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PubMed1996

Identification of anovulation and transient luteal function using a urinary pregnanediol-3-glucuronide ratio algorithm.

The sensitivity and specificity of a urinary pregnanediol-3-glucuronide (PdG) ratio algorithm to identify anovulatory cycles was studied prospectively in two independent populations of women. Urinary hormone data from the first group was used to develop the algorithm, and data from the second group was used for its validation. PdG ratios were calculated by a cycles method in which daily PdG concentrations indexed by creatinine (CR) from cycle day 11 onward were divided by a baseline PdG (average PdG/Cr concentration for cycle days 6-10). In the interval method, daily PdG/CR concentrations from day 1 onward were divided by baseline PdG (lowest 5-day average of PdG/CR values throughout the collection period). Evaluation of the first study population (n = 6) resulted in cycles with PdG ratios > or = 3 for > or = 3 consecutive days being classified as ovulatory; otherwise they were anovulatory. The sensitivity and specificity of the PdG ratio algorithm to identify anovulatory cycles in the second population were 75% and 89.5%, respectively, for all cycles (n = 88); 50% and 88.3% for first cycles (n = 40) using the cycles method; 75% and 92.2%, respectively, for all cycles (n = 89); and 50% and 94.1% for first cycles (n = 40) using the interval method. The "gold standard" for anovulation was weekly serum samples < or = 2 ng/ml progesterone. The sensitivity values for all cycles and for the first cycle using both methods were underestimated because of apparent misclassification of cycles using serum progesterone due to infrequent blood collection. Blood collection more than once a week would have greatly improved the sensitivity and modestly improved the specificity of the algorithm. The PdG ratio algorithm provides an efficient approach for screening urine samples collected in epidemiologic studies of reproductive health in women.

Adult↗

PubMed2003

Convergent validity of the ASAM Patient Placement Criteria using a standardized computer algorithm.

The study examined the convergent validity of the ASAM Patient Placement Criteria (PPC) by comparing Level of Care (LOC) recommendations produced by two alternative methods: a computerdriven algorithm and a "standard" clinical assessment. A cohort of 248 applicants for alcoholism treatment were evaluated at a multi-modality treatment center. The two methods disagreed (58% of cases) more often than they agreed (42%). The algorithm recommended a more intense LOC than the clinician protocol in 81% of the discrepant cases. Four categories of disagreement accounted for 97% of the discrepant cases. Several major sources of disagreement were identified and examined in detail: clinicians' reasoned departures from the PPC rules, conservatism in algorithm LOC recommendations, and measurement overlap between two specific dimensions. In order for the ASAM PPC and its associated algorithm to be embraced by treatment programs, the observed differences in LOC recommendations between the algorithm and "standard" clinical assessment should be resolved.

Algorithms↗

PubMed2005

70/30 insulin algorithm versus sliding scale insulin.

BACKGROUND: The medical literature supports the fact that sliding scale dosing of insulin is an ineffective means to control blood glucose concentrations. Despite this, many clinicians still use sliding scale insulin (SSI) regimens. A better tool for controlling hyperglycemia is clearly needed. OBJECTIVE: To compare the efficacy of an algorithm using 70/30 insulin with traditional SSI dosing for glycemic control in hospitalized patients with type 2 diabetes. METHODS: A prospective, cohort, comparative trial was conducted at a 644-bed, 2-hospital, regional referral health system. Patients were screened for enrollment based on orders received in the pharmacy for sliding scale dosing of insulin. Patients were treated either following an algorithm using 70/30 insulin twice daily or traditional SSI dosing as written by the prescribing physician. RESULTS: Twenty patients with type 2 diabetes were involved in this pilot trial: 10 were treated with the 70/30 insulin algorithm and 10 received a physician-determined traditional SSI regimen. Patients treated based on the 70/30 insulin algorithm achieved better glycemic control (p = 0.042). No difference between the groups was detected in the average number of insulin units administered, insulin injections, or days patients spent on their respective insulin regimens. CONCLUSIONS: Glycemic control with the 70/30 insulin algorithm was superior to traditional SSI dosing.

Algorithms↗

PubMed2002

Semi-three-dimensional algorithm for time-resolved diffuse optical tomography by use of the generalized pulse spectrum technique.

