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PubMed1987

Osteoporosis: the structural and reparative consequences for the skeleton.

We have discussed the biomechanical and biomaterial properties of bone with emphasis on the microenvironment. The microdensity of bone tissues determines the resistance to compressive forces (strength = density2). The structural orientation of bone determines the ability of bone to withstand torsion and bending forces. Highly remodeled bone is brittle and fractures easily because of the multiple reversal planes within the bone plates. Conversely, augmentation of bone on the periphery by modeling leads to increased material microstrength and structural macrostrength. Consequently, appositional modeling augments whereas remodeling diminishes bone strength. Hip fractures, spinal fractures, Colles' fractures, and pelvic fractures have been discussed in terms of their pathophysiology and treatment. An algorithm (Fig. 4-7) has been presented for the differential diagnosis of patients with recently discovered spinal compression fractures. Lastly, a discussion of exercise demonstrated its beneficial role, especially in the retention of bone mass.

Biomechanical Phenomena↗
PubMed2005

Joint source/channel coding for image transmission with JPEG2000 over memoryless channels.

The high compression efficiency and various features provided by JPEG2000 make it attractive for image transmission purposes. A novel joint source/channel coding scheme tailored for JPEG2000 is proposed in this paper to minimize the end-to-end image distortion within a given total transmission rate through memoryless channels. It provides unequal error protection by combining the forward error correction capability from channel codes and the error detection/localization functionality from JPEG2000 in an effective way. The proposed scheme generates quality scalable and error-resilient codestreams. It gives competitive performance with other existing schemes for JPEG2000 in the matched channel condition case and provides more graceful quality degradation for mismatched cases. Furthermore, both fixed-length source packets and fixed-length channel packets can be efficiently formed with the same algorithm.

Algorithms↗
PubMed1995

Venous stasis ulcers. Diagnostic and surgical considerations.

BACKGROUND: Less than 10% of venous ulcers are refractory to a conservative treatment with compression bandages. Patients with such chronic or frequently recurring ulcers are candidates for surgical intervention. OBJECTIVE: This review article discusses the various therapeutic modalities for venous ulcers resistant to compression therapy. METHODS: Each therapeutic modality is discussed separately. RESULTS: There are several therapeutic options. It is not easy to determine the proper place of each therapeutic modality in the management of venous leg ulcers. No type of surgical or medical management is truly curative of venous insufficiency, only palliative. An algorithm is proposed, which may serve as a guideline for chosing the best suitable therapeutic option. CONCLUSION: With a better understanding of therapeutic options other than compression therapy the care for each individual patient may be optimized.

Algorithms↗
PubMed2005

Adaptive signal enhancement of somatosensory evoked potential for spinal cord compression detection: an experimental study.

The objective of this study was to assess the efficacy of adaptive signal enhancement (ASE) as a means of indicating intraoperative spinal cord impingement. ASE technique was used to determine the changes in the somatosensory evoked potential (SEP) elicited from eighteen rats with varying levels of spinal cord compression. ASE technique was found to be able to effectively extract SEP signals for the detection of spinal cord injury. Furthermore, while the traditional ensemble averaging (EA) technique requires more than 500 trials for meaningful signal processing in severe noisy SEP recordings, the ASE method required only 50 trials to provide similar information. Because of its fast and reliable SEP detection, the ASE method is ideal for spinal cord monitoring in the clinical setting.

Algorithms↗
PubMed1985

Storage volume of computer tomography images can be reduced by a factor of five.

The object of this study is the data compression of CT scans of the brain. A circle is first established which contains all pixels inside the head while minimizing the insignificant area, after which the portion outside the circle so obtained is eliminated. The data are then truncated at CT values of +/- 127 and the differences of two consecutive pixel values are converted into variable length codes. The coding algorithms employed are the well-known Huffman code and our packet coding, both of which achieved a data compression ratio of 20%.

Biometry↗
PubMed2005

Compression of map images by multilayer context tree modeling.

