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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

Synthetic images a: Synthetic image of astructure with orientations between 0 and 80° in 3 dimensional space b: Fast Fourier Transform (FFT) spectrum of the image 4a c: Synthetic image of a structure with orientations between 0 and 17° in 3 dimensional space d: FFT spectrum of the image 4c
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Figure 4: Synthetic images a: Synthetic image of astructure with orientations between 0 and 80° in 3 dimensional space b: Fast Fourier Transform (FFT) spectrum of the image 4a c: Synthetic image of a structure with orientations between 0 and 17° in 3 dimensional space d: FFT spectrum of the image 4c

Mentions: To test the reliability of DA assessment, we tested this method on projected volume with known disorientations. We synthesized 6 series of 8 images composed of beam like structures more or less aligned following two directions in order to obtain structures close to trabecular bone of calcaneus. For the less anisotropic structure, horizontal and vertical disorientations varied from 0 to 80° (Figure 4a), and for the most anisotropic structure, the disorientation of the beam like structures varied from 0 to 17° (Figure 4c). These synthetic images comprised a wide variety of structures, from anisotropic to almost isotropic, a variety much wider than expected in the clinical X-rays. The projections of these volumes were analyzed with the same software as bone radiographs.


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)

Synthetic images a: Synthetic image of astructure with orientations between 0 and 80° in 3 dimensional space b: Fast Fourier Transform (FFT) spectrum of the image 4a c: Synthetic image of a structure with orientations between 0 and 17° in 3 dimensional space d: FFT spectrum of the image 4c
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1173107&req=5

Figure 4: Synthetic images a: Synthetic image of astructure with orientations between 0 and 80° in 3 dimensional space b: Fast Fourier Transform (FFT) spectrum of the image 4a c: Synthetic image of a structure with orientations between 0 and 17° in 3 dimensional space d: FFT spectrum of the image 4c
Mentions: To test the reliability of DA assessment, we tested this method on projected volume with known disorientations. We synthesized 6 series of 8 images composed of beam like structures more or less aligned following two directions in order to obtain structures close to trabecular bone of calcaneus. For the less anisotropic structure, horizontal and vertical disorientations varied from 0 to 80° (Figure 4a), and for the most anisotropic structure, the disorientation of the beam like structures varied from 0 to 17° (Figure 4c). These synthetic images comprised a wide variety of structures, from anisotropic to almost isotropic, a variety much wider than expected in the clinical X-rays. The projections of these volumes were analyzed with the same software as bone radiographs.

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