Although a foil three-dimensional (3-D) reconstruction with both 3-D forward and inverse models provide, the optimal solution for diffuse optical tomography (DOT), because of the 3-D nature of photon diffusion in tissue, it is computationally costly for both memory requirement and execution time in a conventional computing environment. Thus in practice there is motivation to develop an image reconstruction algorithm with dimensional reduction based on some modeling approximations. Here we have implemented a semi-3-D modified generalized pulse spectrum technique for time-resolved DOT, where a two-dimensional (2-D) distribution of optical properties is approximately assumed, while we retain 3-D distribution of photon migration in tissue. We have validated the proposed algorithm by reconstructing 3-D structural test objects from both numerically simulated and experimental date. We demonstrate our algorithm by comparing it with the calibrated 2-D reconstruction that is in widespread use as a shortcut to 3-D imaging and proving that the semi-3-D algorithm outperforms the calibrated 2-D algorithm.

Algorithms↗

PubMed2001

Fast maximum-likelihood image-restoration algorithms for three-dimensional fluorescence microscopy.

We have evaluated three constrained, iterative restoration algorithms to find a fast, reliable algorithm for maximum-likelihood estimation of fluorescence microscopic images. Two algorithms used a Gaussian approximation to Poisson statistics, with variances computed assuming Poisson noise for the images. The third method used Csiszar's information-divergence (I-divergence) discrepancy measure. Each method included a nonnegativity constraint and a penalty term for regularization; optimization was performed with a conjugate gradient method. Performance of the methods was analyzed with simulated as well as biological images and the results compared with those obtained with the expectation-maximization-maximum-likelihood (EM-ML) algorithm. The I-divergence-based algorithm converged fastest and produced images similar to those restored by EM-ML as measured by several metrics. For a noiseless simulated specimen, the number of iterations required for the EM-ML method to reach a given log-likelihood value was approximately the square of the number required for the I-divergence-based method to reach the same value.

Algorithms↗

PubMed2003

Improved piecewise orthogonal signal correction algorithm.

Piecewise orthogonal signal correction (POSC), an algorithm that performs local orthogonal filtering, was recently developed to process spectral signals. POSC was shown to improve partial leastsquares regression models over models built with conventional OSC. However, rank deficiencies within the POSC algorithm lead to artifacts in the filtered spectra when removing two or more POSC components. Thus, an updated OSC algorithm for use with the piecewise procedure is reported. It will be demonstrated how the mathematics of this updated OSC algorithm were derived from the previous version and why some OSC versions may not be as appropriate to use with the piecewise modeling procedure as the algorithm reported here.

Algorithms↗

PubMed1998

Interpretive algorithms for the symptom-limited exercise test: assessing dyspnea in Persian Gulf war veterans.

Interpretation of symptom-limited exercise testing requires analysis of a large body of simultaneously recorded cardiopulmonary data. Karlman Wasserman has recommended an algorithmic approach to interpretation (WA) that leads to a dichotomous choice between pulmonary and cardiovascular impairment. An alternative algorithm published by William Eschenbacher (EA) provides for concurrent assessment of cardiovascular and pulmonary exercise impairment. We analyzed a group of 29 individuals referred to the Pulmonary Physiology Laboratory at the Washington Veterans Affairs Medical Center for evaluation of dyspnea following service in the Persian Gulf War to assess the concordance of the two algorithms in determining the cause of dyspnea and exercise impairment in these individuals. They each performed a progressive, ramped, symptom-limited exercise test on a bike for a minimum of 6 min. Exercise measurements were analyzed by both interpretive algorithms. Concordance was found in 28% of tests. The greatest discordance occurred in identifying pulmonary limitation. Eleven had pulmonary limitation by EA; of these, WA found 1 to have pulmonary limitation, 5 to be normal, 4 indeterminate, and 1 musculoskeletal limitation. Of the 11 with pulmonary limitation by EA, but not by WA, 5 had abnormal resting pulmonary function measurements. Analysis of the differences between these two interpretive approaches is given. The EA algorithm may be more sensitive for detecting exercise impairment of pulmonary origin, but its specificity remains to be determined.

Adult↗

PubMed2001

A new detection algorithm for implantable cardioverter defibrillator.

