English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Compensation of magnetic field distortions from paramagnetic instruments by added diamagnetic material: measurements and numerical simulations

Müller-Bierl, B., Graf, H., Steidle, G., & Schick, F. (2005). Compensation of magnetic field distortions from paramagnetic instruments by added diamagnetic material: measurements and numerical simulations. Medical Physics, 32(1), 76-84. doi:10.1118/1.1828674.

Item is

Basic

show hide
Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-D67D-D Version Permalink: http://hdl.handle.net/21.11116/0000-0004-DCE3-4
Genre: Journal Article

Files

show Files

Locators

show
hide
Description:
-

Creators

show
hide
 Creators:
Müller-Bierl, B1, Author              
Graf, H, Author
Steidle, G, Author
Schick, F, Author
Affiliations:
1External Organizations, ou_persistent22              

Content

show
hide
Free keywords: -
 Abstract: In minimally invasive procedures guided by magnetic resonance (MR) imaging instruments usually are made of titanium or titanium alloys (e.g., nitinol), because other more MR-compatible materials often cannot provide sufficient mechanical properties. Artifacts depending on susceptibility arise in MR images due to incorrect spatial encoding and intravoxel dephasing and thereby hamper the surgeon's view onto the region of interest. To overcome the artifact problem, compensation of the paramagnetic properties by diamagnetic coating or filling of the instruments has been proposed in the literature. We used a numerical modeling procedure to estimate the effect of compensation. Modeling of the perturbation of the static magnetic field close to the instruments reflects the underlying problem and is much faster and cost efficient than manufacturing prototypes and measuring artifact behavior of these prototypes in the MR scanner. A numerical model based on the decomposition of the susceptibility distribution in elementary dipoles was developed by us. The program code was written object oriented to allow for both maximum computational speed and minimum random access memory. We used System International units throughout the modeling for the magnetic field, allowing absolute quantification of the magnetic field disturbance. The field outside a simulated needlelike instrument, modeled by a paramagnetic cylinder (out of titan, chi =181.1) of length 8.0 mm and of diameter 1.0 mm, coated with a diamagnetic layer (out of bismuth, chi=-165.0) of thickness 0, 0.1, 0.2, 0.3, and 0.4 mm, was found to be best compensated if the cross-sectional area of the cylinder, multiplied by the absolute susceptibility value of the cylinder material, is equal to the cross-sectional area of the coating, multiplied by the absolute susceptibility value of the coating material. At the extremity of the coated cylinder an uncompensated field distortion was found to remain. We studied various tip shapes and geometries using our computational model: Suitable diamagnetic coating or filling of paramagnetic instruments clearly reduced tip artifacts and diminished the dependency of artifact size on orientation of the instrument with respect to B0 in the numerical studies. We verified the results of the simulations by measuring coated and uncoated titanium wires in a 1.5 T MR scanner.

Details

show
hide
Language(s):
 Dates: 2005-01
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: BibTex Citekey: 4818
DOI: 10.1118/1.1828674
 Degree: -

Event

show

Legal Case

show

Project information

show

Source 1

show
hide
Title: Medical Physics
  Other : Med. Phys.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: New York, etc. : Published for the American Association of Physicists in Medicine by the American Institute of Physics
Pages: - Volume / Issue: 32 (1) Sequence Number: - Start / End Page: 76 - 84 Identifier: ISSN: 0094-2405
CoNE: https://pure.mpg.de/cone/journals/resource/991042742884000