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PubMed2001

[Dosimetry with radiosensitive gels in radiotherapy. Methods].

The goal of conformal radiotherapy is to concentrate the dose in a well-defined volume by avoiding the neighbouring healthy structures. This technique requires powerful treatment planning software and a rigorous control of estimated dosimetry. The usual dosimetric tools are not adapted to visualize and validate complex 3D treatment. Dosimetry by radiosensitive gel permits visualization and measurement of the three-dimensional dose distribution. The objective of this work is to report on current work in this field and, based on our results and our experience, to draw prospects for an optimal use of this technique. Further developments will relate to the realization of new radiosensitive gels satisfying, as well as possible, cost requirements, easy realization and use, magnetic resonance imagery (MRI) sensitivity, tissue equivalence, and stability. Other developments focus on scanning methods, especially in MRI to measure T1 and T2.

Calibration↗
PubMed2000

Measuring the capacity of families to provide unpaid support for a disabled family member: using BIGSTEPS to identify primary and secondary dimensions.

The Principal Components subroutine of the BIGSTEPS computer program (Rasch analysis) was used to identify primary and secondary dimensions within an item set composed of variables pertaining to family capacity to provide assistance to a family member with disability. Data were obtained through interviews with family caregivers of patients in a major rehabilitation hospital, both during patients' inpatient rehabilitation stay and 3 and 6 months after inpatient discharge. Rasch analysis revealed the primary dimension within these data to be family capacity to provide unpaid instrumental help (18 items) and the strongest secondary dimension to be stressors on the caregivers as assessed during the inpatient stay (5-11 items). A scale consisting of the caregiver stressor items significantly predicted patients' functional gain at 3 months after discharge from inpatient rehabilitation (r = -.21) and at 6 months (r = -.20), and also the number of days that the patient had spent in a nursing facility as of 6 months after discharge (r = +.17). Caregiver stress, burnout, and quality of life at 3 months and 6 months were also significantly predicted. These findings strongly suggest the importance of more definitive research into family stressors that affect long-term patient outcomes.

Activities of Daily Living↗
PubMed2003

[Computerized physician order entry, a tool for added safety in the hospital].

DRUG-RELATED IATROGENIC NOSOCOMIAL ILLNESS: Remains a matter of concern in the public health area. Responsibility of hospitals is challenged by the ever increasing number of patients' claims. Dysfunction in the drug-prescribing and delivery system account, to a large extent, for medication errors, some of them resulting in adverse drug events. Most generally, medication ordering by the physician is handwritten, without nominative recapitulating prescriptions, and followed by nurse transcriptions and a global medication order is transmitted to the pharmacy. This system does not integrate the pharmaceutical analysis of the prescription, before distribution of the drugs. THE COMPUTERIZED DRUG ORDER ENTRY PROCESS: The prescription is entered directly and is displayed on the computer screen, together with the previous prescriptions for the same patient. Transcription is hence eliminated. Depending on the sophistication of the software, the prescription undergoes a series of tests; warnings and reminders can be displayed online before the physician validates the prescription. Moreover, various guidelines in some aspects of drug therapy may be presented online before the prescription is completed. POSSIBILITIES: The pharmacist's access to the complete prescriptions permits analysis of the quality and safety of the prescriptions and the adequation with eventual current applicable recommendations. Prospective drug utilization review, with immediate feedback to the prescribing physician in case of concern, may be undertaken, further improving the quality of drug therapy. Moreover, a work sheet is printed out for the nurses, further enhancing the safety of drug administration and validation. The computerized drug network also permits the development of other functions. A TOOL FOR SAFETY: Currently available reports in the literature suggest that computerized drug prescription reduces the incidence of prescribing errors, improves the appropriateness of drug choices, optimises therapeutic follow-up, and reduces the incidence adverse drug events and leads to substantial reduction in drug expenditures.

Computers↗
PubMedDate not supplied

[Cyclosporin pharmacokinetic modeling in renal transplant patients].

