A double end-cap birdcage RF coil for small animal whole body imaging

Proper design of a birdcage coil plays a very important role in obtaining high-resolution small animal magnetic resonance imaging. The RF field homogeneity and the coil filling factor directly affect the signal-to-noise ratio (S/N) and therefore limit the resolution. It has been shown that a conductive end-cap placed on one side of the coil can improve the RF field inhomogeneity near this area. This also contributes to an increase in the S/N by reducing the length of the RF coil. While this is true near the end-cap, the distal half of the coil still suffers from poor homogeneity and S/N. Consequently, such a shortfall may hinder small animal whole body imaging. In order to improve the coil performance for a larger imaging volume, we designed a new small animal birdcage RF coil by adding a detachable second end-cap to the open end. The performance of single end and double end RF coils was compared experimentally. The results indicate that the double end-cap can provide superior uniformity along the long axis of the coil. Furthermore, if one wishes to obtain the same homogeneity within a given volume, a double end-cap would have less than half of the length of the single end-cap coil leading to a superior S/N performance.