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A novel design scheme for monolithic transmission line resonators (TLRs) is presented - the multi-turn multi-gap TLR (MTMG-TLR) design. The MTMG-TLR design enables the construction of TLRs with multiple turns and multiple gaps. This presents an additional degree of freedom in tuning self-resonant TLRs, as their resonance frequency is fully determined by the coil geometry (e.g. diameter, number of turns, conductor width, etc.). The novel design is evaluated at 4.7T and 7T by simulations and experiments, where it is demonstrated that MTMG-TLRs can be used for MRI, and that the B1 distribution of MTMG-TLRs strongly depends on the number and distribution of turns. A comparison to conventional loop coils revealed that the B1 performance of MTMG-TLRs is comparable to a loop coil with the same mean diameter; however, lower 10g SAR values were found for MTMG-TLRs. The MTMG-TLR design is expected to bring most benefits at high static field, where it allows for independent size and frequency selection, which cannot be achieved with standard TLR design. However, it also enables more accurate geometric optimization at low static field. Thereby, the MTMG-TLR design preserves the intrinsic advantages of TLRs, i.e. mechanical flexibility, high SAR efficiency, mass production, and coil miniaturization.

The apparatus (1) is constituted by: device (3) for creating a homogeneous main magnetic static field (HO) orientated along a determined direction (Oz) in which static field there is placed the body (2) to be examined; devices for creating magnetic field gradients in a space of the body to be examined along three directions of the space; radio frequency excitation device (E) and a device (R) for the detection of the nuclear magnetic resonance signals produced by the body to be examined. The one, (Dx) of the devices for creating the gradients is constituted by a unilateral system wherein the device (6) for creating the magnetic field gradient along one direction (Ox) of the space are entirely situated on one and the same side of an "open" surface (P) while the body to be examined (2) is situated on the side of the surface (P) which is opposite to that where the device (6) is located, which are capable of creating a transverse gradient in relation to the direction (Oz) of the main static field, on the side of the surface where the body ( 2) to be examined is situated. Such a device (Dx) is particularly suitable for NMR imaging of the human skin.