AIM: To characterize the pharmacokinetic behavior of oral cyclosporin (CsA) in renal transplant patient, based on through blood concentration (C0) value, and to develop and to evaluate a Bayesian method for the individualized adjustment of CsA daily dose (DD). METHODS: Sixty-seven renal allograft recipients (42 men and 25 women) who had been treated with CsA (Sandimmun Neoral) associated with mycophenolate mofetil (2g daily) and prednisone (0,5-1 mg/kg daily) were randomly divided into two groups. Group A (N=48) was used to characterize CsA pharmacokinetic behavior and Group B (N=19) to evaluate Bayesian predictive performance for the model developed. We evaluated different structural models using non linear mixed effects modeling implemented in the NONMEN computer program in order to quantify the relationship between DD and C0. Accuracy and precision were evaluated by the mean standardized prediction error and its standard deviation. RESULTS: The Michaelis-Menten model was found to be optimum for quantifying the relationship between DD and C0. This model includes time-dependent parameters such as the Michaelis-Menten constant (Km) and daily maximum dose (Dmax) as well as first order autoregressive terms DD and C0 included in the structural model in an additive way. In the final model, the Dmax parameter is affected by plasmatic urea values and shows a half-life stabilization time of 90.90 days (95% CI: 52.60 to 250 days). Plasmatic urea values of 50 mg/dL are related to an initial Dmax value of 3 mg/kg daily (95% CI: 1.81 to 4.19 mg/kg daily) which decreases exponentially throughout the post-transplant period until it reaches a constant value of 2.16 mg/kg daily (95% CI: 1.41 to 2.91 mg/kg daily) In the same way, the Km parameter presents a central tendency value of 93.60 ng/mL (95% CI: 28.60 to 158.60 ng/mL) and the half-life necessary for its stabilization is 12.70 days (95% CI: 9.80 to 17.90 days). The residual variability of the model is 8.2%. The mean value of standardized prediction errors for populations and its standard deviation, as well as its confidence intervals of 95%, confirm the appropriate accuracy and precision of both a priori and a posteriori predictions with this model. Also, it reached between 70 and 100% a posteriori sequential predictions with prediction errors below 10%. CONCLUSION: The characterization of the pharmacokinetic behavior of CsA requires us to consider parameters such as Dmax and Km as non lineal functions of time, while the first order autoregressive terms DD and C0 must also be incorporated into the model.

Adult↗
PubMed2006

[Bone density change simulation by using internal bone remodeling theory and finite element method].

This paper presents an investigation on the effect of external force on internal bone remodeling by adopting the internal bone remodeling theory in conjunction with finite element method. After the border data are picked from a tomogram, a two-dimensional bone model is formed. The bone remodeling results are obtained by use of the finite element software Ansys. The results agree well with the real structure of bone in some degree, thus demonstrating the validity of the proposed method.

Biomechanical Phenomena↗
PubMed1999

Validation of an optical flow method for tag displacement estimation.

We present a validation study of an optical-flow method for the rapid estimation of myocardial displacement in magnetic resonance tagged cardiac images. This registration and change visualization (RCV) software uses a hierarchical estimation technique to compute the flow field that describes the warping of an image of one cardiac phase into alignment with the next. This method overcomes the requirement of constant pixel intensity in standard optical-flow methods by preprocessing the input images to reduce any intensity bias which results from the reduction in stripe contrast throughout the cardiac cycle. To validate the method, SPAMM-tagged images were acquired of a silicon gel phantom with simulated rotational motion. The pixel displacement was estimated with the RCV method and the error in pixel tracking was <4% 1000 ms after application of the tags, and after 30 degrees of rotation. An additional study was performed using a SPAMM-tagged multiphase slice of a canine left ventricle. The true displacement was determined using a previously validated active contour model (snakes). The error between methods was 6.7% at end systole. The RCV method has the advantage of tracking all pixels in the image in a substantially shorter period than the snakes method.

Animals↗
PubMed2001

A computer-based laparoscopic skills assessment device differentiates experienced from novice laparoscopic surgeons.

BACKGROUND: The acquisition of laparoscopic skills is difficult to assess. Previously, through the use of a computer-based skills assessment device (SAD), we have shown that assessments of the time needed to perform a task and graded observations of task performance overestimate the speed at which laparoscopic skills can be acquired. The aim of this study was to test the ability of a laparoscopic SAD to differentiate novices from experienced laparoscopic surgeons and thereby further validate its use in surgical education. METHODS: Using a laparoscopic simulator platform integrated with task simulation and data collection software (MIST VR), we tested both experienced and novice laparoscopists. Each group performed three tasks with a minimum of seven repetitions. The tasks consisted of target acquisition, target traversal, and target manipulation with diathermy. Within each task, time (T), errors (E), and economy of movement for each hand (EML, EMR) were assessed. Results were reported as mean +/- SEM, and comparisons were made using an independent samples t-test. RESULTS: For the target acquisition task, the expert group performed the task faster than the novice group (5.5 +/- 0.24 vs 7.6 +/- 0.40 sec, p < 0.05); the experts also made fewer errors (0.5 +/- 0.10 vs 0.8 +/- 0.11 errors, p < 0.05), and achieved both a better EML (1.8 +/- 0.6 vs 2.3 +/- 0.9, p < 0.05) and a better EMR (2.0 +/- 0.1 vs 2.9 +/- 0.21, p < 0.05). In the target traversal task, the experts made fewer errors than the novices (2.2 +/- 0.25 vs 4.6 +/- 0.38 errors, p < 0.05). For the manipulation and diathermy tasks, the expert group completed the task faster (30.8 +/- 1.5 vs 39 +/- 1.5 sec, p < 0.05), made fewer errors (5.3 +/- 0.59 vs 8.1 +/- 0.63 errors, p < 0.05), and had a better EML (6.0 +/- 0.37 vs 7.2 +/- 0.45, p < 0.05) and EMR (4.3 +/- 0.23 vs 5.8 +/- 0.36, p < 0.05) than the novices. CONCLUSION: A laparoscopic skills assessment device can discern levels of laparoscopic manipulative skill. This type of device can be used in surgical training to make objective assessments of the acquisition of laparoscopic skills.

