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At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Angiographic computed tomography is comparable to multislice computed tomography in lumbar myelographic imaging.

We evaluated the feasibility of angiographic computed tomography (ACT) for diagnostic imaging in a patient with degenerative lumbar spine disease. ACT provides a volume data set out of a rotational acquisition with a c-arm-mounted flat-panel detector. Using this technique, radiographic myelography and myelographic computed tomography can be performed in a single session at the same imaging system. The quality of the reconstructed ACT slice images is comparable to those acquired by postmyelographic computed tomography.

Aged↗
PubMed2006

Improvement of low-contrast detectability in low-dose hepatic multidetector computed tomography using a novel adaptive filter: evaluation with a computer-simulated liver including tumors.

PURPOSE: The purpose of this study was to investigate how much radiation dose can be reduced without loss of low-contrast detectability with a newly developed adaptive noise reduction filter in hepatic multidetector computed tomography (MDCT) scans by using a computer-simulated liver phantom. MATERIALS AND METHODS: Simulated CT images, including liver and intrahepatic tumors, were mathematically constructed using a computer workstation to evaluate low-contrast detectability by the observer performance test. Milliampere second for construction of simulated images were 60, 80, 100, and 120 mAs (low dose) and 160 mAs (standard dose) at 120 kVp. Images with 60, 80, 100, and 120 mAs were postprocessed with the adaptive noise reduction filter. A total of 432 images were prepared and receiver operating characteristic (ROC) analysis was performed by 5 radiologists. The detectability of simulated tumor by radiologists was estimated with the area under the ROC curves (Az values). In addition, we visually evaluated CT images of 15 patients with chronic liver damage for graininess of the liver parenchyma, sharpness of the liver contour, conspicuity and marginal sharpness of the liver tumors, and overall image quality. RESULTS: The mean Az value at 0.777 (60 mAs), 0.828 (80 mAs), and 0.844 (100 mAs) without filter was significantly lower than that of 160 mAs without filter (P < 0.001, 60 mAs; P = 0.010, 80 mAs; P = 0.040, 100 mAs). There was no statistical difference between the mean Az value at 80 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.220) and 100 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.979). In the visual evaluation of patient livers, there was no statistical difference in the graininess and sharpness of the liver, the conspicuity and marginal sharpness of the tumor, and the overall image quality between standard-dose and filtered low-dose images (Wilcoxon signed rank test, P > 0.05). CONCLUSION: The radiation dose can be reduced by 50% without loss of nodule detectability by applying the adaptive noise reduction filter to simulated and patient liver images obtained at MDCT.

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PubMed2002

High-performance computing in computational fluid dynamics: progress and challenges.

Computational fluid dynamics (CFD) is by far the largest user of high-performance computing (HPC) in engineering. The main scientific challenge is the need to gain a greater understanding of turbulence and its consequences for the transfer of momentum, heat and mass in engineering applications, including aerodynamics, industrial flows and combustion systems. Availability of HPC has led to significant advances in direct numerical simulation (DNS) of turbulence and turbulent combustion, and has encouraged the development of large-eddy simulation (LES) for engineering flows. The statistical data generated by DNS have provided valuable insight into the physics of many turbulent flows and have led to rapid improvements in turbulence and combustion modelling for industry. Nevertheless, major challenges remain and the computational requirements for turbulence research, driven by well-established physical scaling laws, are likely to remain at the limit of the available HPC provision for some time to come.

Air Movements↗
PubMed2002

Identification of a novel cis-regulatory element involved in the heat shock response in Caenorhabditis elegans using microarray gene expression and computational methods.

