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PubMed2003

Evaluation of stress patterns generated by reduction forceps within a photoelastic mandibular model.

INTRODUCTION: Little attention has been paid to the mechanical effects of fracture reduction forceps. AIM: This study aims to evaluate the stress patterns within the fractured mandible generated by reduction forceps. MATERIAL AND METHODS: Thirty-six mandibular models were fabricated using a photoelastic resin. Each of the three sets of mandibular models was osteotomized according to one of three different fracture types. After reducing the cut segments, reduction forceps were placed into different engagement holes to compress the segments. Photoelastic stress analysis was used to visualize the stress patterns within the fractured mandibular models as generated by the reduction forceps. RESULTS: In the case of symphyseal or parasymphyseal fractures, an optimum distribution of stresses over the fracture site was achieved when placing the reduction forceps more than 12mm away from either side of the fracture line, between the midway level of the mandibular height (bisecting the mandible) and 5mm below this level. In the case of body fractures, optimum stress distribution was achieved when the reduction forceps were placed more than 16mm from the fracture line at the midway level. CONCLUSION: Correct use of the reduction forceps helps to provide a precise three-dimensional reduction for mandibular fractures.

Birefringence↗
PubMed1996

Dynamics of the sit-to-stand movement.

The strategies of the sit-to-stand movement are investigated by describing the movement in terms of the topology of an associated phase diagram. Kinematic constraints are applied to describe movement sequences, thus reducing the dimension of the phase space. This dimensional reduction allows us to apply theorems of topological dynamics for two-dimensional systems to arrive at a classification of six possible movement strategies, distinguished by the topology of their corresponding phase portrait. Since movement is treated in terms of topological structure rather than specific trajectories, individual variations are automatically included, and the approach is by nature model independent. Pathological movement is investigated, and this method clarifies how subtle abnormalities in movement lead to difficulties in achieving a stable stance upon rising from a seated position.

Humans↗
PubMed1992

[Treatment of unstable fractures of thoracolumbar spine with neurologic injury using a reduction fixation spinal pedicle screws system].

Twenty-six patients with unstable burst fractures, chance fractures and fractures dislocations of the lower thoracic and lumbar spine were treated with a spinal pedical screw reduction fixation system (RF system). This system is a new device designed by Chinese scientists. In biomechanical testing, it provided three-dimensional reduction forces. The special design of angle pedicle screw provided accurate angle to restore the normal thoracic lumbar lordosis and to maintain it. The three-column spine in a lordotic position maximized the reduction and indirectly achieved a neurologic decompression in the spinal canal. All patients had an anatomical reduction by RF system except one case operated two weeks after injury, the spinal canal area increased over 30% by CT (P < 0.01). Except four cases with Frankle A out of twenty patients with neurologic deficits, all other patients had at least one grade progress. Of them one improved from A to D, ten from C and D to normal. These twenty patients were followed-up over six months. All of them maintained anatomical reduction by RF system. Bone grafting had successful fusion by follow-up X-ray examinations. There were no important complications after surgery. The system is of simple structure facilitation implantation and enable the patients beginning ambulatory movements early, therefore it gives more satisfactory results over conventional Harrington and other segmental spinal instrumentation systems.

Adolescent↗
PubMed2002

Advances in computers and image processing with applications in nuclear medicine.

