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Using composite health status measures to assess the nation's health.

Research in progress at the National Center for Health Statistics for evaluating the usefulness of composite measures of health status for assessing the nation's health is described. Three measures suitable for use in the general population, the Health Insurance Experiment-Functional Limitations (HIE-FL), the Health Utility Index (HUI), and the Quality of Well-being (QWB) scale, have been mapped to data collected in the 1980 National Health Interview Survey (NHIS). Analysis using current algorithms for making composite function status measures according to the QWB methods suggests that traditional single indicators of health tend to overestimate the level of health by about 10%. When symptoms and problems are added to the composite function score, the overestimate as measured by the single indicator is at least 50%. The authors are continuing to validate these algorithms, to develop similar ones for the HIE-FL and HUI, and to extend the analysis to data collected in 1977, 1979, and 1984. Current results indicate that to realize fully the benefits of composite measures, well-established, valid, and reliable measures of health-related quality of life should be included as part of the regular NHIS data collection procedures.

Activities of Daily Living

Skeletal measurements using a flying spot digital imaging device.

A flying spot digital imaging unit was devised to measure skeletal length and angles. This device uses a spinning chopper wheel and fixed slit collimator in front of a conventional X-ray tube to produce a scanning pencil beam that passes through the patient and onto an electronic detector. The beam scans the patient transversely and the device moves longitudinally, creating a digital image with a skin dose of less than 2 mrad (0.02 mGy). Patients can be imaged both when upright and when recumbent. A large field of view makes it possible for the entire length of the spine or lower extremities to be included in a single image. Built-in computer algorithms are used to make measurements of skeletal lengths and angles. The accuracy of the digital device was tested by making measurements of known angles and lengths using protractors and rulers. Skeletal measurements were then made on a number of patients. Interobserver error was tested using both patient and nonpatient images. The following patient measurements were made: Cobb angle in 166 patients with scoliosis; knee joint angles in 120 patients undergoing knee surgery; lower extremity lengths in 78 patients with length inequalities; bony fragment angulation and displacement in 30 patients with healing fractures. These studies have shown the device to be accurate with low interobserver error, while delivering much lower patient dose than more conventional methods. The ability to manipulate window levels and widths enables visualization of thick and thin body parts on the same image. Our experience both in the laboratory and with patients has been encouraging, and the method appears to have several advantages over more conventional techniques.

Bone and Bones

Depth dose under narrow shielding blocks: a comparison of measured and calculated dose.

This paper describes measurements done to investigate the accuracy of dose calculation algorithms when used to calculate the dose under shielding blocks. Because the prescribed dose is sometimes limited by the dose to organs at risk within the irradiated volume, it is important to know the dose under a block accurately. Five different algorithms from four treatment planning systems were used to calculate the dose under two narrow lead alloy blocks each placed centrally in a 15 x 15-cm beam of 6- and 18-MV X-rays, respectively. Measurements were done in a water phantom with the same geometrical set-up. All measured data have a common feature; a high surface dose (up to about 20%) decreasing linearly within the first 1-2 cm to a minimum ranging from 13 to 6.5%, and then increasing to a maximum depending on the X-ray energy and block width. Beyond the maximum, the dose decreases approximately linearly due to absorption of the primary beam. The first part of the curve is due essentially to secondary electrons. Beyond the minimum, the X-ray scatter dose component increases, due to increasing phantom scatter, to a maximum which is greater for 6 MV than for 18 MV X-rays. Most algorithms could not reproduce measured data accurately.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms

Hemodynamic and oxygen transport patterns for outcome prediction, therapeutic goals, and clinical algorithms to improve outcome. Feasibility of artificial intelligence to customize algorithms.

