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PubMed2006

A mesh-based disparity representation method for view interpolation and stereo image compression.

This paper proposes a mesh-based representation method for the disparity map of stereo images. The proposed method is designed to concentrate mainly on applications of view interpolation and stereo image compression. To obtain high image quality in the view interpolation and compression of stereo images, we formulate the view-interpolation error and prediction error. In the formulation, the view-interpolation and prediction errors depend not only on the accuracy of the disparity map, but also on the gradient of the stereo images. The proposed representation method for the disparity map is based on a triangular mesh structure, which minimizes the formulated interpolation and prediction errors. The experimental results show that the proposed method yields higher quality view-interpolated images and also has better performance in stereo image compression than the conventional methods.

Algorithms↗
PubMed1990

Enhancement and compression of digital chest radiographs.

The application of digital technologies to chest radiography holds the promise of routine application of image processing techniques to effect image enhancement. Because of their inherent spatial resolution, however, digital chest images impose severe constraints on data storage devices. Compression of these images will relax such constraints and facilitate image transmission on a digital network. We evaluated an algorithm for enhancing digital chest images that has allowed significant data compression while improving the diagnostic quality of the image. This algorithm is based on the photographic technique of unsharp masking. Image quality was measured with respect to the task of tumor detection and compression ratios as high as 2:1 were achieved. This compression can be supplemented by irreversible methods.

Algorithms↗
PubMed1989

Needle localization of nonpalpable breast lesions with a portable dual-grid compression system. Work in progress.

A new device and a geometric algorithm facilitate consistent insertion of a needle tip into nonpalpable breast lesions on a single attempt. With the breast compressed by dual grid plates, two oblique exposures are taken. Three intersecting planes through the lesion referenced to the grid markings permit easy determination of the lesion coordinates. In initial trials for preoperative breast lesion localization in 11 patients, the needle tip was within the lesion in nine patients and was within 0.5 cm of the lesion in two patients. The results indicate that this system is very useful for accurate localization and needle aspiration of breast lesions.

Adult↗
PubMed2002

Experience with a DICOM-compatible digital pediatric echocardiography laboratory.

A digital pediatric echocardiography laboratory, without videotape redundancy was established at Children's Hospital of Wisconsin in December 1998. To characterize the experience, 1198 consecutive patient studies were reviewed-50% from the first 2 months after establishing the digital protocol and 50% from the last 2 months available. Each study was stored using a protocol that was based on capture of single beat clips of relevant two-dimensional/color Doppler imaging and static frame spectral Doppler tracings. Studies were digitally compressed using a DICOM-compatible JPEG algorithm at 20:1 and edited with deletions of redundant clips to minimize archival storage needs. Study quality was uniformly excellent, and no errors were attributable to the digital protocol or compression-related loss of information. The average study required 21.5 +/- 11.4 MB of storage space with 35.4 +/- 12.3 total clips/study captured. Studies reviewed from the earlier experience were not significantly larger (23.6 +/- 14 vs 19.7 +/- 8.1 MB, 35.6 +/- 12.5 vs 35.2 +/- 12 clips) than those done recently. Studies in patients with isolated ventricular septal defect used comparable storage (23.7 +/- 8.9 MB, 42.8 +/- 11.5 clips) to that of the group as a whole. More complex congenital heart disease studies were slightly larger-tetralogy of Fallot (28.2 +/- 19.5 MB, 43.4 +/- 13.9 clips), transposition of the great arteries (30.6 +/- 17.4 MB, 40.3 +/- 16.7 clips), and single ventricle (29.7 +/- 19.6 MB, 39.9 +/- 12 clips)--although this trend was not significant. This study suggests that digital pediatric echo is feasible using a DICOM-compatible protocol with maintenance of diagnostic integrity despite compression of study size to allow rapid archival storage and retrieval.

Algorithms↗
PubMed2006

Noise reduction from genotyping microarrays using probe level information.

Genomic copy number change is one of the important phenomenon observed in cancer and other genetic disorders. Recently oligonucleotide microarrays have been used to analyze changes in the copy number. Although high density microarrays provide genome wide useful data on copy number, they are often associated with substantial amount of experimental noise that could affect the performance of the analyses. We used the high density oligonucleotide genotyping microarrays in our experiments that uses redundant probe tiling approach for individual SNPs. We found that the noise in the genotyping microarray data is associated with several experimental steps during target preparation and devised an algorithm that takes into account those experimental parameters. Additionally, defective probes that do not hybridize well to the target and therefore could not be modified inherently were detected and omitted automatically by using the algorithm. When we applied the algorithm to actual datasets, we could reduce the noise substantially without compressing the dynamic range. Additionally, combinatorial use of our noise reduction algorithm and conventional breakpoint detection algorithm successfully detected a microamplification of c-myc which was overlooked in the raw data. The algorithm described here is freely available with the software upon request to all non-profit researchers.