The continuing advances in hardware performance had made many previously computationally unattractive methods feasible, an example being iterative reconstruction in tomography, which is now routine. Dynamic SPECT can also be performed. However the aim of image processing is not just to produce pretty pictures, but to extract good clinical information. The methods also need to incorporate clinical knowledge and be defined using clinical constraints. In general data in nuclear medicine are n-D, often 3-D plus time. Data reduction for example by the extraction of physiological information, is important. Such data are in any case hard to visualise without compression, for example some kind of dimensionality reduction, going from n-D to a 2-D "functional" image. Both linear and non-linear operations can be considered. To extract physiological data, we need to fit models. Two classes of method are important: data driven and hypothesis driven. Examples of data driven methods are principal component analysis and factor analysis, where the model is derived form the data. Hypothesis driven methods are all implicitly or explicitly based on model fitting. A preliminary data driven step followed by an hypothesis driven approach could be called constrained statistical image analysis. Examples are shown as used in nuclear medicine and are being extended to MRI. Another important problem considered is that of multi-modality image registration and fusion. Although many methods exist, all based on the minimisation of an appropriate distance functions between 2 image data sets such as mutual information, additional constraints are required when the images are not so similar. Additional constraints can be imposed by means of cluster analysis of the n-dimensional feature space. In the analysis of such data, tests against reference data sets (atlases) are required, normally requiring warping the data sets in space, for example by the use of optic flow, or some kind of diffusion equation. Real time analysis of data during acquisition can lead to optimisation of acquisition procedures. Incorporation of such image analysis into a decision support system is desirable.

Algorithms↗
PubMed1998

Application of Kohonen Neural Networks in classification of biologically active compounds.

Automated data classification is an indispensable tool in Drug Design. It allows to select homogeneous training sets or to distinguish compounds with required biological properties. The Kohonen Neural Networks (KNN) suggest new means for classification of biologically interesting compounds. In this paper, first, capabilities of KNN in data dimensionality reduction are presented as compared with the capabilities of Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The advantages of KNN become evident with increasing data dimensionality and size of the training set. Then, new methods are suggested to evaluate the quality of KNN models. Finally, a case study on chemical and biological data is presented. The database studied includes more than 2000 organophosphorous potent pesticides. The Kohonen maps were obtained which allow to distinguish compounds with different biological behavior.

Cluster Analysis↗
PubMed2002

Semi-three-dimensional algorithm for time-resolved diffuse optical tomography by use of the generalized pulse spectrum technique.

Although a foil three-dimensional (3-D) reconstruction with both 3-D forward and inverse models provide, the optimal solution for diffuse optical tomography (DOT), because of the 3-D nature of photon diffusion in tissue, it is computationally costly for both memory requirement and execution time in a conventional computing environment. Thus in practice there is motivation to develop an image reconstruction algorithm with dimensional reduction based on some modeling approximations. Here we have implemented a semi-3-D modified generalized pulse spectrum technique for time-resolved DOT, where a two-dimensional (2-D) distribution of optical properties is approximately assumed, while we retain 3-D distribution of photon migration in tissue. We have validated the proposed algorithm by reconstructing 3-D structural test objects from both numerically simulated and experimental date. We demonstrate our algorithm by comparing it with the calibrated 2-D reconstruction that is in widespread use as a shortcut to 3-D imaging and proving that the semi-3-D algorithm outperforms the calibrated 2-D algorithm.

Algorithms↗
PubMed2002

Clustering of the SOM easily reveals distinct gene expression patterns: results of a reanalysis of lymphoma study.

BACKGROUND: A method to evaluate and analyze the massive data generated by series of microarray experiments is of utmost importance to reveal the hidden patterns of gene expression. Because of the complexity and the high dimensionality of microarray gene expression profiles, the dimensional reduction of raw expression data and the feature selections necessary for, for example, classification of disease samples remains a challenge. To solve the problem we propose a two-level analysis. First self-organizing map (SOM) is used. SOM is a vector quantization method that simplifies and reduces the dimensionality of original measurements and visualizes individual tumor sample in a SOM component plane. Next, hierarchical clustering and K-means clustering is used to identify patterns of gene expression useful for classification of samples. RESULTS: We tested the two-level analysis on public data from diffuse large B-cell lymphomas. The analysis easily distinguished major gene expression patterns without the need for supervision: a germinal center-related, a proliferation, an inflammatory and a plasma cell differentiation-related gene expression pattern. The first three patterns matched the patterns described in the original publication using supervised clustering analysis, whereas the fourth one was novel. CONCLUSIONS: Our study shows that by using SOM as an intermediate step to analyze genome-wide gene expression data, the gene expression patterns can more easily be revealed. The "expression display" by the SOM component plane summarises the complicated data in a way that allows the clinician to evaluate the classification options rather than giving a fixed diagnosis.

