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E Lespessailles

Publications and source records attributed to E Lespessailles.

18 recordsLinked to original sources
PubMed2001

Fractal analysis of radiographic trabecular bone texture and bone mineral density: two complementary parameters related to osteoporotic fractures.

Trabecular bone microarchitecture and bone mineral density (BMD) are two main factors related to osteoporotic fractures. Currently, however, microarchitecture is not evaluated. We have developed and validated a trabecular bone texture analysis from radiographic images. The objective was to determine if the fractal analysis of texture was able to distinguish osteoporotic fracture groups from control groups, either in vertebrae, hip, or wrist fractures, and to determine if this indicator and BMD were independent and complementary. In this cross-sectional unicenter case-control population study in postmenopausal women, 107 fracture cases were enrolled and age-matched with 197 control cases. This population comprised 40 vertebral fractures (with 70 controls), 30 hip fractures (55 controls), and 37 wrist fractures (62 controls). Hip and lumbar spine BMD were measured by double-energy X-ray absorptiometry. Fractal analysis of texture was performed on calcaneus radiographs and the result was expressed as the H parameter (H = 2-fractal dimension). The H parameter showed a lower value (0.679 +/- 0.053 SD) in fracture cases versus control cases (0.696 +/- 0.030; p = 0.007), the statistical significance persisting after adjustment for age and for lumbar spine (LS) or hip BMD. This result was confirmed in vertebral fractures (p = 0.0001) and hip fractures (p = 0.003) but not wrist fractures (p = 0.07). We determined the threshold between high and low H values and then the odds ratios (OR) of fracture for low H for BMD < or = -2.5 SD in T score and for the combinations of both parameters. The OR of fracture for low H was 1.6 (95% CI, 1.1-2.6). For LS BMD < or = -2.5 SD the OR of 6.1 (3.4-10.8) shifted to 9.0 (4.0-20.4) when we added low H and for hip BMD it shifted from 5.6 (3.3-9.4) to 8.1 (4.0-16.8). In vertebral, hip, and wrist fracture cases the results were also significant. These data have shown that the fractal analysis of texture on calcaneus radiographs can distinguish osteoporotic fracture groups from control groups. This analysis and BMD provide independent and complementary information. These data suggest that we can improve the fracture risk evaluation by adding information related to microarchitecture, derived from analysis of conventional radiographic images.

Absorptiometry, Photon↗
PubMed2000

A new method for three-dimensional skeleton graph analysis of porous media: application to trabecular bone microarchitecture.

This paper introduces a new three-dimensional analysis of complex disordered porous media. Skeleton graph analysis is described and applied to trabecular bone images obtained by high resolution magnetic resonance imaging. This technique was developed bearing in mind topological considerations. The correspondence between vertices and branches of the skeleton graph and trabeculae is used in order to get local information on trabecular bone microarchitecture. In addition to real topological parameters, local structural information about trabeculae, such as length and volume distributions, are obtained. This method is applied to two sets of samples: six osteoporosis and six osteoarthritis bone samples. We demonstrate that skeleton graph analysis is a powerful technique to describe trabecular bone microarchitecture.

Femur Head↗
PubMed2000

Fractal dimension of trabecular bone projection texture is related to three-dimensional microarchitecture.

The purpose of this work was to understand how fractal dimension of two-dimensional (2D) trabecular bone projection images could be related to three-dimensional (3D) trabecular bone properties such as porosity or connectivity. Two alteration processes were applied to trabecular bone images obtained by magnetic resonance imaging: a trabeculae dilation process and a trabeculae removal process. The trabeculae dilation process was applied from the 3D skeleton graph to the 3D initial structure with constant connectivity. The trabeculae removal process was applied from the initial structure to an altered structure having 99% of porosity, in which both porosity and connectivity were modified during this second process. Gray-level projection images of each of the altered structures were simply obtained by summation of voxels, and fractal dimension (Df) was calculated. Porosity (phi) and connectivity per unit volume (Cv) were calculated from the 3D structure. Significant relationships were found between Df, phi, and Cv. Df values increased when porosity increased (dilation and removal processes) and when connectivity decreased (only removal process). These variations were in accordance with all previous clinical studies, suggesting that fractal evaluation of trabecular bone projection has real meaning in terms of porosity and connectivity of the 3D architecture. Furthermore, there was a statistically significant linear dependence between Df and Cv when phi remained constant. Porosity is directly related to bone mineral density and fractal dimension can be easily evaluated in clinical routine. These two parameters could be associated to evaluate the connectivity of the structure.

