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Biomedical subjects

P E Lestrel

Publications and source records attributed to P E Lestrel.

At least 19 recordsLinked to original sources
PubMed2005

Sexual dimorphism in the Japanese cranial base: a Fourier-wavelet representation.

An approach, computational shape analysis (CSA), is presented here which utilizes a Fourier-wavelet representation to numerically describe shape features of biological forms. Two elements are involved: 1) elliptical Fourier functions (EFFs), to provide estimates of global aspects, and 2) continuous wavelet transforms (CWTs) to generate an objective estimate of localized features. EFFs are computed, using a set of pseudohomologous points, to create a precise analog of the boundary. This computed contour is then normalized by scaling and rotated in two-dimensional space to insure a representation that is invariant with respect to starting point, size, and orientation. The predicted point coordinates derived from the EFFs are submitted to CWT for further processing. Wavelet coefficients are then computed to identify localized features, localization being a subjective process with EFFs. The advantage of wavelets is that they eliminate the inevitable subjectivity inherent in the choice of measurements. To test the usefulness of CSA, a sample of cranial base (CB) lateral radiographic outlines was available. Five archaeological periods, Yayoi, Kofun, Kamakura, Edo, and Modern, were utilized (n = 297). Statistically significant differences in sex and archaeological age were found. Although archaeological age differences were present, they were small and random in character, suggesting stability in the CB structures. In contrast, sexually dimorphic differences were present in every group from the Yayoi to the Modern period. This presence of sexually dimorphic differences in shape was consistent with earlier studies of M. nemestrina, G. gorilla, and P. troglodytes. Consequently, it is suggested that the pattern of sexual dimorphism documented in the Japanese CB is a primate pattern with an ancient evolutionary history. The results demonstrate, both visually and numerically, that CSA is a powerful approach for describing both global and localized features of craniofacial structures such as the CB.

Anthropology, Physical↗
PubMed2000

Describing shape changes in the human mandible using elliptical Fourier functions.

Elliptical Fourier functions (EFF) were generated for the boundary outline of the mandibular form in 24 non-orthodontic growth study subjects at 9, 11, 13, and 15 years of age. The mean residual fit (observed versus predicted points) of the mandibular form was 0.11 mm, with a range from 0.09 to 0.14 mm, suggesting an accurate fit. The mean plot for each of the four age groups was area standardized and superimposed on the centroid. Shape changes in males and females were found to be similar. No significant shape changes were found between 9 and 11 years. Shape changes were observed in the lower incisor area, the mental region, the body of the mandible, and the gonial angle area between 11 and 15 years. These changes coincided with the onset of the pubertal growth spurt.

Adolescent↗
PubMed2000

Sex differences in proximal humeral outline shape: elliptical Fourier functions.

A method is presented for the numerical analysis of sex differences in size and shape of the proximal humeral outlines using elliptical Fourier functions (EFFs). A skeletal sample consisting of right and left humeri pairs of 69 individuals, 36 males and 33 females, was used. The proximal superior view in the plane of the proximo-distal axis of each humerus was photographed and then 54 boundary points were located on the two-dimensional outline tracings. These points were digitized and used to compute EFFs with 27 harmonics. From the EFFs, a set of expected points on the proximal humeral outline was generated using the centroid as an origin. Superimposition of the male and female outlines on this centroid provided a detailed picture of the relative sex differences in size and shape with respect to that center. The bounded area of the proximal humeral outline showed statistically significant sex differences. Additionally, statistical results of the amplitudes derived from the "area-standardized" EFFs and visual assessments of the mean outline plots indicated significant sex differences in shape of the proximal humeral outlines. Focusing on localized regional differences, the greater tubercle was located more postero-medially and the lesser tubercle was located more anteriorly in the males compared to the females. Sex determinations from the proximal humeri were also examined with discriminant functions based on the amplitudes, which represent shape characteristics of the outline, and the hounded area. Using a cross-validation method, predictions of the percentages of cases correctly classified with the discriminant functions were ranged from 92.8% to 95.7% for the right and left humeral data. These results suggest that differences in size and shape of the proximal humeral outlines may be better predictors of sex when compared with conventional measurements of the humerus.

