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At least 253 records · Page 14Linked to original sources
PubMed1984

Algorithms for restriction map comparisons.

An algorithm is presented which compares two restriction maps, yielding a measure of distance between the maps and relating the maps by an alignment. This new algorithm finds the minimum weighted sum of genetic events required to convert one map into the other, where the genetic events are the appearance/disappearance of restriction sites and changes in the number of bases between restriction sites. The algorithm is illustrated by comparison of the beta-delta region of the globin gene cluster of four primate species. The results are in excellent agreement with known evolutionary relationships.

Animals↗
PubMed1995

A real-time electrical impedance tomograph.

Electrical properties of tissues in the human body can be imaged using a technology known as Electrical Impedance Tomography. In this modality, sinusoidal electrical currents are applied to the body using electrodes attached to the skin, and voltages that are developed on the electrodes are measured. Using these data, a reconstruction algorithm computes the conductivity and permittivity distributions within the body. This paper describes the reconstruction algorithm, image display algorithm, and hardware of a real-time Electrical Impedance Tomograph known as the Real-Time Imaging System. The reconstruction algorithm, executed by a commercially available coprocessor board that resides in a 386-based personal computer, is a modification of the Newton's One Step Error Reconstructor (NOSER) that minimizes algorithm execution time by precomputing many quantities. The image display algorithm, also executed by the coprocessor board, maps the output of the reconstruction algorithm into an image which is displayed using a video graphics board. The architecture of the system and execution times of algorithms implemented by the system are discussed. Using the continuous data acquisition mode of the Real-Time Imaging System, data from the thorax of a normal human subject were collected. Admittivity changes in the chest, as a result of respiration and the cardiac cycle, are presented. Data that were collected from the leg of a normal subject are shown which demonstrate capabilities of the triggered data acquisition mode of the system, allowing data acquisition synchronization with an electrocardiogram.

Algorithms↗
PubMedDate not supplied

Characterization of a p(66)Be(49) neutron therapy beam II: skin-sparing and dose transition effects.

Results of buildup measurements in A-150 tissue equivalent plastic are presented for a p(66)Be(49) neutron beam. These measurements were taken in air and behind various materials to answer questions about skin-sparing, bolussing materials, recovery of skin-sparing, and dosimetry in small radiobiological samples. The depth for Dmax for this beam is 1.6 g cm-2. An algorithm is also presented that reproduces the measured dose buildup curves.

Computers↗
PubMed1991

Envelope expansion methods for speech enhancement.

The last decade has seen increasing interest in techniques for the enhancement of digital speech signals. Significant gains have been made in terms of signal-to-noise ratio (SNR) and quality, but few techniques have produced improvements in intelligibility. A method for speech enhancement based on nonlinear expansion of the spectral envelope is presented. The expansion is consistent with both the long-term spectrum of the speech and with the probability that speech is present in a given sample. Objective SNR measures are used to compare this algorithm with the well-known spectral subtraction method, with an alternative expansion scheme, and with limiting SNRs resulting from perfect recovery of the amplitude spectrum. For the purpose of intelligibility assessments, a simplified version of the algorithm has been implemented on a Texas Instruments TMS320-C25 system. Listening trials with this real-time system, conducted using a modified rhyme test, have produced small, but consistent, improvements in articulation scores.

Acoustics↗
PubMed1984

Myocardial contrast two-dimensional echocardiography: comparison of contrast disappearance rates in normal and underperfused myocardium.

A computer algorithm was developed and applied to measure brightness decay rates of myocardial contrast opacification observed with two-dimensional echocardiography (2DE). An agitated mixture of diatrizoate meglumine and saline (Renografin-saline) was injected into the left main coronary artery of 17 closed-chest dogs during the control state as well as after placement of an intracoronary plug to induce 85% stenosis in the left anterior descending coronary artery (LAD) in five dogs. In 12 dogs, injections were also performed distally to complete intracoronary balloon occlusion of the LAD. For each injection, up to 35 electrocardiographic-gated, end-diastolic 2DE frames were digitized into an image-processing computer that determined mean pixel brightness of each of 12 myocardial segments per 2DE short-axis cross-section. Time-activity curves for each segment were generated, and contrast decay half-life (t 1/2) was calculated. Mean t 1/2 for control-state injections was found to be 24.1 +/- 7.7 sec, as opposed to 293.8 +/- 164.5 sec after complete coronary occlusion (p less than .001). In the five dogs in which 85% LAD stenosis was induced, prolongation of contrast t 1/2 from 18.3 +/- 8.9 sec during control to 44.3 +/- 21.0 sec (p less than .001) after plug insertion occurred in myocardial segments subserved by the stenosed vessel. No significant change occurred in segments that were not supplied by the stenosed vessel (21.9 +/- 9.1 sec during control vs 24.9 +/- 11.6 after plug insertion into the LAD). A reproducibility study of injection-to-injection t 1/2 in the control state indicated a correlation coefficient of r = .84 and a standard error of the estimate (SEE) equal to 5.86 sec, while interobserver t 1/2 reproducibility was r = .91 and SEE = 5.21 sec. The t 1/2 measurement derived by computer analysis of myocardial contrast 2DE may serve as an index for characterization of regional myocardial blood flow and may be applicable to evaluate interventions that alter perfusion.

