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Surface coil with reduced specific absorption rate for rat MRI at 7 T
Sergio E Solis-Najera1, Rodrigo Martin1,2, Fabian Vazquez1
1Department of Physics, Faculty of Sciences, Universidad Nacional Autonoma de Mexico, 04510, Mexico, D.F., Mexico.
Objective:
A scaled-down slotted surface radio frequency (RF) coil was built, and the specific absorbance rate (SAR) in 100 mg of tissue (SAR100 mg) produced in a rat brain phantom was computed at 7 T.
Materials And Methods:
A slotted coil 2-cm in diameter with six circular slots was developed. Its theoretical and experimental performance was computed and compared using the signal-to-noise ratio (SNR) expression and phantom images obtained with a spin echo sequence. Electromagnetic simulations were performed using the finite integral method with saline sphere and rat brain phantoms. SAR100 mg was computed for the circular coil, by varying its radius, and was also computed for the slotted coil.
Results:
The slotted coil quality factor gave a twofold increment over the circular coil, and noise was reduced by 17%. The experimental SNR of the slotted coil produced a 30% improvement for points near the coil plane. The theoretical and experimental results showed substantial agreement. Axial map histograms and profiles showed greater SAR100 mg values for the circular coil than for the slotted coil.
Conclusions:
The slotted surface coil offers improved performance and low SAR100 mg for rat brain imaging at 7 T. This approach may be used with new RF coils to investigate SAR in humans.
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