RF induced temperature elevation near metallic wires in clinical magnetic resonance imaging

Abstract

Heating of biological tissues along metallic wires placed in MRI scanner has become an important question with the development of interventional MRI. In order to assess thermal response to RF exposure during MR procedures, the temperature elevation was studied near metallic non-magnetic wires. All tests have been performed on a 1.5 T clinical scanner. The major issue is to insure patient safety against potential heating of tissues located in the metallic wire vicinity. Three experiments were conducted: the first investigate the wire diameter, the second the excitation angle, and the third, the temperature distribution along the wire. This study shows that the temperature decreases with the diameter wire. The temperature range increases quadratic with excitation angle. Heating has also been observed along the wire, and results indicate that heating peaks are located according to electrical length of the wire. In the close vicinity of the wire, an important heating (40 O C rise) has been observed.Electromagnetic simulations of experimental set up were made assuming a plane wave excitation with FEKO software. Correlations between measured and calculated values of electric field are presented.

Experimental and numerical assessment of MRI‐induced temperature change and SAR distributions in phantoms and in vivo

“…As discussed above, there was negligible contribution from thermal conduction (the first term on the right‐hand side of Eq. 1) during this period, so that SAR could be estimated from the change in temperature as where c phantom is the heat capacity of the phantom (approximately 4200 J/kg/°C (12) and Δ t is the period of heating, or 120 sec.…”

MRI Fundamentals: RF Aspects of Magnetic Resonance Imaging (MRI)

“…This is especially important if the patient has implants such as pacemakers or stents [49]. Work is currently being done [51]- [56] to study ways to determine and measure the temperature in these hot spots. For example, temperature mapping can be performed by looking closely at phase shifts in the T1 relaxation time within the ROI [57].…”

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“…The applications of this kind of systems are unlimited (design of microwave devices, analysis of antennas, radomes, reflectarrays, electromagnetic compatibility, etc.) and they can be used not only in engineering, but also in other scopes like medicine [7]. On the other hand, researchers may take advantage of the parallel versions due to the new power characteristics of actual computers such as high speed and enormous amount of memory.…”