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At least 613 records · Page 34Linked to original sources
PubMedDate not supplied

Mean square error approximation for wavelet-based semiregular mesh compression.

The objective of this paper is to propose an efficient model-based bit allocation process optimizing the performances of a wavelet coder for semiregular meshes. More precisely, this process should compute the best quantizers for the wavelet coefficient subbands that minimize the reconstructed mean square error for one specific target bitrate. In order to design a fast and low complex allocation process, we propose an approximation of the reconstructed mean square error relative to the coding of semiregular mesh geometry. This error is expressed directly from the quantization errors of each coefficient subband. For that purpose, we have to take into account the influence of the wavelet filters on the quantized coefficients. Furthermore, we propose a specific approximation for wavelet transforms based on lifting schemes. Experimentally, we show that, in comparison with a "naive" approximation (depending on the subband levels), using the proposed approximation as distortion criterion during the model-based allocation process improves the performances of a wavelet-based coder for any model, any bitrate, and any lifting scheme.

Algorithms↗
PubMed2005

Perceptual adaptive insensitivity for support vector machine image coding.

Support vector machine (SVM) learning has been recently proposed for image compression in the frequency domain using a constant epsilon-insensitivity zone by Robinson and Kecman. However, according to the statistical properties of natural images and the properties of human perception, a constant insensitivity makes sense in the spatial domain but it is certainly not a good option in a frequency domain. In fact, in their approach, they made a fixed low-pass assumption as the number of discrete cosine transform (DCT) coefficients to be used in the training was limited. This paper extends the work of Robinson and Kecman by proposing the use of adaptive insensitivity SVMs [2] for image coding using an appropriate distortion criterion [3], [4] based on a simple visual cortex model. Training the SVM by using an accurate perception model avoids any a priori assumption and improves the rate-distortion performance of the original approach.

Algorithms↗
PubMed2001

[Metastatic epidural spinal compression: prognostic factors and results of radiotherapy].

BACKGROUND: The metastatic epidural spinal cord compression is an oncologic emergency. Presently, there is no agreement on a standard diagnostic or therapeutic algorithm. In spite of improvement in diagnostic imaging, a great proportion of patients are plegic at the time of the first presentation. PATIENTS AND METHODS: Therapy charts of 53 consecutive patients--31 male and 22 female--with metastatic epidural spinal cord compression treated with radiation therapy only have been analyzed. Median age was 60 years. The most frequent primary tumors were bronchogenic carcinoma (13 patients), breast cancer (ten patients) and prostate cancer (ten patients). RESULTS: MRI was the most sensitive diagnostic tool in detecting spinal cord compression. Plain X-ray films were not useful. Pain symptoms were improved in 66% of the patients. The most important prognostic factor was the pretreatment mobility status. 94% of the ambulatory patients kept their walking ability, but only one plegic patient could walk again after radiation therapy (p < 0.001). Patients whose back pain was presented to an oncologist were more likely to keep their walking ability by the end of the therapy. Patients with bronchogenic cancer and plegic patients had a significantly worse survival. CONCLUSION: Patients with a known malignant tumor and progressive or axial back pain should undergo MRI scan to rule out spinal cord compression. For patients without severe neurologic deficit and MRI proven epidural compression, radiation therapy is able to preserve walking ability and reduce pain. For patients with neurologic symptoms radiation therapy should start within 24 hours.

Adenocarcinoma↗
PubMed1995

A dynamic Fourier series for the compression of ECG using FFT and adaptive coefficient estimation.

In this article, a new ECG data compression technique is proposed. The method relies on modelling quasi-periodic ECG signals as a dynamic Fourier series. Fourier coefficients are continuously estimated using either an FFT algorithm or the adaptive least mean square algorithm. Results from simulated normal and pathological ECGs are presented and discussed. The merits of each of the above two methods are also illustrated. Furthermore, a comparison with other compression techniques is also discussed.

Algorithms↗
PubMed2005

Modifications of orientational dependence of microscopic magnetic resonance imaging T(2) anisotropy in compressed articular cartilage.

