Ratio-based Method Research Articles

Overlap-coefficient for the relationship between mesh size and defect size in laparoscopic ventral hernia surgery

In laparoscopic ventral hernia surgery, the ideal overlap in order to secure in-growth is regarded by many authors as 5 cm in every direction from the abdominal wall defect, and many authors have the impression that larger hernias need a larger overlap. Exact placement of the mesh is mandatory for exact overlap, but calculating an overlap by 5 cm, i.e. a mesh 10 cm larger than the defect in all directions, will probably allow for some variation in placement and shrinkage—and still allow secure in-growth. Attempts to calculate mesh-defect ratios have been founded on area calculations or defect-size-mesh-size ratios. In a search for a simpler parameter to express overlap, I found no area-based or ratio-based method that could be applied easily to statistical analysis. In order to achieve a simply expressed parameter for statistical analysis, I hereby propose the following overlap coefficient: The proposed coefficient is based on the assumption of an ideal overlap as a ratio expressed by a single number. The coefficient can be modified easily if different assumptions of ideal overlap are made. The coefficient is calculated from the least overlap in two directions—length and width of mesh versus defect, respectively—therefore yielding a logical argument: the least overlap is decisive. When dividing the difference between mesh size and defect size by the desired overlap one gets a number, the coefficient. If the overlap is 4 cm, where one wants 5 cm, the number becomes k = 0.8—i.e. 20% ‘‘off target’’. Conversely, if the overlap is 6 cm the number becomes k = 1.2; also 20% ‘‘off target’’ but to the ‘‘good side’’. The same deviation is expressed if one defines another target for overlap, e.g. a 3-cm overlap when 4 cm would be desirable: k = 0.75. Thus, ideal and exact overlap should give a coefficient, k = 1; larger overlaps are[1 and smaller overlaps\1. The smallest value for length versus width is decisive, as the defect size is measured by two simple perpendicular estimates and corresponding mesh placement. In the example with 5 cm as the ideal overlap, a constant can be established: 1/(5 cm ? 5 cm) = 0.1 cm. Formula (logical argument):

The Elastic Ratio: Introducing Curvature Into Ratio-Based Image Segmentation

We present the first ratio-based image segmentation method that allows imposing curvature regularity of the region boundary. Our approach is a generalization of the ratio framework pioneered by Jermyn and Ishikawa so as to allow penalty functions that take into account the local curvature of the curve. The key idea is to cast the segmentation problem as one of finding cyclic paths of minimal ratio in a graph where each graph node represents a line segment. Among ratios whose discrete counterparts can be globally minimized with our approach, we focus in particular on the elastic ratio [Formula: see text] that depends, given an image I, on the oriented boundary C of the segmented region candidate. Minimizing this ratio amounts to finding a curve, neither small nor too curvy, through which the brightness flux is maximal. We prove the existence of minimizers for this criterion among continuous curves with mild regularity assumptions. We also prove that the discrete minimizers provided by our graph-based algorithm converge, as the resolution increases, to continuous minimizers. In contrast to most existing segmentation methods with computable and meaningful, i.e., nondegenerate, global optima, the proposed approach is fully unsupervised in the sense that it does not require any kind of user input such as seed nodes. Numerical experiments demonstrate that curvature regularity allows substantial improvement of the quality of segmentations. Furthermore, our results allow drawing conclusions about global optima of a parameterization-independent version of the snakes functional: the proposed algorithm allows determining parameter values where the functional has a meaningful solution and simultaneously provides the corresponding global solution.

Estimate of maintenance EPO to darbepoetin alfa dose conversion ratio in a hospital-based dialysis patient population

Background:Epoetin alfa (EPO) and darbepoetin alfa are erythropoiesis-stimulating agents (ESAs) used to treat anemia in patients with chronic kidney disease. EPO and darbepoetin alfa have a non-proportional dose conversion relationship across the dosing spectrum. However, reports comparing the dose relationship between the two ESAs do not adjust for the non-proportional dose relationship or for population differences. Because drug cost is directly related to dosage, appropriate methods to assess the dose relationship between the two ESAs are important to understand the economic implications of converting patient populations from one ESA treatment to another.Objective:To describe dose conversion methods that take into account the non-proportional dose relationship between EPO and darbepoetin alfa, and calculate the dose conversion ratio (DCR) between the two ESAs in a hospital-based dialysis patient population.Methods:This was a retrospective observational study where longitudinal data from medical charts were collected for chronic hemodialysis patients being treated at hospital-based dialysis centers. Mean maintenance DCRs were calculated at the population level for hemodialysis patients converted from EPO to darbepoetin alfa treatment and subsequently maintained on darbepoetin alfa. Two methods were used to determine the DCRs: a regression-based method using ordinary least squares regression, and ratio-based method using an arithmetic mean.Results:The estimated population mean maintenance DCR for the population in this analysis was 320:1 (Units EPO:µg darbepoetin alfa) using the regression-based method, and 350:1 using the ratio-based method. Sensitivity analysis yielded DCRs ranging from 311 to 333:1.Conclusions:The two methods in estimating the DCR presented here provide payers with an empirical way of comparing ESA utilization for pharmacoeconomic evaluation. DCR results may vary according to patient characteristics; however, mean DCRs of greater than 300:1 were obtained in this analysis. Exclusion of other patient-related factors that may influence ESA dose is a possible limitation of the study.

