C David L Thomas

Publications (18)40.05 Total impact

• Article: Variation in osteocyte lacunar morphology and density in the human femur - a synchrotron radiation micro-CT study.

  Yasmin Carter, C David L Thomas, John G Clement, Andrew G Peele, Kevin Hannah, David M L Cooper
  [show abstract] [hide abstract]
  ABSTRACT: In recent years there has been growing interest in the spatial properties of osteocytes (including density and morphology) and how these potentially relate to adaptation, disease and aging. This interest has, in part, arisen from the availability of increasingly high-resolution 3D imaging modalities such as synchrotron radiation (SR) micro-CT. As resolution increases, field of view generally decreases. Thus, while increasingly detailed spatial information is obtained, it is unclear how representative this information is of the skeleton or even the isolated bone. The purpose of this research was to describe the variation in osteocyte lacunar density, morphology and orientation within the femur from a healthy young male human. Multiple anterior, posterior, medial and lateral blocks (2mm×2mm) were prepared from the proximal femoral shaft and SR micro-CT imaged at the Advanced Photon Source. Average lacunar densities (±standard deviation) from the anterior, posterior, medial and lateral regions were 27,169±1935, 26,3643±1262, 37,521±6416 and 33,972±2513 lacunae per mm(3) of bone tissue, respectively. These values were significantly different between the medial and both the anterior and posterior regions (p<0.05). The density of the combined anterior and posterior regions was also significantly lower (p=0.001) than the density of the combined medial and lateral regions. Although no difference was found in predominant orientation, shape differences were found; with the combined anterior and posterior regions having more elongated (p=0.004) and flattened (p=0.045) lacunae, than those of the medial and lateral regions. This study reveals variation in osteocyte lacunar density and morphology within the cross-section of a single bone and that this variation can be considerable (up to 30% difference in density between regions). The underlying functional significance of the observed variation in lacunar density likely relates to localized variations in loading conditions as the pattern corresponds well with mechanical axes. Lower density and more elongate shapes being associated with the antero-posterior oriented neutral axis. Our findings demonstrate that the functional and pathological interpretations that are increasingly being drawn from high resolution imaging of osteocyte lacunae need to be better situated within the broader context of normal variation, including that which occurs even within a single skeletal element.
  Bone 09/2012; 52(1):126-132. · 4.02 Impact Factor
• Article: Endocortical bone loss in osteoporosis: The role of bone surface availability

  Pascal R. Buenzli, C. David L. Thomas, John G. Clement, Peter Pivonka
  [show abstract] [hide abstract]
  ABSTRACT: Age-related bone loss and postmenopausal osteoporosis are disorders of bone remodelling, in which less bone is reformed than resorbed. Yet, this dysregulation of bone remodelling does not occur equally in all bone regions. Loss of bone is more pronounced near and at the endocortex, leading to cortical wall thinning and medullary cavity expansion, a process sometimes referred to as "trabecularisation" or "cancellisation". Cortical wall thinning is of primary concern in osteoporosis due to the strong deterioration of bone mechanical properties that it is associated with. In this paper, we examine the possibility that the non-uniformity of microscopic bone surface availability could explain the non-uniformity of bone loss in osteoporosis. We use a computational model of bone remodelling in which microscopic bone surface availability influences bone turnover rate and simulate the evolution of the bone volume fraction profile across the midshaft of a long bone. We find that bone loss is accelerated near the endocortical wall where the specific surface is highest. Over time, this leads to a substantial reduction of cortical wall thickness from the endosteum. The associated expansion of the medullary cavity can be made to match experimentally observed cross-sectional data from the Melbourne Femur Collection. Finally, we calculate the redistribution of the mechanical stresses in this evolving bone structure and show that mechanical load becomes critically transferred to the periosteal cortical bone.
  06/2012;
• Article: A general few-projection method for tomographic reconstruction of samples consisting of several distinct materials

