranking  

Microsoft Academic Search

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

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

2010-01-01

88

Image content influences men's semen quality  

PubMed Central

There is increasing evidence from non-human animals that males adjust their ejaculate expenditure according to the risk of sperm competition. In this study we show that, after controlling for lifestyle factors known to influence semen quality, human males viewing images depicting sperm competition had a higher percentage of motile sperm in their ejaculates. Many lifestyle variables were confirmed to influence semen quality, including the recent suggestion that storage of mobile phones close to the testes can decrease semen quality. PMID:17148180

Kilgallon, Sarah J; Simmons, Leigh W

2005-01-01

89

Multimodality image fusion for diagnosing coronary artery disease  

PubMed Central

Coronary artery disease (CAD) is one of the leading causes of death in the US and a substantial health-care burden in all industrialized societies. In recent years we have witnessed a constant strive towards the development and the clinical application of novel or improved detection methods as well as therapies. Particularly, noninvasive imaging is a decisive component in the cardiovascular field. Image fusion is the ability of combining into a single integrated display the anatomical as well as the physiological data retrieved by separated modalities. Clinical evidence suggests that it represents a promising strategy in CAD assessment and risk stratification by significantly improving the diagnostic power of each modality independently considered and of the traditional side-by-side interpretation. Numerous techniques and approaches taken from the image registration field have been implemented and validated in the context of CAD assessment and management. Although its diagnostic power is widely accepted, additional technical developments are still needed to become a routinely used clinical tool. PMID:24285942

Piccinelli, Marina; Garcia, Ernest

2013-01-01

90

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.

2013-03-01

91

Subjective evaluation of compressed image quality  

Microsoft Academic Search

Lossy data compression generates distortion or error on the reconstructed image and the distortion becomes visible as the compression ratio increases. Even at the same compression ratio, the distortion appears differently depending on the compression method used. Because of the nonlinearity of the human visual system and lossy data compression methods, we have evaluated subjectively the quality of medical images

Heesub Lee; Alan H. Rowberg; Mark S. Frank; Hyung-Sik Choi; Yongmin Kim

1992-01-01

92

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

93

Image Quality Evaluation of HJ CCD Sensors  

Microsoft Academic Search

The Chinese HJ saterllite CCD sensor is similar to Landsat-5 TM with the same spatial resolution, but there are enormous advantages in space coverage and frequency of repeated observations. This paper focuses on the image quality evaluation of the four HJ CCD sensors by reference to Landsat TM data from near-synchronous images. The results are as follows: Mainly due to

Xiaolei Li; Rui Liu

2010-01-01

94

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

95

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

96

Long-term outcome and quality of life after arterial switch operation: a prospective study with a historical comparison.  

PubMed

AIM.: The study aims to describe the long-term cardiological and psychological results of our first surgical cohort of arterial switch operation (ASO) patients and compare the results with our earlier series of Mustard patients. METHODS.: Twenty-four survivors of ASO operated in our center (1985-1990) were evaluated by electrocardiography, echocardiography, magnetic resonance imaging, exercise testing, 24-hour Holter-monitoring, and health-related quality of life questionnaire. The results were compared with 58 adult Mustard patients who were evaluated in 2001 using the same study protocol. RESULTS.: Arterial switch operation was performed at a median age of 13 days and Mustard operation at 2 years. Median follow-up was 22 years (range 20-25) and 25 years (22-29), respectively. After ASO, survival was better (P =.04). The event-free survival after 22 years was 77% after ASO vs. 44% after Mustard (P =.03). Good systemic ventricular function was present in 93% after ASO vs. 6% after Mustard (P <.01). Exercise capacity in ASO was 85% of predicted, compared with 72% in Mustard patients (P =.01). Aortic regurgitation was found in 21% of ASO patients vs. 16% in Mustard patients. Arterial switch patients vs. Mustard patients reported significantly better quality of life and less somatic complaints. CONCLUSION.: The progression made in surgical treatment for transposition of the great arteries from Mustard to ASO has had a positive impact on survival, cardiac function, exercise capacity, and also self-reported quality of life and somatic complaints. Longer follow-up is warranted to monitor aortic regurgitation. PMID:23350828

Ruys, Titia P E; van der Bosch, Annemien E; Cuypers, Judith A A E; Witsenburg, Maarten; Helbing, Willem A; Bogers, Ad J J C; van Domburg, Ron; McGhie, Jacky S; Geleijnse, Marcel L; Henrichs, Jens; Utens, Elisabeth; Van der Zwaan, Heleen B; Takkenberg, Johanna J M; Roos-Hesselink, Jolien W

2013-01-01

97

Quality improvement guidelines for uterine artery embolization for symptomatic leiomyomata.  

PubMed

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. PMID:15346204

Hovsepian, David M; Siskin, Gary P; Bonn, Joseph; Cardella, John F; Clark, Timothy W I; Lampmann, Leo E; Miller, Donald L; Omary, Reed A; Pelage, Jean-Pierre; Rajan, Dheeraj; Schwartzberg, Marc S; Towbin, Richard B; Walker, Woodruff J; Sacks, David

2004-01-01

98

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

99

Image quality of optical remote sensing data  

NASA Astrophysics Data System (ADS)

Photogrammetry and remote sensing (RS) provide procedures for deriving geometric, radiometric and thematic information from image data. A variety of aircraft and space-borne sensors are available to capture image data. Different standards and specifications of quality assessment for optical remote sensing data are available. Due to the possibilities of absolute geometric and radiometric calibration digital sensors provide new promising opportunities to create value added products like digital elevation models, land-use maps etc. Such cameras combine the high geometric quality with the radiometric standards of earth observation systems. The determination of image quality of remote sensing data can be distinguished in (spectral) radiometric and geometric aspects. Standards contains different metrics for accuracy issues (spectral, radiometric and geometric accuracy) and for performance parameters like SNR, MTF. Image artefacts (caused e.g. by compression) are an additional important topic. The paper gives an overview of the current debate and the possibility of standardization.

Reulke, Ralf; Säuberlich, Thomas

2014-10-01

100

Practical usage of image quality verification tools  

NASA Astrophysics Data System (ADS)

Recent standards and upcoming guidelines are beginning to address the issue of image display quality, and image representation consistency. The DICOM standard has recently been extended to address the consistency of the grayscale presentation of images (DICOM part 14, Grayscale Standard Display Function), and it also addresses the consistency of presentation of associated information (text, graphics, annotation, zoom, rotation) with the recently approved addition of the Softcopy Presentation State, i.e. DICOM Supplement 33). These two new standards provide image consistency between viewing stations and printers independent of the manufacturer, brand and/or type. These services have been demonstrated at ECR, RSNA, and are also part of the continuing IHE demonstrations. In addition to the DICOM standards, work is being done by AAPM Task Group 18 to address the issue of Quality Control and Quality Assurance for electronic displays.

Compton, Kenneth D.; Hemminger, Bradley M.; Oosterwijk, Herman J.

2001-08-01

101

Two- and three-dimensional quantitative image analysis of coronary arteries from high-resolution histological sections  

NASA Astrophysics Data System (ADS)

The study of coronary arteries has evolved from examining gross anatomy and morphology to scrutinizing micro-anatomy and cellular composition. Technological advances such as high-powered digital microscopes and high precision cutting devices have allowed clinicians to examine coronary artery morphology and pathology at micron resolution. Our work explores the composition of normal coronary arteries in order to provide the foundation for further study of remodeled tissue. The first of two coronary arteries was sliced into 442 sections with 4 micron inter-slice spacing. Each slice was stained for elastin and collagen. The second coronary artery was sectioned into 283 slices, also with 4 micron resolution. These slices were stained for cellular nuclei and smooth muscle. High sectioned into 283 slices, also with 4 micron resolution. These slices were stained for cellular nuclei and smooth muscle. High resolution light microscopy was used to image the sections. The data was analyzed for collagen/elastin content and nuclei density, respectively. Processing of this type of data is challenging in the areas of segmentation, visualization and quantification. Segmentation was confounded by variation in image quality as well as complexity of the coronary tissue. These problems were overcome by the development of 'smart' thresholding algorithms for segmentation. In addition, morphology and image statistics were used to further refine the result of the segmentation. Specificity/sensitivity analysis suggests that automatic segmentation can be very effective. 3D visualization of coronary arteries is challenging due to multiple tissue layers. Method such as summed voxel projection and maximum intensity projection appear to be effective. Shading methods also provide adequate visualization, however it is important to incorporate combined 2D and 3D displays. Surface rendering techniques are useful tools for visualizing parametric data. Quantification in 3D is simple in practice but appropriate descriptions of these results must be displayed to clinicians in a clear way. Preliminary results are promising, but continued development of algorithms for processing histological data is needed.

Holmes, David R., III; Robb, Richard A.

2000-05-01

102

In vivo imaging of superficial femoral artery (SFA) stents for deformation analysis  

NASA Astrophysics Data System (ADS)

A high-resolution (198 ?m) C-arm CT imaging system (Axiom Artis dTA, Siemens Medical Solutions, Forchheim, Germany) was optimized for imaging superficial femoral artery (SFA) stents in humans. The SFA is susceptible to the development of atherosclerotic lesions. These are typically treated with angioplasty and stent deployment. However, these stents can have a fracture rate as high as 35%. Fracture is usually accompanied by restenosis and reocclusion. The exact cause of breakage is unknown and is hypothesized to result from deforming forces due to hip and knee flexion. Imaging was performed with the leg placed in both straight and bent positions. Projection images obtained during 20 s scans with ~200° of rotation of the C-arm were back-projected to obtain 3D volumes. Using a semi-automatic software algorithm developed in-house, the stent centerlines were found and ellipses were fitted to the slice normals. Image quality was adequate for calculations in 11/13 subjects. Bending the leg was found to shorten the stents in 10/11 cases with the maximum change being 9% (12 mm in a 133 mm stent), and extend the stent in one case by 1.6%. The maximum eccentricity change was 36% with a bend angle of 72° in a case where the stent extended behind the knee.

Ganguly, A.; Schneider, A.; Keck, B.; Bennett, N. R.; Fahrig, R.

2008-03-01

103

The effect of adaptive iterative dose reduction on image quality in 320-detector row CT coronary angiography  

PubMed Central

Objective To evaluate the effect of adaptive iterative dose reduction (AIDR) on image noise and image quality as compared with standard filtered back projection (FBP) in 320-detector row CT coronary angiography (CTCA). Methods 50 patients (14 females, mean age 68±9 years) who underwent CTCA (100 kV or 120 kV, 400–580 mA) within a single heartbeat were enrolled. Studies were reconstructed with FBP and subsequently AIDR. Image noise, vessel contrast and contrast-to-noise ratio (CNR) in the coronary arteries were evaluated. Overall image quality for coronary arteries was assessed using a five-point scale (1, non-diagnostic; 5, excellent). Results All the examinations were performed in a single heartbeat. Image noise in the aorta was significantly lower in data sets reconstructed with AIDR than in those reconstructed with FBP (21.4±3.1 HU vs 36.9±4.5 HU; p<0.001). No significant differences were observed between FBP and AIDR for the mean vessel contrast (HU) in the proximal coronary arteries. Consequently, CNRs in the proximal coronary arteries were higher in the AIDR group than in the FBP group (p<0.001). The mean image quality score was improved by AIDR (3.75±0.38 vs 4.24±0.38; p<0.001). Conclusion The use of AIDR reduces image noise and improves image quality in 320-detector row CTCA. PMID:22253355

Tatsugami, F; Matsuki, M; Nakai, G; Inada, Y; Kanazawa, S; Takeda, Y; Morita, H; Takada, H; Yoshikawa, S; Fukumura, K; Narumi, Y

2012-01-01

104

Parameter based SAR simulator for image quality evaluation  

Microsoft Academic Search

A SAR simulator for image quality evaluation is presented. This simulator can be used for the estimation of SAR image quality performance from the simulated raw data and the verification of the SAR payload design parameter associated with the image quality parameters. Evaluation of SAR image quality is achieved by analyzing the error effect of system parameter using the developed

Chul H. Jung; Min S. Choi; Young K. Kwag

2007-01-01

105

Computerized evaluation of mammographic image quality using phantom images  

Microsoft Academic Search

A simple, quick and computerized method for quantitatively evaluating the image quality of mammography phantom images has been developed. Images of the American College of Radiology (ACR) mammographic accreditation phantoms were acquired under different X-ray techniques, scored and ranked subjectively by five expert readers, and digitized for quantitative analysis. The contrast and signal-to-noise (contrast-to-noise) ratios of the main nodule and

Geoffrey Dougherty

1998-01-01

106

Signal and image processing for early detection of coronary artery diseases: A review  

NASA Astrophysics Data System (ADS)

Today biomedical signals and image based detection are a basic step to diagnose heart diseases, in particular, coronary artery diseases. The goal of this work is to provide non-invasive early detection of Coronary Artery Diseases relying on analyzing images and ECG signals as a combined approach to extract features, further classify and quantify the severity of DCAD by using B-splines method. In an aim of creating a prototype of screening biomedical imaging for coronary arteries to help cardiologists to decide the kind of treatment needed to reduce or control the risk of heart attack.

Mobssite, Youness; Samir, B. Belhaouari; Mohamad Hani, Ahmed Fadzil B.

2012-09-01

107

Image Quality Evaluation Method Based on the Relevant Parameters  

Microsoft Academic Search

Image quality evaluation is an important content of the Image Engineering, which plays an important role in the image communication process. Evaluation methods in general can be divided into objective and subjective quality evaluation methods. This paper analyzes the traditional full-reference image quality evaluation method and some of its shortcomings. Based on the analysis of image information and the relevance

Chunyan Han; Yemao Hou; Wenjia Wang

2009-01-01

108

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

109

Arterial Spin Labeled Myocardium Perfusion Imaging with Background Suppression , E. C. Wong2  

E-print Network

Arterial Spin Labeled Myocardium Perfusion Imaging with Background Suppression Z. Zun1 , E. C. Wong, La Jolla, CA, United States Introduction Arterial spin labeling (ASL) is widely used for assessing a saturation ­ inversion ­ inversion preparation scheme that is designed to suppress a broad range of T1s

Southern California, University of

110

Fast, pseudo-continuous arterial spin labeling for functional imaging using a two-coil system  

Microsoft Academic Search

A fast, two-coil, pseudo-continuous labeling scheme is pre- sented. This new scheme permits the collection of a multislice subtraction pair in <3 s, depending on the subject's arterial transit times. The method consists of acquiring both control and tag images immediately after a labeling period that matches the arterial transit time. The theoretical basis of the technique, and simulations of

Luis Hernandez-Garcia; Gregory R. Lee; Alberto L. Vazquez; Douglas C. Noll

2004-01-01

111

Multi-Modality Image Fusion to Guide Peripheral Artery Chronic Total Arterial Occlusion Recanalization in a Swine Carotid Artery Occlusion Model: Unblinding the Interventionalist!  

PubMed Central

Objectives To demonstrate the feasibility of magnetic resonance imaging (MRI) to x-ray fluoroscopy (XRF) image fusion to guide peripheral artery chronic total occlusion (CTO) recanalization. Background Endovascular peripheral artery CTO revascularization is minimally invasive, but challenging, because the occlusion is poorly visualized under XRF. Devices may steer out of the artery which can lead to severe perforation. Merging pre-acquired MRI of the CTO to the live XRF display may permit upfront use of aggressive devices and improve procedural outcomes. Methods Swine carotid artery CTO’s were created using a balloon injury model. Up to 8 weeks later, MRI of the carotid arteries was acquired and segmented to create 3D surface models, which were then registered onto live XRF. CTO recanalization was performed using incrementally aggressive CTO devices (Group A) or an upfront aggressive directed laser approach (Group B). Procedural success was defined as luminal or sub-intimal device position without severe perforation. Results In this swine model, MRI to XRF fusion guidance resulted in a procedural success of 57% in Group A and 100% in Group B, which compared favorably to 33% using XRF alone. Fluoroscopy time was significantly less for Group B (8.5 min ± 2.6 min) compared to Group A (48.7 min ± 23.9 min), p value<0.01. Contrast dose used was similar between Groups A and B. Conclusions MRI to XRF fusion guided peripheral artery CTO recanalization is feasible. Multi-modality image fusion may permit upfront use of aggressive CTO devices with improved procedural outcomes compared to XRF guided procedures. PMID:23097307

Klein, Andrew J.; Tomkowiak, Michael T.; Vigen, Karl K.; Hacker, Timothy A.; Speidel, Michael A.; VanLysel, Michael S.; Shah, Nehal; Raval, Amish N.

2012-01-01

112

Quality criteria for cardiac images: an update.  

PubMed

The DIMOND II and III Cardiology Groups have agreed on quality criteria for cardiac images and developed a scoring system, to provide a tool to test quality of coronary angiograms, which was demonstrated to be of value in clinical practice. In the last years, digital flat panel technology has been introduced in cardiac angiographic systems and the radiological technique may have been influenced by the better performance of these new detectors. This advance in digital imaging, together with the lesson learned from previous studies, warranted the revision of the quality criteria for cardiac angiographic images as formerly defined. DIMOND criteria were reassessed to allow a simpler evaluation of angiograms. Clinical criteria were simplified and separated from technical criteria. Furthermore, the characteristics of an optimised angiographic technique have been outlined. PMID:18283064

Bernardi, G; Bar, O; Jezewski, T; Vano, E; Maccia, C; Trianni, A; Padovani, R

2008-01-01

113

Cognitive, emotional, and quality of life outcomes in patients with pulmonary arterial hypertension  

PubMed Central

Background The effects of pulmonary arterial hypertension on cardiovascular and physical function are well documented. Limited information exists regarding the effects of pulmonary arterial hypertension on cognitive function despite patient reports of problems with memory and attention. Our primary purpose was to determine if a prospectively identified cohort of pulmonary arterial hypertension patients had cognitive sequelae. Our secondary purpose was to determine the relationships between cognitive sequelae and neuropsychological test scores with depression, anxiety, and quality of life. Methods Forty-six adults with pulmonary arterial hypertension underwent assessment of cognitive function, depression, anxiety, and quality of life using standardized neuropsychological tests and questionnaires. The patients' scores were compared to normal population data. Medical, affective, neuropsychological, and quality of life data for patients with and without cognitive sequelae were compared using analysis of variance, Chi-square, or Fisher exact tests for categorical data. Correlations assessed relationships between neuropsychological test scores, depression, anxiety, quality of life, and medical data. Results Cognitive sequelae occurred in 58% (27/46) of the pulmonary arterial hypertension patients. Patients with cognitive sequelae had worse verbal learning, delayed verbal memory, executive function, and fine motor scores compared to patients without cognitive sequelae. Twenty-six percent of patients had moderate to severe depression and 19% had moderate to severe anxiety. Depression, anxiety and quality of life were not different for patients with or without cognitive sequelae. Our patients had decreased quality of life, which was associated with worse working memory. Conclusion Patients with pulmonary arterial hypertension have cognitive impairments, depression, anxiety, and decreased quality of life. Depression, anxiety, and quality of life were similar for patients with cognitive sequelae compared to those without cognitive sequelae. Decreased quality of life was associated with worse verbal and working memory. Clinicians should be aware of adverse brain related outcomes in PAH patients. Attention to proximal determinants and possible interventions to prevent or reduce cognitive and emotional morbidity and decreased quality of life are warranted and should be an emphasis in outcomes research. PMID:16579853

White, Joanne; Hopkins, Ramona O; Glissmeyer, Eric W; Kitterman, Natalie; Elliott, C Gregory

2006-01-01

114

Lessions learned in WISE image quality  

NASA Astrophysics Data System (ADS)

The Wide-Field Infrared Survey Explorer (WISE) mission launched in December of 2009 is a true success story. The mission is performing beyond expectations on-orbit and maintained cost and schedule throughout. How does such a thing happen? A team constantly focused on mission success is a key factor. Mission success is more than a program meeting its ultimate science goals; it is also meeting schedule and cost goals to avoid cancellation. The WISE program can attribute some of its success in achieving the image quality needed to meet science goals to lessons learned along the way. A requirement was missed in early decomposition, the absence of which would have adversely affected end-to-end system image quality. Fortunately, the ability of the cross-organizational team to focus on fixing the problem without pointing fingers or waiting for paperwork was crucial in achieving a timely solution. Asking layman questions early in the program could have revealed requirement flowdown misunderstandings between spacecraft control stability and image processing needs. Such is the lesson learned with the WISE spacecraft Attitude Determination & Control Subsystem (ADCS) jitter control and the image data reductions needs. Spacecraft motion can affect image quality in numerous ways. Something as seemingly benign as different terminology being used by teammates in separate groups working on data reduction, spacecraft ADCS, the instrument, mission operations, and the science proved to be a risk to system image quality. While the spacecraft was meeting the allocated jitter requirement , the drift rate variation need was not being met. This missing need was noticed about a year before launch and with a dedicated team effort, an adjustment was made to the spacecraft ADCS control. WISE is meeting all image quality requirements on-orbit thanks to a diligent team noticing something was missing before it was too late and applying their best effort to find a solution.

Kendall, Martha; Duval, Valerie G.; Larsen, Mark F.; Heinrichsen, Ingolf H.; Esplin, Roy W.; Shannon, Mark; Wright, Edward L.

2010-08-01

115

Automating Image Enhancement Optimization Using Image Quality Metrics  

NASA Astrophysics Data System (ADS)

Image enhancement algorithms typically require tuning one or more input parameters to get the best results. Skipping this step or poor choice of values can often result in significant decrease in enhancement level or even degrade the image. This paper demonstrates the utility of image quality metrics in automating this tuning process for Space Situational Awareness imagery of resolved Resident Space Objects. The metrics considered in this study compare an original pristine image to the final displayed image, thus only apply directly to simulated images. However it is shown that a training set can be used to determine the best settings as a function of measureable imaging condition (light level, r0, …) to produce a look-up table that can be used for field collected data.

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

2014-09-01

116

Computer-generated 3D ultrasound images of the carotid artery  

NASA Technical Reports Server (NTRS)

A method is under development to measure carotid artery lesions from a computer-generated three-dimensional ultrasound image. For each image, the position of the transducer in six coordinates (x, y, z, azimuth, elevation, and roll) is recorded and used to position each B-mode picture element in its proper spatial position in a three-dimensional memory array. After all B-mode images have been assembled in the memory, the three-dimensional image is filtered and resampled to produce a new series of parallel-plane two-dimensional images from which arterial boundaries are determined using edge tracking methods.

Selzer, Robert H.; Lee, Paul L.; Lai, June Y.; Frieden, Howard J.; Blankenhorn, David H.

1989-01-01

117

Computer-generated 3D ultrasound images of the carotid artery  

NASA Astrophysics Data System (ADS)

A method is under development to measure carotid artery lesions from a computer-generated three-dimensional ultrasound image. For each image, the position of the transducer in six coordinates (x, y, z, azimuth, elevation, and roll) is recorded and used to position each B-mode picture element in its proper spatial position in a three-dimensional memory array. After all B-mode images have been assembled in the memory, the three-dimensional image is filtered and resampled to produce a new series of parallel-plane two-dimensional images from which arterial boundaries are determined using edge tracking methods.

Selzer, Robert H.; Lee, Paul L.; Lai, June Y.; Frieden, Howard J.; Blankenhorn, David H.

118

3DVIEWNIX-AVS: a software package for separate visualization of arteries and veins in CE-MRA images  

NASA Astrophysics Data System (ADS)

Our earlier study developed a computerized method, based on fuzzy connected object delineation principles and algorithms, for artery and vein separation in CE-MRA images. This paper reports its current development - a software package - for the routine clinical use. The software package, termed 3DVIEWNIX-AVS, consists of the following major operational parts: 1)converting data from DICOM3 to 3DVIEWNIX format, 2) previewing slices/creating VOI and MIP shell, 3) segmenting vessel, 4) separating artery and vein, 5) shell rendering vascular structures and creating animations. This package has been applied to EPIX Medical Inc's CE-MRA data (AngioMark MS-325). 133 original CE-MRA data sets (of 52 patients) from 6 hospitals have been processed. In all case studies, unified parameter settings produce correct artery/vein separation. The current package is running on a Pentium PC under Linux and the total operation time per study is about 10 minutes. The strengths of this software package are its 1) minimal user interaction, 2) minimal anatomic knowledge requirements on human vascular system, 3) clinically required speed, 4) free entry to any operational stages, 5) reproducible, reliable, high quality of results, and 6) cost effective computer implementation. To date, it seems to be the only software package (using an image processing approach) available for artery and vein separation for the routine use in a clinical setting.

Lei, Tianhu; Udupa, Jayaram K.; Odhner, Dewey; Saha, Punam K.

2001-05-01

119

Digital Image Processing Of Arterial Thrombi Images, Recorded By Light Transmission  

NASA Astrophysics Data System (ADS)

For several years, the formation and evolution of thrombi in small arteries of rats has been quantitatively studied at the Laboratory of Physiology and Physiopathology at the V.U.B. Global size parameters can be determined by projecting the image of a small arterial segment onto photosensitive cells. The transmitted light intensity is a measure for the thrombotic phenomenon. This unique method permitted extensive in vivo study of the platelet-vessel wall interaction and local thrombosis. Now, a further development has emerged with the aim to improve the resolution of these measurements in order to get information on texture and form of the thrombotic mass at any stage of its evolution. Therefore a thorough understanding of how light propagates through non hemolized blood was essential. For this purpose, the Medical Informatics department developed a system to record and process digital images of the thrombotic phenomenon. For the processing and attempt to reconstruct the thrombi, a model describing the light transmission in a dispersive medium such as flowing blood had to be worked out. Application of results from Twersky's multiple scattering theory, combined with appropriate border conditions and parameter values was attempted. In the particular situation we studied, the dispersive properties of the flowing blood were found to be highly anisotropic. An explanation for this phenomenon could be given by considering the alignment of red blood cells in the blood flow. In order to explain the measured intensity profiles, we had to postulate alignment in the plane perpendicular to the flow as well. The theoretical predictions are in good agreement with the experimental values if we assume almost perfect alignment of the erythrocytes such that their short axes are pointing in the direction of the center of the artery. Conclusive evidence of the interaction between local flow properties and light transmission could be found by observing arteries with perturbated flow.

Nyssen, Marc; Blockeel, Erik; Bourgain, Rene

1986-05-01

120

Image quality measures and their performance  

NASA Technical Reports Server (NTRS)

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. The two graphical measures (histograms and Hosaka plots), however, can be used to appropriately specify not only the amount, but also the type of degradation in reconstructed images.

Eskicioglu, Ahmet M.; Fisher, Paul S.; Chen, Si-Yuan

1994-01-01

121

Image quality evaluation: the data mining approach  

Microsoft Academic Search

It is difficult if not impossible to derive a model to adequately describe the entire visual, cognitive and preference decision process of image quality evaluation and to replace it with objective alternatives. Even if some parts of the process can be modeled based on the current knowledge of the visual system, there is often a lack of sufficient data to

Chengwu Cui

2004-01-01

122

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

123

Image quality evaluation based on human visual perception  

Microsoft Academic Search

This paper introduces two concepts of the traditional quality evaluation: the subjective evolution and objective evaluation, and then several kinds of common used human visual perception image quality judgment criterion are introduced, such as: assessing the quality of enhanced images based on human visual perception, image quality assessing model by using neural network and support vector machine, gradient information based

Fan Zhang; Yuli Xu

2009-01-01

124

Geometric assessment of image quality using digital image registration techniques  

NASA Technical Reports Server (NTRS)

Image registration techniques were developed to perform a geometric quality assessment of multispectral and multitemporal image pairs. Based upon LANDSAT tapes, accuracies to a small fraction of a pixel were demonstrated. Because it is insensitive to the choice of registration areas, the technique is well suited to performance in an automatic system. It may be implemented at megapixel-per-second rates using a commercial minicomputer in combination with a special purpose digital preprocessor.

Tisdale, G. E.

1976-01-01

125

Image Quality Indicator for Infrared Inspections  

NASA Technical Reports Server (NTRS)

The quality of images generated during an infrared thermal inspection depends on many system variables, settings, and parameters to include the focal length setting of the IR camera lens. If any relevant parameter is incorrect or sub-optimal, the resulting IR images will usually exhibit inherent unsharpness and lack of resolution. Traditional reference standards and image quality indicators (IQIs) are made of representative hardware samples and contain representative flaws of concern. These standards are used to verify that representative flaws can be detected with the current IR system settings. However, these traditional standards do not enable the operator to quantify the quality limitations of the resulting images, i.e. determine the inherent maximum image sensitivity and image resolution. As a result, the operator does not have the ability to optimize the IR inspection system prior to data acquisition. The innovative IQI described here eliminates this limitation and enables the operator to objectively quantify and optimize the relevant variables of the IR inspection system, resulting in enhanced image quality with consistency and repeatability in the inspection application. The IR IQI consists of various copper foil features of known sizes that are printed on a dielectric non-conductive board. The significant difference in thermal conductivity between the two materials ensures that each appears with a distinct grayscale or brightness in the resulting IR image. Therefore, the IR image of the IQI exhibits high contrast between the copper features and the underlying dielectric board, which is required to detect the edges of the various copper features. The copper features consist of individual elements of various shapes and sizes, or of element-pairs of known shapes and sizes and with known spacing between the elements creating the pair. For example, filled copper circles with various diameters can be used as individual elements to quantify the image sensitivity limit. Copper line-pairs of various sizes where the line width is equivalent to the spacing between the lines can be used as element-pairs to quantify the image resolution limit.

Burke, Eric

2011-01-01

126

Prediction of Viking lander camera image quality  

NASA Technical Reports Server (NTRS)

Formulations are presented that permit prediction of image quality as a function of camera performance, surface radiance properties, and lighting and viewing geometry. Predictions made for a wide range of surface radiance properties reveal that image quality depends strongly on proper camera dynamic range command and on favorable lighting and viewing geometry. Proper camera dynamic range commands depend mostly on the surface albedo that will be encountered. Favorable lighting and viewing geometries depend mostly on lander orientation with respect to the diurnal sun path over the landing site, and tend to be independent of surface albedo and illumination scattering function. Side lighting with low sun elevation angles (10 to 30 deg) is generally favorable for imaging spatial details and slopes, whereas high sun elevation angles are favorable for measuring spectral reflectances.

Huck, F. O.; Burcher, E. E.; Jobson, D. J.; Wall, S. D.

1976-01-01

127

1680 IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 15, NO. 6, JUNE 2006 Quality-Aware Images  

E-print Network

1680 IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 15, NO. 6, JUNE 2006 Quality-Aware Images Zhou the concept of quality-aware image, in which certain extracted features of the original (high-quality) image are embedded into the image data as invisible hidden messages. When a distorted version of such an image

Simoncelli, Eero

128

IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. XX, NO. XX, MONTH, YEAR 1 Quality-Aware Images  

E-print Network

IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. XX, NO. XX, MONTH, YEAR 1 Quality-Aware Images Zhou of quality-aware image, in which certain extracted features of the original (high-quality) image are embedded into the image data as invisible hidden messages. When a distorted version of such an image is received, users

Wang, Zhou

129

Cerebral Arterial Calcification Is an Imaging Prognostic Marker for Revascularization Treatment of Acute Middle Cerebral Arterial Occlusion  

PubMed Central

Background and Purpose To study the significance of intracranial artery calcification as a prognostic marker for acute ischemic stroke patients undergoing revascularization treatment after middle cerebral artery (MCA) trunk occlusion. Methods Patients with acute MCA trunk occlusion, who underwent intravenous and/or intra-arterial revascularization treatment, were enrolled. Intracranial artery calcification scores were calculated by counting calcified intracranial arteries among major seven arteries on computed tomographic angiography. Patients were divided into high (HCB; score ?3) or low calcification burden (LCB; score <3) groups. Demographic, imaging, and outcome data were compared, and whether HCB is a prognostic factor was evaluated. Grave prognosis was defined as modified Rankin Scale 5-6 for this study. Results Of 80 enrolled patients, the HCB group comprised 15 patients, who were older, and more commonly had diabetes than patients in the LCB group. Initial National Institutes of Health Stroke Scale (NIHSS) scores did not differ (HCB 13.3±2.7 vs. LCB 14.6±3.8) between groups. The final good reperfusion after revascularization treatment (thrombolysis in cerebral infarction score 2b-3, HCB 66.7% vs. LCB 69.2%) was similarly achieved in both groups. However, the HCB group had significantly higher NIHSS scores at discharge (16.0±12.3 vs. 7.9±8.3), and more frequent grave outcome at 3 months (57.1% vs. 22.0%) than the LCB group. HCB was proven as an independent predictor for grave outcome at 3 months when several confounding factors were adjusted (odds ratio 4.135, 95% confidence interval, 1.045-16.359, P=0.043). Conclusions Intracranial HCB was associated with grave prognosis in patients who have undergone revascularization for acute MCA trunk occlusion.

Lee, Seong-Joon; Hong, Ji Man; Lee, Manyong; Huh, Kyoon; Choi, Jin Wook

2015-01-01

130

MR and CT imaging of the structural and functional changes of pulmonary arterial hypertension  

PubMed Central

The current Dana Point classification system (2009) divides elevation of pulmonary artery pressure into Pulmonary Arterial Hypertension (PAH) and Pulmonary Hypertension (PH). Fortunately, pulmonary arterial hypertension (PAH) is not a common disease. However, with the aging of the first world’s population, heart failure is now an important cause of pulmonary hypertension with up to 9% of the population involved. PAH is usually asymptomatic until late in the disease process. While there are indirect features of PAH found on noninvasive imaging studies, the diagnosis and management still requires right heart catheterization. Imaging features of PAH include: 1. Enlargement of the pulmonary trunk and main pulmonary arteries, 2. Decreased pulmonary arterial compliance, 3. Tapering of the peripheral pulmonary arteries, 4. Enlargement of the inferior vena cava, and 5. Increased mean transit time. The chronic requirement to generate high pulmonary arterial pressures measurably affects the right heart and main pulmonary artery. This change in physiology causes the following structural and functional alterations that have been shown to have prognostic significance: Relative area change of the pulmonary trunk, RVSVindex, RVSV, RVEDVindex, LVEDVindex, and baseline RVEF <35%. All of these variables can be quantified non-invasively and followed longitudinally in each patient using MRI to modify the treatment regimen. Untreated PAH frequently results in a rapid clinical decline and death within 3 years of diagnosis. Unfortunately, even with treatment, less than 1/2 of these patients are alive at four years. PMID:23612440

Schiebler, Mark L.; Bhalla, Sanjeev; Runo, James; Jarjour, Nizar; Roldan, Alejandro; Chesler, Naomi; François, Christopher J.

