Subject-Specific, Non-Invasive Helmet-Restraint RF Coil for Awake, Non-Human Primate MR Imaging

The purpose of this study was to develop a noninvasive restraint helmet integrated with an radio frequency (RF) coil for awake-behaving non-human primate MR imaging. To prevent image-corrupting motion, the head needs to be immobilized, which is currently achieved via invasive surgical headpost implants. In this work, an RF coil holder was integrated into the design of a subject-specific helmet to place the coil in closest distance to the head for improved signal-to-noise ratio (SNR). Additive manufacturing was used to print the helmet based upon computed tomography images of the subject. A single channel transmit/receive loop coil was designed using electromagnetic simulations loaded with a voxel-based monkey head model. The Rhesus macaque used in this study underwent behavioral training based on positive reinforcement before engaging in MR imaging. Imaging was performed using the helmet coil, which was successful in immobilizing the macaque head in an awake, unanesthetized subject. Results showed improved SNR by approximately 30% compared to a loop coil used with an implanted head post, and minimal motion artifact in structural imaging. The non-invasive helmet coil eliminates the need for permanently implanting monkeys with a headpost, provides the necessary head immobilization, and allows the use of more subjects for neuroimaging studies.