Cluster Analysis↗
PubMed1997

The zygomatic-sphenoid fracture line in malar reduction. A cadaver study.

OBJECTIVE: To demonstrate the persistent malar displacement and distraction of the zygomatic-sphenoid fracture line that is possible after alignment of the frontozygomatic and infraorbital rim fractures of a displaced malar fracture. DESIGN: Nonblinded cadaver study. SUBJECTS: Three fresh cadaver heads and 1 representative clinical example. INTERVENTION: The cadaver heads were subjected to blunt trauma to the malar eminence. Reduction of the malar unit was performed either with attention to the frontozygomatic and infraorbital rim fractures alone or with concomitant inspection of the zygomatic-sphenoid fracture line. The representative case was repaired with a trans-conjunctival approach for inspection of the zygomatic-sphenoid fracture line. RESULTS: Persistent malar asymmetry is possible after the reduction of displaced malar fractures when only the frontozygomatic and infraorbital rim buttresses are used for reference. In each case in our study, the zygomatic-sphenoid fracture line remained distracted. Alignment of the zygomatic-sphenoid fracture restored premorbid malar position. CONCLUSION: Inspection of the zygomatic-sphenoid fracture line can contribute significantly to the precise 3-dimensional reduction of displaced malar fractures.

Adult↗
PubMed2002

Maxillary tooth size variation in dentitions with palatal canine displacement.

The association between the presence of palatally displaced maxillary canines (PDC) and other anomalies is well known, particularly with regard to the size and form of the lateral incisor. The present study investigated the connection between the maxillary canine anomaly and the existence of a reduction in the size of the other teeth in the maxilla in 58 consecutively treated patients (37 females, 21 males) aged 11-15 years, and compared these with a control group of 40 consecutively treated subjects (20 males, 20 females) with normally erupted maxillary canines. The findings indicate that the teeth of PDC males are reduced in size and similar to those of PDC females, in sharp contrast to the general population, where males have larger teeth. This is the result of a dimensional reduction in the teeth of PDC males, which was statistically significant for all teeth (P < 0.01) in the bucco-lingual (B-L) dimension, and for the first premolars and first molars in the mesio-distal (M-D) dimension. The sole teeth affected for both sexes were the lateral incisors in their B-L dimension. Bilaterally and unilaterally affected subjects presented differing M-D and B-L tooth dimensions.

Adolescent↗
PubMed1998

Feature extraction for on-line EEG classification using principal components and linear discriminants.

The study focuses on the problems of dimensionality reduction by means of principal component analysis (PCA) in the context of single-trial EEG data classification (i.e. discriminating between imagined left- and right-hand movement). The principal components with the highest variance, however, do not necessarily carry the greatest information to enable a discrimination between classes. An EEG data set is presented where principal components with high variance cannot be used for discrimination. In addition, a method based on linear discriminant analysis (LDA), is introduced that detects principal components which can be used for discrimination, leading to data sets of reduced dimensionality but similar classification accuracy.

Brain Damage, Chronic↗
PubMed2000

Indirect posterior reduction and fusion of the traumatic herniated disc by using a cervical pedicle screw system.