Supervised training database for building recognition by using cross ratio invariance and SVD-based method

This paper describes an approach to training a database of building images under the supervision of a user. Then it will be applied to recognize buildings in an urban scene. Given a set of training images, we first detect the building facets and calculate their properties such as area, wall color histogram and a list of local features. All facets of each building surface are used to construct a common model whose initial parameters are selected randomly from one of these facets. The common model is then updated step-by-step by spatial relationship of remaining facets and SVD-based (singular value decomposition) approximative vector. To verify the correspondence of image pairs, we proposed a new technique called cross ratio-based method which is more suitable for building surfaces than several previous approaches. Finally, the trained database is used to recognize a set of test images. The proposed method decreases the size of the database approximately 0.148 times, while automatically rejecting randomly repeated features from the scene and natural noise of local features. Furthermore, we show that the problem of multiple buildings was solved by separately analyzing each surface of a building.

Conditioning of reflectance signals by linear diffusion for improving narrow-band ratio-based remote-sensing bottom depth retrieval in shallow coastal waters

Ratio-based bottom depth-retrieval algorithms are conceptually simple relative to other algorithms and can be effective. The objective of this study was to determine the utility of imposing a spatial-smoothing assumption on three ratio-based, feed-forward remote-sensing bathymetry algorithms: Polcyn et al., Stumpf et al., and Dierssen et al. We consider three smoothing operators: median, Savitzky-Golay, and linear diffusion with data fidelity, applied in three domains: spatial, spectral, and spectral-spatial. Thus, we consider nine smoothing methods. In addition, we consider two points at which smoothing is applied: one before the inversion process (pre-smoothing) and the other after the inversion process (post-smoothing). Our new formulations were tested with synthetic data, in situ remote-sensing reflectance, and simultaneous acoustic bathymetry, acquired in optically shallow waters. Analysis and results from the synthetic-data experiment indicate that pre-smoothing method is more effective than post-smoothing method. The field-data experiments indicate that spatial-domain smoothing is effective regardless of the type of smoothing operator, whereas spectral smoothing is not. Spectral-spatial-domain smoothing is as effective as spatial-domain smoothing, but is prone to over-segmentation. Effectiveness of spatial pre-smoothing was observed with every ratio-based inversion method, which suggests potential universal applicability of smoothing operators to ratio-based algorithms.

FET PET for the evaluation of untreated gliomas: correlation of FET uptake and uptake kinetics with tumour grading

Treatment and prognosis of gliomas depend on their histological tumour grade. The aim of the study was to evaluate the potential of [(18)F]fluoroethyltyrosine (FET) PET for non-invasive tumour grading in untreated patients. Dynamic FET PET studies were performed in 54 patients who, based on MRI, were estimated to have low grade (LG; n = 20), intermediate (WHO II-III; n = 4) or high grade (HG; n = 30) tumours. For standard evaluation, tumour SUV(max) and the ratio to background (SUV(max)/BG) were calculated (sum image: 20-40 min). For dynamic evaluation, mean SUV values within a 90% isocontour ROI (SUV90) and the SUV90/BG ratios were determined for each time frame to evaluate the course of FET uptake. Results were correlated with histopathological findings from PET-guided stereotactic biopsies. Histology revealed gliomas in all patients. Using the standard method a statistically significant difference (p = 0.001) was found between LG (n = 20; SUV(max)/BG: 2.16 +/- 0.98) and HG (n = 34; SUV(max)/BG: 3.29 +/- 1.06) gliomas (opt. threshold 2.58: SN71%/SP85%/area under ROC curve [AUC]:0.798), however, with a marked overlap between WHO II to IV tumours. Time activity curves showed slight increase in LG, whereas HG tumours presented with an early peak (10-20 min) followed by a decrease. Dynamic evaluation successfully separated LG from HG gliomas with higher diagnostic accuracy (SN94%/SP100%/AUC:0.967). Based on the ratio-based method, a statistically significant difference was found between LG and HG gliomas. Due to the interindividual variability, however, no reliable individual grading was possible. In contrast, dynamic evaluation allowed LG and HG gliomas to be differentiated with high diagnostic power and, thus, should supplement the conventional method.