We propose a method for compressing color map images by context tree modeling and arithmetic coding. We consider multicomponent map images with semantic layer separation and images that are divided into binary layers by color separation. The key issue in the compression method is the utilization of interlayer correlations, and to solve the optimal ordering of the layers. The interlayer dependencies are acquired by optimizing the context tree for every pair of image layers. The resulting cost matrix of the interlayer dependencies is considered as a directed spanning tree problem and solved by an algorithm based on the Edmond's algorithm for optimum branching and by the optimal selection and removal of the background color. The proposed method gives results 50% better than JBIG and 25% better than a single-layer context tree modeling.

Algorithms↗
PubMed2000

[The comprehensive surgical treatment of patients with degenerative lesions of the lumbosacral spine].

On the basis of a complex analysis of surgical treatment of 52 patients with degenerative diseases of the lumbosacral part of the spine complicated by the formation of compressive reticulopathies main states were established responsible for the worse quality of life of this category of patients. Different forms of vertebrogenic radiculopathies were determined according to the morphological substrate of compression. The methods of diagnosing the spinal diseases at the lumbosacral level were estimated and the diagnostic algorithms for different variants of degenerative lesions were developed. Rational schemes of surgical correction are proposed according to the established groups of vertebrogenic lumbosacral radiculopathies. Special attention is given to prophylactics of recurrences of the pain syndrome and postoperative instability of the spine.

Humans↗
PubMed2002

Four-dimensional wavelet compression of arbitrarily sized echocardiographic data.

Wavelet-based methods have become most popular for the compression of two-dimensional medical images and sequences. The standard implementations consider data sizes that are powers of two. There is also a large body of literature treating issues such as the choice of the "optimal" wavelets and the performance comparison of competing algorithms. With the advent of telemedicine, there is a strong incentive to extend these techniques to higher dimensional data such as dynamic three-dimensional (3-D) echocardiography [four-dimensional (4-D) datasets]. One of the practical difficulties is that the size of this data is often not a multiple of a power of two, which can lead to increased computational complexity and impaired compression power. Our contribution in this paper is to present a genuine 4-D extension of the well-known zerotree algorithm for arbitrarily sized data. The key component of our method is a one-dimensional wavelet algorithm that can handle arbitrarily sized input signals. The method uses a pair of symmetric/antisymmetric wavelets (10/6) together with some appropriate midpoint symmetry boundary conditions that reduce border artifacts. The zerotree structure is also adapted so that it can accommodate noneven data splitting. We have applied our method to the compression of real 3-D dynamic sequences from clinical cardiac ultrasound examinations. Our new algorithm compares very favorably with other more ad hoc adaptations (image extension and tiling) of the standard powers-of-two methods, in terms of both compression performance and computational cost. It is vastly superior to slice-by-slice wavelet encoding. This was seen not only in numerical image quality parameters but also in expert ratings, where significant improvement using the new approach could be documented. Our validation experiments show that one can safely compress 4-D data sets at ratios of 128:1 without compromising the diagnostic value of the images. We also display some more extreme compression results at ratios of 2000:1 where some key diagnostically relevant key features are preserved.

Algorithms↗
PubMed2001

Imaging of onset and progression of Alzheimer's disease with voxel-compression mapping of serial magnetic resonance images.

BACKGROUND: Early diagnosis and monitoring of the progression of Alzheimer's disease is important for the development of therapeutic strategies. To detect the earliest structural brain changes, individuals need to be studied before symptom onset. We used an imaging technique known as voxel-compression mapping to localise progressive atrophy in patients with preclinical Alzheimer's disease. METHODS: Four symptom-free individuals from families with early-onset Alzheimer's disease with known autosomal dominant mutations underwent serial magnetic resonance imaging (MRI) over 5-8 years. All four became symptomatic during follow-up. 20 individuals with a clinical diagnosis of probable Alzheimer's disease and 20 control participants also underwent serial MR imaging. A non-linear fluid matching algorithm was applied to register repeat scans onto baseline imaging. Jacobian determinants were used to create the voxel-compression maps. FINDINGS: Progressive atrophy was revealed in presymptomatic individuals, with posterior cingulate and neocortical temporoparietal cortical losses, and medial temporal-lobe atrophy. In patients with known Alzheimer's disease, atrophy was widespread apart from in the primary motor and sensory cortices and cerebellum, reflecting the clinical phenomenology. INTERPRETATION: Voxel-compression maps confirmed early involvement of the medial temporal lobes, but also showed posterior cingulate and temporoparietal cortical losses at presymptomatic stage. This technique could be applied diagnostically and used to monitor the effects of therapeutic intervention.

