Project Summary/Abstract: This proposal is to fund a complete refurbishment of the McLean Hospital 9.4 Tesla / 400 mm Agilent pre-clinical Magnetic Resonance Imaging system. This system is the largest active shield pre- clinical magnet in the world (there is a passive shield prototype magnet in Hefei, China) and provides scanning and spectroscopy for a range of subject species by using insertable gradient coils: a large gradient, ID = 260 mm; a middle gradient, ID = 115 mm; and a small gradient, ID=60 mm. This instrument has been productive since it was first installed in 2008 in studying a variety of species from mice through macaques for both morphometric imaging scans, functional magnetic resonance imaging (fMRI) and spectroscopy (MRS) in rodents and in non-human primates. This proposal is to refurbish and upgrade the system, bringing it to state-of-the-art technology so it is ready for the next decade of its service to the McLean Hospital research community. There are three motivations for upgrading this MR system at this time. First, its electronic equipment and gradient coils are 15 years old and are in need of replacement. Connectors and components within the electronics, are expected to fail in the next few years due to normal usage; the gradient coils are made of epoxy and subjected to strong vibration during scanning and need replacement before mechanical failure. These are common needs for MR systems with upgrades normally spaced 10 years apart. Second, this system was originally built by Varian, but was acquired by Agilent, who now provides technical support. Agilent has discontinued its MRI product line, and service and parts will cease to be available over the next few years – this application is for an upgrade to Bruker AVNEO electronics, which will then end our dependence on Agilent and instead will benefit from the full support of Bruker Inc. and offer a future development path. This upgrade is necessary for the system to continue operating. Third, due to its age, our 9.4T lacks many of the more advanced acquisition methods necessary for fMRI and MRS such as MPRAGE sequences, parallel acquisitions with RF array coils for fMRI, and two-dimensional, J-resolved spectroscopic imaging (MEGAPRESS) to name a few. The need for state-of- the-art hardware and acquisition methods drive this upgrade. The unique magnet upon which the system is based is in like-new condition and will last another 10-15 years or longer. Relevance: The McLean 9.4T scanner is one of the most capable systems in the US for pre-clinical scanning, providing imaging and spectroscopy for a wide range of species from mice to macaques. This upgrade will keep this scanner at the forefront of the field and will open up new opportunities for rapidly translating discoveries made in other animals to humans.