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PubMed2004

Neuronal and glial cell populations in the piriform cortex distinguished by using an approximation of q-space imaging after status epilepticus.

BACKGROUND AND PURPOSE: Temporal lobe epilepsy produces an injury cascade that includes neuronal loss and gliosis. The pilocarpine model reliably reproduces the symptoms of temporal lobe epilepsy and the resulting neuronal glial changes can be accurately depicted on diffusion-weighted images. The judicious choice of diffusion-encoding gradients can isolate multiple apparently isochromatic diffusing populations, but the assignment of these populations to specific tissue characteristics has been difficult. We sought to distinguish neuronal tissue from glial cell-infiltrated tissue by using signatures from unique spin populations obtained from an approximation of q-space imaging. METHODS: Ten male Sprague-Dawley rats received pilocarpine injections to induce seizures. All animals underwent diffusion-weighted imaging at 12 hours, 24 hours, and 7 days. At least two animals were selected for histologic analysis at each imaging time point. RESULTS: The results indicated that seizure-induced neurologic dysfunction may have been reflected in the emergence of new spin populations. In the piriform cortex-amygdala region of interest, the mean free diffusion path increased from 12 to 20 microm within 12 hours of seizure onset and persisted for at least 7 days. These results were temporally correlated with histologic evidence of necrotic changes. CONCLUSION: Our results suggest that even incomplete sampling of q space can provide useful physiologic information.

Amygdala↗
PubMed2004

Böhler's and Gissane's angles of the calcaneus in the Saudi population.

OBJECTIVE: The purpose of this study is to measure Böhler s angle (BA) and Gissane s angle (GA) in the Saudi population and compare their values to the published data. METHODS: Lateral plain radiographs of 229 normal feet and ankles of 158 females and 71 males, with age range of 15-72 years, were studied retrospectively at King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia between 2002 and 2003. Böhler's angle and GA were measured and the mean and standard deviation of each angle were calculated. The relationship between each angle and age, gender, and side of body was tested, and compared to international figures. RESULTS: The mean BA in the Saudi population was 31.21 degree with a range of 16-47 degree. The mean GA was 116.16 degree with a range of 96-152 degrees. Böhler's angle and GA are not significantly related to age, gender, or side of body. Moreover, the range of both angles was wider than that reported in the literature. CONCLUSION: The study shows the difference between the Saudi and various other populations in regard to BA and GA, and reinforces the need to establish the normal ranges of BA and GA in a given population.

Adolescent↗
PubMed2006

Creutzfeldt-jakob disease involvement of rolandic cortex: a quantitative apparent diffusion coefficient evaluation.

BACKGROUND: Previous reports have suggested that abnormally reduced water diffusivity and T2 prolongation involving cerebral gray matter in patients with early sporadic Creutzfeldt-Jakob disease (sCJD) involves all areas of neocortex with similar frequency, except for primary sensorimotor cortex (Rolandic cortex) and visual cortex. Rolandic cortex often appears to be spared even in the presence of extensive surrounding neocortical signal intensity abnormality in adjacent frontal and parietal gray matter. A quantitative apparent diffusion coefficient (ADC) analysis was designed to investigate whether this unusual pattern results from pathophysiologic sparing of Rolandic cortex or from reduced conspicuity of signal intensity abnormality on MR imaging echo-planar diffusion-weighted images (epiDWI) related to unknown underlying features of Rolandic cortex. METHODS: ADC maps were derived from epiDWI of 6 patients with sCJD and 8 control patients. Bilateral regions of interest were manually selected in precentral gyri, superior frontal gyri, postcentral gyri, supramarginal gyri, thalamus, putamen, and caudate nuclei. ADC and relative ADC (rADC) values were calculated for each region of interest. RESULTS: Patients with CJD had significantly lower ADC values than control patients in all areas (P < or = 0.05). The trend toward decreased ADC values in the deep nuclei correlates well with previously published reports. rADC were not significantly different between CJD and control groups in any area (P > 0.25 in all cases). CONCLUSION: Quantitative ADC measurements in patients with early sCJD demonstrate a similar degree of reduced water diffusivity in the primary somatosensory cortex as in other neocortical areas, despite the normal appearance of these areas on visual inspection of epiDWI.

