Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “computational design”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed2006

3D surface accuracy of CAD generated skull defect contour.

The creation of a satisfactory cosmetic outcome in the repair of cranial defects relies on manual skill. However, computer aided design is gaining acceptance in the creation of custom cranial implants. The purpose of this work is to demonstrate the accuracy of a CAD generated skull defect contours using 3D difference maps. 3D multi-slice CT scanning was carried out on a life size plastic skull. Surface models were generated of the original skull and of temporofrontal and parietal defects. Surface contours were interpolated towards the centre of the defect from the edges where it was blended. The CAD contour deviation ranged from 0.0 mm to 2.0 mm with 80% of the total defect area less than 0.66 mm as measured by difference maps. CAD techniques can be used to produce contours for the repair of cranial defects with minimum deviation from the original skull contour. This enables accurate design and production of cranial implants.

Computer-Aided Design↗
PubMed1994

CAD-CAM ceramic inlays and onlays: using an indirect technique.

A time-sharing technique for a CAD-CAM unit can avoid scheduling difficulties and lengthy appointments. Dentists can also share the cost of expensive equipment and involve staff in learning the steps of this computer-aided design and manufacture.

Cementation↗
PubMed1996

Development of an anthropometric database for Hong Kong Chinese CAD operators.

With the increasing popularity of using computer-aided design (CAD) in Hong Kong, it is time to look into the design of a suitable workplace for the CAD operators working in the industries. This can be achieved by applying anthropometric data into the design for enhancing performance and reducing musculoskeletal problems. In order to avoid any mismatches in anthropometric dimensions, which is believed to be one of the main causes of fatigue and occupational illness among workers, in the workplace design for them, eleven relevant body dimensions from a group of 150 Hong Kong male adults with ages ranging from 18 to 28 years were collected and analyzed to develop a computerized anthropometric database for Hong Kong CAD operators. The eleven anthropometric dimensions measured were: shoulder rest height, elbow-fingertip length, shoulder breadth, hip breadth, sitting eye height, elbow rest height, third lumbar disc-pan length, thigh clearance height, popliteal height, buttock-popliteal length, and stature. The computerized database can provide some useful statistics such as mean, standard deviation and relevant percentiles of all the measured dimensions. With the aid of these statistics, a new workplace for CAD operators was designed which improved performance substantially.

Adolescent↗
PubMed2002

Computer-assisted preoperative planning of a novel design of total ankle replacement.

Computer-assisted preoperative planning are particularly sought for enhancing surgical implantation and improving clinical outcome of ankle joint replacement arthroplasty. A planning tool was designed to enhance the surgical implantation of a novel ligament-compatible three-component prosthesis. The tool includes a geometric and mechanical model of the ankle complex. The geometry of the articular surfaces and of main ligaments is defined from digitisation on a scanned lateral radiographs of the joint. From the expected movement arc and from component dimensions, a mechanical model of the ligaments is used to select the optimal size and the position the three prosthesis components. The planning is based on the minimisation of ligament change in length and of bone stock to be removed. The main output report is a detailed picture of the replaced ankle with indications of component locations and quantitative measure of bone cuts. An advanced report also superimposes the resulting prediction of prosthesis component kinematics at the replaced joint to the original radiographs.

Ankle↗
PubMed2006

[3D-data acquisition of partially edentulous cast using grating projection method].

OBJECTIVE: A method for 3D-data acquisition of partially edentulous cast was introduced to lay the foundation for reconstructing 3D digital model of a partially edentulous cast and studying computer aided design (CAD) to a removable partial denture framework. METHODS: Using projection system controlled by a computer, four frames of sinusoidal fringe pattern at pi/2 intervals were projected onto the surface of partially edentulous cast consecutively within 0.4 second. Deformed fringe patterns modulated by the surface height of the cast were recorded by a digital camera. The phase value with the height information was demodulated with phase-shifting method. The transition from the unwrapped phase to the height of the points on the cast was performed with triangulation method. The multiview 3D data was integrated automatically to obtain the complete 3D profile data and the 3D digital model of the partially edentulous cast was reconstructed. RESULTS: Dense and complete points-cloud data was achieved without scanning blind zone basically. The anatomic structure of reconstructed 3D digital model was sharp and clear. CONCLUSION: As an alternative for acquiring 3D data of partially edentulous cast, this method presented here with high precision and high speed meets the need for the subsequent 3D design to removable partial denture framework.

