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At least 1,657 records · Page 92Linked to original sources
PubMed2006

Determining phosphorus release rates to runoff from selected Alberta soils using laboratory rainfall simulation.

Phosphorus losses from agricultural land can cause accelerated eutrophication of surface water bodies. This study evaluated the use of soil test phosphorus (STP) levels to predict dissolved inorganic phosphorus (DIP) concentrations in runoff water from agricultural soils using laboratory rainfall simulation. The objectives of this study were to determine (i) to what extent STP concentrations can be used as a basis to predict P losses from Alberta soils and (ii) how extended rainfall simulation run times affected DIP losses. Soil samples collected from a total of 38 field sites, widely scattered throughout the southern half of Alberta, were subjected to rainfall simulation in the laboratory. The STP concentrations were determined using Miller-Axley, Norwest, Kelowna, Modified Kelowna Mehlich-III, and distilled water extraction methods. Each rainfall simulation event lasted for at least 90 min. Runoff samples were collected in time series for the duration of each simulation, during two distinct runoff intervals: (i) for the first 30 min of continuous runoff (T30) and (ii) for 40 min during runoff equilibrium (Teq). For all the STP extractants and both runoff intervals, the relationship with DIP-flow-weighted mean concentration (FWMC) was linear and highly significant with r2 values ranging from 0.74 to 0.96. However, the slopes of the resulting regression lines were, on average, 1.85 times greater for the T30 runoff interval over those computed for the Teq interval. Thus experimental methodology greatly influenced regression parameters, suggesting that more work was needed to verify these relationships under natural conditions. In addition, with many of the r2 values greater than 0.90 there would be little, if any, benefit derived by including soil properties in regression analysis.

Alberta↗
PubMed1988

Magnetic resonance imaging of the brain and spine. Is clinical efficacy established after the first decade?

STUDY OBJECTIVE: Evaluation of demonstrated clinical efficacy of magnetic resonance (MR) imaging in the central nervous system. DESIGN: Information synthesis of studies before January 1987. SETTING: Reports were classified by the level of clinical efficacy studied (technical capacity, diagnostic impacts, and therapeutic or patient outcome impacts) and were judged by the validity of their methods, especially avoidance of diagnosis review, test review, and work-up biases. MAIN RESULTS: Magnetic resonance imaging probably is superior to computed tomography for detection and characterization of posterior fossa lesions and spinal cord myelopathies, imaging in multiple sclerosis, detecting lesions in patients with refractory partial seizures, and detailed display for guiding complex therapy, as for brain tumors. In other diseases, the efficacy of MR imaging is similar to that of computed tomography (cerebrovascular, radiculopathy, and infection). Magnetic resonance imaging is less invasive than intrathecal or intravenous contrast-enhanced computed tomography and costs 20% to 300% more than computed tomography, although avoidance of hospital stays may offset some costs. Generally, the quality of MR images probably exceeds that of computed tomographic (CT) scans. However, published evidence does not show that the clinical efficacy of MR imaging is generally superior to that of existing imaging modalities such as computed tomography. Only six studies avoided major methodologic biases, and lower true-positive rates for MR imaging were reported in these studies than reported in multiply biased studies. Few studies of the potential of MR imaging for false-positive diagnosis have been done. CONCLUSIONS: Use of standards for quality of evidence leads to more conservative conclusions than those of reports describing the clinical potential of MR imaging. Some applications of MR imaging were confirmed by rigorous studies, whereas others were not well supported by reports free of methodologic biases. If the diagnostic alternative is invasive (for example, myelography and cisternography), MR imaging is preferred, but adequate diagnosis for many conditions (head trauma, simple stroke, and dementia) may not require the detail of an MR imaging study. In general, more rigorous clinical research studies are needed for new technologies such as MR imaging. Because the field of MR imaging is changing, review of its clinical efficacy will need to be revised frequently.

Adult↗
PubMed1997

Organisation, transmission, manipulation of pathological human organs on the WWW.