OBJECT: In this study the authors retrospectively review 16 patients with traumatic disc herniation secondary to middle and lower cervical spine injuries who underwent a single posterior reduction and fusion procedure in which a cervical pedicle screw system was used. The study was undertaken to evaluate whether the procedure effectively reduced the disc herniation and whether it can be safely conducted without performing anterior decompressive surgery. METHODS: A total of 73 patients with middle and lower cervical spine injuries were identified. In 50 patients, pre- and postoperative magnetic resonance (MR) images were obtained, and disc herniation was defined as the presence of an extruded disc that deformed the thecal sac or nerve roots. Traumatic disc herniation was revealed in 16 patients (32%) who underwent a single posterior reduction/fusion procedure in which a cervical pedicle screw system was used. The average follow-up period was 4.25 years (2-6.25 years). In all patients the average kyphotic deformity was 18 degrees, which was corrected to 0.7 degrees lordosis postoperatively. Anterior translation was reduced from 8 to 0.7 mm. The preoperative disc height ratio of 63% (normal 100%) was improved to 104%. Preoperative MR images revealed traumatic disc herniation in all 16 patients; postsurgery, reduction or reversal of disc herniation was observed in all patients. Thecal sac and/or spinal cord compression had disappeared after indirect decompression was achieved using a posterior procedure. No additional decompressive procedures were required to remove residual herniated disc material. Preoperatively, four patients presented with cervical radiculopathy, 10 with myelopathy (eight incomplete and two complete), and two without neurological symptoms. At final follow up, complete recovery was observed in all four patients with radiculopathy and improvement of at least one Frankel grade was shown in six patients (60%) with myelopathy. There were no cases of neurological deterioration immediately after surgery or during the course of the follow-up period. In all patients solid bone union was demonstrated, and there were no implant-related complications. CONCLUSIONS: Traumatic disc herniation may occur frequently in association with injury of the cervical spine. The incidence of traumatic disc herniation in our series was 32%. The cervical pedicle screw system allowed three-dimensional reduction of the injured cervical segment and reduction or reversal of a disc herniation. After surgery, compression of the thecal sac and/or spinal cord had disappeared. The cervical pedicle screw system provides effective and safe fixation of the cervical spine injury-related traumatic disc herniation, and the surgery can be performed safely in a single posterior-approach procedure without need of additional anterior decompressive interventions.

Adolescent↗
PubMed1991

Treatment of 813 zygoma-lateral orbital complex fractures. New aspects.

A 10-year experience with surgical treatment of 813 zygomalateral orbital complex fractures is reviewed. Regardless of the type or severity of the fracture pattern, concomitant fractures of the orbital floor and rim were approached exclusively through the transconjunctival approach without a lateral canthotomy. The advantages of this approach compared with the subciliary access are the avoidance of a visible scar and markedly reduced incidence of postoperative lower eyelid complications such as ectropion and edema. Implants of lyophilized dura or cartilage and autogenous bone were used to reconstruct orbital floor defects. Malar asymmetry is a frequent complication of zygoma fractures resulting from inadequate three-dimensional reduction. Methods for accurate reduction and stabilization, indications for closed and open reduction, and management of the fractured infraorbital rim are emphasized. The indications for miniplates vs wire ligatures for the infraorbital rim are discussed. Long-term follow up and evaluation of the results with regard to the fracture pattern, complications, maxillary sinus dysfunction, and facial and orbital symmetry are presented.

Bone Plates↗
PubMed1975

Genetic differentiation among Sardinian villages.

The present study reports an analysis of genetic differentiation among 14 Sardinian villages located mainly in the center of the island. Chi-square tests show significant genetic heterogeneity among villages, and analyses by F- and R- statistics indicate an essentially random pattern of differentiation for all alleles. Using the kinship methods of Morton, a matrix, R, with elements rij describing the correlations between the gene frequencies of villages i and j is obtained. Use of Malécot's formula relating the rij to the geographic distances between villages shows a rapid decline of kinship with increasing distance but reveals essentially no relationship for distances over 40 km. Rotation of a two-dimensional reduction of the kinship matrix to maximum congruence with the geographic distances indicates that about 25% of the genetic distances can be accounted for by the geographic location of the villages. Isolation due in part to cultural factors, genetic drift, and special local or regional patterns of villages associations appear to be involved in the pattern of genetic variation.

Adolescent↗
PubMed1987

On multiparameter data analysis in flow cytometry.

Increasing numbers of parameters that are accessible to simultaneous measurement in flow cytometric instruments, combined with the extremely large sample sizes common in flow cytometry, make it necessary to examine methods of multivariate statistics for their applicability to problems of visualization and quantitative analysis of flow cytometric data. This article describes some approaches to dimensionality reduction that appear well suited for data sets obtained by flow cytometry.

Flow Cytometry↗
PubMed2002

Conformational analysis: a new approach by means of chemometrics.

