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PubMed2005

Expanding the range of free calcium regulation in biological solutions.

Many biological systems use ethylene glycol bis (beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) to regulate the free calcium concentration ([Ca(2+)](free)) in the presence of physiological levels of free Mg(2+) ([Mg(2+)](free)). Frequently, it is necessary to work at [Ca(2+)](free) beyond EGTA's buffering capabilities. Therefore, we have developed methods to extend the buffering range by adding nitrilotriacetic acid (NTA) to solutions containing EGTA. This extension results from NTA having a lower K'(dCa) than EGTA. Such equilibria are solved by pCa Calculator, a computer program designed to aid in the study of Ca(2+)-dependent physiological processes while accounting for the effects of pH, temperature, and ionic strength. With multiple chelators and pH buffers from which to choose, pCa Calculator calculates the total concentration of each species required to achieve specified free concentrations of Ca(2+), ATP, and Mg(2+). The program is intuitive, user-friendly, and flexible enough to fix or vary the [Mg-ATP(2-)] and ionic strength. Moreover, it can account for increases in experimental volume from calcium addition. A comparative analysis is reported for testing solutions in the presence and absence of NTA by measuring the calcium binding affinity of fluorescent cardiac troponin C. These findings demonstrate that EGTA, when used in conjunction with NTA, improves and expands the regulation of free calcium in solution.

Adenosine Triphosphate↗
PubMed2005

Linear interaction energy models for beta-secretase (BACE) inhibitors: Role of van der Waals, electrostatic, and continuum-solvation terms.

Computing the binding affinity of a protein-ligand complex is one of the most fundamental and difficult tasks in computer-aided drug design. Many approaches for computing binding affinities can be classified as linear interaction energy (LIE) models as they rely on some type of linear fit of computed interaction energies between ligand and protein. We have examined the computed interaction energies of a series of beta-secretase (BACE) inhibitors in terms of van der Waals, coulombic, and continuum-solvation contributions to ligand binding. We have also systematically examined the effect of different protonation states of the protein and ligands. We find that the binding affinities are relatively insensitive to the protonation state of the protein when neutral ligands are considered. Inclusion of charged ligands leads to large deviations in the coulomb, solvation, and even van der Waals terms. The latter is due to increased repulsive van der Waals interactions in the complex due to the strong coulomb attraction found between oppositely charged functional groups in the protein and ligand. In general, we find that the best models are obtained when the protein is judiciously charged (e.g. Asp32-, Arg235+) and the potentially charged ligands are treated as neutral.

Amyloid Precursor Protein Secretases↗
PubMed2001

Computer simulations of lung airway structures using data-driven surface modeling techniques.

Knowledge of human lung morphology is a subject critical to many areas of medicine. The visualization of lung structures naturally lends itself to computer graphics modeling due to the large number of airways involved and the complexities of the branching systems. In this study, a method of generating three-dimensional computer simulations of human lung airway networks using data-driven, surface modeling techniques is presented. By simulating the tubular airway structures and realistic bifurcation shapes, anatomically accurate representations of human lungs are obtained. These computer models are designed for use in computational fluid dynamic applications and particle trajectory analyses, and to be complimentary to medical imaging (gamma scintigraphy) protocols.

Computer Graphics↗
PubMed1997

A computer program to aid in visual concept development in dentistry.

Beginning dental students normally receive their first exposure to the study of tooth forms (morphology) through a dental anatomy laboratory course in which they are required to reproduce tooth morphology, usually with wax. The fabrication of a tooth in wax requires proper visual recognition skills and fine eye-hand coordination. Many students struggle with one or both of these. A computer program, designed to teach recognition concepts, was delivered to three groups of beginning freshman dental students in conjunction with their dental anatomy laboratory course while a group of their classmates served as the controls. This study investigated (1) instructional design and interface improvement and (2) the best method to implement the computer program. Experimental and control groups all received normal daily critiques of their course project work. After completion of the computer program, all groups were tested with a recognition-based examination as well as with a practical examination, requiring the reproduction of a tooth in wax. All experimental groups scored better than the control group on both examinations. Results indicated that computer-based instruction may be a useful means to foster visual concept development. An expanded program, using better graphics, animation and movies is currently under development.

Anatomy↗
PubMed2003

Health and economic impact of posttransfusion hepatitis B and cost-effectiveness analysis of expanded HBV testing protocols of blood donors: a study focused on the European Union.

BACKGROUND: Residual risk of posttransfusion hepatitis B (PT-HB) may be reduced through implementation of HBV NAT or the new, enhanced-sensitivity HBsAg assays in routine donor testing. However, there are some doubts about the cost-effectiveness of these new safety measures, because hepatitis B acquired in adulthood is not regarded as a severe disease in western countries. STUDY DESIGN AND METHODS: A computer model was designed to estimate the health outcomes and associated costs of patients with PT-HB. Results from this model and estimations of the residual risk of HBV transmission, the risk reduction yielded by the new assays, and their cost were used to calculate the cost-effectiveness of including the new HBsAg assays or single-sample HBV NAT in the routine screening of blood donors. RESULTS: The model predicts that 0.97 percent of patients with PT-HB die of liver disease (54% of them due to fulminant hepatitis). The mean loss of life expectancy was 0.178 years per patient, and the present value of the lifetime costs of treating PT-HB was 4160 euros per patient. Single-donor HBV NAT or the new HBsAg assays would increase the life expectancy of blood recipients by 16 (95% CI, 8-40) or 14 (95% CI, 7-28) years, respectively, per every 10 million donations tested. The projected cost per life-year gained was 0.79 (95% CI, 0.15-1.85) million euros for the enhanced-sensitivity HBsAg assays and 5.8 (95% CI, 1.9-13.1) million euros for single-donation HBV NAT, both compared with current HBsAg assays. If single-donation HBV NAT is compared with the new HBsAg assays, its cost- effectiveness ratio increases to 53 (95% CI, 16-127) million euros. CONCLUSION: PT-HB has few health or economic repercussions. Single-donation HBV NAT would provide a small health benefit at a very high cost. Instead, in some circumstances, the cost-effectiveness of enhanced-sensitivity HBsAg assays would be within acceptable ranges for new public health interventions.

Adolescent↗
PubMed2001

Microbiological pollution and ocular infection in CAD operators: an on-site investigation.

A large number of workers are currently employed in tasks involving the use of computer based equipment. Much research has been carried out both on prevalence and incidence of ocular and visual disorders as well as on occupational asthenopia. Less attention has been given to investigating the possibility of a microbiological pollution of Video Display Unit (VDU) workstations and to the consequent possible development of work-related ocular infections. The authors investigated the presence of bacteria and fungi on Computer Assisted Design (CAD) workstations and in the conjunctival sac of the operators.

Air Microbiology↗
PubMed2001

Computer-assisted education for critical care nurses.

Technology is changing rapidly and health care is just beinnng to see the wave of technological advances. Computer-assisted educational software is available for many topics and in many media. Educators and learners need to explore these media and determine how they can best fit into a total learning experience. Computers should be used to enhance education and training, rather than replace the human instructor. The latest software and hardware are interesting to learners, but technology needs to be weighed along with outcomes of education. Over the next 10 years, many of the materials we use today for critical care education will be replaced with more advanced technologies. Subject matter experts should work with computer experts to design and improve computer-assisted technology. In addition, all educators should assess the return on investment of these newer technologies before embracing them.

Attitude to Computers↗
PubMed2004

Towards integration of computer games in interactive health education environments: understanding gameplay challenge, narrative and spectacle.

CONTEXT: There is an alarming progress in the health status of the young in western countries, and new methods and tools for behavioural health interventions are urgently called for. OBJECTIVE: To explore how computer game designs can be integrated in the development of Interactive Health Education Environments. DESIGN: Qualitative analyses of adolescents' experiences of playing an action-adventure computer game, using data from in-depth interviews. RESULTS: A model is presented, where the gameplaying experience is connected to four components of computer games. Playing computer games was found to mainly be motivated by the challenges and competition represented in the gameplay scripts. CONCLUSIONS: Interactive health education environments can be improved by implementing challenging gameplay scripts, spectacular technical features and narratives.

Adolescent↗
PubMed1983

Bibliographic control of medical illustrations--a case study in the development of a library subsystem: II. Project implementation.