2013-01-01

131

Quantitative Statistical Methods for Image Quality Assessment  

PubMed Central

Quantitative measures of image quality and reliability are critical for both qualitative interpretation and quantitative analysis of medical images. While, in theory, it is possible to analyze reconstructed images by means of Monte Carlo simulations using a large number of noise realizations, the associated computational burden makes this approach impractical. Additionally, this approach is less meaningful in clinical scenarios, where multiple noise realizations are generally unavailable. The practical alternative is to compute closed-form analytical expressions for image quality measures. The objective of this paper is to review statistical analysis techniques that enable us to compute two key metrics: resolution (determined from the local impulse response) and covariance. The underlying methods include fixed-point approaches, which compute these metrics at a fixed point (the unique and stable solution) independent of the iterative algorithm employed, and iteration-based approaches, which yield results that are dependent on the algorithm, initialization, and number of iterations. We also explore extensions of some of these methods to a range of special contexts, including dynamic and motion-compensated image reconstruction. While most of the discussed techniques were developed for emission tomography, the general methods are extensible to other imaging modalities as well. In addition to enabling image characterization, these analysis techniques allow us to control and enhance imaging system performance. We review practical applications where performance improvement is achieved by applying these ideas to the contexts of both hardware (optimizing scanner design) and image reconstruction (designing regularization functions that produce uniform resolution or maximize task-specific figures of merit). PMID:24312148

Dutta, Joyita; Ahn, Sangtae; Li, Quanzheng

2013-01-01

132

Fourier transform based scalable image quality measure.  

PubMed

We present a new image quality assessment (IQA) algorithm based on the phase and magnitude of the 2D (twodimensional) Discrete Fourier Transform (DFT). The basic idea is to compare the phase and magnitude of the reference and distorted images to compute the quality score. However, it is well known that the Human Visual Systems (HVSs) sensitivity to different frequency components is not the same. We accommodate this fact via a simple yet effective strategy of nonuniform binning of the frequency components. This process also leads to reduced space representation of the image thereby enabling the reduced-reference (RR) prospects of the proposed scheme. We employ linear regression to integrate the effects of the changes in phase and magnitude. In this way, the required weights are determined via proper training and hence more convincing and effective. Lastly, using the fact that phase usually conveys more information than magnitude, we use only the phase for RR quality assessment. This provides the crucial advantage of further reduction in the required amount of reference image information. The proposed method is therefore further scalable for RR scenarios. We report extensive experimental results using a total of 9 publicly available databases: 7 image (with a total of 3832 distorted images with diverse distortions) and 2 video databases (totally 228 distorted videos). These show that the proposed method is overall better than several of the existing fullreference (FR) algorithms and two RR algorithms. Additionally, there is a graceful degradation in prediction performance as the amount of reference image information is reduced thereby confirming its scalability prospects. To enable comparisons and future study, a Matlab implementation of the proposed algorithm is available at http://www.ntu.edu.sg/home/wslin/reduced_phase.rar. PMID:22562758

Narwaria, Manish; Lin, Weisi; McLoughlin, Ian; Emmanuel, Sabu; Chia, Liang-Tien

2012-08-01

133

Processor quality control in laser imaging systems.  

PubMed

Sensitometric techniques for performing processor quality control in laser imaging systems are analyzed in this study. The sensitivity of conventional x-ray films using simulated screen-light sensitometry is compared with helium-neon (HeNe) laser film exposed with a simulated red-light sensitometer, a standalone (reference) laser sensitometer, an experimental (unstable) laser sensitometer, and laser printers. Infrared (IR) laser film exposed with an IR laser diode and a simulated IR sensitometer are also evaluated. It is demonstrated that laser-generated step tablets provide an easy and reliable method of performing laser film processor quality control. PMID:9127311

Bogucki, T M; Murphy, W R; Baker, C W; Piazza, S S; Haus, A G

1997-04-01

134

Risk-Adjusted Survival after Coronary Artery Bypass Grafting: Implications for Quality Improvement  

PubMed Central

Mortality represents an important outcome measure following coronary artery bypass grafting. Shorter survival times may reflect poor surgical quality and an increased number of costly postoperative complications. Quality control efforts aimed at increasing survival times may be misleading if not properly adjusted for case-mix severity. This paper demonstrates how to construct and cross-validate efficiency-outcome plots for a specified time (e.g., 6-month and 1-year survival) after coronary artery bypass grafting, accounting for baseline cardiovascular risk factors. The application of this approach to regional centers allows for the localization of risk stratification rather than applying overly broad and non-specific models to their patient populations. PMID:25050654

Efird, Jimmy T.; O’Neal, Wesley T.; Davies, Stephen W.; O’Neal, Jason B.; Kindell, Linda C.; Anderson, Curtis A.; Chitwood, W. Randolph; Ferguson, T. Bruce; Kypson, Alan P.

2014-01-01

135

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

136

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

137

Development of functional in vivo imaging of cerebral lenticulostriate artery using novel synchrotron radiation angiography.  

PubMed

The lenticulostriate artery plays a vital role in the onset and development of cerebral ischemia. However, current imaging techniques cannot assess the in vivo functioning of small arteries such as the lenticulostriate artery in the brain of rats. Here, we report a novel method to achieve a high resolution multi-functional imaging of the cerebrovascular system using synchrotron radiation angiography, which is based on spatio-temporal analysis of contrast density in the arterial cross section. This method provides a unique tool for studying the sub-cortical vascular elasticity after cerebral ischemia in rats. Using this technique, we demonstrated that the vascular elasticity of the lenticulostriate artery decreased from day 1 to day 7 after transient middle cerebral artery occlusion in rats and recovered from day 7 to day 28 compared to the controls (p < 0.001), which paralleled with brain edema formation and inversely correlated with blood flow velocity (p < 0.05). Our results demonstrated that the change of vascular elasticity was related to the levels of brain edema and the velocity of focal blood flow, suggesting that reducing brain edema is important for the improvement of the function of the lenticulostriate artery in the ischemic brain. PMID:25632958

Lin, Xiaojie; Miao, Peng; Mu, Zhihao; Jiang, Zhen; Lu, Yifan; Guan, Yongjing; Chen, Xiaoyan; Xiao, Tiqiao; Wang, Yongting; Yang, Guo-Yuan

2015-02-21

138

Can eye movements be quantitatively applied to image quality studies?  

Microsoft Academic Search

The aim of the study is to find out whether subjective image quality evaluations can be quantified by eye movement tracking. We want to map objective or physically measurable image quality to subjective evaluations and eye movement data. Results show that eye movement parameters consistently change according to the instructions given to the user, and according to physical image quality.

Tero Vuori; Maria Olkkonen; Monika Pölönen; Ari Siren; Jukka Häkkinen

2004-01-01

139

Imaging of coronary artery stents using multislice computed tomography: in vitro evaluation  

Microsoft Academic Search

.   The aim of this study was to evaluate imaging features of different coronary artery stents during multislice CT Angiography\\u000a (MSCTA). Nineteen stents made of varying material (steel, nitinol, tantalum) and of varying stent design were implanted in\\u000a plastic tubes with an inner diameter of 3 mm to simulate a coronary artery. The tubes were filled with iodinated contrast\\u000a material diluted

David Maintz; Kai-Uwe Juergens; Thomas Wichter; Matthias Grude; Walter Heindel; Roman Fischbach

2003-01-01

140

A quantitative method for visual phantom image quality evaluation  

Microsoft Academic Search

This work presents an image quality evaluation technique for uniform-background target-object phantom images. The Degradation-Comparison-Threshold (DCT) method involves degrading the image quality of a target-containing region with a blocking processing and comparing the resulting image to a similarly degraded target-free region. The threshold degradation needed for 92% correct detection of the target region is the image quality measure of the

Dev P. Chakraborty; Xiong Liu; Michael O'Shea; Lawrence C. Toto

2000-01-01

141

Objective Assessment of Image Quality VI: Imaging in Radiation Therapy  

PubMed Central

Earlier work on Objective Assessment of Image Quality (OAIQ) focused largely on estimation or classification tasks in which the desired outcome of imaging is accurate diagnosis. This paper develops a general framework for assessing imaging quality on the basis of therapeutic outcomes rather than diagnostic performance. By analogy to Receiver Operating Characteristic (ROC) curves and their variants as used in diagnostic OAIQ, the method proposed here utilizes the Therapy Operating Characteristic or TOC curves, which are plots of the probability of tumor control vs. the probability of normal-tissue complications as the overall dose level of a radiotherapy treatment is varied. The proposed figure of merit is the area under the TOC curve, denoted AUTOC. This paper reviews an earlier exposition of the theory of TOC and AUTOC, which was specific to the assessment of image-segmentation algorithms, and extends it to other applications of imaging in external-beam radiation treatment as well as in treatment with internal radioactive sources. For each application, a methodology for computing the TOC is presented. A key difference between ROC and TOC is that the latter can be defined for a single patient rather than a population of patients. PMID:24200954

Barrett, Harrison H.; Kupinski, Matthew A.; Müeller, Stefan; Halpern, Howard J.; Morris, John C.; Dwyer, Roisin

2015-01-01

142

Objective assessment of image quality VI: imaging in radiation therapy  

NASA Astrophysics Data System (ADS)

Earlier work on objective assessment of image quality (OAIQ) focused largely on estimation or classification tasks in which the desired outcome of imaging is accurate diagnosis. This paper develops a general framework for assessing imaging quality on the basis of therapeutic outcomes rather than diagnostic performance. By analogy to receiver operating characteristic (ROC) curves and their variants as used in diagnostic OAIQ, the method proposed here utilizes the therapy operating characteristic or TOC curves, which are plots of the probability of tumor control versus the probability of normal-tissue complications as the overall dose level of a radiotherapy treatment is varied. The proposed figure of merit is the area under the TOC curve, denoted AUTOC. This paper reviews an earlier exposition of the theory of TOC and AUTOC, which was specific to the assessment of image-segmentation algorithms, and extends it to other applications of imaging in external-beam radiation treatment as well as in treatment with internal radioactive sources. For each application, a methodology for computing the TOC is presented. A key difference between ROC and TOC is that the latter can be defined for a single patient rather than a population of patients.

Barrett, Harrison H.; Kupinski, Matthew A.; Müeller, Stefan; Halpern, Howard J.; Morris, John C., III; Dwyer, Roisin

2013-11-01

143

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

144

Pulse Wave Imaging of the Human Carotid Artery: An In Vivo Feasibility Study  

PubMed Central

Noninvasive quantification of regional arterial stiffness, such as measurement of the pulse wave velocity (PWV), has been shown to be of high clinical importance. Pulse wave imaging (PWI) has been previously developed by our group to visualize the propagation of the pulse wave along the aorta and to estimate the regional PWV. The objective of this paper is to determine the feasibility of PWI in the human carotid artery in vivo. The left common carotid arteries of eight (n = 8) healthy volunteers (male, age 27 ± 4 years old) were scanned in a long-axis view, with a 10-MHz linear-array transducer. The beam density of the scan was reduced to 16 beams within an imaging width of 38 mm. The frame rate of ultrasound imaging was therefore increased to 1127 Hz at an image depth of 25 mm. The RF ultrasound signals were then acquired at a sampling rate of 40 MHz and used to estimate the velocity of the arterial wall using a 1-D cross-correlation-based speckle tracking method. The sequence of the wall velocity images at different times depicts the propagation of the pulse wave in the carotid artery from the proximal to distal sides. The regional PWV was estimated from the spatiotemporal variation of the wall velocities and ranged from 4.0 to 5.2 m/s in eight (n = 8) normal subjects, in agreement with findings reported in the literature. PWI was thus proven feasible in the human carotid artery, and may be proven useful for detecting vascular disease through mapping the pulse wave and estimating the regional PWV in the carotid artery. PMID:22293749

Luo, Jianwen; Li, Ronny X.; Konofagou, Elisa E.

2014-01-01

145

Scale-based approach for image quality evaluation  

Microsoft Academic Search

In images, anomalies such as edges or object boundaries take on a perceptual significance that is far greater than their numerical energy contribution to the image. Wavelet transform highlights these anomalies by representing them with significant coefficients. The contribution of a wavelet coefficient to the perceptual quality of the image is related to its magnitude. Degradation in image quality due

Kameswara R. Namuduri; Romain Murenzi; Lance M. Kaplan

1998-01-01

146

Compressed Image Quality Evaluation using Power Law Models  

Microsoft Academic Search

Abstract This paper ,presents a compressed ,image ,quality measure based on the properties of Zipf law, which is a power-law model ,adapted from linguistic analysis. It describes the frequency distribution of image patterns, and can be used ,to put ,into evidence image ,details which are affected by compression.,Two image quality evaluation measures ,based ,on Zipf ,law have ,been proposed and

Yves Caron; Nicole Vincent

2006-01-01

147

Analyzing the Quality of Supernovae Search Image Subtraction James Snitzer  

E-print Network

Analyzing the Quality of Supernovae Search Image Subtraction James Snitzer Adviser: John Marriner with template images of the same RA and DEC, the template images are aligned and subtracted from the reference images through the difference imaging pipeline script. The program that subtracts the two images

Cinabro, David

148

Hyperspectral and multispectral imaging for evaluating food safety and quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spectral imaging technologies have been developed rapidly during the past decade. This paper presents hyperspectral and multispectral imaging technologies in the area of food safety and quality evaluation, with an introduction, demonstration, and summarization of the spectral imaging techniques avai...

149

Ultrasound imaging media layer texture analysis of the carotid artery  

Microsoft Academic Search

The intima-media thickness (IMT) of the common carotid artery (CCA) is widely used as an early indicator of cardiovascular disease (CVD). It was proposed but not thoroughly investigated that the media layer (ML), its composition and texture, may be indicative for identifying the risk of stroke and differentiating between patients of high and low risk. In this study we investigate

C. P. Loizou; Marios Pantziaris; Andrew Nicolaides; A. Spanias; Marios S. Pattichis; Constantinos S. Pattichis

2008-01-01

150

Model-based quantification of image quality  

NASA Technical Reports Server (NTRS)

In 1982, Park and Schowengerdt published an end-to-end analysis of a digital imaging system quantifying three principal degradation components: (1) image blur - blurring caused by the acquisition system, (2) aliasing - caused by insufficient sampling, and (3) reconstruction blur - blurring caused by the imperfect interpolative reconstruction. This analysis, which measures degradation as the square of the radiometric error, includes the sample-scene phase as an explicit random parameter and characterizes the image degradation caused by imperfect acquisition and reconstruction together with the effects of undersampling and random sample-scene phases. In a recent paper Mitchell and Netravelli displayed the visual effects of the above mentioned degradations and presented subjective analysis about their relative importance in determining image quality. The primary aim of the research is to use the analysis of Park and Schowengerdt to correlate their mathematical criteria for measuring image degradations with subjective visual criteria. Insight gained from this research can be exploited in the end-to-end design of optical systems, so that system parameters (transfer functions of the acquisition and display systems) can be designed relative to each other, to obtain the best possible results using quantitative measurements.

Hazra, Rajeeb; Miller, Keith W.; Park, Stephen K.

1989-01-01

151

Enhancement Characteristics and Impact on Image Quality of Two Gadolinium Chelates at Equimolar Doses for Time-Resolved 3-Tesla MR-Angiography of the Calf Station  

PubMed Central

Purpose To compare enhancement characteristics and image quality of two macrocyclic gadolinium chelates, gadoterate meglumine and gadobutrol, in low-dose, time-resolved MRA of the calf station. Materials and Methods 100 consecutive patients with peripheral arterial disease (stages II-IV) were retrospectively analysed. Fifty patients were included in each group - 32 men and 18 women for gadobutrol (mean age 67 years) and 34 men, 16 women for gadoterate meglumine (mean age 64 years). 0.03 mmol/kg bw of either gadobutrol or gadoterate meglumine was injected. Gadobutrol was diluted 1?1 with normal saline (0.9% NaCl) to provide similar injection volume and bolus geometry compared to the undiluted 0.5 M dose of gadoterate meglumine. Signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and image quality were analysed and compared between the two groups. Results Mean SNR ranged from 83.0±46.7 (peroneal artery) to 96.4±64.5 (anterior tibial artery) for gadobutrol, and from 37.6±13.8 (peroneal artery) to 45.3±16.4 (anterior tibial artery) for the gadoterate meglumine group (p<0.0001). CNR values ranged from 30.1±20.1 (peroneal artery) to 37.6±26.0 (anterior tibial artery) for gadobutrol and from 14.9±8.0 (peroneal artery) to 18.6±16.4 (anterior tibial artery) for gadoterate meglumine (p<0.0001). No significant difference in image quality was found except for the peroneal arteries (p?=?0.006 and p?=?0.04). Interreader agreement was excellent (kappa 0.87–0.93) Conclusion The significantly better enhancement as assessed by SNR and CNR provided by gadobutrol compared to gadoterate meglumine does not translate into substantial differences in image quality in an equimolar, low-dose, time-resolved MRA protocol of the calves. PMID:24893292

Hansmann, Jan; Michaely, Henrik J.; Morelli, John N.; Luckscheiter, André; Schoenberg, Stefan O.; Attenberger, Ulrike I.

2014-01-01

152

Improving secondary ion mass spectrometry image quality with image fusion.  

PubMed

The spatial resolution of chemical images acquired with cluster secondary ion mass spectrometry (SIMS) is limited not only by the size of the probe utilized to create the images but also by detection sensitivity. As the probe size is reduced to below 1 ?m, for example, a low signal in each pixel limits lateral resolution because of counting statistics considerations. Although it can be useful to implement numerical methods to mitigate this problem, here we investigate the use of image fusion to combine information from scanning electron microscope (SEM) data with chemically resolved SIMS images. The advantage of this approach is that the higher intensity and, hence, spatial resolution of the electron images can help to improve the quality of the SIMS images without sacrificing chemical specificity. Using a pan-sharpening algorithm, the method is illustrated using synthetic data, experimental data acquired from a metallic grid sample, and experimental data acquired from a lawn of algae cells. The results show that up to an order of magnitude increase in spatial resolution is possible to achieve. A cross-correlation metric is utilized for evaluating the reliability of the procedure. PMID:24912432

Tarolli, Jay G; Jackson, Lauren M; Winograd, Nicholas

2014-12-01

153

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

154

On pictures and stuff: image quality and material appearance  

NASA Astrophysics Data System (ADS)

Realistic images are a puzzle because they serve as visual representations of objects while also being objects themselves. When we look at an image we are able to perceive both the properties of the image and the properties of the objects represented by the image. Research on image quality has typically focused improving image properties (resolution, dynamic range, frame rate, etc.) while ignoring the issue of whether images are serving their role as visual representations. In this paper we describe a series of experiments that investigate how well images of different quality convey information about the properties of the objects they represent. In the experiments we focus on the effects that two image properties (contrast and sharpness) have on the ability of images to represent the gloss of depicted objects. We found that different experimental methods produced differing results. Specifically, when the stimulus images were presented using simultaneous pair comparison, observers were influenced by the surface properties of the images and conflated changes in image contrast and sharpness with changes in object gloss. On the other hand, when the stimulus images were presented sequentially, observers were able to disregard the image plane properties and more accurately match the gloss of the objects represented by the different quality images. These findings suggest that in understanding image quality it is useful to distinguish between quality of the imaging medium and the quality of the visual information represented by that medium.

Ferwerda, James A.

2014-02-01

155

Automatic segmentation of arteries in multi-stain histology images L. Leal Taixe1, A. U. Coskun2, B. Rosenhahn1 and D. H. Brooks2  

E-print Network

Automatic segmentation of arteries in multi-stain histology images L. Leal Taix´e1, A. U. Coskun2 or Coronary Artery Disease (CAD) is a serious disease caused by the formation of plaque in the arteries detector is intro- duced to capture the area of the artery within the image. 2. We propose to create

156

Finger vein image quality evaluation using support vector machines  

NASA Astrophysics Data System (ADS)

In an automatic finger-vein recognition system, finger-vein image quality is significant for segmentation, enhancement, and matching processes. In this paper, we propose a finger-vein image quality evaluation method using support vector machines (SVMs). We extract three features including the gradient, image contrast, and information capacity from the input image. An SVM model is built on the training images with annotated quality labels (i.e., high/low) and then applied to unseen images for quality evaluation. To resolve the class-imbalance problem in the training data, we perform oversampling for the minority class with random-synthetic minority oversampling technique. Cross-validation is also employed to verify the reliability and stability of the learned model. Our experimental results show the effectiveness of our method in evaluating the quality of finger-vein images, and by discarding low-quality images detected by our method, the overall finger-vein recognition performance is considerably improved.

Yang, Lu; Yang, Gongping; Yin, Yilong; Xiao, Rongyang

2013-02-01

157

Image noise analysis with a fast lifting wavelet algorithm for objective image quality evaluation  

Microsoft Academic Search

An essential determinant of the value of surrogate 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

Gaoyong Luo

2004-01-01

158

Registration, segmentation, and visualization of confocal microscopy images of arterial thrombus  

NASA Astrophysics Data System (ADS)

Arterial thrombosis causes death or paralysis of an organ, as it migrates to and localizes in different parts of the body. Massive pulmonary emboli cause 50,000 deaths per year. The cause and origin of arterial thrombosis is not well understood nor objectively characterized. The object of this study was to investigate the microscopic structure of arterial thrombus to better understand this pathology. Confocal microscopy cross-sectional images of an embolized thrombus in the coronary artery were obtained. Adjacent pairs of sections were stained with two different stains, fibrin and CD61, to reveal mutually complementary information. The very thin adjacent slices were treated as one slice. Adjacent slices were registered by a combination of manual and automatic techniques using Analyze software developed in the Biomedical Imaging Resource at Mayo. After smoothing the images with a median filter, the CD61 and fibrin stained section images were used together to segment the tissues by multispectral classification. The image volume was classified into background, platelets and surrounding tissue, and thrombus. The segmented volume was then rendered for visualization and analysis of structure of the thrombus in three dimensions. Preliminary results are promising. Such correlation of structural and histological information may be helpful in determining the origin of the thrombus.

Garg, Ishita; Camp, Jon J.; McBane, Robert; Wysokinski, Waldemar; Robb, Richard A.

2004-05-01

159

Molecular imaging of plaques in coronary arteries with PET and SPECT  

PubMed Central

Coronary artery disease remains a major cause of mortality. Presence of atherosclerotic plaques in the coronary artery is responsible for lumen stenosis which is often used as an indicator for determining the severity of coronary artery disease. However, the degree of coronary lumen stenosis is not often related to compromising myocardial blood flow, as most of the cardiac events that are caused by atherosclerotic plaques are the result of vulnerable plaques which are prone to rupture. Thus, identification of vulnerable plaques in coronary arteries has become increasingly important to assist identify patients with high cardiovascular risks. Molecular imaging with use of positron emission tomography (PET) and single photon emission computed tomography (SPECT) has fulfilled this goal by providing functional information about plaque activity which enables accurate assessment of plaque stability. This review article provides an overview of diagnostic applications of molecular imaging techniques in the detection of plaques in coronary arteries with PET and SPECT. New radiopharmaceuticals used in the molecular imaging of coronary plaques and diagnostic applications of integrated PET/CT and PET/MRI in coronary plaques are also discussed. PMID:25278976

Sun, Zhong-Hua; Rashmizal, Hairil; Xu, Lei

2014-01-01

160

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

161

Parameter assessment for SAR image quality evaluation system  

Microsoft Academic Search

Synthetic Aperture Radar (SAR) image due to its special imaging method has many different characters from optical image. In this paper, a objective image quality evaluation system is proposed with a set of parameters and relevant measurements that mainly based on SAR image itself. And this evaluation system is supposed to be used by both satellite-borne and airborne SAR system.

Xin Lu; Hong Sun

2007-01-01

162

Image Quality Evaluation Model Based on Local Features and Segmentation  

Microsoft Academic Search

The perceived image distortion of any image is strongly de- pend on the local features, such as edge, flat and texture. A new objective no-reference (NR) image quality evaluation model based on local features and segmentation for JPEG coded image is presented in our previous paper, which is easy to calculate and applicable to various image processing ap- plications. But

Yuukou Horita; Masaharu Sato; Yoshikazu Kawayoke; Parvez Z. M. Sazzad; Keiji Shibata

2006-01-01

163

Wavelet-based foveated image quality measurement for region of interest image coding  

Microsoft Academic Search

Region of interest (ROI) image and video compression techniques have been widely used in visual communication applications in an effort to deliver good quality images and videos at limited bandwidths. Most image quality metrics have been developed for uniform resolution images. These metrics are not appropriate for the assessment of ROI coded images, where space-variant resolution is necessary. The spatial

Zhou Wang; Alan C. Bovik; Ligang Lu

2001-01-01

164

WAVELET-BASED FOVEATED IMAGE QUALITY MEASUREMENT FOR REGION OF INTEREST IMAGE CODING  

Microsoft Academic Search

Region of interest (ROI) image and video compression techniques have been widely used in visual communication applications in an effort to deliver good quality images and videos at limited bandwidths. Most image quality metrics have been developed for uniform resolution images. These metrics are not appropriate for the assessment of ROI coded images, where space-variant resolution is necessary. The spatial

Zhou Wang; Alan C. Bovik; Ligang Lu

2002-01-01

165

Signal quality quantification and waveform reconstruction of arterial blood pressure recordings.  

PubMed

Arterial blood pressure (ABP) is an important vital sign of the cardiovascular system. As with other physiological signals, its measurement can be corrupted by different sources of noise, interference, and artifact. Here, we present an algorithm for the quantification of signal quality and for the reconstruction of the ABP waveform in noise-corrupted segments of the measurement. The algorithm quantifies the quality of the ABP signal on a beat-by-beat basis by computing the normalized mean of successive differences of the ABP amplitude over each beat. In segments of poor signal quality, the ABP wavelets are then reconstructed on the basis of the expected cycle duration and envelope information derived from neighboring ABP wavelet segments. The algorithm was tested on two datasets of ABP waveform signals containing both invasive radial artery ABP and noninvasive ABP waveforms. Our results show that the approach is efficient in identifying the noisy segments (accuracy, sensitivity and specificity over 95%) and reliable in reconstructing beats that were artificially corrupted. PMID:25570431

Fanelli, A; Heldt, T

2014-08-01

166

[Health-related quality of life in the elderly after coronary artery bypass grafting].  

PubMed

Despite of higher operative risk in the elderly, coronary artery bypass grafting (CABG) is more often performed in this age group to achieve the remission of the disease and to improve the quality of life. The aim of the study was to assess some subjective and objective health indices in the elderly two years after CABG (I group) in comparison to analogous group of older patients just waiting for CABG (II group). 109 patients aged 65 years and older, consecutively discharged from the Cardiac Surgery Department 2 years ago, were analyzed as well as 60 patients currently waiting for such surgery. Both groups of patients did not differ with demographic features. The health related quality of life was measured with the EASYCare questionnaire and similar one of own construction supplemented with some items of the WHOQol-BREF scale. Two years after CABG, 100 patients were available for the study (six persons died and three persons refused). Response rate was 92%. Significant reduction of symptoms of the coronary artery disease were shown. The chest pain was declared in 18% in I group vs 70% in II group; palpitation in 23% in I group vs 38% in II group and effort angina in 38% in I group vs 65% in II group. The positive evaluation of the health status was declared significantly more often in the patients of I group in comparison to patients in II group. CABG caused positive change concerning health-related quality of life in the elderly two years after surgery. PMID:15850328

Lapi?ski, Tomasz; Bie?, Barbara; Wilma?ska, Jolanta

2004-01-01

167

Regional calcium distribution and ultrasound images of the vessel wall in human carotid arteries  

NASA Astrophysics Data System (ADS)

Arterial calcification can take place at two sites in the vessel wall: the intima and the media. Intimal calcification occurs exclusively within atherosclerotic plaques, while medial calcification may develop independently. Extensive calcified plaques in the carotid arteries can be easily detected by B-mode ultrasonic imaging. The calcium content might correlate with the ultrasound reflectance of the vessel wall, and could be a surrogate marker for arteriosclerosis. In this study, segments of human carotid arteries collected at autopsy were examined by ultrasonography in vitro and calcium distributional maps of sections from the same segments were determined by particle induced X-ray emission. Our aim was to make a first step towards investigating the relationship between the calcium distributional maps and the respective ultrasound images.

Szikszai, Z.; Kertész, Zs.; Uzonyi, I.; Szíki, G. Á.; Magyar, M. T.; Molnár, S.; Ida, Y.; Csiba, L.

2005-04-01

168

An Effect of Spatial Filtering in Visualization of Coronary Arteries Imaging  

E-print Network

At present, coronary angiography is the well known standard for the diagnosis of coronary artery disease. Conventional coronary angiography is an invasive procedure with a small, yet inherent risk of myocardial infarction, stroke, potential arrhythmias, and death. Other noninvasive diagnostic tools, such as electrocardiography, echocardiography, and nuclear imaging are now widely available but are limited by their inability to directly visualize and quantify coronary artery stenoses and predict the stability of plaques. Coronary magnetic resonance angiography (MRA) is a technique that allows visualization of the coronary arteries by noninvasive means; however, it has not yet reached a stage where it can be used in routine clinical practice. Although coronary MRA is a potentially useful diagnostic tool, it has limitations. Further research should focus on improving the diagnostic resolution and accuracy of coronary MRA. This paper will helps to cardiologists to take the clear look of spatial filtered imaging o...

Kodge, B G

2011-01-01

169

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

PubMed Central

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 0.63–0.69mm for the nominal 0.6mm slice and 0.82–0.87mm for the nominal 0.75mm slice. The visually determined through-plane (z axis) spatial resolution in a bar pattern phantom is 0.33–0.36mm for the nominal 0.6mm slice and 0.45mm for the nominal 0.75mm slice, again almost independent of the patient’s heart rate. The authors verify the theoretically expected temporal resolution of 83ms at 330ms gantry rotation time by blur free images of a moving coronary artery phantom with 90ms 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.

2008-01-01

170

Foveated Wavelet Image Quality Index* , Alan C. Bovika  

E-print Network

Foveated Wavelet Image Quality Index* Zhou Wanga , Alan C. Bovika , and Ligang Lub a Laboratory. The spatial resolution of the HVS is highest around the point of fixation (foveation point) and decreases for uniform resolution images. These methods do not correlate well with the perceived foveated image quality

Wang, Zhou

171

Pulse wave imaging of the human carotid artery: an in vivo feasibility study  

Microsoft Academic Search

Noninvasive quantification of regional arterial stiffness, such as measurement of the pulse wave velocity (PWV), has been shown to be of high clinical importance. Pulse wave imaging (PWI) has been previously developed by our group to visualize the propagation of the pulse wave along the aorta and to estimate the regional PWV. The objective of this paper is to determine

Jianwen Luo; Ronny Li; Elisa Konofagou

2012-01-01

172

Using short-wave infrared imaging for fruit quality evaluation  

NASA Astrophysics Data System (ADS)

Quality evaluation of agricultural and food products is important for processing, inventory control, and marketing. Fruit size and surface quality are two important quality factors for high-quality fruit such as Medjool dates. Fruit size is usually measured by length that can be done easily by simple image processing techniques. Surface quality evaluation on the other hand requires more complicated design, both in image acquisition and image processing. Skin delamination is considered a major factor that affects fruit quality and its value. This paper presents an efficient histogram analysis and image processing technique that is designed specifically for real-time surface quality evaluation of Medjool dates. This approach, based on short-wave infrared imaging, provides excellent image contrast between the fruit surface and delaminated skin, which allows significant simplification of image processing algorithm and reduction of computational power requirements. The proposed quality grading method requires very simple training procedure to obtain a gray scale image histogram for each quality level. Using histogram comparison, each date is assigned to one of the four quality levels and an optimal threshold is calculated for segmenting skin delamination areas from the fruit surface. The percentage of the fruit surface that has skin delamination can then be calculated for quality evaluation. This method has been implemented and used for commercial production and proven to be efficient and accurate.

Zhang, Dong; Lee, Dah-Jye; Desai, Alok

2013-12-01

173

Visualization of Coronary Wall Atherosclerosis in Asymptomatic Subjects and Patients with Coronary Artery Disease Using Magnetic Resonance Imaging  

PubMed Central

Background Magnetic resonance imaging (MRI) is sensitive to early atherosclerotic changes such as positive remodeling in patients with coronary artery disease (CAD). We assessed prevalence, quality, and extent of coronary atherosclerosis in a group of healthy subjects compared to patients with confirmed CAD. Methodology Twenty-two patients with confirmed CAD (15M, 7F, mean age 60.4±10.4 years) and 26 healthy subjects without history of CAD (11M, 15F, mean age 56.1±4.4 years) underwent MRI of the right coronary artery (RCA) and vessel wall (MR-CVW) on a clinical 1.5T MR-scanner. Wall thickness measurements of both groups were compared. Principal Findings Stenoses of the RCA (both < and ?50% on CAG) were present in all patients. In 21/22 patients, stenoses detected at MRI corresponded to stenoses detected with conventional angiography. In 19/26 asymptomatic subjects, there was visible luminal narrowing in the MR luminography images. Fourteen of these subjects demonstrated corresponding increase in vessel wall thickness. In 4/26 asymptomatic subjects, vessel wall thickening without luminal narrowing was present. Maximum and mean wall thicknesses in patients were significantly higher (2.16 vs 1.92 mm, and 1.38 vs 1.22 mm, both p<0.05). Conclusions In this cohort of middle-aged individuals, both patients with stable angina and angiographically proven coronary artery disease, as well as age-matched asymptomatic subjects. exhibited coronary vessel wall thickening detectable with MR coronary vessel wall imaging. Maximum and mean wall thicknesses were significantly higher in patients. The vast majority of asymptomatic subjects had either positive remodeling without luminal narrowing, or non-significant stenosis. Trial registration ClinicalTrials.gov NCT00456950 PMID:20927368

Gerretsen, Suzanne C.; Kooi, M. Eline; Kessels, Alfons G.; Schalla, Simon; Katoh, Marcus; van der Geest, Rob J.; Manning, Warren J.; Waltenberger, Johannes; van Engelshoven, Jos M. A.; Botnar, Rene M.; Leiner, Tim

2010-01-01

174

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

PubMed Central

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.

