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Transcript of Second most prevalent cancer worldwide 3 Fifth most common cause of cancer related death 4 Early...
Hyperelastic Elastography for Breast Cancer Assessment
By Ryan Armstrong
Under Guidance of Hosein Amooshahi
In Dr. Samani’s Lab
OutlineBreast Cancer
OverviewBreast AnatomyCurrent Diagnostic Techniques
ElastographyConcept of ElastographyLinear ElastographyNon-Linear (Hyperelastic) ElastographyBiological Stress-Strain CurveElastography as Inverse Problem
Current Lab WorkNumerical PhantomNumerical Phantom AlgorithmTissue Mimicking Phantom
Summary
Breast Cancer Overview
Second most prevalent cancer worldwide 3
Fifth most common cause of cancer related death 4
Early diagnosis is a huge factor in survival
Anatomy of Breast
Figure 1: Taken from Mehrabian, 2008. 1
Current Diagnostic Techniques
Self Examination (Manual Palpation)
Mammography
Magnetic Resonance Imaging
Ultrasound
Biopsy
Elastography Overview Images taken pre and post-compression
Stress-strain relationships in tissues are analyzed
Reconstruction technique used to determine elastic parameters of tissues
Tumours in breast tend to be abnormally stiff compared to surrounding tissue
Linear Elastography For each tissue type, only a single elastic
parameter
Young’s Modulus: E = σ/ε
Only valid for low strains
Significant errors associated with technique
Hyperelastic Elastography
Generally more than one hyperelastic parameter per tissue
Defined by strain energy functions
Valid for large strain values
Calculations more complicated
Biological Stress-Strain Curve
Figure 2: Taken from http://www.smpp.northwestern.edu/. . . 2
Elastography as Inverse Problem
Reconstructing hyperelastic parameters from data is an inverse problem
Involves initial estimates and numerous iterations
Numerical Phantom Computerized proof of concept
Boundary conditions and geometry defined consistent with real breast anatomy
Finite Element calculations performed in ABAQUS to generate displacement data
Iterative inversion algorithm runs to convergence leading to hyperelastic parameter reconstruction
Numerical Phantom (3D)
Before deformation After deformation
Hyperelastic Parameters Reconstruction Algorithm
Calculate displacement field using OF
Calculate Deformation Gradient
Calculate Stress tensor using ABAQUS
Averaging & updating HE parameters (1 to 3)
Converge EndYes
No
Main pre-
image
Main post-image
Initial HEPs
Latest artificial deformed image
Updated HEPs
Figure 3: Taken from Amooshahi 5
Tissue Mimicking Phantom Construction of phantom with PVA,
Biocide, and heat-cool cycles
Unaxial test for parameter measurement
Pre and Post Compression US images are taken
Hyperelastic parameters reconstructed
Summary Breast cancer has high prevalence and
mortality rate
Early detection is vital for treatment and ultimately survival
Elastography shows great potential as a diagnostic tool with high specificity
Hyperelastic models allow us to reconstruct parameters for high strain
References1. H Mehrabian. Soft Tissue Hyperelastic Parameter Reconstruction. Masters thesis submitted to the
University of Western Ontario. Supervisor: Abbas Samani. (2008)2. Mechanical Properties of Soft Tissue. In Sitting Biomechanics Laboratory. Retrieved May 30th, 2010
from:http://www.smpp.northwestern.edu/Makhsous/Mechanical%20Properties%20of%20Soft%2 0Tissue.shtml
3. World Health Organization International Agency for Research on Cancer (2008). "World Cancer Report". Retrieved on May 30th, 2010.4. World Health Organization (February 2006). "Fact sheet No. 297: Cancer". Retrieved on May 30th, 2010.5. M Amooshahi. (Nov. 17, 2009) Classification of Breast Tumours Using Hyperelastic Elastography
PowerPoint presentation presented at the University of Western Ontario.
Questions?