The paper describes an integrated methodology for the development of a WWW computer system which addresses issues of the organisation, retrieval and manipulation of 3D volumetric models of pathological human organs. The library of organs is distributed on the WWW since medical expertise and needs are typically expensive resources and also because many pathological conditions are often restricted to local diffusion. Users are provided with a WWW viewer for interactive manipulation of the models of the organs. The system supports low-cost MS-Windows 32 platforms and requires no specialised hardware. Early results demonstrate that the compression techniques employed provide near real-time response for retrieval/manipulation, not only over high-speed expensive network lines, but also over low/medium network connections.

Computer Communication Networks↗
PubMedDate not supplied

Liver regeneration after extended right hemihepatectomy in patients with hilar or diffuse bile duct carcinoma.

BACKGROUND/AIMS: The degree to which liver size can be restored and the factors that determine liver regeneration after major hepatectomy are not well understood. METHODOLOGY: Liver volumes (LV) were estimated from computed tomography scans in 16 patients who survived with no evidence of cancer recurrence more than 1 year after extended right hemihepatectomy. RESULTS: The mean percentage of LV at 1 year was 75.7 +/- 9.5% and LV did not change significantly beyond 1 year after surgery. A significant correlation was observed between LV at 1 year and body surface area (r = 0.79, p < 0.001). A significant inverse correlation was observed between LV at 1 year and the plasma retention rate of indocyanine green at 15 min (the ICG 15 value) (r = -0.72, p < 0.01). CONCLUSIONS: In adults, the liver does not always regain its pre-operative size after hepatectomy. Patients' body size and intrinsic liver function or liver blood flow, represented by the ICG 15 value, may be related to regenerated liver size.

Aged↗
PubMedDate not supplied

A systems approach in hepatology.

Systems analysis has been applied to hepatology with the aim of providing a reasonable organisation of domain knowledge and supporting the improvement of clinical performance. To this extent liver structures and functions have been classified and defined, clinical parameters have been carefully selected and suitably associated to describe individual liver functions, and methodological criteria for clinical evaluation have been assessed. Three major outcomes of such an approach, respectively concerning the development of a shareable clinical database, the application of a suitable methodology for clinical reasoning, and the computer-based support to medical decision-making, have been discussed.

Biotransformation↗
PubMedDate not supplied

Magnetic resonance cholangiopancreatography for diagnosing hepatolithiasis.

BACKGROUND/AIMS: Direct cholangiography with endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography sometimes fails to adequately opacify the entire biliary tract, because of severe biliary obstruction caused by ductal stricture or lodged stones. We assessed the diagnostic accuracy of magnetic resonance cholangiopancreatography for hepatolithiasis. METHODOLOGY: Five patients with hepatolithiasis underwent ultrasonography, computed tomography, direct cholangiography, and magnetic resonance cholangiopancreatography, using a half-Fourier acquisition single-shot turbo spin-echo sequence. Surgical exploration or pathologic examination revealed stricture and dilatation of the intrahepatic ducts in all patients. Diagnostic accuracies for stones and ductal abnormalities were compared among the imaging studies. RESULTS: No complications occurred during magnetic resonance cholangiopancreatography studies. Magnetic resonance cholangiopancreatography fully depicted the biliary tract. Magnetic resonance cholangiopancreatography accurately detected and localized intrahepatic stones, as well as bile duct stricture and dilatation, in all patients. Intrahepatic stones were detected by endoscopic retrograde cholangiopancreatography in one of four patients and by percutaneous transhepatic cholangiography in all three who underwent this procedure. Endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography demonstrated ductal stricture in all patients but failed to completely demonstrate the biliary tree in three of four patients, and one of three, respectively. On ultrasonography and computed tomography, precise localization of stones was difficult. Ultrasonography and computed tomography failed to demonstrate ductal stricture in one and two of the five patients, respectively. CONCLUSIONS: Magnetic resonance cholangiopancreatography diagnoses intrahepatic stones and bile duct abnormalities less invasively and more accurately than endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography.

Adult↗
PubMed2002

Mandibular dysmorphology in patients with unilateral cleft lip and cleft palate.