In conformational analysis, the systematic search method completely maps the space but suffers from the combinatorial explosion problem because the number of conformations increases exponentially with the number of free rotation angles. This study introduces a new methodology of conformational analysis that controls the combinatorial explosion. It is based on a dimensional reduction of the system through the use of principal component analysis. The results are exactly the same as those obtained for the complete search but, in this case, the number of conformations increases only quadratically with the number of free rotation angles. The method is applied to a series of three drugs: omeprazole, pantoprazole, lansoprazole-benzimidazoles that suppress gastric-acid secretion by means of H+, K+-ATPase enzyme inhibition.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2003

Machine learning approaches to lung cancer prediction from mass spectra.

We addressed the problem of discriminating between 24 diseased and 17 healthy specimens on the basis of protein mass spectra. To prepare the data, we performed mass to charge ratio (m/z) normalization, baseline elimination, and conversion of absolute peak height measures to height ratios. After preprocessing, the major difficulty encountered was the extremely large number of variables (1676 m/z values) versus the number of examples (41). Dimensionality reduction was treated as an integral part of the classification process; variable selection was coupled with model construction in a single ten-fold cross-validation loop. We explored different experimental setups involving two peak height representations, two variable selection methods, and six induction algorithms, all on both the original 1676-mass data set and on a prescreened 124-mass data set. Highest predictive accuracies (1-2 off-sample misclassifications) were achieved by a multilayer perceptron and Naïve Bayes, with the latter displaying more consistent performance (hence greater reliability) over varying experimental conditions. We attempted to identify the most discriminant peaks (proteins) on the basis of scores assigned by the two variable selection methods and by neural network based sensitivity analysis. These three scoring schemes consistently ranked four peaks as the most relevant discriminators: 11683, 1403, 17350 and 66107.

Algorithms↗
PubMed1996

Tobacco smoke upper respiratory response relationships in healthy nonsmokers.

This study determined exposure-response relationships to side-stream tobacco smoke (2 hrs; 0, 1, 5, and 15 ppm CO) in 29 healthy nonsmoking young adults. Sixteen subjects had no history of environmental tobacco smoke rhinitis (ETS-NS) while 13 subjects had a history of ETS rhinitis (ETS-S). Eye irritation and odor perception showed a statistically significant exposure response in both groups; headache was significant in ETS-S and nose irritation was significant in ETS-NS subjects. Significant postexposure (P1) symptoms were first reported at 1 ppm CO among both groups, but in 3/9 symptoms were significantly greater at this exposure level in ETS-S subjects. Nasal congestion, rhinorrhea, and cough increased significantly at 15 ppm CO only. In ETS-S subjects, nasal volume decreased and nasal resistance increased in an exposure-response fashion. ETS-NS subjects had a qualitatively different shape to the exposure-response curve; significant dimensional reductions in mid- and posterior nasal volume occurred with exposure at 1 ppm CO but not at 5 ppm CO and reductions in posterior nasal volume occurred at 15 ppm CO exposure. These studies indicate subjective and objective response relationships with exposure to sidestream tobacco smoke at concentrations from 1 to 15 ppm CO. Some differences are noted among the two subject groups in the magnitude of some symptoms at the lowest exposure level and in the qualitative shape of the acoustic rhinometry and nasal resistance exposure-response curves.

Adult↗
PubMed1988

Auto-association by multilayer perceptrons and singular value decomposition.

The multilayer perceptron, when working in auto-association mode, is sometimes considered as an interesting candidate to perform data compression or dimensionality reduction of the feature space in information processing applications. The present paper shows that, for auto-association, the nonlinearities of the hidden units are useless and that the optimal parameter values can be derived directly by purely linear techniques relying on singular value decomposition and low rank matrix approximation, similar in spirit to the well-known Karhunen-Loève transform. This approach appears thus as an efficient alternative to the general error back-propagation algorithm commonly used for training multilayer perceptrons. Moreover, it also gives a clear interpretation of the rôle of the different parameters.

Mathematics↗