  Glenn R. Myers, C. David L. Thomas, David M. Paganin, Timur E. Gureyev, John G. Clement
  [show abstract] [hide abstract]
  ABSTRACT: We present a method for tomographic reconstruction of objects containing several distinct materials, which is capable of accurately reconstructing a sample from vastly fewer angular projections than required by conventional algorithms. The algorithm is more general than many previous discrete tomography methods, as: (i) a priori knowledge of the exact number of materials is not required; (ii) the linear attenuation coefficient of each constituent material may assume a small range of a priori unknown values. We present reconstructions from an experimental x-ray computed tomography scan of cortical bone acquired at the SPring-8 synchrotron.
  Applied Physics Letters 01/2010; 96(2):021105-021105-3. · 3.84 Impact Factor
• Source

  Available from: Nigel Loveridge

  Article: Femoral neck trabecular bone: loss with aging and role in preventing fracture.

  C David L Thomas, Paul M Mayhew, Jon Power, Kenneth Es Poole, Nigel Loveridge, John G Clement, Chris J Burgoyne, Jonathan Reeve
  [show abstract] [hide abstract]
  ABSTRACT: Hip fracture risk rises 100- to 1000-fold over six decades of age, but only a minor part of this increase is explained by declining BMD. A potentially independent cause of fragility is cortical thinning predisposing to local crushing, in which bone tissue's material disintegrates at the microscopic level when compressed beyond its capacity to maintain integrity. Elastic instability or buckling of a much thinned cortex might alternatively occur under compression. In a buckle, the cortex moves approximately at right angles to the direction of load, thereby distorting its microstructure, eventually to the point of disintegration. By resisting buckling movement, trabecular buttressing would protect the femoral neck cortex against this type of failure but not against crushing. We quantified the effect of aging on trabecular BMD in the femoral neck and assessed its contribution to cortical elastic stability, which determines resistance to buckling. Using CT, we measured ex vivo the distribution of bone in the midfemoral necks of 35 female and 33 male proximal femurs from cases of sudden death in those 20-95 yr of age. We calculated the critical stress sigma(cr), at which the cortex was predicted to buckle locally, from the geometric properties and density of the cortical zone most highly loaded in a sideways fall. Using long-established engineering principles, we estimated the amount by which stability or buckling resistance was increased by the trabecular bone supporting the most stressed cortical sector in each femoral neck. We repeated these measurements and calculations in an age- and sex-matched series of femoral necks donated by women who had suffered intracapsular hip fracture and controls, using histological measurements of cortical thickness to improve accuracy. With normal aging, trabecular BMD declined asymmetrically, fastest in the supero-lateral one-half (in antero-posterior projection) of the trabecular compartment. When viewed axially with respect to the femoral neck, the most rapid loss of trabecular bone occurred in the posterior part of this region (supero-posterior [S-P]), amounting to a 42% reduction in women (34% in men) over five decades of adult age. Because local cortical bone thickness declined comparably, age had no significant effect on the relative contributions of cortical and trabecular bone to elastic stability, and trabecular bone was calculated to contribute 40% (in men) and 43% (in women) to the S-P cortex of its overall elastic stability. Hip fracture cases had reduced elastic stability compared with age-matched controls, with a median reduction of 49% or 37%, depending on whether thickness was measured histologically or by CT (pQCT; p < 0.002 for both). This effect was because of reduced cortical thickness and density. Trabecular BMD was similar in hip fracture cases and controls. The capacity of the femur to resist fracture in a sideways fall becomes compromised with normal aging because cortical thickness and trabecular BMD in the most compressed part of the femoral neck both decline substantially. This decline is relatively more rapid than that of femoral neck areal BMD. If elastic instability rather than cortical crushing initiates the fracture event, interventions that increase trabecular bone in the proximal femur have great potential to reduce fracture risk because the gradient defining the increase in elastic stability with increasing trabecular BMD is steep, and most hip fracture cases have sufficient trabecular bone for anabolic therapies to build on.
  Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 05/2009; 24(11):1808-18. · 6.04 Impact Factor
• Article: The relation of femoral osteon geometry to age, sex, height and weight.