Clinical Competence↗
PubMed1989

Validation of an imaging system: steps to evaluate and validate a microscope imaging system for quantitative studies.

The processing methods described in this article are general and can be used with any computer with adequate software without reference to a specific experimental apparatus. To achieve appropriately corrected images, the operations must be performed correctly and in a specific order to extract meaningful information from digital images. The operations are subtraction of the dark current, a shading correction after low pass filtering of the shading mask, a geometric correction with a reference grid obtained at the longest wavelength of interest, and finally registration. Since the digital data sets are too large for manual evaluation, statistical criteria must be used to define the analytical capabilities and error limits of the system before the more interesting cellular studies can be undertaken.

Algorithms↗
PubMed2006

Semi-automated quantification of axonal densities in labeled CNS tissue.

Current techniques used to quantify axons often rely upon manual quantification or potentially expensive commercially available programs for automated quantification. We describe a computerized method for the detection and quantification of axons in the rat CNS using readily available free software. Feature J, a java-based plug-in to the imaging software NIH Image J, faithfully detects linear structures such as axons in confocal or bright-field images using a Hessian-based algorithm. We validated the method by comparing values obtained by manual and automated analyses of axons induced to grow in response to neurotrophin over-expression in the rat spinal cord. We also demonstrated that the program can be used to quantify neurotrophin-induced growth of lesioned serotonergic axons in the rat cortex, where manual measurement would be impractical due to dense axonal growth. The use of this software suite provided faster and less biased quantification of labeled axons in comparison to manual measurements at no cost.

Algorithms↗
PubMed2005

Application of validated QSAR models of D1 dopaminergic antagonists for database mining.

Rigorously validated quantitative structure-activity relationship (QSAR) models have been developed for 48 antagonists of the dopamine D1 receptor and applied to mining chemical datasets to discover novel potential antagonists. Several QSAR methods have been employed, including comparative molecular field analysis (CoMFA), simulated annealing-partial least squares (SA-PLS), k-nearest neighbor (kNN), and support vector machines (SVM). With the exception of CoMFA, these approaches employed 2D topological descriptors generated with the MolConnZ software package (EduSoft, LLC. MolconnZ, version 4.05; http://www.eslc.vabiotech.com/ [4.05], 2003). The original dataset was split into training and test sets to allow for external validation of each training set model. The resulting models were characterized by cross-validated R2 (q2) for the training set and predictive R2 values for the test set of (q2/R2) 0.51/0.47 for CoMFA, 0.7/0.76 for kNN, R2 for the training and test sets of 0.74/0.71 for SVM, and training set fitness and test set R2 values of 0.68/0.63 for SA-PLS. Validated QSAR models with R2 > 0.7, (i.e., kNN and SVM) were used to mine three publicly available chemical databases: the National Cancer Institute (NCI) database of ca. 250,000 compounds, the Maybridge Database of ca. 56,000 compounds, and the ChemDiv Database of ca. 450,000 compounds. These searches resulted in only 54 consensus hits (i.e., predicted active by all models); five of them were previously characterized as dopamine D1 ligands, but were not present in the original dataset. A small fraction of the purported D1 ligands did not contain a catechol ring found in all known dopamine full agonist ligands, suggesting that they may be novel structural antagonist leads. This study illustrates that the combined application of predictive QSAR modeling and database mining may provide an important avenue for rational computer-aided drug discovery.

Databases, Factual↗
PubMed2005

[Research advance on lake ecosystem dynamic models].