Adenocarcinoma↗
PubMed2005

Optimization of integer wavelet transforms based on difference correlation structures.

In this paper, a novel lifting integer wavelet transform based on difference correlation structure (DCCS-LIWT) is proposed. First, we establish a relationship between the performance of a linear predictor and the difference correlations of an image. The obtained results provide a theoretical foundation for the following construction of the optimal lifting filters. Then, the optimal prediction lifting coefficients in the sense of least-square prediction error are derived. DCCS-LIWT puts heavy emphasis on image inherent dependence. A distinct feature of this method is the use of the variance-normalized autocorrelation function of the difference image to construct a linear predictor and adapt the predictor to varying image sources. The proposed scheme also allows respective calculations of the lifting filters for the horizontal and vertical orientations. Experimental evaluation shows that the proposed method produces better results than the other well-known integer transforms for the lossless image compression.

Algorithms↗
PubMed2005

Effect of CT image compression on computer-assisted lung nodule volume measurement.

PURPOSE: To evaluate the effect of two-dimensional wavelet-based computed tomographic (CT) image compression according to the Joint Photographic Experts Group (JPEG) 2000 standard on computer-assisted assessment of nodule volume. MATERIALS AND METHODS: This HIPAA-compliant study was approved by the research board at the authors' institution; patients' informed consent was not required. Fifty-one nodules in 23 patients (seven men, 16 women; mean age, 59 years; age range, 39-75 years) were selected on low-dose CT scans that were compressed to levels of 10:1, 20:1, 30:1, and 40:1 by using a two-dimensional JPEG 2000 wavelet-based image compression method. Nodules were classified according to size (< or = 5 mm or > 5 mm in diameter), location (central, peripheral, or abutting pleura or fissures), and attenuation (solid, calcified, or subsolid). Regions of interest were placed on the original images and transposed onto compressed images. Nodule volumes on original (noncompressed) and compressed images were measured by using a computer-assisted method. A mixed-model analysis of variance was conducted for statistical evaluation. RESULTS: Nodule volumes averaged 388.1 mm3 (range, 34-3474 mm3). There were three calcified, 33 solid noncalcified, and 15 subsolid nodules (13 with ground-glass attenuation). Average volume decreased with increasing compression level, to 383 mm3 (10:1), 370 mm3 (20:1), 360 mm3 (30:1), and 354 mm3 (40:1). No significant difference was identified between measurements obtained on original images and those compressed to a level of 10:1. Significant differences were noted, however, between original images and those compressed to a level of 20:1 or greater (P < .05). Compression level significantly interacted with nodule size, location, and attenuation (P < .001). The effect of compression was greater for nodules with ground-glass attenuation than for those with higher attenuation values. The difference in mean volumes between original images and those compressed to a level of 20:1 was 34.9 mm3 for nodules with ground-glass attenuation, compared with 8.3 mm3 for higher-attenuation nodules, a 4.2-fold difference. CONCLUSION: Nodule volumes measured on images compressed to a level of 20:1 differed significantly from those measured on noncompressed images, especially for nodules with ground-glass attenuation. This difference could affect the assessment of nodule change in size as measured with computer-assisted methods.

Adult↗
PubMed2001

The enhanced LBG algorithm.

Clustering applications cover several fields such as audio and video data compression, pattern recognition, computer vision, medical image recognition, etc. In this paper, we present a new clustering algorithm called Enhanced LBG (ELBG). It belongs to the hard and K-means vector quantization groups and derives directly from the simpler LBG. The basic idea we have developed is the concept of utility of a codeword, a powerful instrument to overcome one of the main drawbacks of clustering algorithms: generally, the results achieved are not good in the case of a bad choice of the initial codebook. We will present our experimental results showing the ELBG is able to find better codebooks than previous clustering techniques and the computational complexity is virtually the same as the simpler LBG.

Algorithms↗
PubMed2002

Current approach to radial nerve paralysis.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Identify all potential points of radial nerve compression and other likely causes of radial nerve injury. 2. Accurately diagnose both surgical and nonsurgical causes of radial nerve paralysis. 3. Define a safe and effective approach to the surgical release and reconstruction of the radial nerve. Radial nerve paralysis, which can result from a complex humerus fracture, direct nerve trauma, compressive neuropathies, neuritis, or (rarely) from malignant tumor formation, has been reported throughout the literature, with some controversy regarding its diagnosis and management. The appropriate management of any radial nerve palsy depends primarily on an accurate determination of its cause, severity, duration, and level of involvement. The radial nerve can be injured as proximally as the brachial plexus or as distally as the posterior interosseous or radial sensory nerve. This article reviews the etiology, prognosis, and various treatments available for radial nerve paralysis. It also provides a new classification system and treatment algorithm to assist in the management of patients with radial nerve palsies, and it offers a simple, five-step approach to radial nerve release in the forearm.