Computer-Aided Design↗
PubMed2002

[Computer-controlled isolated kidney hypothermic perfusion system].

OBJECTIVE: To evaluate at the laboratory a self-designed computer-controlled kidney perfusion system. A vacuum powered tubular pump with active valves developed by our group is used. This pump is able to produce a flow and pressure patterns very similar to the pulse wave in the human circulatory system. BASIC PROCEDURES: This is an experimental study performed with mini-pig kidneys. After transperitoneal bilateral nephrectomy, both organs are sorted either to immediate perfusion or to perfusion after a period of 24 hours of cold storage in Eurocollins solution. The system is able to record continuously perfusion pressure, flow and intrarenal resistance. RESULTS: A progressive decrease in renal vascular resistance along with an increase in the flow value were observed during the procedures. These dynamic changes become evident both in immediate and deferred renal perfusions. CONCLUSIONS: Computer-controlled kidney perfusion system provide us the opportunity of recording in real time renal microcirculatory state modifications during a perfusion. Vascular system seems to be actively modified by the perfusion. This fact should be researched in the next future.

Animals↗
PubMedDate not supplied

Development of a custom designed TAH using rapid prototyping.

The failure of the orthotopic implantation of a totally implantable artificial heart (TAH) was due mainly to anatomic mismatches in the conduits of the conventional TAH system. To overcome this anatomic incompatibility, a custom design and fabrication process was designed using the rapid prototyping (RP) technique. After three dimensional reconstruction of magnetic resonance imaging of the thoracic cavity and vascular remnants of the recipient, study of anatomic fit was done using the reconstructed thoracic model and three dimensional computer aided design (CAD) model. The direction of the inflow and outflow conduits of the blood sac was changed with a Unigraphics CAD. The RP model of the designed chamber was fabricated and examined for anatomic compatibility. Through this approach, the minute directional mismatch of the inflow and outflow conduits was improved. Thus, a new custom designed moving actuator Korean TAH with CAD and RP techniques was developed.

Biomedical Engineering↗
PubMedDate not supplied

Development of a simulator for endovascular repair of abdominal aortic aneurysms.

The design and development of a simulator for endovascular repair of abdominal aortic aneurysm (AAA) is described. The simulator consists of an interchangeable model of a human AAA based on computed tomography data and is produced by means of computer-aided design and manufacture (CAD/CAM) techniques. The model has renal, iliac, and femoral arteries, and is perfused with a temperature controlled blood-analog fluid under simulated physiological flow conditions. "Fluoroscopic imaging" is simulated by a computerized imaging system that uses visible light. A movable video camera relays images in the antero-posterior and lateral planes of the AAA to a monitor. The imaging system allows "arteriography" and "road-mapping" to be performed so as to facilitate accurate deployment of endovascular stent-grafts. The system has been used for teaching and demonstrating endovascular techniques to clinicians, as well as the evaluation of new stent-graft devices. Its successful incorporation into endovascular workshops has demonstrated its role in the training of clinicians in endovascular repair of AAA.

Angiography↗
PubMed2004

[Design and experimental study of computer-assisted orthopaedic system for distal locking of intramedullary nails].

OBJECTIVE: To test the safety and accuracy of the computer-assisted orthopaedic system for distal locking of intramedullary nails and apply it to internal fixation with intramedullary nails in the lower limb. METHODS: According to the theory of mechanical arms stereotactic localization in computer-assisted orthopaedic surgery (CAOS), we design a CAOS system for distal locking of intramedullary nails. The system comprised 2 independent modules: computer-assisted imaging and registration workstation; mechanical stereotactic framework. Ten plastic tibia models, 20 plastic femur models (Synbone AG, Malans, Switzerland) and 6 human cadaver lower limbs were randomly divided into 2 groups undergoing internal fixation with intramedullary nails (Orthofix, Germany). The first group (CAOS group with 5 plastic tibia models, 10 plastic femur models, 6 human cadaver tibia, 6 human cadaver femur; each nail had 2 holes, and 2 distal locking screws were inserted in each bone, which gave a total number of 54 holes) used a computer-assisted orthopaedic system, the second group (CONTROL GROUP is the same as CAOS group) used Orthofix mechanical targeting device for distal locking. Comparison between 2 groups was made in radiation exposure time, operating time, percentage of correctly placed screws. RESULTS: CAOS group: operating time was (4.44 +/- 2.99) min; radiation exposure time was (1.16 +/- 0.38) min; correctly placed screws rate was (100 +/- 0)%. CONTROL GROUP: operating time was (10.42 +/- 4.18) min; radiation exposure time was (4.71 +/- 3.86) min; correctly placed screws rate was (94.44 +/- 0.36)%. Operating time and radiation exposure time in CAOS group were significantly shorter than those in control group (P < 0.05), no differences were found between 2 groups in relation to the percentage of correctly placed screws. CONCLUSIONS: By using CAOS system for distal locking of intramedullary nails, the locking holes can be drilled accurately and safely. Radiation exposure significantly reduced.