We report here the identification of a previously unknown transcription regulatory element for heat shock (HS) genes in Caenorhabditis elegans. We monitored the expression pattern of 11,917 genes from C. elegans to determine the genes that were up-regulated on HS. Twenty eight genes were observed to be consistently up-regulated in several different repetitions of the experiments. We analyzed the upstream regions of these genes using computational DNA pattern recognition methods. Two potential cis-regulatory motifs were identified in this way. One of these motifs (TTCTAGAA) was the DNA binding motif for the heat shock factor (HSF), whereas the other (GGGTGTC) was previously unreported in the literature. We determined the significance of these motifs for the HS genes using different statistical tests and parameters. Comparative sequence analysis of orthologous HS genes from C. elegans and Caenorhabditis briggsae indicated that the identified DNA regulatory motifs are conserved across related species. The role of the identified DNA sites in regulation of HS genes was tested by in vitro mutagenesis of a green fluorescent protein (GFP) reporter transgene driven by the C. elegans hsp-16-2 promoter. DNA sites corresponding to both motifs are shown to play a significant role in up-regulation of the hsp-16-2 gene on HS. This is one of the rare instances in which a novel regulatory element, identified using computational methods, is shown to be biologically active. The contributions of individual sites toward induction of transcription on HS are nonadditive, which indicates interaction and cross-talk between the sites, possibly through the transcription factors (TFs) binding to these sites.

Animals↗
PubMedDate not supplied

Primer on computers and information technology. Part two: an introduction to computer networking.

Computers networks are a way of connecting computers together such that they can exchange information. For this exchange to be successful, system behavior must be planned and specified very clearly at a number of different levels. Although there are many choices to be made at each level, often there are simple decisions that can be made to rapidly reduce the number of options. Planning is most important at the highest (application) and lowest (wiring) levels, whereas the middle levels must be specified to ensure compatibility. Because of the widespread use of the Internet, solutions based on Internet technologies are often cost-effective and should be considered when designing a network. As in all technical fields, consultation with experts (ie, computer networking specialists) may be worthwhile.

Computer Communication Networks↗
PubMed1984

Computer simulation for the stereotactic placement of interstitial radionuclide sources into computed tomography-defined tumor volumes.

This report describes a method for the preoperative determination of radioactive interstitial source placement within computed tomography (CT)-defined tumor boundaries. The method utilizes CT data obtained under stereotactic conditions. Tumor boundaries are digitized from CT slices and are retained in a three-dimensional computer matrix. A solid tumor volume is created by an interpolation program and may be sliced orthogonal to any specific stereotactic surgical view line. The surgeon may simulate radioactive source placement within the slices and view the resultant isodose configuration against tumor contours on successive slices. Once the best source placement has been determined, the computer outputs the mechanical adjustments that will be necessary on a stereotactic frame located in the operating room for the stereotactic placement of each source and gives the length of each source. Sources are stereotactically implanted utilizing a double-catheter afterloading technique.

Adult↗
PubMed1997

Psychology of computer use: XLIV. Computer anxiety and learning style.

The relation between scores for computer anxiety and for Kolb's Learning Style Inventory was investigated (N = 204). Scores on computer anxiety correlated negatively with scores on the Active-Reflective index. Further, those classified as Convergers reported lower scores on computer anxiety than did those classified as Divergers.

Adult↗
PubMed2002

Advances in computing, and their impact on scientific computing.

This paper begins by discussing the developments and trends in computer hardware, starting with the basic components (microprocessors, memory, disks, system interconnect, networking and visualization) before looking at complete systems (death of vector supercomputing, slow demise of large shared-memory systems, rapid growth in very large clusters of PCs). It then considers the software side, the relative maturity of shared-memory (OpenMP) and distributed-memory (MPI) programming environments, and new developments in 'grid computing'. Finally, it touches on the increasing importance of software packages in scientific computing, and the increased importance and difficulty of introducing good software engineering practices into very large academic software development projects.

Computer Simulation↗
PubMed1984

Computation of glomerular filtration rate with Tc-99m DTPA: an in-house computer program.

The glomerular filtration rate (GFR) can be computed from the scintigraphic determination of Tc-99m DTPA (diethylenetriaminepentaacetic acid) uptake within the kidneys. The required computations are straightforward and can easily be included in the software of various computers, including a hospital's existing data-processing system. This report presents a complete operational program based on extensive experience with this method. The program is easy to use, allows for adjustments to be made for unusual clinical conditions, and produces a permanent record that can be issued as part of the final report.