Femur Head↗
PubMed2000

Long-term corticosteroid therapy induces mild changes in trabecular bone texture.

The relative roles of bone mineral density (BMD) decrease and of microarchitectural changes in corticosteroid-induced osteoporosis (CIOP) are debated. Our objective has been to evaluate both bone microarchitecture (by a fractal analysis of texture on radiographs) and BMD in corticosteroid (CS)-treated patients. In this study, 60 patients from a rheumatology unit with a mean age of 60.6+/-14.8 years taking CS therapy for more than 6 months and a cumulative dose of prednisone over 1 g and 57 controls among age-matched patients and hospital staff were recruited. Bone diseases and bone-modifying drugs (except calcium, vitamin D, and hormonal replacement therapy [HRT]) were considered as exclusion criteria. A fractal analysis of trabecular bone texture was performed on calcaneus radiographs after an oriented analysis in 18 directions. The fractal analysis was based on the fractional Brownian motion model. Results were expressed by H parameter (H = 2 - fractal dimension) in each direction, Hmean being the average of 18 directions, Hmini the minimum, and Hmaxi the maximum. BMD was measured by double-energy X-ray absorptiometry (DEXA) at the femoral neck (FN) and lumbar spine (LS). The odds ratios (OR) were calculated for a variation of 1 SD. The mean duration and dose of CS therapy was 5.6+/-6.6 years and 16.9+/-19.7 g. CS therapy was significantly correlated to a decrease in FN or LSBMD: OR = 1.95, 95% confidence interval (CI, 1.29-2.97) and OR = 3.19 (CI, 1.80-5.66), respectively. The Hmean and Hmaxi were significantly lower in the cases than in the controls: P = 0.03 and P = 0.02; OR = 1.67 (CI, 1.10-2.54) and OR = 1.75 (CI, 1.05-2.37). A similar trend was observed with Hmini but the difference did not reach the level of statistical significance: P = 0.06, OR = 1.57 (CI, 1.05-2.37). This study was repeated among cases and controls who had never taken HRT (respectively, n = 40 and n = 39). The results were similar. Among patients taking CS therapy, the presence of nontraumatic fractures was inversely related to BMD values but not to texture parameters. These data have shown that long-term CS therapy induces both BMD decrease and trabecular bone texture changes. The effect of CS therapy was much stronger on BMD than on the fractal H parameter. These results are in accordance with previous studies showing a lower effect of CS therapy on bone microarchitecture than on bone mass. These results can be contrasted with those observed in women with postmenopausal osteoporosis and vertebral crush fractures in which the variations in the fractal parameters are more significant than the BMD variations.

Adrenal Cortex Hormones↗
PubMed2000

Glucocorticoid-induced osteoporosis: is the bone density decrease the only explanation?