A generalized decision tree or clinical algorithm for treatment of high-risk elective surgical patients was developed from a physiologic model based on empirical data. First, a large data bank was used to do the following: (1) describe temporal hemodynamic and oxygen transport patterns that interrelate cardiac, pulmonary, and tissue perfusion functions in survivors and nonsurvivors; (2) define optimal therapeutic goals based on the supranormal oxygen transport values of high-risk postoperative survivors; (3) compare the relative effectiveness of alternative therapies in a wide variety of clinical and physiologic conditions; and (4) to develop criteria for titration of therapy to the endpoints of the supranormal optimal goals using cardiac index (CI), oxygen delivery (DO2), and oxygen consumption (VO2) as proxy outcome measures. Second, a general purpose algorithm was generated from these data and tested in preoperatively randomized clinical trials of high-risk surgical patients. Improved outcome was demonstrated with this generalized algorithm. The concept that the supranormal values represent compensations that have survival value has been corroborated by several other groups. We now propose a unique approach to refine the generalized algorithm to develop customized algorithms and individualized decision analysis for each patient's unique problems. The present article describes a preliminary evaluation of the feasibility of artificial intelligence techniques to accomplish individualized algorithms that may further improve patient care and outcome.

Algorithms

Estimation of drug binding parameters.

Many methods have been suggested and tested to estimate the association constants and binding capabilities of ligand-macromolecule interactions from experimental data. This problem is a subset of the general problem of parameter estimation for nonlinear algebraic models where both the independent and dependent variables are subject to measurement error. It is often difficult to anticipate the effect on the parameter estimates that is caused by error in the primary measurements. In this work, a computer algorithm is described which finds the maximum likelihood estimate for the true values of the parameters and also estimates for the values of the measurements. It is applied to experimental binding data in two examples for fitting the association constants and binding capacities.

Dicumarol

Investigation of an FFT-based correlation technique for verification of radiation treatment setup.

Electronic portal imaging devices that capture an image of a patient's treatment field electronically by means of a computer data acquisition system operating in real time are becoming available. This paper reports on a study of a field verification correlation algorithm that can compare each treatment portal image to an image of the correct treatment field positioning. The algorithm requires no human intervention or analysis of the images but rather uses fast Fourier transforms to produce a correlation distribution. The position and amplitude of the correlation distribution maximum were tested as objective measures of translational and rotational differences of subject positions between pairs of images. The concept was tested by using a prototype algorithm to obtain the correlation distributions for images of an Alderson Rando head phantom. Images of the phantom setup with various errors were compared with an image of the phantom in the initial, correct treatment position. Translations, in-plane and out-of-plane rotations, and combinations of translations and rotations were studied. The algorithm accurately measured translations. The value of the correlation distribution maximum was found to be a reasonable candidate for an alignment parameter for which tolerable error thresholds might be established.

Algorithms

Accuracy and reproducibility of clinically acquired two-dimensional echocardiographic mass measurements.

Left ventricular mass (LVM) measurements made by the truncated ellipsoid algorithm from clinical two-dimensional echocardiograms (2DE) were compared to autopsy weights in 37 patients. All six 2DE instruments were calibrated with an ultrasound phantom to standardize LVM measurements. Measurements were made by an experienced echocardiographer (LVME) and by an echocardiographer (LVMN) newly trained in LVM measurement from clinical 2DE tapes of patients with LV weights later confirmed at autopsy. LVME (r = 0.91, SEE +/- 41 gm) were more accurate than LVMN for all 2DE, but LVMN equalled LVME in accuracy for technically good 2DE. Interobserver variability was 36 gm, or 17% of LVM for all 2DE, and fell to 27 gm, or 12% of LVM for technically good 2DE. Segmental wall motion abnormalities and time from 2DE to death did not influence measurement accuracy significantly. LVM measurements by the 2DE truncated ellipsoid formula are accurate and reproducible in patients with normal and abnormal hearts.

Adult

Physics of gamma knife approach on convergent beams in stereotactic radiosurgery.

The Presbyterian-University Hospital of Pittsburgh installed the first clinically designated Leksell gamma knife in the U.S. in August 1987. Gamma knife radiosurgery involves stereotactic target localization with the Leksell frame and subsequent closed-skull single-treatment session irradiation of a lesion with multiple highly focused gamma ray beams produced from 60Co sources. The hemispherical array of sources, the large number of small-diameter beams, and the steep dose gradients surrounding a targeted lesion make physical characterization of the radiation field complex. This paper describes the physical features and the operation of the gamma knife as well as the calibration procedures of the very small, well-collimated beams. The results of studies using in-phantom ion chamber, diode, film, and lithium fluoride thermoluminescent dosimetry were all in close agreement. Both single-beam and multiple-beam dose profiles were measured and reported for the interchangeable helmets, which have 4-, 8-, 14-, and 18-mm-diameter collimators. We also describe the dose calculation and treatment planning algorithm in the treatment planning system. Measurements of the accuracy of mechanical and radiation alignment are also performed and discussed.

