1. Failure Determination in Embedded Biomaterials
Rexxi Prasasya, Chou Mai, Hyungjin Kim
Advisor: Prof. Willis Tompkins
Client: Raj Ambay, MD, DDS, UWHC, Division of Plastic Surgery

2. Outline Background Problem Statement Competition Alternative Proposals
Design Matrix
Future Work
References

3. Background Biomaterial Materials Applications
Metal, polymer, biologically derived, ceramics
Combination of materials
Biocompatible
Applications
Repair
Replacement
Drug delivery system

4. Problem Statement Biomaterial failure determination Properties changes
Physical, chemical, structural
Quantification
Non-invasive detection
Hyungjin, in this slide you don’t need to mention anything about Host response. Just say that our goal is to determine failure within biomaterial by detecting changes in property (can be physical, chemical, or structural). We would like to quantify this change non-invasively.
(Kao, 2008)

5. Competition MRI X-ray Structural changes Non-metal Expensive
Detect density difference
Low cost
On MRI part don’t mention inflammation, say that it can detect structural changes, but only limited to non-metal biomaterial.

6. Design Requirements Determine change in property
Detect failure in biomaterials
Non-invasive
Clinical utility
Cost: less than $500
Note: Clinical utility means it can be easily integrated into hospital setting.

7. Alternative designs Impedance spectroscopy Elastography
Microwave tomography

8. Design 1: Impedance Spectroscopy
Contrasts materials’ abilities to resist the flow of electrical current
Use high frequency AC source
Example: impedance pneumography

9. Design 1: Pro’s and Con’s
Hand-held device feasible
Simple electronic circuit
High impedance of biomaterials

10. Design 2: Elastography Exploit difference in stiffness
Echoes from high frequency sound wave
Combined ultrasound and compressive image
(Itoh et al., 2006)

11. Design 2: Pro’s and Con’s
High sensitivity
Readily available
Reduced cost ($100 - $200) per scanning
Immediate diagnosis
Con’s
Complex system ($250,000)
Requires multiple transducers
Dependence on interpreter

12. Design 3: Microwave Tomography
Detects differences in dielectric properties
Captures reflected electromagnetic waves
Example: ischemia detection
Physiological condition: molecular constituent, ion concentration and mobility, concentration fo free water and bound water molecule, tissue temperature
(Guerquin-Kern et al. 1985)

13. Design 3: Pro’s and Con’s
Known dielectric properties
Non-ionizing electromagnetic field
High contrast ratio
Limited access to microwave technology
Variations in tissue dielectric properties
At body temperature, dielectric constant of fat is about 5 and heart tissue is about 50 – so about 10 fold difference. Contrast range in X-ray region is less than 2% and less than 10% in ultrasound.
Level of microwave field used in this procedure is comparable w/ that used in cell phones

14. Design Matrix Category Weight Impedance Spectroscopy Elastography
Microwave Tomography
Feasibility
.30 1 9 8
Accuracy
.20 7
Cost 5
Availability
.10 2
Non-invasiveness
.15 6
Accessibility
.05
Total
4.4
7.8
6.9

15. Future Work Construction of phantom Qualitative testing
Evaluation of transducers and frequencies
Clinical applicability

16. Reference
“A-Medic 500 Radiographic X-ray Unit.” Accessed March 06,
Guerquin-Kern. J.L, et al. “Active microwavetomographic imaging of isolated, perfused animal organs.” Bioelectromagnetic 1985, p
“How elastography works.” Accessed March 03, 2008.
Itoh, K. et al. “Breast Disease: Clinical Application of US Elastography for Diagnosis.” Radiology 2006; p. 239:341.
Kao, J. “BME 430 lecture notes”
Accessed March 03, 2008.