Spatial distribution of RF-induced E-fields and implant heating in MRI.
The purpose of this study was to assess the distribution of RF-induced E-fields inside a gel-filled phantom of the human head and torso and compare the results with the RF-induced temperature rise at the tip of a straight conductive implant, specifically examining the dependence of the temperature rise on the position of the implant inside the gel. MRI experiments were performed in two different 1.5T MR systems of the same manufacturer. E-field distribution inside the liquid was assessed using a custom measurement system. The temperature rise at the implant tip was measured in various implant positions and orientations using fluoroptic thermometry. The results show that local E-field strength in the direction of the implant is a critical factor in RF-related tissue heating. The actual E-field distribution, which is dependent on phantom/body properties and the MR-system employed, must be considered when assessing the effects of RF power deposition in implant safety investigations.
Nordbeck
Peter
P
Medizinische Klinik und Poliklinik I, Universität Würzburg, Würzburg, Germany. nordbeck@physik.uni-wuerzburg.de
Fidler
Florian
F
Weiss
Ingo
I
Warmuth
Marcus
M
Friedrich
Michael T
MT
Ehses
Philipp
P
Geistert
Wolfgang
W
Ritter
Oliver
O
Jakob
Peter M
PM
Ladd
Mark E
ME
Quick
Harald H
HH
Bauer
Wolfgang R
WR
D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D003198:Computer Simulation; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D019736:Prostheses and Implants; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation