Technical aspects: development, manufacture and installation of a cryo-cooled HTS coil system for high-resolution in-vivo imaging of the mouse at 1.5 T.

Signal-to-noise ratio improvement is of major importance to achieve microscopic spatial resolution in magnetic resonance experiments. Magnetic resonance imaging of small animals is particularly concerned since it typically requires voxels of less than (100 microm)(3) to observe the small anatomical structures having size reduction by a factor of more than 10 as compared to human being. The signal-to-noise ratio can be increased by working at high static magnetic field strengths, but the biomedical interest of such high-field systems may be limited due to field-dependent contrast mechanisms and severe technological difficulties. An alternative approach that allows working in clinical imaging system is to improve the sensitivity of the radio-frequency receiver coil. This can be done using small cryogenically operated coils made either of copper or high-temperature superconducting material. We report the technological development of cryo-cooled superconducting coils for high-resolution imaging in a whole-body magnetic resonance scanner operating at 1.5 T. The technological background supporting this development is first addressed, including HTS coil design, simulation tools, cryogenic mean description and electrical characterization procedure. To illustrate the performances of superconducting coils for magnetic resonance imaging at intermediate field strength, in-vivo mouse images of various anatomic sites acquired with a 12 mm diameter cryo-cooled superconducting coil are presented.