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At least 217 records · Page 12Linked to original sources
PubMed1985

Identification of pharmacokinetic parameters of two compartment open model with first order absorption.

This paper deals with the estimation of pharmacokinetic parameters of a two-compartment open model with first order absorption from plasma level data. The eigen-values of the characteristic matrix of the given system are obtained by transforming them into a single variable and the global minimum of the deviation (for plasma concentrations) from the observed values is obtained through the solution of linear relations involving the eigen-values. The distribution volume and the lag time are also identified. Finally, the uniqueness of the absorption rate constant is obtained by the minimum energy principle. The model is tested for different sets of data for the drug Guanfacine, an antihypertensive drug. The results are compared to those obtained by the SAMM program.

Absorption↗
PubMed1989

Recursive identification of lung parameters.

Determination of lung capacity (FRC) using insoluble gas washout or equilibrium methods is a common procedure in respiratory tests. The lung model can be extended to include multiple compartments with differing volumes and ventilation fractions. A discrete-time mathematical model of a multi-compartment lung was developed based on mass conservation laws of the gas exchange. To estimate the unknown parameters in the model from experimental data, a recursive prediction error algorithm was implemented. The design of the algorithm provides the capability to track time-varying parameters, such that the system can be monitored on-line. Determination of the model order may be as important as estimation of the parameters, especially in biological systems where little may be known about the structure. Two new criteria to distinguish between models of varying complexity, the 'minimum description length principle' and the 'accumulated prediction error', are illustrated. Theoretical studies show that these criteria yield consistent order estimates of the process. Simulations and experimental data confirm the feasibility of this approach for the estimation of lung parameters.

Algorithms↗
PubMed1996

Affinity immunosensor for milk progesterone: identification of critical parameters.

The effects of several experimental parameters on the performance characteristics of a competitive-type immunochromatographic assay of milk progesterone were studied. Increasing the size of the colloidal gold particles used as a label increased both maximal signal obtained and sensitivity of the assay measured as slope of the progesterone standard curve. The concentration of the antibody used to prepare the detection zone was found to be critical factor, in that low concentrations of antibody resulted in a poor sensitivity. The compatibilities of various buffer systems with the assay were studied. The assay worked well with buffers having a broad pH range of 4.5-8.5.

Animals↗
PubMed1993

The identification of informative parameters in the flow cytometric analysis of breast carcinoma.

DNA ploidy and the measurement of proliferation or S-phase fraction are both of prognostic significance in breast cancer, yet clinical use is minimal in the U.K. Immunohistochemistry is, however, used to aid diagnosis, so a panel of antibodies were analysed by flow cytometry to assess their predictive value for prognosis, tumour stage and grade. Of 10 parameters tested on 202 breast tumour samples, tumour cell proliferation and DNA ploidy were the two most informative; cytokeratin staining, natural killer and B-cell infiltration also proved to be of value but there was no prognostic value in measuring tumour infiltrating monocytes, helper/suppressor T-cell ratios, tumour cell reactivity with carcinoembryonic antigen or human milk fat globulin antibodies. For each of the informative parameters, scores numerically weighted towards a poorer prognosis were derived which when combined, correlated with tumour grade, stage and prognosis. Such data interpretation is objective, and can be transposed to other human tumours.

Adolescent↗
PubMed1999

Clinical Value of Neuroimaging in the Diagnosis of Dementia. Sensitivity and Specificity of Regional Cerebral Metabolic and Other Parameters for Early Identification of Alzheimer's Disease.

Dementing illnesses such as Alzheimer's disease (AD) progressively devastate human brain tissue and consequently the health and lives of people afflicted by these disorders. One of the greatest clinical challenges posed by dementia is establishing an approach to ensure its early identification and accurate diagnosis-thus making it possible to treat and, potentially, arrest the development of disease before a substantial amount of brain tissue has been permanently destroyed. The data generated by neuroimaging studies conducted over the past two decades show PET with [(18)F]fluorodeoxyglucose (FDG) to be exceptionally well-suited to meeting this challenge. The regional metabolic patterns imaged with FDG-PET enable sensitive diagnosis of AD, and reveal pathophysiologic alterations even before they lead to symptomatic expression. The accuracy of PET in identifying early AD, and distinguishing it from other etiologies of cognitive impairment, exceeds that of CT, MRI (qualitative or quantitative), and SPECT, as well as that of expert clinical evaluation based on history, physical examination, cognitive testing, and blood laboratory values. Recent developments in instrumentation and radiopharmaceutical distribution have made obtaining scans of cerebral metabolism achievable in routine clinical settings, including most hospitals in which Nuclear Medicine services are provided, for less than the cost of a single year of anticholinesterase therapy or a single month of lost productivity. The need and opportunity are thus present for making a fundamental change in the current approach to evaluating patients for dementia.