Cadaver↗
PubMed2005

Anterior dual rod instrumentation in idiopathic thoracic scoliosis: a computed tomography analysis of screw placement relative to the aorta and the spinal canal.

STUDY DESIGN: Axial computed tomography scans (CT) in 20 consecutive patients with idiopathic right thoracic scoliosis and anterior correction and fusion with a dual rod dual screw system. OBJECTIVES: CT evaluation of screw position in anterior dual rod instrumentation relative to the aorta and the spinal canal. SUMMARY OF BACKGROUND DATA: In anterior scoliosis surgery, bicortical screw purchase is used to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. Data on the accuracy of dual screw instrumentation in thoracic scoliosis are missing. METHODS: All 20 patients underwent an identical anterior surgical technique with double thoracotomy approach and dual rod instrumentation of the primary curve. Postoperative sequential CT scans were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, distance from the aorta to the closest point of the vertebral body cortex, distance between the tip of the screws and the aorta, distance between the screw and the spinal canal, and the amount of contralateral screw penetration. A total amount of 226 screws were evaluated. RESULTS: All screws were placed correctly without any critical proximity to the aorta or spinal canal. A total of 198 of 226 screws (88%) had a bicortical purchase. Thirteen screw tips (5.8%) were within 1 to 3 mm proximity to the aorta. All other screws were more than 3 mm distant from the aorta. The closest proximity of the screw tips to the thoracic aorta was found at the upper end vertebrae (T5, T6, or T7). There were no screws perforating the spinal canal. CONCLUSION: Anterior instrumentation and correction of thoracic scoliosis with a dual rod dual screw system enable a correct and safe screw placement using a standard open approach. Excessive bicortical screw perforation should be avoided in order not to endanger the thoracic aorta.

Adolescent↗
PubMed1992

Pediatric craniofacial surgery: comparison of milling and stereolithography for 3D model manufacturing.

To improve the planning phase for pediatric craniofacial surgery, 3D reconstructions of CT image series were performed on a personal computer. For construction of true models of the surgical site, two concepts were pursued. CT image data of six patients were used for model manufacturing by a conventional 2 1/2 axis milling system. The material used was polyurethane foam. Alternatively, in one patient a stereolithography was produced on the basis of the 3D reconstructed CT data. This new manufacturing device uses a photocurable monomer, hardened by a UV-laser. The spatial resolution of the system is about 0.1 mm. 3D-reconstructions were performed on a personal computer. Data were then transferred into a surface oriented structure to control a stereolithographic modeling device. Time for transfer was 70 min. The production of the modelled cranium took a total time of 59 h. Accuracy was found to be much higher in stereolithography than in milled models. The model served for surgical planning. The long time for production was caused by inadequate computer capacities, which are configured for much less complex objects in computer aided design. Furthermore the programs for the machine control are optimized for technical purposes. If these conditions are improved, stereolithography could be an attractive alternative to milling of medical models.

Child↗
PubMed2005

[Fabrication of 3-dimensional skull model with rapid prototyping technique and its primary application in repairing one case of cranio-maxillo-facial trauma].