2013-01-01

175

Arterial Vulnerable Plaque Characterization Using Ultrasound-Induced Thermal Strain Imaging (TSI)  

Microsoft Academic Search

Thermal strain imaging (TSI) is demonstrated in two model systems mimicking two potential clinical applications. First, a custom ultrasound (US) microscope produced high-resolution TSI images of an excised porcine coronary artery. Samples were placed in a temperature-controlled water chamber and scanned transversely and longitudinally. Phase-sensitive, correlation-based speckle tracking was applied to map the spatial distribution of temporal strain across the

Kang Kim; Sheng-Wen Huang; Timothy L. Hall; Russell S. Witte; Thomas L. Chenevert; Matthew O'Donnell

2008-01-01

176

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. PMID:24146940

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

2013-01-01

177

Imaging of Unilateral Meningo-ophthalmic Artery Anomaly in a Patient with Bilateral Nasopharyngeal Angiofibroma  

PubMed Central

A 12-year-old boy with epistaxis presented with a rare midline nasopharyngeal angiofibroma that extended lateral into the pterygoid and infratemporal fossae. Pre-operative angiography revealed bilateral prominent feeder arteries and two major anastomotic connections, and a rare left meningo-ophthalmic artery (M-OA) anomaly that was the sole path of supply to the eye. A literature search using Pubmed and Medline was conducted. For imaging, a six-vessel study (i.e. external and internal carotid and vertebral arteries on both sides) was selected. Embolization of prominent tumor feeder arteries was unsafe for tumor extirpation, but super-selective embolization of both sphenopalatine arteries was performed to control epistaxis. The M-OA anomaly that originated from the maxillary artery (MA) was marked by an ophthalmic artery (OA) variant with orbital and ocular divisions that coursed through the superior orbital fissure and optic foramen, respectively, each with distinct branching patterns, a middle meningeal artery (MMA) with normal branches (i.e. anterior and posterior branches), and two branch variations (i.e. lacrimal and meningeal branches) that originated from the anterior branch of the MMA. The lacrimal branch coursed through a cranio-orbital foramen, but the meningeal branch remained outside the orbit. The anatomy of the right OA was normal. The left M-OA anomaly was considered incidental and not tumor-related since the tumor was more prominent on the right side, and no intra-orbital infiltrations occurred. Of clinical significance is that proximal embolization of MA or MMA carries a high risk of visual impairment in cases where M-OA anomalies are the sole mode of supply to the eye. PMID:25558432

Louw, Louise; Steyl, Johan; Loggenberg, Eugene

2014-01-01

178

Improving best-phase image quality in cardiac CT by motion correction with MAM optimization  

SciTech Connect

Purpose: Research in image reconstruction for cardiac CT aims at using motion correction algorithms to improve the image quality of the coronary arteries. The key to those algorithms is motion estimation, which is currently based on 3-D/3-D registration to align the structures of interest in images acquired in multiple heart phases. The need for an extended scan data range covering several heart phases is critical in terms of radiation dose to the patient and limits the clinical potential of the method. Furthermore, literature reports only slight quality improvements of the motion corrected images when compared to the most quiet phase (best-phase) that was actually used for motion estimation. In this paper a motion estimation algorithm is proposed which does not require an extended scan range but works with a short scan data interval, and which markedly improves the best-phase image quality. Methods: Motion estimation is based on the definition of motion artifact metrics (MAM) to quantify motion artifacts in a 3-D reconstructed image volume. The authors use two different MAMs, entropy, and positivity. By adjusting the motion field parameters, the MAM of the resulting motion-compensated reconstruction is optimized using a gradient descent procedure. In this way motion artifacts are minimized. For a fast and practical implementation, only analytical methods are used for motion estimation and compensation. Both the MAM-optimization and a 3-D/3-D registration-based motion estimation algorithm were investigated by means of a computer-simulated vessel with a cardiac motion profile. Image quality was evaluated using normalized cross-correlation (NCC) with the ground truth template and root-mean-square deviation (RMSD). Four coronary CT angiography patient cases were reconstructed to evaluate the clinical performance of the proposed method. Results: For the MAM-approach, the best-phase image quality could be improved for all investigated heart phases, with a maximum improvement of the NCC value by 100% and of the RMSD value by 81%. The corresponding maximum improvements for the registration-based approach were 20% and 40%. In phases with very rapid motion the registration-based algorithm obtained better image quality, while the image quality of the MAM algorithm was superior in phases with less motion. The image quality improvement of the MAM optimization was visually confirmed for the different clinical cases. Conclusions: The proposed method allows a software-based best-phase image quality improvement in coronary CT angiography. A short scan data interval at the target heart phase is sufficient, no additional scan data in other cardiac phases are required. The algorithm is therefore directly applicable to any standard cardiac CT acquisition protocol.

Rohkohl, Christopher; Bruder, Herbert; Stierstorfer, Karl [Siemens AG, Healthcare Sector, Siemensstrasse 1, 91301 Forchheim (Germany); Flohr, Thomas [Siemens AG, Healthcare Sector, Siemensstrasse 1, 91301 Forchheim (Germany); Institute of Diagnostic Radiology, Eberhard Karls University, Hoppe-Seyler-Str. 3, 72076 Tuebingen (Germany)

2013-03-15

179

Image quality characteristics of handheld display devices for medical imaging.  

PubMed

Handheld devices such as mobile phones and tablet computers have become widespread with thousands of available software applications. Recently, handhelds are being proposed as part of medical imaging solutions, especially in emergency medicine, where immediate consultation is required. However, handheld devices differ significantly from medical workstation displays in terms of display characteristics. Moreover, the characteristics vary significantly among device types. We investigate the image quality characteristics of various handheld devices with respect to luminance response, spatial resolution, spatial noise, and reflectance. We show that the luminance characteristics of the handheld displays are different from those of workstation displays complying with grayscale standard target response suggesting that luminance calibration might be needed. Our results also demonstrate that the spatial characteristics of handhelds can surpass those of medical workstation displays particularly for recent generation devices. While a 5 mega-pixel monochrome workstation display has horizontal and vertical modulation transfer factors of 0.52 and 0.47 at the Nyquist frequency, the handheld displays released after 2011 can have values higher than 0.63 at the respective Nyquist frequencies. The noise power spectra for workstation displays are higher than 1.2 × 10(-5) mm(2) at 1 mm(-1), while handheld displays have values lower than 3.7 × 10(-6) mm(2). Reflectance measurements on some of the handheld displays are consistent with measurements for workstation displays with, in some cases, low specular and diffuse reflectance coefficients. The variability of the characterization results among devices due to the different technological features indicates that image quality varies greatly among handheld display devices. PMID:24236113

Yamazaki, Asumi; Liu, Peter; Cheng, Wei-Chung; Badano, Aldo

2013-01-01

180

Image Quality Characteristics of Handheld Display Devices for Medical Imaging  

PubMed Central

Handheld devices such as mobile phones and tablet computers have become widespread with thousands of available software applications. Recently, handhelds are being proposed as part of medical imaging solutions, especially in emergency medicine, where immediate consultation is required. However, handheld devices differ significantly from medical workstation displays in terms of display characteristics. Moreover, the characteristics vary significantly among device types. We investigate the image quality characteristics of various handheld devices with respect to luminance response, spatial resolution, spatial noise, and reflectance. We show that the luminance characteristics of the handheld displays are different from those of workstation displays complying with grayscale standard target response suggesting that luminance calibration might be needed. Our results also demonstrate that the spatial characteristics of handhelds can surpass those of medical workstation displays particularly for recent generation devices. While a 5 mega-pixel monochrome workstation display has horizontal and vertical modulation transfer factors of 0.52 and 0.47 at the Nyquist frequency, the handheld displays released after 2011 can have values higher than 0.63 at the respective Nyquist frequencies. The noise power spectra for workstation displays are higher than 1.2×10?5 mm2 at 1 mm?1, while handheld displays have values lower than 3.7×10?6 mm2. Reflectance measurements on some of the handheld displays are consistent with measurements for workstation displays with, in some cases, low specular and diffuse reflectance coefficients. The variability of the characterization results among devices due to the different technological features indicates that image quality varies greatly among handheld display devices. PMID:24236113

Yamazaki, Asumi; Liu, Peter; Cheng, Wei-Chung; Badano, Aldo

2013-01-01

181

Studying Satellite Image Quality Based on the Fusion Techniques  

E-print Network

Various and different methods can be used to produce high-resolution multispectral images from high-resolution panchromatic image (PAN) and low-resolution multispectral images (MS), mostly on the pixel level. However, the jury is still out on the benefits of a fused image compared to its original images. There is also a lack of measures for assessing the objective quality of the spatial resolution for the fusion methods. Therefore, an objective quality of the spatial resolution assessment for fusion images is required. So, this study attempts to develop a new qualitative assessment to evaluate the spatial quality of the pan sharpened images by many spatial quality metrics. Also, this paper deals with a comparison of various image fusion techniques based on pixel and feature fusion techniques.

Al-Wassai, Firouz Abdullah; Al-Zaky, Ali A

2011-01-01

182

LANDSAT-4 image data quality analysis  

NASA Technical Reports Server (NTRS)

Work done on evaluating the geometric and radiometric quality of early LANDSAT-4 sensor data is described. Band to band and channel to channel registration evaluations were carried out using a line correlator. Visual blink comparisons were run on an image display to observe band to band registration over 512 x 512 pixel blocks. The results indicate a .5 pixel line misregistration between the 1.55 to 1.75, 2.08 to 2.35 micrometer bands and the first four bands. Also a four 30M line and column misregistration of the thermal IR band was observed. Radiometric evaluation included mean and variance analysis of individual detectors and principal components analysis. Results indicate that detector bias for all bands is very close or within tolerance. Bright spots were observed in the thermal IR band on an 18 line by 128 pixel grid. No explanation for this was pursued. The general overall quality of the TM was judged to be very high.

Anuta, P. E. (principal investigator)

1982-01-01

183

Polarization and retinal image quality estimates in the human eye  

Microsoft Academic Search

We have previously studied how polarization affects the double-pass estimates of the retinal image quality by using an imaging polarimeter (Opt. Lett. 24, 64 (1999)). A series of 16 images for independent combinations of polarization states in the polarimeter were recorded to obtain the spatially resolved Mueller matrices of the eye. From these matrices, double-pass images of a point source

Juan M. Bueno; Pablo Artal

2001-01-01

184

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

NASA Astrophysics Data System (ADS)

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, motion artifacts are suppressed by accelerated image acquisition triggered on cardiac and respiratory activity. In vivo TPLSM is performed on rat renal and mouse carotid arteries, both surgically exposed and labeled fluorescently (cell nuclei, elastin, and collagen). The use of short acquisition times consistently limit in-frame motion artifacts. Additionally, triggered imaging reduces between-frame artifacts. Indeed, structures in the vessel wall (cell nuclei, elastic laminae) can be imaged at subcellular resolution. In mechanically damaged carotid arteries, even the subendothelial collagen sheet (~1 ?m) is visualized using collagen-targeted quantum dots. We demonstrate stable in vivo imaging of large arteries at subcellular resolution using TPLSM triggered on cardiac and respiratory cycles. This creates great opportunities for studying (diseased) arteries in vivo or immediate validation of in vivo molecular imaging techniques such as magnetic resonance imaging (MRI), ultrasound, and positron emission tomography (PET).

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

2010-01-01

185

Quality Measures for Image Segmentation Using Generated Images Theo E. Schouten, Maurice S. klein Gebbinck  

E-print Network

Quality Measures for Image Segmentation Using Generated Images Theo E. Schouten, Maurice S. klein measure of the quality of a segmentation of an image a ''true'' segmentation must be known is described to generate a realistic satellite image and its true segmentation to sub­pixel level using ground

Schouten, Theo

186

An image quality evaluation tool simulating image sensors including quantum efficiency off-axis effect  

Microsoft Academic Search

The image quality evaluation of CMOS sensors is a big challenge for camera module manufacturers. In this paper, we present an update of the Image Quality Evaluation Tool, a graphical user interface simulating image sensors to assess the performance of a pixel. The simulated images are computed from operating conditions and sensor's characteristics like Quantum Efficiency including off-axis effect. Simulation

Clémence Mornet; Jérôme Vaillant; Thomas Decroux; Nicolas Virollet; Didier Herault; Isabelle Schanen

2011-01-01

187

Searching for the limit of image quality in film radiography  

SciTech Connect

Radiographic film image quality in general was, and in most cases still is, considered as a very subjective and rather vague parameter. Yet it is of vital importance to the NDT and related quality control and quality assurance industry. Therefore, lately Agfa has put a major effort into quantifying image quality in an objective, measurable way. It was in the framework of this optimization project, that the authors, based on these new insights in imaging of industrial film systems, strived to search for the limit of the highest achievable image quality. In this paper they report these results. They not only report these results in an academic way, meaning how this highest image quality can be achieved under lab conditions, but also how these same results can be obtained under practical e.g. field-conditions.

Vaessen, B.; Perdieus, P.; Florens, R. [Agfa Gevaert N.V., Mortsel (Belgium). Business Unit NDT

1993-12-31

188

Contrast sensitivity function calibration based on image quality prediction  

NASA Astrophysics Data System (ADS)

Contrast sensitivity functions (CSFs) describe visual stimuli based on their spatial frequency. However, CSF calibration is limited by the size of the sample collection and this remains an open issue. In this study, we propose an approach for calibrating CSFs that is based on the hypothesis that a precise CSF model can accurately predict image quality. Thus, CSF calibration is regarded as the inverse problem of image quality prediction according to our hypothesis. A CSF could be calibrated by optimizing the performance of a CSF-based image quality metric using a database containing images with known quality. Compared with the traditional method, this would reduce the work involved in sample collection dramatically. In the present study, we employed three image databases to optimize some existing CSF models. The experimental results showed that the performance of a three-parameter CSF model was better than that of other models. The results of this study may be helpful in CSF and image quality research.

Han, Yu; Cai, Yunze

2014-11-01

189

The role of completion imaging following carotid artery endarterectomy.  

PubMed

A variety of completion imaging methods can be used during carotid endarterectomy to recognize technical errors or intrinsic abnormalities such as mural thrombus or platelet aggregation, but none of these methods has achieved wide acceptance, and their ability to improve the outcome of the operation remains a matter of controversy. It is unclear if completion imaging is routinely necessary and which abnormalities require re-exploration. Proponents of routine completion imaging argue that identification of these abnormalities will allow their immediate correction and avoid a perioperative stroke. However, much of the evidence in favor of this argument is incidental, and many experienced vascular surgeons who perform carotid endarterectomy do not use any completion imaging technique and report equally good outcomes using a careful surgical protocol. Furthermore, certain postoperative strokes, including intracerebral hemorrhage and hyperperfusion syndrome, are unrelated to the surgical technique and cannot be prevented by completion imaging. This controversial subject is now open to discussion, and our debaters have been given the task to clarify the evidence to justify their preferred option for completion imaging during carotid endarterectomy. PMID:23601598

Ricco, Jean-Baptiste; Schneider, Fabrice; Illuminati, Giulio; Samson, Russell H

2013-05-01

190

Heart imaging: the accuracy of the 64-MSCT in the detection of coronary artery disease.  

PubMed

At present, coronary angiography represents the gold standard technique for the diagnosis of coronary artery disease. Our aim is to compare the conventional coronary angiography to the coronary 64-multislice spiral computed tomography (64-MSCT), a new and non-invasive cardiac imaging technique. The last generation of MSCT scanners show a better imaging quality, due to a greater spatial and temporal resolution. Four expert observers (two cardiologists and two radiologists) have compared the angiographic data with the accuracy of the 64-MSCT in the detection and evaluation of coronary vessels stenoses. From the data obtained, the sensibility, the specificity and the accuracy of the coronary 64-MSCT have been defined. We have enrolled 75 patients (57 male, 18 female, mean age 61.83 +/- 10.38; range 30-80 years) with known or suspected coronary artery disease. The above population has been divided into 3 groups: Group A (Gr. A) with 40 patients (mean age 60.7 +/- 12.5) affected by both non-significant and significant coronary artery disease; Group B (Gr. B) with 25 patients (mean age 60.3 +/- 14.6) who underwent to percutaneous coronary intervention (PCI); Group C (Gr. C) with 10 patients (mean age 54.20 +/- 13.7) without any coronary angiographic stenoses. All the patients underwent non-invasive exams, conventional coronary angiography and coronary 64-MSCT. The comparison of the data obtained has been carried out according to a per group analysis, per patient analysis and per segment analysis. Moreover, the accuracy of the 64-MSCT has been defined for the detection of >75%, 50-75% and <50% coronary stenoses. Coronary angiography has identified significant coronary artery disease in 75% of the patients in the Gr. A and in 73% of the patients in the Gr. B. No coronary stenoses have been detected in Gr. C. According to a per segment analysis, in Gr. A, 36% of the segments analysed have shown a coronary stenosis (37% stenoses >75%, 32% stenoses 50-75% and 31% stenoses <50%). In Gr. B, 32% of the segments have shown a coronary stenosis (33% stenoses >75%, 29% stenoses 50-75% and 38% stenoses <50%). In-stent disease has been shown in only 4 of the 29 coronary stents identified. In Gr. A, coronary 64-MSCT has confirmed the angiographic results in the 93% of cases (sensibility 93%, specificity 100%, positive predictive value 100% and negative predictive value 83%) while, in Gr. B, this confirm has been obtained only in 64% of cases (sensibility 64%, specificity 100%, positive predictive value 100% and negative predictive value 50%). In Gr. C, we have observed a complete agreement between angiographic and CT data (sensibility, specificity, positive predictive value and negative predictive value 100%). According to a per segment analysis, the angiographic results have been confirmed in 98% of cases in Gr. A (sensibility 98%, specificity 94%, positive predictive value 90% and negative predictive value 94%) but only in 55% of cases in Gr. B (sensibility 55%, specificity 90%, positive predictive value 71% and negative predictive value 81%). Moreover, only 1 of the 4 in-stent restenoses has been detected (sensibility 25%, specificity 100%, positive predictive value 100% and negative predictive value 77%). Coronary angiography has detected a greater number of coronary stenoses than the 64-MSCT. 64-MSCT has demonstrated better accuracy in the study of coronary vessels wider than 2 mm, while its accuracy is lower for smaller vessels (diameter < 2.5 mm) and for the identification of in-stent restenosis, because there is a reduced image quality for these vessels and therefore a lower accuracy in the coronary stenosis detection. Nevertheless, 64-MSCT shows high accuracy and it can be considered a comparative but not a substitutive exam of the coronary angiography. Several technical limitations of the 64-MSCT are responsible of its lower accuracy versus the conventional coronary angiography, but solving these technical problems could give us a new non-invasive imaging technique for the study of coronary stents. PMID:1967316

Alessandri, N; Di Matteo, A; Rondoni, G; Petrassi, M; Tufani, F; Ferrari, R; Laghi, A

2009-01-01

191

Limitations to adaptive optics image quality in rodent eyes  

PubMed Central

Adaptive optics (AO) retinal image quality of rodent eyes is inferior to that of human eyes, despite the promise of greater numerical aperture. This paradox challenges several assumptions commonly made in AO imaging, assumptions which may be invalidated by the very high power and dioptric thickness of the rodent retina. We used optical modeling to compare the performance of rat and human eyes under conditions that tested the validity of these assumptions. Results showed that AO image quality in the human eye is robust to positioning errors of the AO corrector and to differences in imaging depth and wavelength compared to the wavefront beacon. In contrast, image quality in the rat eye declines sharply with each of these manipulations, especially when imaging off-axis. However, some latitude does exist to offset these manipulations against each other to produce good image quality. PMID:22876346

Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

2012-01-01

192

Anatomy-based image processing analysis of the running pattern of the perioral artery for minimally invasive surgery.  

PubMed

We aimed to elucidate the tortuous course of the perioral artery with the aid of image processing, and to suggest accurate reference points for minimally invasive surgery. We used 59 hemifaces from 19 Korean and 20 Thai cadavers. A perioral line was defined to connect the point at which the facial artery emerged on the mandibular margin, and the ramification point of the lateral nasal artery and the inferior alar branch. The course of the perioral artery was reproduced as a graph based on the perioral line and analysed by adding the image of the artery using MATLAB. The course of the artery could be classified into 2 according to the course of the alar branch - oblique and vertical. Two distinct inflection points appeared in the course of the artery along the perioral line at the ramification points of the alar branch and the inferior labial artery, respectively, and the course of the artery across the face can be predicted based on the following references: the perioral line, the ramification point of the alar branch (5?10 mm medial to the perioral line at the level of the lower third of the upper lip) and the inferior labial artery (5?10 mm medial to the perioral line at the level of the middle of the lower lip). PMID:25081954

Lee, Sang-Hee; Lee, Minho; Kim, Hee-Jin

2014-10-01

193

Determination of lung segments in computed tomography images using the Euclidean distance to the pulmonary artery  

SciTech Connect

Purpose: Computed tomography (CT) imaging is the modality of choice for lung cancer diagnostics. With the increasing number of lung interventions on sublobar level in recent years, determining and visualizing pulmonary segments in CT images and, in oncological cases, reliable segment-related information about the location of tumors has become increasingly desirable. Computer-assisted identification of lung segments in CT images is subject of this work.Methods: The authors present a new interactive approach for the segmentation of lung segments that uses the Euclidean distance of each point in the lung to the segmental branches of the pulmonary artery. The aim is to analyze the potential of the method. Detailed manual pulmonary artery segmentations are used to achieve the best possible segment approximation results. A detailed description of the method and its evaluation on 11 CT scans from clinical routine are given.Results: An accuracy of 2–3 mm is measured for the segment boundaries computed by the pulmonary artery-based method. On average, maximum deviations of 8 mm are observed. 135 intersegmental pulmonary veins detected in the 11 test CT scans serve as reference data. Furthermore, a comparison of the presented pulmonary artery-based approach to a similar approach that uses the Euclidean distance to the segmental branches of the bronchial tree is presented. It shows a significantly higher accuracy for the pulmonary artery-based approach in lung regions at least 30 mm distal to the lung hilum.Conclusions: A pulmonary artery-based determination of lung segments in CT images is promising. In the tests, the pulmonary artery-based determination has been shown to be superior to the bronchial tree-based determination. The suitability of the segment approximation method for application in the planning of segment resections in clinical practice has already been verified in experimental cases. However, automation of the method accompanied by an evaluation on a larger number of test cases is required before application in the daily clinical routine.

Stoecker, Christina; Moltz, Jan H.; Lassen, Bianca; Kuhnigk, Jan-Martin; Krass, Stefan [Fraunhofer MEVIS, Institute for Medical Image Computing, Universitaetsallee 29, 28359 Bremen (Germany)] [Fraunhofer MEVIS, Institute for Medical Image Computing, Universitaetsallee 29, 28359 Bremen (Germany); Welter, Stefan [Ruhrlandklinik, Department of Thoracic Surgery, Tueschener Weg 40, 45239 Essen (Germany)] [Ruhrlandklinik, Department of Thoracic Surgery, Tueschener Weg 40, 45239 Essen (Germany); Peitgen, Heinz-Otto [Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)] [Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)

2013-09-15

194

Image Quality Measures for Predicting Automatic Target Recognition Performance  

Microsoft Academic Search

One important issue for Automatic Target Recognition (ATR) systems is to learn how robust the performance is under different scenarios. The quality of the input image sequence is a major factor affecting the ATR algorithm's ability to detect and recognize an object. If one can correlate the algorithm performance with different image quality measures, the recognition confidence can be predicted

Yin Chen; G. Chen; R. S. Blum; E. Blasch; R. S. Lynch

2008-01-01

195

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

196

Image quality evaluation method based on structural similarity  

Microsoft Academic Search

Aiming at solving the limit of current distortion sensitivity analysis(HVS is a complicated non-linear system, while the vision models current are linear and simple), we research a new image quality evaluation method based on structural similarity, that is, to get a general similarity from luminance, contrast and image construction, as an objective quality evaluation criteria. In this way, the method

Li Zhu; Guoyou Wang; Ying Liu

2007-01-01

197

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

198

Analyzing and improving image quality in reflective ghost imaging  

E-print Network

Ghost imaging is a transverse imaging technique that relies on the correlation between a pair of light fields, one that has interacted with the object to be imaged and one that has not. Most ghost imaging experiments have ...

Hardy, Nicholas D. (Nicholas David)

2011-01-01

199

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

200

Quantitative image quality evaluation of an order-statistic filter in x-ray fluoroscopic imaging  

Microsoft Academic Search

The use of x-ray fluoroscopy in complex interventional procedures can result in high patient dose leading to severe skin injuries. Simply reducing exposure degrades image quality. One solution is to acquire images at reduced exposures and digitally filter to reduce noise and restore image quality. We quantitatively evaluated image quality improvement from a bi-directional multi-stage (BMS) median spatio-temporal filter. Improvements

David L. Wilson; Yogesh Srinivas; Francisco J. Sanchez-Marin; Kadri N. Jabri

2000-01-01

201

Noncontrast MR Angiography of the Hand: Improved Arterial Conspicuity by Multi-Directional Flow-Sensitive Dephasing Magnetization Preparation in 3D Balanced SSFP Imaging  

PubMed Central

Purpose To develop a flow-sensitive dephasing (FSD) preparative scheme to facilitate multi-directional flow signal suppression in three-dimensional balanced steady-state free precession (SSFP) imaging and to validate the feasibility of the refined sequence for noncontrast MR angiography (NC-MRA) of the hand. Materials and Methods A new FSD preparative scheme was developed that combines two conventional FSD modules. Studies using a flow phantom (gadolinium doped water 15 cm/sec) and the hands of 11 healthy volunteers (6 males and 5 females) were performed to compare the proposed FSD scheme with its conventional counterpart with respect to the signal suppression of multi-directional flow. In 9 of the 11 healthy subjects and 2 patients with suspected vasculitis and documented Raynaud’s phenomenon, respectively, balanced SSFP imaging coupled with the new FSD scheme was compared with spatial-resolution-matched (0.94 × 0.94 × 0.94 mm3) contrast-enhanced (CE) MRA (0.15 mmol/kg gadopentetate dimeglumine) in terms of overall image quality, venous contamination, motion degradation, and arterial conspicuity. Results The proposed FSD scheme was able to suppress two-dimensional flow signal in the flow phantom and hands and yielded significantly higher arterial conspicuity scores than the conventional scheme did on NC-MRA at the regions of common digitals and proper digitals. Compared with CE-MRA, the refined NC-MRA technique yielded comparable overall image quality and motion degradation, significantly less venous contamination, and significantly higher arterial conspicuity score at digital arteries. Conclusion The FSD-based NC-MRA technique is improved in the depiction of multi-directional flow by applying a two-module FSD preparation, which enhances its potential to serve as an alternative MR angiography technique for the assessment of hand vascular abnormalities. PMID:21487301

Fan, Zhaoyang; Hodnett, Philip A.; Davarpanah, Amir H.; Scanlon, Timothy G.; Sheehan, John J.; Varga, John; Carr, James C.; Li, Debiao

2011-01-01

202

Image processing system performance prediction and product quality evaluation  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. A new technique for image processing system performance prediction and product quality evaluation was developed. It was entirely objective, quantitative, and general, and should prove useful in system design and quality control. The technique and its application to determination of quality control procedures for the Earth Resources Technology Satellite NASA Data Processing Facility are described.

Stein, E. K.; Hammill, H. B. (principal investigators)

1976-01-01

203

Quaternion structural similarity: a new quality index for color images.  

PubMed

One of the most important issues for researchers developing image processing algorithms is image quality. Methodical quality evaluation, by showing images to several human observers, is slow, expensive, and highly subjective. On the other hand, a visual quality matrix (VQM) is a fast, cheap, and objective tool for evaluating image quality. Although most VQMs are good in predicting the quality of an image degraded by a single degradation, they poorly perform for a combination of two degradations. An example for such degradation is the color crosstalk (CTK) effect, which introduces blur with desaturation. CTK is expected to become a bigger issue in image quality as the industry moves toward smaller sensors. In this paper, we will develop a VQM that will be able to better evaluate the quality of an image degraded by a combined blur/desaturation degradation and perform as well as other VQMs on single degradations such as blur, compression, and noise. We show why standard scalar techniques are insufficient to measure a combined blur/desaturation degradation and explain why a vectorial approach is better suited. We introduce quaternion image processing (QIP), which is a true vectorial approach and has many uses in the fields of physics and engineering. Our new VQM is a vectorial expansion of structure similarity using QIP, which gave it its name-Quaternion Structural SIMilarity (QSSIM). We built a new database of a combined blur/desaturation degradation and conducted a quality survey with human subjects. An extensive comparison between QSSIM and other VQMs on several image quality databases-including our new database-shows the superiority of this new approach in predicting visual quality of color images. PMID:22203713

Kolaman, Amir; Yadid-Pecht, Orly

2012-04-01

204

High quality underwater imaging platform with laser range gated technique combining with image denoising and restoration  

NASA Astrophysics Data System (ADS)

Underwater laser imaging is of great significance in underwater search and marine science, etc. However, traditional underwater laser imaging is often of poor quality with noises and blurs, moreover, the resolution of the image is also low. In order to obtain clear underwater images with high resolution and quality, here, we have designed a range gated imaging underwater imaging system and realized an image restoration approach. In this paper, based on the introduction to the imaging system and image restoration algorithm, the experiment is established by setting the imaging system under water in the lake to capture the underwater targets. With the proposed underwater image restoration approach, images of high quality could be retrieved which proves that the method is able to identify the target ~10 meters away underwater.

Huang, Huachuan; Wang, Rongbo; Yan, Keding; Yan, Zhengang; Wang, Shouyu; Li, Zhenhua; Li, Zeren

2014-10-01

205

Carotid Artery Segmentation in Ultrasound Images and Measurement of Intima-Media Thickness  

PubMed Central

Background. The segmentation of the common carotid artery (CCA) wall is imperative for the determination of the intima-media thickness (IMT) on B-mode ultrasound (US) images. The IMT is considered an important indicator in the evaluation of the risk for the development of atherosclerosis. In this paper, authors have discussed the relevance of measurements in clinical practices and the challenges that one has to face while approaching the segmentation of carotid artery on ultrasound images. The paper presents an overall review of commonly used methods for the CCA segmentation and IMT measurement along with the different performance metrics that have been proposed and used for performance validation. Summary and future directions are given in the conclusion. PMID:23865066

Gamad, R. S.; Bansod, P. P.

2013-01-01

206

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

207

SPY: an innovative intra-operative imaging system to evaluate graft patency during off-pump coronary artery bypass grafting.  

PubMed

Off-pump coronary artery bypass grafting (CABG) has been rapidly increased, because of its less invasiveness with low complications. However, graft patency rate highly depends on the operators' capability due to technical difficulties. The SPY system, based on the fluorescence of indocyanine green, is an innovative device that permits validation of graft patency intra-operatively. Real time images of grafts are obtained with no need for catheterization, X-rays or iodine contrast medium. High-quality images could be obtained in all 290 grafts of 72 off-pump CABG cases (mean 4.0 grafts per patient). Four anastomoses (1.4%), including two proximal and two distal, were revised because of defects detected by SPY images. In one case, the SPY system revealed no blood flow in a radial sequential graft, although transit-time flow meter measurements showed a diastolic dominant pattern. SPY images provide critical information to surgeons to detect non-patent grafts, allowing them to be revised while the patient is still on the operating table. Using the SPY system, technical failures could be completely resolved during surgery. The use of the SPY system for intra-operative graft validation during off-pump CABG may become the gold standard for surgical management in the near future. PMID:17670291

Takahashi, Masao; Ishikawa, Toshihiro; Higashidani, Koichi; Katoh, Hiroki

2004-09-01

208

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

209

An Image Quality Evaluation Method Based on Digital Watermarking  

Microsoft Academic Search

As a practical and novel application of watermarking, this paper presents a digital watermarking-based image quality evaluation method that can accurately estimate image quality in terms of the classical objective metrics, such as peak signal-to-noise ratio (PSNR), weighted PSNR (wPSNR), and Watson just noticeable difference (JND), without the need for the original image. In this method, a watermark is embedded

Sha Wang; Dong Zheng; Jiying Zhao; Wa James Tam; Filippo Speranza

2007-01-01

210

An Approach of Image Fusion Based on General Image Quality Evaluation  

Microsoft Academic Search

The paper introduces a new and simple method of multi-sensor image fusion which is based on an image fusion quality evaluation index with subjectivity and objectivity combined the application of wavelet transform in image fusion, a new image fusion strategy based on pixel level is used, it overcomes the disadvantage of losing easily image details of simple fusion method. The

Tian Ya-fei; Qin Yun-xia; Yang Jia-yuan; Guo Ai-ping

2009-01-01

211

Quantitative images quality evaluation of digital medical imaging systems using mutual information  

Microsoft Academic Search

Information about image quality of medical images is important for imaging system assessment in order to promote the development and manufacturing of state-of-the-art imaging systems. In this paper, we present a method for evaluating physical performance of digital medical imaging systems using mutual information which is a concept from information theory. To validate the proposed method, computer simulations were performed,

Du-Yih Tsai; Eri Matsuyama; Yongbum Lee

2011-01-01

212

Effect of image quality on calcification detection in digital mammography  

SciTech Connect

Purpose: This study aims to investigate if microcalcification detection varies significantly when mammographic images are acquired using different image qualities, including: different detectors, dose levels, and different image processing algorithms. An additional aim was to determine how the standard European method of measuring image quality using threshold gold thickness measured with a CDMAM phantom and the associated limits in current EU guidelines relate to calcification detection. Methods: One hundred and sixty two normal breast images were acquired on an amorphous selenium direct digital (DR) system. Microcalcification clusters extracted from magnified images of slices of mastectomies were electronically inserted into half of the images. The calcification clusters had a subtle appearance. All images were adjusted using a validated mathematical method to simulate the appearance of images from a computed radiography (CR) imaging system at the same dose, from both systems at half this dose, and from the DR system at quarter this dose. The original 162 images were processed with both Hologic and Agfa (Musica-2) image processing. All other image qualities were processed with Agfa (Musica-2) image processing only. Seven experienced observers marked and rated any identified suspicious regions. Free response operating characteristic (FROC) and ROC analyses were performed on the data. The lesion sensitivity at a nonlesion localization fraction (NLF) of 0.1 was also calculated. Images of the CDMAM mammographic test phantom were acquired using the automatic setting on the DR system. These images were modified to the additional image qualities used in the observer study. The images were analyzed using automated software. In order to assess the relationship between threshold gold thickness and calcification detection a power law was fitted to the data. Results: There was a significant reduction in calcification detection using CR compared with DR: the alternative FROC (AFROC) area decreased from 0.84 to 0.63 and the ROC area decreased from 0.91 to 0.79 (p < 0.0001). This corresponded to a 30% drop in lesion sensitivity at a NLF equal to 0.1. Detection was also sensitive to the dose used. There was no significant difference in detection between the two image processing algorithms used (p > 0.05). It was additionally found that lower threshold gold thickness from CDMAM analysis implied better cluster detection. The measured threshold gold thickness passed the acceptable limit set in the EU standards for all image qualities except half dose CR. However, calcification detection varied significantly between image qualities. This suggests that the current EU guidelines may need revising. Conclusions: Microcalcification detection was found to be sensitive to detector and dose used. Standard measurements of image quality were a good predictor of microcalcification cluster detection.