Algorithms↗
PubMed2004

Highly scalable video compression with scalable motion coding.

A scalable video coder cannot be equally efficient over a wide range of bit rates unless both the video data and the motion information are scalable. We propose a wavelet-based, highly scalable video compression scheme with rate-scalable motion coding. The proposed method involves the construction of quality layers for the coded sample data and a separate set of quality layers for the coded motion parameters. When the motion layers are truncated, the decoder receives a quantized version of the motion parameters used to code the sample data. The effect of motion parameter quantization on the reconstructed video distortion is described by a linear model. The optimal tradeoff between the motion and subband bit rates is determined after compression. We propose two methods to determine the optimal tradeoff, one of which explicitly utilizes the linear model. This method performs comparably to a brute force search method, reinforcing the validity of the linear model itself. Experimental results indicate that the cost of scalability is small. In addition, considerable performance improvements are observed at low bit rates, relative to lossless coding of the motion information.

Algorithms↗
PubMed2001

Computerized image analysis: estimation of breast density on mammograms.

An automated image analysis tool is being developed for the estimation of mammographic breast density. This tool may be useful for risk estimation or for monitoring breast density change in prevention or intervention programs. In this preliminary study, a data set of 4-view mammograms from 65 patients was used to evaluate our approach. Breast density analysis was performed on the digitized mammograms in three stages. First, the breast region was segmented from the surrounding background by an automated breast boundary-tracking algorithm. Second, an adaptive dynamic range compression technique was applied to the breast image to reduce the range of the gray level distribution in the low frequency background and to enhance the differences in the characteristic features of the gray level histogram for breasts of different densities. Third, rule-based classification was used to classify the breast images into four classes according to the characteristic features of their gray level histogram. For each image, a gray level threshold was automatically determined to segment the dense tissue from the breast region. The area of segmented dense tissue as a percentage of the breast area was then estimated. To evaluate the performance of the algorithm, the computer segmentation results were compared to manual segmentation with interactive thresholding by five radiologists. A "true" percent dense area for each mammogram was obtained by averaging the manually segmented areas of the radiologists. We found that the histograms of 6% (8 CC and 8 MLO views) of the breast regions were misclassified by the computer, resulting in poor segmentation of the dense region. For the images with correct classification, the correlation between the computer-estimated percent dense area and the "truth" was 0.94 and 0.91, respectively, for CC and MLO views, with a mean bias of less than 2%. The mean biases of the five radiologists' visual estimates for the same images ranged from 0.1% to 11%. The results demonstrate the feasibility of estimating mammographic breast density using computer vision techniques and its potential to improve the accuracy and reproducibility of breast density estimation in comparison with the subjective visual assessment by radiologists.

Biophysical Phenomena↗
PubMed1990

ECG data compression techniques--a unified approach.

A broad spectrum of techniques for electrocardiogram (ECG) data compression have been proposed during the last three decades. Such techniques have been vital in reducing the digital ECG data volume for storage and transmission. These techniques are essential to a wide variety of applications ranging from diagnostic to ambulatory ECG's. Due to the diverse procedures that have been employed, comparison of ECG compression methods is a major problem. Present evaluation methods preclude any direct comparison among existing ECG compression techniques. The main purpose of this paper is to address this issue and to establish a unified view of ECG compression techniques. ECG data compression schemes are presented in two major groups: direct data compression and transformation methods. The direct data compression techniques are: ECG differential pulse code modulation and entropy coding, AZTEC, Turning-point, CORTES, Fan and SAPA algorithms, peak-picking, and cycle-to-cycle compression methods. The transformation methods briefly presented, include: Fourier, Walsh, and K-L transforms. The theoretical basis behind the direct ECG data compression schemes are presented and classified into three categories: tolerance-comparison compression, differential pulse code modulation (DPCM), and entropy coding methods. The paper concludes with the presentation of a framework for evaluation and comparison of ECG compression schemes.

Algorithms↗
PubMed2005

A novel noncontact ultrasound indentation system for measurement of tissue material properties using water jet compression.