OBJECTIVE: To investigate the methods of establishing 3-dimensional skull model using electron beam CT (EBCT) data rapid prototyping technique, and to discuss its application in repairing cranio-maxillo-facial trauma. METHODS: The data were obtained by EBCT continuous volumetric scanning with 1.0 mm slice at thickness. The data were transferred to work-station for 3-dimensional surface reconstruction by computer-aided design software and the images were saved as STL file. The data can be used to control a laser rapid-prototyping device (AFS-320QZ) to construct geometric model. The material for the model construction is a kind of laser-sensitive resin power, which will become a mass when scanned by laser beam. The design and simulation of operation can be done on the model. The image data were transferred to the device slice by slice. Thus a geometric model is constructed according to the image data by repeating this process. Preoperative analysis, surgery simulation and implant of bone defect could be done on this computer-aided manufactured 3D model. One case of cranio-maxillo-facial bone defect resulting from trauma was reconstructed with this method. The EBCT scanning showed that the defect area was 4 cm x 6 cm. The nose was flat and deviated to left. RESULTS: The 3-dimensional skull was reconstructed with EBCT data and rapid prototyping technique. The model can display the structure of 3-dimensional anatomy and their relationship. The prefabricated implant by 3-dimensional model was well-matched with defect. The deformities of flat and deviated nose were corrected. The clinical result was satisfactory after a follow-up of 17 months. CONCLUSION: The 3-dimensional model of skull can replicate the prototype of disease and play an important role in the diagnosis and simulation of operation for repairing cranio-maxillo-facial trauma.

Adult↗
PubMed1997

Myocardial O2 balance during fluid resuscitation in uncontrolled hemorrhage: computer model.

OBJECTIVE: To study myocardial oxygen balance during fluid resuscitation for uncontrolled hemorrhage. DESIGN: A computer simulation. MATERIALS AND METHODS: A mathematical model of the cardio-vascular system was used to simulate uncontrolled hemorrhage with and without fluid replacement. The parameters of initial bleeding rates, fluid replacement, and time intervals were selected to approximate typical values encountered in an urban emergency medical services system. The model was used to calculate myocardial oxygen supply and demand, and the time from injury to myocardial oxygen deficit was calculated for each fluid regimen. MAIN RESULTS: The model predicts an exponential decline in bleeding rate when no fluids are administered. Optimal fluid infusion rate was predicted as a function of initial bleeding rate. The time to a negative myocardial oxygen balance was shorter when a fluid bolus (100 mL/min or more) was given compared with no fluid administration. CONCLUSIONS: For uncontrolled hemorrhage at initial bleeding rates of 100 mL/min or more, the time interval from injury to cardiac oxygen deficit is inversely related to the infusion rate. A detailed study of the myocardial oxygen balance provides a pathophysiologic rationale for fluid restriction in the initial management of uncontrolled hemorrhage.

Computer Simulation↗
PubMed2005

Combining structure-based drug design and pharmacophores.

Development towards integrated computer-aided drug design methodologies is presented by utilising crystal structure complexes to produce structure-based pharmacophores. These novel pharmacophores represent the ligand features that are involved in interactions with the target protein, as well as the space around the ligand occupied by the protein. The protein-ligand complexes can also yield information about all interactions that ligands could potentially form with the binding site, as well as about the size of the binding cavity. Together, these describe a 'superligand', which can also be viewed as a pharmacophore. Various types of novel pharmacophores are discussed and compared, using HIV-1 reverse transcriptase (RT) as the target protein, and their application in database searching is presented.

Binding Sites↗
PubMed2005

Biogeneric tooth: a new mathematical representation for tooth morphology in lower first molars.

A mathematical representation of tooth morphology may help to improve and automate restorative computer-aided design processes, virtual dental education, and parametric morphology. However, to date, no quantitative formulation has been identified for the description of dental features. The aim of this study was to establish and to validate a mathematical process for describing the morphology of first lower molars. Stone replicas of 170 caries-free first lower molars from young patients were measured three-dimensionally with a resolution of about 100,000 points. First, the average tooth was computed, which captures the common features of the molar's surface quantitatively. For this, the crucial step was to establish a dense point-to-point correspondence between all teeth. The algorithm did not involve any prior knowledge about teeth. In a second step, principal component analysis was carried out. Repeated for 3 different reference teeth, the procedure yielded average teeth that were nearly independent of the reference (less than +/- 40 microm). Additionally, the results indicate that only a few principal components determine a high percentage of the three-dimensional shape variability of first lower molars (e.g. the first five principal components describe 52% of the total variance, the first 10 principal components 72% and the first 20 principal components 83%). With the novel approach presented in this paper, surfaces of teeth can be described efficiently in terms of only a few parameters. This mathematical representation is called the 'biogeneric tooth'.

Algorithms↗