  Hayley M Britz, C David L Thomas, John G Clement, David M L Cooper
  [show abstract] [hide abstract]
  ABSTRACT: As computational modeling becomes an increasingly common tool for probing the regulation of bone remodeling, the need for experimental data to refine and validate such models also grows. For example, van Oers et al. (R.F. van Oers, R. Ruimerman, B. van Rietbergen, P.A. Hilbers, R. Huiskes, Relating osteon diameter to strain. Bone 2008;43: 476-482.) recently described a mechanism by which osteon size may be regulated (inversely) by strain. Empirical data supporting this relation, particularly in humans, are sparse. Therefore, we sought to determine if there is a link between body weight (the only measure related to loading available for a cadaveric population) and osteon geometry in human bone. We hypothesized that after controlling for age, sex and height, weight would be inversely related to femoral osteon size (area, On.Ar; diameter, On.Dm). Secondarily we sought to describe the relation between osteon circularity (On.Cr) and these parameters. Osteons (n=12,690) were mapped within microradiographs of femoral mid-diaphyseal specimens (n=88; 45 male, 43 female; 17-97 yrs). Univariate analysis of covariance was conducted (n=87; 1 outlier) with sex as a fixed factor and height, weight and log-transformed age as covariates. Weight was negatively related to On.Ar and On.Dm (p=0.006 and p=0.004, respectively). Age was significantly related to osteon and, it was also significantly related to circularity (all p<0.001). This relation was negative for On.Ar and On.Dm and positive for On.Cr (increasing circularity with age). On.Ar and On.Dm were found to be significantly different between the sexes (p=0.021 and p=0.019, respectively), with females having smaller osteons. No relation between sex and On.Cr was detected (p=0.449). Height was not significantly related to any of the geometric parameters. Partial eta-squared values revealed that age accounted for the largest proportion (On.Ar: 28%, On.Dm: 18%, On.Cr: 30%), weight accounted for the second largest (On.Ar: 9%, On.Dm: 10%) and sex accounted for the smallest proportion (On.Ar: 6%, On.Dm: 7%) of the variance in geometry. While previous studies have reported relations between osteon size and sex/age, we believe that our findings are the first to demonstrate a link with weight. We believe that this negative relation with weight is most probably mechanical in nature; however, alternative (endocrine) links between bone and adipose tissue cannot be ruled out by our design.
  Bone 03/2009; 45(1):77-83. · 4.02 Impact Factor
• Article: Collagen turnover in the adult femoral mid-shaft: modeled from anthropogenic radiocarbon tracer measurements.

  Robert E M Hedges, John G Clement, C David L Thomas, Tamsin C O'connell
  [show abstract] [hide abstract]
  ABSTRACT: We have measured the (14)C content of human femoral mid-shaft collagen to determine the dynamics of adult collagen turnover, using the sudden doubling and subsequent slow relaxation of global atmospheric (14)C content due to nuclear bomb testing in the 1960s and 1970s as a tracer. (14)C measurements were made on bone collagen from 67 individuals of both sexes who died in Australia in 1990-1993, spanning a range of ages at death from 40 to 97, and these measurements were compared with values predicted by an age-dependent turnover model. We found that the dataset could constrain models of collagen turnover, with the following outcomes: 1) Collagen turnover rate of females decreases, on average, from 4%/yr to 3%/yr from 20 to 80 years. Male collagen turnover rates average 1.5-3%/yr over the same period. 2) For both sexes the collagen turnover rate during adolescent growth is much higher (5-15%/yr at age 10-15 years), with males having a significantly higher turnover rate than have females, by up to a factor of 2. 3) Much of the variation in residual bomb (14)C in a person's bone can be attributed to individual variation in turnover rate, but of no more than about 30% of the average values for adults. 4) Human femoral bone collagen isotopically reflects an individual's diet over a much longer period of time than 10 years, including a substantial portion of collagen synthesised during adolescence.
  American Journal of Physical Anthropology 06/2007; 133(2):808-16. · 2.82 Impact Factor
• Article: Age-dependent change in the 3D structure of cortical porosity at the human femoral midshaft.