PURPOSE: To investigate the compression-induced changes in the orientational characteristics in T(2) anisotropy of articular cartilage using microscopic magnetic resonance imaging (microMRI). MATERIALS AND METHODS: Six beagle specimens were subjected to various levels of strain (0% to 27%) and were imaged at a minimum of two orientations (0 degrees and 55 degrees ). Two specimens at 14% and 27% strain were imaged at every 5 degrees increment over the first quadrant of the angular space. Quantitative two-dimensional T(2) images and three-dimensional T(2) anisotropy maps of cartilage were constructed at a 19.8-microm in-depth resolution. RESULTS: The load-induced laminar appearance of cartilage at the magic angle became more distinct as the strain level increased. T(2) anisotropy maps of cartilage at 14% and 27% strain exhibited load-induced modifications in the collagen fibril ultrastructure, with a new peak toward the cartilage-bone interface and alterations to orientational dependence of T(2) anisotropy. CONCLUSION: Distinct alternations in the orientational dependence of microMRI T(2) anisotropy reflect the organizational modification of the collagen matrix due to external loading. This approach could become useful in detecting changes in cartilage's macromolecular structure due to injury or diseases.

Algorithms↗
PubMed1989

A new method for aligning histological serial sections for three-dimensional reconstruction.

A new method for aligning histological serial sections for three-dimensional reconstruction by computer is introduced. This method is particularly suited for embedding structures in celloidine or paraplast. Prior to sectioning, at least three reference markers are affixed to the preparation in a direction perpendicular to the section plane, for easy identification on the finished sections. An algorithm translates and rotates the serial sections until all the reference markers are congruent. The main advantage of this method, however, is its capability to eliminate deformations caused by compression or stretching during sectioning by the determination of correction factors.

Algorithms↗
PubMed2006

Digitized cervical images: problems, solutions, and potential medical impact.

OBJECTIVE: To demonstrate compression, illumination enhancement, registration, segmentation, automated classification and steganography using digitized cervical images. MATERIALS AND METHODS: The Hybrid Multi-Scale Vector Quantization algorithm developed at Texas Technological University and other automated systems were used to improve digitized cervical images. RESULTS: We demonstrated high levels of image compression, illumination enhancement, registration, automated segmentation and classification and steganography of digitized cervical images. CONCLUSIONS: Digitized cervical images can be altered to facilitate research of cervical neoplasia.

Cervix Uteri↗
PubMed2005

Myocardial contusion injury: redefining the diagnostic algorithm.

Myocardial contusion injury (MCI) is a complication of blunt thoracic trauma, which may occur at relatively low velocities. MCI may also occur from chest compressions during cardiopulmonary resuscitation. We review the clinical pathology, diagnostic tools, and treatment for MCI.

Algorithms↗
PubMed2001

ECG data compression using wavelets and higher order statistics methods.

This paper evaluates the compression performance and characteristics of two wavelet coding compression schemes of electrocardiogram (ECG) signals suitable for real-time telemedical applications. The two proposed methods, namely the optimal zonal wavelet coding (OZWC) method and the wavelet transform higher order statistics-based coding (WHOSC) method, are used to assess the ECG compression issues. The WHOSC method employs higher order statistics (HOS) and uses multirate processing with the autoregressive HOS model technique to provide increasing robustness to the coding scheme. The OZWC algorithm used is based on the optimal wavelet-based zonal coding method developed for the class of discrete "Lipschitizian" signals. Both methodologies were evaluated using the normalized rms error (NRMSE) and the average compression ratio (CR) and bits per sample criteria, applied on abnormal clinical ECG data samples selected from the MIT-BIH database and the Creighton University Cardiac Center database. Simulation results illustrate that both methods can contribute to and enhance the medical data compression performance suitable for a hybrid mobile telemedical system that integrates these algorithmic approaches for real-time ECG data transmission scenarios with high CRs and low NRMSE ratios, especially in low bandwidth mobile systems.

Algorithms↗
PubMed1997

[The treatment of therapy-resistant lateral epicondylitis].

Failed treatment for chronic or refractory lateral epicondylitis can successfully be avoided strictly respecting guidelines in diagnosis, treatment and patient selection. Co-existing or simply other pathologic conditions as radial nerve compression neuropathy or instability of the elbow are evident reasons for failure and have to be treated accordingly to the condition. Inadequate patient selection, lack of compliance in performing therapy as well as ongoing cumulative trauma exposure are further factors compromising correct treatment and have to be ruled out prior to surgical therapy.