Nitrous oxide emissions from drained organic forest soils––an up-scaling based on C:N ratios

Total emissions of N2O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N2O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from Histosols amount to 2,820 tonnes N2O a−1. This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel on Climate Change: 580 tonnes N2O a−1. The higher value in the present study can mainly be explained by improved accuracy of estimates of N2O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols, there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount to 1,890 tonnes of N2O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N2O a−1, which, if added, would increase the current estimate of the Swedish anthropogenic N2O source strength by 18%. Of these emissions, 88% occur from sites with C:N ratios lower than 25. The exponential relationship between C:N ratio and N2O emissions, in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However, by using the C:N ratio-based method, N2O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that there are exceptionally large emissions of N2O from the most nitrogen-rich drained organic forest soils are taken into account.

Soft Counting Poisson Mixture Model-Based Polling Method for Speech/Nonspeech Classification

In this letter, a new segment-level speech/nonspeech classification method based on the Poisson polling technique is proposed. The proposed method makes two modifications from the baseline Poisson polling method to further improve the classification accuracy. One of them is to employ Poisson mixture models to more accurately represent various segmental patterns of the observed frequencies for frame-level input features. The other is the soft counting-based frequency estimation to improve the reliability of the observed frequencies. The effectiveness of the proposed method is confirmed by the experimental results showing the maximum error reduction of 39% compared to the segmentally accumulated log-likelihood ratio-based method.

Comparing median lethal concentration values using confidence interval overlap or ratio tests

Experimenters in toxicology often compare the concentration-response relationship between two distinct populations using the median lethal concentration (LC50). This comparison is sometimes done by calculating the 95% confidence interval for the LC50 for each population, concluding that no significant difference exists if the two confidence intervals overlap. A more appropriate test compares the ratio of the LC50s to 1 or the log(LC50 ratio) to 0. In this ratio test, we conclude that no difference exists in LC50s if the confidence interval for the ratio of the LC50s contains 1 or the confidence interval for the log(LC50 ratio) contains 0. A Monte Carlo simulation study was conducted to compare the confidence interval overlap test to the ratio test. The confidence interval overlap test performs substantially below the nominal alpha = 0.05 level, closer to p = 0.005; therefore, it has considerably less power for detecting true differences compared to the ratio test. The ratio-based method exhibited better type I error rates and superior power properties in comparison to the confidence interval overlap test. Thus, a ratio-based statistical procedure is preferred to using simple overlap of two independently derived confidence intervals.

Wavelet-Based Cascaded Adaptive Filter for Removing Baseline Drift in Pulse Waveforms

This paper presents an energy ratio-based method and a wavelet-based cascaded adaptive filter (CAF) for detecting and removing baseline drift from pulse waveforms. Experiments on 50 simulated and five hundred real pulse signals demonstrate that this CAF outperforms traditional filters both in removing baseline drift and in preserving the diagnostic information of pulse waveforms.

An adaptive web page layout structure for small devices

The limited display size of current small Internet devices is becoming a serious obstacle to information access. In this paper, we introduce a Document REpresentation for Scalable Structures (DRESS) to help information providers make composite documents, typically web pages, scalable in both logic and layout structure to support effective information acquisition in heterogeneous environments. Through this novel document representation structure based on binary slicing trees, the document can dynamically adapt its presentation according to display sizes by maximizing the information throughput to users. We discuss the details of this structure with its key attributes. An automatic approach for generating this structure for existing web pages is also presented. A branch-and-bound algorithm and a capacity ratio-based slicing method are proposed to select proper content representation and aesthetic document layouts respectively. A set of user study experiments have been carried out and the results show that compared with the thumbnail-based approach, the DRESS-based interface can reduce browsing time by 23.5%.

Characterization of dye‐induced mobility shifts affecting DNA sequencing in poly(ethylene oxide) sieving matrix

The influence of three classes of fluorescence labels including dipyrrometheneboron difluoride (BODIPY), energy transfer (ET) and conventional fluorescein and rhodamine (ABI), on DNA sequencing has been examined with laser-induced fluorescence detection and poly(ethylene oxide)-filled capillary electrophoresis. DNA sequencing fragments were generated by dye-labeled primer cycle-sequencing reactions in a hot-air thermal cycler. A parameter, relative-induced shift, was introduced to quantify the uniformity of electrophoretic mobilities of these fragments. BODIPY was found to have the smallest, but nonzero, effect for dye-induced nonuniformity. Although ET dyes provided the highest sensitivity due to their unique spectroscopic properties, they were found to lack photostability compared to BODIPY and ABI dyes. Characterization also brings out some important tips for selecting the suitable dye set for the two-channel ratio-based DNA base-calling method.

The number of illegal migrants of Mexican origin in the United States: Sex ratio-based estimates for 1980

This article reports the results of applying a sex ratio-based method to estimate the number of undocumented Mexicans residing in the United States in 1980. The approach centers on a comparison between the hypothetical sex ratio one would expect to find in Mexico in the absence of emigration to the United States and the sex ratio that is in fact reported in preliminary results from the 1980 Mexican Census. The procedure involves, inter alia, assuming a range of values for the sex ratio at birth and for census coverage differentials by sex in Mexico. Even the combinations of these values most likely to result in large estimates suggest that no more than 4 million illegal migrants of Mexican origin were residing in the United States in 1980.