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At least 1,405 records · Page 78Linked to original sources
PubMed1999

Computer-aided craniofacial surgical planning implemented in CAD software.

Accurate presurgical planning is imperative for successful cranial surgery. This article introduces a simulation program developed in a computer-aided design environment. The neurocranium is introduced as a mathematical surface, since this is the part on which the actual operation will be performed. The viscerocranium, which serves as reference, is visualized using small triangular surfaces. The development of the program commenced with a classification of the different surgical techniques mentioned in the literature into six basic actions. The use of mathematically described surfaces has the advantage that the program can simulate actions which change the shape of a surface and perform an on-line estimation of the fracture risk during bending. Three-point bending tests were carried out to provide the necessary data to perform the mathematical check, as these data are not available in the literature. A database with reference distances was introduced to guide the surgeon to obtain the best possible results. During one clinical trial, the computer was taken into the operating room so that the surgical plan developed with the simulation program could be applied to the actual operation.

Brain↗
PubMed2005

Designing and testing a computer-based screening system for transfusion-related acute lung injury.

Computer-based systems can detect underreported adverse events. We hypothesized that a system could be designed to detect potential or unreported cases of transfusion-related acute lung injury (TRALI). We developed and tested a computer screening system using retrospective computer blood gas data after transfusions during a 45-day period at a tertiary care academic hospital. The program identified cases of posttransfusion hypoxemia. Medical records of identified cases were reviewed to diagnose TRALI. During the 45-day period, 820 patients received 6,888 blood products. Seven cases of TRALI were diagnosed, whereas only 2 had been reported. The system had 99% accuracy and 26% positive predictive value for detecting potential TRALI. Computer screening finds more cases of TRALI than are reported voluntarily, and a prospective study using this system is feasible and needed to validate this method of detecting this important adverse transfusion reaction.

Adolescent↗
PubMed2001

Simulation of the BP-80 blood pump.

In this study, computational fluid dynamics (CFD) analysis was applied to investigate the flow within a commercially available Biopump, BP-80 (Medtronic, Minneapolis, MN, U.S.A.). The Biopump was selected because, for this purpose, a great number of experimental hemolysis data is available. The process of geometry representation and grid generation was focused on, due to its high impact on the numerical results. This process incorporated the use of three commercially available software packages for three-dimensional computer-aided design (3D-CAD), grid generation, and solving, respectively. For the purpose of validation, the head/flow characteristics of the pump were experimentally obtained and compared to the computed data. The results showed a rough agreement between CFD data and experimental data. Further investigations should cover detailed shear stress analyses and computation of other hemolysis-related quantities.

Computer Simulation↗
PubMed1999

Collaborative prototyping approaches for ICU decision aid design.

When computer-based aids do not support the human users' decision-making strategies or anticipate the organizational impacts of technological change, advances in information technology may degrade rather than enhance decision-making performance. Such failures suggest the design of human-computer cooperation for problem solving and decision-making must be driven by human cognitive and organizational process requirements rather than computer technology. Decision- and user-centered development techniques involve domain experts and end-users in the earliest phases of design to evolve an understanding of requirements through iterative prototyping. This paper presents a collaborative approach to cognitive systems engineering applied to developing a clinical aid to assist respiratory care in the surgical ICU.

Computer Systems↗
PubMed1999

Stereoscopic lithography: customized titanium implants in orofacial reconstruction. A new surgical technique without flap cover.

Head and neck surgery may involve complex methods of composite reconstruction that do not replicate the volume and contour of the normal anatomy. 'Functional' reconstruction implies replication of the normal volume and contour of both hard and soft tissues to produce normal form and function of the face, mouth and jaws. Techniques such as stereoscopic lithography and computer-assisted design, and-manufacture (CAD-CAM) have been successfully used with computer-numerized control (CNC) milling to manufacture customized titanium implants for single-stage reconstruction of the maxilla, hemimandible and dentition without the use of composite flap cover after the removal of tumours. Reduction in theatre time and personnel, less need for intensive care, and earlier discharge from hospital, indicate possible savings of Pound Sterling 17,000-Pound Sterling 19,000 per patient. There are implications for surgery in general, and further research and development is advocated.

Adult↗
PubMed2001

Computer-assisted prefabrication of individual craniofacial implants.

