A Phantom for use in an MR Imager

BME 400

October 14, 2005

Team Members:

• Missy Haehn (Team Leader)

• Can Pi (BSAC)

• Ben Sprague (Communications)

• Andrea Zelisko (BWIG)

Advisor:

• Professor Kristyn Masters

Client:

• Dr. Victor Haughton, M.D.

University of Wisconsin - MadisonBiomedical Engineering Design Courses

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2) Agrees not to use this information for any other purpose unless given writtenapproval in advance by the Project Group, the Client / SDC, and the Advisor.

3) Agrees to keep this information in confidence until the University and therelevant parties listed in Part (2) above have evaluated and secured anyapplicable intellectual property rights in this information.

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Medical Background• Spine consists of vertebrae and disks which

act as shock cushions• Disks begin to degenerate with age due to

reduced blood flow and water content• This causes disk density loss

and risk for vertebrae shifting• Patients suffer from back pain,

pinched nerves, muscle

spasms, bone spurs

MR Background

• MR imaging uses magnets and

radio waves to image body • T2 value is relaxation time for

protons, relative to water• Can essentially pick a point in the

body and ask “What type of tissue are you?”

• Phantoms are used to calibrate the scanner as well as in tissue simulations

Motivation

• Dr. Haughton is radiologist at • UW-Hospital with a specialty in

neuroradiology• Research interest in dynamic spine MR

imaging– Specifically disk degeneration

• Phantom needed for calibration of laboratory equipment– Mimicking intervertebral disks and T2 values

Client Design Specifications

• Hold artificial lumbar disk samples

• Contain samples with varying distances to the spinal coil

• Include solutions with known relaxation T2 times between 50 and 100 ms

• Sit securely atop of the spinal coil

• Is easy to use

Current Progress

• Current phantoms typically contain water doped solutions – have corresponding T1/T2 values

• Constructed by companies such as GE, Supertech, and CIRS

• Prices range from $2000 to $5000• Not directed towards

client’s specific research needs

Last Semester’s Design

Problems with First Design

• Stair structure was large and cumbersome

• Material used for structure showed up on MR image

• Samples were not close enough together– exposed to varying areas of magnetic field

• Disk mimicking samples separated into components over time

• Not a leak-proof design

Current Work: Phantom Material

• Visited Standard Imaging over summer and received plastic samples– Tissue mimicking– Blue water– Virtual water

• Tested samples in MR-found they show up on image and are ideal for x-ray applications

• New material to use: Acrylic– Commonly used in commercial and research

phantoms

Current Work: Disk Samples

• Need artificial disks to maintain integrity over time– Composed of water, collagen, and

proteoglycans

• Looking into gelatin, agarose, acrylamide, and alginates for substitutes– Tested gelatin and acrylamide in MR with

good results– Need to complete testing to decide which is

most cost and labor effective

Current Work: Physical Design

• Disk samples held close together

• Has spigot for easy fill and empty

• Able to hold ten samples-two in each tube

• Tight seal for phantom-no leaks

• Less cumbersome

Potential Problems

• Acrylic may show up on MR images• Artifacts from too many interfaces in

phantom– Water—plastic—air—glass—sample

• Fixed construction does not allow for much variety in experiments

• Artificial disk samples may not mimic disks accurately

• May need to construct platform so phantom is stable on the MR table/coil

Future Work

• Making more hydrogels to test and determining which to use

• Continued testing of Gd doped water samples

• Construction of phantom– Receiving quote from Acrylix.com– UW polymer processing lab

• TESTING!

References• Weidenbaum, M., et al. Correlating Magnetic Resonance Imaging

with the Biochemical Content of the Normal Human Intervertebral disk. J. Ortho Research. 10(4): 552-61.

• Lumbar Degenerative Disk Disease. DynoMed. 2/12/05. http://www.dynomed.com/encyclopedia/encyclopedia/spine/Lumbar_Degenerative_Disk_Disease.html.

• 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. 2001. Computerized Imaging Reference Systems, Inc. http:www.cirsinc.com/overview.html.

• Rice, J. Robin, et all. “Anthropomorphic 1H MRS head phantom.” Medical Physics, Vol. 25, No. 7, July 1998, Part 1.

• http://www.supertechx-ray.com/#MRI• http://www.cirsinc.com/productlist.html

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

Questions?