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PubMed2002

Geometric analysis of selected press fit prosthetic systems for proximal humeral replacement.

The ability of a prosthetic system to replicate a wide range of normal anatomy appears dependent in part to its capacity to produce variable prosthetic geometries. Several modern designs have recently been developed in order to provide multiple prosthetic options. The purpose of this study was to compare the geometry of select press fit prosthetic systems in terms of their ability to match normal three-dimensional geometry of the proximal humerus. The anatomy of 60 humeral specimens from 30 cadavers known from CT data and computer-aided design (CAD) analysis was compared to a 1996 database of four conventional shoulder prosthetic systems (fixed inclination angle, one medial-lateral offset position per head) and one so-called anatomic system (variable inclination angles, multiple head offset positions). The prosthetic system with greatest geometric options allowed for a significantly better replication of the anatomy. Average displacement of the center of rotation was 2.1 mm compared to 9.7 mm for the other systems combined. Reduction in surface arc was 12 degrees compared to 32 degrees. The most problematic feature of conventional prosthetic systems in terms of replicating normal humeral anatomy is the gap created by the prosthetic collar and Morse taper.

Algorithms↗

PubMed2001

Design of inhibitors of Ras--Raf interaction using a computational combinatorial algorithm.

Drugs that inhibit important protein-protein interactions are hard to find either by screening or rational design, at least so far. Most drugs on the market that target proteins today are therefore aimed at well-defined binding pockets in proteins. While computer-aided design is widely used to facilitate the drug discovery process for binding pockets, its application to the design of inhibitors that target the protein surface initially seems to be limited because of the increased complexity of the task. Previously, we had started to develop a computational combinatorial design approach based on the well-known 'multiple copy simultaneous search' (MCSS) procedure to tackle this problem. In order to identify sequence patterns of potential inhibitor peptides, a three-step procedure is employed: first, using MCSS, the locations of specific functional groups on the protein surface are identified; second, after constructing the peptide main chain based on the location of favorite locations of N-methylacetamide groups, functional groups corresponding to amino acid side chains are selected and connected to the main chain C(alpha) atoms; finally, the peptides generated in the second step are aligned and probabilities of amino acids at each position are calculated from the alignment scheme. Sequence patterns of potential inhibitors are determined based on the propensities of amino acids at each C(alpha) position. Here we report the optimization of inhibitor peptides using the sequence patterns determined by our method. Several short peptides derived from our prediction inhibit the Ras--Raf association in vitro in ELISA competition assays, radioassays and biosensor-based assays, demonstrating the feasibility of our approach. Consequently, our method provides an important step towards the development of novel anti-Ras agents and the structure-based design of inhibitors of protein--protein interactions.

Algorithms↗

PubMed2006

Effect of keyswitch design of desktop and notebook keyboards related to key stiffness and typing force.

This study aimed to compare and analyse rubber-dome desktop, spring-column desktop and notebook keyboards in terms of key stiffness and fingertip typing force. The spring-column keyboard resulted in the highest mean peak contact force (0.86N), followed by the rubber dome desktop (0.68N) and the notebook (0.59N). All these differences were statistically significant. Likewise, the spring-column keyboard registered the highest fingertip typing force and the notebook keyboard the lowest. A comparison of forces showed the notebook (rubber dome) keyboard had the highest fingertip-to-peak contact force ratio (overstrike force), and the spring-column generated the least excess force (as a ratio of peak contact force). The results of this study could aid in optimizing computer key design that could possibly reduce subject discomfort and fatigue.

Adult↗

PubMed1997

Comparison of image processing techniques (magnetic resonance imaging, computed tomography scan and ultrasound) for 3D modeling and analysis of the human bones.