Historically, reconstruction of the skull with intraoperatively modeled implants has been restricted severely by limitations in implant material, unpredictable aesthetic results, prolonged OR time, and indirect techniques that cause decreased precision and increased expense. This article discusses modern computer-aided design and manufacturing systems that allow for direct preoperative fabrication of implants out of pure titanium with a variety of enhanced construction details. Between 1997 and 1999, 135 cranial and craniofacial reconstructions with defects measuring up to 22 cm were performed using this technique at 25 health care centers in Europe. The results obtained in these patients were predictable and constant and demonstrated dramatically reduced OR times.

Adult↗
PubMedDate not supplied

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment.

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

Cochlear Implants↗
PubMed1996

Application of computational fluid dynamics techniques to blood pumps.

Present-day computational fluid dynamics (CFD) techniques can be used to analyze the behavior of fluid flow in a variety of pumps. CFD can be a powerful tool during the design stage for rapid virtual prototyping of different designs, analyzing performance parameters, and making design improvements. Computational flow solutions provide information such as the location and size of stagnation zones and the local shear rate. These parameters can be correlated to the extent of hemolysis and thrombus formation and are critical to the success of a blood pump. CFD-ACE, an advanced commercial CFD code developed by CFD Research Corporation, has been applied to fluid flows in rotary machines, such as axial flow pumps and inducers. Preprocessing and postprocessing tools for efficient grid generation and advanced graphical flow visualization are integrated seamlessly with CFD-ACE. The code has structured multiblock grid capability, non-Newtonian fluid treatment, a variety of turbulence models, and an Eulerian-Langrangian particle tracking model. CFD-ACE has been used successfully to study the flow characteristics in an axial flow blood pump. An unstructured flow solver that greatly automates the process of grid generation and speeds up the flow simulation is under development.

Biocompatible Materials↗
PubMed2003

Anatomically shaped osteochondral constructs for articular cartilage repair.

Few successful treatment modalities exist for surface-wide, full-thickness lesions of articular cartilage. Functional tissue engineering offers a great potential for the clinical management of such lesions. Our long-term hypothesis is that anatomically shaped tissue constructs of entire articular layers can be engineered in vitro on a bony substrate, for subsequent implantation. To determine the feasibility, this study investigated the development of bilayered scaffolds of chondrocyte-seeded agarose on natural trabecular bone. In a series of three experiments, bovine chondrocytes were seeded in (1) cylindrical bilayered constructs of agarose and bovine trabecular bone, 0.53 cm2 in surface area and 3.2 mm thick, and were cultured for up to 6 weeks; (2) chondrocyte-seeded anatomically shaped agarose constructs reproducing the human patellar articular layer (area=11.7 cm2, mean thickness=3.4 mm), cultured for up to 6 weeks; and (3) chondrocyte-seeded anatomically shaped agarose constructs of the patella (same as above) integrated into a corresponding anatomically shaped trabecular bone substrate, cultured for up to 2 weeks. Articular layer geometry, previously acquired from human cadaver joints, was used in conjunction with computer-aided design and manufacturing technology to create these anatomically accurate molds. In all experiments, chondrocytes remained viable over the entire culture period, with the agarose maintaining its shape while remaining firmly attached to the underlying bony substrate (when present). With culture time, the constructs exhibited positive type II collagen staining as well as increased matrix elaboration (Safranin O staining for glycosaminoglycans) and material properties (Young's modulus and aggregate modulus). Despite the use of relatively large agarose constructs partially integrated with trabecular bone, no adverse diffusion limitation effects were observed. Anatomically shaped constructs on a bony substrate may represent a new paradigm in the design of a functional articular cartilage tissue replacement.

Animals↗
PubMed1996

Evaluation of gene structure prediction programs.

We evaluate a number of computer programs designed to predict the structure of protein coding genes in genomic DNA sequences. Computational gene identification is set to play an increasingly important role in the development of the genome projects, as emphasis turns from mapping to large-scale sequencing. The evaluation presented here serves both to assess the current status of the problem and to identify the most promising approaches to ensure further progress. The programs analyzed were uniformly tested on a large set of vertebrate sequences with simple gene structure, and several measures of predictive accuracy were computed at the nucleotide, exon, and protein product levels. The results indicated that the predictive accuracy of the programs analyzed was lower than originally found. The accuracy was even lower when considering only those sequences that had recently been entered and that did not show any similarity to previously entered sequences. This indicates that the programs are overly dependent on the particularities of the examples they learn from. For most of the programs, accuracy in this test set ranged from 0.60 to 0.70 as measured by the Correlation Coefficient (where 1.0 corresponds to a perfect prediction and 0.0 is the value expected for a random prediction), and the average percentage of exons exactly identified was less than 50%. Only those programs including protein sequence database searches showed substantially greater accuracy. The accuracy of the programs was severely affected by relatively high rates of sequence errors. Since the set on which the programs were tested included only relatively short sequences with simple gene structure, the accuracy of the programs is likely to be even lower when used for large uncharacterized genomic sequences with complex structure. While in such cases, programs currently available may still be of great use in pinpointing the regions likely to contain exons, they are far from being powerful enough to elucidate its genomic structure completely.