Journal Article↗
PubMed2000

Analytic method based on identification of ellipse parameters for scanner calibration in cone-beam tomography.

This paper is about calibration of cone-beam (CB) scanners for both x-ray computed tomography and single-photon emission computed tomography. Scanner calibration refers here to the estimation of a set of parameters which fully describe the geometry of data acquisition. Such parameters are needed for the tomographic reconstruction step. The discussion is limited to the usual case where the cone vertex and planar detector move along a circular path relative to the object. It is also assumed that the detector does not have spatial distortions. We propose a new method which requires a small set of measurements of a simple calibration object consisting of two spherical objects, that can be considered as 'point' objects. This object traces two ellipses on the detector and from the parametric description of these ellipses, the calibration geometry can be determined analytically using explicit formulae. The method is robust and easy to implement. However, it is not fully general as it is assumed that the detector is parallel to the rotation axis of the scanner. Implementation details are given for an experimental x-ray CB scanner.

Calibration↗
PubMed1995

Identification of hormonal parameters for successful systemic single-dose methotrexate therapy in ectopic pregnancy.

Single-dose methotrexate is an alternative to surgery in treating ectopic pregnancy. Because success rates vary, we sought to identify factors which predict treatment outcome. A total of 44 women with ectopic gestation were treated. The non-laparoscopic diagnosis of ectopic pregnancy was made following history, physical examination, ultrasound, endometrial biopsy and the measurement of serial beta-human chorionic gonadotrophin (HCG) and progesterone concentrations. Methotrexate (50 mg/m2 i.m.) was administered, with a second dose given 1 week later in patients with plateauing or rising beta-HCG concentrations. Of 44 patients, 23 (52.3%) were successfully treated with one dose. An additional 10 women (22.7%) were also successfully managed but required a second dose, giving an overall success rate of 75.0%. In all, 11 women (25.0%) required surgery, four of whom experienced tubal rupture. Receiver operator curves were constructed to optimally select pretreatment beta-HCG and progesterone cut-off concentrations for successful treatment. Using beta-HCG < 1500 IU/l or progesterone < 7.0 ng/ml (22.3 nmol/l) as a cut-off concentration produced a diagnostic test with a sensitivity of 87.5%, a specificity of 90.0%, a positive predictive value of 96.6% and a negative predictive value of 69.2%. Conversely, this model predicts that patients with serum beta-HCG concentrations > or = 1500 IU/l and progesterone concentrations > or = 7.0 ng/ml are at far greater risk of failing single-dose methotrexate therapy.

Adult↗
PubMed2006

Parallel analysis of transcript levels and physiological key parameters allows the identification of stress phase gene markers in Chlamydomonas reinhardtii under copper excess.

Excessive copper concentrations, known to induce reactive oxygen species (ROS) formation, have been tested with respect to their effects on transcript abundance and related proteins involved in oxidative stress responses. The results show that the stromal photosynthetic functions were more ROS sensitive than the membrane-located reactions. The rbcL over-expression compensated for the damage only at 10 microM Cu, whereas the genetic stimulation of alpha-tocopherol biosynthesis led to the protection of membrane reactions up to 50-100 microM Cu. For this reason, the gradual growth drop of Chlamydomonas reinhardtii cultures observed under increasing Cu(2+) concentrations matched better with the loss of photosynthetic capacity than with those of photosynthetic quantum yields. According to Larcher's stress concept, the results allow the identification of gene markers for the alarm (rbcL), the hardening (FeSOD, VTE3) and the exhaustion [cyclin-dependent protein kinase (cdk), psbA] phases. These genes can be used to rapidly evaluate the state of oxidative stress in algae and putatively in other plant cells.

Animals↗
PubMed2004

Quantitative analysis of retinopathy in type 2 diabetes: identification of prognostic parameters for developing visual loss secondary to diabetic maculopathy.

PURPOSE: To describe whether quantitative assessment of early changes in the morphology of retinopathy lesions can predict development of vision-threatening diabetic maculopathy. METHODS: We used a nested case-control study, and we studied 11 type 2 diabetes patients who had developed visual loss secondary to diabetic maculopathy. For each diabetes patient, we also studied three matched control patients who had been followed for a comparable period of time without developing visual loss. Fundus photographs describing the early development of retinopathy were digitized and subjected to a full manual quantitative grading on a computer monitor. Differences in the early development of retinal morphology were compared between the two groups. The outcome parameters were changes in the number and area of haemorrhages and exudates in different regions of the fundus, and the weighted distance of these lesions from the fovea and the optic disc. RESULTS: In patients who developed visual loss secondary to diabetic maculopathy there was significant early progression in the total area and number of haemorrhages and exudates. The haemorrhages had progressed in all retinal areas except the area around the optic disc and the temporal vascular arcades. The exudates had progressed temporally from the fovea and in the retinal periphery. CONCLUSIONS: The results suggest that a quantitative description of the regional development of early diabetic retinopathy may help in identifying patients who will later develop vision-threatening maculopathy.