Magnetic resonance imaging (MRI), computed tomography scanning (CT scan), and ultrasound imaging techniques (UI) were used for data acquisition to construct/develop a 3D solid model of the human tibia, femur, and skull. CT scan was found to be an acceptable technique for cadavers. CT scans are harmful to the human body in large doses, while MRIs and ultrasound are known to be safe. However, MRIs form a better tool in performing this image generation task for living beings because of its high resolution capacity when compared with images obtained using ultrasound techniques. High resolution poses to be a very important factor, as the consideration of various material properties of the bones was part of the emphasis of this research. MRIs have the capacity of displaying a distinct boundary between the muscles and the bone, in addition to the boundary between the cortical and the cancellous region within the bone. Ultrasound was found to be the cheapest technique and gave reasonably good results for just the outside boundaries of the bone. The models of the human bones were generated on a Computer Aided Design (CAD) system. The cross-sections obtained from (MRI, CT, or UI) were scanned into the computer. Image processing software was used to detect the boundaries of the bones. A C + + program was used to read the coordinates of the edges and construct a B-spline curve on the CAD system. The curves were converted to a B-rep solid using skinning. The solid models were meshed, constrained, and material properties were assigned to different regions of the models for Finite Element Analysis (FEM).

Anatomy, Cross-Sectional↗

PubMed2005

3D models of blood flow in the cerebral vasculature.

The circle of Willis (CoW) is a ring-like arterial structure located in the base of the brain and is responsible for the distribution of oxygenated blood throughout the cerebral mass. To investigate the effects of the complex 3D geometry and anatomical variability of the CoW on the cerebral hemodynamics, a technique for generating physiologically accurate models of the CoW has been created using a combination of magnetic resonance data and computer-aided design software. A mathematical model of the body's cerebral autoregulation mechanism has been developed and numerous computational fluid dynamics simulations performed to model the hemodynamics in response to changes in afferent blood pressure. Three pathological conditions were explored, namely a complete CoW, a fetal P1 and a missing A1. The methodology of the cerebral hemodynamic modelling is proposed with the potential for future clinical application in mind, as a diagnostic tool.

Blood Flow Velocity↗

PubMedDate not supplied

Exhaustive de novo design of low-molecular-weight fragments against the ATP-binding site of DNA-gyrase.

We present a de novo design approach to generating small fragments in the DNA-gyrase ATP-binding site using the computational drug design platform SkelGen. We have generated an exhaustive number of structural possibilities, which were subsequently filtered for site complementarity and synthetic tractability. A number of known active fragments are found, but most of the species created are potentially novel and could be valuable for further elaboration and development into lead-like structures.

Adenosine Triphosphate↗

PubMed2004

Computer-aided anthropometry in the evaluation of dysmorphic children.

OBJECTIVE: Although anthropometry is widely regarded as the technique of choice for the evaluation of dysmorphic features among children, it is only rarely used in clinical practice. Possible reasons for this are the limited access of pediatricians to appropriate reference values and the time-consuming way measurements must be plotted onto growth charts. This article describes a computer program that overcomes these problems and greatly facilitates the use of anthropometric measurements in pediatric medicine. DESIGN: A computer program for PalmOS-based, handheld computers that compares entered anthropometric measurements with age- and gender-matched reference values was developed. The software is distributed free of charge and can be downloaded (www.medgen.unizh.ch/abase/). RESULTS: The ABase software contains age- and gender-matched reference values for 18 anthropometric measures frequently used for the evaluation of dysmorphic children. The proband's age is automatically calculated from the entered birth date and can be corrected for prematurity. Entered measurements are compared with the internal reference values; the results are displayed as percentile ranks or z scores and are plotted on digital growth charts. CONCLUSIONS: The presented software makes anthropometric reference values easily accessible on the ward or in the clinic and greatly reduces the time needed to plot the measurements onto growth charts. This should promote more widespread use of anthropometry in pediatric medicine.

Anthropometry↗

PubMed1997

Possibility of correcting image cytometric nuclear DNA (ploidy) measurements in tissue sections. Insights from computed corpuscle sectioning and the reference curve method.