BACKGROUND: Glucocorticoids may increase bone fragility via mechanisms independent from their bone mass reducing effect. OBJECTIVE: To study relationships between osteoporotic fractures and bone mineral density in patients on long-term glucocorticoid therapy. PATIENTS AND METHODS: We studied 121 women with a mean age of 60.4 +/- 14.3 years on long-term glucocorticoid therapy (cumulative dose > or = 1 g of prednisone equivalent, duration > or = 6 months) for rheumatoid arthritis (n = 38), polymyalgia rheumatica or giant cell arteritis (n = 26), connective tissue disease (n = 15), asthma (n = 14), another inflammatory joint disease (n = 14), or another condition (n = 14). The control group was composed of 125 subjects who had the same mean age and met the same exclusion criteria as the case group. Bone mineral density was measured at the lumbar spine and femoral neck using a Hologic QDR 4500 unit. In subjects with back pain, radiographs of the thoracic and lumbar spine were obtained to look for fractures. RESULTS: The odds ratio for a bone mineral density decrease of one standard deviation at the femoral neck was 1.68 (1.20-2.35) in patients with a cumulative glucocorticoid dose of 10 g of prednisone equivalent and 1.67 (1.22-2.29) in those with a glucocorticoid therapy duration of 2 years. Sixty-eight fractures were recorded in 56 patients (46% of the overall patient group). Even after adjustment on age, glucocorticoid therapy duration, and dose, mean bone mineral density values at the lumbar spine and femoral neck were significantly lower in the subgroup of patients with fractures than in the subgroup without fractures. Sensitivity and specificity of bone mineral density at the femoral neck and/or lumbar spine for the diagnosis of vertebral fracture and/or peripheral fracture were 73% and 51%, respectively. In the stepwise logistic regression model, factors explaining the presence of fractures were as follows, in hierarchical order: age; absence of calcium/vitamin D supplementation, femoral neck T-score, and glucocorticoid dose. CONCLUSION: Our data are compelling evidence that bone mineral density is a major determinant of the fracture risk in patients with glucocorticoid-induced osteoporosis.

Bone Density↗
PubMed1999

Skull bone mass deficit in prepubertal highly-trained gymnast girls.

It is known that impact loading sport can increase the bone mineral density in the stressed sites of the skeleton in athletes. However, non weight-bearing sites are seldom studied in healthy young girl athletes. In order to study the effects of a long term intensive training on the non-stressed region of the skeleton (skull), we investigated both highly-trained girl athletes, involved in sports requiring or not significant impact loading on the skeleton and a girl control group. Bone mineral content (BMC) and density (BMD) were measured in the whole body, at lumbar spine, femoral neck, trochanter, Ward's triangle, radius, head and ribs, in 60 prepubertal girls including 12 swimmers, 32 gymnasts and 16 controls. Measurements were made by DXA. There were no statistical differences between the groups as regards age, height, body weight, body mass index, lean tissue mass and dietary calcium intake. Mean BMD in gymnasts was statistically higher than in other groups for radius (p < 0.001), femoral neck (p < 0.05) and Ward's triangle (p < 0.05) while there was no difference between swimmers and controls. Head BMC was significantly lower in gymnasts compared to other groups (241.9+/-41 g vs. 285.8+/-34.7 g and 291.1+/-50.2 g respectively in swimmers and controls, p < 0.001). The same observation was made for head BMD (p < 0.01). When body weight was used as a covariant, the contribution of the head BMC to the whole body was significantly lower (p < 0.001) in gymnasts (24.97%) than in swimmers (27.88%) and controls (27.77%). When compared between groups, the slopes of the regressions for head/whole body BMC or BMD were significantly lower in gymnasts (p < 0.05) than in other groups. These data suggest that in prepubertal children the increased bone density induced by gymnastic training in the stressed sites of the body could be related to a decreased skull bone mass.

Bone Density↗
PubMed1999

Bone material acquisition and somatic development in highly trained girl gymnasts.

