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PubMed1987

Differentiation of vascular and neurogenic claudication.

Lower extremity pain caused by exercise but relieved by rest is usually a reliable symptom of chronic arterial insufficiency. However, similar discomfort often occurs in patients who have neurospinal compression. Furthermore, both arterial occlusive disease and neurogenic causes of lower extremity discomfort may present simultaneously. Forty patients with symptoms that suggested intermittent claudication comprised our study group. All had non-arterial cause of their complaint. The nonvascular origin of the symptoms was suggested initially by clinical evaluation in 30 patients and by noninvasive evaluation in 25 patients. The neurospinal origin of symptoms was obscured in 15 patients because of the concomitant presence of significant arterial occlusive disease as demonstrated by noninvasive arterial testing. Twelve of these 15 patients underwent arterial reconstruction, which did not relieve their symptoms. Subsequently, the neurospinal origin of their symptoms was proven by appropriate evaluation and therapy. Forms of evaluation that proved helpful in the differential diagnosis were lumbosacral spine x-rays, electromyography, nerve conduction velocity studies, computerized tomography, Doppler noninvasive assessment and, at times arteriography and contrast myelography.

Adult↗
PubMed1992

Differential diagnosis and surgical treatment of pathologic spine fractures.

The prognosis for survival has improved dramatically for cancer patients over the past three decades. Advances in systemic therapy have prolonged survival even in those who cannot be cured. The importance of managing spinal column disease and protecting the spinal cord has subsequently been amplified. Almost any patient presenting with detectable neurologic function and enough physical reserve to withstand an operation will benefit from a spinal stabilization, pain relief, and neural decompression; there are few exceptions. Advances in surgical technique and biomaterials have not only improved survival and functional outcome, they have diminished many of the postoperative complications that plagued earlier treatment techniques. Methods of preventing or correcting iatrogenic deformity have improved outcome. Newer fixation techniques promise to eliminate many of the causes of hardware and fixation failure previously seen. Improved medical management, antibiotics, and preoperative planning, along with techniques of preoperative embolization and early postoperative mobilization have made surgical management much less risky. Vertebrectomy, considered a last alternative in the past, is now coming to be seen as the conservative approach to tumor management in many situations. Appropriate surgical treatment can have a dramatic impact on function and outcome in patients with tumors of the spinal column, and should never be dismissed as an option without serious consideration. Advances in fixation systems, local and systemic therapy, and in our understanding of the biology of cancer promise even greater improvements for the future.

Adult↗
PubMed1988

Towards a digital model for an electron-microscope image.

An image model is defined based on the boundaries between image regions with different textures and series of descriptions of those textures. Six models of texture are studied under the categories of pixel-based and region-based models. Several techniques for the determination of the unit-cell of textures are presented. The model is applied to the consideration of (a) image correction, (b) the classification of image texture, (c) image enhancement including averaging of detail in periodic specimens, and (d) image data compression. A floating point format, which provides a significant simplification for the Huffman code, is also introduced.

Algorithms↗
PubMed1991

Signals in DNA sequences and their potential properties.

DNA and RNA molecules contain signals which are recognized by regulatory proteins or enzymes either directly, through their nucleotide sequences or indirectly, through induced structural changes on their neighboring sequences. To date, most signal searches have been focused on specific recurrences of nucleotide sequences. Much less attention has been directed towards the structure, flexibility and hydrogen-bonding patterns that recognition elements may possess. Here we review the various methods involved in such searches. In particular, however, we also address the searches for potential properties. In this regard it is of interest to inspect the asymmetry in the distributions of complementary oligomers near biological features. Upstream of transcription initiation the frequencies of G-rich oligomers are particularly high (Nussinov, 1987a; 1990). The frequencies of C-rich oligomers are lower. A-tracts are also very frequent in these regions. This may correlate with the recent finding that guanine, but not cytosine, tracts enhance A-tract directed bends (Milton et al., 1990). Presumably A-tracts near G-tracts on the same strand may induce a structural change in the G-tracts which may enhance the bend. G-tracts may have the potential for participating in a DNA bend due to their compression of the major groove. Thus, proteins may not always be necessary to induce DNA conformational changes. This example illustrates the importance of studies of the properties of DNA oligomers in regulatory regions, and of algorithms for their detection.

Algorithms↗
PubMedDate not supplied

[The role of computer methods in the diagnosis of mono- and multifactorial traumatic compression of the brain].

