Dielectric effect '''an explanation

1
Dielectric effect...an explanation
2
Agenda

• What is Dielectric Effect?
• Recommendations for Reducing the Dielectric
  Effect

3
What is Dielectric Effect?

• Dielectric effects appear as non-uniformity or
  shading in MR images.
• Caused by the shortening of RF wavelengths inside
  the body.
• How much they shorten varies by the tissue?

4
The Truth About Dielectric Effect

• Dielectric effects exist at all field strengths
• The effects are increased at higher field
  strengths
• The effects can be increased with multi-channel
  coils

5
Dielectric Effect in STIR
STIR
T2 FSE with Fat Sat
Courtesy of Dr. Tanenbaum, Edison Imaging
6
3.0T Physics Dielectric Effect
Multi-Channel Coils
Scanned with the body coil only
Scanned with 8-channel torso
Shading Is More Apparent Because of Higher SNR
7
3.0T Physics Dielectric Effect
Dielectric Pads Can Minimize the Effect That Is
Seen
High conductivity pad goes between the coil and
the patient
Dilute Manganese Chloride solution
8
3.0T Physics Dielectric Effect
Dielectric Pads Can Minimize the Effect That Is
Seen
No Pad
With Pad
Most effective means to reduce appearance of
dielectric effect may be use of pads in
conjunction with SCIC
With pad post SCIC
9
3.0T Physics Dielectric Effect
Dielectric Pads Can Minimize the Effect That Is
Seen
Pad placement
10
3.0T Physics Dielectric Effect
In Summary

• Dielectric effects are unavoidable with MR
  Imaging..no matter what field strength..
• There are many things that can be done to
  minimize the effects at 3.0T
• Muscle is much worse than fat wavelength 4
  times shorter
• All vendors are looking at ways to reduce the
  impact that these effects might have on the
  diagnostic quality of images