Biomedical Modelling with Clinical Applications

1
Biomedical Modelling with Clinical Applications
Su Yi ??
2
(No Transcript)
3
(No Transcript)
4
From an engineering perspective
Design- centric
5
From a clinical perspective
Patient- centric
6
(No Transcript)
7
An example in dealing with heart failure

• Epidemic of chronic heart failure among survivors
  of heart attack

8
What happens after an heart attack?

• LV remodelling the process in which the heart
  alters its size, shape configuration after a
  heart attack
• Serial assessment quantitation of LV
  remodelling facilitates
• surveillance of heart failure progression
• tailoring of appropriate treatment monitoring
  of efficacy
• reduce cost

9
How is LV remodelling being assessed?

• Ejection Fraction (EF), i.e. change in LV volume
• Qualitative or semi-quantitative descriptors of
  shape, e.g. sphericity index (SI) and conicity
  index (CI)
• Dimension, e.g. change in LV diameter, wall
  thickness image-based
• Twisting, e.g. tagged-MRI, speckle tracking
  echocardiography image-based
• Ventricular wall stiffness (s/e) FEM-based

10
How is LV remodelling being assessed?

• Cardiac magnetic resonance (CMR) imaging
• LV structure and function, e.g. LV dimensions, LV
  volumes, etc
• Infarct size and extent late gadolinium
  enhancement (LGE)
• Fails to exploit full range of quantitative
  multi-dimensional MRI data

11
Our idea

• To develop new indices to quantitate LV
  remodelling using a computational geometry
  approach
• Extract 3D/4D information
• Provide localised patient-specific details
• Apply rigorous engineering and physiological
  principles to derive cardiac indices which are
  robust and scientifically valid

12
Our approach

• What kind of clinical inference can we make from
  the model?

13
Approximating local shape of LV
14
Extracting physical properties

• Local 3D radius (R)
• Local wall thickness (T) - equivalent to solving
  a ray-triangle intersection of a ray with the
  epicardial surface
• Local wall stress (?)

15
Is 3D method better than 2D image-based methods?

• 10 normal subjects

16
Why is a 3D method better than 2D image-based
methods?
17
Regional curvedness

• 10 control 10 diseased

18
Regional Wall Stress and Thickening
High wall stress, especially at apex
Very little wall thickening despite high wall
stress
19
Validation against LGE
late gadolinium enhancement representing
myocardial scaring/fibrosis
20
Surgical Ventricular Restoration

• 40 patients pre- and post-SVR

Before SVR
4 months after SVR
21
Comparison to other methods
22
What are the implications?

• Potential to replace delayed contrast
  hyperenhancement MRI
• Reduce scanning time/cost by at least 25
• Avoid the need to inject Gadolinium which might
  result in complication in some patients
• Reduce patient trauma

23
What are the current limitations?

• Current approach does not exploit full 4D
  information finite difference between
  end-diastole and end-systole phase
• Partitioning of endocardial surface according to
  medical nomenclature assumes rigid rotation and
  linear vertical compression not realistic
• Assumption of uniform pressure loading in LV
  chamber

24
Whats needed to bring this to the next level?

• Clinical trial testbedding
• 20 normal
• 30 diseased over time (at least 1 year)
• age-matched
• gender-matched

25
Acceptance by clinicians

• Medical Journals
• Zhong L, Su Y, Yeo SY, Tan RS, Ghista DN, Kassab
  G. Three-dimensional curvedness and wall stress
  assessment in dilated cardiomyopathy using
  magnetic resonance imaging. Am J Physiol Heart
  Circ Physiol, 296 H573-H584, 2009.
• Yeo SY, Zhong L, Su Y, Tan RS, Ghista DN. A
  curvature-based approach for left ventricular
  shape analysis from cardiac magnetic resonance
  imaging. Med Biol Eng Comput, 47(3) 313-322,
  2009.
• Invited Book Chapter
• Zhong L, Tan RS, Su Y, Yeo SY, Ghista DN, Kassab
  G. Noninvasive Assessment of Left Ventricular
  Remodeling Geometry, Wall Stress and Function,
  in Computational Cardiovascular Mechanics
  Modeling and Applications in Heart Failure,
  Julius Guccione and Mark Radcliff, Ed.
• Medical Conferences
• L. Zhong, Y. Su, S. Y. Yeo, D. Ghista, R. S. Tan.
  Three-dimensional left ventricular regional shape
  and wall stress alterations after surgical
  ventricular restoration, accepted for oral
  presentation at the 11th World Congress on
  Medical Physics and Biomedical Engineering,
  September 7-12, 2009 in Munich, Germany.
• Yeo SY, Zhong L, Su Y, Tan RS, Ghista DN.
  Analysis of left ventricular surface deformation
  during isovolumic contraction. Conf Proc IEEE Eng
  Biol Soc 20071787-790. (EI, PubMed)
• Zhong L, Yeo SY, Su Y, Le TT, Tan RS, Ghista DN.
  Regional assessment of left ventricular surface
  shape from magnetic resonance imaging. Conf Proc
  IEEE Eng Biol Soc 20071884-887. (EI, PubMed)
• Yeo SY, Tan RS, Chai GB, Ghista DN. Variation of
  left ventricular surface shape during the cardiac
  cycle. The 3rd IASTED International Conference on
  Biomechanics, BioMech 2005. Benidorm, 7-9 Sep
  2005.

26
Some concluding thoughts

• Near confluence point of computational and
  clinical practitioners
• Need appropriate structure to facilitate
  communications
• Novelty vs Impact
• Ease-of-use is key

27
Thank You