Warren, Lucy M.; Mackenzie, Alistair; Cooke, Julie; Given-Wilson, Rosalind M.; Wallis, Matthew G.; Chakraborty, Dev P.; Dance, David R.; Bosmans, Hilde; Young, Kenneth C. [National Co-ordinating Centre for the Physics of Mammography, Royal Surrey County Hospital NHS Foundation Trust, Guildford GU2 7XX, United Kingdom and Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH (United Kingdom); Jarvis Breast Screening and Diagnostic Centre, Guildford GU1 1LJ (United Kingdom); Department of Radiology, St. George's Healthcare NHS Trust, Tooting, London SW17 0QT (United Kingdom); Cambridge Breast Unit, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, United Kingdom and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0QQ (United Kingdom); Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15210 (United States); National Co-ordinating Centre for the Physics of Mammography, Royal Surrey County Hospital NHS Foundation Trust, Guildford GU2 7XX, United Kingdom and Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH (United Kingdom); University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium); National Co-ordinating Centre for the Physics of Mammography, Royal Surrey County Hospital NHS Foundation Trust, Guildford GU2 7XX, United Kingdom and Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH (United Kingdom)

2012-06-15

213

Effect of image quality on calcification detection in digital mammography  

PubMed Central

Purpose: This study aims to investigate if microcalcification detection varies significantly when mammographic images are acquired using different image qualities, including: different detectors, dose levels, and different image processing algorithms. An additional aim was to determine how the standard European method of measuring image quality using threshold gold thickness measured with a CDMAM phantom and the associated limits in current EU guidelines relate to calcification detection. Methods: One hundred and sixty two normal breast images were acquired on an amorphous selenium direct digital (DR) system. Microcalcification clusters extracted from magnified images of slices of mastectomies were electronically inserted into half of the images. The calcification clusters had a subtle appearance. All images were adjusted using a validated mathematical method to simulate the appearance of images from a computed radiography (CR) imaging system at the same dose, from both systems at half this dose, and from the DR system at quarter this dose. The original 162 images were processed with both Hologic and Agfa (Musica-2) image processing. All other image qualities were processed with Agfa (Musica-2) image processing only. Seven experienced observers marked and rated any identified suspicious regions. Free response operating characteristic (FROC) and ROC analyses were performed on the data. The lesion sensitivity at a nonlesion localization fraction (NLF) of 0.1 was also calculated. Images of the CDMAM mammographic test phantom were acquired using the automatic setting on the DR system. These images were modified to the additional image qualities used in the observer study. The images were analyzed using automated software. In order to assess the relationship between threshold gold thickness and calcification detection a power law was fitted to the data. Results: There was a significant reduction in calcification detection using CR compared with DR: the alternative FROC (AFROC) area decreased from 0.84 to 0.63 and the ROC area decreased from 0.91 to 0.79 (p?image processing algorithms used (p?>?0.05). It was additionally found that lower threshold gold thickness from CDMAM analysis implied better cluster detection. The measured threshold gold thickness passed the acceptable limit set in the EU standards for all image qualities except half dose CR. However, calcification detection varied significantly between image qualities. This suggests that the current EU guidelines may need revising. Conclusions: Microcalcification detection was found to be sensitive to detector and dose used. Standard measurements of image quality were a good predictor of microcalcification cluster detection. PMID:22755704

Warren, Lucy M.; Mackenzie, Alistair; Cooke, Julie; Given-Wilson, Rosalind M.; Wallis, Matthew G.; Chakraborty, Dev P.; Dance, David R.; Bosmans, Hilde; Young, Kenneth C.

2012-01-01

214

Analysis of the Quality of Information Obtained About Uterine Artery Embolization From the Internet  

SciTech Connect

Purpose: The Internet is widely used by patients to source health care-related information. We sought to analyse the quality of information available on the Internet about uterine artery embolization (UAE). Materials and Methods: We searched three major search engines for the phrase 'uterine artery embolization' and compiled the top 50 results from each engine. After excluding repeated sites, scientific articles, and links to documents, the remaining 50 sites were assessed using the LIDA instrument, which scores sites across the domains of accessibility, usability, and reliability. The Fleisch reading ease score (FRES) was calculated for each of the sites. Finally, we checked the country of origin and the presence of certification by the Health On the Net Foundation (HONcode) as well as their effect on LIDA and FRES scores.ResultsThe following mean scores were obtained: accessibility 48/60 (80%), usability 42/54 (77%), reliability 20/51 (39%), total LIDA 110/165 (67%), and FRES 42/100 (42%). Nine sites had HONcode certification, and this was associated with significantly greater (p < 0.05) reliability and total LIDA and FRES scores. When comparing sites between United Kingdom and United States, there was marked variation in the quality of results obtained when searching for information on UAE (p < 0.05). Conclusion: In general, sites were well designed and easy to use. However, many scored poorly on the reliability of their information either because they were produced in a non-evidence-based way or because they lacking currency. It is important that patients are guided to reputable, location-specific sources of information online, especially because prominent search engine rank does not guarantee reliability of information.

Tavare, Aniket N. [British Medical Association House, British Medical Journal Group (United Kingdom); Alsafi, Ali, E-mail: ali.alsafi03@imperial.ac.uk; Hamady, Mohamad S. [St. Mary's Hospital, Imaging Department (United Kingdom)

2012-12-15

215

A perceptual image quality evaluation based on local spatial information  

Microsoft Academic Search

This paper presents a new comparative objective method for image quality evaluation. This method relies on two keys points: a local objective evaluation and a perceptual gathering. The local evaluation concerns the dissimilarities between the degraded image and the reference image ; it is based on a gray- level local Hausdorff distance. This new Hausdorff distance uses a generalized distance

N. Girard; E. Baudrier

2009-01-01

216

Effects of exercise training program on functional capacity and quality of life in patients with peripheral arterial occlusive disease  

Microsoft Academic Search

Summary Background: In patients with peripheral arterial oc- clusive disease (PAOD) stage II, exercise training seems to be important to reduce symptoms and improve functional capacity. We evaluated the effects of an out- patient treatment program on walking distance (stan- dardized treadmill testing), training exercise capacity, and disease specific quality of life (PAVK-86 question- naire). Methods and results: Thirty-one patients

Ch. Gartenmann; I. Kirchberger; M. Herzig; I. Baumgartner; H. Saner; F. Mahler; K. Meyer

2002-01-01

217

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

218

Effects of nebivolol on the central hemodynamic, platelet aggregation and life’s quality in patients with arterial hypertension  

Microsoft Academic Search

Object of this investigation is study of Nebivolol's influence on parameters of Central Hemodynamic, platelet aggregation and life's quality in patients with Arterial Hypertension (AH). 32 patients (men) aged 30-65 years with mild and moderate AH were examined. Nebivolol was administrated in dosage of 5 mg one time daily as the 6 monthly monotherapy.We carried out the dynamic control of

Mardona D. Rakhmatullaeva; Shirin R. Ibabekova; Nargiza I. Azimova

2002-01-01

219

Identification of suitable fundus images using automated quality assessment methods.  

PubMed

Retinal image quality assessment (IQA) is a crucial process for automated retinal image analysis systems to obtain an accurate and successful diagnosis of retinal diseases. Consequently, the first step in a good retinal image analysis system is measuring the quality of the input image. We present an approach for finding medically suitable retinal images for retinal diagnosis. We used a three-class grading system that consists of good, bad, and outlier classes. We created a retinal image quality dataset with a total of 216 consecutive images called the Diabetic Retinopathy Image Database. We identified the suitable images within the good images for automatic retinal image analysis systems using a novel method. Subsequently, we evaluated our retinal image suitability approach using the Digital Retinal Images for Vessel Extraction and Standard Diabetic Retinopathy Database Calibration level 1 public datasets. The results were measured through the F1 metric, which is a harmonic mean of precision and recall metrics. The highest F1 scores of the IQA tests were 99.60%, 96.50%, and 85.00% for good, bad, and outlier classes, respectively. Additionally, the accuracy of our suitable image detection approach was 98.08%. Our approach can be integrated into any automatic retinal analysis system with sufficient performance scores. PMID:24718384

?evik, U?ur; Köse, Cemal; Berber, Tolga; Erdöl, Hidayet

2014-04-01

220

Determination of culprit coronary artery branches using hemodynamic indices from angiographic images.  

PubMed

A recently reported angiographic technique for hemodynamic indices based on first-pass distribution analysis (FPA) could potentially be helpful for determining the culprit artery responsible for myocardial ischemia. The purpose of this study was to determinate the culprit coronary arterial branches based on coronary flow reserve (CFR) and fractional flow reserve (FFR) using only angiographic images. The study was performed in 14 anesthetized swine. Microspheres were injected into coronary arterial branches to create microvascular disruption. Stenosis was also created by inserting plastic tubings in LAD and LCX arterial branches. Adenosine was used to produce maximum hyperemia. Angiographic CFR (CFRa), relative angiographic CFR (rCFRa), and angiographic FFR (FFRa) were calculated by FPA. The diagnostic abilities of CFRa, rCFRa, and FFRa were compared in three models: (1) epicardial stenosis model (S), (2) microcirculation disruption model (M), and (3) combined(S + M) model by using the area under the ROC curve (AUC). The mean differences between FFRa and the pressure-derived FFR (FFRp) measurements were -0.01 ± 0.21 in S model (N = 37) and 0.01 ± 0.18 in M model (N = 53). From 225 measurements in S model, the AUCs for CFRa and FFRa were 0.720 and 0.918, respectively. From 262 measurements in M model and 238 measurements in (S + M) model, the AUCs for CFRa, rCFRa, FFRa were 0.744, 0.715, 0.959 and 0.806, 0.738, 0.995, respectively. The hemodynamic indices of the small branches (down to ~0.7 mm) could be measured using only angiographic image data. The application of FFRa could potentially provide a useful method to assess the severity of disease in coronary arterial branches. PMID:25288357

Zhang, Zhang; Chen, Jun; Takarada, Shigeho; Molloi, Sabee

2015-01-01

221

Image quality and dose efficiency of high energy phase sensitive x-ray imaging: Phantom studies  

PubMed Central

The goal of this preliminary study was to perform an image quality comparison of high energy phase sensitive imaging with low energy conventional imaging at similar radiation doses. The comparison was performed with the following phantoms: American College of Radiology (ACR), contrast-detail (CD), acrylic edge and tissue-equivalent. Visual comparison of the phantom images indicated comparable or improved image quality for all phantoms. Quantitative comparisons were performed through ACR and CD observer studies, both of which indicated higher image quality in the high energy phase sensitive images. The results of this study demonstrate the ability of high energy phase sensitive imaging to overcome existing challenges with the clinical implementation of phase contrast imaging and improve the image quality for a similar radiation dose as compared to conventional imaging near typical mammography energies. In addition, the results illustrate the capability of phase sensitive imaging to sustain the image quality improvement at high x-ray energies and for – breast – simulating phantoms, both of which indicate the potential to benefit fields such as mammography. Future studies will continue to investigate the potential for dose reduction and image quality improvement provided by high energy phase sensitive contrast imaging. PMID:24865208

Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

2014-01-01

222

Study on the improvement of overall optical image quality via digital image processing  

NASA Astrophysics Data System (ADS)

This paper studies the effects of improving overall optical image quality via Digital Image Processing (DIP) and compares the promoted optical image with the non-processed optical image. Seen from the optical system, the improvement of image quality has a great influence on chromatic aberration and monochromatic aberration. However, overall image capture systems-such as cellphones and digital cameras-include not only the basic optical system but also many other factors, such as the electronic circuit system, transducer system, and so forth, whose quality can directly affect the image quality of the whole picture. Therefore, in this thesis Digital Image Processing technology is utilized to improve the overall image. It is shown via experiments that system modulation transfer function (MTF) based on the proposed DIP technology and applied to a comparatively bad optical system can be comparable to, even possibly superior to, the system MTF derived from a good optical system.

Tsai, Cheng-Mu; Fang, Yi Chin; Lin, Yu Chin

2008-12-01

223

Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality.  

PubMed

The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 microGy/frame (cine) and 5 and 95 mGy min(-1) (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality. PMID:16306664

Vano, E; Geiger, B; Schreiner, A; Back, C; Beissel, J

2005-12-01

224

Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality  

NASA Astrophysics Data System (ADS)

The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 µGy/frame (cine) and 5 and 95 mGy min-1 (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

Vano, E.; Geiger, B.; Schreiner, A.; Back, C.; Beissel, J.

2005-12-01

225

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

226

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

PubMed Central

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.

2013-01-01

227

Cardiovascular magnetic resonance imaging as applied to patients with pulmonary arterial hypertension.  

PubMed

Numerous imaging techniques are currently used to evaluate pulmonary arterial hypertension (PAH), including echocardiography, x-ray, electrocardiogram (ECG), computed tomography and magnetic resonance imaging (MRI). All such modalities have inherent advantages and disadvantages governed by physical principles that result in their clinical utility. In that PAH is a progressive disorder characterised by abnormally elevated blood pressure of the pulmonary circulation that leads to extensive vascular remodelling and increased pulmonary vascular resistance, a technique that can encapsulate those specific features that depict the multiple facets of this disease has obvious advantages. Recent advances in cardiovascular MRI (CMR) technology have led to the development of dedicated techniques for non-invasive assessment of cardiovascular structure and function, including haemodynamical parameters in the pulmonary circulation, which are superior in their identification of pulmonary arterial right ventricular morphological changes. These advantages make CMR a very attractive modality for diagnosing, following and providing prognoses for PAH patients. In this review, we highlight the developments in the use of CMR for the diagnosis, assessment and monitoring of patients with PAH. These remarkable improvements in image acquisition, physiological imaging and contrast techniques place CMR in a prime position for defining this disease. In the coming decade, it is anticipated that continued improvements in CMR image acquisition, spatial and temporal resolution and analytical techniques will result in improved understanding of PAH pathophysiology, diagnosis and prognostic variables, as well as the replacement of the most, if not all, invasive procedures currently applied routinely to the evaluation of PAH. PMID:19624797

Biederman, R W W

2009-09-01

228

Prevalence of calcified carotid artery atheromas on panoramic images of individuals with primary hyperparathyroidism  

PubMed Central

Objectives: Primary hyperparathyroidism (PHPT), affecting 1% of the population, is associated with increased cardiovascular morbidity and mortality. The presence of calcified carotid artery plaque (CCAP) on panoramic images is a validated risk indicator of future adverse cardiovascular events. We hypothesized that military veterans aged 50 years or older diagnosed with PHPT by increased parathyroid hormone and calcium levels would frequently have CCAP on their images. Methods: We determined the prevalence rates of CCAP on the images of patients diagnosed with PHPT and evaluated their atherogenic risk profiles, including hypertension, dyslipidaemia, diabetes and obesity. Comparisons of atherogenic risk factors were made between subjects with and without observed CCAP on their panoramic images. Results: Of the 60 patients (86.7% males and 13.3% females, mean age 73.2 ± 11.3 years) with PHPT, 40% had atheromas. There were no significant differences between CCAP+ and CCAP? groups in gender or race (p > 0.05). The atherogenic profile (age, body mass index, hypertension, diabetes, hyperlipidaemia) in the CCAP+ and CCAP? groups was not significantly different (p > 0.05). Conclusions: Calcified carotid artery atheromas are often seen on the panoramic images of patients with PHPT. Thus, dentists must be uniquely vigilant for these lesions when evaluating these studies. PMID:23775925

Friedlander, A H; Aghazadehsanai, N; Chang, T I; Harada, N; Garrett, N R

2013-01-01

229

Imaging of post-mortem coronary arteries by 30 MHz intravascular ultrasound.  

PubMed

Intravascular ultrasound cross-sectional imaging of the atherosclerotic artery may be employed to guide plaque ablation by spark erosion, atherectomy, laser irradiation or other means. To assess whether in the coronary artery the echolucent zone of the three-layered ultrasound appearance of muscular arteries might be a reliable boundary to halt transluminal ablative angioplasty, epicardial coronary arteries were scanned under pressure over a distance of 4-8 cm at 1 mm intervals. A 5.2F catheter with a 30 MHz transducer rotating at 600 RPM was used. In 419 images from four post-mortem hearts, aged at death 22, 31, 56 and 82 years, the presence of a distinct echolucent zone was scored as percentage of the wall circumference. The median scores were 0%, 0%, 10% and 75%, respectively. In the three youngest hearts, the three-layered appearance was largely absent. In the 82 year old heart, in contrast, the three-layered appearance could generally be identified. Within subjects, the presence of an echolucent zone was variable in location. Qualitatively, neither abundant medial elastin tissue nor a reduced medial thickness could explain the absence of an echolucent zone when the ultrasound image was compared to the corresponding microscopic section. The results show that in the 82 year old heart, 30 MHz intravascular ultrasound discrimination of coronary wall layers would be adequate to guide transluminal plaque ablation. In the younger hearts, guided ablation would fail due to the limited presence of a distinct echolucent zone as an ultrasound landmark of the media. Whether the presence or absence of an echolucent zone is related to age remains to be determined. PMID:1919066

Borst, C; Savalle, L H; Smits, P C; Post, M J; Gussenhoven, W J; Bom, N

1991-01-01

230

Comparison of the astronomical and multimedia image quality criteria  

NASA Astrophysics Data System (ADS)

This paper deals with the criteria definition of image quality in astronomy and their comparison with common multimedia approaches. Astronomical images have typical specific properties - high grayscale bit depth, size, high noise occurrence, sensitivity to point spread function deformation and special processing algorithms. They belong to the class of scientific images as well as medical or similar. Their processing and compression is quite different from the classical approach of multimedia image processing. The new compression algorithm based on JPEG2000 is selected as a distortion source in this paper. Selected image quality criteria (multimedia and optimized for astronomical images) are tested on the set of images from the DEIMOS image database with miscellaneous level of the thermally generated CCD noise. The deformation of the point spread function (PSF) is also measured for chosen compression approach.

Anisimova, Elena; Páta, Petr; Fliegel, Karel; Klíma, Miloš

2012-06-01

231

Objective and subjective image quality evaluation for security technology  

Microsoft Academic Search

The paper is devoted to the impacts of image compression algorithms on security image data. It compares three fundamentally different evaluation techniques of image objective criteria, subjective criteria and identification. We have selected two typical security image data (a car plate and a face) with different initial quality and we applied three different compression techniques-two professional (JPEG and LuRaWave-LWF) and

Milos Klima; Jiri Pazderak; Martin Bernas; Petr Pata; Jiri Hozman; Karel Roubik

2001-01-01

232

Blood Flow Vortices along the Main Pulmonary Artery Measured with MR Imaging for Diagnosis of Pulmonary Hypertension.  

PubMed

Purpose To approximate the functional relationship between invasively measured mean pulmonary arterial pressure ( mPAP mean pulmonary arterial pressure ) and the phase-contrast magnetic resonance (MR) imaging-derived duration of vortical blood flow along the main pulmonary artery and to analyze its applicability for noninvasive diagnosis of pulmonary hypertension ( PH pulmonary hypertension ) and borderline mPAP mean pulmonary arterial pressure . Materials and Methods The local ethics review board approved this prospective study of 145 patients suspected of having PH pulmonary hypertension (69 patients with PH pulmonary hypertension , 19 patients with borderline mPAP mean pulmonary arterial pressure , and 57 patients with normal mPAP mean pulmonary arterial pressure ) who underwent right heart catheterization ( RHC right heart catheterization ) and three-directional phase-contrast MR imaging of the main pulmonary artery. Velocity fields were viewed with dedicated software and evaluated for the duration of vortical blood flow in the main pulmonary artery (tvortex, the percentage of cardiac phases with vortex present). The relationship between mPAP mean pulmonary arterial pressure at RHC right heart catheterization and tvortex was assessed by means of a segmented linear regression model, and by Bland-Altman and receiver operating characteristic curve analyses. Results The relationship between mPAP mean pulmonary arterial pressure and tvortex was described adequately (R(2) = 0.95) as linearly increasing, from tvortex of 0% ( mPAP mean pulmonary arterial pressure ? 16.0 mm Hg) with a slope of 1.59% per millimeter of mercury. The standard deviation between mPAP mean pulmonary arterial pressure values derived from RHC right heart catheterization and those estimated by using tvortex was 3.9 mm Hg. The area under the curve for tvortex-based diagnosis of PH pulmonary hypertension was 0.994 (95% confidence interval [ CI confidence interval ]: 0.982, 0.998), and the calculated PH pulmonary hypertension cut-off value (tvortex ? 14.3%) resulted in sensitivity of 0.97 (95% CI confidence interval : 0.90, 0.99) and specificity of 0.96 (95% CI confidence interval : 0.89, 0.99). Vortical blood flow with tvortex less than 14.3% was specific for borderline mPAP mean pulmonary arterial pressure . Conclusion Duration of vortical blood flow in the main pulmonary artery that is determined by using phase-contrast MR imaging allows accurate estimation of elevated mPAP mean pulmonary arterial pressure and diagnosis of PH pulmonary hypertension . © RSNA, 2014 Clinical trial registration no. NCT00575692. PMID:25372980

Reiter, Gert; Reiter, Ursula; Kovacs, Gabor; Olschewski, Horst; Fuchsjäger, Michael

2014-11-01

233

Monitoring the quality of life in patients with coronary artery disease.  

PubMed

Monitoring the outcomes of treatment and quantifying patients' functional status have assumed a prominent role in both clinical trials and quality assurance programs. Because patients with coronary artery disease (CAD) may have comorbid illnesses, and because generic health status questionnaires may not focus on symptoms and impairments unique to coronary disease, a generic measure of health status may not be sufficient to detect important changes in patients' CAD. The responsiveness to clinical change of the Seattle Angina Questionnaire (SAQ), a disease-specific measure for CAD, was compared with that of the Short Form-36, a generic measure of health status. Both questionnaires were serially administered, 3 months apart, to 45 patients undergoing coronary angioplasty and to 130 patients with stable CAD. Most scales of both questionnaires improved significantly after coronary angioplasty. The responsiveness statistics of the SAQ exceeded those of the Short Form-36. Among 130 patients with initially stable angina, 33 deteriorated, 79 remained stable, and 18 improved over 3 months of observation. Mean SAQ scores changed significantly and appropriately in each of these groups. In contrast, none of the Short Form-36 scales detected these more subtle changes. Although useful in assessing overall function, a generic health status measure, such as the Short Form-36, may not be responsive enough to detect important clinical changes in patients' CAD. A disease-specific instrument, such as the SAQ, can be an important and relevant outcome measure in clinical trials or quality assurance programs. PMID:7977097

Spertus, J A; Winder, J A; Dewhurst, T A; Deyo, R A; Fihn, S D

1994-12-15

234

Figure of Image Quality and Information Capacity in Digital Mammography  

PubMed Central

Objectives. In this work, a simple technique to assess the image quality characteristics of the postprocessed image is developed and an easy to use figure of image quality (FIQ) is introduced. This FIQ characterizes images in terms of resolution and noise. In addition information capacity, defined within the context of Shannon's information theory, was used as an overall image quality index. Materials and Methods. A digital mammographic image was postprocessed with three digital filters. Resolution and noise were calculated via the Modulation Transfer Function (MTF), the coefficient of variation, and the figure of image quality. In addition, frequency dependent parameters such as the noise power spectrum (NPS) and noise equivalent quanta (NEQ) were estimated and used to assess information capacity. Results. FIQs for the “raw image” data and the image processed with the “sharpen edges” filter were found 907.3 and 1906.1, correspondingly. The information capacity values were 60.86 × 103 and 78.96 × 103?bits/mm2. Conclusion. It was found that, after the application of the postprocessing techniques (even commercial nondedicated software) on the raw digital mammograms, MTF, NPS, and NEQ are improved for medium to high spatial frequencies leading to resolving smaller structures in the final image. PMID:24895593

Michail, Christos M.; Kalyvas, Nektarios E.; Valais, Ioannis G.; Fudos, Ioannis P.; Fountos, George P.; Dimitropoulos, Nikos; Kandarakis, Ioannis S.

2014-01-01

235

Evaluation of exercise electrocardiography and thallium tomographic imaging in detecting asymptomatic coronary artery disease in diabetic patients.  

PubMed Central

Thallium tomographic imaging and exercise electrocardiography were performed on 136 diabetic patients without symptoms of heart disease. Thirty three patients had post-exercise thallium defects and 19 had ST 1 mm greater than or equal to segment depression during exercise electrocardiography. Both tests were positive in 13 patients. Coronary angiography was subsequently performed on 33 patients with either scintigraphic and/or electrocardiographic evidence of myocardial ischaemia. Angiographically significant coronary artery disease (greater than or equal to 50% narrowing of the coronary artery lumen) was detected in 13 patients. Six patients had minimal coronary artery stenosis (less than 50%), and 14 had normal coronary arteries. Six patients refused cardiac catheterisation. In 14 out of 27 patients with post-exercise thallium defects coronary angiography did not show any coronary artery stenoses (positive predictive accuracy 48%). Exercise electrocardiography showed only one false positive result (positive predictive accuracy 94%) but failed to detect coronary artery disease in three patients with a positive scintigraphic result. The accuracy of a positive exercise electrocardiographic test seems to be better than that of a positive thallium tomographic scan for detecting asymptomatic coronary artery disease in diabetic patients. The high number of false positive thallium defects may be the result of technical features inherent in thallium tomography and/or the possible disease of the small intramyocardial arteries in diabetic patients. Images PMID:2310651

Koistinen, M J; Huikuri, H V; Pirttiaho, H; Linnaluoto, M K; Takkunen, J T

1990-01-01

236

Unusual hemodynamic stroke related to an accessory middle cerebral artery: The usefulness of fusion images from three-dimensional angiography  

PubMed Central

Background: Ischemic stroke associated with an anomaly of the middle cerebral artery (MCA) is a rare occurrence. The diagnosis is very difficult when there are steno-occlusive lesions associated with an accessory middle cerebral artery (AMCA). Case Description: A 77-year-old female with hypertension and hyperlipidemia experienced repeated transient ischemic attacks (TIAs) of motor aphasia and dysarthria. Although angiography showed only left intracranial occlusion, the fusion images of three-dimensional digital subtraction angiography (3-D DSA) showed complex steno-occlusive lesions and an AMCA related with the TIA. The cerebral blood flow (CBF) to the left frontal lobe was supplied by the AMCA, via the anterior communicating artery from the right internal carotid artery. The left temporal and parietal lobes were supplied by the stenotic MCA, via the left posterior communicating artery from the left posterior cerebral artery. Single-photon emission computed tomography showed a marked decrease in CBF to both the left frontal and temporal lobes. A left superficial temporal artery (STA)-to-left MCA double anastomosis was performed, in which each branch of the STA supplied branches of the AMCA and MCA. Conclusion: This is the first reported case of ischemic stroke in a patient with an AMCA. The exact diagnosis could be made only by using fusion images of 3-D DSA, which were useful for understanding the complicated CBF pattern and for the choice of recipient artery in bypass surgery. PMID:24778914

Noguchi, Kei; Aoki, Takachika; Komaki, Satoru; Takeuchi, Yasuharu; Hirohata, Masaru; Morioka, Motohiro

2014-01-01

237

Indocyanine green fluorescence and three-dimensional imaging of right gastroepiploic artery in gastric tube cancer.  

PubMed

A 79-year-old male was admitted to our hospital for the treatment of cancer of the gastric tube. Gastrointestinal examination revealed a T1b Union for International Cancer Control (UICC) tumor at the pyloric region of the gastric tube. Laparotomy did not reveal infiltration into the serosa, peritoneal dissemination, regional lymph node swelling, or distant metastasis. We performed a distal gastrectomy preserving the right gastroepiploic artery by referencing the preoperative three-dimensional computed tomoangiography. We also evaluated the blood flow of the right gastroepiploic artery and in the proximal gastric tube by using indocyanine green fluorescence imaging intra-operatively and then followed with a gastrojejunal anastomosis with Roux-en-Y reconstruction. The definitive diagnosis was moderately differentiated adenocarcinoma of the gastric tube, pT1bN0M0, pStage IA (UICC). His postoperative course was uneventful. Three-dimensional computed tomographic imaging is effective for assessing the course of blood vessels and the relationship with the surrounding structures. Intraoperative evaluation of blood flow of the right gastroepiploic artery and of the gastric tube in the anastomotic portion is very valuable information and could contribute to a safe gastrointestinal reconstruction. PMID:25574113

Nakano, Toru; Sakurai, Tadashi; Maruyama, Shota; Ozawa, Yohei; Kamei, Takashi; Miyata, Go; Ohuchi, Noriaki

2015-01-01

238

3D printing of intracranial artery stenosis based on the source images of magnetic resonance angiograph  

PubMed Central

Background and purpose Three dimensional (3D) printing techniques for brain diseases have not been widely studied. We attempted to ‘print’ the segments of intracranial arteries based on magnetic resonance imaging. Methods Three dimensional magnetic resonance angiography (MRA) was performed on two patients with middle cerebral artery (MCA) stenosis. Using scale-adaptive vascular modeling, 3D vascular models were constructed from the MRA source images. The magnified (ten times) regions of interest (ROI) of the stenotic segments were selected and fabricated by a 3D printer with a resolution of 30 µm. A survey to 8 clinicians was performed to evaluate the accuracy of 3D printing results as compared with MRA findings (4 grades, grade 1: consistent with MRA and provide additional visual information; grade 2: consistent with MRA; grade 3: not consistent with MRA; grade 4: not consistent with MRA and provide probable misleading information). If a 3D printing vessel segment was ideally matched to the MRA findings (grade 2 or 1), a successful 3D printing was defined. Results Seven responders marked “grade 1” to 3D printing results, while one marked “grade 4”. Therefore, 87.5% of the clinicians considered the 3D printing were successful. Conclusions Our pilot study confirms the feasibility of using 3D printing technique in the research field of intracranial artery diseases. Further investigations are warranted to optimize this technique and translate it into clinical practice. PMID:25333049

Liu, Jia; Li, Ming-Li; Sun, Zhao-Yong; Chen, Jie

2014-01-01

239

Indocyanine green fluorescence and three-dimensional imaging of right gastroepiploic artery in gastric tube cancer  

PubMed Central

A 79-year-old male was admitted to our hospital for the treatment of cancer of the gastric tube. Gastrointestinal examination revealed a T1b Union for International Cancer Control (UICC) tumor at the pyloric region of the gastric tube. Laparotomy did not reveal infiltration into the serosa, peritoneal dissemination, regional lymph node swelling, or distant metastasis. We performed a distal gastrectomy preserving the right gastroepiploic artery by referencing the preoperative three-dimensional computed tomoangiography. We also evaluated the blood flow of the right gastroepiploic artery and in the proximal gastric tube by using indocyanine green fluorescence imaging intra-operatively and then followed with a gastrojejunal anastomosis with Roux-en-Y reconstruction. The definitive diagnosis was moderately differentiated adenocarcinoma of the gastric tube, pT1bN0M0, pStage IA (UICC). His postoperative course was uneventful. Three-dimensional computed tomographic imaging is effective for assessing the course of blood vessels and the relationship with the surrounding structures. Intraoperative evaluation of blood flow of the right gastroepiploic artery and of the gastric tube in the anastomotic portion is very valuable information and could contribute to a safe gastrointestinal reconstruction. PMID:25574113

Nakano, Toru; Sakurai, Tadashi; Maruyama, Shota; Ozawa, Yohei; Kamei, Takashi; Miyata, Go; Ohuchi, Noriaki

2015-01-01

240

High-quality Reflection Separation using Polarized Images  

E-print Network

Abstract—In this paper, we deal with a problem of separating the effect of reflection from images captured behind glass. The input consists of multiple polarized images captured from the same view point but with different polarizer angles. The output is the high quality separation of the reflection layer and the background layer from the images. We formulate this problem as a constrained optimization problem and propose a framework that allows us to fully exploit the mutually exclusive image information in our input data. We test our approach on various images and demonstrate that our approach can generate good reflection separation results. Index Terms—reflection separation, image enhancement (a) (b)

Naejin Kong; Yu-wing Tai; Sung Yong Shin

241

Volume of myocardium perfused by coronary artery branches as estimated from 3D micro-CT images of rat hearts  

NASA Astrophysics Data System (ADS)

Average myocardial perfusion is remarkably consistent throughout the heart wall under resting conditions and the velocity of blood flow is fairly reproducible from artery to artery. Based on these observations, and the fact that flow through an artery is the product of arterial cross-sectional area and blood flow velocity, we would expect the volume of myocardium perfused to be proportional to the cross-sectional area of the coronary artery perfusing that volume of myocardium. This relationship has been confirmed by others in pigs, dogs and humans. To test the body size-dependence of this relationship we used the hearts from rats, 3 through 25 weeks of age. The coronary arteries were infused with radiopaque microfil polymer and the hearts scanned in a micro- CT scanner. Using these 3D images we measured the volume of myocardium and the arterial cross-sectional area of the artery that perfused that volume of myocardium. The average constant of proportionality was found to be 0.15 +/- 0.08 cm3/mm2. Our data showed no statistically different estimates of the constant of proportionality in the rat hearts of different ages nor between the left and right coronary arteries. This constant is smaller than that observed in large animals and humans, but this difference is consistent with the body mass-dependence on metabolic rate.

Lund, Patricia E.; Naessens, Lauren C.; Seaman, Catherine A.; Reyes, Denise A.; Ritman, Erik L.

2000-04-01

242

Image quality evaluation based on image weighted separating block peak signal to noise ratio  

Microsoft Academic Search

Traditional objective image quality evaluation measures, such as the MSE or the PSNR, only represent the total difference between the original images and reconstructed images. However in some case, such as there are few large error pixels and many small error pixels in an image, they have not a consistent a result with subjective measure. To cope with this drawback,

Wang Yuanji; Li Jianhua; Lu Yi; Fu Yao; Jiang Qinzhong

2003-01-01

243

Optical imaging of resting-state functional connectivity in a novel arterial stiffness model  

PubMed Central

This study aims to assess the impact of unilateral increases in carotid stiffness on cortical functional connectivity measures in the resting state. Using a novel animal model of induced arterial stiffness combined with optical intrinsic signals and laser speckle imaging, resting state functional networks derived from hemodynamic signals are investigated for their modulation by isolated changes in stiffness of the right common carotid artery. By means of seed-based analysis, results showed a decreasing trend of homologous correlation in the motor and cingulate cortices. Furthermore, a graph analysis indicated a randomization of the cortex functional networks, suggesting a loss of connectivity, more specifically in the motor cortex lateral to the treated carotid, which however did not translate in differentiated metabolic activity. PMID:24298398

Guevara, Edgar; Sadekova, Nataliya; Girouard, Hélène; Lesage, Frédéric

2013-01-01

244

Digital Receptor Image Quality Evaluation: Effect of Different Filtration Schemes  

NASA Astrophysics Data System (ADS)

The International Electrotechnical Commission provides a standard measurement methodology to provide performance intercomparison between imaging systems. Its formalism specifies beam quality based on half value layer attained by target kVp and additional Al filtration. Similar beam quality may be attained more conveniently using a filtration combination of Cu and Al. This study aimed to compare the two filtration schemes by their effects on image quality in terms of signal-difference-to-noise ratio, spatial resolution, exposure index, noise power spectrum, modulation transfer function, and detective quantum efficiency. A comparative assessment of the images was performed by analyzing commercially available image quality assessment phantom and by following the IEC 62220-3 formalism.

Murphy, Simon; Christianson, Olav; Amurao, Maxwell; Samei, Ehsan

2010-04-01

245

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.