Computers↗
PubMedDate not supplied

A computer assisted tutorial for applications of computer spreadsheets in nursing financial management.

A computer-based tutorial for teaching nursing financial management concepts was developed using the macro function of a commercially available spreadsheet program. The goals of the tutorial were to provide students with an experience with spreadsheets as a computer tool and to teach selected financial management concepts. Preliminary results show the tutorial was well received by students. Suggestions are made for overcoming the general lack of computer sophistication among students.

Budgets↗
PubMed2000

Paradoxical emboli: demonstration using helical computed tomography of the pulmonary artery associated with abdominal computed tomography.

We report the case of a 60-year-old woman with a recent history of a cerebrovascular accident. Because of clinical suspicion of pulmonary embolism and negative Doppler ultrasound findings of the lower limbs, spiral computed tomography of the pulmonary artery was performed and demonstrated pulmonary emboli. We emphasize the role of computed tomography of the abdomen, performed 3 min after the thoracic acquisition, which showed an unsuspected thrombus within the abdominal aorta and the left renal artery with infarction of the left kidney. Paradoxical embolism was highly suspected on computed tomography data and confirmed by echocardiography which demonstrated a patent foramen ovale.

Aorta, Abdominal↗
PubMed2006

Computational modeling of arterial wall growth. Attempts towards patient-specific simulations based on computer tomography.

The present manuscript documents our first experiences with a computational model for stress-induced arterial wall growth and in-stent restenosis related to atherosclerosis. The underlying theoretical framework is provided by the kinematics of finite growth combined with open system thermodynamics. The computational simulation is embedded in a finite element approach in which growth is essentially captured by a single scalar-valued growth factor introduced as internal variable on the integration point level. The conceptual simplicity of the model enables its straightforward implementation into standard commercial finite element codes. Qualitative studies of stress-induced changes of the arterial wall thickness in response to balloon angioplasty or stenting are presented to illustrate the features of the suggested growth model. First attempts towards a patient-specific simulation based on realistic artery morphologies generated from computer tomography data are discussed.

Aorta↗
PubMed1977

A computer program for the on-line computation of cardiac output from thermodilution curves.

An accurate, rapid calculation of Cardiac Output is of great importance during the treatment of critically ill patients. This paper describes a complete, self-contained mini-computer system, based on a Data General NOVA 1220 which can accurately sample data and compute the results in about 30 sec. The system uses the thermodilution method with a Swan-Ganz catheter to collect data and a weighted least-squares technique to compute the results.

Cardiac Catheterization↗
PubMed1988

A computer program in compiled BASIC for the IBM personal computer to calculate the mean platelet survival time with the multiple-hit and weighted mean methods.

We developed an easy-to-operate computer program for the IBM personal computer to calculate, display and store in a database platelet kinetic data determined by analysis of the rate of clearance of radiolabeled blood platelets from the circulation. This was done by curve fitting using the weighted mean method and multiple-hit model. These models are complementary and calculating the mean platelet survival time with both is recommended. Improvement of the weighted mean method was investigated. The optimized weighting and fitting the exponential function with the Marquardt non-linear least squares method improved the weighted mean method. The weighted mean and multiple-hit models fit the survival curve data equally well. The calculation of the mean platelet survival time with the weighted mean method was very fast. The duration of calculation with the multiple-hit model could take up to 2 minutes. Calculation of the mean platelet survival time using both models has the advantage that conditions when calculation of the mean platelet survival time would be invalid, can be detected. The computer program will promote the valid comparison of results obtained at different institutions.

Blood Platelets↗
PubMedDate not supplied

Computer interface and software analysis for multi-channel, on-line temperature recording to any micro-computer.