Adult↗
PubMed1999

Shape changes in the cleft palate maxilla: a longitudinal study.

OBJECTIVE: The purpose of this study was to compare the shape of the maxilla in Norma lateralis of cleft lip and palate (CLP) patients with non-CLP controls matched for sex and age. This study utilized elliptical Fourier functions to assess the presence of residual shape changes in the cleft palate maxilla after treatment, compared with controls. DESIGN: Longitudinal data (n = 25) were available from the Miami Craniofacial Anomalies Foundation. From these data, two samples were selected: group I (mean age and SD, 5.06 +/- 1.82 years) after lip surgery and the initiation of palate surgery and group II (16.58 +/- 2.42 years) well after the conclusion of surgery. Twenty-two of these patients were matched with controls (5.11 +/- 1.33 and 15.91 +/- 2.25 years, respectively). The maxillary outline as seen on the lateral radiograph was (1) traced, (2) fitted with a series of 48 closely placed points, (3) digitized, and (4) submitted to a specially written routine that computes elliptical Fourier functions (EFFs). These EFFs are close analogs of the bounded maxillary outline as judged by the residual or difference between the observed points and the predicted points generated by the Fourier function. Each maxillary outline was subsequently standardized for size and corrected for positioning in two-dimensional space. RESULTS AND CONCLUSIONS: Utilizing a three-way multivariate analysis of variance, statistically significant shape differences were obtained for both young and older groups, as well as between the CLP and controls. No significant gender differences were found. Morphological differences consisted of a posterior repositioning of the nasal crest aspect in the CLP cases. These results suggest that although a clinically satisfactory treatment result was obtained, differences in maxillary shape remain.

Adolescent↗
PubMed1994

Skeletal jaw relationships: a quantitative assessment using elliptical Fourier functions.

Elliptical Fourier functions (EFF) were generated for the boundary outlines of the hard tissue craniofacial complex including the maxilla, mandible, and cranial base in order to quantitatively describe adult patients (n = 98) who were initially classified into nine skeletal groups by a combination of conventional cephalometric measures and clinical judgement. The mean residual fit of the EFF-predicted points and the original digitized data for the individual subjects ranged from .42 mm to .61 mm with a mean of .52 mm suggesting an accurate fit. Visual inspection of the individual plots confirmed this. Predicted classifications from a step-wise discriminant analysis based on EFF amplitudes were compared with the original classifications. The discordance rates for A-P and vertical plane classification were 21% and 13% respectively with an overall discordance rate of 33%. In general, a cluster analysis using EFF amplitudes did not identify clusters very similar in membership to the original groups; however, it was marginally successful in identifying members of the more severe groups and, like discriminant analysis, appeared to be more sensitive to vertical morphological differences. The overall lack of agreement between classifications and clusters based on EFF amplitudes and the original classifications may indicate that traditional skeletal categories such as those used in this study do not actually represent discrete groups.

Adolescent↗
PubMed1993

Longitudinal study of cranial base shape changes in Macaca nemestrina.

The primate cranial base (CB) represents a complex irregular structure even when limited to two dimensions, making it difficult to describe quantitatively using the conventional metrical approach composed of angles and distances. Consequently, a curve-fitting procedure, elliptical Fourier functions (EFF), was utilized, which accurately defines the form of complex two-dimensional morphologies. A longitudinal Macaca nemestrina sample consisting of 14 females and 15 males was utilized. Lateral headfilms, 1 to 8 years, were available (275 headfilms). Because the x-rays were not always taken at precise one-year intervals, a number of headfilms were excluded, which reduced the sample to 181. The CB boundary outline was carefully traced onto acetate sheets and 54 points located. The observed points were digitized and used to compute size-standardized EFF's with 20 harmonics. From each EFF, a set of 150 expected distances to the CB boundary was generated using the centroid as an origin. Superimposition of the CB's on the centroid also provided a detailed picture of the relative shape changes with respect to that center. Statistically significant shape differences were found as a function of age and sexual dimorphism. These age changes consisted of a gradual anteroposterior lengthening with a concomitant narrowing in the superoinferior direction. Specifically, a lengthening of the dorsal clivus and an anterior migration of the hypophyseal fossa could also be discerned. Thus, Fourier descriptors provide a particularly powerful method for documenting, both visually and numerically, the shape changes of complex two dimensional morphologies.