246

Multi-delay Arterial Spin Labeling Perfusion MRI in Moyamoya Disease – Comparison with CT Perfusion Imaging  

PubMed Central

Purpose To present a multi-delay multi-parametric pseudo-continuous ASL (pCASL) protocol that offers simultaneous measurements of cerebral blood flow (CBF), arterial transit time (ATT) and arterial cerebral blood volume (aCBV) and to evaluate its accuracy by comparison with CT perfusion in moyamoya disease. Materials and Methods A 4 post-labeling delay (PLD) pCASL protocol was applied on 17 patients with moyamoya disease who also underwent CT perfusion imaging. ATT was estimated using the multi-delay protocol and included in the calculation of CBF. ASL and CT perfusion images were rated for lesion severity/conspicuity. Pearson correlation coefficients were calculated across voxels between the two modalities in grey and white matter of each subject respectively and between normalized mean values of ASL and CT perfusion measures in major vascular territories. Results Significant associations between ASL and CT perfusion were detected using subjective ratings, voxel-wise analysis in grey and white matter and region of interest (ROI) based analysis of normalized mean perfusion. The correlation between ASL CBF and CT perfusion was improved using the multi-delay pCASL protocol compared to CBF acquired at a single PLD of 2 s (p<0.05). Conclusion There is a correlation between perfusion data from ASL and CT perfusion imaging in patients with moyamoya disease. Multi-delay ASL can improve CBF quantification, which could be a prognostic imaging biomarker in patients with moyamoya disease. PMID:24557051

Wang, Rui; Yu, Songlin; Alger, Jeffry R.; Zuo, Zhentao; Chen, Juan; Wang, Rong; An, Jing; Wang, Bo; Zhao, Jizong; Xue, Rong; Wang, Danny JJ

2014-01-01

247

The Quality of Reports on Cervical Arterial Dissection following Cervical Spinal Manipulation  

PubMed Central

Background Cervical artery dissection (CAD) and stroke are serious harms that are sometimes associated with cervical spinal manipulation therapy (cSMT). Because of the relative rarity of these adverse events, studying them prospectively is challenging. As a result, systematic review of reports describing these events offers an important opportunity to better understand the relation between adverse events and cSMT. Of note, the quality of the case report literature in this area has not yet been assessed. Purpose 1) To systematically collect and synthesize available reports of CAD that have been associated with cSMT in the literature and 2) assess the quality of these reports. Methods A systematic review of the literature was conducted using several databases. All clinical study designs involving CADs associated with cSMT were eligible for inclusion. Included studies were screened by two independent reviewers for the presence/absence of 11 factors considered to be important in understanding the relation between CAD and cSMT. Results Overall, 43 articles reported 901 cases of CAD and 707 incidents of stroke reported to be associated with cSMT. The most common type of stroke reported was ischemic stroke (92%). Time-to-onset of symptoms was reported most frequently (95%). No single case included all 11 factors. Conclusions This study has demonstrated that the literature infrequently reports useful data toward understanding the association between cSMT, CADs and stroke. Improving the quality, completeness, and consistency of reporting adverse events may improve our understanding of this important relation. PMID:23527121

Wynd, Shari; Westaway, Michael; Vohra, Sunita; Kawchuk, Greg

2013-01-01

248

Influence of chroma variations on naturalness and image quality of stereoscopic images  

NASA Astrophysics Data System (ADS)

The computational view on image quality of Janssen and Blommaert states that the quality of an image is determined by the degree to which the image is both useful (discriminability) and natural (identifiability). This theory is tested by creating two manipulations. Firstly, multiplication of the chroma values of each pixel with a constant in the CIELab color space, i.e., chroma manipulation, is expected to increase only the usefulness by increasing the distances between the individual color points, enhancing the contrast. Secondly, introducing stereoscopic depth by varying the screen disparity, i.e., depth manipulation, is expected to increase both the usefulness and the naturalness. Twenty participants assessed perceived image quality, perceived naturalness and perceived depth of the manipulated versions of two natural scenes. The results revealed a small, yet significant shift between image quality and naturalness as a function of the chroma manipulation. In line with previous research, preference in quality was shifted to higher chroma values in comparison to preference in naturalness. Introducing depth enhanced the naturalness scores, however, in contrast to our expectations, not the image quality scores. It is argued that image quality is not sufficient to evaluate the full experience of 3D. Image quality appears to be only one of the attributes underlying the naturalness of stereoscopic images.

Kuijsters, Andre; Ijsselsteijn, Wijnand A.; Lambooij, Marc T. M.; Heynderickx, Ingrid E. J.

2009-02-01

249

Digital Receptor Image Quality Evaluation: Effect of Different Filtration Schemes  

Microsoft Academic Search

The International Electrotechnical Commission provides a standard measurement methodology to provide performance intercomparison between imaging systems. Its formalism specifies beam quality based on half value layer attained by target kVp and additional Al filtration. Similar beam quality may be attained more conveniently using a filtration combination of Cu and Al. This study aimed to compare the two filtration schemes by

Simon Murphy; Olav Christianson; Maxwell Amurao; Ehsan Samei

2010-01-01

250

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 PMID:8043342

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

1994-01-01

251

Evaluation of the Combined Application of Ultrasound Imaging Techniques for Middle Cerebral Artery Stent Surveillance and Follow-Up Study  

PubMed Central

Objective In recent years, cerebral artery stenting has become an effective method for the treatment of cerebral artery stenosis. However, methods for assessing efficacy and techniques for follow-up imaging still need to be developed. This study was designed to evaluate the application of transcranial color-coded sonography (TCCS) in assessing stenting of middle cerebral artery (MCA) stenosis. And, two new imaging techniques (vascular enhancement technology (VET) and 3-dimensional (3D) imaging) were tried out and evaluated. Method We enrolled 43 patients with cerebral artery stenosis for vascular stent implantation. All patients were examined by ultrasonography and confirmed through digital subtraction angiography. The stenosis was imaged and blood flow parameters were analyzed before and after the procedure using TCCS. VET and 3D imaging model were used in part of the patients. Important postoperative hemodynamic changes were noted. Results 1) Adequate stent image was present in 41 out of 43 patients as detected by postoperative 2-dimensional imaging. Images lacking clarity were obtained in 2 patients. 2) The perioperative and postoperative (one week follow-up) instantaneous blood flow velocity at the site of stenosis was significantly decreased (P<0.05) when compared with preoperative levels. Differences between postoperative (one week follow-up) and preoperative blood flow velocity were significant (P<0.05). Differences in blood flow velocity at long-term follow-up (six months and two years) compared to one-week values were not statistically significant (P>0.05). 3) VET imaging visualizes the MCA lumen and stent morphology clearly. 3D ultrasound can be used for imaging of the stent shape as well as its inner surface. Conclusion TCCD can be considered a quick and effective clinical detection method to evaluate the intracranial arterial hemodynamics changes before and after stenting treatment for MCA stenosis. New imaging technologies 3D and VET can achieve additional image information. PMID:24236130

Liu, Xi; Wang, Jia; Li, Li Hong; Deng, Jian Ping; Duan, Yun You

2013-01-01

252

Food quality assessment by NIR hyperspectral imaging  

Microsoft Academic Search

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

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

2010-01-01

253

Automated tea quality classification by hyperspectral imaging.  

PubMed

A hyperspectral imaging technique was attempted to classify green tea. Five grades of green tea samples were attempted. A hyperspectral imaging system was developed for data acquisition of tea samples. Principal component analysis was performed on the hyperspectral data to determine three optimal band images. Texture analysis was conducted on each optimal band image to extract characteristic variables. A support vector machine (SVM) was used to construct the classification model. The classification rates were 98% and 95% in the training and prediction sets, respectively. The SVM algorithm shows excellent performance in classification results in contrast with other pattern recognitions classifiers. Overall results show that the hyperspectral imaging technique coupled with a SVM classifier can be efficiently utilized to classify green tea. PMID:19571909

Zhao, Jiewen; Chen, Quansheng; Cai, Jianrong; Ouyang, Qin

2009-07-01

254

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. PMID:21258446

Mostaço-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

255

Smoothing depth maps for improved steroscopic image quality  

Microsoft Academic Search

A technique to improve the image quality of stereoscopic pictures generated from depth maps (depth image based rendering or DIBR) is examined. In general, there are two fundamental problems with DIBR: a depth map could contain artifacts (e.g., noise or \\

Wa James Tam; Guillaume Alain; Liang Zhang; Taali Martin; Ronald Renaud

2004-01-01

256

Low Resolution Character Recognition by Image Quality Evaluation  

Microsoft Academic Search

The character image database plays an important role for the evaluation of a character recognition system. But there is no measure which tells the level of recognition difficulty of a given database. This paper proposes a novel approach for the low resolution character recognition, which fits the input character for the appropriate character database according to the input image quality.

Chunmei Liu; Chunheng Wang; Ruwei Dai

2006-01-01

257

Free viewpoint image quality evaluation based on ray space  

Microsoft Academic Search

Free viewpoint video (FW) is on its research stage with many problems to be resolved. Due to no original data can be used to compare with when the arbitrary viewpoint image is reproduced, quality evaluation for the new viewpoint image becomes one of the difficulties in realizing FW. Ray space representation is the main approach to realize FVV of complex

Li Zhou; Ping An; Zhaoyang Zhang; Ying Zhang

2008-01-01

258

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

259

A new quality metric for compressed images based on DDCT  

NASA Astrophysics Data System (ADS)

As the performance-indicator of the image processing algorithms or systems, image quality assessment (IQA) has attracted the attention of many researchers. Aiming to the widely used compression standards, JPEG and JPEG2000, we propose a new no reference (NR) metric for compressed images to do IQA. This metric exploits the causes of distortion by JPEG and JPEG2000, employs the directional discrete cosine transform (DDCT) to obtain the detail and direction information of the images and incorporates with the visual perception to obtain the image quality index. Experimental results show that the proposed metric not only has outstanding performance on JPEG and JPEG2000 images, but also applicable to other types of artifacts.

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

2010-07-01

260

High quality image oriented telemedicine with multimedia technology  

Microsoft Academic Search

Researchers at Osaka and Kyoto University hospital performed three experiments, beginning in 1995, which looked at high quality-oriented telemedicine. This paper describes the system design for the three projects. Experiment 1 applied high-definition TV images and B-ISDN for distance learning and medical information exchange. Experiment 2 developed a super high-definition medical image filing system and the images were transmitted via

Hiroshi Takeda; Kotaro Minato; Takashi Takahasi

1999-01-01

261

Regional aortic compliance studied by magnetic resonance imaging: the effects of age, training, and coronary artery disease.  

PubMed Central

Arterial compliance was measured in 70 healthy volunteers, 13 athletes, and 17 patients with coronary artery disease. Magnetic resonance images were acquired at end diastole and end systole through the ascending aorta, the aortic arch, and the descending thoracic aorta. Regional compliance was derived from the change in luminal area in a slice of known thickness and from the pulse pressure. Total arterial compliance was also measured from the left ventricular stroke volume and the pulse pressure. In the volunteers, mean (SD) regional compliance (microliters/mm Hg) was greatest in the ascending aorta (37 (18], lower in the arch (31 (15], and lowest in the descending aorta (18 (8], and it decreased with age. Compliance in the athletes was significantly higher than in their age matched controls (41 (16) versus 22 (11) microliters/mm Hg). In the patients with coronary artery disease it was significantly lower (12 (4) v 18 (10] than in age matched controls. Total arterial compliance also fell with age in those with coronary artery disease although there was more variation. The results suggest a possible role for compliance in the assessment of cardiovascular fitness and the detection of coronary artery disease. Images Fig 1 Fig 2 PMID:2765331

Mohiaddin, R H; Underwood, S R; Bogren, H G; Firmin, D N; Klipstein, R H; Rees, R S; Longmore, D B

1989-01-01

262

Serial right ventricle /sup 201/Tl imaging after exercise: relation to anatomy of the right coronary artery  

SciTech Connect

The relation of the appearance of the right ventricle on serium /sup 201/Tl myocardial imaging to coronary artery anatomy was examined in 88 consecutive patients undergoing exercise /sup 201/Tl testing and coronary angiography for the evaluation of chest pain. Transient defects in the right ventricle were found in 8 patients. All had high grade (greater than or equal to 90%) stenosis of the proximal right coronary artery. Nonvisualization of right ventricular (RV) activity occurred in 10 patients. Nine of the 10 (90%) had significant (greater than or equal to 50% stenosis) disease of the proximal right coronary artery and 7 (70%) had high grade stenosis. The right ventricle appeared normal in 70 patients. Twenty-nine (41%) of these patients had significant proximal right coronary artery disease. Right ventricular appearance was not affected by the presence or absence of disease of the left anterior descending or left circumflex artery or by the appearance of the left ventricle. Thus, with serial RV thallium-201 myocardial imaging after exercise, we found that (1) RV transient defects suggest the presence of high grade proximal right coronary artery stenosis, (2) non-visualization of RV activity also predicts significant proximal right coronary disease, and (3) the right ventricle frequently appears normal despite proximal right coronary artery disease and therefore this finding does not exclude such disease.

Brown, K.A.; Boucher, C.A.; Okada, R.D.; Strauss, H.W.; McKusick, K.A.; Pohost, G.M.

1982-12-01

263

Comparison of cardiac and pulmonary-specific quality-of-life measures in pulmonary arterial hypertension.  

PubMed

Studies systematically comparing the performance of health-related quality-of-life (HRQoL) instruments in pulmonary arterial hypertension (PAH) are lacking. We sought to address this by comparing cardiac and respiratory-specific measures of HRQoL in PAH. We prospectively assessed HRQoL in 128 patients with catheterisation-confirmed PAH at baseline and at 6, 12 and post-24 month follow-up visits. Cardiac-specific HRQoL was assessed using the Minnesota Living with Heart Failure Questionnaire (LHFQ); respiratory-specific HRQoL was assessed using the Airways Questionnaire 20 (AQ20); and general health status was assessed using the 36-item Short Form physical component summary (SF-36 PCS). The LHFQ and AQ20 were highly intercorrelated. Both demonstrated strong internal consistency and converged with the SF-36 PCS. Both discriminated patients based on World Health Organization (WHO) functional class, 6-min walking distance (6MWD) and Borg dyspnoea index (BDI), with the exception of a potential floor effect associated with low 6MWD. The LHFQ was more responsive than the AQ20 to changes over time in WHO functional class, 6MWD and BDI. In multivariate analyses, the LHFQ and AQ20 were each longitudinal predictors of general health status, independent of functional class, 6MWD and BDI. In conclusion, both cardiac-specific and respiratory-specific measures appropriately assess HRQoL in most patients with PAH. Overall, the LHFQ demonstrates stronger performance characteristics than the AQ20. PMID:21273391

Chen, H; De Marco, T; Kobashigawa, E A; Katz, P P; Chang, V W; Blanc, P D

2011-09-01

264

Tumor Encasement of the Right Coronary Artery: Role of Anatomic and Functional Imaging in Diagnosis and Therapeutic Management  

PubMed Central

We presented two rare cases of mediastinal tumor encasing the right coronary artery (RCA), one with recurrent metastatic thymoma and another with primary poorly differentiated neoplasm. Different degrees and locations of RCA involvement were noted. The treatment approach varied from conservative to surgical. Coronary artery involvement by mediastinal tumors is important to be investigated with imaging as it may guide the surgical planning. PMID:25422676

Juan, Yu-Hsiang; Chatzizisis, Yiannis S; Saboo, Sachin S; Rocha, Tatiana; Steigner, Michael L

2014-01-01

265

Virtual arterial blood pressure feedback improves chest compression quality during simulated resuscitation?  

PubMed Central

Introduction Quality chest compressions (CC) are the most important factor in successful cardiopulmonary resuscitation. Adjustment of CC based upon an invasive arterial blood pressure (ABP) display would be theoretically beneficial. Additionally, having one compressor present for longer than a 2-min cycle with an ABP display may allow for a learning process to further maximize CC. Accordingly, we tested the hypothesis that CC can be improved with a real-time display of invasively measured blood pressure and with an unchanged, physically fit compressor. Methods A manikin was attached to an ABP display derived from a hemodynamic model responding to parameters of CC rate, depth, and compression-decompression ratio. The area under the blood pressure curve over time (AUC) was used for data analysis. Each participant (N = 20) performed 4 CPR sessions: (1) No ABP display, exchange of compressor every 2 min; (2) ABP display, exchange of compressor every 2 min; (3) no ABP display, no exchange of the compressor; (4) ABP display, no exchange of the compressor. Data were analyzed by ANOVA. Significance was set at a p-value < 0.05. Results The average AUC for cycles without ABP display was 5201 mmHg s (95% confidence interval (CI) of 4804–5597 mmHg s), and for cycles with ABP display 6110 mmHg s (95% CI of 5715–6507 mmHg s) (p< 0.0001). The average AUC increase with ABP display for each participant was 20.2 ± 17.4% 95 CI (p < 0.0001). Conclusions Our study confirms the hypothesis that a real-time display of simulated ABP during CPR that responds to participant performance improves achieved and sustained ABP. However, without any real-time visual feedback, even fit compressors demonstrated degradation of CC quality. PMID:23816900

Rieke, Horst; Rieke, Martin; Gado, Samkon K.; Nietert, Paul J.; Field, Larry C.; Clark, Carlee A.; Furse, Cory M.; McEvoy, Matthew D.

2014-01-01

266

Bio-inspired framework for automatic image quality enhancement  

NASA Astrophysics Data System (ADS)

We propose a bio-inspired framework for automatic image quality enhancement. Restoration algorithms usually have fixed parameters whose values are not easily settable and depend on image content. In this study, we show that it is possible to correlate no-reference visual quality values to specific parameter settings such that the quality of an image could be effectively enhanced through the restoration algorithm. In this paper, we chose JPEG blockiness distortion as a case study. As for the restoration algorithm, we used either a bilateral filter, or a total variation denoising detexturer. The experimental results on the LIVE database will be reported. These results will demonstrate that a better visual quality is achieved through the optimized parameters over the entire range of compression, with respect to the algorithm default parameters.

Ceresi, Andrea; Gasparini, Francesca; Marini, Fabrizio; Schettini, Raimondo

2012-01-01

267

High Speed Terahertz Pulse Imaging in the Reflection Geometry and Image Quality Enhancement by Digital Image Processing  

NASA Astrophysics Data System (ADS)

We describe the formation and enhancement of two dimensional pulsed terahertz (THz) images obtained in the reflection geometry with a high-speed optical delay line. Two test objects are imaged and analyzed with respect to material information and concealed structure. Clear THz images were obtained with various imaging modes and were compared with the X-ray images. The THz image of a sample revealed material features that the X-ray image cannot distinguish. We could enhance the THz image quality using various image processing techniques, such as edge detection, de-noising, high-pass filtering, and wavelet filtering.

Shon, Chae-Hwa; Chong, Won-Yong; Jeon, Seok-Gy; Kim, Geun-Ju; Kim, Jung-Il; Jin, Yun-Sik

2008-01-01

268

Peripheral Aberrations and Image Quality for Contact Lens Correction  

PubMed Central

Purpose Contact lenses reduced the degree of hyperopic field curvature present in myopic eyes and rigid contact lenses reduced sphero-cylindrical image blur on the peripheral retina, but their effect on higher order aberrations and overall optical quality of the eye in the peripheral visual field is still unknown. The purpose of our study was to evaluate peripheral wavefront aberrations and image quality across the visual field before and after contact lens correction. Methods A commercial Hartmann-Shack aberrometer was used to measure ocular wavefront errors in 5° steps out to 30° of eccentricity along the horizontal meridian in uncorrected eyes and when the same eyes are corrected with soft or rigid contact lenses. Wavefront aberrations and image quality were determined for the full elliptical pupil encountered in off-axis measurements. Results Ocular higher-order aberrations increase away from fovea in the uncorrected eye. Third-order aberrations are larger and increase faster with eccentricity compared to the other higher-order aberrations. Contact lenses increase all higher-order aberrations except 3rd-order Zernike terms. Nevertheless, a net increase in image quality across the horizontal visual field for objects located at the foveal far point is achieved with rigid lenses, whereas soft contact lenses reduce image quality. Conclusions Second order aberrations limit image quality more than higher-order aberrations in the periphery. Although second-order aberrations are reduced by contact lenses, the resulting gain in image quality is partially offset by increased amounts of higher-order aberrations. To fully realize the benefits of correcting higher-order aberrations in the peripheral field requires improved correction of second-order aberrations as well. PMID:21873925

Shen, Jie; Thibos, Larry N.

2011-01-01

269

Image gathering and restoration - Information and visual quality  

NASA Technical Reports Server (NTRS)

A method is investigated for optimizing the end-to-end performance of image gathering and restoration for visual quality. To achieve this objective, one must inevitably confront the problems that the visual quality of restored images depends on perceptual rather than mathematical considerations and that these considerations vary with the target, the application, and the observer. The method adopted in this paper is to optimize image gathering informationally and to restore images interactively to obtain the visually preferred trade-off among fidelity resolution, sharpness, and clarity. The results demonstrate that this method leads to significant improvements in the visual quality obtained by the traditional digital processing methods. These traditional methods allow a significant loss of visual quality to occur because they treat the design of the image-gathering system and the formulation of the image-restoration algorithm as two separate tasks and fail to account for the transformations between the continuous and the discrete representations in image gathering and reconstruction.

Mccormick, Judith A.; Alter-Gartenberg, Rachel; Huck, Friedrich O.

1989-01-01

270

Hepatic Arterial Phase on Gadoxetic Acid-Enhanced Liver MR Imaging: A Randomized Comparison of 0.5 mL/s and 1 mL/s Injection Rates  

PubMed Central

Objective To compare gadoxetic acid injection rates of 0.5 mL/s and 1 mL/s for hepatic arterial-phase magnetic resonance (MR) imaging. Materials and Methods In this prospective study, 101 consecutive patients with suspected focal liver lesions were included and randomly divided into two groups. Each group underwent dynamic liver MR imaging using a 3.0-T scanner after an intravenous injection of gadoxetic acid at rates of either 0.5 mL/s (n = 50) or 1 mL/s (n = 51). Arterial phase images were analyzed after blinding the injection rates. The signal-to-noise ratios (SNRs) of the liver, aorta, portal vein, hepatic vein, spleen, and pancreas were measured. The contrast-to-noise ratios (CNRs) of the hepatocellular carcinomas (HCC) were calculated. Finally, two experienced radiologists were independently asked to identify, if any, HCCs in the liver on the images and score the image quality in terms of the presence of artifacts and the proper enhancement of the liver, aorta, portal vein, hepatic vein, hepatic artery, spleen, pancreas, and kidney. Results The SNRs were not significantly different between the groups (p = 0.233-0.965). The CNRs of the HCCs were not significantly different (p = 0.597). The sensitivity for HCC detection and the image quality scores were not significantly different between the two injection rates (p = 0.082-1.000). Conclusion Image quality and sensitivity for hepatic HCCs of arterial-phase gadoxetic acid-enhanced MR were not significantly improved by reducing the contrast injection rate to 0.5 mL/s compared with 1 mL/s. PMID:25246821

Kim, Sung Mo; Heo, Suk Hee; Kim, Jin Woong; Lim, Hyo Soon; Shin, Sang Soo; Kang, Heoung Keun

2014-01-01

271

Improving high resolution retinal image quality using speckle illumination HiLo imaging.  

PubMed

Retinal image quality from flood illumination adaptive optics (AO) ophthalmoscopes is adversely affected by out-of-focus light scatter due to the lack of confocality. This effect is more pronounced in small eyes, such as that of rodents, because the requisite high optical power confers a large dioptric thickness to the retina. A recently-developed structured illumination microscopy (SIM) technique called HiLo imaging has been shown to reduce the effect of out-of-focus light scatter in flood illumination microscopes and produce pseudo-confocal images with significantly improved image quality. In this work, we adopted the HiLo technique to a flood AO ophthalmoscope and performed AO imaging in both (physical) model and live rat eyes. The improvement in image quality from HiLo imaging is shown both qualitatively and quantitatively by using spatial spectral analysis. PMID:25136486

Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

2014-08-01

272

Noisy images-JPEG compressed: subjective and objective image quality evaluation  

NASA Astrophysics Data System (ADS)

The aim of this work is to study image quality of both single and multiply distorted images. We address the case of images corrupted by Gaussian noise or JPEG compressed as single distortion cases and images corrupted by Gaussian noise and then JPEG compressed, as multiply distortion case. Subjective studies were conducted in two parts to obtain human judgments on the single and multiply distorted images. We study how these subjective data correlate with No Reference state-of-the-art quality metrics. We also investigate proper combining of No Reference metrics to achieve better performance. Results are analyzed and compared in terms of correlation coefficients.

Corchs, Silvia; Gasparini, Francesca; Schettini, Raimondo

2014-01-01

273

Steganalysis of watermarking techniques using image quality metrics  

NASA Astrophysics Data System (ADS)

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 feature set to distinguish between watermarked and unwatermarked images. To identify specific quality measures, which provide the best discriminative power, we use analysis of variance (ANOVA) techniques. The multivariate regression analysis is used on the selected quality metrics to build the optimal classifier using images and their blurred versions. The idea behind blurring is that the distance between an unwatermarked image and its blurred version is less than the distance between a watermarked image and its blurred version. Simulation results with a specific feature set and a well-known and commercially available watermarking technique indicates that our approach is able to accurately distinguish between watermarked and unwatermarked images.

Avcibas, Ismail; Memon, Nasir D.; Sankur, Bulent

2001-08-01

274

WAVELET-BASED FOVEATED IMAGE QUALITY MEASUREMENT FOR REGION OF INTEREST IMAGE CODING  

E-print Network

WAVELET-BASED FOVEATED IMAGE QUALITY MEASUREMENT FOR REGION OF INTEREST IMAGE CODING Zhou Wang1 "fixated" by human eyes, the foveation property of the HVS supplies a natural approach for guiding and enhancement of ROI coded images and videos. We show its effectiveness by applying it to an embedded foveated

Wang, Zhou

275

Human vision model for image quality evaluation suitable for smart imager implementation  

Microsoft Academic Search

This article deals with image quality evaluation ofthe compressed images especially for compression format JPEG 2000. It shows evaluation of selected test images (scene with: textures, details, text, color of face, etc.) using selected methods: subjective testing as the reference method, objective testing and two designed human vision models. At the end article compares results of these methods.

Jaroslav Dusek; Karel Roubík; Martin Bernas

2005-01-01

276

Imaging of carotid artery vessel wall edema using T2-weighted cardiovascular magnetic resonance  

PubMed Central

Background Atherothrombosis remains a major health problem in the western world, and carotid atherosclerosis is an important contributor to embolic ischemic strokes. It remains a clinical challenge to identify rupture-prone atherosclerotic plaques before clinical events occur. Inflammation, endothelial injury and angiogenesis are features of vulnerable plaques and may all be associated with plaque edema. Therefore, vessel wall edema, which can be detected by 2D T2-weighted cardiovascular magnetic resonance (CMR), may be used as a dynamic marker of disease activity in the atherosclerotic plaque. However, 2D imaging is limited by low spatial resolution in the slice-select direction compared to 3D imaging techniques. We sought to investigate the ability of novel 3D techniques to detect edema induced in porcine carotid arteries by acute balloon injury compared to conventional 2D T2-weighted black-blood CMR. Methods Edema was induced unilaterally by balloon overstretch injury in the carotid artery of nine pigs. Between one to seven hours (average four hours) post injury, CMR was performed using 2D T2-weighted short-tau inversion recovery (T2-STIR), 3D volumetric isotropic turbo spin echo acquisition (VISTA) and 3D T2 prepared gradient-echo (T2prep-GE). The CMR images were compared in terms of signal-to-noise ratio (SNR) and contrast-to-noise (CNR) ratio. Furthermore, the presence of vessel wall injury was validated macroscopically by means of Evans Blue dye that only enters the injured vessel wall. Results All three imaging sequences classified the carotid arteries correctly compared to Evans Blue and all sequences demonstrated a significant increase in SNR of the injured compared to the non-injured carotid vessel wall (T2-STIR, p?=?0.002; VISTA, p?=?0.004; and T2prep-GE, p?=?0.003). There was no significant difference between sequences regarding SNR and CNR. Conclusion The novel 3D imaging sequences VISTA and T2prep-GE perform comparably to conventional 2D T2-STIR in terms of detecting vessel wall edema. The improved spatial coverage of these 3D sequences may facilitate visualization of vessel wall edema to enable detection and monitoring of vulnerable carotid atherosclerotic plaques. PMID:24593873

2014-01-01

277

[Small imaging spectrometer for the inspection of fruit quality].  

PubMed

Imaging spectrometer can acquire spatial and spectral information of the target at the same time, achieve high-precision, non-destructive, non-contamination and large area instantaneous inspection of the fruit. In order to get the imaging spectrum of the fruit, compact imaging spectrometer with convex grating produced by self was designed, it has the advantages of good performance, small volume and low weight, its resolution at 578 nm is 2.1 nm, and spectral line bend and chromatic distortion are both smaller than 0.6%. Laboratory test of the imaging spectrometer and the experiment of getting the imaging spectrum of apple were done, and the result shows that the imaging spectrometer satisfies the design requirement and can acquire the imaging spectrum of apple rapidly with high precision for inspection of fruit quality. PMID:22497177

Liu, Yu-juan; Tang, Yu-guo; Cui, Ji-cheng; Bayanheshig

2012-01-01

278

Evidence quality imaging for bank security  

Microsoft Academic Search

A long standing problem within the banking security and law enforcement communities has been the inability to use the images recorded with conventional security cameras as definitive evidence in a court of law. The issue with affordable solid state or tube security cameras is the spatial resolution and gray scale resolution. Neither is sufficient. Alternatives using film cameras have proved

P. Gallagher; S. Doyle

1995-01-01

279

A SPECT study in internal carotid artery occlusion: Discrepancies between flow image and neurologic deficits  

SciTech Connect

A SPECT (single photon emission computed tomography) study in internal carotid artery (ICA) occlusion was performed in 6 patients. The validity of iodoamphetamine (IMP) SPECT study in the evaluation of cerebral blood flow (CBF) or neurologic function is still controversial. In this study, the authors showed several cases in whom SPECT images of brain were not compatible with their neurologic deficits. In 2 typical cases, a large low-density area was observed in the non-dominant hemisphere in computed tomography (CT) scan, but no apparent motor-sensory deficits in left limbs were present. In these patients, SPECT study also revealed flow reduction in the affected side of the brain. So there was a possibility that an IMP brain image could not always reflect CBF, which maintains neurologic function of the brain.

Moriwaki, H.; Hougaku, H.; Matsuda, I.; Kusunoki, M.; Shirai, J. (Kobe Ekisaikai Hospital (Japan))

1989-08-01

280

Imaging of high-risk carotid artery plaques: current status and future directions.  

PubMed

In this paper, the authors review the definition of high-risk plaque as developed by experienced researchers in atherosclerosis, including pathologists, clinicians, molecular biologists, and imaging scientists. Current concepts of vulnerable plaque are based on histological studies of coronary and carotid artery plaque as well as natural history studies and include the presence of a lipid-rich necrotic core with an overlying thin fibrous cap, plaque inflammation, fissured plaque, and intraplaque hemorrhage. The extension of these histologically identified high-risk carotid plaque features to human in vivo MRI is reviewed as well. The authors also assess the ability of in vivo MRI to depict these vulnerable carotid plaque features. Next, the ability of these MRI-demonstrated high-risk carotid plaque features to predict the risk of ipsilateral carotid thromboembolic events is reviewed and compared with the risk assessment provided by simple carotid artery stenosis measurements. Lastly, future directions of high-risk carotid plaque MRI are discussed, including the potential for increased clinical availability and more automated analysis of carotid plaque MRI. The ultimate goal of high-risk plaque imaging is to design and run future multicenter trials using carotid plaque MRI to guide individual patient selection and decisions about optimal atherosclerotic treatment strategies. PMID:24380475

DeMarco, J Kevin; Huston, John

2014-01-01

281

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

282

A fast iris image quality evaluation method based on weighted entropy  

Microsoft Academic Search

During the image acquisition procedure of an automatic iris recognition system, the iris image with low quality may lead to the personal identification failure in some cases. Therefore it is very important to adopt the image quality evaluation procedure before the image processing. In this paper, we proposed a fast image quality evaluation method based on weighted information entropy combining

Yuqing He; Ting Liu; Yushi Hou; Yuanbo Wang

2008-01-01

283

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

284

Separation of arteries and veins in the cerebral cortex using physiological oscillations by optical imaging of intrinsic signal.  

PubMed

An automated method is presented for artery-vein separation in cerebral cortical images recorded with optical imaging of the intrinsic signal. The vessel-type separation method is based on the fact that the spectral distribution of intrinsic physiological oscillations varies from arterial regions to venous regions. In arterial regions, the spectral power is higher in the heartbeat frequency (HF), whereas in venous regions, the spectral power is higher in the respiration frequency (RF). The separation method was begun by extracting the vascular network and its centerline. Then the spectra of the optical intrinsic signals were estimated by the multitaper method. A standard F-test was performed on each discrete frequency point to test the statistical significance at the given level. Four periodic physiological oscillations were examined: HF, RF, and two other eigenfrequencies termed F1 and F2. The separation of arteries and veins was implemented with the fuzzy c-means clustering method and the region-growing approach by utilizing the spectral amplitudes and power-ratio values of the four eigenfrequencies on the vasculature. Subsequently, independent spectral distributions in the arteries, veins, and capillary bed were estimated for comparison, which showed that the spectral distributions of the intrinsic signals were very distinct between the arterial and venous regions. PMID:20615027

Hu, Dewen; Wang, Yucheng; Liu, Yadong; Li, Ming; Liu, Fayi

2010-01-01

285

Quantitative quality control in microarray image processing and data acquisition.  

PubMed

A new integrated image analysis package with quantitative quality control schemes is described for cDNA microarray technology. The package employs an iterative algorithm that utilizes both intensity characteristics and spatial information of the spots on a microarray image for signal-background segmentation and defines five quality scores for each spot to record irregularities in spot intensity, size and background noise levels. A composite score q(com) is defined based on these individual scores to give an overall assessment of spot quality. Using q(com) we demonstrate that the inherent variability in intensity ratio measurements is closely correlated with spot quality, namely spots with higher quality give less variable measurements and vice versa. In addition, gauging data by q(com) can improve data reliability dramatically and efficiently. We further show that the variability in ratio measurements drops exponentially with increasing q(com) and, for the majority of spots at the high quality end, this improvement is mainly due to an improvement in correlation between the two dyes. Based on these studies, we discuss the potential of quantitative quality control for microarray data and the possibility of filtering and normalizing microarray data using a quality metrics-dependent scheme. PMID:11470890

Wang, X; Ghosh, S; Guo, S W

2001-08-01

286

High-resolution MR imaging of the arterial wall in moyamoya disease.  