Animals↗
PubMed1981

Stereotactic surgical system controlled by computed tomography.

The three-dimensional data obtained by computed tomographic (CT) scanning offer an advantage in using this imaging technique for stereotactic surgical procedures. This requires interfacing of CT image data with a stereotactic guide. In the performance of functional procedures where the surgical target must be identified from brain landmarks, such as the anterior and posterior commissures, an image reconstruction technique that presents in an image high spatial resolution structural information must be used. The description of a fully hardware- and software-interfaced CT-directed stereotactic surgical system is presented. The logic of operation and examples of images reconstructed with a high spatial resolution algorithm are illustrated. The experimentally determined measurement of an electrode tip localization with this system is within 1 pixel or +/- 0.5 mm in any direction.

General Surgery↗
PubMed1992

Pressure ulcers in adults: prediction and prevention. Quick reference guide for clinicians. Agency for Health Care Policy And Research.

These guidelines are presented in a user-friendly format for quick reference in daily practice. The goals are to: 1) identify at-risk individuals needing prevention and the specific factors placing them at risk; 2) maintain and improve tissue tolerance to pressure in order to prevent injury; 3) protect against the adverse effects of external mechanical forces; and 4) reduce the incidence of pressure ulcers through educational programs. An algorithm helps to specify appropriate prevention measures.

Adult↗
PubMed1989

[Acute renal insufficiency after the administration of tetracycline and gentamycin].

The clinical course of eight case reports of patients with acute renal failure after administration of nephrotoxic antibiotics--specially of tetracycline and gentamycin--is demonstrated. All patients were suffering on preexisting nephropathy, many of them in stage of chronic renal failure according to various etiopathogenesis. As concomitant factor inducing acute renal failure together with antibiotics are: elderly, hepatopathy, surgical interventions, administration of other nephrotoxic drugs. In 6 patients, where acute renal failure induced by nonreducted doses of antibiotics appeared, the treatment was successful, in five cases due to short term haemodialysis, once conservatively with diuretics and volume diuresis. Two patients died before the therapeutic measures and dialysis could be performed. Algorithms in diagnosis and treatment of chronic renal failure--patients where antibiotic treatment is necessary are discussed.

Acute Kidney Injury↗
PubMed1985

The Pennsylvania Plan II: an algorithm for the management of lumbar degenerative disc disease.

We have thus presented a series of decision-making processes that are easy to follow, clearly defined, and cost effective. We have found that with the use of this decision-making algorithm our patients receive the therapeutic measures most helpful at the optimal time and are neither denied helpful surgery nor submitted to operations that are useless surgical exercises. With the use of this protocol, we believe that our efficiency as surgeons, physicians, and advisors will increase and the specter of fear found in the general population regarding low back pain will diminish.

Adult↗
PubMedDate not supplied

Blood flow determinations utilizing digital densitometry.

A method of obtaining relative and absolute blood flow measurements from digital densitometry was evaluated with a simulated vessel phantom and a hydrodynamic model. A digital vascular imaging system capable of acquisition in 512(2) and 1024(2) mode was used. Relative and absolute blood flow were measured using parameters derived from the densitometric curve. Since application of densitometric data to absolute flow measurements requires the vessel diameter, an algorithm for vessel size determination was created. Gray scale changes were demonstrated to be linearly related to contrast concentration. The variance of vessel size determination was significantly different in all combinations of 1024(2) and 512(2) imaging with 15 cm or 35 cm field size. The error in vessel size determination was significantly less using the larger 1024(2) matrix and the smaller 15 cm image intensifier field size, as shown by the smaller variance. In relative flow determinations, there was good correlation between the flow and four parameters of the densitometric curve with no significant differences between 512(2) and 1024(2) imaging. Absolute flow determinations had slightly lower correlation to actual flow but were not significantly different from relative flow determinations. Relative and absolute blood flow determinations can be performed adequately with either 512(2) or 1024(2) imaging. The increased accuracy in vessel size determination with 1024(2) imaging makes this high resolution system potentially preferable to determine absolute blood flow.