Algorithms↗
PubMed2006

Interpretation of the Lempel-Ziv complexity measure in the context of biomedical signal analysis.

Lempel-Ziv complexity (LZ) and derived LZ algorithms have been extensively used to solve information theoretic problems such as coding and lossless data compression. In recent years, LZ has been widely used in biomedical applications to estimate the complexity of discrete-time signals. Despite its popularity as a complexity measure for biosignal analysis, the question of LZ interpretability and its relationship to other signal parameters and to other metrics has not been previously addressed. We have carried out an investigation aimed at gaining a better understanding of the LZ complexity itself, especially regarding its interpretability as a biomedical signal analysis technique. Our results indicate that LZ is particularly useful as a scalar metric to estimate the bandwidth of random processes and the harmonic variability in quasi-periodic signals.

Algorithms↗
PubMed2005

Missing the forest for the trees: phylogenetic compression and its implications for inferring complex evolutionary histories.

Phylogenetic tree reconstruction is difficult in the presence of lateral gene transfer and other processes generating conflicting signals. We develop a new approach to this problem using ideas borrowed from algorithmic information theory. It selects the hypothesis that simultaneously minimizes the descriptive complexity of the tree(s) plus the data when encoded using those tree(s). In practice this is the hypothesis that can compress the data the most. We show not only that phylogenetic compression is an efficient method for encoding most phylogenetic data sets and is more efficient than compression schemes designed for single sequences, but also that it provides a clear information theoretic rule for determining when a collection of conflicting trees is a better explanation of the data than a single tree. By casting the parsimony problem in this more general framework, we also conclude that the so-called total-evidence tree--the tree constructed from all the data simultaneously--is not always the most economical explanation of the data.

Algorithms↗
PubMed2005

An adaptive incremental LBG for vector quantization.

This study presents a new vector quantization method that generates codewords incrementally. New codewords are inserted in regions of the input vector space where the distortion error is highest until the desired number of codewords (or a distortion error threshold) is achieved. Adoption of the adaptive distance function greatly increases the proposed method's performance. During the incremental process, a removal-insertion technique is used to fine-tune the codebook to make the proposed method independent of initial conditions. The proposed method works better than some recently published efficient algorithms such as Enhanced LBG (Patane, & Russo, 2001) for traditional tasks: with fixed number of codewords, to find a suitable codebook to minimize distortion error. The proposed method can also be used for new tasks that are insoluble using traditional methods: with fixed distortion error, to minimize the number of codewords and find a suitable codebook. Experiments for some image compression problems indicate that the proposed method works well.

Algorithms↗
PubMed2004

Content-based retrieval of historical Ottoman documents stored as textual images.

There is an accelerating demand to access the visual content of documents stored in historical and cultural archives. Availability of electronic imaging tools and effective image processing techniques makes it feasible to process the multimedia data in large databases. In this paper, a framework for content-based retrieval of historical documents in the Ottoman Empire archives is presented. The documents are stored as textual images, which are compressed by constructing a library of symbols occurring in a document, and the symbols in the original image are then replaced with pointers into the codebook to obtain a compressed representation of the image. The features in wavelet and spatial domain based on angular and distance span of shapes are used to extract the symbols. In order to make content-based retrieval in historical archives, a query is specified as a rectangular region in an input image and the same symbol-extraction process is applied to the query region. The queries are processed on the codebook of documents and the query images are identified in the resulting documents using the pointers in textual images. The querying process does not require decompression of images. The new content-based retrieval framework is also applicable to many other document archives using different scripts.