PubMed

High resolution magnetic resonance imaging (HRMRI) has been developed as an emerging tool for evaluating intracranial arterial disease. We aimed to analyze the progression of diseased arterial walls in moyamoya disease (MMD) and further elucidate differences compared to intracranial atherosclerotic stenosis using HRMRI. The population of this HRMRI study consisted of 21 patients with MMD and 44 patients with atherosclerotic middle cerebral artery (MCA) stenosis. The cross-sectional images of the MCA wall on HRMRI were compared between the two groups based on outer diameter, wall thickness, luminal stenotic morphology, signal intensity, collateral vascular structures adjacent to stenotic position. In addition, stage classification based on MRA finding was used to depict the course of moyamoya disease. We compared outer diameter and wall thickness of the MCAs in different MRA stages. As a result, the outer diameter and wall thickness of MCAs were significantly smaller in the MMD group than in the atherosclerosis group (outer diameter: MMD 2.01 ± 0.31 mm vs. atherosclerosis 3.31 ± 0.37 mm, p<0.001 and wall thickness: MMD 0.39 ± 0.19 mm vs. atherosclerosis 1.64 ± 0.38 mm, p < 0.001). The concentric stenosis (91.4% in MMD vs. 36.9% in atherosclerosis group, p < 0.001), homogeneous signal intensity (85.7% in MMD vs. 32.6% in atherosclerosis group, p < 0.001) and collateral vascular structures (54.3% in MMD vs. 8.7% in atherosclerosis group, p < 0.001) were more common in MMD patients. In addition, the outer diameter of MCAs in MMD was significantly different between MRA stage 1 and MRA stage 3 or 4 (MRA stage 1 vs. MRA stage 3, Nemenyi test p = 0.005 and MRA stage 1 vs. MRA stage 4, Nemenyi test p = 0.009). But the wall thickness of MCAs was no significantly different in different MRA stages (Kruskal-wallis H test, p = 0.074). We conclude that HRMRI may be used to identify different types of middle cerebral artery stenosis. MMD was characterized by concentric stenosis, homogeneous signal intensity, and collateral vascular structures in the affected MCA segments by HRMRI. Pathological shrinkage of MCA was an important phenomenon in MMD progression. PMID:25459282

Yuan, Min; Liu, Zhi-qiang; Wang, Zhi-qiang; Li, Bin; Xu, Li-jun; Xiao, Xin-lan

2015-01-01

287

[Peripheral arteries].  

PubMed

Peripheral arterial disease is a main cause of morbidity in industrialised countries. It chiefly affects older people. The most common causes are atherosclerosis and vasodilatatory abnormalities. In the presence of unexplained leg symptoms, peripheral arterial disease can be diagnosed or ruled out by non-invasive diagnostic methods such as history, clinical examination and the measurement of ankle and brachial artery pressure by Doppler ultrasound, as well as by calculating the ankle brachial index. Colour coded duplex sonography, computer tomography angiography, magnetic resonance angiography and arteriography are the imaging modalities used. Current diagnostic strategies are analysed for the different peripheral artery diseases. PMID:17479237

Vosshenrich, R; Reimer, P; Landwehr, P

2007-06-01

288

Follow-up outcomes 10 years after arterial switch operation for transposition of the great arteries: comparison of cardiological health status and health-related quality of life to those of the a normal reference population  

Microsoft Academic Search

The purpose of this study was to investigate the cardiological health status and health-related quality of life after the\\u000a arterial switch operation (ASO) for transposition of the great arteries (TGA) in comparison with a normative reference group.\\u000a Chart review and cross-sectional systematic follow-up, including echocardiography, exercise testing, and electrocardiography,\\u000a were performed on all survivors of ASO for TGA between 1990

Wilfred B. de Koning; Magdalena van Osch-Gevers; A. Derk Jan Ten Harkel; Ron T. van Domburg; Alma W. Spijkerboer; Elisabeth M. W. J. Utens; Ad J. J. C. Bogers; Willem A. Helbing

2008-01-01

289

Colour naturalness metric for evaluating image quality of mobile displays  

NASA Astrophysics Data System (ADS)

A series of psychophysical experiments using categorical judgment method was carried out to develop a colour naturalness metric (CNM) for evaluating image quality of mobile displays. These experiments included colour naturalness judgment and image-quality difference judgment. Through the former one, CNMs were trained and the latter experiment tested the metrics. Two types of CNMs were newly proposed: nonlinearly decaying CNM and linearly decaying CNM. In the CNMs, it was assumed that one familiar object in an image played a critical role to judge the colour naturalness of the whole image. Through a performance comparison between objects' models, one critical object in a scene was selected and with the critical object's model, the whole scene's colour naturalness was predicted.

Yoo, Jang Jin; Cui, Guihua; Luo, M. Ronnier

2009-01-01

290

APQ-102 imaging radar digital image quality study  

NASA Technical Reports Server (NTRS)

A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

Griffin, C. R.; Estes, J. M.

1982-01-01

291

Exploratory survey of image quality on CR digital mammography imaging systems in Mexico.  

PubMed

The purpose of this study was to assess the current status of image quality and dose in computed radiographic digital mammography (CRDM) systems. Studies included CRDM systems of various models and manufacturers which dose and image quality comparisons were performed. Due to the recent rise in the use of digital radiographic systems in Mexico, CRDM systems are rapidly replacing conventional film-screen systems without any regard to quality control or image quality standards. Study was conducted in 65 mammography facilities which use CRDM systems in the Mexico City and surrounding States. The systems were tested as used clinically. This means that the dose and beam qualities were selected using the automatic beam selection and photo-timed features. All systems surveyed generate laser film hardcopies for the radiologist to read on a scope or mammographic high luminance light box. It was found that 51 of CRDM systems presented a variety of image artefacts and non-uniformities arising from inadequate acquisition and processing, as well as from the laser printer itself. Undisciplined alteration of image processing settings by the technologist was found to be a serious prevalent problem in 42 facilities. Only four of them showed an image QC program which is periodically monitored by a medical physicist. The Average Glandular Dose (AGD) in the surveyed systems was estimated to have a mean value of 2.4 mGy. To improve image quality in mammography and make more efficient screening mammographic in early detection of breast cancer is required new legislation. PMID:23938078

Gaona, E; Rivera, T; Arreola, M; Franco, J; Molina, N; Alvarez, B; Azorín, C G; Casian, G

2014-01-01

292

Reduction of errors in ASL cerebral perfusion and arterial transit time maps using image de-noising.  

PubMed

In this work, the performance of image de-noising techniques for reducing errors in arterial spin labeling cerebral blood flow and arterial transit time estimates is investigated. Simulations were used to show that the established arterial spin labeling cerebral blood flow quantification method exhibits the bias behavior common to nonlinear model estimates, and as a result, the reduction of random errors using image de-noising can improve accuracy. To assess the effect on precision, multiple arterial spin labeling data sets acquired from the rat brain were processed using a variety of common de-noising methods (Wiener filter, anisotropic diffusion filter, gaussian filter, wavelet decomposition, and independent component analyses). The various de-noising schemes were also applied to human arterial spin labeling data to assess the possible extent of structure degradation due to excessive spatial smoothing. The animal experiments and simulated data show that noise reduction methods can suppress both random and systematic errors, improving both the precision and accuracy of cerebral blood flow measurements and the precision of transit time maps. A number of these methods (and particularly independent component analysis) were shown to achieve this aim without compromising image contrast. PMID:20578044

Wells, Jack A; Thomas, David L; King, Martin D; Connelly, Alan; Lythgoe, Mark F; Calamante, Fernando

2010-09-01

293

Image quality against metric capability of an aerial camera  

NASA Technical Reports Server (NTRS)

Glass plate targets containing multiple contrast three bar patterns and a military standard resolution target were photographed through a light-source collimator-camera system. The glass plate targets and images were then scanned. Through a computer plotting program selected portions of the scanned items were presented. The plots were then measured and analyzed to obtain information of image quality parameters and effects. The measurement errors are discussed together with aspects of resolution determination.

Ghosh, S. K.

1973-01-01

294

Objective quality evaluation of visible and infrared color fusion image  

NASA Astrophysics Data System (ADS)

An evaluation for objectively assessing the quality of visible and infrared color fusion image is proposed. On the basis of the consideration that human perception is most sensitive to color, sharpness, and contrast when assessing the quality of color image, we propose four objective metrics: image sharpness metric (ISM), image contrast metric (ICM), color colorfulness metric (CCM), and color naturalness metric (CNM). The ISM is evaluated by image gradient information. The ICM is defined based on both gray and color histogram characteristics. A color chroma metric, as well as a color variety metric based on a color difference gradient, is proposed, respectively, to define the CCM. The CNM is defined by measuring the color distribution's similarity between the fusion image and nature image, which are of the same scene. All the color attributions are computed in the CIELAB color space. Experimental results show that the proposed objective metrics are meaningful and effective on color fusion image evaluation because they correspond well to subjective evaluation.

Yuan, Yihui; Zhang, Junju; Chang, Benkang; Han, Yiyong

2011-03-01

295

No-reference image quality assessment for horizontal-path imaging scenarios  

NASA Astrophysics Data System (ADS)

There exist several image-enhancement algorithms and tasks associated with imaging through turbulence that depend on defining the quality of an image. Examples include: "lucky imaging", choosing the width of the inverse filter for image reconstruction, or stopping iterative deconvolution. We collected a number of image quality metrics found in the literature. Particularly interesting are the blind, "no-reference" metrics. We discuss ways of evaluating the usefulness of these metrics, even when a fully objective comparison is impossible because of the lack of a reference image. Metrics are tested on simulated and real data. Field data comes from experiments performed by the NATO SET 165 research group over a 7 km distance in Dayton, Ohio.

Rios, Carlos; Gladysz, Szymon

2013-05-01

296

Digital image correlation for full-field time-resolved assessment of arterial stiffness.  

PubMed

Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19??m/s as measured with DIC and between 5.14 and 6.58??m/s as measured with US, with a maximum absolute difference of 2.78??m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid-structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics. PMID:24407501

Campo, Adriaan; Soons, Joris; Heuten, Hilde; Ennekens, Guy; Goovaerts, Inge; Vrints, Christiaan; Lava, Pascal; Dirckx, Joris

2014-01-01

297

Dose and diagnostic image quality in digital tomosynthesis imaging of facial bones in pediatrics  

NASA Astrophysics Data System (ADS)

The purpose of this study was to evaluate the use of digital tomosynthesis (DT) for pediatric facial bone imaging. We compared the eye lens dose and diagnostic image quality of DT facial bone exams relative to digital radiography (DR) and computed tomography (CT), and investigated whether we could modify our current DT imaging protocol to reduce patient dose while maintaining sufficient diagnostic image quality. We measured the dose to the eye lens for all three modalities using high-sensitivity thermoluminescent dosimeters (TLDs) and an anthropomorphic skull phantom. To assess the diagnostic image quality of DT compared to the corresponding DR and CT images, we performed an observer study where the visibility of anatomical structures in the DT phantom images were rated on a four-point scale. We then acquired DT images at lower doses and had radiologists indicate whether the visibility of each structure was adequate for diagnostic purposes. For typical facial bone exams, we measured eye lens doses of 0.1-0.4 mGy for DR, 0.3-3.7 mGy for DT, and 26 mGy for CT. In general, facial bone structures were visualized better with DT then DR, and the majority of structures were visualized well enough to avoid the need for CT. DT imaging provides high quality diagnostic images of the facial bones while delivering significantly lower doses to the lens of the eye compared to CT. In addition, we found that by adjusting the imaging parameters, the DT effective dose can be reduced by up to 50% while maintaining sufficient image quality.

King, J. M.; Hickling, S.; Elbakri, I. A.; Reed, M.; Wrogemann, J.

2011-03-01

298

High-speed terahertz imaging toward food quality inspection.  

PubMed

In contrast to conventional x-ray food inspection systems that have difficulty in detecting low-density materials, a terahertz imaging system can even identify insects and plastics embedded in a food matrix. A reflection-mode continuous-wave terahertz imaging system was therefore developed for application to food quality inspection, which requires fast, compact, and low-cost detection. High-speed operation of the terahertz imaging system was achieved through the use of a beam-steering tool. A reasonable compromise between the spatial resolution and the scan length of an aspheric f-theta scanning lens could be achieved by optimizing the lens parameters. PMID:24663370

Ok, Gyeongsik; Park, Kisang; Kim, Hyun Jung; Chun, Hyang Sook; Choi, Sung-Wook

2014-03-01

299

Arterial elasticity imaging: comparison of finite-element analysis models with high-resolution ultrasound speckle tracking  

PubMed Central

Background The nonlinear mechanical properties of internal organs and tissues may be measured with unparalleled precision using ultrasound imaging with phase-sensitive speckle tracking. The many potential applications of this important noninvasive diagnostic approach include measurement of arterial stiffness, which is associated with numerous major disease processes. The accuracy of previous ultrasound measurements of arterial stiffness and vascular elasticity has been limited by the relatively low strain of nonlinear structures under normal physiologic pressure and the measurement assumption that the effect of the surrounding tissue modulus might be ignored in both physiologic and pressure equalized conditions. Methods This study performed high-resolution ultrasound imaging of the brachial artery in a healthy adult subject under normal physiologic pressure and the use of external pressure (pressure equalization) to increase strain. These ultrasound results were compared to measurements of arterial strain as determined by finite-element analysis models with and without a surrounding tissue, which was represented by homogenous material with fixed elastic modulus. Results Use of the pressure equalization technique during imaging resulted in average strain values of 26% and 18% at the top and sides, respectively, compared to 5% and 2%, at the top and sides, respectively, under physiologic pressure. In the artery model that included surrounding tissue, strain was 19% and 16% under pressure equalization versus 9% and 13% at the top and sides, respectively, under physiologic pressure. The model without surrounding tissue had slightly higher levels of strain under physiologic pressure compared to the other model, but the resulting strain values under pressure equalization were > 60% and did not correspond to experimental values. Conclusions Since pressure equalization may increase the dynamic range of strain imaging, the effect of the surrounding tissue on strain should be incorporated into models of arterial strain, particularly when the pressure equalization technique is used. PMID:20565833

2010-01-01

300

Tracking Navigation Imaging of Transcatheter Arterial Chemoembolization for Hepatocellular Carcinoma Using Three-Dimensional Cone-Beam CT Angiography  

PubMed Central

Purpose New tracking navigation imaging software was used to evaluate the usefulness of three dimensional (3D) CT angiography for transcatheter arterial chemoembolization (TACE) in patients with hepatocellular carcinoma (HCC). Materials and Methods Fifty-two patients with 73 HCCs were enrolled in this study retrospectively. Rotational angiography was performed from the hepatic artery for evaluation of the tumor feeding vessels. Arteries feeding the tumor were traced automatically by adjusting the region of interest around the targeted tumor on axial and coronal images using tracking navigation imaging with 3D cone-beam CT angiography. Results Using final selective angiographic findings as the gold standard, the detection of feeding vessels was 90.4% (66/73) for tracking navigation imaging and 50.7% (37/73) for celiac trunk angiography. This difference was statistically significant (Wilcoxon rank sum test, p < 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value for the detection of feeding arteries were 97.1% (66/68), 80.0% (4/5), 98.5% (66/67), and 66.7% (4/6), respectively. The kappa coefficient had a value of 0.638 (95% CI: 0.471-0.805), which is considered to indicate a good degree of agreement. With the assistance of tracking navigation imaging, the disease control rate of TACE for HCC was 67.3% (35/52) according to the modified Response Evaluation Criteria in Solid Tumors. During follow-up periods of 1-11 months, 10 patients (19.2%) remained cancer-free after TACE. Conclusion: Tracking navigation imaging with 3D cone-beam CT angiography should be useful for TACE in HCC patients with complicated feeding arteries. PMID:24804177

Minami, Yasunori; Yagyu, Yukinobu; Murakami, Takamichi; Kudo, Masatoshi

2014-01-01

301

Video quality assessment using objective parameters based on image segmentation  

Microsoft Academic Search

This work presents a methodology for video quality assessment using objective parameters based on image segmentation. Natural scenes are segmented into plane, edge and texture regions, and a set of objective parameters are assigned to each of these contexts. A perception-based model that predicts subjective ratings is defined by computing the relationship between objective measures and results of subjective assessment

A. C. F. Pessoa; A. X. Falcao; A. E. F. e Silva; R. M. Nishihara; R. A. Lotufo

1998-01-01

302

Biomarker, Imaging and Quality of Life Studies Funding Program  

Cancer.gov

Funded National Clinical Trials Network (NCTN) and Community Clinical Oncology Program (CCOP) Research Bases are invited to apply for funding to support biomarker, imaging, and quality of life studies with or without Cost-Effectiveness Analysis (CEA) proposals which are associated with NCI clinical trial concepts.

303

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

304

Arti cial Neural Network Visual Model for Image Quality Enhancement  

E-print Network

Arti cial Neural Network Visual Model for Image Quality Enhancement S. Chen y, Z He x and P and quadtree coding systems show that the proposed arti cial neural network visual model signi cantly enhances of Edinburgh, Edinburgh EH9 3JL, U.K. Abstract An arti cial neural network visual model is developed, which

Chen, Sheng

305

Aberrations of holographic lenses in image quality evaluation  

Microsoft Academic Search

The imaging quality of holographic lenses depends on parameters that include the shape of a holographic lens surface or an input pupil position. Based on the formulas for third-order aberration coefficients derived for such cases, conditions that ensure the correction of aperture and field aberrations are given. The possibility of joint correction of spherical aberration, coma, and astigmatism is discussed.

Boguslawa Dubik; Jan Masajada; Jerzy Nowak; Marek Zajac

1992-01-01

306

Helmet-mounted display image quality evaluation system  

Microsoft Academic Search

Helmet-mounted displays (HMDs) provide essential pilotage and fire control imagery information for pilots. To maintain system integrity and readiness, there is a need to develop an image quality evaluation system for HMDs. In earlier work, a framework was proposed for an HMD system called the integrated helmet and display sighting system (IHADSS), used with the U.S. Army's Apache helicopter. This

Sheng-Jen Hsieh; Clarence E. Rash; Thomas H. Harding; H. H. Beasley; John S. Martin

2003-01-01

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.

2012-03-01

308

Optoelectronic complex inner product for evaluating quality of image segmentation  

NASA Astrophysics Data System (ADS)

In automatic target recognition and machine vision applications, segmentation of the images is a key step. Poor segmentation reduces the recognition performance. For some imaging systems such as MRI and Synthetic Aperture Radar (SAR) it is difficult even for humans to agree on the location of the edge which allows for segmentation. A real- time dynamic approach to determine the quality of segmentation can enable vision systems to refocus of apply appropriate algorithms to ensure high quality segmentation for recognition. A recent approach to evaluate the quality of image segmentation uses percent-pixels-different (PPD). For some cases, PPD provides a reasonable quality evaluation, but it has a weakness in providing a measure for how well the shape of the segmentation matches the true shape. This paper introduces the complex inner product approach for providing a goodness measure for evaluating the segmentation quality based on shape. The complex inner product approach is demonstrated on SAR target chips obtained from the Moving and Stationary Target Acquisition and Recognition (MSTAR) program sponsored by the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory (AFRL). The results are compared to the PPD approach. A design for an optoelectronic implementation of the complex inner product for dynamic segmentation evaluation is introduced.

Power, Gregory J.; Awwal, Abdul Ahad S.

2000-11-01

309

SPY Imaging Assessment Correlates With Transesophageal Echocardiogram Assessment of Ventricular Function During Off-Pump Coronary Artery Bypass Grafting.  

PubMed

Intraoperative assessment of graft anastomoses is commonly performed after off-pump coronary artery bypass grafting (OPCAB). The SPY imaging system allows intraoperative graft assessment. We document correlation between intraoperative SPY images and wall motion abnormality by transesophageal echocardiogram (TEE) during OPCAB. A 79-year-old female underwent OPCAB. Intraoperative graft patency assessment was performed with the SPY and left ventricular wall motion was assessed by TEE. SPY imaging demonstrated poor flow trough the distal vein graft anastomosis to the posterior descending artery, which correlated with a new posterior wall motion hypokinesis. After graft revision, SPY imaging demonstrated good distal flow and the TEE demonstrated normalization of the left ventricular posterior wall motion. SPY technology allows the surgeon to accurately assess graft patency intraoperatively and allows immediate correction of a technical problem. PMID:22436858

Anderson, Curtis A; Kypson, Alan P; Hudson, Wes; Ferguson, Bruce; Rodriguez, Evelio

2008-05-01

310

Image quality and high contrast improvements on VLT/NACO  

E-print Network

NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ...

Girard, Julien H V; Mawet, Dimitri; Kasper, Markus; Zins, Gérard; Neichel, Benoît; Kolb, Johann; Christiaens, Valentin; Tourneboeuf, Martin; 10.1117/12.925660

2012-01-01

311

Subclinical Cerebral Complications After Coronary Artery Bypass Grafting: Prospective Analysis With Magnetic Resonance Imaging, Quantitative Electroencephalography, and Neuropsychological Assessment  

Microsoft Academic Search

Objective: To analyze the frequency and severity of sub- clinical cerebral complications associated with coro- nary artery bypass grafting (CABG). Design: A prospective controlled study using preopera- tive and postoperative magnetic resonance imaging (MRI) of the brain, quantitative electroencephalography (QEEG), and detailed neuropsychological and neurologic exami- nations as potentially sensitive indicators of subclinical cerebral injury associated with CABG.

Ritva Vanninen; Marja Aikia; Mervi Kononen; Kaarina Partanen; Harri Tulla; Paivi Hartikainen; Juhani Partanen; Hannu Manninen; Pentti Enberg; Mikko Hippelainen

1998-01-01

312

Techniques to evaluate the quality of medical images  

NASA Astrophysics Data System (ADS)

There is not a perfect agree in the definition of medical image quality from the physician and physicist point of view. The present conference analyzes the standard techniques used to grade image quality. In the first place, an analysis about how viewing conditions related to environment, monitor used or physician experience determines the subjective evaluation is done. After that, the physics point of view is analyzed including the advantage and disadvantage of the main published methods like: Quality Control Tests, Mathematical metrics, Modulation Transfer Function, Noise Power Spectrum, System Response Curve and Mathematical observers. Each method is exemplified with the results of updated papers. We concluded that the most successful methods up to the present have been those which include simulations of the Human Visual System. They have good correlation between the results of the objective metrics and the subjective evaluation made by the observers.

Perez-Diaz, Marlen

2014-11-01

313

Comparison of quality control software tools for diffusion tensor imaging.  

PubMed

Image quality of diffusion tensor imaging (DTI) is critical for image interpretation, diagnostic accuracy and efficiency. However, DTI is susceptible to numerous detrimental artifacts that may impair the reliability and validity of the obtained data. Although many quality control (QC) software tools are being developed and are widely used and each has its different tradeoffs, there is still no general agreement on an image quality control routine for DTIs, and the practical impact of these tradeoffs is not well studied. An objective comparison that identifies the pros and cons of each of the QC tools will be helpful for the users to make the best choice among tools for specific DTI applications. This study aims to quantitatively compare the effectiveness of three popular QC tools including DTI studio (Johns Hopkins University), DTIprep (University of North Carolina at Chapel Hill, University of Iowa and University of Utah) and TORTOISE (National Institute of Health). Both synthetic and in vivo human brain data were used to quantify adverse effects of major DTI artifacts to tensor calculation as well as the effectiveness of different QC tools in identifying and correcting these artifacts. The technical basis of each tool was discussed, and the ways in which particular techniques affect the output of each of the tools were analyzed. The different functions and I/O formats that three QC tools provide for building a general DTI processing pipeline and integration with other popular image processing tools were also discussed. PMID:25460331

Liu, Bilan; Zhu, Tong; Zhong, Jianhui

2015-04-01

314

Weighted perceptual difference model (case-PDM) for MR image quality evaluation  

Microsoft Academic Search

The perceptual difference model (Case-PDM) is being used to quantify image quality of fast, parallel MR acquisitions and reconstruction algorithms by comparing to slower, full k-space, high quality reference images. To date, most perceptual difference models average a single scalar image quality metric over a large region of interest. In this paper, we create an alternative metric weighted to image

Jun Miao; Wilbur C. K. Wong; David L. Wilson

2008-01-01

315

Use of low-dose contrast agent in cerebral angiography produces high-quality diagnostic images  

PubMed Central

The present study was aimed to study feasibility of low-dose contrast agent in cerebral CT angiography (CTA) to alleviate some side effects and costs associated with routine doses of contrast agent. Sixty patients suspected to have cerebral artery disease were randomly selected to receive either low-dose (60 mL) contrast agent or routine-dose (100 mL) contrast agent. CTA included transverse images, volume rendering (VR), and maximum intensity projection (MIP) images. Developing strength, image noise, and structure display effects of the cerebral artery were compared between groups. The developing strength and image noise of the cerebral artery were equivalent between groups (P > 0.05). No statistical differences were observed in structure display effects of the cerebral artery or in radiological diagnosis between groups (P > 0.05). Application of the low-dose contrast agent is feasible and offers comparable diagnostic capabilities in cerebral CT angiography. PMID:24995091

Zhou, Yang; Chen, Mu-Nan; Liu, Yang

2014-01-01

316

Segmentation of the common carotid artery with active shape models from 3D ultrasound images  

NASA Astrophysics Data System (ADS)

Carotid atherosclerosis is a major cause of stroke, a leading cause of death and disability. In this paper, we develop and evaluate a new segmentation method for outlining both lumen and adventitia (inner and outer walls) of common carotid artery (CCA) from three-dimensional ultrasound (3D US) images for carotid atherosclerosis diagnosis and evaluation. The data set consists of sixty-eight, 17× 2× 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80mg atorvastain and nine with placebo), who had carotid stenosis of 60% or more, at baseline and after three months of treatment. We investigate the use of Active Shape Models (ASMs) to segment CCA inner and outer walls after statin therapy. The proposed method was evaluated with respect to expert manually outlined boundaries as a surrogate for ground truth. For the lumen and adventitia segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC) of 93.6%+/- 2.6%, 91.8%+/- 3.5%, mean absolute distances (MAD) of 0.28+/- 0.17mm and 0.34 +/- 0.19mm, maximum absolute distances (MAXD) of 0.87 +/- 0.37mm and 0.74 +/- 0.49mm. The proposed algorithm took 4.4 +/- 0.6min to segment a single 3D US images, compared to 11.7+/-1.2min for manual segmentation. Therefore, the method would promote the translation of carotid 3D US to clinical care for the fast, safety and economical monitoring of the atherosclerotic disease progression and regression during therapy.

Yang, Xin; Jin, Jiaoying; He, Wanji; Yuchi, Ming; Ding, Mingyue

2012-03-01

317

Segmentation of common carotid artery with active appearance models from ultrasound images  

NASA Astrophysics Data System (ADS)

Carotid atherosclerosis is a major cause of stroke, a leading cause of death and disability. In this paper, a new segmentation method is proposed and evaluated for outlining the common carotid artery (CCA) from transverse view images, which were sliced from three-dimensional ultrasound (3D US) of 1mm inter-slice distance (ISD), to support the monitoring and assessment of carotid atherosclerosis. The data set consists of forty-eight 3D US images acquired from both left and right carotid arteries of twelve patients in two time points who had carotid stenosis of 60% or more at the baseline. The 3D US data were collected at baseline and three-month follow-up, where seven treated with 80mg atorvastatin and five with placebo. The baseline manual boundaries were used for Active Appearance Models (AAM) training; while the treatment data for segmentation testing and evaluation. The segmentation results were compared with experts manually outlined boundaries, as a surrogate for ground truth, for further evaluation. For the adventitia and lumen segmentations, the algorithm yielded Dice Coefficients (DC) of 92.06%+/-2.73% and 89.67%+/-3.66%, mean absolute distances (MAD) of 0.28+/-0.18 mm and 0.22+/-0.16 mm, maximum absolute distances (MAXD) of 0.71+/-0.28 mm and 0.59+/-0.21 mm, respectively. The segmentation results were also evaluated via Pratt's figure of merit (FOM) with the value of 0.61+/-0.06 and 0.66+/-0.05, which provides a quantitative measure for judging the similarity. Experimental results indicate that the proposed method can promote the carotid 3D US usage for a fast, safe and economical monitoring of the atherosclerotic disease progression and regression during therapy.

Yang, Xin; He, Wanji; Fenster, Aaron; Yuchi, Ming; Ding, Mingyue

2013-02-01

318

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

319

Seeing Red: A new imaging technique produces video-quality images of red blood  

E-print Network

diseases like cancer. To detect specific molecules or cancerous cells, MRI requires the patient to ingest laser light down to 100 nanometers, providing a way for scientists to see cells at work. Nano LaserSeeing Red: A new imaging technique produces video-quality images of red blood cells in living

Heller, Eric

320

Estimating static performance parameters of thermal imaging system based on image quality evaluation  

Microsoft Academic Search

Thermal imaging system is a kind of equipment that is widely used, its static performance parameters are always measured in library. The paper comes up with a new method to estimate the static performance parameters based on image quality evaluation, which can more easily and more quickly to compare performance of two instruments.

Chun-mei Xu; Yue-feng Wang; Wei Dong; Wei Zhang; Gang Li

2005-01-01

321

Deriving the Intrahepatic Arteriovenous Shunt Rate from CT Images and Biochemical Data Instead of from Arterial Perfusion Scintigraphy in Hepatic Arterial Infusion Chemotherapy  

SciTech Connect

The purpose of the present study was to elucidate a method for predicting the intrahepatic arteriovenous shunt rate from computed tomography (CT) images and biochemical data, instead of from arterial perfusion scintigraphy, because adverse exacerbated systemic effects may be induced in cases where a high shunt rate exists. CT and arterial perfusion scintigraphy were performed in patients with liver metastases from gastric or colorectal cancer. Biochemical data and tumor marker levels of 33 enrolled patients were measured. The results were statistically verified by multiple regression analysis. The total metastatic hepatic tumor volume (V{sub metastasized}), residual hepatic parenchyma volume (V{sub residual}; calculated from CT images), and biochemical data were treated as independent variables; the intrahepatic arteriovenous (IHAV) shunt rate (calculated from scintigraphy) was treated as a dependent variable. The IHAV shunt rate was 15.1 {+-} 11.9%. Based on the correlation matrixes, the best correlation coefficient of 0.84 was established between the IHAV shunt rate and V{sub metastasized} (p < 0.01). In the multiple regression analysis with the IHAV shunt rate as the dependent variable, the coefficient of determination (R{sup 2}) was 0.75, which was significant at the 0.1% level with two significant independent variables (V{sub metastasized} and V{sub residual}). The standardized regression coefficients ({beta}) of V{sub metastasized} and V{sub residual} were significant at the 0.1 and 5% levels, respectively. Based on this result, we can obtain a predicted value of IHAV shunt rate (p < 0.001) using CT images. When a high shunt rate was predicted, beneficial and consistent clinical monitoring can be initiated in, for example, hepatic arterial infusion chemotherapy.

Ozaki, Toshiro, E-mail: ganronbun@amail.plala.or.jp; Seki, Hiroshi; Shiina, Makoto [Niigata Cancer Center Hospital, Department of Radiology (Japan)

2009-09-15

322

Deriving the intrahepatic arteriovenous shunt rate from CT images and biochemical data instead of from arterial perfusion scintigraphy in hepatic arterial infusion chemotherapy.  

PubMed

The purpose of the present study was to elucidate a method for predicting the intrahepatic arteriovenous shunt rate from computed tomography (CT) images and biochemical data, instead of from arterial perfusion scintigraphy, because adverse exacerbated systemic effects may be induced in cases where a high shunt rate exists. CT and arterial perfusion scintigraphy were performed in patients with liver metastases from gastric or colorectal cancer. Biochemical data and tumor marker levels of 33 enrolled patients were measured. The results were statistically verified by multiple regression analysis. The total metastatic hepatic tumor volume (V(metastasized)), residual hepatic parenchyma volume (V(residual); calculated from CT images), and biochemical data were treated as independent variables; the intrahepatic arteriovenous (IHAV) shunt rate (calculated from scintigraphy) was treated as a dependent variable. The IHAV shunt rate was 15.1 +/- 11.9%. Based on the correlation matrixes, the best correlation coefficient of 0.84 was established between the IHAV shunt rate and V(metastasized) (p < 0.01). In the multiple regression analysis with the IHAV shunt rate as the dependent variable, the coefficient of determination (R (2)) was 0.75, which was significant at the 0.1% level with two significant independent variables (V(metastasized) and V(residual)). The standardized regression coefficients (beta) of V(metastasized) and V(residual) were significant at the 0.1 and 5% levels, respectively. Based on this result, we can obtain a predicted value of IHAV shunt rate (p < 0.001) using CT images. When a high shunt rate was predicted, beneficial and consistent clinical monitoring can be initiated in, for example, hepatic arterial infusion chemotherapy. PMID:19484290

Ozaki, Toshiro; Seki, Hiroshi; Shiina, Makoto

2009-09-01

323

Sociodemographic and clinical factors associated with low quality of life one year after coronary bypass operations: The Israeli Coronary Artery Bypass Study (ISCAB)  

Microsoft Academic Search

Objectives: We sought to examine the effect of sociodemographic characteristics and perioperative clinical factors 1 year after coronary bypass operations on low health-related quality of life. We also sought to assess the usefulness of an additional single question on overall health for identifying patients with low health-related quality of life. Methods: This report is part of the Israeli coronary artery

Elisheva Simchen; Noya Galai; Dalit Braun; Yana Zitser-Gurevich; Eti Shabtai; Irit Naveh

2001-01-01

324

Asymmetric radial expansion and contraction of rat carotid artery observed using a high-resolution ultrasound imaging system.  

PubMed

The geometry of carotid artery bifurcation is of high clinical interest because it determines the characteristics of blood flow that is closely related to the formation and development of atherosclerotic plaque. However, information on the dynamic changes in the vessel wall of carotid artery bifurcation during a pulsatile cycle is limited. This pilot study investigated the cyclic changes in carotid artery geometry caused by blood flow pulsation in rats. A high-resolution ultrasound imaging system with a broadband scanhead centered at 40 MHz was used to obtain longitudinal images of the rat carotid artery. A high frame rate retrospective B-scan imaging technique based on the use of electrocardiogram to trigger signal acquisition was used to examine precisely the fast arterial wall motion. Two-dimensional geometry data obtained from nine rats showed that the rat carotid artery asymmetrically contracts and dilates during each cardiac cycle. Systolic/diastolic vessel diameters near the upstream and downstream regions from the bifurcation were 0.976 ± 0.011/0.825 ± 0.015 mm and 0.766 ± 0.015/0.650 ± 0.016 mm, respectively. Their posterior/anterior wall displacement ratios in the radial direction were 41.0 ± 14.9% and 2.9 ± 1.6%, respectively. These results indicate that in the vicinity of bifurcation, the carotid artery favorably expands to the anterior side during the systolic phase. This phenomenon was observed to be more prominent in the downstream region near the bifurcation. The cyclic variation pattern in wall movement varies depending on the measurement site, which shows different patterns at far upstream and downstream of the bifurcation. The asymmetric radial expansion and contraction of the rat carotid artery observed in this study may be useful in studying the hemodynamic etiology of cardiovascular diseases because the pulsatile changes in vessel geometry may affect the local hemodynamics that determines the spatial distribution of wall shear stress, one of important cardiovascular risk factors. Further systematic study is needed to clarify the effects of wall elasticity, branch angle and vessel diameter ratio on the asymmetric wall motion of carotid artery bifurcation. PMID:23664377

Nam, Kweon-Ho; Bok, Tae-Hoon; Jin, Changzhu; Paeng, Dong-Guk

2014-01-01

325

IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 13, NO. 4, APRIL 2004 1 Image Quality Assessment: From Error Visibility to  

E-print Network

IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 13, NO. 4, APRIL 2004 1 Image Quality Assessment: From processing applications. First, it can be used to dynamically monitor and adjust image quality. For example concealment and post- filtering algorithms at the decoder. Third, it can be used to benchmark image processing

Simoncelli, Eero

326

The Effect of Image Data Compression on the Clinical Information Quality of Compressed Computed Tomography Images for Teleradiology Applications  

Microsoft Academic Search

Image communication systems for medical images have bandwidth and image size constraints that result in time-consuming transmission of uncompressed raw image data. Thus image compression plays vital role to reduce the bit rate for transmission or storage while maintaining an acceptable reproduction quality, but it is natural to rise the question of how much an image can be compressed and

S. E. Ghrare; M. A. M. Ali; M. Ismail

2008-01-01

327

Fundamental image quality limits for microcomputed tomography in small animals.  

