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At least 217 records · Page 12Linked to original sources
PubMed1995

Design of an emergency teleradiology system based on progressive transmission.

In clinical surgery, there are frequent needs for communication between the house staff and the attending physician in an emergency situation. To overcome the limitation of voice communication through the telephone line, we have designed an 'emergency teleradiology system' which can be used for emergency surgical and medical decision making. This system can transmit the high quality images of CT, MRI, and other X-ray data using a PC attached to a modem through the conventional telephone line. It is based on the progressive transmission system which enables the successive update of a received image. The iterative residual coding/decoding algorithm efficiently compresses the image to maximally utilize the low bandwidth PSTN channels. This system also satisfies design requirements such as low-cost, ease of operation, fast transmission, and interactive image communication including voice. Test results using several CT, MR, and X-ray images evaluate the compression performance, image quality, transmission time and computational time of the coding and decoding processes, thus demonstrate the usefulness of this system in an emergency situation.

Algorithms↗
PubMed2004

Lossless compression of volumetric medical images with improved three-dimensional SPIHT algorithm.

This article presents a lossless compression of volumetric medical images with the improved three-dimensional (3-D) set partitioning in hierarchical tree (SPIHT) algorithm that searches on asymmetric trees. The tree structure links wavelet coefficients produced by 3-D reversible integer wavelet transforms. Experiments show that the lossless compression with the improved 3-D SPIHT gives improvement about 42% on average over two-dimensional techniques and is superior to those of prior results of 3-D techniques. In addition, we can easily apply different numbers of decomposition between the transaxial and axial dimensions, which is a desirable function when the coding unit of a group of slices is limited in size.

Adolescent↗
PubMed1995

ECG compression using Ziv-Lempel techniques.

The strong regularity in an ECG recording suggests that data compression techniques based on finding and efficiently coding repetitions in the data are likely to be effective. It is shown how the LZ77 compression method due to Ziv and Lempel can be adapted to ECG compression. Experimental results show the new algorithm to be highly effective. Some enhancements to the basic compression algorithm to reduce noise in the decompressed trace are described and experimentally verified.

Algorithms↗
PubMed1986

Image transmission and data compression. Two key elements of an electronic imaging department.

Growing numbers of diagnostic images are being produced electronically and filmed only for storage, or sometimes also for interpretation. However, in most imaging centers, transmission of images from one location to another is still being accomplished manually. Almost 40 years ago, x-rays were first transmitted over telephone lines, and this form of "teleradiology" has been increasingly used to link isolated hospitals and clinics to larger facilities so that radiologists can interpret the images. Continuing improvement of the various electronic image-processing technologies has produced faster means of transmission, and increasingly sophisticated computer algorithms for "compressing" the image data have further improved both transmission speed and the quality of the transmitted images. To date, only a few imaging research centers and teaching hospitals have integrated these techniques into a comprehensive picture archiving and communications system (PACS) or digital image management system (DIMS), and a number of factors are restraining these systems' spread. However, electronic transmission of images for interpretation by specialists at a central facility is likely to increase, and truly "filmless" radiology may someday become a reality, if image transmission and data compression techniques are eventually determined to create images of acceptable quality in all imaging modalities.

Computer Communication Networks↗
PubMed1999

Transverse/sigmoid sinus dural arteriovenous fistulas presenting as pulsatile tinnitus.

OBJECTIVE/HYPOTHESIS: Transverse/sigmoid sinus dural arteriovenous fistula (TSDAVF) is a diagnostically elusive entity that is critical for the otologist to account for, when confronted by pulsatile tinnitus in the face of normal otoscopy. Left untreated, TSDAVF may result in catastrophic outcome. We have previously proposed a grading system specifically for TSDAVF based on venous restrictive disease. Our objective was to assess the validity of this grading system for clinical severity and therapeutic outcome. METHODS: Through a retrospective review of 41 patients with TSDAVF, we evaluated clinical presentation, diagnostic evaluation, therapy, and outcome. Patients were classified into four grades based on the severity of venous restrictive disease as determined by superselective angiography. Our treatment algorithm combined compression therapy, transarterial embolization, and for more severe grades, surgery. RESULTS: Pulsatile tinnitus was the chief complaint of all the patients in this series, and of 90% of all cases of TSDAVF treated at our institution. While angiography remains the gold standard, magnetic resonance imaging/magnetic resonance arteriography is far superior to computed tomography scanning in detecting dural arteriovenous fistulas. As normal venous outflow gives way to aberrant cortical venous drainage in higher grades, there is a dramatically increased risk for adverse consequences with therapeutic intervention. Using our treatment algorithm, 82% of patients achieved clinical resolution of symptoms. Half of these patients had complete angiographic obliteration of their TSDAVF. CONCLUSIONS: The TSDAVF-specific grading system for the severity of venous restrictive disease is reflective of clinical presentation, fundamental in planning treatment, and predictive of therapeutic outcome.

Adolescent↗
PubMed2003

Numerical simulations on fatigue destruction of ultra-high molecular weight polyethylene using discrete element analyses.