The present study was conducted to investigate both skeletal and somatic developments in a group of highly trained prepubertal girl gymnasts at the beginning of their peak bone mass acquisition. The experimental group included 14 gymnasts who had trained 12-15 h per wk for 3 y before starting the study. The control group consisted of 15 non-exerciser children and 6 swimmers training for 5-6 h/wk. Body composition and bone mineral density (BMD) of the total body, lumbar spine, non-dominant hip and radius were measured using dual-energy X-ray absorptiometry. Calculation of bone age and measurement of body height and weight were done. All measurements and analyses were carried out twice with a 1-y interval by the same technician. There were no differences between groups in age, bone age, body height and weight and lean tissue mass at the start of the study and 1 y later. The somatic changes observed between the first and second years tended to be greater in gymnasts compared to controls, except for body height. At the first and second investigations, BMD values in the gymnasts were statistically higher than in the controls at all skeletal sites, but not for the whole body (from p < 0.05 to p < 0.001, depending on the site). Percentage changes in BMD pre-investigation compared with post-investigation tended to be greater in gymnasts. Variations in lean mass, bone age and fat mass were found to be the best independent predictors of annual changes in BMD for total body, lumbar spine, trochanter and femoral neck sites. These results suggested that high-volume impact loading training could promote a higher annual gain in bone mineral acquisition at the strained body sites in prepubertal girls without affecting somatic growth dimensions.

Body Height↗
PubMed1999

Long-term reproducibility optimization of an x-ray process for bone architectural evaluation during osteoporosis.

Non-invasive and in vivo assessment of bone architectural changes at high resolution is of considerable interest in osteoporosis. In this note, the use of an x-ray acquisition system in the evaluation of the architectural quality of trabecular bone by radiographic texture analysis is optimized to achieve good long-term reproducibility. First, radiographic and digitization processes are modelled and defined. Procedures to make radiographs and their digital images are fixed. Then, measurements of the modulation transfer function (MTF) of the entire acquisition chain were completed. These measurements provide an MTF in excess of 30% at a spatial frequency of 2.5 lp/mm. Also, results of a fractal texture analysis made on digital images of calcaneus radiographs show a mean coefficient of variation of 2.07%. These data show that good long-term reproducibility can make the x-ray acquisition system efficient for patient follow-up, or evaluation of treatment regimes for osteoporosis. Finally, it is shown that fractal texture parameters are statistically different in an osteoporotic population and in a control group. Therefore, this system should also be of medical interest.

Bone and Bones↗
PubMed1999

Alternaria infection of the skin and joints. A report of two cases involving the hand.

Alternaria is a fungus that is usually saprophytic but occasionally causes skin infections. Involvement of other structures is exceedingly rare. We report two cases in which a joint was also affected. The possible precipitating role of intraarticular glucocorticoid therapy is discussed. Both patients achieved a full recovery after itraconazole therapy, given for 12 and seven months, respectively.

Adult↗
PubMed1998

Effect of physical training on bone mineral density in prepubertal girls: a comparative study between impact-loading and non-impact-loading sports.

Physical activity is known to have an anabolic effect on bone tissue. It has been shown to increase the bone mineral density (BMD) in young adults, as well as in teenagers. But there is little information about the effect of intensive physical activity in childhood, particularly at the prepubertal stage. To examine the influence of an early intensive physical training on BMD, we have studied a group of elite prepubertal girls, at the starting phase of their peak bone mass acquisition. Subjects were engaged either in sport requiring significant impact loading on the skeleton, or in sport without impact loading. Forty-one healthy prepubertal girls took part in this study. The sport group consisted of 10 swimmers (10.5 +/- 1.4 years old) and 18 gymnasts (10.4 +/- 1.3 years old), who had performed 3 years of high-level sport training (8-12 h per week for swimmers, 10-15 h per week for gymnasts). Thirteen girls (10.7 +/- 1 years old) doing less than 3 h per week of physical activity served as a control group. BMD measurements were done using dual-energy X-ray absorptiometry. There was no statistical significant difference between groups as regards age, body height and weight, and body composition. There was no statistical significant difference between swimmers and controls for all the BMD measurements. Mean BMD in gymnasts was statistically higher than in the control group for mid-radius (+15.5%, p < 0.001), distal radius (+33%, p < 0.001), L2-4 vertebrae (+11%, p < 0.05), femoral neck (+15%, p < 0.001) and Ward's triangle (+15%, p < 0.01). Moreover, in gymnasts, BMD at radius, trochanter and femoral neck was above normative values. We conclude that physical activity in childhood could be an important factor in bone mineral acquisition in prepubertal girls, but only if the sport can induce bone strains during a long-term program: gymnastics has such characteristics, unlike swimming. Such acquisition could provide protection against risks of osteoporosis in later life, but this remains debatable.

