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PubMed1986

Compression of nucleic acid and protein sequence data.

This paper describes the application of text compression methods to machine-readable files of nucleic acid and protein sequence data. Two main methods are used to reduce the storage requirements of such files, these being n-gram coding and run-length coding. A Pascal program combining both of these techniques resulted in a compression figure of 74.6% for the GenBank data-base and a program that used only n-gram coding gave a compression figure of 42.8% for the Protein Identification Resource database.

Algorithms↗
PubMed2003

Time-frequency analysis of SEMG--with special consideration to the interelectrode spacing.

The surface electromyogram (SEMG) is a complex, nonstationary signal. The spectrum of the SEMG is dependent on the force of contraction being generated and other factors like muscle fatigue and interelectrode distance (IED). The spectrum of the signal is time variant. This paper reports the experimental research conducted to study the influence of force of muscle contraction and IED on the SEMG signal using time-frequency (T-F) analysis. Two T-F techniques have been used: Wigner-Ville distribution (WVD) and Choi-Williams distribution (CWD). The experiment was conducted with the help of ten healthy volunteers (five males and five females) who performed isometric elbow flexions of the active right arm at 20%, 50%, and 80% of their maximal voluntary contraction. The SEMG signal was recorded using surface electrodes placed at a distance of 18 and 36 mm over biceps brachii muscle. The results indicate that the two distributions were spread out across the frequency range at smaller IED. Further, regardless of the spacing, both distributions displayed increased spectral compression with time at higher contraction level.

Adult↗
PubMed2003

Effects of left ventricular contractility and coronary vascular resistance on coronary dynamics.

Wave-intensity analysis, which separates upstream from downstream events and defines their interaction, has been used to study the effects of changes in left ventricular (LV) contractility (E(max)) and left circumflex coronary artery resistance (R(LCx)) on the coronary systolic flow impediment (CSFI). In 10 anesthetized, open-chest dogs, we measured coronary, aortic, and LV pressures, coronary velocity (Flowire), and flow. E(max) was increased by paired pacing and R(LCx) was modulated by intracoronary infusions of vasodilators (adenosine and nitroglycerin) and a vasoconstrictor (phenylephrine). When both E(max) and R(LCx) were varied, CSFI and the energy of the backward-going compression wave (I(W-)) were greatest at the highest levels of E(max) and the lowest levels of R(LCx). I(W-) was proportional to the CSFI. We conclude that contractility and coronary resistance change CSFI by modulating the backward-going compression wave.

Algorithms↗
PubMedDate not supplied

[ECG compression method by using multiple polynomial modelling: comparison with wavelet-changing technique].

The proposed ECG compression combined two approaches, ECG beat alignment and polynomial modeling. QRS complexes are firstly detected then aligned in order to reduce high frequency changes from beat to beat. These changes are modeled by means a polynomial projection. ECG from MIT-BIH database are used to evaluate the performances of the proposed technique. A comparison with the wavelet approach is performed by means the compression ratio (CR) versus the RRD curve.

Algorithms↗
PubMed2006

[Study of color blood image segmentation based on two-stage-improved FCM algorithm].

This paper introduces a new method for color blood cell image segmentation based on FCM algorithm. By transforming the original blood microscopic image to indexed image, and by doing the colormap, a fuzzy apparoach to obviating the direct clustering of image pixel values, the quantity of data processing and analysis is enormously compressed. In accordance to the inherent features of color blood cell image, the segmentation process is divided into two stages. (1)confirming the number of clusters and initial cluster centers; (2) altering the distance measuring method by the distance weighting matrix in order to improve the clustering veracity. In this way, the problem of difficult convergence of FCM algorithm is solved, the iteration time of iterative convergence is reduced, the execution time of algarithm is decreased, and the correct segmentation of the components of color blood cell image is implemented.

Algorithms↗
PubMed2002

A modified block matching method for real-time freehand strain imaging.

This manuscript reports a technical innovation that has been developed for real-time, freehand strain imaging. This work is based on a well-known block-matching algorithm with two significant modifications. First, since displacements are estimated row-by-row, displacement estimates from the previous row are used to predict the displacement estimates in the current row, thereby drastically reducing the search-region size and increasing computational efficiency. Second, a displacement error detection and correction method is developed to overcome the local tracking errors that may be more severe with freehand scanning and thereby improve the robustness of the algorithm. This algorithm has been implemented on a clinical ultrasound imaging system, and with real-time imaging feedback, long sequences of high quality strain images are observed using freehand compression. Displacement estimation errors with this method are experimentally measured and compared with results from simulation. We report only a specific implementation, with no comparison to other displacement estimators in the literature and no optimization of this specific technique. Images of tissue-mimicking phantoms with small spherical targets are used to test the ability to detect small lesions using the strain imaging technique. In vivo strain images of breast and thyroid are also shown.