Aged↗
PubMed2006

Higher prevalence of cortical lesions observed in patients with acute stroke using high-resolution diffusion-weighted imaging.

Ischemic lesion conspicuity on routine diffusion-weighted imaging (DWI, 30 seconds) was compared with an improved sequence (high-resolution DWI [DWI-HR], 256 seconds) having increased spatial resolution and signal to noise and decreased eddy current artifact in 42 patients with acute ischemic stroke. Total lesion volumes were similar; however, twice as many lesions were identified on DWI-HR, predominately in cortical gray matter. Modest improvements to imaging resulted in increased conspicuity, potentially affecting diagnosis, suspected pathogenic mechanism, and therapeutic decision.

Adult↗
PubMed1991

The quantification of planar scintigraphy using three dimensional modelling of organ shadows.

A method to define biodistribution from planar scintigraphic data is presented. Sampling regions or regions of interest (ROI's) are first defined as the projection contour of organs. From anatomical knowledge the three dimensional volume of the organ whose shadow has been traced is reconstructed. When the relevant organ volumes including the whole body or relevant whole body part have been defined, the count rate density in each pixel is assumed to represent the sum of the product of the projecting organ partial volumes times the tracer concentrations in the underlying organs. The solution (the definition of organ concentrations) is found by a matrix inversion. Validation is obtained in two ways. The first method is illustrative: an image is reconstructed from the defined volumes modulated by the computed concentrations. This image, if the method is correct, should be a crisp equivalent of the original data and closely similar to it following blurring with a convolution kernel equal to the imaging system's point spread function. The second is analytical: from reconstructed S.P.E.C.T. data in which voxel values are directly proportional to organ concentrations, a planar image is reconstructed. Organ average voxel values are computed in the S.P.E.C.T. image with volumetric ROI's and in the reprojected planar image using the method described here. The methods should yield the same concentration data but for a scaling factor. The method has the advantage that it yields volumetric and concentration data which are directly applicable to MIRD type analysis. In effect, the standard man assumptions in MIRD analysis have been incorporated in the calculation of the concentrations.

Humans↗
PubMed1990

Classification methods for computerized interpretation of the electrocardiogram.

Two methods for diagnostic classification of the electrocardiogram are described: a heuristic one and a statistical one. In the heuristic approach, the cardiologist provides the knowledge to construct a classifier, usually a decision tree. In the statistical approach, probability densities of diagnostic features are estimated from a learning set of ECGs and multivariate techniques are used to attain diagnostic classification. The relative merits of both approaches with respect to criteria selection, comprehensibility, flexibility, combined diseases, and performance are described. Optimization of heuristic classifiers is discussed. It is concluded that heuristic classifiers are more comprehensible than statistical ones; encounter less difficulties in dealing with combined categories; are flexible in the sense that new categories may readily be added or that existing ones may be refined stepwise. Statistical classifiers, on the other hand, are more easily adapted to another operating environment and require less involvement of cardiologists. Further research is needed to establish differences in performance between both methods. In relation to performance testing the issue is raised whether the ECG should be classified using as much prior information as possible, or whether it should be classified on itself, explicitly discarding information other than age and sex, while only afterwards other information will be used to reach a final diagnosis. Consequences of taking one of both positions are discussed.

Algorithms↗
PubMed1989

Nonlinear curve fitting improves noise sensitivity of the single-breath method for estimation of cardiac output.

In a recent theoretical study, Srinivasan (10) presented a new nonlinear curve fitting algorithm for computing pulmonary blood flow by the single-breath method. The results obtained with the new algorithm showed a considerably lower sensitivity of the estimated pulmonary blood flow to experimental noise than with the linear curve fitting technique reported previously by Grønlund (5). In the present study, we have compared the linear and the nonlinear algorithms using computer simulations and experimental single-breath data. The results showed only a small difference between the two methods. Further, we showed that the difference between the noise sensitivities obtained by Grønlund (5) and Srinivasan (10) can be explained almost entirely by a difference between the models used to simulate experimental noise.