Bone Density↗
PubMed1998

Fractal analysis of trabecular bone texture on radiographs: discriminant value in postmenopausal osteoporosis.

Trabecular bone microarchitecture cannot be routinely evaluated. We have developed and validated a fractal analysis of trabecular bone texture on calcaneus radiographs. The aim of this work was to evaluate the ability of the fractal analysis to discriminate a group of 39 postmenopausal women with osteoporotic (OP) vertebral crush fractures (68.0 +/- 10.8 years) from an age-matched control group of 39 women (68.0 +/- 10.7 years). The value of the fractal analysis was compared with the value of the femoral neck bone mineral density (FNBMD) and trochanteric bone mineral density (TRBMD). The result is expressed by the parameter Hmean (Hmean = 2 - fractal dimension). Hmean value was 0.691 +/- 0.050 in the OP group versus 0.739 +/- 0.024 in the controls, while FNBMD was 0.598 +/- 0.113 g/cm2 versus 0.645 +/- 0.109 g/cm2 and TRBMD was 0.512 +/- 0.108 g/cm2 versus 0.594 +/- 0.106 g/cm2 respectively. The statistical significance of the Hmean test (p < 0.0001) was higher than for FNBMD (p < 0.05) and for TRBMD (p = 0.0004). We used a receiver operating characteristic (ROC) curve to check this superiority. The area under the ROC curve was 0.824 for Hmean, 0.633 for FNBMD and 0.727 for TRBMD. This superiority of the Hmean ROC curve was statistically significant versus FNBMD, but not versus TRBMD. In a second analysis, we studied the subgroups of OP patients and controls with overlapping FNBMD or TRBMD values to check whether the fractal dimension test could be discriminant in these subgroups. Significant statistical differences were found for Hmean between OP patients and controls in the overlapping subgroup for FNBMD or TRBMD (respectively p = 0.006 and p < 0.02). These data confirm that the fractal analysis of texture on calcaneus radiographs is able to discriminate OP patients with vertebral crush fracture from controls. This discrimination was stronger than that obtained by FNBMD or TRBMD alone. It was also present when we compared subgroups with overlapping values of FNBMD or TRBMD.

Absorptiometry, Photon↗
PubMed1998

Fractal analysis of bone texture on os calcis radiographs compared with trabecular microarchitecture analyzed by histomorphometry.

Microarchitecture of trabecular bone is an important determinant of bone fragility; to date, its evaluation requires bone biopsy with histomorphometry analysis. Methods of noninvasive characterization of trabecular bone microarchitecture are in development and we have developed and validated a bone texture analysis applied to bone radiographs and based on fractal geometry. The aim of our study was to compare this fractal analysis of trabecular bone texture on radiographs to the trabecular microarchitecture analyzed by bone histomorphometry on os calcis biopsies. Thirty eight ossa calcis from 19 human cadavers were studied. Fractal analysis of the trabecular bone of os calcis radiographs was performed by the maximum likelihood estimator following the fractional brownian motion model. The ossa calcis were dissected, then transcortical biopsy cores focused on the fractal analysis region of interest were obtained. Structural and connectivity parameters were measured with both automatic and semiautomatic analyzers. We have found a significant relationship between the fractal Hmean parameter and structural histomorphometric indices; the best correlation was found with trabecular separation (r = -0.55; P = 0.0004). Based on a stepwise regression analysis, trabecular spacing and trabeculae number together would explain 38% of the variance of the fractal parameter. Although the relationship with connectivity indices was poor, our fractal analysis of os calcis trabecular bone texture on radiographs seemed to partially reflect the trabecular bone microarchitecture.

