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PubMed2004

Design of signal-adapted multidimensional lifting scheme for lossy coding.

This paper proposes a new method for the design of lifting filters to compute a multidimensional nonseparable wavelet transform. Our approach is stated in the general case, and is illustrated for the 2-D separable and for the quincunx images. Results are shown for the JPEG2000 database and for satellite images acquired on a quincunx sampling grid. The design of efficient quincunx filters is a difficult challenge which has already been addressed for specific cases. Our approach enables the design of less expensive filters adapted to the signal statistics to enhance the compression efficiency in a more general case. It is based on a two-step lifting scheme and joins the lifting theory with Wiener's optimization. The prediction step is designed in order to minimize the variance of the signal, and the update step is designed in order to minimize a reconstruction error. Application for lossy compression shows the performances of the method.

Algorithms↗
PubMedDate not supplied

Applications of Forman's discrete Morse theory to topology visualization and mesh compression.

Morse theory is a powerful tool for investigating the topology of smooth manifolds. It has been widely used by the computational topology, computer graphics, and geometric modeling communities to devise topology-based algorithms and data structures. Forman introduced a discrete version of this theory which is purely combinatorial. This work aims to build, visualize, and apply the basic elements of Forman's discrete Morse theory. It intends to use some of those concepts to visually study the topology of an object. As a basis, an algorithmic construction of optimal Forman's discrete gradient vector fields is provided. This construction is then used to topologically analyze mesh compression schemes, such as Edgebreaker and Grow&Fold. In particular, this paper proves that the complexity class of the strategy optimization of Grow&Fold is MAX-SNP hard.

Algorithms↗
PubMed2003

Development of a three-dimensional finite element model for carpal load transmission in a static neutral posture.

A three-dimensional developmental finite element model has been created to analyze load transmission pathways in the constrained carpus during static compressive loading. The bone geometry was extracted from an in vivo computed tomography scan using a combination of commercial and proprietary software. The complete geometry, including bone, cartilage, and ligament tissues, was compiled using a commercial finite element program. This model extends the state of biomechanical modeling by being the first to incorporate all eight carpal bones of the wrist and the related soft tissues in three dimensions. The model results indicate that cartilage material modulus and unconstrained carpal rotation have substantial impacts on the articular contact patterns and pressures.

Algorithms↗
PubMed2002

An iterative method for viscoelastic modeling of prosthetic feet.

Prosthetic foot designs are growing in complexity, but a few material and structural properties, including stiffness and viscoelasticity, remain critical to foot function. Consistent identification of these critical properties would aid prosthesis prescription. This investigation evaluates a new technique to model prosthetic feet as a combination of springs and dampers, and therefore characterize a foot's stiffness and viscoelasticity by means of spring and damper coefficients. A quasi-Newton iterative algorithm was developed to determine model coefficients for 9 prosthetic feet based on compressive creep, stress-relaxation, and constant strain rate tests. A broad range of current energy-storing feet including designs from Otto Bock, Seattle, Kingsley, and Ohio Willow Wood were very accurately modeled with the iterative technique. Feet without a solid ankle from Flex and College Park were the least accurately modeled. The Flex foot, tested without a cover, had a considerably lower damping coefficient. Damper coefficients were similar for most all other feet, suggesting similar material properties of the foam cover. Stiffness varied and generally agreed with published data. The ability of the model to produce two separate parallel spring stiffness constants might provide insight into foot structure. The model represents a means to objectively quantify material properties for a range of solid ankle dynamic elastic response prosthetic feet, but may be limited in its characterization of other foot varieties.

Algorithms↗
PubMed2002

Dynamic image data compression in the spatial and temporal domains: clinical issues and assessment.

In our previous work, we developed a novel approach to dynamic image data compression, and demonstrated that very high compression ratios can be achieved while preserving relevant kinetic information. However, the technique has not yet been assessed with clinical data. Many issues need to be addressed to tailor the method for clinical use. In this paper, we apply the compression technique to dynamic [18F] 2-fluoro-deoxy-glucose (FDG) brain positron emission tomography (PET) data, using a five-parameter model to include cerebral blood volume (CBV) and partial volume (PV) effects. Functional images generated from the compressed data are compared with those from the original uncompressed data. We show that the storage requirements for a typical clinical dynamic PET image data set can be reduced by more than 95%, without degradation of image quality. Furthermore, the technique greatly reduces the computational complexity of further clinical image postprocessing such as smoothing and generation of functional images. It is expected that the compression technique will be of benefit in image data management and telemedicine.