One of the most important subsystems of implantable cardioverter defibrillator (ICD) is the sensing stage, since it determines the sensitivity and specificity of the device to detect the heart rate and the underlying arrhythmia. This paper aims to investigate a new detection algorithm for ICD, which operates fully automatically. The algorithm ARGUS was implemented as a computer model and tested with intracardiac electrograms recorded (band-pass: 0.05 to 500 Hz; sampling rate: 1-4 kHz) under different rhythm condition like sinus rhythm (n = 18), atrial tachycardia (n = 16), and ventricular tachycardia as well as fibrillation (n = 139) during electrophysiological tests or ICD implantation. The results of the tests were visually inspected on a beat-to-beat basis. In total 31,934 events were classified by the algorithm (18,758 as long intervals (LI) with cycle length > 300 ms; 13,176 as short intervals (SI)). 195 out of the 13,176 SI and 572 out of 18,758 LI were incorrectly classified (SI: 1.48%; LI: 3.05%). In conclusion the new algorithm yield high sensitivity (99.9%) and specificity (97.0%) as known from conventional ICD algorithms but need no manual adjustments.

Algorithms↗

PubMed2004

A fast global fitting algorithm for fluorescence lifetime imaging microscopy based on image segmentation.

Global fitting algorithms have been shown to improve effectively the accuracy and precision of the analysis of fluorescence lifetime imaging microscopy data. Global analysis performs better than unconstrained data fitting when prior information exists, such as the spatial invariance of the lifetimes of individual fluorescent species. The highly coupled nature of global analysis often results in a significantly slower convergence of the data fitting algorithm as compared with unconstrained analysis. Convergence speed can be greatly accelerated by providing appropriate initial guesses. Realizing that the image morphology often correlates with fluorophore distribution, a global fitting algorithm has been developed to assign initial guesses throughout an image based on a segmentation analysis. This algorithm was tested on both simulated data sets and time-domain lifetime measurements. We have successfully measured fluorophore distribution in fibroblasts stained with Hoechst and calcein. This method further allows second harmonic generation from collagen and elastin autofluorescence to be differentiated in fluorescence lifetime imaging microscopy images of ex vivo human skin. On our experimental measurement, this algorithm increased convergence speed by over two orders of magnitude and achieved significantly better fits.

Algorithms↗

PubMed2005

Priority areas for anuran conservation using biogeographical data: a comparison of greedy, rarity, and simulated annealing algorithms to define reserve networks in cerrado.

Spatial patterns in biodiversity variation at a regional scale are rarely taken into account when a natural reserve is to be established, despite many available methods for determining them. In this paper, we used dimensions of occurrence of 105 species of Anura (Amphibia) in the cerrado region of central Brazil to create a regional system of potential areas that preserves all regional diversity, using three different algorithms to establish reserve networks: "greedy", rarity, and simulated annealing algorithms. These generated networks based on complementarity with 10, 12, and 8 regions, respectively, widely distributed in the biome, and encompassing various Brazilian states. Although the purpose of these algorithms is to find a small number of regions for which all species are represented at least once, the results showed that 67.6%, 76.2%, and 69.5% of the species were represented in two or more regions in the three networks. Simulated annealing produced the smallest network, but it left out three species (one endemic). On the other hand, while the greedy algorithm produce a smaller solution, the rarity-based algorithm ensured that more species were represented more than once, which can be advantageous because it takes into consideration the high levels of habitat loss in the cerrado. Although usually coarse, these macro-scale approaches can provide overall guidelines for conservation and are useful in determining the focus for more local and effective conservation efforts, which is especially important when dealing with a taxonomic group such as anurans, for which quick and drastic population declines have been reported throughout the world.

Algorithms↗

PubMedDate not supplied

An adaptive ant colony system algorithm for continuous-space optimization problems.

Ant colony algorithms comprise a novel category of evolutionary computation methods for optimization problems, especially for sequencing-type combinatorial optimization problems. An adaptive ant colony algorithm is proposed in this paper to tackle continuous-space optimization problems, using a new objective-function-based heuristic pheromone assignment approach for pheromone update to filtrate solution candidates. Global optimal solutions can be reached more rapidly by self-adjusting the path searching behaviors of the ants according to objective values. The performance of the proposed algorithm is compared with a basic ant colony algorithm and a Square Quadratic Programming approach in solving two benchmark problems with multiple extremes. The results indicated that the efficiency and reliability of the proposed algorithm were greatly improved.

Algorithms↗

PubMed2004

A modified multitarget adaptive array algorithm for wireless CDMA system.