Aged↗
PubMed1998

Biomechanical properties of human os calcanei: relationships with bone density and fractal evaluation of bone microarchitecture.

The relationship between bone strength and bone mass is well established. The link between trabecular microarchitecture and biomechanical properties has been less extensively explored. To address this question, we have tested the mechanical behaviour of calcaneus bone samples and investigated the correlations between mechanical properties on the one hand, bone density and fractal analysis of microarchitecture on the other hand. Mechanical properties of 43 human os calcanei were determined by uniaxial compression testing of samples from tuber calcanei. Ash density, bulk density and dual energy X-ray absorptiometry of the samples were measured. Fractal analysis of the trabecular bone on calcaneus radiographs was performed by two estimators derived from the fractional Brownian motion model. The mechanical properties of human os calcis were found to correlate with age and density measurements. Fractal parameters derived from the bone texture analysis showed weaker but significant correlations with bone strength. Fractal analysis of texture could account in part for the variations of bone strength, but in this study cannot explain better than density the mechanical properties of trabecular bone. Nevertheless, it provides a non-invasive means of assessing molecular bone microarchitecture.

Aged↗
PubMed1998

Lean tissue mass is a better predictor of bone mineral content and density than body weight in prepubertal girls.

PURPOSE AND METHODS: Body weight is the most extensively studied correlate of bone mass and is widely used as a covariate in statistical evaluations of bone mineral parameters. Lean tissue mass (LTM) also correlates with bone mass. We evaluated the correlations linking each of these two parameters with bone mineral content and bone mineral density in 41 prepubertal girls, including ten swimmers, 18 gymnasts and 13 nonathletes. Lean tissue mass, bone mineral content and bone mineral density were measured using dual-energy X-ray absorptiometry (Hologic QDR-1000/W; Hologic Inc., Waltham, MA, USA). Forward stepwise multiple regression was used to evaluate correlations linking bone mineral content or density (the dependent variables) to body weight or lean tissue mass (the independent variables). RESULTS: Body weight and lean tissue mass showed strong correlations with all bone mineral content and density measurements in the simple linear regression analysis, with lean tissue mass yielding the highest Pearson's correlation coefficients. In the multiple regression model, lean tissue mass consistently explained the largest proportion of the variance, whereas body weight had little influence or was eliminated from the model. The slopes of the regression lines of bone mineral content or density on body weight were significantly steeper in the subgroup of gymnasts (P < 0.001), whereas the slopes of the regression lines of bone mineral content or density on lean tissue mass were significantly less steep in the swimmers (P < 0.05). CONCLUSION: Our data indicate that lean tissue mass is a significant predictor of bone mass in prepubertal girls and explains a larger part of the variance of bone mineral content and density than body weight. Use of body weight as a covariate in studies of bone mineral density may lead to erroneous results in prepubertal girls.

Absorptiometry, Photon↗
PubMed1996

[Bone structure and mechanical resistance of the bone tissue].

The strength of bone depends on bone structure, both in terms of global geometry of the bone and the microscopic pattern of the trabecular network. Modifications in the trabecular organization, often related to the aging process, include altered anisotropy, perforations, loss of connectivity and microfractures. The microscopic architecture of trabecular bone can be studied on histomorphometric slices, the use of stereologic techniques on these slices may better reflect the changes occurring in 3 dimensions. High-resolution tomodensitometry and 3-D magnetic resonance imaging are under further evaluation. An evaluation of the fractal geometry of the trabecular network, performed on the vertebrae, calcaneus, or ulna on standard radiographs has given promising results. Bone strength is determined by resistance tests on bone tissue samples. The relationship between the applied force and bone deformation is used to determine a stress-strain curve and resistance parameters. The mechanical behavior of a given bone can be modelized by a Finite Element Analysis, the computerized model being able to predict the reaction of this bone. Ultra-sound analysis does not directly measure bone density, nor bone architecture, but would reflect both these properties. Velocity and attenuation of ultra-sounds, measured at the calcaneus or patella, are useful in distinguishing between controls and osteoporosis cases, and may have predictive value.