Algorithms↗
PubMed2006

Compressive properties of mouse articular cartilage determined in a novel micro-indentation test method and biphasic finite element model.

The mechanical properties of articular cartilage serve as important measures of tissue function or degeneration, and are known to change significantly with osteoarthritis. Interest in small animal and mouse models of osteoarthritis has increased as studies reveal the importance of genetic background in determining predisposition to osteoarthritis. While indentation testing provides a method of determining cartilage mechanical properties in situ, it has been of limited value in studying mouse joints due to the relatively small size of the joint and thickness of the cartilage layer. In this study, we developed a micro-indentation testing system to determine the compressive and biphasic mechanical properties of cartilage in the small joints of the mouse. A nonlinear optimization program employing a genetic algorithm for parameter estimation, combined with a biphasic finite element model of the micro-indentation test, was developed to obtain the biphasic, compressive material properties of articular cartilage. The creep response and material properties of lateral tibial plateau cartilage were obtained for wild-type mouse knee joints, by the micro-indentation testing and optimization algorithm. The newly developed genetic algorithm was found to be efficient and accurate when used with the finite element simulations for nonlinear optimization to the experimental creep data. The biphasic mechanical properties of mouse cartilage in compression (average values: Young's modulus, 2.0 MPa; Poisson's ratio, 0.20; and hydraulic permeability, 1.1 x 10(-16) m4/N-s) were found to be of similar orders of magnitude as previous findings for other animal cartilages, including human, bovine, rat, and rabbit and demonstrate the utility of the new test methods. This study provides the first available data for biphasic compressive properties in mouse cartilage and suggests a promising method for detecting altered cartilage mechanics in small animal models of osteoarthritis.

Animals↗
PubMed2003

To blow or not to blow: a randomised controlled trial of compression-only and standard telephone CPR instructions in simulated cardiac arrest.

This randomised controlled trial used a manikin model of cardiac arrest to compare skill performance in untrained lay persons randomised to receive either compression-only telephone CPR (Compression-only tel., n=29) or standard telephone CPR instructions (Standard tel., n=30). Performance was evaluated during standardised 10 min cardiac arrest simulations using a video recording and data from a laptop computer connected to the training manikin. A number of subjects in both groups did not open the airway. More than 75% in the Standard tel. group failed to deliver two effective initial rescue breaths, and only 17% provided an adequate inflation volume for subsequent breaths, delivering a median of only five inflations during the entire scenario. Most subjects in both groups gave chest compressions that were too shallow and at an inappropriately rapid rate. Hand position was also poor, but was worse in the group given simplified instructions. There was a significant delay to first compression in both groups, although this interval was shortened by over a minute when ventilations were eliminated from the telephone instruction algorithm (245 vs. 184 s, P<0.001). Over two-and-a-half times as many chest compressions were delivered during an average ambulance response time with compression-only telephone directions compared with standard CPR (461 vs. 186, P<0.001). These variables may be critical in predicting survival from out-of-hospital cardiac arrest. Further research is necessary to establish if modifications to scripted telephone instructions can remedy the identified performance deficiencies. Eliminating instructions for rescue breaths from scripted telephone directions will have little impact on the ventilation of most patients. Research is required to determine if the consequent reduction in the delay to starting chest compressions and the significant increase in the number of compressions delivered can increase survival from out-of-hospital cardiac arrest.

Adult↗
PubMed2002

Medical image compression by sampling DCT coefficients.

Advanced medical imaging requires storage of large quantities of digitized clinical data. Due to the constrained bandwidth and storage capacity, however, a medical image must be compressed before transmission and storage. Among the existing compression schemes, transform coding is one of the most effective strategies. Image data in spatial domain will be transformed into spectral domain after the transformation to attain more compression gains. Based on the quantization strategy, coefficients of low amplitude in the transformed domain are discarded and significant coefficients are preserved to increase the compression ratio without inducing salient distortion. In this paper, we use an adaptive sampling algorithm by calculating the difference area between correct points and predicted points to decide the significant coefficients. Recording or transmitting the significant coefficients instead of the whole coefficients achieves the goal of compression. On the decoder side, a linear equation is employed to reconstruct the coefficients between two sequent significant coefficients. Simulations are carried out to different medical images, which include sonogram, angiogram, computed tomography, and X-ray images. Consequent images demonstrate the performance at compression ratios of 20-45 without perceptible alterations. In addition, two doctors are invited to verify that the decoded quality is acceptable for practical diagnosis. Therefore, our proposed method is found to preserve information fidelity while reducing the amount of data.