A scheme of differential diagnosis of mono- and multifactor compression of the brain was formed on the grounds of 18 most frequently encountered signs of the injury. The work is based on 693 cases which were verified on operation. The results were checked on a large independent selection. Accuracy of recognition was 87.5%. The Table suggested by the authors may prove valuable in emergency situations when the patients are admitted in a serious condition, in impetuous development of the compression syndrome, and when there is lack of time for carrying out instrumental examination.

Adult↗
PubMedDate not supplied

[Mechanical deformations of bioconstructions during different stages of morphogenesis].

The stress-deformation regularities of the body behaviour are taken as principal pattern formation factors in bioconstructions: mutually compressed cap rays of Acetabularia and contiguous tissue layers (the model). With the growth of rays or layers mechanical tensions which are initiated in them increase. If no morphogenetic loss of shape stability is resulted, an alternative algorithm of natural complication of their initial pattern is finally realized and ruptures, shifts and other deformations are formed in some weakened elements of the constructions. Among rigid stable parameters of biomaterials and geometric parameters of bioconstructions only the latter prove to be the determining ones in feasibility criterion of this or that extreme case of pattern formation (with the loss of stability or fractures). Restrictions imposed to the values of possible deformations are conditioned in case of the loss of pattern stability by geometric parameter, in case of fractures--by the strength parameters.

Acetabularia↗
PubMed1988

The impact of magnetic resonance on the diagnostic evaluation of acute cervicothoracic spinal trauma.

From 1984 to 1987 magnetic resonance (MR) imaging was performed on 100 patients suffering acute spinal trauma. MR demonstrated one or more injuries to the cervicothoracic region in 31 patients. It displayed a spectrum of spinal cord injury ranging from mild compression and swelling to complete transection. MR was also useful in evaluating alignment at the cervicothoracic junction, in depicting ligamentous injury, in establishing the presence of disc herniation, and in identifying unsuspected levels of injury. We present a diagnostic algorithm that incorporates the role of MR in evaluating acute cervicothoracic spinal trauma and emphasizes the replacement of myelography by MR in the initial assessment of neurologic deficit.

Acute Disease↗
PubMed1984

A technique for the detection, decomposition and analysis of the EMG signal.

In the present paper we have described a system for acquiring, processing and decomposing EMG signals for the purpose of extracting as many motor unit action potential trains as possible with the greatest level of accuracy. This system consists of 4 main sections. The first section consists of methodologies for signal acquisition and quality verification. Three channels of EMG signals are acquired using a quadripolar needle electrode designed to enhance discrimination among different MUAPs. An automated experiment control system is devised to free the experimenter from the burden of experiment detailed surveillance and bookkeeping; and to allow on-line assessment of the EMG signal quality in terms of decomposition suitability. The second section consists of methodologies for signal sampling and conditioning. The EMG signal is bandpass filtered (between 1 kHz and 10 kHz), sampled and compressed by eliminating parts of the signal under a preset threshold level. The third section consists of a signal decomposition technique where motor unit action potential trains are extracted from the EMG signal using a highly computer assisted interactive algorithm. The algorithm uses a continuously updated template matching routine and firing statistics to identify MUAPs in the EMG signal. The templates of the MUAPs are continuously updated to enable the algorithm to function even when the shape of a specific MUAP undergoes slow variations. The fourth section deals with ways in which to analyze and display the results. The more frequently used representation formats are: (1) display of MUAP wave shapes; (2) impulse trains representing motor unit firings; (3) IPI plots where time interval between successive firings of the same motor unit is plotted vs. time of the muscle contraction; (4) firing rate plots where the estimated time-varying mean firing rate of the detected motor units is plotted vs. time of the muscle contraction. The performance of the system has been tested in terms of: (1) consistency among results obtained by different operators; (2) accuracy evaluated on synthetic EMG signal; (3) indirect measure of accuracy on real EMG signal by comparing results pertaining the same motor unit action potential trains derived by two EMG signals, independently and simultaneously recorded from two different electrodes.

Action Potentials↗
PubMed1988

Measurement of pitch by subharmonic summation.

In order to account for the phenomenon of virtual pitch, various theories assume implicitly or explicitly that each spectral component introduces a series of subharmonics. The spectral-compression method for pitch determination can be viewed as a direct implementation of this principle. The widespread application of this principle in pitch determination is, however, impeded by numerical problems with respect to accuracy and computational efficiency. A modified algorithm is described that solves these problems. Its performance is tested for normal speech and "telephone" speech, i.e., speech high-pass filtered at 300 Hz. The algorithm out-performs the harmonic-sieve method for pitch determination, while its computational requirements are about the same. The algorithm is described in terms of nonlinear system theory, i.c., subharmonic summation. It is argued that the favorable performance of the subharmonic-summation algorithm stems from its corresponding more closely with current pitch-perception theories than does the harmonic sieve.

