B1 field homogeneity and SAR calculations

doi:10.1088/0031-9155/46/2/324

B₁ field homogeneity and SAR calculations for the birdcage coil

T S Ibrahim et al 2001 Phys. Med. Biol. 46 609-619 doi: 10.1088/0031-9155/46/2/324

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T S Ibrahim^1,2, R Lee¹, B A Baertlein¹ and P-M L Robitaille^2,3
¹ Department of Electrical Engineering, The Ohio State University, 1320 Kinnear Road, Columbus, OH 43212, USA
² MRI Facility, The Ohio State University, 1630 Upham Drive, Columbus, OH 43210, USA
³ Author to whom correspondence should be addressed.
E-mail: robitaille.1@osu.edu

Abstract. The finite-difference time-domain (FDTD) method is used to model a birdcage resonator. All the coil components, including the wires, lumped capacitors and the source, are geometrically modelled together. As such, the coupling effects within the birdcage, including the interactions of coil, source and human head, are accurately computed. A study of the transverse magnetic (B₁) field homogeneity and the specific absorption rate (SAR) is presented on an anatomically detailed human head model at 64 and 200 MHz representing 1.5 and 4.7 T MRI systems respectively. Unlike that at 64 MHz, the B₁ field distribution is found to be inhomogeneous at 200 MHz. Also, high local SAR values are observed in the tissue near the source due to the coupling between the source and the head at 200 MHz.

Print publication: Issue 2 (February 2001)
Received 26 May 2000, in final form 30 October 2000

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B₁ field homogeneity and SAR calculations for the birdcage coil

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