A simple, inexpensive computer interface designed for in vitro or in vivo researchers with limited electronic experience allows direct on-line multi-channel temperature recording from thermistor probes to any micro-computer. The designed system saves time and increases the accuracy of collected data that are ready for storage in files compatible with graphic and statistical software. In vitro testing of the designed interface, over a range of 25-45 degrees C, showed a 0.999 intraclass correlation to reference water bath temperatures. In vivo testing using anesthetized rats involved simultaneous measurements of: (1) a thermogenic tissue, interscapular brown adipose temperature (IBAT), (2) core (colonic) temperature, and (3) surface (tail) temperature, a heat loss tissue. The temperatures measured by the designed computer-interface demonstrate excellent stability, sensitivity and accuracy when compared to respective temperatures measured by a YSI telethermometer.

Animals↗
PubMed2006

Computer-aided detection of solid lung nodules in lossy compressed multidetector computed tomography chest exams.

RATIONALE AND OBJECTIVES: To assess the effect of three-dimensional (3D) lossy image compression of multidetector computed tomography chest scans on computer-aided detection (CAD) of solid lung nodules greater than 4 mm in size. MATERIALS AND METHODS: A total of 120 cases, acquired with 1.25-mm collimation, were collected from 5 different sites, of which 66/120 were low-dose cases. Two chest radiologists established that 37 cases had no actionable lung nodules; the remaining 83 cases contained 169 nodules (range 3.8-35.0 mm, mean 5.8 mm +/- 3.0 [SD]). All cases were compressed using the 3D Set Partitioning in Hierarchical Trees algorithm to 24:1, 48:1, and 96:1 levels. A study of the effect of compression on computer-aided detection (CAD) sensitivity was performed at operating points of 2.5 false marks (FM), 5 FM, and 10 FM per case using McNemar's test. Logistic regression models were used to evaluate the impact on CAD sensitivity by compression level on nodule and image characteristics. RESULTS: Compared with no compression, there was no significant degradation in CAD sensitivity found at any of the studied compression levels and operating points. However, between compression levels, there was marginal association with sensitivity. Specifically, 24:1 level was significantly better than 96:1 at all operating points, and occasionally better than no compression at 10 FM/case. Based on multivariate analysis, nodule location was found to be a significant predictor (P = .01) with a lower sensitivity associated with juxtapleural nodules. Nodule size, dose, reconstruction filter, and contrast medium were not significant predictors. CONCLUSION: CAD detection performance of solid lung nodules did not suffer until 48:1 compression.

Algorithms↗
PubMed2005

Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation.

To compare the alignment after computer-navigated total knee arthroplasty, 52 patients were randomly allocated to 2 groups. Twenty-seven patients received a total knee arthroplasty with the aid of a kinematic computer-navigation system, and 25 patients received a total knee arthroplasty with the conventional method. Both groups were well balanced concerning demographic data and preoperative scores. At 3-month follow-up, the mechanical alignment of the leg reached the desired straight axis in more cases with the computer-navigated implantation. This difference was statistically significant. The femoral and tibial mechanical anteroposterior axis and the femoral and tibial sagittal tilt (slope) measured on sagittal x-rays were not significantly improved in this patient group.

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PubMed2006

Trapezius muscle rest time during standardised computer work--a comparison of female computer users with and without self-reported neck/shoulder complaints.

Work related musculoskeletal disorders (WMSDs) in the shoulder/neck area are a common and increasing problem among European computer workers, especially women. Long-term low-level workloads with low degree of muscle rest are a potential risk factor for developing WMSDs. The purpose of the present study of female computer users (age 45-65 years) in Denmark and Sweden was to investigate if subjects with self-reported neck/shoulder complaints (cases, N=35) show less trapezius muscle relative rest time (RRT) than controls (N=44) when performing standardised short-term computer work tasks in controlled laboratory conditions. Surface electromyography (EMG) signals were recorded bilaterally from the upper trapezius muscles during a type, edit, precision and colour word stress task. Besides RRT, 10th percentile RMS values were calculated. On the average, 15 of the cases and 18 of the controls showed analysable EMG files per task. For the colour word stress task, the results showed lower RRT values and higher 10th percentile RMS amplitude levels among cases compared to controls. No such signs could be found for the other tasks performed. The present results indicate an increased motor response to a psychological stressor among subjects with self-reported neck/shoulder complaints.

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