In vivo Bone Characterization from Magnetic Resonance Imaging: Morphometry and Mechanical analysis

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1 In vivo Bone Characterization from Magnetic Resonance Imaging: Morphometry and Mechanical analysis Angel Alberich-Bayarri, PhD 15 th october 2014

2 La Fe Polytechnics and University Hospital Valencia East of Spain 1000 beds Medical Imaging 7 CT scanners 5 MR scanners 1 PET/CT 1 SPECT/CT Research Group & Lab 1 MR scanner 1 angio suite

$Asymptomatic progression. First symptom that usually appears: bone fracture. - Reginster JY, Burlet N. Bone 2006;38:S4-S9. - Cummings SR, Melton III JR.$

3 Introduction to the problem Approx. 200 million patients worldwide. Prevalence (> 50 y.o.): Women: 33% Men: 8% Usually diagnosed in advanced stages. Asymptomatic progression. First symptom that usually appears: bone fracture. - Reginster JY, Burlet N. Bone 2006;38:S4-S9. - Cummings SR, Melton III JR. Lancet 2002;359:

$Introduction to the problem Estimation of 2.6 millions of new fractures by 2025.$

4 Introduction to the problem Estimation of 2.6 millions of new fractures by NIH definition 2001: Skeletal disease characterized by a decreased bone resistance that induces a higher probability of suffering a fracture in a specific person. Fracturas de muñeca Fracturas vertebrales Fracturas de cadera -Gullberg B, Johnell O, Kanis JA. Osteoporosis International 1997;7:

5 Introduction to the problem Bone resistance decrease Bone Mineral Density Trabecular Microarchitecture

$50 SD BMD explains around 60% of bone fractures - WHO technical report series 843, Geneva,$

6 Introduction to the problem Diagnosis: Dual Energy X-Ray Absorptiometry (DEXA) WHO Criteria Stage Healthy Osteopenia Osteoporosis DEXA T-score > SD SD to SD < SD BMD explains around 60% of bone fractures - WHO technical report series 843, Geneva, Switzerland; Wehrli FW, et al. Topics in Magnetic Resonance Imaging 2002;13:

Introduction to the problem There is a need to characterize bone microarchitecture Complement in the diagnosis process Therapy efficacy follow-up

7 Introduction to the problem There is a need to characterize bone microarchitecture Complement in the diagnosis process Therapy efficacy follow-up Quantitative properties of shape, orientation, topology, tortuosity, mechanical resistance. We must develop and find new tools to characterize bone quality.

8 How to obtain bone images Radius distal metaphysis (non-dominant) 3 Tesla MR (Philips Healthcare) Gradients: 80mT/m (Gmáx), 200mT/m/ms (SR) 4-channel surface coil

9 How to obtain bone images Acquisition mode: 3D Sequence type: Gradient-Echo T1 (Spoiled) TE/TR/α: 5ms/16ms/25º 60 axial partitions Voxel size: 180 x 180 x 180 µm 3 Parallel Im. Factor: 2/0 (plane/slices) Bandwidth: 167 Hz/pix Matrix: 512 x 512 Number of examinations: 3 Total time: 5 42

10 Processing the images Automated Range filters Average filters Thresholding Adaptative contours Semi-automated Rectangular ROI Propagation through slices

11 Processing the images Heterogeneities correction. Bone Volume Fraction Map (BVF) Laplacian based local thresholding of intensities ~ L r I Original segmented image BVF map - Vasilic B, Wehrli FW. IEEE Transactions on Medical Imaging 2005;24:

12 Processing the images Increase in spatial resolution 180 x 180 x 180 µm 90 x 90 x 90 µm BVF map Superresolution José V. Manjón, Pierrick Coupe, Antonio Buades, Louis Collins and Montserrat Robles. MRI Superresolution Using Self Similarity and Image Priors. International Journal of Biomedical Imaging, Article ID , 2010

13 Processing the images Otsu s thresholding Intra-class variance minimization t* arg.max t 2 B 2 T Superresolution Binarization

14 Processing the images Pipeline Original segmented BVF map Binarization Superresolution

15 Processing the images 3D Triangulated surface extraction STL exportation routine

16 Morphometry analysis Morphology Bone volume / total volume percentage BV/TV [%] BV / TV n _ bone _ voxels n _ total _ voxels Mean Trabecular Thickness [µm] TbTh. p Sk c 2 d Mean Trabecular Separation [µm] Mean number of adjacent marrow voxels Sk c min Trabecular index Tb. N BV / TV TbTh.