Algorithms↗
PubMed1987

Deformation analyses in cell and developmental biology. Part II--Mechanical experiments on cells.

This study employs the finite element approach developed in Part I to analyze mechanical experiments on cells. It views cells as axisymmetric membrane structures containing a body of incompressible material, and models the mechanical contact between a cell and the loading apparatus by a contact algorithm. Since the method is valid for analyzing axisymmetric shell-like bodies with arbitrary shapes, it treates various mechanical experiments on cells in a unified manner. For demonstration purposes, three commonly used mechanical experiments on cells are considered; the compression experiment; the suction (micropipette aspiration) experiment; and the magnetic particle experiment. Based on an estimate of the mechanical property data for unfertilized sea urchin eggs, this analysis method predicts the responses for all three experiments using the same assumptions and approximations. This parallel treatment gives a broad basis for data correlation with experiments. The method also provides insights into mechanical experiments not offered by other approximate methods. For example, it gives the distributions of tensions and stretches on the cell cortex, and suggests the role of friction in the suction experiment.

Animals↗
PubMed1992

System identification for the ECG using CZT.

A new approach for extraction of clinically useful parameters from the ECG signal is presented using the system identification technique of CZT on the DCT-transformed signal. A one to one relationship between the model singularities and the significant points in the time signal is arrived at. The method allows the determination of R-R interval needed in rhythm analysis. The complex cepstrum is used for identifying and removing the effect of zeros outside the unit circle. A significant data compression of 1 in 10 is achieved. A large number of continuous strips of ECG data are analyzed and the results are presented.

Algorithms↗
PubMed1991

Application of the u-p finite element method to the study of articular cartilage.

The finite element method using the principle of virtual work was applied to the biphasic theory to establish a numerical routine for analyses of articular cartilage behavior. The matrix equations that resulted contained displacements of the solid matrix (mu) and true fluid pressure (p) as the unknown variables at the element nodes. Both small and large strain conditions were considered. The algorithms and computer code for the analysis of two-dimensional plane strain, plane stress, and axially symmetric cases were developed. The u-p finite element numerical procedure demonstrated excellent agreement with available closed-form and numerical solutions for the configurations of confined compression and unconfined compression under small strains, and for confined compression under large strains. The model was also used to examine the behavior of a repaired articular surface. The differences in material properties between the repair tissue and normal cartilage resulted in significant deformation gradients across the repair interface as well as increased fluid efflux from the tissue.

Biomechanical Phenomena↗
PubMed1984

Automatic classification of EEG segments and extraction of representative ones by dynamic clusters method.

Use of the dynamic clusters method for automatic extraction of compressed information about recorded EEG signal is presented. The computer first divides the record into quasi-stationary segments by means of adaptive segmentation. Second, the extracted segments are classified by a method of dynamic clusters into homogeneous classes. One part of the used clustering algorithm permits to specify and draw the most typical class members, which may represent the whole studied EEG signal and may be used as input for the further phase of the automatic EEG analysis, i.e. for the classification of the whole EEG records. The above procedure was applied to a 75 sec long EEG record of anaesthetized cat intoxicated by CO.

Computers↗
PubMed1992

Artificial neural network classification of Drosophila courtship song mutants.

Courtship songs produced by Drosophila males--wild-type, plus the cacophony and dissonance behavioral mutants--were examined with the aid of newly developed strategies for adaptive acoustic analysis and classification. This system used several techniques involving artificial neural networks (a.k.a. parallel distributed processing), including learned vector quantization of signals and non-linear adaption (back-propagation) of data analysis. "Pulse" song from several individual wild-type and mutant males were first vector-quantized according to their frequency spectra. The accumulated quantized data of this kind, for a given song, were then used to "teach" or adapt a multiple-layered feedforward artificial neural network, which classified that song according to its original genotype. Results are presented on the performance of the final adapted system when faced with novel test data and on acoustic features the system decides upon for predicting the song-mutant genotype in question. The potential applications and extensions of this new system are discussed, including how it could be used to screen for courtship mutants, search novel behavior patterns or cause-and-effect relationships associated with reproduction, compress these kinds of data for digital storage, and analyze Drosophila behavior beyond the case of courtship song.

Algorithms↗
PubMed1990

Quadtree-based data compression of abdominal CT images.