Alternative Splicing↗
PubMed1978

Computer-assisted review of digoxin therapy in the elderly.

Current practice with digoxin was assessed in a group of 42 elderly patients by comparing plasma digoxin concentrations attained on previously established maintenance doses with those generated by a computer programme designed to calculate dosage schedules to suit individual patients. Discrepancies between measured and computed plasma levels and between established and computed doses dictated withdrawal of the drug or revision of dosage in 26 patients (62%), with obvious clinical benefit. An important determinant of dosage was renal function; reduction in creatinine clearance provided good evidence for the loss of ability of the elderly kidney to eliminate digoxin. Simple bedside methods are available which permit a reliable estimate of creatinine clearance without a 24-hour urine collection, provoding a rational basis for the choice of digoxin dosage in the elderly.

Aged↗
PubMed1984

The pharmacy computer system at The Ohio State University hospitals.

The pharmacy computer system designed, developed, and implemented at The Ohio State University Hospitals is described. The computer system was developed to make more efficient use of hospital facilities and professional staff time. The pharmacy system operates on the mainframe hospital system using computer terminals with light-pen and keyboard access. Current online applications include order entry, patient profiles, pharmacokinetic calculations, and preparation of unit dose cart fill lists. Batch processing functions include drug-use review, drug-drug interactions, and financial management reports. Approximately 95% of unit dose orders and 20% of i.v. orders are conditionally entered by pharmacy technicians for subsequent verification by pharmacists. The system saves considerable staff time in the i.v. admixture and billing areas and has relieved pharmacists from performing many clerical and repetitive tasks. Disadvantages of the system include (1) its dependence on another department for patient admission, transfer, and discharge information and (2) delays in obtaining approval for program modifications and new applications. The advantages of the pharmacy computer system lie in its ability to access information from other computerized databases in the hospital. Future modifications and enhancements to the system are discussed.

Computers↗
PubMed2003

Instrumental functional diagnostics with the ROSY simulator.

The ROSY robot system has been developed to simulate movements of the jaw under stepper motor control. The areas of indication comprise functional diagnostics and production of designed occlusal splints. Moreover, this device can also be extended for use in other areas. The computer-assisted design of OR templates has become possible. The simulator also permits the production of implant-borne restorations with optimum implant loading.

Computer Simulation↗
PubMedDate not supplied

Applying ergonomics to nurse computer workstations: review and recommendations.

Nursing is associated with high rates of musculoskeletal disorders from patient handling, and nurses are at high risk for developing cumulative trauma disorders, which can result from computer usage. Although there are many benefits to using computers in the workplace, nurses need to incorporate ergonomic factors into work settings to promote safe workplace environments. This article reviews recent literature about computer workstation ergonomics, discusses related policies, and makes recommendations about computer workstation design and related research in nursing workplace settings.

Computer Terminals↗
PubMed2005

Leaflet geometry extraction and parametric representation of a pericardial artificial heart valve.

Reverse engineering technology was used to reconstruct the complex leaflet geometry of a commercial pericardial valve in our study. Results show that the three-dimensional computer-aided design model of the leaflet surface can be rendered by fitting the surface either to cloud points or by a group of B-splines fitted to a set of cloud points that had been obtained by the process of laser-scanning digitizing. However, an acceptable smooth surface is usually not guaranteed and additional manipulation is required. An alternative method is introduced in this paper, which involves the fitting of an equation to the leaflet geometry to create a smooth surface. The geometrical profile of a pericardial artificial heart valve was scanned using a laser digitizing system. The leaflet profile is represented as a set of cloud points. A quadric surface is fitted to a set of unique points, which were located on the set of cloud points. A mathematical equation is obtained by solving a least-squares fit. The geometry of the fitted leaflet surface has been proven to be closely represented by an elliptical hyperboloid. The quadratic equations of the leaflet curvatures, calculated along both the circumferential and the radial directions, resulted in simple hyperbolic curvatures. The advantages of using elliptical hyperboloid geometry for the leaflet surface are discussed and compared with other types of conicoid geometries. The concepts of parametric representation of the leaflet geometry and parametric design for leaflets are discussed. A smooth surface without inflection points and with an adjustable surface area suitable for a series of stent sizes with incremented diameters is created by this method of a single parametric design. Finally, a generic method to apply the geometry extraction and parametric representation to most pericardial heart valve prostheses was discussed. The application to valves with natural shape was introduced, challenges were identified, and a technical solution was proposed.