Algorithms↗
PubMed1998

Non-linear signal processing in digital hearing aids.

Three different non-linear digital signal processing algorithms were developed; LinEar, DynEar and RangeEar. All three provided individual frequency shaping via a seven-band low-power filterbank and compression in two channels. RangeEar and DynEar used wide dynamic range syllabic compression in the low-frequency (LF) channel, while LinEar used compression limiting. In the high-frequency (HF) channel, RangeEar used a slow-acting automatic volume control, while DynEar and LinEar used compression limiting. Wearable digital signal processing-based experimental instruments were used to evaluate the fitting algorithms under real world conditions with experienced hearing aid users. Evaluation included laboratory testing of speech recognition in noise and questionnaires on sound quality ratings. Results did not indicate one general good-for-all algorithm, but different algorithms resulting in preference and performance depending on the hearing loss configuration. Preference for any of the new algorithms could be predicted based on auditory dynamic range measurements. It was hypothesized that the different preferences were affected by different susceptibility to masking of HF sounds by amplified LF sounds.

Adult↗
PubMed1995

DMSO resolves certain compressions and signal dropouts in fluorescent dye labeled primer-based DNA sequencing reactions.

Automated base calling algorithms are more sensitive to the quality of the DNA sequencing data than are the labor intensive visual methods of base calling. To improve this quality, data from DNA sequencing reactions have been compared in order to determine the effects of the inclusion of dimethyl sulfoxide (DMSO). Inclusion of 10% DMSO into the reaction cocktail resolves at least one type of sequence compression. This compression may be due to the lack of ability in T7 DNA polymerase to read through certain sequences correctly. The poor quality of these data is seen as radioactive bands or fluorescent signal peaks that have an abnormal alignment, either in the wrong order or as single bands/peaks. The inclusion of DMSO also resolves sequences where the peak signal is absent or severely diminished, leading to a "gap" in the chromatogram profile. DMSO is better than deaza-dITP for resolving certain compressions. Addition of DMSO is a cheaper and more efficient method for high-throughput DNA sequencing than repeating reactions with base analogs.

Algorithms↗
PubMed1992

Special problems in the older cancer patient: spinal cord compression and pleural effusions.

Spinal cord compression due to epidural metastases, and malignant pleural effusions are devastating complications of advanced cancer that can destroy the quality of a life that is already limited in quantity. Neither need do so. A diagnostic algorithm has been developed for each of these complications. Early diagnosis of cord compression can be accomplished by prompt myelography or magnetic resonance imaging of the affected area of the spine. A malignant pleural effusion, even one that initially appears cytologically negative, can be promptly diagnosed. Radiation and steroids are optimal therapy for most patients with cord compression, and few require surgery. Intrapleural bleomycin appears to be the most effective agent for pleurodesis.

Aging↗
PubMed2006

A compression-based approach for coding sequences identification. I. Application to prokaryotic genomes.

Most of the gene prediction algorithms for prokaryotes are based on Hidden Markov Models or similar machine-learning approaches, which imply the optimization of a high number of parameters. The present paper presents a novel method for the classification of coding and non-coding regions in prokaryotic genomes, based on a suitably defined compression index of a DNA sequence. The main features of this new method are the non-parametric logic and the costruction of a dictionary of words extracted from the sequences. These dictionaries can be very useful to perform further analyses on the genomic sequences themselves. The proposed approach has been applied on some prokaryotic complete genomes, obtaining optimal scores of correctly recognized coding and non-coding regions. Several false-positive and false-negative cases have been investigated in detail, which have revealed that this approach can fail in the presence of highly structured coding regions (e.g., genes coding for modular proteins) or quasi-random non-coding regions (e.g., regions hosting non-functional fragments of copies of functional genes; regions hosting promoters or other protein-binding sequences). We perform an overall comparison with other gene-finder software, since at this step we are not interested in building another gene-finder system, but only in exploring the possibility of the suggested approach.

Algorithms↗
PubMed2006

Diagnosis and treatment of deep-vein thrombosis.

