Zusammenfassung
High‐field RF volume coils for the human limbs and heads are commonly formed from rigid cylinders. For extremity imaging this design often requires using larger one‐size‐fit‐all volume coils that decrease transmission efficiency and SNR. Splitting the coil solves this problem by providing tighter fit. It also improves patient access by eliminating the need for the coil to be slid over the region of interest. Split unshielded birdcage volume coils have been described previously for field strengths up to 3 T. For birdcage coils a direct electrical connection between two halves of the coil is required. For high‐field (>3 T) shielded birdcage coils, both the shield and the coil must be split and reliably connected electrically, which complicates the design. This problem can be circumvented by the use of split TEM volume coils. Since the elements of a TEM coil are coupled inductively, no direct electrical connection between the halves is necessary. In this study we demonstrate that the effects of splitting the shield for head and knee TEMs can be compensated for, and performance retained. For the knee, the improved access allowed the coil diameter to be reduced, enhancing the sensitivity by 15–20%.