Brain Diseases

PaNDA: Efficient Optimization of Phylogenetic Diversity in Networks.

Phylogenetic diversity (PD) plays an important role in biodiversity, conservation, and evolutionary studies by measuring the diversity of a set of taxa based on their phylogenetic relationships. In phylogenetic trees, a subset of k taxa with maximum PD can be found by a simple and efficient greedy algorithm. However, this algorithmic tractability is lost when considering phylogenetic networks, which incorporate reticulate evolutionary events such as hybridization and horizontal gene transfer. To address this challenge, we introduce PaNDA (Phylogenetic Network Diversity Algorithms), the first software package and interactive graphical user-interface for exploring, visualizing, and maximizing diversity in phylogenetic networks. PaNDA includes a novel algorithm to find a subset of k taxa with maximum diversity, running in polynomial time for networks of bounded scanwidth, a measure of tree-likeness of a network that grows slower than the well-known level measure. This algorithm considers the variant of PD on networks in which the branch lengths of all paths from the root to the selected taxa contribute towards their diversity. We demonstrate the scalability of this algorithm on simulated networks, successfully analyzing level-15 networks with up to 200 taxa in seconds. We also provide a proof-of-concept analysis using a phylogenetic network on Xiphophorus species, illustrating how the tool can support diversity studies based on real genomic data. The software is easily installable and freely available at https://github.com/nholtgrefe/panda. Additionally, we extend the definition of PD to semi-directed phylogenetic networks, which are mixed graphs increasingly used in phylogenetic analysis to model uncertainty of the root location. We prove that finding a subset of k taxa with maximum diversity remains NP-hard on semi-directed networks, but do present a polynomial-time algorithm for networks with bounded level.

network

Critically ill patients have high basal growth hormone levels with attenuated oscillatory activity associated with low levels of insulin-like growth factor-I.

OBJECTIVE: The aim was to study the relationship between growth hormone (GH) and insulin-like growth factor-I (IGF-I) in critically ill patients. DESIGN: Case-control study of critically ill patients admitted to the intensive care unit was carried out. PATIENTS: Six critically ill patients (51-78 years) who required ventilation and parenteral nutrition and six age, weight, height, and sex-matched healthy adults were studied. MEASUREMENTS: The patients and controls were studied for two 24-hour periods; the patients before and after starting parenteral feeding, and the controls during a 36-hour fast and when taking meals equivalent in calories and protein to the patients' parenteral feed. Serum GH was measured at 20-minute intervals and analysed by a pulse detection algorithm (Pulsar) and Fourier transformation. IGF-I was measured at 0, 12, and 24 hours. RESULTS: Patients had low serum IGF-I levels compared with controls, whether fasted or fed, despite having mean GH levels similar to fasted controls. For fasted patients vs fasted controls the mean (+/- 1 SD) GH levels were 4.5 +/- 2.0 vs 4.0 +/- 2.4 mU/l respectively, and IGF-I levels at the end of the fast were 0.17 +/- 0.11 vs 0.78 +/- 0.29 U/ml (P = 0.003). Patients showed elevated baseline GH levels compared with controls when fasted and during parenteral feeding (patients vs controls fasted 3.1 +/- 1.9 vs 0.8 +/- 0.5 mU/l, P = 0.01; patients vs controls fed 4.2 +/- 4.5 vs 0.5 +/- 0.04 mU/l, P = 0.028). Fourier transformation confirmed oscillatory GH levels in the controls, fasted or fed, but this activity was attenuated in the patients. Parenteral feeding had no effect on the GH profiles or IGF-I levels of patients, but controls showed greater mean GH levels during their fast than when fed. CONCLUSIONS: We have demonstrated that critically ill patients have low IGF-I levels associated with augmented baseline GH levels which show reduced oscillatory activity. The results would be compatible with the hypothesis that there is an adaptive change in critically ill patients away from the indirect effects of GH (stimulation of IGF-I production and anabolism) and toward the direct effects (lipolysis and insulin antagonism) which increase the availability of energy substrates. The pattern of GH levels seen in our patients may be important in this adaptation.

