Describing a craniofacial anomaly: Finite elements and the biometrics of landmark locations

Bookstein, Fred L.

doi:10.1002/ajpa.1330740408

Cited by 64 publications

(31 citation statements)

References 8 publications

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“…Preliminary results suggest that the number of landmarks can be substantially reduced without sacrificing much in terms of performance. Reductions in user effort could also be realized through automating landmark placement, although automatically defining unequivocal landmarks in biological objects is not trivial and often difficult to generalize (Berkley et al, 2000;Bookstein, 1987;Bowden et al, 1998b;Lapeer and Prager, 2000;Lazarus and Verroust, 1998;Richtsmeier et al, 2002;Yoshizawa et al, 2004). We found identifying landmarks visually simple, and therefore minimizing the number of landmarks was not one of our objectives.…”

Section: Discussionmentioning

confidence: 91%

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Mesh-morphing algorithms for specimen-specific finite element modeling

Sigal

Hardisty

Whyne

2008

Journal of Biomechanics

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Despite recent advances in software for meshing specimen-specific geometries, considerable effort is still often required to produce and analyze specimen-specific models suitable for biomechanical analysis through finite element modeling. We hypothesize that it is possible to obtain accurate models by adapting a pre-existing geometry to represent a target specimen using morphing techniques. Here we present two algorithms for morphing, automated wrapping (AW) and manual landmarks (ML), and demonstrate their use to prepare specimen-specific models of caudal rat vertebrae. We evaluate the algorithms by measuring the distance between target and morphed geometries and by comparing response to axial loading simulated with finite element (FE) methods. First a traditional reconstruction process based on microCT was used to obtain two natural specimen-specific FE models. Next, the two morphing algorithms were used to compute mappings from the surface of one model, the source, to the other, the target, and to use this mapping to morph the source mesh to produce a target mesh. The microCT images were then used to assign element-specific material properties. In AW the mappings were obtained by wrapping the source and target surfaces with an auxiliary triangulated surface. In ML, landmarks were manually placed on corresponding locations on the surfaces of both source and target. Both morphing algorithms were successful in reproducing the shape of the target vertebra with a median distance between natural and morphed models of 18.8 and 32.2 microm, respectively, for AW and ML. Whereas AW-morphing produced a surface more closely resembling that of the target, ML guaranteed correspondence of the landmark locations between source and target. Morphing preserved the quality of the mesh producing models suitable for FE simulation. Moreover, there were only minor differences between natural and morphed models in predictions of deformation, strain and stress. We therefore conclude that it is possible to use mesh-morphing techniques to produce accurate specimen-specific FE models of caudal rat vertebrae. Mesh morphing techniques provide advantages over conventional specimen-specific finite element modeling by reducing the effort required to generate multiple target specimen models, facilitating intermodel comparisons through correspondence of nodes and maintenance of connectivity, and lends itself to parametric evaluation of "artificial" geometries with a focus on optimizing reconstruction.

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Section: Discussionmentioning

confidence: 91%

“…Thin-plate splines were used which produce a nice smooth transformation and allow precise transformation of point A to A 0 . We used the classical Bookstein thin-plate splines transformation as implemented in Amira (Bookstein, 1987;Zelditch et al, 2004).…”

Section: Manual Landmarks (Ml)mentioning

confidence: 99%

Mesh-morphing algorithms for specimen-specific finite element modeling

Sigal

Hardisty

Whyne

2008

Journal of Biomechanics

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“…However, this technique has been superceded by newer approaches. One of these, finite element scaling analysis (FESA) [20], has been used widely, despite statistical objections to this usage [21). FESA is the inverse of a form of analysis widely used in engineering to study strain in materials under loads.…”

mentioning

confidence: 99%

Geometric Morphometrics in Primatology: Craniofacial Variation in Homo sapiens and Pan troglodytes

Lynch

Wood²,

Luboga³

1996

IJFP

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Traditionally, morphometric studies have relied on statistical analysis of distances, angles or ratios to investigate morphometric variation among taxa. Recently, geometric techniques have been developed for the direct analysis of landmark data. In this paper, we offer a summary (with examples) of three of these newer techniques, namely shape coordinate, thin-plate spline and relative warp analyses. Shape coordinate analysis detected significant craniofacial variation between 4 modern human populations, with African and Australian Aboriginal specimens being relatively prognathous compared with their Eurasian counterparts. In addition, the Australian specimens exhibited greater basicranial flexion than all other samples. The observed relationships between size and craniofacial shape were weak. The decomposition of shape variation into affine and non-affine components is illustrated via a thin-plate spline analysis of Homo and Pan cranial landmarks. We note differences between Homo and Pan in the degree of prognathism and basicranial flexion and the position and orientation of the foramen magnum. We compare these results with previous studies of these features in higher primates and discuss the utility of geometric morphometrics as a tool in primatology and physical anthropology. We conclude that many studies of morphological variation, both within and between taxa, would benefit from the graphical nature of these techniques.

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“…7 This method requires the definition of corresponding landmarks for the initial (before deforming) and final (after deforming) shapes (Fig. 2).…”

Section: Process Sizementioning

confidence: 99%

Mesh Morphing and Response Surface Analysis: Quantifying Sensitivity of Vertebral Mechanical Behavior

Sigal

Whyne

2009

Ann Biomed Eng

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Vertebrae provide essential biomechanical stability to the skeleton. In this work novel morphing techniques were used to parameterize three aspects of the geometry of a specimen-specific finite element (FE) model of a rat caudal vertebra (process size, neck size, and end-plate offset). Material properties and loading were also parameterized using standard techniques. These parameterizations were then integrated within an RSM framework and used to produce a family of FE models. The mechanical behavior of each model was characterized by predictions of stress and strain. A metamodel was fit to each of the responses to yield the relative influences of the factors and their interactions. The direction of loading, offset, and neck size had the largest influences on the levels of vertebral stress and strain. Material type was influential on the strains, but not the stress. Process size was substantially less influential. A strong interaction was identified between dorsal-ventral offset and dorsal-ventral off-axis loading. The demonstrated approach has several advantages for spinal biomechanical analysis by enabling the examination of the sensitivity of a specimen to multiple variations in shape, and of the interactions between shape, material properties, and loading.

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Describing a craniofacial anomaly: Finite elements and the biometrics of landmark locations

Cited by 64 publications

References 8 publications

Mesh-morphing algorithms for specimen-specific finite element modeling

Mesh-morphing algorithms for specimen-specific finite element modeling

Geometric Morphometrics in Primatology: Craniofacial Variation in Homo sapiens and Pan troglodytes

Mesh Morphing and Response Surface Analysis: Quantifying Sensitivity of Vertebral Mechanical Behavior

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