Algorithms↗
PubMed1989

Dynamic wrist motion analysis using six degree of freedom sensors.

Dynamic motion analysis of the wrist in the past has been a tedious and often impossible task to undertake. However, such motion analysis is now practical with the use of the McDonnell Douglas 3Space Digitizer and Macintosh microcomputer. The feasibility of using this system with multiple electromagnetic sensors for upper extremity kinematics analysis has been previously described by our laboratory. This work has now been extended to the dynamic analysis of wrist motion during performance of a work task by placing one sensor on the hand and the other on the distal forearm. The 3Space Digitizer source creates a low-frequency magnetic field. Sensors placed within the field have a specific position and orientation with respect to a coordinate system defined by the source. The x, y, z coordinates and theta, phi, psi orientation angles of the sensors on the subject's extremity are measured during task performance at a rate of approximately 19 readings per second. Analysis of this data provides a "motion signature" of the task under study. After the task completion the data obtained from the digitizer (orientation of the hand and forearm with respect to the digitizer's source) is stored on a computer disk and then reduced using mathematical transformations to obtain instantaneous radial/ulnar deviation (RUD), flexion/extension (FE), and supination/pronation (SP). The transformed data is displayed graphically as RUD vs. time, or FE vs. time and SP vs. time for each given task. A frequency analysis for each task performed is obtained with the use of the Macintosh microcomputer and a Fast Fourier Transform.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1988

Use of spreadsheet software for short-range forecasting of pharmacy management data.

The use of a personal-computer spreadsheet program (Lotus 1-2-3) for forecasting pharmacy management data is described. Exponential smoothing is used in the forecasting model; historical data are used to predict subsequent values. Future performance is assumed to be more closely related to recent performance than to older performance data, so the model gives greater weight to more recent data. The smoothing weight controls the magnitude of error correction; a mean squared error table in the spreadsheet is used to determine the weighting. Two versions of the forecasting model are described. Version A, for a service or product for which data are expected to remain fairly stable, is used to predict values for the next time period. Version B, for data in which a substantial upward or downward trend exists, can be used to predict values for several time periods in the future. Version B differs from version A in that the forecast in version B is an estimate of the overall average of the data (weighted toward the most recent data) plus the estimated change per time period (weighted toward the most recent changes). Data from a university hospital for 1986-87 are used to illustrate the spreadsheet's tabular and graphic output; version A is used to predict the number of outpatient prescriptions for the next month, and data for the hospital's semiannual expenditures on i.v. solutions and sets are used to illustrate version B's forecast. Pharmacy managers can use these spreadsheet forecasts to quantify drug-use and personnel information for presentation to hospital administration.

Computer Simulation↗
PubMed1995

A hybrid neural and statistical classifier system for histopathologic grading of prostatic lesions.

Neural network and statistical classification methods were applied to derive an objective grading for moderately and poorly differentiated lesions of the prostate, based on characteristics of the nuclear placement patterns. A partly trained multilayer neural network was used as a feature extractor. A hybrid classifier system using a quadratic Bayesian classifier applied to these features allowed grade assignment consensus with visual diagnosis in 96% of fields from a training set of 500 fields and in 77% of 130 fields of a test set.

Humans↗
PubMed1994

Modeling the relational complexities of symptoms.

Realization of the value of reliable codified medical data is growing at a rapid rate. Symptom data in particular have been shown to be useful in decision analysis and in the determination of patient outcomes. Electronic medical record systems are emerging, and attempts are underway to define the structure and content of these systems to support the storage of all medical data. The underlying models upon which these systems are being built continue to be strengthened by a deeper understanding of the complex information they are to store. This report analyzes symptoms as they might be recorded in free text notes and presents a high-level conceptual data model representation of this domain.

Computer Graphics↗
PubMed1994

Mixed Bayesian networks: a mixture of Gaussian distributions.