Abdomen

Segmentation of coronary arteriograms by iterative ternary classification.

A segmentation algorithm for extracting arterial structures in coronary angiograms is presented. The algorithm mimics the process of interactive interpretation in human vision by iteratively implementing a ternary classification and learning process. Two gray-scale thresholds are computed to define three pixel classes: artery, background, and undecided. Then, two new thresholds for undecided pixels are computed using statistics conditioned upon the current classification. The threshold adaptation is governed by a learning algorithm based on the line and consistency measurements around each pixel. The process converges and results in a binary image. The performance of this algorithm on human coronary arteriograms was compared qualitatively to that of a relaxation algorithm and of a scattering based algorithm. Quantitative comparison was also made possible with computer generated images, which were obtained with the help of a model of the imaging chain and a process of interactive visualization of the modeled data. The iterative ternary classifier showed the best performance over a broad range of image quality. The study also demonstrated the use of visualization and user interaction in model building and algorithm development.

Algorithms

Variation in the lung inhomogeneity correction factor with beam energy. Clinical implications.

In order to determine the magnitude of the dosimetry error introduced by failing to correct for increased transmission through lung tissue in treating thoracic malignancies, measurements in a phantom were taken using different field sizes, inhomogeneity thicknesses and photon qualities. The results indicate that the error introduced by neglecting the inhomogeneity correction is greatest at lower photon energies, smaller field sizes and greater thickness of inhomogeneity. Correction factors to account for the lung inhomogeneity were obtained from phantom measurements and were compared with those calculated using the tissue-air ratio and Batho-Young algorithms; correlation coefficients describing the relationship between measured and calculated values exceeded 0.995. The calculated values tended to overestimate the correction factor and differed most from the measured correction factors at lower energies, smaller field sizes, and greater inhomogeneity thicknesses. The importance of these results in clinical radiation therapy is discussed.

Cobalt Radioisotopes

Methods for defining equity-stratifying variables: a systematic review of validation studies.

BACKGROUND AND OBJECTIVE: Disease burden is often disproportionally higher among those who are socially disadvantaged by factors defined in the PROGRESS-Plus framework (ie, Place of residence, Race/ethnicity/culture/language, Occupation, Gender/sex, Religion, Education, Socioeconomic status, and Social capital, with "Plus" covering features like age and disability). The accuracy and applicability of case definitions to identify these variables from administrative and clinical health data are unknown. We conducted a systematic review to explore how equity-stratifying variables, as categorized by the PROGRESS-Plus framework, have been defined and validated in epidemiologic studies using administrative health, population-level, or electronic health record (EHR) data. METHODS: Medline, EMBASE, CINAHL, Web of Science, and Google Scholar were searched from the inception of the databases to 2024 for validation studies of equity-stratifying variables in adults using administrative health datasets, health registries, or EHR data. Titles and abstracts, followed by relevant full-text articles, were screened in duplicate by two reviewers for eligibility. The data sources utilized, algorithms employed, and their associated performance measures were extracted and synthesized from included studies. Given substantial heterogeneity in study design, equity-stratifying variable definition, and performance metrics, meta-analysis was not possible. RESULTS: Of the 9099 unique citations screened, 188 full texts were reviewed and 116 were included in this review. Most studies were published between 2019 and 2024 (n = 64, 55%) and were validation studies of race/ethnicity definitions that used race/ethnicity codes or surname list algorithms (n = 66, 57%). No studies examined religion. Regarding the reported performance measure estimates, the race/ethnicity/culture/language equity-stratifying variables category had the largest variability across sensitivity, positive predictive value (PPV), and Cohen's Kappa. Occupation validation studies had the lowest variation in sensitivity and PPV. CONCLUSION: Despite an increasing number of publications reporting on the validation of equity-stratifying variables relevant to the PROGRESS-Plus framework, performance measures varied widely across studies. The significant heterogeneity in equity-stratifying variable definitions and methods used to validate them support the need for further rigorous validation of equity-stratifying variables in administrative and clinical health data. PLAIN LANGUAGE SUMMARY: Disease burden is often higher in people who experience financial hardships, lower level of education, discrimination due to race/ethnicity, and unstable housing. These social factors can be considered health equity factors and are important for understanding health inequalities. Health researchers often use large datasets, such as hospital or electronic health records (EHRs), to study these health equity factors. However, it is not clear how accurately these data sources capture information about people's social circumstances and how these factors are defined. In this study, we reviewed existing research to understand how health equity factors have been defined across health data sources and how accurate they are at measuring aspects of health equity and social disadvantage. Of the more than 9000 studies we identified, we included 116 that met our criteria for this systematic review. Most included studies focused on identifying race and ethnicity, often using codes or surname-based methods. We found that the accuracy of these methods varied widely across studies, meaning results may not always be reliable or comparable. Overall, our findings show that there are inconsistencies in how social factors are defined and measured in health data. This makes it difficult to fully understand and address health inequalities using routinely collected health data. More work is needed to develop and validate better quality and more consistent methods for capturing these important social factors.