Algorithms↗
PubMedDate not supplied

Adaptive Fourier series modeling of time-varying evoked potentials: study of human somatosensory evoked response to etomidate anesthetic.

Evoked potentials (EPs) have traditionally been analyzed in time domain, with amplitude and latency of various signal components used in clinical interpretation. A new approach, called adaptive Fourier series modeling (FSM), is presented here. Dynamic changes in magnitudes of Fourier coefficients are analyzed for diagnostic purposes. In order to estimate the time-varying changes in the Fourier coefficients of noisy signals, a least mean-square filtering algorithm is applied. Results of computer simulations as well as experimental data are presented. Time-varying trends are presented in a new compressed evoked spectrum format. These techniques are applied to the study of alterations in human somatosensory EPs caused by the intravenous administration of etomidate during neurosurgical procedures. Amplitude increases of the order of 200-500% occurring within a time span of about 100 sec were captured. Due to its superior convergence properties, the adaptive FSM technique estimates more rapid changes in amplitude and latency than exponentially weighted averaging or moving window averaging schemes.

Computer Simulation↗
PubMed2005

A psychophysical evaluation of spectral enhancement.

Listeners with sensorineural hearing loss have well-documented elevated hearing thresholds; reduced auditory dynamic ranges; and reduced spectral (or frequency) resolution that may reduce speech intelligibility, especially in the presence of competing sounds. Amplification and amplitude compression partially compensate for elevated thresholds and reduced dynamic ranges but do not remediate the loss in spectral resolution. Spectral-enhancement processing algorithms have been developed that putatively compensate for decreased spectral resolution by increasing the spectral contrast, or the peak-to-trough ratio, of the speech spectrum. Several implementations have been proposed, with mixed success. It is unclear whether the lack of strong success was due to specific implementation parameters or whether the concept of spectral enhancement is fundamentally flawed. The goal of this study was to resolve this ambiguity by testing the effects of spectral enhancement on detection and discrimination of simple, well-defined signals. To that end, groups of normal-hearing (NH) and hearing-impaired (HI) participants listened in 2 psychophysical experiments, including detection and frequency discrimination of narrowband noise signals in the presence of broadband noise. The NH and HI listeners showed an improved ability to detect and discriminate narrowband increments when there were spectral decrements (notches) surrounding the narrowband signals. Spectral enhancements restored increment detection thresholds to within the normal range when both energy and spectral-profile cues were available to listeners. When only spectral-profile cues were available for frequency discrimination tasks, performance improved for HI listeners, but not all HI listeners reached normal levels of discrimination. These results suggest that listeners are able to take advantage of the local improvement in signal-to-noise ratio provided by the spectral decrements.

Acoustic Stimulation↗
PubMed2003

Studies of wet granulation in small scale high shear mixer of 20 mg tablets of policosanol.

It was studied the influence of three factors in the manufacturing process of tablets containing 20 mg of policosanol in a small scale when was used a high shear mixer. A factorial design without repetitions was used, considering as independent variables: volume of binder solution, kneading time and the use or not of chopper. Data analysis was carried out using the Yates algorithm, considering the effect of these three factors over the diameter of the granules, the percent of fine powders in granulate and the compression forces. The diameter of the granules was increased with an increase in the volume of the binder solution added and with an increase in the kneading time and was decreased when the chopper was used. The percent of fine powders, present in granulate, was significantly diminished with an increase of the volume of binder solution and diminished with an increase in the kneading time, the influence of the use of chopper was insignificant. The compression forces diminished with the use of chopper, with the increase of the volume of binder solution used and are not affected with the changes in the kneading time.

Anticholesteremic Agents↗
PubMed2006

Evaluation of the thyroid nodule.

