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A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform.

Brunet-Imbault B, Lemineur G, Chappard C, Harba R, Benhamou CL - BMC Med Imaging (2005)

Bottom Line: The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively.From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA.The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Equipe Inserm 658, Hôpital Porte Madeleine, BP 2439, 45032 Orléans Cedex 1, France. brunet-imbault@libertysurf.fr

ABSTRACT

Background: The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA.

Methods: In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented.

Results: Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 +/- 0.15 versus 1.72 +/- 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA.

Conclusion: The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions.

No MeSH data available.


Related in: MedlinePlus

Radiographic image of the calcaneus showing the localization of the Region of Interest (ROI). Inside the ROI, longitudinal trabeculae correspond to the compressive trabecular network extended from the subtalar joint and the transverse to the tensile trabecular network sweeping backwards and upwards the great tuberosity. Arrows show anatomical landmarks corresponding to the bottom of the ROI.
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Figure 1: Radiographic image of the calcaneus showing the localization of the Region of Interest (ROI). Inside the ROI, longitudinal trabeculae correspond to the compressive trabecular network extended from the subtalar joint and the transverse to the tensile trabecular network sweeping backwards and upwards the great tuberosity. Arrows show anatomical landmarks corresponding to the bottom of the ROI.

Mentions: In order to obtain digitized images of the calcaneus trabecular bone, the radiographic films were digitized with an AGFA Duoscan scanner (AGFA GEVAERT N.V., Morstel, Belgium) with 256 gray-levels. Calcaneus is known to be a heterogeneous site of trabecular bone [32]. For this reason we have selected a large region of interest (ROI) of 2.7 × 2.7 cm2 (256 × 256 pixels with a pixel size of 105 μm). The ROI of 256 × 256 pixels (Figure 1) was defined from anatomic marks [27]. The basis of the ROI was positioned on a line linking the plantar aponeurosis insertion to the superior end of the Achilles tendon insertion, the ROI comprising both compressive and tensile trabecular network [10].


A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform.

Brunet-Imbault B, Lemineur G, Chappard C, Harba R, Benhamou CL - BMC Med Imaging (2005)

Radiographic image of the calcaneus showing the localization of the Region of Interest (ROI). Inside the ROI, longitudinal trabeculae correspond to the compressive trabecular network extended from the subtalar joint and the transverse to the tensile trabecular network sweeping backwards and upwards the great tuberosity. Arrows show anatomical landmarks corresponding to the bottom of the ROI.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1173107&req=5

Figure 1: Radiographic image of the calcaneus showing the localization of the Region of Interest (ROI). Inside the ROI, longitudinal trabeculae correspond to the compressive trabecular network extended from the subtalar joint and the transverse to the tensile trabecular network sweeping backwards and upwards the great tuberosity. Arrows show anatomical landmarks corresponding to the bottom of the ROI.
Mentions: In order to obtain digitized images of the calcaneus trabecular bone, the radiographic films were digitized with an AGFA Duoscan scanner (AGFA GEVAERT N.V., Morstel, Belgium) with 256 gray-levels. Calcaneus is known to be a heterogeneous site of trabecular bone [32]. For this reason we have selected a large region of interest (ROI) of 2.7 × 2.7 cm2 (256 × 256 pixels with a pixel size of 105 μm). The ROI of 256 × 256 pixels (Figure 1) was defined from anatomic marks [27]. The basis of the ROI was positioned on a line linking the plantar aponeurosis insertion to the superior end of the Achilles tendon insertion, the ROI comprising both compressive and tensile trabecular network [10].

Bottom Line: The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively.From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA.The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Equipe Inserm 658, Hôpital Porte Madeleine, BP 2439, 45032 Orléans Cedex 1, France. brunet-imbault@libertysurf.fr

ABSTRACT

Background: The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA.

Methods: In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented.

Results: Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 +/- 0.15 versus 1.72 +/- 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA.

Conclusion: The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions.

No MeSH data available.


Related in: MedlinePlus