Algorithms↗
PubMed2003

Stereolithographic surgical templates for placement of dental implants in complex cases.

In recent years, dental implant rehabilitation has faced demands from prosthetic and esthetic arenas that call for increasingly ideal outcomes, which require precise surgical planning and placement. Anatomic limitations and bone quantity and quality can now be evaluated using more sophisticated radiographic techniques, although transferring this information to the surgical phase has been at best a difficult task. Recently, computer-aided design and manufacturing have made it possible to use data from computerized tomography to not only plan implant rehabilitation, but also to transfer this information to the surgery. One of these techniques uses stereolithography, a laser-driven polymerization process that fabricates an anatomic model and surgical templates. This novel approach is illustrated with two advanced cases, demonstrating that the technique not only allows for the precise translation of the treatment plan directly to the surgical field, but also offers many significant benefits over traditional procedures.

Bone Transplantation↗
PubMed2006

Tailor-made tricalcium phosphate bone implant directly fabricated by a three-dimensional ink-jet printer.

Rapid prototyping (RP) is a molding technique that builds a three-dimensional (3D) model from computer-aided design (CAD) data. We fabricated new tailor-made bone implants (TIs) from alpha-tricalcium phosphate powder using an RP ink-jet printer based on computed tomography (CT) data, and evaluated their safety and efficacy. CT data of the skulls of seven beagle dogs were obtained and converted to CAD data, and bone defects were virtually made in the skull bilaterally. TIs were designed to fit the defects and were fabricated using the 3D ink-jet printer with six horizontal cylindrical holes running through the implants, designed for possible facilitation of vascular invasion and bone regeneration. As a control, hydroxyapatite implants (HIs) were cut manually from porous hydroxyapatite blocks. Then, craniectomy was performed to create real skull defects, and TIs and HIs were implanted. After implantation, CT was performed regularly, and the animals were euthanized at 24 weeks. No major side effects were observed. CT analysis showed narrowing of the cylindrical holes; bony bridging between the implants and the temporal bone was observed only for TIs. Histological analysis revealed substantial new bone formation inside the cylindrical holes in the TIs, while mainly connective tissues invaded the porous structures in HIs. Bone marrow was observed only in TIs. Osteoclasts were seen to resorb regenerated bone from inside the cylindrical holes and to invade and probably resorb the TIs. These data suggest that TIs are a safe and effective bone substitute, possessing osteoconductivity comparable with that of HIs.

Animals↗
PubMed1994

Morphology predicts rapid growth of small abdominal aortic aneurysms.

This study evaluated CT scans of small abdominal aortic aneurysms (AAAs) (< 5 cm) to assess anatomic features associated with rapid expansion. Serial CT scans obtained at least 10 months apart (mean 15 months) from patients with small AAAs were reviewed. Each cross-sectional image of the AAAs was analyzed using a computer-assisted design program. The circumference of the AAA in each CT image was divided into eight equal arcs, from which the apparent radius of curvature (Rc) for each segment was calculated. Flattening of the wall curvature results in an increased segmental Rc. The CT scans of nine patients with expanding AAAs (expansion > or = 0.5 cm/yr) were compared to those of 10 patients with stable AAAs (expansion < or = 0.2 cm/yr). To adjust for differences in AAA size, the Rc for each segment was normalized by dividing each individual Rc by the average of the eight Rcs (RcAvg) calculated for that cross-sectional CT image. Analysis of variance showed that the left posterolateral segments in expanding AAAs had larger Rc/RcAvg ratios than those segments in stable AAAs (1.14 +/- 0.19 vs. 0.80 +/- 0.09, p < 0.02). Laplace's law indicates that the left posterolateral segment in AAAs that grow more rapidly is subjected to greater wall tension. Flattening in the curvature of the left posterolateral wall segment was significantly associated with an increased rate of expansion in small AAAs. This finding, readily derived from standard CT scan images, may predict which small AAAs are more prone to rapid expansion.

Aortic Aneurysm, Abdominal↗