OBJECTIVE: To describe, validate and apply a computer simulation of corpuscle sectioning to determine which assumptions are compatible with the possibility of correction. STUDY DESIGN: A computer program was written in PASCAL and run on a personal computer. RESULTS: Correction is practical in the case of spherical nuclei with homogeneous intranuclear DNA and a constant internuclear DNA concentration, even if section thickness is uneven or inaccurate. Correction is not possible in the case of marked nuclear ellipticity: mild cases are correctable, although subpopulations in a mixed-ploidy sample would not be distinguished. Correction is possible in the case of spherical (but not ellipsoidal) nuclei with a variable internuclear DNA concentration, and subpopulations in a mixed-ploidy sample would be distinguishable if sufficiently different. If the DNA is markedly concentrated in one part of the nucleus, overcorrection results. CONCLUSION: The results clarify the factors that limit correction of image cytometric measurements of ploidy in tissue sections. A new method of correcting ploidy measurements in tissue sections is usable.

Cell Nucleus↗

PubMed2001

Haptic force-feedback devices for the office computer: performance and musculoskeletal loading issues.

Pointing devices, essential input tools for the graphical user interface (GUI) of desktop computers, require precise motor control and dexterity to use. Haptic force-feedback devices provide the human operator with tactile cues, adding the sense of touch to existing visual and auditory interfaces. However, the performance enhancements, comfort, and possible musculoskeletal loading of using a force-feedback device in an office environment are unknown. Hypothesizing that the time to perform a task and the self-reported pain and discomfort of the task improve with the addition of force feedback, 26 people ranging in age from 22 to 44 years performed a point-and-click task 540 times with and without an attractive force field surrounding the desired target. The point-and-click movements were approximately 25% faster with the addition of force feedback (paired t-tests, p < 0.001). Perceived user discomfort and pain, as measured through a questionnaire, were also smaller with the addition of force feedback (p < 0.001). However, this difference decreased as additional distracting force fields were added to the task environment, simulating a more realistic work situation. These results suggest that for a given task, use of a force-feedback device improves performance, and potentially reduces musculoskeletal loading during mouse use. Actual or potential applications of this research include human-computer interface design, specifically that of the pointing device extensively used for the graphical user interface.

Adult↗

PubMed1999

Effect of keyboard keyswitch design on hand pain.

This randomized clinical trial evaluated the effects of keyboard keyswitch design on computer users with hand paresthesias. Twenty computer users were matched and randomly assigned to keyboard A (n = 10) or B (n = 10). The keyboards were of conventional layout and differed in keyswitch design. Various outcome measures were assessed during the 12 weeks of use. Subjects assigned keyboard A experienced a decrease in hand pain between weeks 6 and 12 when compared with keyboard B subjects (P = 0.05) and demonstrated an improvement in the Phalen test time (right hand, P = 0.006; left hand, P = 0.06). Keyboard assignment had no significant effect on change in hand function or median nerve latency. We conclude that use of keyboard A for 12 weeks led to a reduction in hand pain and an improved physical examination finding when compared with keyboard B. There was no corresponding improvement in hand function or median nerve latency.

Adult↗

PubMed1990

Computer-assisted preoperative planning (CAPP) in orthopaedic surgery.

Computer-assisted preoperative planning (CAPP) is a complex approach to planning a surgical treatment. It includes computer-assisted design (CAD) principles, expert knowledge utilization and facilities for decision making process support. The CAPP system uses actual patient data and calculates instructions in real dimensions for performing a particular operation on a particular patient. Our first CAPP application was preoperative planning of corrective osteotomy of a malunited fracture at the distal end of the radius. The application was based on the construction of three-dimensional wire models from only two orthogonal projections of objects (two orthogonal X-rays of affected and healthy wrists). On these wire models, an operation of the affected hand was simulated until the best fitting of the models was achieved. The use of real dimensions in computer calculation was crucial because the numerical output was used as a surgical treatment guideline. The results obtained in a group of 33 patients were excellent when compared with the results reported in the literature.

Adolescent↗

PubMed2000

A newly developed spinal simulator.

A number of studies indicate poor intra-therapist and inter-therapist reliability in the performance of graded, passive oscillatory movements to the lumbar spine. However, it has been suggested that therapists can be trained to be more consistent in their performance of these techniques if given reliable quantitative feedback. The intention of this study was to develop equipment, analogous to the lumbar spine that could be used for both teaching and research purposes. Equipment has been updated and connected to a personal IBM compatible computer. Custom designed software allows concurrent and accurate feedback to students on their performance and in a form suitable for advanced data analysis using statistical packages. The uses and implications of this equipment are discussed.