Absorptiometry, Photon↗
PubMed1985

A count-based algorithm for attenuation-corrected volume determination using data from an external flood source.

We discuss the basic features of a count-based algorithm for attenuation-corrected volume determination, for use with planar gamma camera images. The attenuation correction is arrived at by combining the results of two 180 degrees opposed images with a transmission image obtained with an external flood source. A sample of the imaged radioactive volume is used to convert the attenuation-corrected count to an absolute volume. The algorithm is best suited to the measurement of small to medium-sized volumes of uniform activity, such as are encountered in cardiac blood-pool imaging.

Heart↗
PubMed1979

An algorithm for the operational assessment of adverse drug reactions. III. Results of tests among clinicians.

To determine how practicing clinicians use a recently developed algorithm for the diagnostic assessment of suspected adverse drug reactions (ADRs), eight clinicians--four board-certified, practicing physicians and four interns--rated the likelihood of 30 suspected ADRs. Each physician reviewed the case summaries, first using implicit clinical judgment and two months later by means of the ADR algorithm. The algorithm significantly improved the reproducibility of the senior clinicians' assessments as compared with their implicit assessments; however, the improvement in the interns' assessments with the algorithm was not significant. The validity of the physicians' assessments, which was measured by comparing their ratings with a consensus rating of the three algorithm developers, was also significantly improved by the use of the algorithm. When used by practicing clinicians, the algorithm improves the reproducibility and validity of their assessments of ADRs and should provide a more precise diagnostic approach to these complex clinical phenomena.

Child↗
PubMed1977

An operator-independent method for background subtraction in adrenal-uptake measurements: concise communication.

A new computer program for adrenal-uptake measurements is presented in which the algorithm identifies the adrenal and background regions automatically after being given a starting point in the image. Adrenal uptakes and results of reproducibility tests are given for patients injected with [131I] 6beta-iodomethyl-19-norcholesterol. The data to date indicate no overlap in the percent-of-dose uptakes for normal patients and patients with Cushing's disease and Cushing's syndrome.

Cholesterol↗
PubMed1995

In vivo validation of an experimental adaptive quantitative coronary angiography algorithm to circumvent overestimation of small luminal diameters.

The reliability of quantitative coronary angiography (QCA) measurements is of fundamental importance for the study and practice of interventional cardiology. In vivo validation results have consistently reported a tendency for QCA systems to overestimate small luminal diameters. Such a systematic error may result in the underestimation of luminal gain during intracoronary procedures and in the underestimation of progression of coronary artery disease during longitudinal studies. We report the in vivo validation results of an experimental adaptive edge-detection algorithm that was developed to reduce overestimation of small luminal diameters by incorporating a dynamic function of variable kernel size of the derivative operator and variable weighting of the first and second derivatives of the brightness profile. The results of the experimental algorithm were compared to those of the conventional parent edge detection algorithm with fixed parameters. Dynamic adjustment of the edge-detection algorithm parameters was found to improve measurements of small (< 0.8-mm) luminal diameters as evidenced by an intercept of +.07 mm for the algorithm with variable weighting compared to +0.21 mm for the parent algorithm with fixed weighting. A slope of < 1 was found for both the parent and experimental algorithms with subsequent underestimation of large luminal diameters. Systematic errors in a QCA system can be identified and corrected by the execution of objective in vivo validation studies and the consequent refinement of edge-detection algorithms. The overestimation of small luminal diameters may be overcome by the incorporation of a dynamic edge-detection algorithm.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1987

Techniques for the observation and measurement of red blood cell velocity in vessels of the guinea pig cochlea.

Fluorescence techniques combined with intravital microscopy provide a powerful approach to the study of cochlear blood microcirculation. In the current study, fluorescein isothiocyanate conjugated to high molecular weight dextrans was added to plasma to enhance the visual contrast of flowing blood in microscopic images from the guinea pig cochlea. Photometric signals, obtained from video pictures of the blood vessels, provided a means to continuously measure red cell velocity by using crosscorrelation algorithms to extract the time delay for moving features of the image. Alternatively, a small amount of fluorescently-labeled red blood cells (RBCs) were added to the vascular volume to serve as natural indicators of whole blood flow. The speed of these cells was measured by video photometric detection of the time required for the cells to pass between two predetermined positions in the television image. RBCs can be made fluorescent by chemical bonding of a fluorochrome to the cell membrane or by internal loading of the cell with an inert fluorochrome. Labeled RBCs provide a means to determine blood velocity in capillaries having extremely poor optical contrast, a situation which is generally the case for relatively thick tissues such as the lateral wall of the membranous labyrinth.

Animals↗