  David M L Cooper, C David L Thomas, John G Clement, Andrei L Turinsky, Christoph W Sensen, Benedikt Hallgrímsson
  [show abstract] [hide abstract]
  ABSTRACT: Microstructural change associated with cortical bone remodeling has been extensively explored with 2D techniques. However, relatively little is known regarding the 3D dynamic microstructure of cortical bone. Therefore, we employed micro-CT imaging to investigate 3D remodeling-related change in the structure of cortical bone porosity across the human lifespan. Anterior femoral midshaft specimens (n=51 male, 28 female) spanning 18 to 92 years of age were scanned with 7 mum nominal isotropic resolution. Canal volume fraction (Ca.V/TV), mean diameter (Ca.Dm), mean separation (Ca.Sp), degree of anisotropy (DA), connectivity density (Ca.ConnD), and number (Ca.N) were calculated for subperiosteal cylindrical regions of interest. Ca.N was calculated in 2D (Ca.N(2D)) and 3D (Ca.N(3D)). Regression was used to examine the relation between the structural parameters and age. Additionally, the impact of sex, height, and weight were investigated collectively (MANCOVA) and individually (ANCOVA). For all analyses, Ca.V/TV and Ca.Dm were inverted (Ca.V/TV(-1), Ca.Dm(-1)) to establish normality and linear relations with age. Ca.N values (2D and 3D) were non-linearly (quadratic) related to age, increasing until the 6th decade then decreasing. This relation was only significant for the pooled sexes Ca.N(3D) values (p=0.012). Ca.ConnD was positively related to age (p<0.05), while all remaining 3D parameters, except DA for males (p=0.070), were negatively related (p<0.05). In all cases, the relation with age was strongest for females. MANCOVA revealed that age was the only significant (p<0.001) covariate overall. Univariate ANCOVA indicated significant differences between the sexes for Ca.V/TV(-1) and Ca.Dm(-1) (p=0.018 and 0.010, respectively). Relative to males, females had lower values for these parameters, translating into larger mean canal diameter and overall porosity. Body weight had a significant (p=0.043) positive relation with Ca.Dm(-1), indicating lower weight was also associated with increased mean canal diameter. Therefore, while age was the most important factor, sex and body size were found to play a role in parameters related to canal size and the overall level of porosity. This study is unique in that changes in cortical bone microstructure were examined across the adult human lifespan in three rather than two dimensions.
  Bone 05/2007; 40(4):957-65. · 4.02 Impact Factor
• Article: Increase in pore area, and not pore density, is the main determinant in the development of porosity in human cortical bone.

  C David L Thomas, Sophie A Feik, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: This study investigated the relative contributions of pore size and pore density (number of pores per mm2) to porosity in the midshaft of the human femur. Cross-sections were obtained from 168 individuals from a modern Australian population (mostly Anglo-Celtic). The study group comprised 73 females and 95 males, aged from 20 to 97 years. Microradiographs were made of 100-microm sections and porosity, pore areas and pore densities determined using image processing software. The cortex was divided into three rings radially and into octants circumferentially, and the porosity, pore area and pore density of each segment were calculated. Results show that 81% of the variance in porosity can be explained by changes in mean pore area with only a further 12-16% explained by changes in pore density. These effects were found to be constant across all areas of the cortex and in both sexes. These results are significant in their consistency and ordered gradation and indicate a well-regulated and systematic process of bone removal with ageing. The results show a regular progression from less porous to more porous bone; this is a uniform process that occurs in all individuals, and factors such as sex and rate of ageing determine where on this continuum any individual is at a particular time.
  Journal of Anatomy 09/2006; 209(2):219-30. · 2.37 Impact Factor
• Article: Three-dimensional microcomputed tomography imaging of basic multicellular unit-related resorption spaces in human cortical bone.