Animals↗
PubMed1993

Quantification of function regulator therapy using elliptical Fourier functions.

The application of various functional appliances to correct antero-posterior skeletal discrepancies in the treatment of Class III malocclusion has received increased attention. In this context, elliptical Fourier functions (EFF) are particularly useful for eliciting boundary-outline information. This longitudinal study was undertaken to visually and numerically describe the shape alterations arising as a response to treatment with the FR-3 appliance of Fränkel. The subjects chosen were Caucasians (n = 14) from the Glasgow Dental Hospital and School who presented with Class III incisor relationships. Lateral cephalometric head-films were available prior to the initiation of treatment, at the end of active treatment, and at least one year out of retention. Maxillary and mandibular boundary outlines were carefully traced. A set of points, 42 on the maxilla, and 78 on the mandible, were precisely located. These points were then digitized and used to compute EFF's with 20 harmonics. These equations were then standardized for size. Subsequently, 102 maxillary and 150 mandibular closely spaced points on the outline were calculated from the EFF's. After superimposition on the centroid, expected vectors were then computed to these points from the centroid. Statistically significant dento-alveolar shape changes could be discerned with treatment. These involved a localized anterior repositioning of the maxillary incisal aspect with a concomitant posterior displacement of the mandibular incisal aspect. There was no evidence of shape changes in the basal areas of either the maxilla or mandible. This method of fitting Fourier descriptors, specifically EFF's, provides a precise numerical and visual description of the changes arising from functional regulator therapy.

Adolescent↗
PubMed1993

Fourier analysis of shape changes in the Japanese skull: occipital view.

Photographs (norma occipitalis) of Japanese adult skulls (n = 171) were mathematically described with Fourier analysis to assess shape changes over time. The materials used were adult male skulls excavated from the Kanto District and covered four age-periods; Jomon (2000-1000 BC). Kamakura (14C. AD), Muromachi (15C. AD). and Edo (18C. AD). Mean raw data values, containing both size and shape information of each vector, were compared for the four age-periods. Statistically significant differences among the four age-periods were found using an ANOVA. The form of the Jomon skulls displayed the most difference among the four groups. This trend was especially evident at the parietal margin. Fourier analysis was subsequently undertaken to detect the presence of secular changes in skull form after standardization for size. Once the effect of size was removed, the occipital shape of the Jomon skulls was found to be essentially similar to those of the more recent age-periods.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Shape changes due to functional appliances.

Functional appliances are now routinely used in orthodontic treatment to correct anteroposterior skeletal discrepancies, based on the assumption that existing functional patterns can be modified to yield a new morphological pattern. However, the mechanisms by which this correction occurs remain in dispute as current measurement procedures, primarily mathematical, do not adequately describe shape changes. This paper introduces a new measurement method, Fourier descriptors, to clinical dentistry.

Adolescent↗
PubMed1989

Some approaches toward the mathematical modeling of the craniofacial complex.

It is increasingly recognized by quantitative morphologists that the use of the conventional metrical approach (CMA), consisting of linear distances, angles, and ratios, to describe the size and shape of complex morphological forms as well as the shape changes between forms, is a procedure that is inherently deficient. Conventional metrics were designed to measure regular geometric objects and were never intended to describe the shape of complex irregular forms. A number of new methods have been developed to describe complex irregular shapes that attempt to circumvent the difficulties with CMA. These procedures fall into two categories, those dependent on homologous-point representations and those based on boundary representations. Three of these new methods, 1) biorthogonal grids, 2) finite element scaling, and 3) elliptical Fourier analysis, are reviewed here. While all three methods represent major improvements over CMA as shape and shape change descriptors, they must be considered as promising preliminary numerical models rather than final definitive pronouncements. Each method has constraints that preclude it from being the method of choice. It is apparent that a generalized model for the characterization of complex morphological forms remains to be developed.