BACKGROUND: Conventional studies of the cleft lip/palate (CLP) dysmorphology have mainly focused on deformities of the lip, nose, and maxilla, while ignoring the mandible. Reasons for that were the lack of well-defined mandibular deformity and restriction from the research methodology. METHODS: This study used 3-dimensional computed tomography (CT) imaging data from 35 patients with unilateral CLP. The 3-dimensional images were rotated into a neutral position. Eight cephalometric landmarks were recorded: the pogonion (PG) and the infradentale (ID) from the frontal view; and the condylion (CO), the tip of coronoid process (CP), and the gonion (GO) from both sides of lateral views. The nasion was used as a reference point for the facial midline. Nine linear distances and four angular measurements were calculated from these landmarks. Each mandible was segmented into two hemi-mandibles for volume measurements. The image manipulation and measurements were performed using a personal computer running Analyze' program. Landmark deviation from the facial midline was computed, and comparisons were made between the cleft and non-cleft sides. RESULTS: The results showed that the precision and accuracy of landmark localization was high with an average error of 0.4%. Deviation from the midline of the ID and PG points, and spatial distances between bilateral CP, CO, and GO points varied without a specific pattern. The average differences were within 2 mm. The volume of the cleft side hemi-mandible was consistently larger than that of the non-cleft side (p < 0.0001). Among linear and angular measurements, CP-GO-PG, CO-ID, CP-ID, and CP-GO showed significant difference between the two sides. CONCLUSION: This study demonstrated that mandibular asymmetry and deformity existed and was measurable in patients with unilateral CLP. The influence of CLP to the mandibular development was expressed by the significant differences of hemi-mandible volume and some of the linear and angular measurements between the cleft and non-cleft sides.

Cleft Lip↗
PubMedDate not supplied

Spleen volume and platelet number changes after living donor liver transplantation in adults.

BACKGROUND/AIMS: The purpose of the present study was to examine the changes of spleen volume and platelet numbers after living donor liver transplantation in adults. METHODOLOGY: The spleen volume was measured by computed tomography preoperatively and 1, 6, and 12 months in 19 patients after liver transplantation. The platelet numbers were followed on the same time schedule. RESULTS: The preoperative average spleen volume was 451+/-276 mL, which decreased gradually after liver transplantation. The preoperative averaged platelet number was 15.4+/-9.0x10(4)/mL, which did not change significantly during the observation period. CONCLUSIONS: The changes in spleen volume in the present study were consistent with the previous data, suggesting that living donor liver transplantation effectively reduced hypersplenism for adult patients.

Adult↗
PubMed2005

Coronary plaque analysis by multimodality fusion.

Imaging of the coronary arteries is usually performed by X-ray contrast angiography or intravascular ultrasound (IVUS). Angiography provides information about the vessel lumen and its geometry. IVUS offers more detailed information that also includes the vascular wall. The chapter describes these two imaging modalities and their geometrically correct fusion yielding a 3-D and/or 4-D representation of the coronary geometry and morphology. The image-derived information is used for assessment of coronary function and plaque severity, blood flow related indices are determined using computational fluid dynamics. Detailed description of the methodology is followed by validation and clinical studies.

Coronary Angiography↗
PubMed1989

Innovations in human genetics education. Alternative methods of instruction in medical genetics.

A course in medical genetics for first-year medical students was developed with the use of alternative methods of instruction, including audiovisual materials and computer-assisted instruction. The use of this methodology enabled students to consider many significant areas of medical genetics, without a dependency on the traditional lecture-based instructional format. Seventy-eight percent of the students identified the alternative instructional methods as an enhancement to their education. These students performed a mean of 6% better on class examinations.

Curriculum↗
PubMed1982

In vivo determination of cellular uptake in the kidney.

This paper describes the application of the pulse injection, multiple indicator dilution method to the study of cellular uptake in the kidney in vivo. By using the uptake of sugars and amino acids as specific examples, a rationale is provided that outlines the use of the technique in distinguishing luminal compared to antiluminal uptake. The site of cellular uptake processes cannot be localized by using a whole-organ approach such as the indicator dilution method; nevertheless, for sugars the correlation between in vivo studies and vesicle uptake measurements carried out with purified brush border and antiluminal membrane fractions confirms that the indicator dilution experiments reflect events that are occurring at the level of the proximal tubule in dog kidney. Because of the heterogeneity of tubular flow and substrate concentration profiles along the length of the nephron, it is difficult to use in vivo methods for carrying out kinetic studies on substrate uptake at the luminal surface. By contrast, a strong argument is made that uptake at the contraluminal surface of the proximal tubule can be optimally studied by using the single-pass indicator dilution method. The particular advantages are that the orientation of the basolateral membrane is known and also that uptake fluxes can be measured over short periods of time, i.e., less than 5 s. As an experimental example, uptake of glutamine in the kidney is discussed, and by a combination of indicator dilution methodology and arteriovenous extraction measurements combined with computer simulation and mathematical modeling, an approach is developed for the purposes of deriving unidirectional substrate fluxes at opposing nephron surfaces.