  David M L Cooper, C David L Thomas, John G Clement, Benedikt Hallgrímsson
  [show abstract] [hide abstract]
  ABSTRACT: This study employed microcomputed tomography (micro-CT) as a novel means for visualizing the morphology and quantifying the range (length) of basic multicellular unit (BMU)-related resorption spaces in human cortical bone. We tested the hypotheses that the density and range of spaces vary with age and sex. The sample included 82 human (18-92 years) anterior femoral midshaft samples. The morphology of the spaces (n = 99) was varied, including unidirectional, bidirectional, branched, and even highly clustered forms. The density of resorption spaces was negatively correlated with age for the combined sexes and females, with Spearman's rho values of -0.355 (P < 0.001) and -0.522 (P = 0.002), respectively. The density of spaces did not differ significantly between the sexes (P = 0.735). Mean range +/- SD for the combined sexes, females, and males was 2,706 +/- 1,177, 2,681 +/- 1,247, and 2,718 +/- 1,150 microm, respectively. Numerical simulation of the effect of the 7,000 microm scan field of view suggested that the actual mean range of the spaces for the pooled sample was actually on the order of 3,770 microm. Range did not correlate significantly with age for the combined sexes (P = 0.587) or females (P = 0.345) and males (P = 0.896) considered separately and was not significantly different (P = 0.883) between the sexes. These results suggest that the range of BMUs is not affected by age. The age-dependent decrease in resorption space density for the females and pooled sexes was most likely a consequence of cortical rarefaction, leading to difficulty detecting resorption spaces with micro-CT, rather than a decrease in overall remodeling activity.
  The Anatomical Record Part A Discoveries in Molecular Cellular and Evolutionary Biology 07/2006; 288(7):806-16.
• Article: Three‐dimensional microcomputed tomography imaging of basic multicellular unit‐related resorption spaces in human cortical bone

  David M.L. Cooper, C. David L. Thomas, John G. Clement, Benedikt Hallgrímsson
  [show abstract] [hide abstract]
  ABSTRACT: This study employed microcomputed tomography (micro-CT) as a novel means for visualizing the morphology and quantifying the range (length) of basic multicellular unit (BMU)-related resorption spaces in human cortical bone. We tested the hypotheses that the density and range of spaces vary with age and sex. The sample included 82 human (18–92 years) anterior femoral midshaft samples. The morphology of the spaces (n = 99) was varied, including unidirectional, bidirectional, branched, and even highly clustered forms. The density of resorption spaces was negatively correlated with age for the combined sexes and females, with Spearman's rho values of −0.355 (P < 0.001) and −0.522 (P = 0.002), respectively. The density of spaces did not differ significantly between the sexes (P = 0.735). Mean range ± SD for the combined sexes, females, and males was 2,706 ± 1,177, 2,681 ± 1,247, and 2,718 ± 1,150 μm, respectively. Numerical simulation of the effect of the 7,000 μm scan field of view suggested that the actual mean range of the spaces for the pooled sample was actually on the order of 3,770 μm. Range did not correlate significantly with age for the combined sexes (P = 0.587) or females (P = 0.345) and males (P = 0.896) considered separately and was not significantly different (P = 0.883) between the sexes. These results suggest that the range of BMUs is not affected by age. The age-dependent decrease in resorption space density for the females and pooled sexes was most likely a consequence of cortical rarefaction, leading to difficulty detecting resorption spaces with micro-CT, rather than a decrease in overall remodeling activity. Anat Rec Part A, 288A:806–816, 2006. © 2006 Wiley-Liss, Inc.
  The Anatomical Record Part A Discoveries in Molecular Cellular and Evolutionary Biology 06/2006; 288A(7):806 - 816.
• Article: Effects of tensioning the lumbar fasciae on segmental stiffness during flexion and extension: Young Investigator Award winner.