Starting with the role of system analysis in lake ecosystem research, this paper summarized the tentative procedures and softwares for studying the dynamics of lake ecosystem. There are several main stages in modeling the dynamics of lake ecosystem, namely, problems identification, mathematical formulation, computation, validation, sensitive analysis, calibration, and verification. In the modeling, selecting temporal and spatial scales is essential but complex. Since 1960s, a rapid progress has been made in modeling the dynamics of lake ecosystem, being developed from simple zero-dimension models to complex ecological-aquatic-hydrodynamic ones, among which, exergy was applied popularly as an objective function in modeling. In this paper, LakeWeb and LEEDS (Lake Eutrophication, Effect, Dose, and Sensitivity model) were analyzed as examples. In China, the development of lake ecosystem dynamic models could be traced back to 1980s, and most of them were focused on Lake Dianch, Lake Taihu, Lake Chaohu and Lake Donghu. Some softwares such as CE-QUAL-ICM, WASP, AQUATOX, PAMOLARE and CAEDYM were developed to simulate lake ecosystem dynamics, among which, CE-QUAL-ICM is more suitable for long and narrow water bodies. WASP consists of three parts, i. e., DYNHYD, EUTRO, and TOXI. AQUATOX is an ecological risk model, and the parameters are mainly calibrated in U. S. A, which has limited its further application in China. The software ECOPATH for simulating the energy flows in lakes was also described in this paper. There are still many shortages in the lake ecosystem dynamic models, e. g., the lack of sufficient monitoring data for validation, insufficient consideration of uncertainties and the role of bacteria, and inconsistent relationship with watershed changes. The uncertainties are mainly from the intrinsic uncertainties in aquatic ecosystem, in modeling, in parameters selection, and also in forecast and application. Setting up long-term monitoring and data sharing mechanism, using interpolation to make data more densely, introducing objective functions, dealing with uncertainties, and constructing watershed-lake ecosystem dynamic model could be the available ways for overcoming the shortages.

China↗
PubMed2005

Revised Space Fortress: a validation study.

We describe briefly the redevelopment of Space Fortress (SF), a research tool widely used to study training of complex tasks involving both cognitive and motor skills, to be executed on current-generation systems with significantly extended capabilities, and then compare the performance of human participants on an original PC version of Space Fortress (SF) with the revised Space Fortress (RSF). Participants trained on SF or RSF for 10 sets of eight 3-min practice trials and two 3-min test trials. They then took tests involving retention, resistance to secondary task interference, and transfer to a different control system. They then switched from SF to RSF or from RSF to SF for 2 sets of final tests and completed rating scales comparing RSF and SE Slight differences were predicted on the basis of a scoring error in the original version of SF used and on slightly more precise joystick control in RSF. The predictions were supported. The SF group started better but did worse when they transferred to RSE Despite the disadvantage of having to be cautious in generalizing from RSF to SF, we conclude that RSF has many advantages, which include accommodating new PC hardware and new training techniques. A monograph that presents the methodology used in creating RSF, details on its performance and validation, and directions on how to download free copies of the system may be downloaded from www.psychonomic.org/archive/.

Adolescent↗
PubMed2006

PROFtmb: a web server for predicting bacterial transmembrane beta barrel proteins.

PROFtmb predicts transmembrane beta-barrel (TMB) proteins in Gram-negative bacteria. For each query protein, PROFtmb provides both a Z-value indicating that the protein actually contains a membrane barrel, and a four-state per-residue labeling of upward- and downward-facing strands, periplasmic hairpins and extracellular loops. While most users submit individual proteins known to contain TMBs, some groups submit entire proteomes to screen for potential TMBs. Response time is about 4 min for a 500-residue protein. PROFtmb is a profile-based Hidden Markov Model (HMM) with an architecture mirroring the structure of TMBs. The per-residue accuracy on the 8-fold cross-validated testing set is 86% while whole-protein discrimination accuracy was 70 at 60% coverage. The PROFtmb web server includes all source code, training data and whole-proteome predictions from 78 Gram-negative bacterial genomes and is available freely and without registration at http://rostlab.org/services/proftmb.

Bacterial Proteins↗
PubMed2004

Evaluation of the electromagnetic field level emitted by medium frequency AM broadcast stations.

In order to estimate the level of the electromagnetic field produced by telecommunication systems, different computational techniques can be employed whose complexity depends on the accuracy of the final results. In this paper, we present the validation of a code based on the method of moments that allows us to analyse the electromagnetic field emitted by radio-communication systems operating at medium frequencies. The method is able to provide an accurate estimate of the levels of electromagnetic field produced by this type of device and, consequently, it can be used as a method for verifying the compliance of the system with the safe exposure level regulations and population protection laws. Some numerical and experimental results are shown relevant to an amplitude modulated (AM) radio transmitter, together with the results of a forthcoming system that will be operative in the near future.