The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system.

Algorithms↗

PubMed2004

A fast Monte Carlo algorithm to simulate the spectrum of DNA damages formed by ionizing radiation.

Ionizing radiation produces both singly and multiply damaged DNA sites. Multiply damaged sites (MDS) have been implicated in radiation-induced cell killing and mutagenesis. The spatial distribution of elementary damages (strand breaks and base damages) that constitute MDS is of special interest, since the complexity of MDS has an impact on damage repair. A fast and easy-to-implement algorithm to simulate the local clustering of elementary damages produced by ionizing radiation is proposed. This algorithm captures the major trends in the DNA damage spectrum predicted using detailed track- structure simulations. An attractive feature of the proposed algorithm is that only four adjustable parameters need to be identified to simulate the formation of DNA damage. A convenient recipe to determine the parameters used in the fast Monte Carlo damage simulation algorithm is provided for selected low- and high-LET radiations. The good agreement among the damage yields predicted by the fast and detailed damage formation algorithms suggests that the small-scale spatial distribution of damage sites is determined primarily by independent and purely stochastic events and processes.

Algorithms↗

PubMed2004

Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms.

BACKGROUND: Differentiation between septic arthritis and transient synovitis of the hip in children can be difficult. Kocher et al. recently developed a clinical prediction algorithm for septic arthritis based on four clinical variables: history of fever, non-weight-bearing, an erythrocyte sedimentation rate of >or=40 mm/hr, and a serum white blood-cell count of >12000/mm(3) (>12.0 x 10(9)/L). The purpose of this study was to apply this clinical algorithm retrospectively to determine its predictive value in our patient population. METHODS: A retrospective review was performed to identify all children who had undergone a hip arthrocentesis for the evaluation of an irritable hip at our institution between 1992 and 2000. One hundred and sixty-three patients with 165 involved hips satisfied the criteria for inclusion in the study and were classified as having true septic arthritis (twenty hips), presumed septic arthritis (twenty-seven hips), or transient synovitis (118 hips). RESULTS: Patients with septic arthritis (true and presumed; forty-seven hips) differed significantly (p < 0.05) from patients with transient synovitis (118 hips) with regard to the erythrocyte sedimentation rate, differential of serum white blood-cell count, total white blood-cell count and differential in the synovial fluid, gender, previous health-care visits, and history of fever. If the four independent multivariate predictors of septic arthritis proposed by Kocher et al. were present, the predicted probability of the patient having septic arthritis was 59% in our study, in contrast to the 99.6% predicted probability in the patient population described by Kocher et al. Statistical analyses demonstrated that the best model to describe our patient population was based on three variables: a history of fever, a serum total white blood-cell count of >12000/mm(3) (>12.0 x 10(9)/L), and a previous health-care visit. When all three variables were present, the predicted probability of the patient having septic arthritis was 71%. CONCLUSIONS: Although the use of a clinical prediction algorithm to differentiate between septic arthritis and transient synovitis may have improved the utility of existing technology and medical care to facilitate the diagnosis at the institution at which the algorithm originated, application of the algorithm proposed by Kocher et al. or of our three-variable model does not appear to be valid at other institutions.

Algorithms↗

PubMed1995

An imaging algorithm for the differential diagnosis of adrenal adenomas and metastases.