An ROC study was performed to evaluate the effect of quadtree-based data compression on the diagnostic yield of CT images. Seventy images were selected from a series of consecutive abdominal/pelvic CT scans. Following the application of quadtree-based compression, all images were reviewed independently by three radiologists. The images were analyzed at six decreasing irreversible compression ratios (30.6:1 to 7.4:1), as well as after reversible compression (2.9:1). ROC curves reveal a gradual decrease in clinical accuracy with increasing compression ratios. At a compression ratio of 7.4:1, sensitivity for all major abnormalities was 99% with a specificity of 93%. As the compression ratio was increased to 30.6:1, sensitivity and specificity dropped to 75% and 83% respectively. Execution times for compression and decompression of the CT images with a PC-AT based digital radiography system varied from 24.7 to 18.5 seconds and from 16.2 to 5.1 seconds respectively, decreasing with higher levels of compression. We conclude that quadtree-based compression of abdominal CT images may have practical applications for a PC based digital radiography system.

Algorithms↗
PubMed1988

Implications of protein folding. Additivity schemes for volumes and compressibilities.

Partial specific volume and compressibility properties of the extended state of proteins are estimated from additivity schemes using revised amino acid and peptide data. These calculated properties are compared with the experimental data of the native state in order to assess the contribution from folding. Results of this treatment show that, in the case of partial specific volumes, there is close agreement between the two data sets for a number of proteins. The implication is that subtle compensatory contributions in volume occur during the folding process. In the case of compressibilities, however, a substantial difference is observed which is believed to arise because of the hydrophobic interior created in the native protein as a result of the folding process. Using suitable measures of protein hydrophobicities and estimates of the fraction of buried apolar residues, a "micellar model of protein compressibility" is proposed and tested for several proteins. Results obtained from this model show good agreement with the experimental data for the native state of a number of proteins.

Algorithms↗
PubMed1988

Clinical usefulness of an algorithm for the early diagnosis of spinal metastatic disease.

We have previously reported an algorithm that invokes several imaging modalities in the early detection of metastatic and benign disease of the spine in patients with cancer (J Clin Oncol 4:576, 1986). The development of new lesions (shown by Tc99m bone scans) in cancer patients with normal neurological examinations is further evaluated with plain radiographs, spinal computed tomography (CT), and CT myelography (CT-M). Of 60 patients in the original study, 28% were diagnosed as having only benign disease and the remainder had spinal metastases. Thecal sac impingement was seen in 47% of patients with metastatic disease and disruption of the posterior vertebral cortex was noted in all patients with epidural compression. We now report the 2-year follow-up of 55 of these patients. Without treatment, the 17 patients diagnosed with benign disease have shown no evidence of local failure in the spine and median survival is greater than 27 months. Thirty-eight patients diagnosed with spinal metastases had a median survival time of 16.9 months. Radiation therapy directed by CT-M findings provided pain relief in 78% of patients with back pain and metastatic disease. No patient, including 19 with thecal sac impingement, developed clinical myelopathy. These results demonstrate the usefulness of an imaging algorithm for the early identification and distinction of spinal metastatic disease and benign disease in patients with cancer.

Algorithms↗
PubMed1988

Imaging system for morphometric assessment of absorption or fluorescence in stained cells.

An image acquisition and processing system has been developed for quantitative microscopy of absorption or fluorescence in stained cells. Three different light transducers are used in the system to exploit the best characteristics of these sensors for different biological measurements. A digital scanner, in the form of a linear array charge-coupled device (CCD), acquires data with high spatial and photometric resolution. A color (RGB) camera is employed when spectral information is required for the segmentation of cellular subcomponents. An image-intensified charged-injection device (CID) camera provides for very low light intensity measurements, primarily for fluorescence-labeled cells. Properties of these transducers, such as contrast transfer function, linearity, and photo-response nonuniformity, have been measured. Two dedicated image processing units were incorporated into the system. The front-end processor, based on a digital signal processor, provides functions such as object detection, raw image calibration, compression, artifact removal, and filtering. The second image processor is associated with the frame memory and includes a histogram processor, a dedicated arithmetic logic unit for image processing functions, and a graphics module for one-bit overlay functions. An interactive program was developed to acquire cell images and to experiment with a range of segmentation algorithms, feature extractions, and other image processing functions. The results of any image operation are displayed on the video monitor. Once a desired processing sequence is determined, the sequence may be stored to become part of a command library and can be executed thereafter as a single instruction.

Algorithms↗