This study is aimed to develop a novel noncontact ultrasonic indentation system for measuring quantitative mechanical properties of soft tissues, which are increasingly important for tissue assessment and characterization. The key idea of this method is to use a water jet as an indenter to compress the soft tissue while at the same time as a medium for an ultrasound beam to propagate through. The use of water jet indentation does not require a rigid compressor in front of the focused high frequency ultrasound transducer to compress the tissue, so that the additional attenuation caused by the rigid compressor and the strong echoes reflected from its surfaces can be avoided. The indentation deformation was estimated from the ultrasound echoes using a cross-correlation algorithm and the indentation force was calculated from the water pressure measured inside the water pipe. Experiments were performed on uniform tissue-mimicking phantoms with different stiffness. The Young's moduli and Poisson's ratios of these phantoms were measured using a uniaxial ultrasound compression system. The ratio of the indentation pressure to the tissue relative deformation was obtained from the water indentation. This ratio was well correlated with the Young's modulus (r = 0.87). The results also demonstrated that the water indentation approach could differentiate materials with different stiffness in a combined phantom (288 kPa and 433 kPa). This novel noncontact water indentation approach could be potentially used for the measurement of the elasticity of small samples and with a fast scanning speed.

Algorithms↗
PubMed2006

On the mathematical reconstruction of two dimensional plants.

A set of 10, chosen medicinal plants (some of them with a reputation as remedies for tuberculosis) has been investigated through Partitioned Iterated Function Systems-Semi Fractals with Angle (PIFS-SFA) coding, Lempel, Ziv, Welch with quantization and noise (LZW-QN) compression, and surface density statistics (f(alpha)-SDS) discrimination techniques. The final outcomes of this quantitative analysis were, firstly: the linear ordering of the plants in question accompanied by the hope that it reflects their medical significance, secondly: the mathematical representation of each of the plants, and thirdly: the impressive compression achieved, leading to remarkable computer memory saving, and still permitting successful pattern recognition i.e., proper identification of the plant from the compressed image.

Algorithms↗
PubMed2004

Dual domain watermarking for authentication and compression of cultural heritage images.

This paper proposes an approach for the combined image authentication and compression of color images by making use of a digital watermarking and data hiding framework. The digital watermark is comprised of two components: a soft-authenticator watermark for authentication and tamper assessment of the given image, and a chrominance watermark employed to improve the efficiency of compression. The multipurpose watermark is designed by exploiting the orthogonality of various domains used for authentication, color decomposition and watermark insertion. The approach is implemented as a DCT-DWT dual domain algorithm and is applied for the protection and compression of cultural heritage imagery. Analysis is provided to characterize the behavior of the scheme under ideal conditions. Simulations and comparisons of the proposed approach with state-of-the-art existing work demonstrate the potential of the overall scheme.

Algorithms↗
PubMed2005

Early detection and treatment of spinal cord compression.

Several key areas must be considered in the diagnosis and management of spinal cord compression. Because the outcome can be devastating, a diagnosis must be made early and treatment initiated promptly. Although any malignancy can metastasize to the spine, clinicians should be aware that this occurs more commonly in certain diseases, i.e., lung cancer, breast cancer, prostate cancer, and myeloma. The current algorithm for early diagnosis of spinal cord compression involves neurologic assessment and magnetic resonance imaging of the entire spine. Treatment generally consists of intravenous dexamethasone followed by oral dosing. Depending on the extent of the metastases, symptoms may also be managed with nonnarcotic pain medicines, anti-inflammatory medications, and/or bisphosphonates, with local radiation administered as needed. Surgery has often led to destabilization of the spine.

Administration, Oral↗
PubMed2004

Noise reduction using spatial-angular compounding for elastography.

Ultrasound elastography has developed into an imaging modality suitable for detection and diagnosis of cancers in the breast, prostate, and thyroid and for monitoring ablative therapies in the liver, kidneys, and other sites. In this article, a new approach is described that enables the reduction of noise artifacts in elastography without a significant reduction in either the contrast or spatial resolution. The technique uses angular-weighted compounding of local angular strains estimated from echo signals scanned at different insonification angles. Strain estimated along angular insonification directions can be separated into strain tensor components along the axial (direction of compression) and lateral directions. The mechanical stimulus is applied only along one direction. Angular-weighting factors are derived from the relationship between the axial and lateral strains under the assumption of tissue incompressibility. Experimental results using a uniformly elastic, tissue-mimicking phantom demonstrate the improvement in the signal-to-noise ratio obtained with angular-weighted compounding. Variation in the signal-to-noise ratio obtained using different angular increments also is investigated. Elastograms obtained from an inclusion phantom also demonstrate the improvement in contrast detail resolution obtained using spatial-angular compounding.

Algorithms↗
PubMedDate not supplied

Data predictability for compression of digital fluorography images.

Images obtained by digital fluorography were checked for compressability. These images include images of coronary vessels and images of peripheral vessels. These images have a very low signal-to-noise ratio compared to the optical images usually used for developing compression methods. Configurational entropy was used to represent the information content of these images. Reversible prediction algorithms were extensively checked in a search for minimal residual information, enabling more efficient reversible compression. Optimal results were obtained for algorithms based on two or three neighboring pixels and a semiempirical rule, based on the noise level, was found which decides on the best approach. It was found that raw data images are more predictable than subtracted images although the latter are visually preferred.

Algorithms↗