Animals↗
PubMed1994

Discriminant value of symptoms in patients with dyspepsia.

BACKGROUND: Family physicians encounter many pitfalls in managing and treating dyspeptic patients, most of whom are treated in family practice based solely on their signs and symptoms. METHODS: A computer literature search followed by a systematic methodological appraisal was performed to identify studies that evaluated clinical symptomatology in dyspeptic patients. RESULTS: Ten studies, none of which took place in a family practice, fulfilled our inclusion criteria. The main conclusion drawn from outpatient populations and patients referred for open-access endoscopy was that certain clusters of symptoms have a negative predictive value for organic causes of dyspepsia. Higher age, male sex, pain at night, relief by antacids or food, and previous history of peptic ulcer disease were identified as predictors of organic causes for abdominal symptoms. CONCLUSIONS: These findings can be helpful to family physicians in determining the need for endoscopy referral. However, since the diagnostic values of tests in family practice may differ from those in referred populations, there is a need for prospective studies in primary care.

Dyspepsia↗
PubMed1995

A formal model for quality assurance in coloproctologic surgery.

In the last 30 years the advanced countries experienced a large growth of financial and social resources devoted to Health Care (HC) [1] The need of better co-ordinating activities of a composite large set of specialists, and the need of avoiding further growth of financial and social resources without reducing benefits, stimulated the growth of Health Care Evaluation (HCE) and Quality Assurance (QA) studies. In this paper we show how system analysis and precise assessment of the clinical process can be largely enhanced by using formal techniques. The proposed methodology takes advantage of positive experiences in computer science. It is based on a formal model of the clinical process that provides the physicians with support for assessing diagnostic procedures in a co-operative surgical environment [7]. Diagnostic, grading, and staging procedures are integrated in a single model that can be formally expressed and analyzed. The approach is exemplified by presenting an elementary model of the diagnosis, grading and staging procedures for the colo-rectal cancer and ulcerative colitis.

Colitis, Ulcerative↗
PubMed1996

Fathers of children with disabilities comment on health services.

AIM: A study to investigate the experiences of fathers of children with disabilities generated comments about hospital-based services received around the time of diagnosis. METHODS: Fifteen fathers were interviewed in-depth using an inductive qualitative methodology. Interview transcripts were subjected to computer-assisted analysis in order to identify patterns, themes and categories. RESULTS: Analysis of the data produced a dimension identified and labelled by the authors as negative service evaluation. The components of this dimension were related to poor interpersonal skills by medical staff while breaking bad news, and different expectations of physicians of and fathers over the practical implications of diagnosis. CONCLUSIONS: These results support previous findings and indicate that physicians must take more responsibility for breaking bad news in a way that parents find acceptable.

Adolescent↗
PubMedDate not supplied

[Plasmid size determination using 3 methods].

Analysis of bacterial plasmid profiles has been shown to be very important in epidemiological studies, especially those involving outbreaks of nosocomial infections. The molecular weight size of unknown plasmids is determined by comparing their band pattern obtained in agarose gel electrophoresis with those obtained with plasmids that have been used as molecular weight or size standards. In this study, we determined the size of plasmids present in clinical samples of Enterobacter cloacae comparing their electrophoresis mobility with seven plasmids of known size, using three different mathematical methods. For plasmids with molecular weight ranging from 2 kb to 100 kb. The most accurate determinations were obtained by power-function. Analyses using the exponential variables obtained with these plasmids were accurate for two types of plasmids, those with size ranging from 50 kb to 100 kb and those with size ranging from 2 kb to 30 kb. We also observed discrepancies among the methodologies described, including one used by a computer software designed for calculating the size of plasmids DNA.