Algorithms↗
PubMed2006

Marginal modeling of nonnested multilevel data using standard software.

Epidemiologic data are often clustered within multiple levels that may not be nested within each other. Generalized estimating equations are commonly used to adjust for correlation among observations within clusters when fitting regression models; however, standard software does not currently accommodate nonnested clusters. This paper introduces a simple generalized estimating equation strategy that uses available commercial or public software for the regression analysis of nonnested multilevel data. The authors describe how to obtain empirical standard error estimates for constructing valid confidence intervals and conducting statistical hypothesis tests. The method is evaluated using simulations and illustrated with an analysis of data from the Breast Cancer Surveillance Consortium that estimates the influence of woman, radiologist, and facility characteristics on the positive predictive value of screening mammography. Performance with a small number of clusters is discussed. Both the simulations and the example demonstrate the importance of accounting for the correlation within all levels of clustering for proper inference.

Adult↗
PubMed2002

Training and pretreatment planning of interventional neuroradiology procedures--initial clinical validation.

A PC based system for simulating image-guided interventional neuroradiological procedures for physician training and patient specific pretreatment planning is described. The system allows physicians to manipulate and interface interventional devices such as catheters, guidewires, stents and coils within 2-D and hybrid surface and volume rendered 3-D patient vascular images in real time. A finite element method is employed to model the interaction of the catheters and guidewires with the vascular system. Fluoroscopic, roadmapping and volume rendered 3-D presentations of the vasculature are provided. System software libraries allow for the use of commonly employed catheters, guidewires, stents and occluding coils of various shapes and sizes. The results of an initial clinical validation suggest that the experience gained from our simulator is comparable with that of using a vascular phantom. We are conducting further validation with the aim of providing patient specific pretreatment planning.

Angioplasty, Balloon↗
PubMed2004

A computational tool based on voxel geometry for dose reconstruction of a radiological accident due to external exposure.

In the case of overexposure to ionising radiation, estimation of the absorbed dose in the organism is an important indicator for evaluating the biological consequences of this exposure. The physical dosimetry approach is based either on real reconstruction of the accident, using physical phantoms, or on calculation techniques. Tools using Monte Carlo simulations associated with geometric models are very powerful since they offer the possibility to simulate faithfully the victim and the environment for dose calculations in various accidental situations. Their work presents a new computational tool, called SESAME, dedicated to dose reconstruction of radiological accidents based on anthropomorphic voxel phantoms built from real medical images of the victim in association with the MCNP Monte Carlo code. The utility was, as a first step, validated for neutrons by experimental means using a physical tissue-equivalent phantom.

Algorithms↗
PubMed2005

Talairach-based parcellation of neonatal brain magnetic resonance imaging data: validation of a new approach.

BACKGROUND AND PURPOSE: Talairach-based parcellation (TP) of human brain magnetic resonance imaging (MRI) data has been used increasingly in clinical research to make regional measurements of brain structures in vivo. Recently, TP has been applied to pediatric research to elucidate the changes in regional brain volumes related to several neurological disorders. However, all freely available tools have been designed to parcellate adult brain MRI data. Parcellation of neonatal MRI data is very challenging owing to the lack of strong signal contrast, variability in signal intensity within tissues, and the small size and thus difficulty in identifying small structures used as landmarks for TP. Hence the authors designed and validated a new interactive tool to parcellate brain MRI data from newborns and young infants. METHODS: The authors' tool was developed as part of a postprocessing pipeline, which includes registration of multichannel MR images, segmentation, and parcellation of the segmented data. The tool employs user-friendly interactive software to visualize and assign the anatomic landmarks required for parcellation, after which the planes and parcels are generated automatically by the algorithm. The authors then performed 3 sets of validation experiments to test the precision and reliability of their tool. RESULTS: Validation experiments of intra-and interrater reliability on data obtained from newborn and 1-year-old children showed a very high sensitivity of >95% and specificity >99.9%. The authors also showed that rotating and reformatting the original MRI data results in a statistically significant difference in parcel volumes, demonstrating the importance of using a tool such as theirs that does not require realignment of the data prior to parcellation. CONCLUSIONS: To the authors' knowledge, the presented approach is the first TP method that has been developed and validated specifically for neonatal brain MRI data. Their approach would also be valuable for the analysis of brain MRI data from older children and adults.

Brain↗

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