This second part of a two-part paper describes how the University of California, San Francisco (UCSF) Library implemented a bibliographic control system for a medical illustrations collection. Discussed are the staffing of the project, the design of formats and computer programs, further design changes, the input process, quality evaluation of the illustrations, and production and distribution of the control products (printed indexes and microfiche replicas). The report ends with a note on the applicability of the UCSF system to other libraries, and some benefits of the project.

Abstracting and Indexing↗
PubMed1997

High coordination lattice models of protein structure, dynamics and thermodynamics.

A high coordination lattice discretization of protein conformational space is described. The model allows discrete representation of polypeptide chains of globular proteins and small macromolecular assemblies with an accuracy comparable to the accuracy of crystallographic structures. Knowledge based force field, that consists of sequence specific short range interactions, cooperative model of hydrogen bond network and tertiary one body, two body and multibody interactions, is outlined and discussed. A model of stochastic dynamics for these protein models is also described. The proposed method enables moderate resolution tertiary structure prediction of simple and small globular proteins. Its applicability in structure prediction increases significantly when evolutionary information is exploited or/and when sparse experimental data are available. The model responds correctly to sequence mutations and could be used at early stages of a computer aided protein design and protein redesign. Computational speed, associated with the discrete structure of the model, enables studies of the long time dynamics of polypeptides and proteins and quite detailed theoretical studies of thermodynamics of nontrivial protein models.

Amino Acid Sequence↗
PubMed2006

Assessment of a new multileaf collimator concept using GEANT4 Monte Carlo simulations.

The aim of the work was to investigate in advance the dosimetric properties of a new multileaf collimator (MLC) concept with the help of Monte Carlo (MC) simulations prior to the production of a prototype. The geometrical design of the MLC was implemented in the MC code GEANT4. For the simulation of a 6 MV treatment beam, an experimentally validated phase space and a virtual spatial Gaussian-shaped model placed in the origin were used. For the simulation of the geometry in GEANT4, the jaws and the two leaf packages were implemented with the help of computer-aided design data. First, transmission values for different tungsten alloys were extracted using the simulation codes GEANT4 and BEAMnrc and compared to experimental measurements. In a second step, high-resolution simulations were performed to detect the leakage at depth of maximum dose. The 20%-80% penumbra along the travel direction of the leaves was determined using 10 x 10 cm2 fields shifted along the x- and y-axis. The simulated results were compared with measured data. The simulation of the transmission values for different tungsten alloys showed a good agreement with the experimental measurements (within 2.0%). This enabled an accurate estimation of the attenuation coefficient for the various leaf materials. Simulations with varying width of the spatial Gaussian distribution showed that the leakage and the penumbra depend very much on this parameter: for instance, for widths of 2 and 4 mm, the interleaf leakage is below 0.3% and 0.75%, respectively. The results for the leakage and the penumbra (4.7+/-0.5 mm) are in good agreement with the measurements. This study showed that GEANT4 is appropriate for the investigation of the dosimetric properties of a multileaf collimator. In particular, a quantification of the leakage, the penumbra, and the tongue-and-groove effect and an evaluation of the influence of the beam parameters such as the width of the Gaussian distribution was possible.

Body Burden↗
PubMed2001

Three-dimensional computerized selection of hip prostheses in patients with congenital dislocated hips.

This study assessed the effectiveness of the combined use of computed tomography (CT) and computer-aided design (CAD) in the preoperative evaluation and implant selection in 20 patients (20 hips) with congenital dislocation of the hip who were scheduled to undergo total hip arthroplasty. Computerized selection of the femoral implant with optimum fit and fill was made after a three-dimensional reconstruction of the femoral canal using CT data and CAD. Implantation of all sizes of 5 noncemented and 2 cemented femoral implants was simulated using CATIA software (IBM, Kingstone, NY). When patients underwent surgery, 18 of 20 preselected prostheses agreed by type and size with the prostheses implanted. The remaining 2 preselected implants agreed by type only. In patients with dislocated and dysplastic hips, combined use of CT and CAD allows effective preoperative planning by providing the surgeon with vital information about the proximal femoral canal geometry and the possible femoral implant with optimum fit and fill to be used.