Algorithms↗
PubMed1998

[Dendrites, neurons and simulation models].

The dendritic tree, this morphologically remarkably structured and typically diversified portion of the neuron reveals gradually its till recently little known complex functional possibilities. The size of the dendritic membrane participates in the latter similarly as their morphological pattern and their electronic structure which has a marked effect also due to its passive cable properties on the spread and interaction of potential changes on the membrane. Moreover the presence of a complex, differentiated mosaic of ion channels of different types provides dendrites with non-linearities with a wide scope of dynamic phenomena and active properties. The dendritic membrane can e.g. actively reinforce signals proceeding along the thin dendrite fibres and may make the development of action potentials or their retrograde movement from the membrane of the cell body possible. The possible operations above the spatial and temporal structures of signals equipped by differently located excitation and inhibition synapses are enriched by the action of ions entering via ion channels into the cell when the membrane potential changes. Manifestations of neuroplasticity lend these properties further temporal and functional dimensions. The neuron is no longer a one-way polarized and passive transmitter of synaptic input signals four output action potentials; it is a complicated non-linear hierarchic dynamic system with possible complex temporal and spatial analogue signal transformations in dendritic structures. New findings are the result of the cooperative use of empirical and theoretical procedures based on the morphophysiological methods with a high differentiating capacity and the methodology of studies of dynamic systems and computer simulation.

Action Potentials↗
PubMed1997

A methodology for the quantitative assessment of articular cartilage histomorphometry.

OBJECTIVE: Traditionally, histological analysis of cartilage and cartilage repair has been performed qualitatively. While new techniques and grading systems have attempted to improve the quantitative nature of histological assessment, the advent of computer-based analysis systems have enabled development of more quantitative methodologies for cartilage repair. The objective of this study was to develop such a methodology for a more quantitative assessment of cartilage repair using a color-based image analysis system. DESIGN: Repair parameters were defined to describe the degree of cartilage restoration: repair dimensions, degree of attachment, surface roughness and repair location. This technique was experimentally applied to a cartilage repair study using cultured perichondrial cells implanted in a polylactic acid matrix in the rabbit femoral condyle. Specimens were examined and compared with the contralateral normal knee. RESULTS: Results showed increases in cartilage height, repair area, and surface roughness over controls for both 6 and 12 weeks. Surface elevation was significantly decreased at 6 weeks over 12 weeks. The percentage of repair improved between 6 and 12 weeks. Results were compared with a traditional grading system and demonstrated close correlation. Intraobserver and interobserver precision analysis were performed and demonstrated the reproducibility of the quantitative results by and between individuals. CONCLUSIONS: The methodology was deemed successful for a more objective analysis of cartilage with the added advantage of providing measured parameters that can assist in making comparisons between different studies using the same methodology.

Animals↗
PubMed1982

Orbital computed tomography: technical aspects.

Computed tomographic scanning has revolutionized the diagnosis and management of orbital disease. The best use of this methodology requires knowledge of the principles and appropriate attention to scanning protocols. Computed tomographic scanning of the orbit is a demanding technique requiring thin sections through planes precisely positioned from the topographical anatomy. Ideally, orbital CT should include both transverse axial and coronal sections: The pathological condition and its plane of growth will influence the selection of the optimal plane or section. Coronal sections may be obtained either directly or indirectly by computer reconstruction from contiguous transverse images. Sagittal or oblique sections or both also are useful and may be obtained directly or indirectly. Difficulty in patient positioning may preclude direct sagittal imaging, however. The use of intravenous contrast enhancement is not necessary as a routine technique unless a mass is identified or suspected. Where surgical resection or biopsy of a space-occupying lesion is contemplated, contrast enhancement can be valuable in assessing relative vascularity and aiding diagnostic specificity. It should be continually emphasized that CT is a powerful technology which, in orbital diagnosis, produces the highest yield when clinician and radiologist collaborate in the radiodiagnostic workup. The clinical information supplied by the referring ophthalmologist is used by the radiologist both in the selection of the appropriate techniques for investigation and in striving to achieve the most specific conclusion.

Contrast Media↗