PubMed

Small-animal imaging has become increasingly more important as transgenic and knockout mice are produced to model human diseases. One imaging technique that has emerged is microcomputed tomography (micro-CT). For live-animal imaging, the precision in the images will be determined by the x-ray dose given to the animal. As a result, we propose a simple method to predict the noise performance of an x-ray micro-CT system as a function of dose and image resolution. An ideal, quantum-noise limited micro-CT scanner, assumed to have perfect resolution and ideal efficiency, was modeled. Using a simplified model, the coefficient of variation (COV) of the linear attenuation coefficient was calculated for a range of entrance doses and isotropic voxel sizes. COV calculations were performed for the ideal case and with simulated imperfections in efficiency and resolution. Our model was validated in phantom studies and mouse images were acquired with a specimen scanner to illustrate the results. A simplified model of noise propagation in the case of isotropic resolution indicates that the COV in the linear attenuation coefficient is proportional to (dose)(-1/2) and to the (isotropic voxel size)(-2) in the reconstructed volume. Therefore an improvement in the precision can be achieved only by increasing the isotropic voxel size (thereby decreasing the resolution of the image) or by increasing the x-ray dose. For the ideal scanner, a COV of 1% in the linear attenuation coefficient for an image of a mouse exposed to 0.25 Gy is obtained with a minimum isotropic voxel size of 135 microm. However, the same COV is achieved at a dose of 5.0 Gy with a 65 microm isotropic voxel size. Conversely, for a 68 mm diameter rat, a COV of 1% obtained from an image at 5.0 Gy would require an isotropic voxel size of 100 microm. These results indicate that short-term, potentially lethal, effects of ionizing radiation will limit high-resolution live animal imaging. As improvements in detector technology allow the resolution to improve, by decreasing the detector element size to tens of microns or less, high quality images will be limited by the x-ray dose administered. For the highest quality images, these doses will approach the lethal dose or LD50 for the animals. Approaching the lethal dose will affect the way experiments are planned, and may reduce opportunities for experiments involving imaging the same animal over time. Dose considerations will become much more important for live small-animal imaging as the limits of resolution are tested. PMID:14655933

Ford, N L; Thornton, M M; Holdsworth, D W

2003-11-01

328

Post-traumatic Cavernosal Artery Pseudoaneurysm Presenting as Right Hip Pain: An Imaging Evaluation.  

PubMed

Pseudoaneurysm of the cavernosal artery is quite rare. Herein, we describe color Doppler findings of post-traumatic pseudoaneurysm of the right cavernosal artery in a 19-year-old adolescent boy who presented with right hip pain. Doppler showed turbulence of flow with arterial inflow and outflow from the aneurysm. Selective transarterial catheterization of the internal iliac and internal pudental artery with microcatheter and embolization of pseudoaneurysm using histocryl resulted in alleviation of symptoms. PMID:22530186

Govindarajan, Aarthi; Sai, P M Venkata; Anupama, C; Joseph, S Santosh

2012-01-01

329

A study of image quality for radar image processing. [synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

Methods developed for image quality metrics are reviewed with focus on basic interpretation or recognition elements including: tone or color; shape; pattern; size; shadow; texture; site; association or context; and resolution. Seven metrics are believed to show promise as a way of characterizing the quality of an image: (1) the dynamic range of intensities in the displayed image; (2) the system signal-to-noise ratio; (3) the system spatial bandwidth or bandpass; (4) the system resolution or acutance; (5) the normalized-mean-square-error as a measure of geometric fidelity; (6) the perceptual mean square error; and (7) the radar threshold quality factor. Selective levels of degradation are being applied to simulated synthetic radar images to test the validity of these metrics.

King, R. W.; Kaupp, V. H.; Waite, W. P.; Macdonald, H. C.

1982-01-01

330

Arterial embolism  

PubMed Central

Surgical and intensive care patients are at a heightened risk for arterial embolization due to pre-existing conditions such as age, hypercoagulability, cardiac abnormalities and atherosclerotic disease. Most arterial emboli are clots that originate in the heart and travel to distant vascular beds where they cause arterial occlusion, ischemia, and potentially infarction. Other emboli form on the surface of eroded arterial plaque or within its lipid core. Thromboemboli are large clots that dislodge from the surface of athesclerotic lesions and occlude distal arteries causing immediate ischemia. Atheroemboli, which originate from fracturing the lipid core tend to cause a process of organ dysfunction and systemic inflammation, termed cholesterol embolization syndrome. The presentation of arterial emboli depends on the arterial bed that is affected. The most common manifestations are strokes and acute lower limb ischemia. Less frequently, emboli target the upper extremities, mesenteric or renal arteries. Treatment involves rapid diagnosis, which may be aided by precise imaging studies and restoration of blood flow. The type of emboli, duration of presentation, and organ system affected determines the treatment course. Long-term therapy includes supportive medical care, identification of the source of embolism and prevention of additional emboli. Patients who experienced arterial embolism as a result of clots formed in the heart should be anticoagulated. Arterial emboli from atherosclerotic disease of the aorta or other large arteries should prompt treatment to reduce the risk for atherosclerotic progression, such as anti-platelet therapy and the use of statin drugs. The use of anticoagulation and surgical intervention to reduce the risk of arterial embolization from atherosclerotic lesions is still being studied. PMID:23724391

Lyaker, Michael R.; Tulman, David B.; Dimitrova, Galina T.; Pin, Richard H.; Papadimos, Thomas J.

2013-01-01

331

Preparation of primary cultured mesenteric artery smooth muscle cells for fluorescent imaging and physiological studies  

Microsoft Academic Search

In this protocol, we describe a method for isolation and culture of smooth muscle cells derived from the adult rat (or mouse) superior mesenteric artery. Arterial myocytes are obtained by enzymatic dissociation and established in primary culture. The cultured cells retain expression of smooth muscle-specific ?-actin and physiological responses to agonists. Cultured arterial myocytes (prepared from wild-type or transgenic animals)

Mordecai P Blaustein; Vera A Golovina

2007-01-01

332

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

2009-07-01

333

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

334

Method for laser disturbing image quality evaluation based on wavelet weight and correlation  

Microsoft Academic Search

The advantages and disadvantages of conventional image quality evaluation methods are analyzed and according to the characteristics of laser disturbing image, an image quality evaluation method which is based on wavelet weight and correlation is established. In the method, both the original and disturbed images are processed by wavelet decomposition, replacement and reconstruction. Then different sub-band images are obtained and

Yin Xu; Xiao-Quan Sun; Zuo-Lai Wang

2010-01-01

335

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.

336

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

2012-12-01

337

Clinical Decision Making With Myocardial Perfusion Imaging in Patients With Known or Suspected Coronary Artery Disease  

PubMed Central

Myocardial perfusion imaging (MPI) to diagnose coronary artery disease (CAD) is best performed in patients with intermediate pretest likelihood of disease; unfortunately, pretest likelihood is often overestimated, resulting in the inappropriate use of perfusion imaging. A good functional capacity often predicts low risk, and MPI for diagnosing CAD should be reserved for individuals with poor exercise capacity, abnormal resting electrocardiography, or an intermediate or high probability of CAD. With respect to anatomy-based testing, coronary CT angiography has a good negative predictive value, but stenosis severity correlates poorly with ischemia. Therefore decision making with respect to revascularization may be limited when a purely noninvasive anatomical test is used. Regarding perfusion imaging, the diagnostic accuracies of SPECT, PET, and cardiac magnetic resonance are similar, though fewer studies are available with cardiac magnetic resonance. PET coronary flow reserve may offer a negative predictive value sufficiently high to exclude severe CAD such that patients with mild to moderate reversible perfusion defects can forego invasive angiography. In addition, combined anatomical and perfusion-based imaging may eventually offer a definitive evaluation for diagnosing CAD, even in higher risk patients. Any remarkable findings on single-photon emission computed tomography and PET MPI studies are valuable for prognostication. Furthermore, assessment of myocardial blood flow with PET is particularly powerful for prognostication as it reflects the end result of many processes that lead to atherosclerosis. Decision making with respect to revascularization is limited for cardiac MRI and PET MPI. In contrast, retrospective radionuclide studies have identified an ischemic threshold, but randomized trials are needed. In patients with at least moderately reduced left ventricular systolic function, viable myocardium as assessed by PET or MRI, appears to identify patients who benefit from revascularization, but well-executed randomized trials are lacking. PMID:24948154

Cremer, Paul; Hachamovitch, Rory; Tamarappoo, Balaji

2015-01-01

338

Intravascular near-infrared fluorescence molecular imaging of atherosclerosis: toward coronary arterial visualization of biologically high-risk plaques  

NASA Astrophysics Data System (ADS)

New imaging methods are urgently needed to identify high-risk atherosclerotic lesions prior to the onset of myocardial infarction, stroke, and ischemic limbs. Molecular imaging offers a new approach to visualize key biological features that characterize high-risk plaques associated with cardiovascular events. While substantial progress has been realized in clinical molecular imaging of plaques in larger arterial vessels (carotid, aorta, iliac), there remains a compelling, unmet need to develop molecular imaging strategies targeted to high-risk plaques in human coronary arteries. We present recent developments in intravascular near-IR fluorescence catheter-based strategies for in vivo detection of plaque inflammation in coronary-sized arteries. In particular, the biological, light transmission, imaging agent, and engineering principles that underlie a new intravascular near-IR fluorescence sensing method are discussed. Intravascular near-IR fluorescence catheters appear highly translatable to the cardiac catheterization laboratory, and thus may offer a new in vivo method to detect high-risk coronary plaques and to assess novel atherosclerosis biologics.

Calfon, Marcella A.; Vinegoni, Claudio; Ntziachristos, Vasilis; Jaffer, Farouc A.

2010-01-01

339

Quality of traffic flow on urban arterial streets and its relationship with safety  

Microsoft Academic Search

The two-fluid model for vehicular traffic flow explains the traffic on arterials as a mix of stopped and running vehicles. It describes the relationship between the vehicles’ running speed and the fraction of running vehicles. The two parameters of the model essentially represent ‘free flow’ travel time and level of interaction among vehicles, and may be used to evaluate urban

Vinayak V. Dixit; Anurag Pande; Mohamed Abdel-Aty; Abhishek Das; Essam Radwan

2011-01-01

340

A quality assurance program for image quality of cone-beam CT guidance in radiation therapy  

SciTech Connect

The clinical introduction of volumetric x-ray image-guided radiotherapy systems necessitates formal commissioning of the hardware and image-guided processes to be used and drafts quality assurance (QA) for both hardware and processes. Satisfying both requirements provides confidence on the system's ability to manage geometric variations in patient setup and internal organ motion. As these systems become a routine clinical modality, the authors present data from their QA program tracking the image quality performance of ten volumetric systems over a period of 3 years. These data are subsequently used to establish evidence-based tolerances for a QA program. The volumetric imaging systems used in this work combines a linear accelerator with conventional x-ray tube and an amorphous silicon flat-panel detector mounted orthogonally from the accelerator central beam axis, in a cone-beam computed tomography (CBCT) configuration. In the spirit of the AAPM Report No. 74, the present work presents the image quality portion of their QA program; the aspects of the QA protocol addressing imaging geometry have been presented elsewhere. Specifically, the authors are presenting data demonstrating the high linearity of CT numbers, the uniformity of axial reconstructions, and the high contrast spatial resolution of ten CBCT systems (1-2 mm) from two commercial vendors. They are also presenting data accumulated over the period of several months demonstrating the long-term stability of the flat-panel detector and of the distances measured on reconstructed volumetric images. Their tests demonstrate that each specific CBCT system has unique performance. In addition, scattered x rays are shown to influence the imaging performance in terms of spatial resolution, axial reconstruction uniformity, and the linearity of CT numbers.

Bissonnette, Jean-Pierre; Moseley, Douglas J.; Jaffray, David A. [Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada)

2008-05-15

341

Performance evaluation of objective quality metrics for HDR image compression  

NASA Astrophysics Data System (ADS)

Due to the much larger luminance and contrast characteristics of high dynamic range (HDR) images, well-known objective quality metrics, widely used for the assessment of low dynamic range (LDR) content, cannot be directly applied to HDR images in order to predict their perceptual fidelity. To overcome this limitation, advanced fidelity metrics, such as the HDR-VDP, have been proposed to accurately predict visually significant differences. However, their complex calibration may make them difficult to use in practice. A simpler approach consists in computing arithmetic or structural fidelity metrics, such as PSNR and SSIM, on perceptually encoded luminance values but the performance of quality prediction in this case has not been clearly studied. In this paper, we aim at providing a better comprehension of the limits and the potentialities of this approach, by means of a subjective study. We compare the performance of HDR-VDP to that of PSNR and SSIM computed on perceptually encoded luminance values, when considering compressed HDR images. Our results show that these simpler metrics can be effectively employed to assess image fidelity for applications such as HDR image compression.

Valenzise, Giuseppe; De Simone, Francesca; Lauga, Paul; Dufaux, Frederic

2014-09-01

342

Novel MOS prediction models for compressed medical image quality.  

PubMed

This paper presents the development of novel models which can be potentially useful in determining the upper limit of image compression thresholds, to preserve diagnostically relevant information in compressed medical images. These models were developed by evolving the correlation between the theoretically computed objective (peak signal-to-noise ratio and structural similarity) and subjective mean opinion score (MOS) quality parameters. The developed models were validated by comparing the model generated MOS with the corresponding experimental MOS of six independent observers considering joint photographic experts group (JPEG), JPEG2000 and set partitioning in hierarchical trees (SPIHT) compressions of computed tomography (CT) scan images. It is found that the correlation between the model generated and experimental MOS and PRD are ?0.87 and ?13% respectively for the compression range 0.05-2.0 bits/pixel of the CT scan images. Therefore our models can be potentially useful for observer-independent MOS prediction and quality assessment of reconstructed medical images. In addition this also avoids the need for exhaustive and time-consuming experimental MOS and thus it can be more suitable for teleradiology applications. PMID:21401314

Kumar, B; Singh, S P; Mohan, A; Anand, A

2011-01-01

343

Clinical study in phase- contrast mammography: image-quality analysis.  

PubMed

The first clinical study of phase-contrast mammography (PCM) with synchrotron radiation was carried out at the Synchrotron Radiation for Medical Physics beamline of the Elettra synchrotron radiation facility in Trieste (Italy) in 2006-2009. The study involved 71 patients with unresolved breast abnormalities after conventional digital mammography and ultrasonography exams carried out at the Radiology Department of Trieste University Hospital. These cases were referred for mammography at the synchrotron radiation facility, with images acquired using a propagation-based phase-contrast imaging technique. To investigate the contribution of phase-contrast effects to the image quality, two experienced radiologists specialized in mammography assessed the visibility of breast abnormalities and of breast glandular structures. The images acquired at the hospital and at the synchrotron radiation facility were compared and graded according to a relative seven-grade visual scoring system. The statistical analysis highlighted that PCM with synchrotron radiation depicts normal structures and abnormal findings with higher image quality with respect to conventional digital mammography. PMID:24470410

Longo, Renata; Tonutti, Maura; Rigon, Luigi; Arfelli, Fulvia; Dreossi, Diego; Quai, Elisa; Zanconati, Fabrizio; Castelli, Edoardo; Tromba, Giuliana; Cova, Maria A

2014-03-01

344

Quality assessment of butter cookies applying multispectral imaging.  

PubMed

A method for characterization of butter cookie quality by assessing the surface browning and water content using multispectral images is presented. Based on evaluations of the browning of butter cookies, cookies were manually divided into groups. From this categorization, reference values were calculated for a statistical prediction model correlating multispectral images with a browning score. The browning score is calculated as a function of oven temperature and baking time. It is presented as a quadratic response surface. The investigated process window was the intervals 4-16 min and 160-200°C in a forced convection electrically heated oven. In addition to the browning score, a model for predicting the average water content based on the same images is presented. This shows how multispectral images of butter cookies may be used for the assessment of different quality parameters. Statistical analysis showed that the most significant wavelengths for browning predictions were in the interval 400-700 nm and the wavelengths significant for water prediction were primarily located in the near-infrared spectrum. The water prediction model was found to correctly estimate the average water content with an absolute error of 0.22%. From the images it was also possible to follow the browning and drying propagation from the cookie edge toward the center. PMID:24804036

Andresen, Mette S; Dissing, Bjørn S; Løje, Hanne

2013-07-01

345

Quality assessment of butter cookies applying multispectral imaging  

PubMed Central

A method for characterization of butter cookie quality by assessing the surface browning and water content using multispectral images is presented. Based on evaluations of the browning of butter cookies, cookies were manually divided into groups. From this categorization, reference values were calculated for a statistical prediction model correlating multispectral images with a browning score. The browning score is calculated as a function of oven temperature and baking time. It is presented as a quadratic response surface. The investigated process window was the intervals 4–16 min and 160–200°C in a forced convection electrically heated oven. In addition to the browning score, a model for predicting the average water content based on the same images is presented. This shows how multispectral images of butter cookies may be used for the assessment of different quality parameters. Statistical analysis showed that the most significant wavelengths for browning predictions were in the interval 400–700 nm and the wavelengths significant for water prediction were primarily located in the near-infrared spectrum. The water prediction model was found to correctly estimate the average water content with an absolute error of 0.22%. From the images it was also possible to follow the browning and drying propagation from the cookie edge toward the center. PMID:24804036

Andresen, Mette S; Dissing, Bjørn S; Løje, Hanne

2013-01-01

346

Magnetic Resonance Imaging (MRI) Analysis of Fibroid Location in Women Achieving Pregnancy After Uterine Artery Embolization  

SciTech Connect

The purpose of this study was to evaluate the fibroid morphology in a cohort of women achieving pregnancy following treatment with uterine artery embolization (UAE) for symptomatic uterine fibroids. A retrospective review of magnetic resonance imaging (MRI) of the uterus was performed to assess pre-embolization fibroid morphology. Data were collected on fibroid size, type, and number and included analysis of follow-up imaging to assess response. There have been 67 pregnancies in 51 women, with 40 live births. Intramural fibroids were seen in 62.7% of the women (32/48). Of these the fibroids were multiple in 16. A further 12 women had submucosal fibroids, with equal numbers of types 1 and 2. Two of these women had coexistent intramural fibroids. In six women the fibroids could not be individually delineated and formed a complex mass. All subtypes of fibroid were represented in those subgroups of women achieving a live birth versus those who did not. These results demonstrate that the location of uterine fibroids did not adversely affect subsequent pregnancy in the patient population investigated. Although this is only a small qualitative study, it does suggest that all types of fibroids treated with UAE have the potential for future fertility.

Walker, Woodruff J. [Royal Surrey County Hospital, Department of Radiology (United Kingdom); Bratby, Mark John [St George's Hospital, Department of Radiology (United Kingdom)], E-mail: markbratby@doctors.org.uk

2007-09-15

347

Assessment of Carotid Artery Atherosclerotic Disease by Using Three-dimensional Fast Black-Blood MR Imaging: Comparison with DSA.  

PubMed

Purpose To assess fast three-dimensional (3D) black-blood (BB) magnetic resonance (MR) imaging as a noninvasive alternative to intraarterial digital subtraction angiography (DSA) at quantifying moderate to severe carotid artery atherosclerotic disease. Materials and Methods Local ethics committee approval and written informed patient consent were obtained for this study. Sixty-five carotid arteries from 52 patients with at least 50% stenosis underwent 3D BB MR imaging and DSA. Quantitative measurements, including stenosis, lesion length, and the presence or absence of plaque ulceration, obtained with the two modalities were independently determined. Sensitivity and specificity, the intraclass correlation coefficient (ICC), Cohen ?, and Bland-Altman analysis were used to assess the agreement. Results Excellent agreement in measuring luminal stenosis was found between 3D BB MR imaging and DSA (ICC, 0.96; 95% confidence interval [CI]: 0.93, 0.97). Three-dimensional BB MR imaging was also found to have high sensitivity (91.7%), specificity (96.2%), and agreement (Cohen ?, 0.85; 95% CI: 0.66, 0.99) with DSA for detection of ulcers. Good agreement was found between lesion length measured by using 3D BB MR imaging and DSA (ICC, 0.75; 95% CI: 0.51, 0.84). However, lesion length measurements by using 3D BB MR imaging were, on average, 4.0 mm longer than those measured by using DSA (P < .001). Conclusion Three-dimensional BB MR imaging is a noninvasive and accurate way to quantify moderate to severe carotid artery atherosclerotic disease. With fast acquisition and large coverage, 3D BB MR imaging has the potential to become an alternative imaging approach in evaluating the severity of atherosclerosis. © RSNA, 2014. PMID:25286322

Zhao, Huilin; Wang, Jinnan; Liu, Xiaosheng; Zhao, Xihai; Hippe, Daniel S; Cao, Ye; Wan, Jieqing; Yuan, Chun; Xu, Jianrong

2015-02-01

348

Automated coronary artery calcification detection on low-dose chest CT images  

NASA Astrophysics Data System (ADS)

Coronary artery calcification (CAC) measurement from low-dose CT images can be used to assess the risk of coronary artery disease. A fully automatic algorithm to detect and measure CAC from low-dose non-contrast, non-ECG-gated chest CT scans is presented. Based on the automatically detected CAC, the Agatston score (AS), mass score and volume score were computed. These were compared with scores obtained manually from standard-dose ECG-gated scans and low-dose un-gated scans of the same patient. The automatic algorithm segments the heart region based on other pre-segmented organs to provide a coronary region mask. The mitral valve and aortic valve calcification is identified and excluded. All remaining voxels greater than 180HU within the mask region are considered as CAC candidates. The heart segmentation algorithm was evaluated on 400 non-contrast cases with both low-dose and regular dose CT scans. By visual inspection, 371 (92.8%) of the segmentations were acceptable. The automated CAC detection algorithm was evaluated on 41 low-dose non-contrast CT scans. Manual markings were performed on both low-dose and standard-dose scans for these cases. Using linear regression, the correlation of the automatic AS with the standard-dose manual scores was 0.86; with the low-dose manual scores the correlation was 0.91. Standard risk categories were also computed. The automated method risk category agreed with manual markings of gated scans for 24 cases while 15 cases were 1 category off. For low-dose scans, the automatic method agreed with 33 cases while 7 cases were 1 category off.

Xie, Yiting; Cham, Matthew D.; Henschke, Claudia; Yankelevitz, David; Reeves, Anthony P.

2014-03-01

349

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

2011-09-01

350

Image Quality and Performance of the LSST Camera  

NASA Astrophysics Data System (ADS)

The LSST camera, which will be the largest digital camera built to date, presents a number of novel challenges. The field of view will be 3.5 degrees in diameter and will be sampled by a 3.2 billion pixel array of sensors to be read-out in under 2 seconds, which leads to demanding constraints on the sensor architecture and read-out electronics. The camera also incorporates three large refractive lenses, an array of five wide-band large filters mounted on a carousel, and a mechanical shutter. Given the fast optical beam (f/1.2) and tight tolerances for image quality and throughput specifications, the requirements on the optical design, assembly and alignment, and contamination control of the optical elements and focal plane are crucial. We present an overview of the LSST camera, with an emphasis on models of camera image quality and throughput performance that are characterized by various analysis packages and design considerations.

Gilmore, D. Kirk; Kahn, S.; Rassmussen, A.; Singel, J.

2012-01-01

351

[Imaging characteristics of two-dimensional spin echo T?-weighted image in carotid artery plaque].  

PubMed

Recently, T? weighted image (T?WI) has proven to be useful for diagnosing carotid plaque. This time, the image parameter of two-dimensional spin echo (2D SE) T?WI was examined. Phantoms that imitated muscle and carotid plaque were made. Signal noise ratio (SNR) and the contrast of phantoms were examined when the flip angle (FA) of radio frequency (RF) pulse, repetition time (TR), and echo train length (ETL) was changed. A visual evaluation was done in a clinical case. Both SE and fast spin echo (FSE) SNR improved according to the extension of TR, and the contrast decreased. Moreover, the contrast improved when there was a lot of ETL and the FA of RF pulse. It is thought that this is because SNR and the contrast depend on the interrelation of TR, T? value, and the FA of RF pulse. When the FA of RF pulse was set to 70 degrees and the TR was set to 400 ms resulting from the phantom experiment, clinical cases obtained great results. This examination confirmed the utility of 2D SE in carotid plaque inspection. PMID:22277819

Naka, Takanori; Sasaki, Yuuya; Kawaguchi, Seigo; Fujita, Mayumi; Takeda, Miho; Umezawa, Syuuichi; Tomiyama, Takeaki

2012-01-01

352

Image quality evaluation with a new phase rotation beamformer  

Microsoft Academic Search

Over the last few decades, dynamic focusing based on digital receive beamforming (DRBF) has led to significant improvements in image quality. However, it is computationally very demanding due to its requirement for multiple lowpass filters (e.g., a complex filter for each receive channel in quadrature demodulation-based phase rotation beamform- ers (QD-PRBF)). We recently developed a novel phase rotation beamformer with

Anup Agarwal; Fabio Kurt Schneider; Yang Mo Yoo; Yongmin Kim

2008-01-01

353

Verification of quality parameters for portal images in radiotherapy  

PubMed Central

Background The purpose of the study was to verify different values of quality parameters of portal images in radiotherapy. Materials and methods We investigated image qualities of different field verification systems. Four EPIDs (Siemens OptiVue500aSi®, Siemens BeamView Plus®, Elekta iView® and Varian PortalVision™) were investigated with the PTW EPID QC PHANTOM® and compared with two portal film systems (Kodak X-OMAT® cassette with Kodak X-OMAT V® film and Kodak EC-L Lightweight® cassette with Kodak Portal Localisation ReadyPack® film). Results A comparison of the f50 and f25 values of the modulation transfer functions (MTFs) belonging to each of the systems revealed that the amorphous silicon EPIDs provided a slightly better high contrast resolution than the Kodak Portal Localisation ReadyPack® film with the EC-L Lightweight® cassette. The Kodak X-OMAT V® film gave a poor low contrast resolution: from the existing 27 holes only 9 were detectable. Conclusions On the base of physical characteristics, measured in this work, the authors suggest the use of amorphous-silicon EPIDs producing the best image quality. Parameters of the EPIDs with scanning liquid ionisation chamber (SLIC) were very stable. The disadvantage of older versions of EPIDs like SLIC and VEPID is a poor DICOM implementation, and the modulation transfer function (MTF) values (f50 and f25) are less than that of aSi detectors. PMID:22933938

Pesznyák, Csilla; Polgár, István; Weisz, Csaba; Király, Réka; Zaránd, Pál

2011-01-01

354

Radiometric Quality Evaluation of INSAT-3D Imager Data  

NASA Astrophysics Data System (ADS)

INSAT-3D is an advanced meteorological satellite of ISRO which acquires imagery in optical and infra-red (IR) channels for study of weather dynamics in Indian sub-continent region. In this paper, methodology of radiometric quality evaluation for Level-1 products of Imager, one of the payloads onboard INSAT-3D, is described. Firstly, overall visual quality of scene in terms of dynamic range, edge sharpness or modulation transfer function (MTF), presence of striping and other image artefacts is computed. Uniform targets in Desert and Sea region are identified for which detailed radiometric performance evaluation for IR channels is carried out. Mean brightness temperature (BT) of targets is computed and validated with independently generated radiometric references. Further, diurnal/seasonal trends in target BT values and radiometric uncertainty or sensor noise are studied. Results of radiometric quality evaluation over duration of eight months (January to August 2014) and comparison of radiometric consistency pre/post yaw flip of satellite are presented. Radiometric Analysis indicates that INSAT-3D images have high contrast (MTF > 0.2) and low striping effects. A bias of <4K is observed in the brightness temperature values of TIR-1 channel measured during January-August 2014 indicating consistent radiometric calibration. Diurnal and seasonal analysis shows that Noise equivalent differential temperature (NEdT) for IR channels is consistent and well within specifications.

Prakash, S.; Jindal, D.; Badal, N.; Kartikeyan, B.; Gopala Krishna, B.

2014-11-01

355

Spectral CT imaging in patients with Budd-Chiari syndrome: investigation of image quality.  

PubMed

To assess the image quality of monochromatic imaging from spectral CT in patients with Budd-Chiari syndrome (BCS), fifty patients with BCS underwent spectral CT to generate conventional 140 kVp polychromatic images (group A) and monochromatic images, with energy levels from 40 to 80, 40 + 70, and 50 + 70 keV fusion images (group B) during the portal venous phase (PVP) and the hepatic venous phase (HVP). Two-sample t tests compared vessel-to-liver contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) for the portal vein (PV), hepatic vein (HV), inferior vena cava. Readers' subjective evaluations of the image quality were recorded. The highest SNR values in group B were distributed at 50 keV; the highest CNR values in group B were distributed at 40 keV. The higher CNR values and SNR values were obtained though PVP of PV (SNR 18.39 ± 6.13 vs. 10.56 ± 3.31, CNR 7.81 ± 3.40 vs. 3.58 ± 1.31) and HVP of HV (3.89 ± 2.08 vs. 1.27 ± 1.55) in the group B; the lower image noise for group B was at 70 keV and 50 + 70 keV (15.54 ± 8.39 vs. 18.40 ± 4.97, P = 0.0004 and 18.97 ± 7.61 vs. 18.40 ± 4.97, P = 0.0691); the results show that the 50 + 70 keV fusion image quality was better than that in group A. Monochromatic energy levels of 40-70, 40 + 70, and 50 + 70 keV fusion image can increase vascular contrast and that will be helpful for the diagnosis of BCS, we select the 50 + 70 keV fusion image to acquire the best BCS images. PMID:24833430

Su, Lei; Dong, Junqiang; Sun, Qiang; Liu, Jie; Lv, Peijie; Hu, Lili; Yan, Liangliang; Gao, Jianbo

2014-11-01

356

Flurpiridaz F 18 PET: Phase II Safety and Clinical Comparison with SPECT Myocardial Perfusion Imaging for Detection of Coronary Artery Disease  

PubMed Central

Objectives Phase II trial to assess flurpiridaz F 18 for safety and compare its diagnostic performance for PET myocardial perfusion imaging (MPI) to Tc-99m SPECT-MPI regarding image quality, interpretative certainty, defect magnitude and detection of coronary artery disease (CAD)(? 50% stenosis) on invasive coronary angiography (ICA). Background In preclinical and phase I studies, flurpiridaz F 18 has shown characteristics of an essentially ideal MPI tracer. Methods 143 patients from 21 centers underwent rest-stress PET and Tc-99m SPECT-MPI. Eighty-six patients underwent ICA, and 39 had low-likelihood of CAD. Images were scored by 3 independent, blinded readers. Results A higher % of images were rated as excellent/good on PET vs. SPECT on stress (99.2% vs. 88.5%, p<0.01) and rest (96.9% vs. 66.4, p<0.01) images. Diagnostic certainty of interpretation (% cases with definitely abnormal/normal interpretation) was higher for PET vs. SPECT (90.8% vs. 70.9%, p<0.01). In 86 patients who underwent ICA, sensitivity of PET was higher than SPECT [78.8% vs. 61.5%, respectively (p=0.02)]. Specificity was not significantly different (PET:76.5% vs. SPECT:73.5%). Receiver operating characteristic curve area was 0.82±0.05 for PET and 0.70±0.06 for SPECT (p=0.04). Normalcy rate was 89.7% with PET and 97.4% with SPECT (p=NS). In patients with CAD on ICA, the magnitude of reversible defects was greater with PET than SPECT (p=0.008). Extensive safety assessment revealed that flurpiridaz F 18 was safe in this cohort. Conclusions In this Phase 2 trial, PET MPI using flurpiridaz F 18 was safe and superior to SPECT MPI for image quality, interpretative certainty, and overall CAD diagnosis. PMID:23265345

Berman, Daniel S.; Maddahi, Jamshid; Tamarappoo, B. K.; Czernin, Johannes; Taillefer, Raymond; Udelson, James E.; Gibson, C. Michael; Devine, Marybeth; Lazewatsky, Joel; Bhat, Gajanan; Washburn, Dana

2015-01-01

357

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

358

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

359

Testing of new models of the human visual system for image quality evaluation  

Microsoft Academic Search

This article deals with evaluation of image quality by various methods and comparison of their results. Generally, there are several ways how to assess image quality. Three main approaches are: subjective testing, objective testing and image quality evaluation using a human visual system model (HVS). The subjective testing is based on human perception, the objective testing on a mathematical computing

J. Dusek; K. Roubik

2003-01-01

360

Modeling and validation of a psychovisually based image quality evaluator for DCT-based compression  

Microsoft Academic Search

In this paper, we propose an algorithm for evaluating the quality of JPEG compressed images, called the psychovisually based image quality evaluator (PIQE), which measures the severity of artifacts produced by JPEG compression. The PIQE evaluates the image quality using two psychovisually based fidelity criteria: blockiness and similarity. The blockiness is an index that measures the patterned square artifact created

Ruby Wai-Shan Chan; Peter Goldsmith

2002-01-01

361

Image gathering and digital restoration for fidelity and visual quality  

NASA Technical Reports Server (NTRS)

The fidelity and resolution of the traditional Wiener restorations given in the prevalent digital processing literature can be significantly improved when the transformations between the continuous and discrete representations in image gathering and display are accounted for. However, the visual quality of these improved restorations also is more sensitive to the defects caused by aliasing artifacts, colored noise, and ringing near sharp edges. In this paper, these visual defects are characterized, and methods for suppressing them are presented. It is demonstrated how the visual quality of fidelity-maximized images can be improved when (1) the image-gathering system is specifically designed to enhance the performance of the image-restoration algorithm, and (2) the Wiener filter is combined with interactive Gaussian smoothing, synthetic high edge enhancement, and nonlinear tone-scale transformation. The nonlinear transformation is used primarily to enhance the spatial details that are often obscurred when the normally wide dynamic range of natural radiance fields is compressed into the relatively narrow dynamic range of film and other displays.