OBJECTIVE: The purpose of this study was to develop an algorithm using CT and chemical-shift MR imaging for the characterization of adrenal masses in patients with a primary cancer and no other evidence of metastatic disease. SUBJECTS AND METHODS: Thirty-three patients with 37 adrenal masses (19 metastases, 18 adenomas), all of whom had a known primary cancer, were studied with noncontrast CT and chemical-shift MR imaging (1.5 T). Lesion size and density in Hounsfield units (H) were determined by CT. Adrenal signal intensity normalized to that of spleen was used to calculate adrenal-spleen ratio (ASR), defined as the percentage of signal remaining in the opposed-phase image relative to the in-phase image. Lesions less than or equal to 0 H were classified as benign, lesions greater than 20 H were regarded as malignant, and lesions between 0 and 20 H were regarded as indeterminate. Diagnoses were confirmed by biopsy (for 19 lesions) or by follow-up imaging (for 18 lesions). An imaging algorithm was derived by determining the relative value of CT and MR imaging for diagnosing the lesions. The reimbursement rates for CT-guided biopsy and MR imaging of the abdomen were obtained from Medicare. RESULTS: All 13 lesions of 0 or less H were correctly classified as benign by CT. ASR was less than 70 in 10 of these 13. In another 13 lesions, H was greater than 20; all were malignant and all had an ASR greater than 80. Of 11 CT-indeterminate lesions, four of five adenomas had an ASR less than 70, and four of six metastases had an ASR greater than 80. Two malignant lesions had ASRs between 70 and 80 and were diagnosed by biopsy findings. One CT-indeterminate adenoma had an ASR of 84 and was diagnosed by biopsy findings. The reimbursement rate by Medicare is similar for CT-guided biopsy with pathologic interpretation and for MR imaging of the abdomen. CONCLUSION: An algorithm was developed for diagnosis of adrenal lesions that uses the density reading on noncontrast CT as the first step, with chemical-shift MR imaging for CT-indeterminate lesions. In this algorithm, lesions of 0 H or less may be regarded as benign and further work-up is not required. Lesions with a density greater than 20 H are likely malignant and should be biopsied when the result will influence management. For CT-indeterminate lesions, we recommend chemical-shift MR imaging. An ASR threshold of 70 indicates a benign lesion, and no further workup is required in these patients. Lesions with an ASR greater than 70 should have a biopsy performed, depending on the clinical situation. The above algorithm is cost-effective and reduces the number of biopsies required without reducing the sensitivity of detecting malignant lesions.

Adrenal Cortex↗

PubMed1987

Algorithmic diagnosis of jaundice.

Extensive clinical and clinical chemical information was collected from 1002 jaundiced patients. By applying Bayes' theorem and logistic discriminant analysis, a diagnostic algorithm was developed based upon 21 of the 107 variables collected. This algorithm permitted a probabilistic classification of jaundiced patients into four diagnostic categories: acute non-obstructive, chronic non-obstructive, benign obstructive and malignant obstructive jaundice. Of the 985 patients with a final diagnosis a correct probabilistic diagnosis (obstruction vs. non-obstruction) was suggested by the algorithm in 867 patients (88%). Adopting a probability limit of 0.80, 683 patients (69%) were correctly classified, 34 patients (3.5%) were wrongly so, and 268 patients (27%) could not be classified with a probability above 0.80 (doubtful cases). The algorithm was also tested in a further series of 110 jaundiced patients and found to perform equally well: 88 patients classified, 22 patients remaining doubtful. Patients with doubtful diagnoses should be referred to a non-invasive test such as ultrasound examination, whereas patients with definite diagnoses can be referred to invasive tests (liver biopsy, direct cholangiography) as appropriate. The diagnostic algorithm seems to be a valuable aid for the preliminary differential diagnosis of the jaundiced patient and can be used in the planning of a diagnostic strategy for the individual patient.

Algorithms↗

PubMed2002

Technical note: determining peeling order using sparse matrix algorithms.

To study the effect of individual genes by segregation or linkage analyses, the likelihood of the model needs to be evaluated. The likelihood can be computed efficiently using the Elston-Stewart algorithm. This algorithm involves summing over the unobserved genotypes in the pedigree, which is called peeling. An important aspect of this algorithm is to determine the order of peeling to maximize efficiency. This paper shows how determining peeling order is related to a problem in solving systems of symmetric sparse linear equations. It also shows how algorithms developed to efficiently solve those systems, can be used to determine the optimal order of peeling in the Elston-Stewart algorithm.

Algorithms↗

PubMed2006

Algorithms for dairy barn design: resting, feeding, and exercise.

This study presents a series of algorithms designed to assist farmers and other decision-makers in the design of dairy cattle housing. Four algorithms have been developed, each for a different basic design (2 rows head-to-head, 2 rows head-to-wall, 3 rows, or rows perpendicular to feed alley). Each algorithm requires input of herd size and various other parameters (e.g., free-stall width), depending on the design; the output gives barn layout and overall size, thus facilitating comparison of designs in terms of financial cost and animal welfare. Although these algorithms have been developed primarily for small family farms in Galicia (northwest Spain) with herd sizes of up to 250, they could be useful for herds of any size, because herd size is an input parameter. We consider that these algorithms are useful tools for dairy farm planning, and they can be readily incorporated into personal computer applications, greatly facilitating their application.

Algorithms↗