1. A Phantom for use in an MR Imager
BME 402
February 24, 2006

2. Team Members:
Missy Haehn (Communications)
Can Pi (BWIG)
Ben Sprague (Team Leader)
Andrea Zelisko (BSAC)
Advisor:
Professor Kristyn Masters
Client:
Dr. Victor Haughton, M.D.

4. Outline Background Design Components Phantom Disks The Ultimate Goal
Summary

5. Problem Statement
To create an MR phantom for use in assessing the relationship between T2 values and disk health.
Develop gelatin samples with T2 values between 50 and 150 ms
Assess the precision and accuracy of MR measurements using the phantom
Using cadaver disks, assess relative disk health using the T2 measurements
Ultimate goal: find preliminary data to support disk health based on T2 measurement

6. Intervertebral Disks
Spine consists of vertebrae and disks which act as shock cushions
Disks are made up of varying percentages of water, collagen, and glycoaminoglycans (GAG)
Variations correspond to differing degrees of health
Disks begin to degenerate with age due to reduced blood flow and water content

7. Imaging Modality: MRI MR imaging uses magnets and
radio freq. waves to image body
T2 value is relaxation time rate of decay for protons
Can essentially pick a point in the body and ask “What type of tissue are you?”
Phantoms facilitates scanner calibration as well as research in MR scanners

8. Project Motivation Dr. Haughton is Neuroradiologist at UW-Hospital
Research interest in dynamic spine MR imaging
One focus in disk degeneration
Design Project:
Phantom needed for calibration of laboratory equipment and research
Gels needed to predict health of disks

9. Necessary Components for the Design
Gelatin hydrogels to hold water and GAGs suspended in solution
Known amounts of water and GAGs
T2 values 50 to 150 ms
Gadolinium doped water solutions to assess precision/accuracy in scanner
Phantom container to hold Gd water and gelatin samples

10. Current Research
Research by Nightingale, et al. determined a positive correlation between water content and GAG content
Performed on NMR
Research by Masi, et al. found similar results with Gd concentration and T2 values
Commercial phantoms are typically filled with doped water from GE, Supertech, CIRS

11. Phantom: Last Semester’s Design

12. Phantom: Progress Started with a larger, more cumbersome design
Attempted to use materials to eliminate water
Standard Imaging ( tissue mimicking, blue water, virtual water)
Materials didn’t work: showed up on MR scan
Decided to use acrylic
Commonly used in commercial and research phantoms
New design
Disk samples held close
Has spigot for easy fill and empty
Less cumbersome

13. Phantom: Current Work Final adjustments Construction: Todd Kyle
Cross-like pattern for vials
9 total slots
Made from acrylic
Construction: Todd Kyle
Constructed by UW ME instrument shop

14. Phantom: Potential Problems
Construction is slow
Dependant on machine shop
Possible problems with construction due to difficulty
Friction fit holes may wear down
Artifacts possible at material interfaces

15. Phantom: Future Work Testing on the phantom
With and without samples
Utilizing phantom for data collection
More accurate placement
Easier identification
Utilizing phantom for tests that depend on spacing
Can vary distance and position from coil

16. Disk Mimicking Samples: Last Semester
Original Samples
Did not maintain homogeneity
Evaluated different hydrogels
gelatin, agarose, acrylamide, alginates
Tests/results

17. Disk Mimicking Samples: Progress
Addition of components
GAGs
Tests/results

18. Disk Mimicking Samples: Current Work
Varying components
Water
GAGs
Correlate water-T2
and GAG-T2
Test results

19. Analysis

20. Disk Mimicking Samples: Potential Problems
Gels
Not mimicking disks correctly
Components in gels not the same as in body
Can rule out collagen effect on T2 based on study performed by Nightingale, et al.
Multiple water/GAG conc. for various T2 values pose problems for analysis

21. Disk Mimicking Samples: Future Work
From the relationships we determine from our gels and T2 values, we can test cadaver intervertebral disks
Quantifying components of disks
Two methods:
Scan disk and then fully digest to find out composition
Scan disk and digest in successions to find out correlation between T2 and composition of disk

22. The Ultimate Goal To assess the health of a disk based on T2 values
No definite values, only a range
Healthy
Unhealthy
Inconclusive

23. Summary Why we are doing this? Our progress
To find a relationship between T2 and water content
This will lead to a determination of disk health after more human testing in completed
Our progress
Currently gathering initial relationship data
Cadaver disks for proof of concept
What we hope to finish by May
Preliminary research into relationship for T2 and disk health

24. References
Nightingale, T., et al. A Model of Unloaded Human Intervertebral Disk Based on NMR Relaxation. Magnetic Resonance in Medicine :
Elliott, Dawn M. A Linear Material Model for Fiber-Induced Anisotropy of the Anulus
Fibrosus. J. Biomechanical Engineering, Vol. 122 p April 2000.
Masi, J., et al. Optimization of Gadodiamide Concentration for MR Arthrography at a 3T. American Journal of Radiology :
Weidenbaum, M., et al. Correlating Magnetic Resonance Imaging with the Biochemical Content of the Normal Human Intervertebral disk. J. Ortho Research. 10(4):
Lumbar Degenerative Disk Disease. DynoMed. 2/12/05.
Blechinger, J.C., Madsen, E.L., and Frank, G.R. “Tissue-mimicking gelatin-agar gels for use in magnetic resonance imaging phantoms.” Medical Physics, Vol. 15, No. 4, Jul/Aug 1988.
Phantom Applications and Technology Overview Computerized Imaging Reference Systems, Inc.
Rice, J. Robin, et all. “Anthropomorphic 1H MRS head phantom.” Medical Physics, Vol. 25, No. 7, July 1998, Part 1.

25. Thanks too… Dr. Victor Haughton John Perry
Dan Schmidt, Standard Imaging
Professor Bill Murphy
Professor Wally Block
Advisor Kristyn Masters
Ernie Madsen and Maritza Hobson, Medical Physics

26. Questions?