  Priscilla J Barker, Katharine T Guggenheimer, Ivica Grkovic, Christopher A Briggs, Daniel C Jones, C David L Thomas, Paul W Hodges
  [show abstract] [hide abstract]
  ABSTRACT: Biomechanical study of unembalmed human lumbar segments. To investigate the effects of tensioning the lumbar fasciae (transversus abdominis [TrA]) aponeurosis) on segment stiffness during flexion and extension. Animal and human studies suggest that TrA may influence intersegmental movement via tension in the middle and posterior layers of lumbar fasciae (MLF, PLF). Compressive flexion and extension moments were applied to 17 lumbar segments from 9 unembalmed cadavers with 20 N lateral tension of the TrA aponeurosis during: 1) "static" tests: load was compared when fascial tension was applied during static compressive loads into flexion-extension; 2) "cyclic loading" tests: load, axial displacement, and stiffness were compared during repeated compressive loading cycles into flexion-extension. After testing, the PLF was incised to determine the tension transmitted by each layer. At all segments and loads (<200 N), fascial tension increased resistance to flexion loads by approximately 9.5 N. In 15 of 17, fascial tension decreased resistance to extension by approximately 6.6 N. Fascial tension during cyclic flexion loading decreased axial displacement by 26% at the onset of loading (0-2 N) and 2% at 450 N (13 of 17). During extension loading, fascial tension increased displacement at the onset of loading (10 of 17) by approximately 23% and slightly (1%) decreased displacement at 450 N. Segment stiffness was increased by 6 N/mm in flexion (44% at 25 N) and decreased by 2 N/mm (8% at 25 N) in extension. More than 85% of tension was transmitted through the MLF. Tension on the lumbar fasciae simulating moderate contraction of TrA affects segmental stiffness, particularly toward the neutral zone.
  Spine 03/2006; 31(4):397-405. · 2.08 Impact Factor
• Article: Regional variation of intracortical porosity in the midshaft of the human femur: age and sex differences.

  C David L Thomas, Sophie A Feik, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: This study investigated age and sex differences in patterns of porosity distribution in the midshaft of the human femur. Cross-sections were obtained from 168 individuals from a modern Australian population. The sample comprised 73 females and 95 males, aged between 20 and 97 years. Microradiographs were made of 100-microm sections and pore and bone areas were determined using image processing software. Initially the sample was divided by age: young (20-44 years), middle (45-64 years) and old (65+ years), but it was found that analysis on the basis of the ratio of medullary area to total subperiosteal area gave clearer results. The cortex was divided into three rings radially and into octants circumferentially and the porosity of each segment was calculated. Results showed that a pattern with raised porosity in the posterior and anterolateral regions, and with greater porosity in the inner parts of the cortex, becomes more pronounced with age. In males this pattern develops steadily; in females there are much greater differences between the middle and older groups than earlier in life. The patterns observed are consistent with progressive bone loss occurring along a neutral axis of the cortex where bending stress is lowest and the mechanical advantage of the bone is least.
  Journal of Anatomy 03/2005; 206(2):115-25. · 2.37 Impact Factor
• Article: Delineation of facial archetypes by 3d averaging.

  Ashraf I Shaweesh, C David L Thomas, Agnes Bankier, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: The objective of this study was to investigate the feasibility of creating archetypal 3D faces through computerized 3D facial averaging. A 3D surface scanner Fiore and its software were used to acquire the 3D scans of the faces while 3D Rugle3 and locally-developed software generated the holistic facial averages. 3D facial averages were created from two ethnic groups; European and Japanese and from children with three previous genetic disorders; Williams syndrome, achondroplasia and Sotos syndrome as well as the normal control group. The method included averaging the corresponding depth (z) coordinates of the 3D facial scans. Compared with other face averaging techniques there was not any warping or filling in the spaces by interpolation; however, this facial average lacked colour information. The results showed that as few as 14 faces were sufficient to create an archetypal facial average. In turn this would make it practical to use face averaging as an identification tool in cases where it would be difficult to recruit a larger number of participants. In generating the average, correcting for size differences among faces was shown to adjust the average outlines of the facial features. It is assumed that 3D facial averaging would help in the identification of the ethnic status of persons whose identity may not be known with certainty. In clinical medicine, it would have a great potential for the diagnosis of syndromes with distinctive facial features. The system would also assist in the education of clinicians in the recognition and identification of such syndromes.
  Annals of the Royal Australasian College of Dental Surgeons 11/2004; 17:73-9.
• Article: A Japanese computer-assisted facial identification system successfully identifies non-Japanese faces.