Calibration↗

PubMed1987

'Metamorphosis': computer-assisted rotational analysis and interspatial distribution of nuclear structures from serial ultrathin sections.

'Metamorphosis' is a group of computer programs designed to permit rapid three-dimensional analysis and generation of models of nuclei cells from digitized data. Infinite exterior views are possible using the rotation program and the user has the added ability to enter the object and peer out. This permits analysis of structural associations from any perspective. Since many chromosome associations cannot be abstracted without a computer, using rotation and cluster analysis reveals obscure relationships. This concept becomes important when proposing theories involving interactions between two or more objects. The program is written in BASICA and designed for use on IBM-compatible personal computers equipped with a digitizer. Three-dimensional transformations are accomplished via matrix manipulation which permits rapid generation of new images.

Animals↗

PubMed2000

Minimal toxicity with 3-FAT radiotherapy of prostate cancer.

Beam radiation with three-dimensional conformal planning appears to decrease morbidity of prostate cancer therapy. The 3-field, arc technique (3-FAT) technique was designed by computer modeling to improve radiation dose to the target and minimize dispersion to nearby organs. Toxicity was studied in patients with prostate cancer. We performed a retrospective study of 168 consecutive men with prostate cancer after 3-FAT radiotherapy with a median follow-up of 24 months. All patients, treated from 1996 through 1999 at the University of Colorado had a pathological diagnosis of cancer before irradiation. Therapy was designed with a urethrogram and planning computed tomography scan. The 3-FAT was employed using noncoplanar, rotational beams, and nonuniform blocking of portals. Patients were treated to a minimal tumor dose of 74 Gy in 37 fractions. Adverse effects were investigated. Definitive radiotherapy was given to 80% of the group, and 58% received total androgen blockade. 3-FAT produced favorable dose distributions for the rectum, bladder, femoral heads, and base of the penis. Patients routinely report minimal dysuria and frequency during treatment. There were minimal urinary complaints after irradiation and no proctitis, diarrhea, incontinence, or change in potency as a result of radiotherapy. The 3-FAT represents a technical improvement in the treatment of prostate cancer by minimizing radiation delivered to adjacent critical structures. There were minimal side effects to the rectum, bladder, and penis base despite high doses to the prostate and seminal vesicles. The large percentage of patients with preliminary prostate-specific antigen values below 1.0 portends efficacy.

Aged↗

PubMed1984

A new approach to quantitation of exercise thallium-201 scintigraphy before and after an intervention: application to define the impact of coronary angioplasty on regional myocardial perfusion.

We have developed a new computer method designed to quantitate regional myocardial thallium-201 (TI-201) initial distribution, redistribution, and clearance rate. In addition, this computer method permits the generation of functional images to compare two thallium images in the same projection to one another. These functional images can be used to demonstrate the extent of redistribution and the extent of change in regional perfusion before and after an intervention. To validate and apply this new computer technique, exercise TI-201 myocardial images obtained before and 1 week after percutaneous transluminal coronary angioplasty (PTCA) were analyzed in 20 patients with isolated left anterior descending coronary artery disease. Significant improvement in initial TI-201 activity, expressed as a percentage of maximal myocardial activity, was present in the anterior (71.9 +/- 12.0 to 84.1 +/- 11.5%, p less than 0.001) and septal (66.7 +/- 15.4 to 75.2 +/- 11.0%, p less than 0.05) regions of the left ventricle 1 week after PTCA. This increase in relative anterior wall TI-201 uptake was associated with a significant reduction in the amount of TI-201 redistribution between initial and delayed postexercise images (14.7 +/- 14.6 to 3.0 +/- 13.2%, p less than 0.05) as well as an increase in TI-201 clearance rate (t 1/2 from 8.8 +/- 4.4 to 4.3 +/- 2.5 hours, p less than 0.001). Quantitative analysis of TI-201 scans demonstrated improvement in 14 of 20 patients following PTCA. Computer-derived functional difference images depicted diminution in the extent of ischemia as manifested by redistribution of TI-201.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2002

[Hydrodynamic and biochemical effects of hypothermic perfusion of isolated kidney according to the type of pump].