Animals↗
PubMed1989

Carapace growth of the turtle Chrysemys scripta: a longitudinal study of shape using Fourier analysis.

Because the majority of morphological structures encountered in Biology are irregular in form, conventional metrics composed of distances, angles and ratios, are inefficient shape descriptors. To circumvent this drawback in the application of morphometrics to describe 2 dimensional shapes, an alternative procedure based on Fourier analysis was developed and applied to the turtle carapace. Once size differences were controlled for, the presence of shape changes with age could be demonstrated. This study showed that small systematic differences in the phase angle are associated with increase in carapace asymmetry. The differences were not visually apparent in the original data. These results reinforce the need for precise shape descriptors that are capable of measuring a large percentage of the informational content that is present in all biological forms.

Age Factors↗
PubMed1982

A Fourier analytic procedure to describe complex morphological shapes.

Most time-dependent processes such as growth are characterized by changes in size and shape. An accurate assessment of such morphological changes at specific points in time and over time has remained problematic. The conventional metrical approach, consisting of a comparatively few and subjectively chosen distances, angles, and ratios remains an inefficient descriptor of complex shapes. This is not to say that conventional metrics have no utility (their use depends on the application), but rather that they cannot measure more than a fraction of the informational content present in complex shapes. An alternative approach to conventional metrics has been developed using a Fourier analytic procedure. The Fourier function chosen provides an accurate representation of the morphological form. As the Fourier coefficients are orthogonal it is possible to partition out the effect of size to facilitate comparisons based solely on shape. The application of this Fourier procedure to describe morphological shapes is illustrated with data drawn from craniofacial as well as postcranial skeletal materials.

Aging↗
PubMed1980

A cephalometric study of mandibular cortical bone thickness in dentulous persons and denture wearers.

Cephalometric measurements of the cortical thickness of the inferior mandibular border and the inferior aspect of the mandibular symphysis were compared in two groups of subjects, one with complete dentition and the other wearing complete maxillary and mandibular dentures. Although the cortical thickness of the inferior mandibular border increased slightly with age in both dentition groups, the cortical thickness was significantly less in denture groups than in their respective dentition groups. The opposite was true with the cortical thickness of the inferior aspect of the mandibular symphysis; a decrease in thickness was noted with age, and a slight increase in thickness was noted with edentulousness. The results suggest that bone remodeling can be expected at sites distant from the residual ridge in denture wearers.

Adult↗
PubMed1978

The mandibular dental arch: part III. Buccal expansion.

The tendency toward relapse in intercuspid width has been examined with those cases having final intercuspid width less than 27 mm showing significantly less relapse than those cases with final intercuspid width of 28 mm or more. The point of contact between the cuspid and first premolar has been introduced as a key point on the arch, determining arch width. An individualized norm has been derived for this measurement as a function of the patient's tooth size, facial pattern, and other variables based upon stable normal occlusions in treated cases. Those cases expanded to a dimension exceeding the norm by more than 1 mm showed a greater propensity toward relapse. The group following the norm was significantly more stable than the over- and underexpansion groups at the .025 significance level. An individual norm for intermolar width based upon the patient's facial pattern (using frontal and lateral X-rays) has been established. Cases showing relapse showed considerably less space between the lower molar and the JAG plane, and greater lower face height than stable cases. The results show that the space available for the permanent dentition can be estimated in advance of treatment based on the patient's own skeletal measurements, thus minimizing unnecessary extractions, relapse, and extended treatment time due to errors in diagnosis.

Adolescent↗
PubMed1978

The cranial base in fetal Macaca nemestrina: a quantitative analysis of size and shape.

The applicability of Fourier analysis to quantitate the midsagittal cranial base has been demonstrated utilizing fetal Macaca nemestrina. This methodology accurately measures the irregular form of the endocranial profile, minimizes the effects of size, and maximizes shape differences. This method provides a quantitative dimension to the descriptive analysis of shape change previously observed with a combined histologic and cephalometric analysis.

Animals↗