  Natalie L Fraser, Mineo Yoshino, Kazuhiko Imaizumi, Sherie A Blackwell, C David L Thomas, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: The method developed by Yoshino et al. in [Forensic Sci. Int. 109 (2000) 225 and Jpn. J. Sci. Tech. Iden. 5 (2000) 9] and already being applied in Japan utilizes a three-dimensional (3D) physiognomic rangefinder combined with a computer-assisted superimposition system. Facial outlines can be compared between two-dimensional (2D) surveillance images and data extracted from 3D images obtained from the rangefinder. Also, the loci of potentially concordant features can be compared and differences measured. The method is largely objective and gives statistics for false positive/false negative findings. This recently developed method by Yoshino et al. is currently being introduced to the Japanese courts. To enable courts outside Japan to assess the admissibility of this new method, studies of non-Japanese faces have been undertaken and shown to produce similar low error rates. The present authors, therefore, consider the Yoshino method to be applicable in a non-Japanese context. As part of this study a comparison of morphological features between two ethnic groups has been undertaken using 3D measurements for the first time and will serve as the foundation for an anthropological database in the future.
  Forensic Science International 09/2003; 135(2):122-8. · 2.30 Impact Factor
• Article: Lateral facial soft-tissue prediction model: analysis using Fourier shape descriptors and traditional cephalometric methods.

  Adam D Rose, Michael G Woods, John G Clement, C David L Thomas
  [show abstract] [hide abstract]
  ABSTRACT: This study was designed to investigate the relationship between traditional skeletal cephalometric measurement and Fourier analysis of the lateral soft-tissue profile. A random sample of 121 untreated subjects of European descent, with wide ranges of malocclusions and underlying facial patterns, was selected in the Orthodontic Unit at the University of Melbourne. Lateral cephalograms were available for all subjects. Both traditional lateral cephalometric analysis and Fourier soft-tissue profile analysis were carried out. Multivariate statistical analysis among 11 hard-tissue cephalometric measurements and the first 50 Fourier harmonics was then performed. This analysis formed the basis for a subsequently proposed soft-tissue prediction model. From this model, 50 predicted x- and y-harmonics were generated for each subject in the total sample. Calculation of Pearson's correlation coefficients between the actual and predicted harmonics revealed strong relationships for many of the lower-order harmonics. To further test the model, the prediction-coefficients derived from all 121 subjects were then used to make predictions for the first 50 x- and y-harmonics for a subgroup of 10 independent test subjects. Once again, Pearson's correlations between the actual and predicted harmonics of the test model in the lower-order harmonics revealed strong associations. Superimposition of the actual and predicted soft-tissue outlines, however, revealed that much actual detail in the region between the nose and the chin was still lost using the predicted Fourier harmonics. This suggests that soft-tissue prediction based on this Fourier test model, while already useful in Forensic facial reconstruction, may not yet be appropriate for useful diagnosis and planning in clinical disciplines.
  American Journal of Physical Anthropology 07/2003; 121(2):172-80. · 2.82 Impact Factor
• Source

  Available from: mcphu.edu

  Article: Preferred collagen fiber orientation in the human mid-shaft femur.