OBJECTIVE: To study on isolated kidney perfusions by means of a self-designed computer-controlled organ perfusion system the hydrodynamic and biochemical effects of two types of pumps: a self-designed vacuum powered tubular pump and a classical roller pump. BASIC PROCEDURES: Experimental study performed on 12 right mini-pig kidneys. After transperitoneal bilateral nephrectomy, organs are perfused with Eurocollins solution in a randomised manner with one type of pump. The system records continuously perfusion pressure, flow and renal resistance. RESULTS: Medium renal vascular resistance was significantly lower in vacuum powered tubular pump perfusions. LDH level in the solution showed correlation with perfusion flow. CONCLUSIONS: Vacuum powered tubular pump increases renal flow and lowers renal vascular resistance significantly in comparison to roller pump. LDH level in the solution is related to good-quality hydrodynamic perfusion parameter values.

Animals↗

PubMed1998

Measurement error as a source of QT dispersion: a computerised analysis.

OBJECTIVE: To establish a general method to estimate the measuring error in QT dispersion (QTD) determination, and to assess this error using a computer program for automated measurement of QTD. SUBJECTS: Measurements were done on 1220 standard simultaneous 12 lead electrocardiograms. DESIGN: The computer program was validated against two observers on a random subset of 100 electrocardiograms. Simple laws of physics require that at least five of the six extremity leads have the same QT duration. This allows the direct assessment of the error in measuring QTD derived from five extremity leads (QTD5). It also enables ST-T amplitude dependent distributions of measurement error in determining QT duration to be established. These QT error distributions were then used to estimate the error in measuring QTD from all 12 leads (QTD12). MAIN OUTCOME MEASURES: Mean and standard deviation of error in measuring QTD duration, QTD5, and QTD12. RESULTS: Performance of the program was comparable to that of observers. Errors in measuring QT duration (measured QT minus reference QT) fell from a mean (SD) of 6.9 (17.1) ms for ST-T amplitudes < 50 microV to -1.4 (6.3) ms for amplitudes > 350 microV. Measurement errors of QTD5 and QTD12 were 20.4 (11.5) ms and 29.4 (14.9) ms. CONCLUSIONS: The fact that no QTD can exist between five of the six extremity leads provides a means of estimating QTD measurement error. Measuring error of QT duration is dependent on ST-T amplitude. QTD measurement error is large compared with typical QTD values reported.

Databases, Factual↗

PubMed1994

Evaluating the accuracy of transcribed computer-stored immunization data.

OBJECTIVE: To evaluate the accuracy of immunization records transcribed into a computer-based immunization tracking system and to assess factors that contribute to inaccurate or incomplete immunization record keeping. DESIGN: Computer-stored immunization records were analyzed for 2098 children up to 2 years of age at the time of their most recent well-child visit to the UCLA Children's Health Center over a 12-month period. For children whose immunizations were not up to date, the computer-stored records were analyzed for sources of inaccuracy by comparison with the handwritten records from which the computer-stored data were transcribed. RESULTS: An underimmunization rate of 22.5% (472 of 2098) was observed based on analysis of the computer-stored records. Comparison of the computer-stored and handwritten records revealed an overall transcription error rate of at least 10.2%. In addition, 38.4% of these apparently underimmunized children had received unrecorded immunizations from providers outside UCLA. When transcription errors were corrected and other available sources of immunization data were taken into account, the estimated rate of underimmunization decreased from 22.5% to 10.9%. CONCLUSION: Unavoidable inaccuracies can diminish the utility of the data recorded in an immunization tracking system. Some inaccuracies are related to the process of transcription, but failures to record and communicate immunization data consistently also contribute to the inaccuracy of computer-stored immunization records.

Child Health Services↗