Deep-vein thrombosis (DVT) is a common condition that can lead to complications such as postphlebitic syndrome, pulmonary embolism and death. The approach to the diagnosis of DVT has evolved over the years. Currently an algorithm strategy combining pretest probability, D-dimer testing and compression ultrasound imaging allows for safe and convenient investigation of suspected lower-extremity thrombosis. Patients with low pretest probability and a negative D-dimer test result can have proximal DVT excluded without the need for diagnostic imaging. The mainstay of treatment of DVT is anticoagulation therapy, whereas interventions such as thrombolysis and placement of inferior vena cava filters are reserved for special situations. The use of low-molecular-weight heparin allows for outpatient management of most patients with DVT. The duration of anticoagulation therapy depends on whether the primary event was idiopathic or secondary to a transient risk factor. More research is required to optimally define the factors that predict an increased risk of recurrent DVT to determine which patients can benefit from extended anticoagulant therapy.

Algorithms↗
PubMed2006

Texture characterization for joint compression and classification based on human perception in the wavelet domain.

Today's multimedia applications demand sophisticated compression and classification techniques in order to store, transmit, and retrieve audio-visual information efficiently. Over the last decade, perceptually based image compression methods have been gaining importance. These methods take into account the abilities (and the limitations) of human visual perception (HVP) when performing compression. The upcoming MPEG 7 standard also addresses the need for succinct classification and indexing of visual content for efficient retrieval. However, there has been no research that has attempted to exploit the characteristics of the human visual system to perform both compression and classification jointly. One area of HVP that has unexplored potential for joint compression and classification is spatial frequency perception. Spatial frequency content that is perceived by humans can be characterized in terms of three parameters, which are: 1) magnitude; 2) phase; and 3) orientation. While the magnitude of spatial frequency content has been exploited in several existing image compression techniques, the novel contribution of this paper is its focus on the use of phase coherence for joint compression and classification in the wavelet domain. Specifically, this paper describes a human visual system-based method for measuring the degree to which an image contains coherent (perceptible) phase information, and then exploits that information to provide joint compression and classification. Simulation results that demonstrate the efficiency of this method are presented.

Algorithms↗
PubMed2006

Oriented wavelet transform for image compression and denoising.

In this paper, we introduce a new transform for image processing, based on wavelets and the lifting paradigm. The lifting steps of a unidimensional wavelet are applied along a local orientation defined on a quincunx sampling grid. To maximize energy compaction, the orientation minimizing the prediction error is chosen adaptively. A fine-grained multiscale analysis is provided by iterating the decomposition on the low-frequency band. In the context of image compression, the multiresolution orientation map is coded using a quad tree. The rate allocation between the orientation map and wavelet coefficients is jointly optimized in a rate-distortion sense. For image denoising, a Markov model is used to extract the orientations from the noisy image. As long as the map is sufficiently homogeneous, interesting properties of the original wavelet are preserved such as regularity and orthogonality. Perfect reconstruction is ensured by the reversibility of the lifting scheme. The mutual information between the wavelet coefficients is studied and compared to the one observed with a separable wavelet transform. The rate-distortion performance of this new transform is evaluated for image coding using state-of-the-art subband coders. Its performance in a denoising application is also assessed against the performance obtained with other transforms or denoising methods.

Algorithms↗
PubMed2002

Hair-MAP: a prototype automated system for forensic hair comparison and analysis.

This paper demonstrates the feasibility of the automation of forensic hair analysis and comparison task using neural network explanation systems (NNESs). Our system takes as input microscopic images of two hairs and produces a classification decision as to whether or not the hairs came from the same person. Hair images were captured using a NEXTDimension video board in a NEXTDimension color turbo computer, connected to a video camera. Image processing was done on an SGI indigo workstation. Each image is segmented into a number of pieces appropriate for classification of different features. A variety of image processing techniques are used to enhance this information. Use of wavelet analysis and the Haralick texture algorithm to pre-process data has allowed us to compress large amounts of data into smaller, yet representative data. Neural networks are then used for feature classification. Finally, statistical tests determine the degree of match between the resulting collection of hair feature vectors. An important issue in automation of any task in criminal investigations is the reliability and understandability of the resulting system. To address this concern, we have developed methods to facilitate explanation of neural network's behavior using a decision tree. The system was able to achieve a performance of 83% hair match accuracy, using 5 of the 21 morphological characteristics used by experts. This shows promise for the usefulness of a fuller scale system. While an automated system would not replace the expert, it would make the task easier by providing a means for pre-processing the large amount of data with which the expert must contend.

Algorithms↗