Ultra-high molecular weight polyethylene (UHMWPE) is a heterogeneous material composed of a networked substructure of grain boundary and grain aggregation. A new numerical model based on the discrete element method (DEM) was proposed to examine microscopic defect formation and propagation in UHMWPE. Numerical simulations were carried out using this model under two types of loading condition: unidirectional repetitive compression (simple loading) and bidirectional repetitive compression (switched loading). Subsurface defects were initiated and propagated in the vicinity of grain boundaries under both loading conditions. The defect propagation behavior was especially sensitive to grain boundary allocation under switched loading. An increase in defects was more rapid under switched loading than under simple loading. These numerical results showed qualitatively good agreement with experimental ones. It is suggested that the newly developed numerical method based on the DEM is a promising method to investigate fatigue behavior of a heterogeneous material such as UHMWPE under complicated loading conditions.

Algorithms↗
PubMed2004

The effect of tibial curvature and fibular loading on the tibia index.

The tibia index (TI) is commonly used to predict leg injury based on measurements taken by an anthropomorphic test device (ATD). The TI consists of an interaction formula that combines axial loading and bending plus a supplemental compressive force criterion. Current ATD lower limbs lack geometric biofidelity with regard to tibial curvature and fibular load-sharing. Due to differences in tibial curvature, the midshaft moments induced by axial loading are different in humans and ATDs. Midshaft tibial loading in the human is also reduced by load-sharing through the fibula, which is not replicated in current ATDs. In this study, tibial curvature and fibular load-sharing are quantified through CT imaging and biomechanical testing, and equations are presented to correct ATD measurements to reflect the loading that would be experienced by a human tibia.

Adult↗
PubMed2003

Meshfree representation and computation: applications to cardiac motion analysis.

For medical image analysis issues where the domain mappings between images involve large geometrical shape changes, such as the cases of nonrigid motion recovery and inter-object image registration, the finite element methods exhibit considerable loss of accuracy when the elements in the mesh become extremely skewed or compressed. Therefore, algorithmically difficult and computationally expensive remeshing procedures must be performed in order to alleviate the problem. We present a general representation and computation framework which is purely based on the sampling nodal points and does not require the construction of mesh structure of the analysis domain. This meshfree strategy can more naturally handle very large object deformation and domain discontinuity problems. Because of its intrinsic h-p adaptivity, the meshfree framework can achieve desired numerical accuracy through adaptive node and polynomial shape function refinement with minimum extra computational expense. We focus on one of the more robust meshfree efforts, the element free Galerkin method, through the moving least square approximation and the Galerkin weak form formulation, and demonstrate its relevancy to medical image analysis problems. Specifically, we show the results of applying this strategy to physically motivated multiframe motion analysis, using synthetic data for accuracy assessment and for comparison to finite element results, and using canine magnetic resonance tagging and phase contrast images for cardiac kinematics recovery.

Algorithms↗
PubMedDate not supplied

A client/server system for Internet access to biomedical text/image databanks.

Internet access to mixed text/image databanks is finding application in the medical world. An example is a database of medical X-rays and associated data consisting of demographic, socioeconomic, physician's exam, medical laboratory and other information collected as part of a nationwide health survey conducted by the government. Another example is a collection of digitized cryosection images, CT and MR taken of cadavers as part of the National Library of Medicine's Visible Human Project. In both cases, the challenge is to provide access to both the image and the associated text for a wide end user community to create atlases, conduct epidemiological studies, to develop image-specific algorithms for compression, enhancement and other types of image processing, among many other applications. The databanks mentioned above are being created in prototype form. This paper describes the prototype system developed for the archiving of the data and the client software to enable a broad range of end users to access the archive, retrieve text and image data, display the data and manipulate the images. System design considerations include; data organization in a relational database management system with object-oriented extensions; a hierarchical organization of the image data by different resolution levels for different user classes; client design based on common hardware and software platforms incorporating SQL search capability, X Window, Motif and TAE (a development environment supporting rapid prototyping and management of graphic-oriented user interfaces); potential to include ultra high resolution display monitors as a user option; intuitive user interface paradigm for building complex queries; and contrast enhancement, magnification and mensuration tools for better viewing by the user.

Anatomy, Cross-Sectional↗
PubMed2026

FFC: a scalable FASTA compressor.

SUMMARY: FASTA is a widely used text-based format for storing nucleotide and protein sequences. The existing FASTA compressors usually focus on (slightly) improving the compression ratio, not on practical performance. We present FFC, a scalable FASTA compressor that achieves average compression speeds 4.7× and 11.4× higher than two high-performance compressors, zstd and NAF, respectively, across a benchmark set of seven single genomes. It also delivers average decompression speeds 3.5× and 2.7× higher than zstd and NAF, respectively. Although a chunk-based zstd variant with parallel decompression, pzstd, almost matches FFC speed, its compression ratio is on average by 23% worse than FFC's. For the experiment, a 14-core workstation and a RAM disk (to reduce the impact of I/O) were used. AVAILABILITY AND IMPLEMENTATION: FFC is freely available at github.com/kowallus/ffc and also as a Zenodo repository at 10.5281/zenodo.18892353, and the used datasets at 10.5281/zenodo.18873744.