Adult↗
PubMed2000

The use of anthropometric and clinical parameters for early identification and categorisation of nutritional risk in pre-school children in Benin City, Nigeria.

This study was conducted in Benin City, Nigeria between June and August 1996 to assess nutritional status and health risks of three to five-year-old children, with the view to suggesting practical approaches to their early detection and intervention. A total of 165 children comprising 90 males and 75 females was studied. Mid-upper arm circumference (MUAC), weight-for-age (WFA), weight-for-height (WFH) and height-for-age (HFA) z-scores were determined and used to calculate percentage prevalence of malnutrition. Clinical features of macro- and micro-nutrient deficiency were used to develop a clinical scoring system which was subsequently matched with anthropometric z-scores. The results showed that MUAC z-scores (-1.91 SD +/- 0.74) gave the highest percentage prevalence of malnutrition of 45.2% in this population, followed by the WFA (-1.22 SD +/- 1.07) and HFA (-0.84 SD +/- 1.42) z-scores with a percentage prevalence of 23.3% and 20.6% respectively. The WFH z-score (-0.89 SD +/- 1.06) was the least sensitive in detecting malnutrition (14.7% prevalence). The percentage prevalence calculated from MUAC z-scores matched FAO figures (43%) for the sub-Saharan African region in 1996. MUAC z-scores also correlated more closely with the clinical features of malnutrition (R2 = 0.7087). Progressively worsening clinical features were also seen with decreasing z-scores for all variables. Even though moderate differences in clinical and anthropometric variables were detected between the sexes with females fairing better than male subjects, these differences were not statistically significant. Comparisons between anthropometric variables showed only weak correlation, except for WFA vs. HFA z-scores (R2 = 0.5233) and WFH vs. WFA z-scores (R2 = 0.4559) which showed moderately positive correlation. We conclude that whereas MUAC z-scores were most sensitive in detecting the extent of malnutrition in this population, merely using anthropometric variables alone may lead to significant under-reporting of the prevalence of malnutrition in a community. A combination of various anthropometric z-scores with clinical features will however help in the early identification and categorisation of subjects in terms of degree of nutritional risk. The training of field health and nutrition workers should therefore emphasise the routine use and combination of anthropometric and clinical variables in the determination of prevalence of malnutrition and in the formulation of intervention strategies for nutrition rehabilitation.

Analysis of Variance↗
PubMed2003

Identification of milling parameters for manual cutting of bicortical bone structures.

Within the framework of the development of a new neurosurgical robot system, parameters of conventional manual neurosurgical bone milling had to be determined. These results were used as a reference for the design and validation of the robotic versus manual milling task. Bovine scapulae were used for the tests because their bicortical structure is similar to the bone structure of the skull. The exercise was to cut defined geometries that had been registered on the bone prior to the start of the milling operation. The geometries had to be milled with a depth of 3 mm, which corresponded to the radius of the ball of the cutter. Different parameters like tool position, rotary speed, temperature, forces and time were registered. Eleven experienced neurosurgeons with practical experience of 80-1200 skull operations participated in this study. First results show a large variation in depth along the line. The lateral deviation was up to 5 mm, the depth error up to 2.5 mm, the tool temperature was 22 degrees C to 65 degrees C, and rotary speed varied from 15,000 to 80,000 rpm. Registered forces had maxima of 16 N in the feed direction and 21 N normal to the surface; average forces were approximately 1-2 N.

Animals↗
PubMed2004

Non-endoscopic parameters for the identification of esophageal varices in patients with chronic hepatitis.

OBJECTIVE: To develop non-invasive laboratory variables for the identification of esophageal varices in patients with cirrhosis at Digestive Disease Center, Shifa International Hospital, Islamabad. PATIENTS AND METHODS: All patients with chronic viral hepatitis who presented to the Gastroenterology Division between July 2002 to July 2003 were enrolled in the study. All patients with a diagnosis of Chronic Hepatitis who had platelet counts of 140,000, I.N.R of greater than 1.5 and portal vein (PV) diameter of 13 mm or greater were included in the study. All patients underwent endoscopy to see the presence of varices which were graded following the standard criteria RESULTS: Of 140 patients, 100 (71%) were males and 40 (29%) females. Esophageal varices were present in 70% of the patients while 30% had no varices. CONCLUSION: It was seen that using the standard criteria of a PV diameter 13 mm, I.N.R 1.5 and platelet counts 100,000 for the diagnosis of portal hypertension about 70% patients had endoscopic evidence of esophageal varices. As prophylactic beta blockers are recommended to reduce the chances of a bleed from esophageal varices therefore it is suggested that endoscopy should be done only in patients who fulfill the standard criteria of portal hypertension and those found to have varices should be put on beta blockers.

Adult↗