17 Morphometry analysis Morphology - Alberich-Bayarri et al. AJR 2008: 191:

18 Morphometry analysis Irregularities analysis 2D Fractal Dimension, D2D Contour detection Box-counting Slice-by-slice Validation 2D log( N) D log( ) k

19 Morphometry analysis Irregularities analysis 3D Fractal Dimension, D3D Surface detection Validation 3D log( N) D log( ) k - Alberich-Bayarri et al. Medical Physics 2010;37:

20 Morphometry analysis Irregularities analysis 2D and 3D Fractal Dimension results - Alberich-Bayarri et al. Medical Physics 2010;37:

21 Morphometry analysis Anisotropy analysis Mean Intercept Length Tensor Scale b a θa DA=a/b - Inglis D, Pietruszczak S. International Journal of Solids and Structures 2003;40: Saha PK, Wehrli FW. Pattern Recognition 2004;37:

22 Mechanical analysis Meshing algorithm Voxelwise Hexahedron elements (brick) Nodes and elements definition Approx: 1 million of elements

23 Mechanical analysis Model generation Properties definition Elastic modulus: E b =10 GPa (Linear, elastic, isotropic) 0.3 =ט coefficient: Poisson Exportation routines generation Ansys (Ansys Inc., USA) Abaqus (Dassault Systèmes SIMULIA Inc., USA) Salome (CAELINUX) OpenFOAM - Ladd AJ, Kinney JH. Journal of Biomechanics 1998;31: Fung YC. Biomechanics. Mechanical properties of living tissues (2 nd edition). New York, NY: Springer, Newitt DC, Majumdar S, van Rietbergen B, et al. Osteoporosis International 2002;13:6-17.

24 Mechanical analysis Compression essay X, Y, Z Deformación conocida Definición de sistema de ecuaciones K u f K: stiffness matrix u: displacements vector f: forces vector

Mechanical analysis Compression essay Solution calculation Sparse Gaussian Elimination e T K B DB d( vol) V e D E 1 v 2 1 v 0 v 1 0 0 0 (1 v) / 2 e K ij K ij K u f

25 Mechanical analysis Compression essay Solution calculation Sparse Gaussian Elimination e T K B DB d( vol) V e D E 1 v 2 1 v 0 v (1 v) / 2 e K ij K ij K u f Non-linearities: infinite displacements Generation of a routine previous to the generation of an ANSYS exportation file. FE model generation Isolated elements control Exportable file

26 Mechanical analysis Compression essay Young s modulus calculation. Homogenization theory X, Y, Z E app 1 A n F - Hollister SJ, Fyhrie DP, Jepsen KJ, Goldstein SA. Journal of Biomechanics 1991;24: Hollister SJ, Kikuchi N. Computational Mechanics 1992;10:73 95.

27 Mechanical analysis 3D nodal stresses [Pa] Pa Pa

28 Mechanical analysis 3D nodal stresses [Pa] Control Osteoporosis Pa

29 Trabecular bone analysis Influence of the ROI - Alberich-Bayarri et al. AJR 2008: 191:

Trabecular bone analysis Reproducibility and accuracy The goal was to evaluate the accuracy and reproducibility of the morphometry and mechanical trabecular bone

30 Trabecular bone analysis Reproducibility and accuracy The goal was to evaluate the accuracy and reproducibility of the morphometry and mechanical trabecular bone characterization from MR. 5 sheep extremities (tibia proximal metaphysis) Reproducibility: 3 MR acquisitions of each sample (1 per day) Accuracy: 1 µct acquisition per sample (Gold Standard)

31 Trabecular bone analysis Reproducibility and accuracy 3 Tesla MR (Philips Healthcare) 4-channel surface coil Sequence: 3D GE T1 (Spoiled) TE/TR/α: 5ms/16ms/25º 60 partitions Voxel size: 180 x 180 x 180 µm 3

32 Trabecular bone analysis Reproducibility and accuracy Accuracy: µct acquisition explore Locus SP, General Electric, USA. Spatial resolution (7,5 x 7,5 x 7,5 µm). Gold standard

33 Trabecular bone analysis Reproducibility and accuracy All parameters showed a high reproducibility, with variation coefficients below 10%. BVTV TbTh TbSp TbN D 2D D 3D Ex Ey Ez p RMS CoV [%] - Alberich-Bayarri A et al.. Titlel Radiologia,

34 Trabecular bone analysis Reproducibility and accuracy Only Tb.Th, Tb.Sp y Tb.N showed significant differences when compared to μct (p<0.05). BV/TV [%] Tb.Th [mm] Tb.Sp [mm] Tb.N [mm -1 ] D2D D3D Ex [MPa] Ey [Mpa] Ez [Mpa] MR µct p value Error [%]

35 Trabecular bone analysis Reproducibility and accuracy

36 Trabecular bone analysis But Too many parameters? Clinical confusion due to an excess in the number of variables Solution: Mechanical Competence of Bone (MCP) unified parameter! - Alberich-Bayarri et al. IEEE Trans Biomed Engineering 2013: 60(5):

37 Final Workflow

38 Report

39 Bone analysis Work in progress: Ultra-Short Echo Time Water molecules in small pores have a really short TE (below ms)

40 Acknowledgements: The developments and results shown on bone characterization are partialy funded by the Ministry of Economy and Competitiveness of Spain through Project DPI Design for Osteoporosis (DFO). Principal Investigator: María Ángeles Pérez (University of Zaragoza)

41 Acknowledgements: Enrique Ruiz Jose Tomás Celia Juan Beatriz Dionisio Raquel Nombela Ana Penadés Ángel Alberich-Bayarri Luis Martí-Bonmatí

42 OBRIGADO! Angel Alberich-Bayarri, PhD 15 th october 2014

Conference Biomedical Engineering

Conference Biomedical Engineering Automatic Medical Image Analysis for Measuring Bone Thickness and Density M. Kovalovs *, A. Glazs Image Processing and Computer Graphics Department, Riga Technical University, Latvia * E-mail: mihails.kovalovs@rtu.lv