Algorithms↗
PubMed1989

Efficient storage of urodynamic signals by computer: application of FAN adaptive sampling.

Digital storage of urodynamic signals such as detrusor pressure and flowrate at a sufficiently high sampling rate (10 samples per second) to allow subsequent analysis requires considerable computer memory. A procedure for compressing these data by deleting redundant samples (the fan method of adaptive sampling) was tested. The method allows a flexible adaptation to specific hardware and a compromise between storage requirements and accuracy. In this study the number of samples required for adequate reconstruction of the detrusor pressure signal could be varied from 80% to 4% of the original number of samples by varying the average difference between reconstructed and original signal from 0.01 to 2 cm H2O. Fast components of the measurements (for example cough peaks) which were lost if a lower sampling rate or averaging was used to obtain equally low storage requirements were unaffected by this compression technique.

Algorithms↗
PubMedDate not supplied

Visual disturbances of migraine.

Migraine, a clinical syndrome of unknown etiology, is a common cause of a variety of visual disturbances. This review describes the visual alterations associated with migraine syndromes of particular interest to the ophthalmologist; acephalgic, ocular, and ophthalmoplegic. Several current theories of migraine pathophysiology are discussed. Migrainous episodes are common and must be differentiated from neurologic dysfunction due to ischemia, inflammation, seizure, and compression. The differentiating characteristics of these conditions as well as a diagnostic algorithm are presented.

Adolescent↗
PubMed2006

Optimal cut of trabecular network.

It has been shown recently that failure of mechanically tested trabecular bone samples can be localized within a part of the volume of the samples. Bone volume fraction BV/TV of failure regions was found to be a better determinant of the mechanical competence of the specimens and was smaller than BV/TV of the whole samples. These results suggest that localization of a failure within a part of an inhomogeneous trabecular network can be related to the presence of a surface of minimal cut-a surface separating the analyzed trabecular sample into two disjoint parts in such a way, that the separation requires removal of minimal possible amount of bone material. Thus, to properly address the problem of mechanical competence of a trabecular bone sample, one must be able to detect and describe the surface of minimal cut. In this paper an algorithm localizing surfaces of minimal cut within 3D trabecular structures is introduced.

Algorithms↗
PubMed2001

Acute low cervical nerve root conditions: symptom presentations and pathobiological reasoning.

Acute low cervical nerve root conditions may be easily misdiagnosed. The perspective presented is that their symptom presentation is not as straightforward as the classic descriptions of brachialgia would have us believe. This clinical commentary presents a series of observations and reasoning models that are relevant to patient symptom presentations believed to be of cervical nerve root origin. Clinicians are urged to consider low cervical nerve root assessment in the light of our current understanding of neural sensitivity, pain science, nerve root biomechanics and the presence and effect of degenerative changes. This particularly relates to thoughts about cervical movements and postures being able to bring forces to bear on nerve roots via compressive as well as elongation forces.

Algorithms↗
PubMed2002

Algorithmic cooling and scalable NMR quantum computers.

We present here algorithmic cooling (via polarization heat bath)-a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our "spin-refrigerating" method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved.

Journal Article↗
PubMedDate not supplied

Performance improvement of the SPIHT coder based on statistics of medical ultrasound images in the wavelet domain.

This paper proposes some modifications to the state-of-the-art Set Partitioning In Hierarchical Trees (SPIHT) image coder based on statistical analysis of the wavelet coefficients across various subbands and scales, in a medical ultrasound (US) image. The original SPIHT algorithm codes all the subbands with same precision irrespective of their significance, whereas the modified algorithm processes significant subbands with more precision and ignores the least significant subbands. The statistical analysis shows that most of the image energy in ultrasound images lies in the coefficients of vertical detail subbands while diagonal subbands contribute negligibly towards total image energy. Based on these statistical observations, this work presents a new modified SPIHT algorithm, which codes the vertical subbands with more precision while neglecting the diagonal subbands. This modification speeds up the coding/decoding process as well as improving the quality of the reconstructed medical image at low bit rates. The experimental results show that the proposed method outperforms the original SPIHT on average by 1.4 dB at the matching bit rates when tested on a series of medical ultrasound images. Further, the proposed algorithm needs 33% less memory as compared to the original SPIHT algorithm.

Algorithms↗