Abstracting and Indexing↗
PubMed1995

Data clustering and other archive retrieval strategies for teleradiology and picture archiving and communication systems.

A key advantage in the conversion from film-based to digital radiology is the possibility of a long-term on line electronic archival of patient studies. The popular approach based on optical disk jukeboxes for the long-term archive and magnetic disk storage for data caching is not economically attractive because of the cost of both the jukebox and the medium. Strategies for extending the archival system design with a tape jukebox have been studied. The proposed strategy calls for the use of high-ratio lossy compression together with low-cost tape storage to make long-term on line archiving more affordable. An intelligent prefetching algorithm based on hospital information system and radiologic information system triggers, which in turn are augmented by manual case preparation, can effectively overcome the longer latency of ad hoc retrievals. This longer latency is caused by both system-level bottlenecks and the sequential access constraint of the tape drive. Strategies for image clustering and tape allocation by patient classification also enhance retrieval efficiency. This archival design using image compression, prefetching, and clustering could be implemented in many of the existing teleradiology and picture archiving and communication systems.

Algorithms↗
PubMedDate not supplied

Cervical spondylotic myelopathy: a review of surgical indications and decision making.

Cervical spondylotic myelopathy (CSM) is frequently underdiagnosed and undertreated. The key to the initial diagnosis is a careful neurologic examination. The physical findings may be subtle, thus a high index of suspicion is helpful. Poor prognostic indicators and, therefore, absolute indications for surgery are: 1. Progression of signs and symptoms. 2. Presence of myelopathy for six months or longer. 3. Compression ratio approaching 0.4 or transverse area of the spinal cord of 40 square millimeters or less. Improvement is unusual with nonoperative treatment and almost all patients progressively worsen. Surgical intervention is the most predictable way to prevent neurologic deterioration. The recommended decompression is anterior when there is anterior compression at one or two levels and no significant developmental narrowing of the canal. For compression at more than two levels, developmental narrowing of the canal, posterior compression, and ossification of the posterior longitudinal ligament, we recommend posterior decompression. In order for posterior decompression to be effective there must be lordosis of the cervical spine. If kyphosis is present, anterior decompression is needed. Kyphosis associated with a developmentally narrow canal or posterior compression may require combined anterior and posterior approaches. Fusion is required for instability.

Algorithms↗
PubMed2002

A dynamic anatomical study of ulnar nerve motion after anterior transposition for cubital tunnel syndrome.

Cubital tunnel syndrome is the second most commonly encountered compression neuropathy of the upper limb. Multiple techniques for surgical management have been proposed but no universally accepted algorithm for management exists. Six cadaveric upper limbs underwent ulnar nerve decompression and anterior transposition into subcutaneous and then submuscular positions. After marking nerves with tungsten, radiological examination of nerve motion was performed and nerve angulations were measured in the region of the flexor carpi ulnaris (FCU) origin. Comparison of ulnar nerves in each position revealed statistically significant greater angulation after subcutaneous transposition than after submuscular transposition with the elbow held in full flexion. This point of angulation may act as a secondary point of compression or as a focus for neuritis and scar formation. This finding can contribute to the understanding of why differing outcomes may be observed after different forms of anterior transposition.

Cadaver↗
PubMed2006

Lossless compression of color mosaic images.

Lossless compression of color mosaic images poses a unique and interesting problem of spectral decorrelation of spatially interleaved R, G, B samples. We investigate reversible lossless spectral-spatial transforms that can remove statistical redundancies in both spectral and spatial domains and discover that a particular wavelet decomposition scheme, called Mallat wavelet packet transform, is ideally suited to the task of decorrelating color mosaic data. We also propose a low-complexity adaptive context-based Golomb-Rice coding technique to compress the coefficients of Mallat wavelet packet transform. The lossless compression performance of the proposed method on color mosaic images is apparently the best so far among the existing lossless image codecs.

Algorithms↗