Stretchable coil arrays: application to knee imaging under varying flexion angles.

To fit high-density receiver arrays for MRI closely around individual target anatomies, there is a need to provide a high degree of geometric adjustability with ease of handling and patient comfort. In this work, this is accomplished by the construction of a coil array that is stretchable such that it automatically conforms to a given anatomy's shape and size. Stretchability is implemented by creating the coil conductors from braided wire mounted on an elastic textile substrate. The signal-to-noise ratio yield of such coils is measured by MRI experiments at 3 T, and the signal-to-noise ratio effect of coil stretching is investigated with and without adjustment of the matching between each coil and the respective preamplifier. Four-channel and eight-channel arrays of stretchable receiver coils are evaluated in phantoms as well as for in vivo imaging of the human knee. Exploiting stretchability, it is demonstrated that the knee can be imaged under varying flexion angles up to 60° while maintaining closely coupled array detection, high signal-to-noise ratio, and uniform coverage of the entire joint.