Radiofrequency Transmit and Revieve Upgrade for 3T Research Scanner

We propose to upgrade the radiofrequency (RF) capabilities of our 3T research scanner at the F.M. Kirby Research Center of the Hugo Moser Research Institute at Kennedy Krieger (KKI). The purpose is to remain a state-of-the-art MRI core facility by 1) extending the RF transmit capabilities to parallel transmit (TX) and upgrading to system release 3.0, and 2) increasing the number of head coil elements for brain studies to 32 receive channels. This is necessary to address the needs of many investigators at the KKI and Johns Hopkins University (JHU) who presently have 20 NIH-funded grants with several aims that can strongly benefit from the improved technical capabilities provided by this upgrade.

These investigators use the 3T system in the F.M. Kirby Research Center for structural MRI, functional MRI (fMRI), quantitative physiological MRI, magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI), and diffusion tensor imaging (DTI) of a large range of diseases and developmental disabilities. This proposed instrumentation will provide the following benefits:

1. Body coil TX /Release 3.0 system: upgrades us to the latest system software and hardware and expands our capabilities to multi-channel (parallel) RF transmit. The latter allows for RF transmit field optimization (B1+ shimming) to reduce dielectric shading at 3T, caused by the RF wavelength being on the order of the subject size. This is important for homogeneous image intensity and contrast, which benefits quantitative assessment of tissue volumes, metabolite levels, and other physiological parameters. In addition, the Release 3.0 upgrade will allow dynamic slice-by-slice B0 adjustment, providing increased local SNR, reduced spatial distortions, and better temporal stability for fMRI.

2. 32-channel 1H receive-only head coil: Currently, the brain studies in the grants listed use the 8- channel receive coil. Compared to this, the 32-channel coil increases cortical signal-to-noise ratio (SNR) by more than 50% and the coil design allows the efficient use of high acceleration factor SENSE imaging in all three directions. This is due to a large reduction in the noise-amplification factor (g-factor), which can be more than 40-80% depending on the acceleration rate and directions used.

   These primary advantages can be used to: a) better detect small signals (MRS) or small signal changes (fMRI); b) increase spatial resolution for all modalities; c) reduce scan times (i.e., yield shorter scans) for especially in 3D acquisition sequences for structural MRI and MRSI; d) reduce spatial distortions in fast single-shot acquisitions, such as used for DTI and fMRI. This 3T RF transmit/receive upgrade is essential for continued high-quality state-of-the-art research for the NIH-funded researchers at our institutions who are served by the core facilities of our NIH/NCRR Research Resource.

PUBLIC HEALTH RELEVANCE: The proposed system upgrades will benefit all researchers using the F.M. Kirby Research Center at the Hugo Moser Research Institute at Kennedy Krieger. The Center provides a core magnetic resonance facility within an interdisciplinary environment for the investigation of human anatomy, function and physiology. Cognitive functions including memory, attention, reading ability, and others are studied in conditions such as autism, Rett syndrome, and many other developmental disabilities. Other clinical applications include imaging studies of cancer (brain, breast), Huntington's disease, Alzheimer's disease, HIV, multiple sclerosis, cardiac disease, and rare metabolic disorders.