Aged↗
PubMed2006

A new twist for DNA.

A computer-aided design strategy allows scientists to 'staple' DNA molecules into a wide variety of two-dimensional shapes, generating precisely arranged scaffolds that could serve as promising platforms for nanoscale research applications.

Computer-Aided Design↗
PubMedDate not supplied

Accuracy assessment of image-guided implant surgery: an experimental study.

PURPOSE: To accurately accomplish the drilling of an implant socket, the use of image-guided navigation has become an option. The aim of this study was to evaluate the 3-dimensional (3D) accuracy of navigation-guided drilled holes. MATERIALS AND METHODS: Laboratory accuracy measurements were obtained on an acrylic resin model with standardized target holes drilled by a computerized numerical control machine. The model was scanned by a multislice computerized tomography scanner and registered with fiducial marker-based algorithms. Navigated drillings were performed using an optical navigation system based on passive marker technology. Coordinates of drilled holes were determined by a 3D-digitizer probe, and accuracy was assessed for all 5 degrees of freedom using a computer-aided design system (Pro/Engineer). RESULTS: A total of 240 drillings were evaluated. Mean registration error was 0.86 mm (SD 0.25 mm). Target point deviation between preplanned and actual drill starting point was 0.95 mm (SD 0.25 mm). The deviation in terms of full length was 0.97 mm (SD 0.34 mm), and mean angular deviation on the coronal and sagittal planes was 1.35 degrees (SD 0.42 degrees). DISCUSSION: The accuracy of image-guided navigation depends on imaging modalities, patient-to-image registration procedures, and instrument tracking. The technical accuracy and the navigation procedure, as evaluated in the study presented, seem to be of minor influence. CONCLUSION: The data obtained by this in vitro study demonstrate that the accuracy of navigation-based drilling may be sufficient for clinical practice, particularly in terms of the transferability of preplanned trajectories. However, in vivo clinical trials need to be performed to evaluate the clinical accuracy and treatment quality of navigation-guided interventions.

Acrylic Resins↗
PubMedDate not supplied

Reading the medical record. II. Design of a human-computer interface for basic reading of computerized medical records.

A user interface for reading the medical record was designed and implemented on a workstation with a 19-inch colour screen. The text is presented on imitations of paper-pages. The pages are organized in bundles which are dynamically connected to scrollable index lists. The turning of pages on the screen is the fundamental concept of the interface. A page can be turned by a mouse-click or by a circular mouse-movement. Elaborated feedback is given to the user in order to provide effortless orientation and navigation. The interface supports the basic ways of use identified in our analyses of reading habits. It also enables human perceptual and cognitive skills to be used. It seems very easy to learn and efficient in use.

Cues↗
PubMed1999

Experimental computer-assisted alloplastic sandwich augmentation of the atrophic mandible.

PURPOSE: This study evaluated the effectiveness of a technique that combined computer-aided surgery with alloplastic augmentation and implant-borne prosthodontic rehabilitation of the atrophic mandible. MATERIALS AND METHODS: Computed tomographic (CT) data from an atrophic cadaver mandible were transferred to a computer-aided design (CAD) system that prepared an anterior sandwich osteotomy. The cranial segment was moved upward and backward to provide an ideal alveolar relationship, and the geometry of the intermediate space was used to design a titanium implant. Furthermore, a surgical template was derived for the osteotomies, and insertion of dental implants was planned to stabilize both the transposed bone and the intermediate implant on the bony base. An identical implant for augmentation was also fabricated from poly-D,L-lactide in a mold as a possible resorbable carrier for osteoinductive proteins. RESULTS: The experimental surgery was successfully performed with maximum precision on the dried mandible. The fabrication of an implant made out of poly-D,L-lactide for the same purpose was also possible. CONCLUSIONS: This preliminary experiment showed that it is possible to use CAD/computer-aided manufacturing (CAM) technology to prepare a prefabricated template and a corresponding titanium implant for mandibular augmentation with a high degree of exactness. Dental implants could be planned and integrated in this procedure as well. The fabrication of a mold using this method also provided the opportunity to give a complex shape to possible carriers of osteoinductive substances.

Alveolar Bone Loss↗