BACKGROUND: Thyroid nodules are common, yet treatment modalities range from observation to surgical resection. Because thyroid nodules are frequently found incidentally during routine physical examination or imaging performed for another reason, physicians from a diverse range of specialties encounter thyroid nodules. Clinical decision making depends on proper evaluation of the thyroid nodule. METHODS: The current literature was reviewed and synthesized. RESULTS: Current evidence allows the formulation of recommendations and a general algorithm for evaluating the incidental thyroid nodule. CONCLUSIONS: Only a small percentage of thyroid nodules require surgical management. Diagnosis and treatment selection require a risk stratification by history, physical examination, and ancillary tests. Nodules causing airway compression or those at high risk for carcinoma should prompt evaluation for surgical treatment. In nodules larger than 1 cm, fine-needle aspiration biopsy is central to the evaluation as it is accurate, low risk, and cost effective. Subcentimeter nodules, often found incidentally on imaging obtained for another purpose, can usually be evaluated by ultrasonography. Other laboratory and imaging evaluations have specific and more limited roles. An algorithm for the evaluation of the thyroid nodule is presented.

Biopsy, Fine-Needle↗
PubMed2002

Management strategy for arterial priapism: therapeutic dilemmas.

PURPOSE: We present 7 cases of arterial high flow priapism and propose management algorithms for the condition. MATERIALS AND METHODS: We studied 2 children and 5 adults with posttraumatic arterial priapism. Blood gas analysis and color Doppler ultrasonography of the corpora cavernosa confirmed the diagnosis in 4 adults, while 1 patient had already undergone cavernous artery ligation in elsewhere. In the children perineal compression resulted in detumescence, a sign that is proposed to be indicative of the diagnosis of arterial priapism (piesis sign) complementing physical examination. Mechanical compressive force was applied to the perineum of 1 boy, while the other received a watchful waiting program. All adults participated in an observation regimen except 1, who decided to undergo immediate embolization of the internal pudendal artery. RESULTS: Perineal compression led to the resolution of priapism in 1 child, while spontaneous resolution was noted in the other. An adult noticed spontaneous penile detumescence 3 to 4 months after trauma, which was attributable to site specific venous leakage and decreased, inflow in the contralateral cavernous artery. The patient underwent venous surgery and is on an intracavernous injection regimen. Successful embolization of the internal pudendal artery was performed immediately in 1 man and in the other 4 months after trauma due to social inconvenience. Adult patient 3 is still on the watchful waiting protocol (42 months), while the one who underwent cavernous artery ligation is receiving treatment for erectile dysfunction. CONCLUSIONS: Absent of long-term damaging effects of arterial priapism on erectile tissue combined with the possibility of spontaneous resolution or progressive concomitant hemodynamic abnormalities associated with blunt perineal trauma are suggestive of the introduction of an observation period in the management algorithm of high flow priapism. Such a period may help avoid unnecessary intervention and determine the impact of priapism on patient personal life. Perineal compression may be also added as part of the physical examination as a sign specifically indicative of arterial priapism.

Adult↗
PubMed2004

Positron emission mammography with tomographic acquisition using dual planar detectors: initial evaluations.

Positron emission mammography (PEM) with tomographic acquisition using dual planar detectors rotating about the breast can obtain complete angular sampling and has the potential to improve activity estimation compared with PEM using stationary detectors. PEM tomography (PEMT) was compared with stationary PEM for point source and compressed breast phantom studies performed with a compact dual detector system. The acquisition geometries were appropriate for the target application of PEM guidance of stereotactic core biopsy. Images were reconstructed with a three-dimensional iterative maximum likelihood expectation maximization algorithm. PEMT eliminated blurring normal to the detectors seen with stationary PEM. Depth of interaction effects distorted the shape of the point spread functions for PEMT as the angular range from normal incidence of lines of response used in image reconstruction increased. Streak artefacts in PEMT for large detector rotation increments led to the development of an expression for the maximum rotation increment that maintains complete angular sampling. Studies with a compressed breast phantom were used to investigate contrast and signal-to-noise ratio (SNR) trade-offs for different sized spherical tumour models. PEMT and PEM both had advantages depending on lesion size and detector separation. The most appropriate acquisition method for specific detection or quantitation tasks requires additional investigation.

Algorithms↗
PubMed2001

Generation, description and storage of dendritic morphology data.