Humans

Sex determination from chest plate roentgenograms.

Precise sexing--97% to 99% accuracy--of adult chest plates is possible when highly predictive costal cartilage ossification patterns are combined with four simple metric determinations. More than 1100 chest plate roentgenograms were evaluated for ossification pattern, fourth rib width, corpus width, sternal length and sternal area in an adult decedent population. An elementary, empirically obtained algorithm using the patternings and measurements, along with simple derivations (sternal length and area indices) was developed and then applied in chest plate sexing. This technique is not only easy, rapid and inexpensive, but it also results in a permanent and easily stored record.

Adult

Advantages and limitations of the spatially adaptive program SAPRO in clinical perimetry.

The SAPRO program devised for the OCTOPUS 201 automated perimeter, consists of a number of program components. It is designed to be used on the Octopus 201 computer. In its measurement mode, it employs an algorithm which achieves high speed and efficiency. This is made possible by a threshold bracketing strategy which is simpler than the normal OCTOPUS bracketing. Moreover, three grids with test location distributions of increasing resolution are superimposed in succession on the whole or on part of the visual field to be analyzed. Out of the distribution of test locations, only those which fulfill a number of criteria are actually utilized. These criteria must be given and are adaptable to any given clinical problem. As a result, despite the high spatial resolution achieved, only a fraction of the test locations are utilized using SAPRO as compared with a program using a fixed pattern of test locations. The algorithm is thus able to imitate human intelligence, which tends to concentrate stimuli at places which appear to be relevant for the solution of a problem. The results of program SAPRO are disturbed by short- and long-term fluctuations. Their validity is limited, in a manner similar to that encountered in any other threshold determination procedure. A number of printout modes is available which are oriented towards an optimal understanding of the information contained in various examinations. These principles will be illustrated by one case of inactive disseminated chorioretinitis.

Computers

Calculation of pulse-wave velocity using cross correlation--effects of reflexes in the arterial tree.

The need to investigate the elastic properties of arterial vessels in situ for the early recognition of degenerative disorders in arteries has long been apparent. Pulse-wave diagnostics has been used in traditional medicine, but only in a qualitative way. By measuring the vessel diameter change, simultaneously at two levels along an artery, it should be possible to calculate the pulse-wave velocity (PWV). A newly developed ultrasonic instrument, DIAMOVE, was designed to provide a two-dimensional, real time, B-mode image for display of the exact position of two measurement sites; a computer-controlled digital phased-locked loop detector for the measurement of diameter changes; and a personal computer for the display of the momentary displacement of the artery walls. The cross-correlation technique was used on the information from the vessel wall movements to calculate the resulting PWV. Early measurements on healthy patients showed some unexpected artifacts, which were found to be due to reflected waves, affecting the shape of the pulse-wave at the sites of measurement. A modified PWV estimation algorithm, where only the foot of the pulse-wave in every beat is utilized, seems to have solved this problem and now makes the method suitable for clinical use.

Algorithms

Evaluation of lung dose correction methods for photon irradiations of thorax phantoms.

Radiation absorbed dose in lung is measured and calculated using several algorithms available on commercial treatment planning systems. Phantoms resembling the human thorax are used and irradiated with small and large photon beams of 60Co, 4, 6, and 10 MV X ray energies. The applicability and usefulness of the different calculation methods in clinical situations is discussed.

Lung