Huck, Friedrich O.; Alter-Gartenberg, Rachel; Rahman, Zia-Ur

1991-01-01

362

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

363

IEEE TRANSACTIONS ON MEDICAL IMAGING ---FINAL MANUSCRIPT 20040117 1 Interactive Virtual Endoscopy in Coronary Arteries  

E-print Network

in Coronary Arteries based on Multi­Modality Fusion Andreas Wahle, # Senior Member, IEEE, Mark E. Olszewski­independent virtual endoscopy in human coronary arteries is presented in this pa­ per. It incorporates previously results in a three­ or four­dimensional (3­D/4­D) model of a coronary artery, specifically of its lumen

Wahle, Andreas

364

Image quality evaluation of the angiography imaging system at the European synchrotron radiation facility  

Microsoft Academic Search

The evaluation of the image quality of the angiography imaging system used at the Medical Beamline of European Synchrotron Radiation Facility (ESRF) is presented. A two-line 432-pixel germanium detector is utilized in the human coronary angiography program. The performances have been measured with two monochromatic beams, with energies above and below the iodine K-edge. The large-area transfer characteristics (response curve),

A. Peterzol; A. Bravin; P. Coan; H. Elleaume

2003-01-01

365

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

366

Image quality evaluation of a direct digital radiography detector operating in a UK radiology department  

Microsoft Academic Search

This paper presents results of an image quality evaluation performed on a prototype DirectRay system (Sterling Diagnostic Imaging, Direct Radiography Corp.) operating in a UK radiology department. Physical imaging characteristics measured included characteristic (sensitometric) response, square-wave response function, Wiener spectrum and detective quantum efficiency (DQE). In addition, subjective image quality was assessed using a calibrated threshold contrast detail detectability (TCDD)

Stephen M. Kengyelics; Arnold R. Cowen; Andrew G. Davies

1999-01-01

367

A no-reference image quality evaluation based on power spectrum  

Microsoft Academic Search

No-reference quality evaluation is more difficult because it does not refer to any image. However, in some cases, like virtual view images, can not find the reference image, no-reference method had to be used. With the free viewpoint video technology development and application, measuring the performance of the multiview video system is essential and virtual view image quality evaluation is

Yan Zhang; Ping An; Qiuwen Zhang; Liquan Shen; Zhaoyang Zhang

2011-01-01

368

The Research of Digital Image Quality Evaluation Method for Beef Tenderness  

Microsoft Academic Search

Abstract-Digital image quality evaluation is a relatively new area of research. In this field, how to choose a good image is an important research content for enhancing the efficiency of pattern recognition system. In this paper, beef images are used as an object of study for computing tenderness. Based on the traditional evaluation method of image quality, the thesis analyzes

Jian Wang; Guo-min Zhou

2010-01-01

369

Characterization of image quality for 3D scatter-corrected breast CT images  

NASA Astrophysics Data System (ADS)

The goal of this study was to characterize the image quality of our dedicated, quasi-monochromatic spectrum, cone beam breast imaging system under scatter corrected and non-scatter corrected conditions for a variety of breast compositions. CT projections were acquired of a breast phantom containing two concentric sets of acrylic spheres that varied in size (1-8mm) based on their polar position. The breast phantom was filled with 3 different concentrations of methanol and water, simulating a range of breast densities (0.79-1.0g/cc); acrylic yarn was sometimes included to simulate connective tissue of a breast. For each phantom condition, 2D scatter was measured for all projection angles. Scatter-corrected and uncorrected projections were then reconstructed with an iterative ordered subsets convex algorithm. Reconstructed image quality was characterized using SNR and contrast analysis, and followed by a human observer detection task for the spheres in the different concentric rings. Results show that scatter correction effectively reduces the cupping artifact and improves image contrast and SNR. Results from the observer study indicate that there was no statistical difference in the number or sizes of lesions observed in the scatter versus non-scatter corrected images for all densities. Nonetheless, applying scatter correction for differing breast conditions improves overall image quality.

Pachon, Jan H.; Shah, Jainil; Tornai, Martin P.

2011-03-01

370

Readout-Segmented Echo-Planar Imaging in Diffusion-Weighted MR Imaging in Breast Cancer: Comparison with Single-Shot Echo-Planar Imaging in Image Quality  

PubMed Central

Objective The purpose of this study was to compare the image quality of standard single-shot echo-planar imaging (ss-EPI) and that of readout-segmented EPI (rs-EPI) in patients with breast cancer. Materials and Methods Seventy-one patients with 74 breast cancers underwent both ss-EPI and rs-EPI. For qualitative comparison of image quality, three readers independently assessed the two sets of diffusion-weighted (DW) images. To evaluate geometric distortion, a comparison was made between lesion lengths derived from contrast enhanced MR (CE-MR) images and those obtained from the corresponding DW images. For assessment of image parameters, signal-to-noise ratio (SNR), lesion contrast, and contrast-to-noise ratio (CNR) were calculated. Results The rs-EPI was superior to ss-EPI in most criteria regarding the qualitative image quality. Anatomical structure distinction, delineation of the lesion, ghosting artifact, and overall image quality were significantly better in rs-EPI. Regarding the geometric distortion, lesion length on ss-EPI was significantly different from that of CE-MR, whereas there were no significant differences between CE-MR and rs-EPI. The rs-EPI was superior to ss-EPI in SNR and CNR. Conclusion Readout-segmented EPI is superior to ss-EPI in the aspect of image quality in DW MR imaging of the breast. PMID:25053898

Kim, Yun Ju; Kang, Bong Joo; Park, Chang Suk; Kim, Hyeon Sook; Son, Yo Han; Porter, David Andrew; Song, Byung Joo

2014-01-01

371

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. PMID:19014545

Lessa, Patrícia S; Caous, Cristofer A; Arantes, Paula R; Amaro, Edson; de Souza, Fernando M Campello

2008-01-01

372

Image Quality of the Helioseismic and Magnetic Imager (HMI) Onboard the Solar Dynamics Observatory (SDO)  

NASA Technical Reports Server (NTRS)

We describe the imaging quality of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) as measured during the ground calibration of the instrument. We describe the calibration techniques and report our results for the final configuration of HMI. We present the distortion, modulation transfer function, stray light,image shifts introduced by moving parts of the instrument, best focus, field curvature, and the relative alignment of the two cameras. We investigate the gain and linearity of the cameras, and present the measured flat field.

Wachter, R.; Schou, Jesper; Rabello-Soares, M. C.; Miles, J. W.; Duvall, T. L., Jr.; Bush, R. I.

2011-01-01

373

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

374

Axial strain imaging of intravascular data: results on polyvinyl alcohol cryogel phantoms and carotid artery  

Microsoft Academic Search

Mapping the local elastic properties of an atherosclerotic artery is of major interest for predicting the disease evolution or an intervention outcome. These properties can be investigated by elastography, which estimates the strain distribution within a medium in response to a stress. But because diseased arteries are highly heterogeneous, a small global deformation may result in high local strains in

Elisabeth Brusseau; Jérémie Fromageau; Gérard Finet; Philippe Delachartre; Didier Vray

2001-01-01

375

Degraded visual environment image/video quality metrics  

NASA Astrophysics Data System (ADS)

A number of image quality metrics (IQMs) and video quality metrics (VQMs) have been proposed in the literature for evaluating techniques and systems for mitigating degraded visual environments. Some require both pristine and corrupted imagery. Others require patterned target boards in the scene. None of these metrics relates well to the task of landing a helicopter in conditions such as a brownout dust cloud. We have developed and used a variety of IQMs and VQMs related to the pilot's ability to detect hazards in the scene and to maintain situational awareness. Some of these metrics can be made agnostic to sensor type. Not only are the metrics suitable for evaluating algorithm and sensor variation, they are also suitable for choosing the most cost effective solution to improve operating conditions in degraded visual environments.

Baumgartner, Dustin D.; Brown, Jeremy B.; Jacobs, Eddie L.; Schachter, Bruce J.

2014-06-01

376

Influence of void on image quality of industrial SPECT  

NASA Astrophysics Data System (ADS)

Industrial single photon emission computed tomography (SPECT) is a promising technique to determine the dynamic behavior of industrial process media and has been developed in the Korea Atomic Energy Research Institute. The present study evaluated the influence of a void, which is presence in multiphase reactors of industrial process, on the image quality of an industrial SPECT. The results are very encouraging; that is, the performance of the industrial SPECT system is little influenced by the presence of a void, which means that industrial SPECT is an appropriate tool to estimate the dynamic characteristics of the process media in a water-air phase bubble column with a static gas sparger.

Park, J. G.; Jung, S. H.; Kim, J. B.; Moon, J.; Kim, C. H.

2013-12-01

377

The quality of the X-ray image: fault analysis.  

PubMed

Current guidelines encourage dentists to assess the quality of the radiographs that they take as a normal part of their routine, and peer review is recommended on a regular basis. Technical faults or processing errors may result in unsatisfactory diagnostic images. In order to rectify such faults and to prevent their recurrence it is vital that the practitioner is able to recognize them and determine their cause. This article proposes a user-friendly approach to recognition of technical (procedural) faults, and gives advice on their prevention. PMID:18170953

Brocklebank, L M

1998-06-01

378

Nonlinear filtering for character recognition in low quality document images  

NASA Astrophysics Data System (ADS)

Optical character recognition in scanned printed documents is a well-studied task, where the captured conditions like sheet position, illumination, contrast and resolution are controlled. Nowadays, it is more practical to use mobile devices for document capture than a scanner. So as a consequence, the quality of document images is often poor owing to presence of geometric distortions, nonhomogeneous illumination, low resolution, etc. In this work we propose to use multiple adaptive nonlinear composite filters for detection and classification of characters. Computer simulation results obtained with the proposed system are presented and discussed.

Diaz-Escobar, Julia; Kober, Vitaly

2014-09-01

379

No-reference remote sensing image quality assessment using a comprehensive evaluation factor  

NASA Astrophysics Data System (ADS)

The conventional image quality assessment algorithm, such as Peak Signal to Noise Ratio ?PSNR?? Mean Square Error?MSE? and structural similarity (SSIM), needs the original image as a reference. It's not applicable to the remote sensing image for which the original image cannot be assumed to be available. In this paper, a No-reference Image Quality Assessment (NRIQA) algorithm is presented to evaluate the quality of remote sensing image. Since blur and noise (including the stripe noise) are the common distortion factors affecting remote sensing image quality, a comprehensive evaluation factor is modeled to assess the blur and noise by analyzing the image visual properties for different incentives combined with SSIM based on human visual system (HVS), and also to assess the stripe noise by using Phase Congruency (PC). The experiment results show this algorithm is an accurate and reliable method for Remote Sensing Image Quality Assessment.

Wang, Lin; Wang, Xu; Li, Xiao; Shao, Xiaopeng

2014-05-01

380

The effect of ambient illumination on handheld display image quality.  

PubMed

Handheld devices such as smartphones and tablets are becoming useful in the medical field, as they allow physicians, radiologists, and researchers to analyze images with the benefit of mobile accessibility. However, for handheld devices to be effective, the display must be able to perform well in a wide range of ambient illumination conditions. We conducted visual experiments to quantify user performance for testing the image quality of two current-generation devices in different ambient illumination conditions while measuring ambient light levels with a real-time illuminance meter. We found and quantified that due to the high reflectivity of handheld devices, performance deteriorates as the user moves from dark areas into environments of greater ambient illumination. The quantitative analysis suggests that differences in display reflection coefficients do not affect the low illumination performance of the device but rather the performance at higher levels of illumination. PMID:24113844

Liu, Peter; Zafar, Fahad; Badano, Aldo

2014-02-01

381

Impact of chopping on image quality in the SIRTF telescope  

NASA Technical Reports Server (NTRS)

The initial Phase-A concept for the Space Infrared Telescope Facility (SIRTF), which was established in 1981, is concerned with a cryogenically cooled, 85 cm diameter, f/24 Ritchey-Chretien telescope, followed by a Multiple Instrument Chamber (MIC), containing six scientific instruments. In 1982, the Phase-A concept was reviewed with the aim to assess the technical readiness for the next phase of development. Various areas of concern were subsequently investigated in three parallel studies by industry. Two of the arising questions are considered in the present paper, taking into account the system and technology implications of achieving diffraction-limited resolution at 2 microns, and the limitations on the size of the imaging field under this condition. The conducted study takes into account an evaluation of the different methods of chopping. Attention is given to the telescope parameters, symmetric chopping, asymmetrical chopping, focus and alignment errors, the wavefront-error budget, and image quality.

Bottema, M.

1985-01-01

382

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

383

600 IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 13, NO. 4, APRIL 2004 Image Quality Assessment: From Error Visibility to  

E-print Network

600 IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 13, NO. 4, APRIL 2004 Image Quality Assessment a variety of roles in image processing applications. First, it can be used to dy- namically monitor to optimize algorithms and parameter settings of image processing systems. For instance, in a visual

Wang, Zhou

384

Assessment of image quality in x-ray radiography imaging using a small plasma focus device  

NASA Astrophysics Data System (ADS)

This paper offers a comprehensive investigation of image quality parameters for a small plasma focus as a pulsed hard x-ray source for radiography applications. A set of images were captured from some metal objects and electronic circuits using a low energy plasma focus at different voltages of capacitor bank and different pressures of argon gas. The x-ray source focal spot of this device was obtained to be about 0.6 mm using the penumbra imaging method. The image quality was studied by several parameters such as image contrast, line spread function (LSF) and modulation transfer function (MTF). Results showed that the contrast changes by variations in gas pressure. The best contrast was obtained at a pressure of 0.5 mbar and 3.75 kJ stored energy. The results of x-ray dose from the device showed that about 0.6 mGy is sufficient to obtain acceptable images on the film. The measurements of LSF and MTF parameters were carried out by means of a thin stainless steel wire 0.8 mm in diameter and the cut-off frequency was obtained to be about 1.5 cycles/mm.

Kanani, A.; Shirani, B.; Jabbari, I.; Mokhtari, J.

2014-08-01

385

Correlation of the clinical and physical image quality in chest radiography for average adults with a computed radiography imaging system  

PubMed Central

Objective: The purpose of this study was to examine the correlation between the quality of visually graded patient (clinical) chest images and a quantitative assessment of chest phantom (physical) images acquired with a computed radiography (CR) imaging system. Methods: The results of a previously published study, in which four experienced image evaluators graded computer-simulated postero-anterior chest images using a visual grading analysis scoring (VGAS) scheme, were used for the clinical image quality measurement. Contrast-to-noise ratio (CNR) and effective dose efficiency (eDE) were used as physical image quality metrics measured in a uniform chest phantom. Although optimal values of these physical metrics for chest radiography were not derived in this work, their correlation with VGAS in images acquired without an antiscatter grid across the diagnostic range of X-ray tube voltages was determined using Pearson’s correlation coefficient. Results: Clinical and physical image quality metrics increased with decreasing tube voltage. Statistically significant correlations between VGAS and CNR (R=0.87, p<0.033) and eDE (R=0.77, p<0.008) were observed. Conclusion: Medical physics experts may use the physical image quality metrics described here in quality assurance programmes and optimisation studies with a degree of confidence that they reflect the clinical image quality in chest CR images acquired without an antiscatter grid. Advances in knowledge: A statistically significant correlation has been found between the clinical and physical image quality in CR chest imaging. The results support the value of using CNR and eDE in the evaluation of quality in clinical thorax radiography. PMID:23568362

Wood, T J; Beavis, A W; Saunderson, J R

2013-01-01

386

Diagnostic accuracy of global myocardial deformation indexes in coronary artery disease: a velocity vector imaging study.  

PubMed

The aim of our study was to assess the diagnostic accuracy of a global longitudinal strain and strain rate (GLS, GLSR) and mean radial strain and strain rate (MRS, MRSR) of the left ventricle to predict multivessel disease. In 113 patients, who underwent coronary angiography, left ventricular deformation was analysed by speckle-tracking based velocity vector imaging. In three standard apical views strain and strain rate curves were generated corresponding with two opposite basal, mid, and apical segments. The negative peaks of systolic strain and strain rate from 18 curves were averaged as GLS and GLSR. Similarly, in short axis view 6 negative systolic peaks were averaged and considered as MRS and MRSR. Four subgroups were defined: (1) without significant coronary stenosis, 0-vessel disease (0VD), (2) single-vessel disease (1VD), (3) double-vessel disease (2VD), and (4) triple-vessel disease (3VD). In comparison with patients without significant coronary artery disease, all deformation indexes were significantly decreased in patients with 3VD. The left ventricular ejection fraction (LVEF) and wall motion score index (WMSI) showed lower significance level as deformation parameters. MRSR was the strongest predictor of multivessel disease. Receiver-operating characteristic curves (ROC) showed that MRSR had the highest diagnostic accuracy. Comparing ROC areas, MRSR had significantly higher diagnostic accuracy than LVEF and WMSI. The results of our study show that global deformation indexes have a good diagnostic accuracy in differentiating multivessel disease. MRSR tended to be better in identification of 3VD than traditional indexes of global and regional left ventricular function. PMID:22327941

Valocik, Gabriel; Valocikova, Ivana; Mitro, Peter; Fojtikova, Livia; Druzbacka, Ludmila; Kristofova, Beata; Juhas, Stanislav; Kolesar, Adrian; Sabol, Frantisek

2012-12-01

387

Comparison of quality of life in patients with peripheral arterial disease caused by atherosclerosis obliterans or Buerger’s disease  

PubMed Central

Summary Objective Buerger’s disease and atherosclerosis obliterans (ASO) are two peripheral arterial diseases (PAD) that are frequently encountered. The aim of this study was to compare quality of life (QOL) in patients with Buerger’s disease and ASO. Methods We prospectively followed 86 patients who were admitted to our hospital due to ASO or Buerger’s disease. Their ischaemia was evaluated according to the clinical category chronic limb ischaemia at the time of hospital admission and at six and 12 months. The QOL was measured at the time of hospital admission and at six and 12 months with the Short Form Health Status Survey (SF-36) and Vascular Quality of Life Questionnaire (VASCUQOL). Results A total of 86 patients with ASO or Buerger’s disease (47 and 39, respectively) were included in the study. Pain parameters from both SF-36 and VASCUQOL scores were lower in patients with Buerger’s disease at the time of hospital admission and at six months. The impairment in QOL was found to be proportional to the extent of chronic limb ischaemia. Conversely, when patients with critical limb ischaemia were evaluated, no difference was observed between those with ASO or Buerger’s disease in terms of QOL. Amputations were found to have a negative effect on quality of life. Conclusion Buerger’s disease had a more pronounced negative effect on QOL than ASO, particularly in terms of pain score. When critical limb ischaemia was considered, ASO and Buerger’s disease impaired quality of life at the same rate. PMID:25000442

Karakoyun, Rojbin; Köksoy, Cüneyt; ?ener, Zeynep; Gündüz, Umut; Karaka?, Bar??; Karakoyun, Mustafa

2014-01-01

388

Principles and Applications of Hyperspectral Imaging in Quality Evaluation of Agro-Food Products: A Review  

Microsoft Academic Search

The requirements of reliability, expeditiousness, accuracy, consistency, and simplicity for quality assessment of food products encouraged the development of non-destructive technologies to meet the demands of consumers to obtain superior food qualities. Hyperspectral imaging is one of the most promising techniques currently investigated for quality evaluation purposes in numerous sorts of applications. The main advantage of the hyperspectral imaging system

Gamal Elmasry; Mohammed Kamruzzaman; Da-Wen Sun; Paul Allen

2012-01-01

389

An improved Markov-based localization approach by using image quality evaluation  

Microsoft Academic Search

This paper presents a new approach for the classical Markov localization method for mobile robots by using image quality evaluation. Machine learning techniques have been used to obtain the quality of the images. This quality value is used to select the best information source, between odometry and sensor information. Real experiments in different scenarios of the Robocup standard platform league

José A. Gámez; Ismael García-varea; Jesus Martinez-gomez

2008-01-01

390

Recent developments in the applications of image processing techniques for food quality evaluation  

Microsoft Academic Search

Image processing techniques have been applied increasingly for food quality evaluation in recent years. This paper reviews recent advances in image processing techniques for food quality evaluation, which include charge coupled device camera, ultrasound, magnetic resonance imaging, computed tomography, and electrical tomography for image acquisition; pixel and local pre-processing approaches for image pre-processing; thresholding-based, gradient-based, region-based, and classification-based methods for

Cheng-Jin Du; Da-Wen Sun

2004-01-01

391

Monitoring Lake Simcoe water quality using Landsat TM images  

NASA Astrophysics Data System (ADS)

Inland lakes are important resources to humans, while the eutrophication effect caused by an overload of nutrients is a significant problem. This study focuses on utilizing the satellite remote sensing to monitor the water quality of Lake Simcoe, Ontario, Canada, which has been suffering from the overload of Total Phosphorus (TP) and therefore eutrophication for decades. The data employed in this study includes 22 cloud-free Landsat 5 TM images, as well as the nearly simultaneous in-situ data from 15 observation stations on the lake. Compared to the generally used model, an improved model is developed in this study to estimate the Secchi Disk Transparency (SDT), a parameter for water clarity measurements, using the TM images. Models based on different band combinations are compared to estimate the chlorophyll- a (chl-a) concentration. The results of these estimations are validated using the in-situ data by the linear regression analysis, and the accuracies are measured by the correlation coefficients R 2. The results reveal that the improved SDT model provides higher prediction accuracies than the general model when applied to 68.2% (15 out of 22) of the images. The majority of the SDT predictions show high R 2, whereas some of the estimated chl-a concentrations have weak relationships with the in-situ data. The possible reasons for this are the geo-location of stations, as well as the influences of chl- a and Dissolved Organic Carbon (DOC). The resultant concentration maps indicate that the eutrophic water is normally distributed at the near-shore areas and the northeastern part of Lake Simcoe. In addition, the southern Cook's Bay has always been suffering from an extremely serious water quality problem even until now. Meanwhile, the water quality of the southwestern part of Lake Simcoe is much better than the other parts of this lake. The results also show that the water quality of Lake Simcoe was at its worst in August and September for the past 22 years while it was much better in the other sampling seasons. According to the trend of the monthly averaged SDT, on an overall scale, the SDT dropped from 1980 to 1982 and then kept relatively stable until the fall of 1992, followed by a gradual increase until 2000, and then stayed constant until the summer of 2008. The chl-a concentration reveals an inverse trend, i.e., the higher the chl-a concentration, the more turbid the water.

Guan, Xian

392

Virtual monochromatic imaging in dual-source dual-energy CT: Radiation dose and image quality  

PubMed Central

Purpose: To evaluate the image quality of virtual monochromatic images synthesized from dual-source dual-energy computed tomography (CT) in comparison with conventional polychromatic single-energy CT for the same radiation dose. Methods: In dual-energy CT, besides the material-specific information, one may also synthesize monochromatic images at different energies, which can be used for routine diagnosis similar to conventional polychromatic single-energy images. In this work, the authors assessed whether virtual monochromatic images generated from dual-source CT scanners had an image quality similar to that of polychromatic single-energy images for the same radiation dose. First, the authors provided a theoretical analysis of the optimal monochromatic energy for either the minimum noise level or the highest iodine contrast to noise ratio (CNR) for a given patient size and dose partitioning between the low- and high-energy scans. Second, the authors performed an experimental study on a dual-source CT scanner to evaluate the noise and iodine CNR in monochromatic images. A thoracic phantom with three sizes of attenuating rings was used to represent four adult sizes. For each phantom size, three dose partitionings between the low-energy (80 kV) and the high-energy (140 kV) scans were used in the dual-energy scan. Monochromatic images at eight energies (40 to 110 keV) were generated for each scan. Phantoms were also scanned at each of the four polychromatic single energy (80, 100, 120, and 140 kV) with the same radiation dose. Results: The optimal virtual monochromatic energy depends on several factors: phantom size, partitioning of the radiation dose between low- and high-energy scans, and the image quality metrics to be optimized. With the increase of phantom size, the optimal monochromatic energy increased. With the increased percentage of radiation dose on the low energy scan, the optimal monochromatic energy decreased. When maximizing the iodine CNR in monochromatic images, the optimal energy was lower than that when minimizing noise level. When the total radiation dose was equally distributed between low and high energy in dual-energy scans, for minimum noise, the optimal energies were 68, 71, 74, and 77 keV for small, medium, large, and extra-large (xlarge) phantoms, respectively; for maximum iodine CNR, the optimal energies were 66, 68, 70, 72 keV. With the optimal monochromatic energy, the noise level was similar to and the CNR was better than that in a single-energy scan at 120 kV for the same radiation dose. Compared to an 80 kV scan, however, the iodine CNR in monochromatic images was lower for the small, medium, and large phantoms. Conclusions: In dual-source dual-energy CT, optimal virtual monochromatic energy depends on patient size, dose partitioning, and the image quality metric optimized. With the optimal monochromatic energy, the noise level was similar to and the iodine CNR was better than that in 120 kV images for the same radiation dose. Compared to single-energy 80 kV images, the iodine CNR in virtual monochromatic images was lower for small to large phantom sizes. PMID:22149820

Yu, Lifeng; Christner, Jodie A.; Leng, Shuai; Wang, Jia; Fletcher, Joel G.; McCollough, Cynthia H.

2011-01-01

393

Task-based measures of image quality and their relation to radiation dose and patient risk  

NASA Astrophysics Data System (ADS)

The theory of task-based assessment of image quality is reviewed in the context of imaging with ionizing radiation, and objective figures of merit (FOMs) for image quality are summarized. The variation of the FOMs with the task, the observer and especially with the mean number of photons recorded in the image is discussed. Then various standard methods for specifying radiation dose are reviewed and related to the mean number of photons in the image and hence to image quality. Current knowledge of the relation between local radiation dose and the risk of various adverse effects is summarized, and some graphical depictions of the tradeoffs between image quality and risk are introduced. Then various dose-reduction strategies are discussed in terms of their effect on task-based measures of image quality.

Barrett, Harrison H.; Myers, Kyle J.; Hoeschen, Christoph; Kupinski, Matthew A.; Little, Mark P.

2015-01-01

394

Diffusion imaging quality control via entropy of principal direction distribution.  

PubMed

Diffusion MR imaging has received increasing attention in the neuroimaging community, as it yields new insights into the microstructural organization of white matter that are not available with conventional MRI techniques. While the technology has enormous potential, diffusion MRI suffers from a unique and complex set of image quality problems, limiting the sensitivity of studies and reducing the accuracy of findings. Furthermore, the acquisition time for diffusion MRI is longer than conventional MRI due to the need for multiple acquisitions to obtain directionally encoded Diffusion Weighted Images (DWI). This leads to increased motion artifacts, reduced signal-to-noise ratio (SNR), and increased proneness to a wide variety of artifacts, including eddy-current and motion artifacts, "venetian blind" artifacts, as well as slice-wise and gradient-wise inconsistencies. Such artifacts mandate stringent Quality Control (QC) schemes in the processing of diffusion MRI data. Most existing QC procedures are conducted in the DWI domain and/or on a voxel level, but our own experiments show that these methods often do not fully detect and eliminate certain types of artifacts, often only visible when investigating groups of DWI's or a derived diffusion model, such as the most-employed diffusion tensor imaging (DTI). Here, we propose a novel regional QC measure in the DTI domain that employs the entropy of the regional distribution of the principal directions (PD). The PD entropy quantifies the scattering and spread of the principal diffusion directions and is invariant to the patient's position in the scanner. High entropy value indicates that the PDs are distributed relatively uniformly, while low entropy value indicates the presence of clusters in the PD distribution. The novel QC measure is intended to complement the existing set of QC procedures by detecting and correcting residual artifacts. Such residual artifacts cause directional bias in the measured PD and here called dominant direction artifacts. Experiments show that our automatic method can reliably detect and potentially correct such artifacts, especially the ones caused by the vibrations of the scanner table during the scan. The results further indicate the usefulness of this method for general quality assessment in DTI studies. PMID:23684874

Farzinfar, Mahshid; Oguz, Ipek; Smith, Rachel G; Verde, Audrey R; Dietrich, Cheryl; Gupta, Aditya; Escolar, Maria L; Piven, Joseph; Pujol, Sonia; Vachet, Clement; Gouttard, Sylvain; Gerig, Guido; Dager, Stephen; McKinstry, Robert C; Paterson, Sarah; Evans, Alan C; Styner, Martin A

2013-11-15

395

Diffusion imaging quality control via entropy of principal direction distribution  

PubMed Central

Diffusion MR imaging has received increasing attention in the neuroimaging community, as it yields new insights into the microstructural organization of white matter that are not available with conventional MRI techniques. While the technology has enormous potential, diffusion MRI suffers from a unique and complex set of image quality problems, limiting the sensitivity of studies and reducing the accuracy of findings. Furthermore, the acquisition time for diffusion MRI is longer than conventional MRI due to the need for multiple acquisitions to obtain directionally encoded Diffusion Weighted Images (DWI). This leads to increased motion artifacts, reduced signal-to-noise ratio (SNR), and increased proneness to a wide variety of artifacts, including eddy-current and motion artifacts, “venetian blind” artifacts, as well as slice-wise and gradient-wise inconsistencies. Such artifacts mandate stringent Quality Control (QC) schemes in the processing of diffusion MRI data. Most existing QC procedures are conducted in the DWI domain and/or on a voxel level, but our own experiments show that these methods often do not fully detect and eliminate certain types of artifacts, often only visible when investigating groups of DWI's or a derived diffusion model, such as the most-employed diffusion tensor imaging (DTI). Here, we propose a novel regional QC measure in the DTI domain that employs the entropy of the regional distribution of the principal directions (PD). The PD entropy quantifies the scattering and spread of the principal diffusion directions and is invariant to the patient's position in the scanner. High entropy value indicates that the PDs are distributed relatively uniformly, while low entropy value indicates the presence of clusters in the PD distribution. The novel QC measure is intended to complement the existing set of QC procedures by detecting and correcting residual artifacts. Such residual artifacts cause directional bias in the measured PD and here called dominant direction artifacts. Experiments show that our automatic method can reliably detect and potentially correct such artifacts, especially the ones caused by the vibrations of the scanner table during the scan. The results further indicate the usefulness of this method for general quality assessment in DTI studies. PMID:23684874

Oguz, Ipek; Smith, Rachel G.; Verde, Audrey R.; Dietrich, Cheryl; Gupta, Aditya; Escolar, Maria L.; Piven, Joseph; Pujol, Sonia; Vachet, Clement; Gouttard, Sylvain; Gerig, Guido; Dager, Stephen; McKinstry, Robert C.; Paterson, Sarah; Evans, Alan C.; Styner, Martin A.

2013-01-01

396

3D MR angiographic visualization and artery-vein separation  

NASA Astrophysics Data System (ADS)

The common approach for artery-vein separation applies a presaturation pulse to obtain different image intensity representations in MRA data for arteries and veins. However, when arteries and veins do not run in opposite directions as in the brain, lungs, and heart, this approach fails. This paper presents an image processing approach devised for artery-vein separation. The anatomic separation utilizes fuzzy connected object delineation. The first step of this separation method is the segmentation of the entire vessel structure from the background via absolute connectedness by using scale-based affinity. The second step is to separate artery from vein via relative connectedness. After 'seed' points are specified inside artery and vein in the vessel- only image, the operation is performed in an iterative fashion. The small regions of the bigger aspects of artery and vein are separated in the initial iteration. Further regions are added with the subsequent iterations so that the small aspects of artery and vein are included in alter iterations. Shell rendering is used for 3D display. Combining the strengths of fuzzy connected object definition, object separation, and shell rendering, high- quality volume rendering of vascular information in MRA data has been achieved. MS-325 contrast-enhanced MRA were used to illustrate this approach. Several examples of 3D display of arteries and veins are included to show the considerable promise of this new approach.

Lei, Tianhu; Udupa, Jayaram K.; Saha, Punam K.; Odhner, Dewey

1999-05-01

397

Numerical Simulation System for Blood Flow in the Cerebral Artery Using CT Imaging Data  

NASA Astrophysics Data System (ADS)

Over 90% of subarachnoid hemorrhages are caused by rupture of a cerebral aneurysm. Medical statistics indicate that cerebral aneurysm occurs predominantly in arteries which branch off with sharp curvature, where flow and wall shear stress change abruptly. In this paper, a system for analysis of flow in the cerebral artery is constructed. In this system, numerical simulation is conducted for geometry, which is extracted from computed tomographic angiography of the cerebral artery. The boundary conditions are modeled from measured data and are prescribed to simulate hemodynamics in the real situation. This system investigates effects of geometry on wall shear stress distribution and the flow pattern in the artery. Wall shear stress was found to be concentrated in specific areas due to effects of curvature.

Torii, Ryo; Oshima, Marie; Kobayashi, Toshio; Takagi, Kiyoshi

398

Image Quality Evaluation Based on HVS and Energy-Weighted Subband of Wavelet Transform  

Microsoft Academic Search

A new objective image quality evaluation method is proposed based on DWT and HVS (Human Visual System). The sensitivity of HVS is weighted with both subband and its energy. In order to verify the reliability of WEWMSE method and to demonstrate the effectiveness, image quality evaluation experiments based on the proposed method are performed on a set of images after

Jiang Ming; Sun Shui-fa; Dong Fangmin; Lei Bangjun

2008-01-01

399

Image quality evaluation of a LightSpeed CT750 HD computed tomography system  

Microsoft Academic Search

With the advancement of Computed Tomography technology, improving image quality while reducing patient dose has been a big technical challenge. The recent CT750 HD system from GE Healthcare provides significantly improved spatial resolution and the capability to reduce dose during routine clinical imaging. This paper evaluates the image quality of this system. Spatial resolution, dose reduction, noise, and low contrast

Jiahua Fan; Frank Dong; Paavana Sainath; Jiang Hsieh; Xiangyang Tang; Thomas Toth; Baojun Li; Peter Crandall; Robert Senzig; Adam Dixon

2009-01-01

400

ImQual: a web-service dedicated to image quality evaluation and metrics benchmark  

Microsoft Academic Search

Quality assessment is becoming an important issue in the framework of image and video processing. Images are generally intended to be viewed by human observers and thus the consideration of the visual perception is an intrinsic aspect of the effective assessment of image quality. This observation has been made for different application domains such as printing, compression, transmission, and so

Michael Nauge; Mohamed-Chaker Larabi; Christine Fernandez-Maloigne

2011-01-01

401

Absence of the Left Main Coronary Artery: MDCT Coronary Angiographic Imaging  

PubMed Central

Absent left main coronary artery (LMCA) is a rare congenital cardiac malformation. We present a case report of a 65-year-old woman with anomalous origin of the left anterior descending (LAD) and circumflex (LCx) artery separated from the left sinus of Valsalva that was diagnosed by multi-detector row computed tomography (MDCT) coronary angiography. Our case indicates that MDCT plays an important role in the diagnosis of some rare coronary anomalies.

Yilmaz-Cankaya, Bahar; Kantarci, Mecit; Yalcin, Ahmet; Durur-Karakaya, Afak; Yuce, Ihsan

2009-01-01