Mixed Bayesian networks are probabilistic models associated with a graphical representation, where the graph is directed and the random variables are discrete or continuous. We propose a comprehensive method for estimating the density functions of continuous variables, using a graph structure and a set of samples. The principle of the method is to learn the shape of densities from a sample of continuous variables. The densities are approximated by a mixture of Gaussian distributions. The estimation algorithm is a stochastic version of the Expectation Maximization algorithm (Stochastic EM algorithm). The inference algorithm corresponding to our model is a variant of junction three method, adapted to our specific case. The approach is illustrated by a simulated example from the domain of pharmacokinetics. Tests show that the true distributions seem sufficiently fitted for practical application.

Algorithms↗
PubMedDate not supplied

Gompertzian growth curves in parathyroid tumours: further evidence for the set-point hypothesis.

BACKGROUND: Clinical and cell kinetic data in parathyroid tumours show that their rate of growth slows down progressively and that tumour size approaches an asymptotic value. The Gompertz equation has been widely used in oncology to model growth retardation in malignant tumours; we describe its first application to a benign tumour. METHODS: In 41 patients with radiation associated hyperparathyroidism, individual solutions were derived for the Gompertz equation: Nt = Exp[A/ a(1 - Exp - at)], where A is the rate constant (years-1) for initial exponential growth and a is the rate constant (years-1) for exponential decline in A. Input data comprised three estimates of tumour age at surgery, 100%, 75% and 50% of the time since irradiation, cell number estimated from tumour weight, and current tumour growth rate, representing the difference between current cell birth rate, estimated from the prevalence of mitotic figures, and an assumed mean rate of cell loss of 5%. RESULTS: With 100% tumour age, geometric mean values were 2.76 for A, 0.134 for a, and 0.87 g for the growth asymptote. As assumed tumour age decreased, the rate constants increased and the growth asymptotes declined from 22% to 9% greater than the geometric mean tumour weight. Depending on assumed tumour age, the rate constants were about 15-45 times smaller than in myeloma and in testicular tumours, and the growth asymptotes about 2500 and about 60 times smaller, respectively. A and a were highly correlated (r2 = 0.993), with a slope of 20.9 and no significant intercept. Depending on assumed tumour age, the geometric mean time from the initial mutation to the first cell division ranged from 39 to 92 days, much longer than in malignant tumours. CONCLUSIONS: (1) The Gompertz modelling demonstrates that both the nonprogressive clinical course and the slow growth of parathyroid tumours can be accounted for by a single mutation. (2) The extremely low values for A and a, and consequent very long delay before the first cell division, support the notion that the initial mutation does not affect a growth regulatory gene, but increases growth indirectly via an increase in secretory set-point, the clone of mutant cells behaving as if they were in a hypocalcaemic environment until the plasma calcium rises to the new set-point. (3) The clinical characteristics of radiation-induced parathyroid tumours are modelled more closely if there is a substantial delay between time of irradiation and onset of tumour growth. (4) The rate constants A and a are highly correlated because the variability of tumour weight on a logarithmic scale is much lower than the variability of the rate constants.

Adenoma↗
PubMed2003

Parametric stability evaluation in computer experiments on the mathematical model of Drosophila control gene subnetwork.

Using the method of generalized threshold models, the problem is formulated and solved to evaluate the parametric stability of the model of a gene subnetwork controlling the early ontogenesis of the fruit fly Drosophila melanogaster. Computer experiments have been performed to test the parametric stability of the model. Quantitative evaluations have been obtained for parametric stability of the Drosophila gene subnetwork in nuclei along the embryo's anterior-posterior axis. The results of computer experiments have been compared with the previous research data on "sensitivity" of functioning regimes to random changes of the parameters in the models of prokaryotic and eukaryotic systems, namely the system controlling the lambda-phage development and the subsystem controlling the flower morphogenesis of Arabidopsis thaliana. The obtained results confirm high parametric stability of gene networks that control the development of organisms.

Animals↗