  Haviva M Goldman, Timothy G Bromage, C David L Thomas, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: Collagen fiber orientation is one aspect of the microstructure of bone that influences its mechanical properties. While the spatial distribution of preferentially oriented collagen is hypothesized to reflect the effects of loading during the process of aging, its variability in a modern human sample is essentially unknown. In a large sample (n = 67) of autopsied adults, the variability of collagen fiber orientation in the mid-shaft femur was examined in relation to age and sex. Montaged images of entire 100 microm thick cross-sections were obtained using circularly polarized light microscopy (CPLM) under standardized illuminating conditions. An automated image-analyzing routine divided images into 48 segments according to anatomical position. Average gray values (varying with orientation) were quantified for each segment, and one-way ANOVA with Tukey HSD post hoc tests were applied to assess differences between segments. Collagen fiber orientation appeared to be nonrandomly distributed across the mid-shaft femur sample; however, no single "human" pattern was identified. Individual variation, unexplainable by age, sex, or body size, exceeded population-level trends. Differences between age and sex groups suggest there is a strong correspondence between collagen fiber orientation and tissue-type distributions. The minimal consistencies demonstrated here may reflect mechanical forces induced at the femoral mid-shaft. However, the myriad of other factors that may influence collagen fiber orientation patterning, including growth trajectories, metabolic and nutritional status, and disease states, must be explored further. Only then, in conjunction with studies of other structural and material properties of bone, will we be able to elucidate the linkages between microstructure and functional adaptation in the human mid-shaft femur.
  The Anatomical Record Part A Discoveries in Molecular Cellular and Evolutionary Biology 06/2003; 272(1):434-45.
• Article: Individual identification of disguised faces by morphometrical matching.

  Mineo Yoshino, Kasumi Noguchi, Masaru Atsuchi, Satoshi Kubota, Kazuhiko Imaizumi, C David L Thomas, John G Clement
  [show abstract] [hide abstract]
  ABSTRACT: The reliability of a morphometrical matching method for identifying disguised faces was examined experimentally using a computer-assisted facial image identification system. The 2D right oblique facial images of three target persons disguised with sunglasses, cap and gauze mask were each compared with each of the 3D facial images of 100 subjects, yielding 900 face-to-face superimpositions. The average perpendicular distance between the facial outlines and the average point-to-point distance of the corresponding landmarks in the 2D image of the disguised face and the 3D facial image, were calculated. As a matching criterion, the sum of the values of the average perpendicular difference of the facial outlines and the average point-to-point difference between the corresponding landmarks was used (abbreviation: average difference). The range of the average difference was 2.3-2.8mm for the same person (a match) and 4.0-14.6mm for different (non-matching) people, respectively. The ranges for matching and non-matching faces did not overlap. Even the 3D facial images of the non-matching person showing the closest value of average difference to the average difference for the matching person could be excluded easily. It was concluded that the morphometrical matching method can reliably identify disguised faces and the results produced by this method could be easily understandable by a court of law.
  Forensic Science International 07/2002; 127(1-2):97-103. · 2.30 Impact Factor
• Article: Assessing growth and development of the facial profile.

  Wina E Darwis, Louise B Messer, C David L Thomas
  [show abstract] [hide abstract]
  ABSTRACT: The study of growth and development of the facial profile is of interest to clinicians and researchers in the fields of pediatric dentistry, orthodontics, and craniofacial surgery, enabling diagnosis, planning, and evaluation of treatment. Until recently, craniofacial studies addressed facial growth, facial asymmetry, and gender differences by examining changes in size. However, size changes alone do not represent fully the complicated process of craniofacial growth which also involves changes in shape. The shape of the facial profile can now be quantified with Fourier analysis, contributing to a better understanding of growth. A combination of recently developed methods, such as 3-dimensional facial morphometry and Fourier analysis, should allow a more comprehensive knowledge of growth and development of the craniofacial structures, including the facial profile. This article examines various methods for assessing facial growth and development currently available with particular reference to the facial profile, and addresses the value of Fourier analysis in assessing shape changes.
  Pediatric dentistry 25(2):103-8. · 1.02 Impact Factor