Adult↗
PubMed1996

Anisotropy measurements obtained by fractal analysis of trabecular bone at the calcaneus and radius.

The resistance of bone tissue is influenced not only by bone density parameters but also by bone architecture parameters, such as the microarchitecture and anisotropy of trabecular bone. We have developed and validated a fractal analysis method for studying bone microarchitecture on roentgenograms. This technique provides reproducible measurements of the fractal dimension (D) of bone, which reflects bone texture. The fractal dimension is determined in 36 different directions; the mean of these 36 values is representative of the image. A polar diagram gives the value of D according to the angle of analysis. By decomposing this diagram using polar Fourier Transform analysis, the parameters related to the shape of the polar diagram can be determined. This diagram image analysis technique has been used for other similar diagrams and applied to the results of our fractal analysis method. Diagram shape characterization may provide information on the angular distribution of results and therefore on the anisotropy of the images under study. The purpose of this study was to compare roentgenograms of the calcaneus and radius in the same subjects to determine whether texture and anisotropy parameters discriminated between these two bones. Roentgenograms of the calcaneus and radius were obtained in ten nonosteoporotic subjects. The radius had a smaller fractal dimension than the calcaneus (mean +/- standard deviation: 1.215 +/- 0.025 and 1.285 +/- 0.066, respectively; p = 0.014). Differences in the shape of the polar diagram were found between the two bones. The mean Fourier coefficient ratio C2/C4 was considerably smaller at the calcaneus (0.63 +/- 0.50) than at the radius (4.88 +/- 3.45; p = 0.005). Our method allows quantitative characterization of texture and anisotropy differences between the calcaneus and radius. The smaller fractal dimension of the radius probably reflects the simpler architecture of this non weight-bearing bone. The differences in polar diagram shape allow to evaluate anisotropy differences between the calcaneus and radius.

Adult↗
PubMed1994

Fractal organization of trabecular bone images on calcaneus radiographs.

Bone density is not the unique factor conditioning bone strength. Trabecular bone microarchitecture also plays an important role. We have developed a fractal evaluation of trabecular bone microarchitecture on calcaneus radiographs. Fractal models may provide a single numeric evaluation (the fractal dimension) of such complex structures. Our evaluation results from an analysis of images with a varying range of gray levels, without binarization of the image. It is based on the fractional brownian motion model, or more precisely on the analysis of its increment, the fractional gaussian noise (FGN). The use of this model may be considered validated if two conditions are fulfilled: the gaussian repartition and the self-similarity of our data. The gaussian repartition of intermediate lines of these images was tested on a sample of 32,800 lines from 82 images. Following a chi-square goodness-of-fit test, it was checked in 86% of these lines for alpha = 0.01. The self-similarity was tested on 20 images by two estimators, the variance method of Pentland and the spectrum method of Fourier. Self-similarity is defined by lined-up points in a log-log plot of the FGN spectrum or of the variance as a function of the lag. We found two self-similarity areas between scales of analysis ranging from 105 to 420 microns, then above 900 microns, where linear regression produced high mean correlation coefficients (r > or = 0.97). Following this validation, we studied the reproducibility of this new technique. Intra- and interobserver reproducibility, influence of transferring the region of interest, and long-term reproducibility were assessed and given CV of 0.61 +/- 0.15, 0.68 +/- 0.47, 0.53 +/- 0.16, and 2.07 +/- 0.84%, respectively. These data have allowed us to validate the use of this fractal model by checking the fractal organization of our radiographic images analyzed by the model. The good reproducibility of successive x-rays in the same subject allows us to undertake population studies and to envisage longitudinal series.

Calcaneus↗