Data Compression↗
PubMed2006

Reconstructions of shear modulus, Poisson's ratio, and density using approximate mean normal stress lambda epsilon alpha alpha as unknown.

As a differential diagnosis technique for living soft tissues, we are developing ultrasonic-strain-measurement-based shear modulus reconstruction methods. Previously, we reported three-dimensional (3-D) and 2-D reconstruction methods utilizing a typical Poisson's ratio very close to 0.5 (nearly-incompressible). However, because a decrease in the accuracy of the reconstructed value was confirmed to be due to the difference between the original value and the set value, we proposed 3-D and 2-D methods of reconstructing Poisson's ratio as well. Furthermore, we proposed methods of reconstructing density and dealing with dynamic deformation. However, due to tissue incompressibility, the reconstructions of shear modulus, Poisson's ratio, and density became unstable. In this report, to obtain stable, unique reconstructions, we describe a new reconstruction method using mean normal stress approximated by the product of one of Lame's constants X and volume strain epsilon alpha alpha as an unknown. Regularization is simultaneously applied to the respective distributions to decrease the instability of the reconstructions due to measurement errors of the deformation. This method also enables stable, unique reconstructions of shear modulus and density under the condition that the mean normal stress remains unknown. We also verify the effectiveness of this method through 3-D simulations, while showing erroneous artifacts occurring when 2-D and 1-D reconstructions are performed.

Algorithms↗
PubMed2004

Potential theory method for 3D crack and contact problems of multi-field coupled media: a survey.

This paper presents an overview of the recent progress of potential theory method in the analysis of mixed boundary value problems mainly stemming from three-dimensional crack or contact problems of multi-field coupled media. This method was used to derive a series of exact three dimensional solutions which should be of great theoretical significance because most of them usually cannot be derived by other methods such as the transform method and the trial-and-error method. Further, many solutions are obtained in terms of elementary functions that enable us to treat more complicated problems easily. It is pointed out here that the method is usually only applicable to media characterizing transverse isotropy, from which, however, the results for the isotropic case can be readily obtained.

Algorithms↗
PubMedDate not supplied

[Simulation models of the processes of the interface in dental structures].

The occlusal forces have an effect on the dental structure in the longitudinal axis of the tooth, on the one hand, but, on the other hand, in the horizontal plane, they are conducted through interdental contact points. In this paper we try to simulate the stress and the deformations determined by different forces in different directions, over the dental interfaces. We have used the method of finite elements and Fastflo domain for the mathematical calculations of probability. Our conclusions are that the changes in the deformation field appear only for those materials that comply with the rate of elasticity changes in the condition where delta = E1/E2 < 20.

Algorithms↗
PubMed1993

ECG compression using long-term prediction.

A new algorithm for ECG signal compression is introduced. The compression system is based on the subautoregression (SAR) model, known also as the long-term prediction (LTP) model. The "periodicity" of the ECG signal is employed in order to further reduce redundancy, thus yielding high compression ratios. The suggested algorithm was evaluated using an in-house database. Very low bit rates on the order of 70 b/s are achieved with a relatively low reconstruction error (percent rms difference-PRD) of less than 10%. The algorithm was compared, using the same database, with the conventional linear prediction (short-term prediction--STP) method, and was found superior at any bit rate. The suggested algorithm can be considered a generalization of the recently published average beat subtraction method.

Algorithms↗
PubMed2000

Hadamard-based image decomposition and compression.

In this paper, we develop a general algorithm for decomposition and compression of grayscale images. The decomposition can be expressed as a functional relation between the original image and the Hadamard waveforms. The dynamic adaptive clustering procedure incorporates potential functions as a similarity measure for clustering as well as a reclustering phase. The latter is a multi-iteration, convergent procedure which divides the inputs into nonoverlapping clusters. These two techniques allow us to efficiently store and transmit a class of half-tone medical images such as magnetic resonance imaging (MRI) of the human brain. Due to the redundant image structure of MRI, obtained after the decomposition and clustering, almost half of the image can be omitted all together. Naturally, the compression rates for this specific type of grayscale image are increased greatly. A run-length coding is performed in order to compress further the retained information from the first two steps. Although all the techniques applied are simple, they represent an efficient way to compress grayscale images. The algorithm exhibits a performance which is competitive and often outperforming some of the methods reported in the literature.

Algorithms↗
PubMed1996

Wavelet packet-based compression of single lead ECG.

A preliminary investigation of a wavelet packet based algorithm for the compression of single lead ECG is presented. The algorithm combines the efficiency and flexibility of wavelet packet expansions with the methodology of the Karhunen-Loeve transform (KLT). For selected records from the MIT-BIH arrhythmia database, an average data rate of 184.7 bits per second, corresponding to a compression ratio of 21.4 : 1, is achieved. When compared with the KLT applied to the same data, the wavelet packet algorithm generates significantly lower data rates with less than one-third the computational effort.

Algorithms↗
PubMed1992

An efficient algorithm for MR image reconstruction and compression.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Algorithms↗