Scalable and modular 8-channel transmit and 8-channel flexible receive coil array for 19F MRI
An RF coil system originally developed for 19F cardiac MRI at 3 T.
It composes of an 8-channel transmit (Tx) and 8-channel flexible receive (Rx) coil array tuned to 115.9 MHz that can be used in combination with existing commercial 1H RF coils as the coil housing can be removed without moving the subject. The Tx coils were designed to have high transmit efficiency with homogeneous field distribution, and high sensitivity within the target volume of the heart.
For Tx coil design optimization, finite-difference time-domain (FDTD) simulations were performed to compare 8-channel independent loop elements to a high-pass birdcage coil for different subject sizes. To improve Tx efficiency, a coil housing was constructed that can be adapted to subjects of various sizes. An Rx coil array was designed to fit tightly on curved abdomens. The performance the 19F RF coil system was evaluated in silico, in phantom, and ex-vivo.
As the Tx coils are made of independent loop coil elements, they can be retuned to other frequencies and used for other applications as well. For frequency of operation until 128MHz, B1+ homogeneity is reasonable even with fixed phase and amplitude settings. For higher field strengths, RF shimming using a pTx system is needed. The number of channels can be reduced or increased. Since there is no decoupling elements between the coils, the distance between them should be large enough (>2cm) to prevent excessive coupling effects.
All the PCBs and component values, are available for reproducing the coils and the interface circuits.
1Divison of Medical Physics, Department of Radiology, University Medical Center Freiburg