It is generally assumed that the variability of neuronal morphology has an important effect on both the connectivity and the activity of the nervous system, but this effect has not been thoroughly investigated. Neuroanatomical archives represent a crucial tool to explore structure-function relationships in the brain. We are developing computational tools to describe, generate, store and render large sets of three-dimensional neuronal structures in a format that is compact, quantitative, accurate and readily accessible to the neuroscientist. Single-cell neuroanatomy can be characterized quantitatively at several levels. In computer-aided neuronal tracing files, a dendritic tree is described as a series of cylinders, each represented by diameter, spatial coordinates and the connectivity to other cylinders in the tree. This 'Cartesian' description constitutes a completely accurate mapping of dendritic morphology but it bears little intuitive information for the neuroscientist. In contrast, a classical neuroanatomical analysis characterizes neuronal dendrites on the basis of the statistical distributions of morphological parameters, e.g. maximum branching order or bifurcation asymmetry. This description is intuitively more accessible, but it only yields information on the collective anatomy of a group of dendrites, i.e. it is not complete enough to provide a precise 'blueprint' of the original data. We are adopting a third, intermediate level of description, which consists of the algorithmic generation of neuronal structures within a certain morphological class based on a set of 'fundamental', measured parameters. This description is as intuitive as a classical neuroanatomical analysis (parameters have an intuitive interpretation), and as complete as a Cartesian file (the algorithms generate and display complete neurons). The advantages of the algorithmic description of neuronal structure are immense. If an algorithm can measure the values of a handful of parameters from an experimental database and generate virtual neurons whose anatomy is statistically indistinguishable from that of their real counterparts, a great deal of data compression and amplification can be achieved. Data compression results from the quantitative and complete description of thousands of neurons with a handful of statistical distributions of parameters. Data amplification is possible because, from a set of experimental neurons, many more virtual analogues can be generated. This approach could allow one, in principle, to create and store a neuroanatomical database containing data for an entire human brain in a personal computer. We are using two programs, L-NEURON and ARBORVITAE, to investigate systematically the potential of several different algorithms for the generation of virtual neurons. Using these programs, we have generated anatomically plausible virtual neurons for several morphological classes, including guinea pig cerebellar Purkinje cells and cat spinal cord motor neurons. These virtual neurons are stored in an online electronic archive of dendritic morphology. This process highlights the potential and the limitations of the 'computational neuroanatomy' strategy for neuroscience databases.

Algorithms↗
PubMed1996

Computationally efficient sub-band coding of ECG signals.

A data compression technique is presented for the compression of discrete time electrocardiogram (ECG) signals. The compression system is based on sub-band coding, a technique traditionally used for compressing speech and images. The sub-band coder employs quadrature mirror filter banks (QMF) with up to 32 critically sampled sub-bands. Both finite impulse response (FIR) and the more computationally efficient infinite impulse response (IIR) filter banks are considered as candidates in a complete ECG coding system. The sub-bands are threshold, quantized using uniform quantizers and run-length coded. The output of the run-length coder is further compressed by a Huffman coder. Extensive simulations indicate that 16 sub-bands are a suitable choice for this application. Furthermore, IIR filter banks are preferable due to their superiority in terms of computational efficiency. We conclude that the present scheme, which is suitable for real time implementation on a PC, can provide compression ratios between 5 and 15 without loss of clinical information.

Algorithms↗
PubMed1993

SCANGRAPH: a program for digitization of graphs using an image scanner.

The program SCANGRAPH has been developed for vectorizing any drawing or graph in the form of a single continuous line. With the use of the software, the raster image of a graph in the TIFF format as generated from an optical scanner or digitizing video system can be converted to the corresponding digitized graph with x and y coordinates given. The digitized data can be output in the ASCII format for importing to other software packages. Options for peak identification, data smoothing and compression, and graph comparison are also provided for data manipulation.

Algorithms↗
PubMed1996

Integrated management of venous thromboembolism.

Diagnostic methods for pulmonary embolism and deep vein thrombosis of the lower extremity are intertwined, since the latter nearly always precedes the former. Recent prospective studies show that an independent clinical estimate of disease probability helps to refine probability estimates of ventilation-perfusion lung scans and of ultrasonography with compression, reducing the need for pulmonary angiography and contrast venography. Repeated ultrasonography with compression can also be used to stratify patients into groups that are at high or low risk for subsequent pulmonary embolic events. I give algorithms and guidelines for the clinical use of these findings. Effective treatment of acute venous thromboembolism depends on achieving an antithrombotic state with heparin and warfarin. I give recommendations for dosing and monitoring heparin and warfarin that are based on knowledge of heparin blood levels and on use of the international normalized ratio with warfarin therapy. Use of low-molecular-weight heparin to prevent deep vein thrombosis is briefly described.

Algorithms↗