Margaret Hart Surbeck Laboratory for Advanced Imaging
The mission of the Surbeck Laboratory is to create an optimal environment for cutting edge imaging research and education, contributing to translational science at UCSF across departments, campuses and affiliated institutions. The Laboratory serves as an intellectual hub through which over 100 researchers and staff conduct studies, develop new technologies, educate post-doctoral scholars, graduate and professional students, produce a large number of original research articles appearing in leading MR journals, and submit over 70 abstracts annually to the International Society of Magnetic Resonance in Medicine.
The state-of-the-art equipment includes GE 3T and 7T high field magnets, two Oxford Instruments hyperpolarizers, one prototype GE polarizer, and 500MHz and 600MHz Varian NMR instruments. The amenities for human subjects include reception area, changing room with lockers and restroom adjacent to interview and preparation rooms. There is a clean room for preparing hyperpolarized compounds for future human studies. Located at the opposite end of the laboratory is a suite for animal management that includes rooms for housing, preparation and surgery. Other crucial laboratory facilities are the MR Coil & Electronics Shop, the Fabrication and Machine Shop, and a server room dedicated to the heavy computational needs of the research programs in the building.
The 3T and 7T scanners are available to researchers on a recharge basis, with dedicated staff to assist in application development. These magnets have the latest technology from GEH with 32 receivers and a high speed / high volume data pipeline, multi-nuclear capability and high performance gradients. The 7T system is one of a handful of research systems constructed by GEH for collaborative development with academic partners. There are multiple exciters for dual-excitation, decoupling and multi-nuclear editing. The frequency converter allows imaging and spectroscopy with H-1, F-19, P-31, Na-23 and C-13 with decoupling and inverse detection capabilities. The system includes software for automated shimming of second order resistive shim coils. The prototype polarizer from GE Amersham is installed immediately adjacent to the 3T scanner in a custom designed clean room so that sterile agents can be produced for human studies.
7T MR 950 Upgrade
The new platform is critical for matching the new clinical systems currently being installed at UCSF and for expanding the capabilities of the 7T system to address the questions of interest to the research community. The following describes how the upgrade will impact the performance of the system.
Improved Gradients and RF System Stability
Gradient performance at higher field strengths suffers from a number of deficiencies due to greater strength and slew rate requirements to compensate higher chemical shift and susceptibility effects, as well as increased coil vibration due to higher Lorentz forces from the higher static field. In addition, reliance on fast imaging sequences often leads to a need for higher gradient duty cycles. The system upgrade described in this proposal addresses these problems through significant improvements in the design of the gradient coil and the gradient driver.
- The coil makes use of a far more efficient cooling system than the current generation of coils; heat extraction from the coil is roughly 25 kW, six times as efficient as the current design.
- Second, the driver control loop includes a feed-forward component that takes a model of the frequency-dependent coil impedance and so can compensate the interactions between the coil and the magnet.
- The higher current and voltage supplied by the driver, together with the increased cooling efficiency, will allow stable operation at higher duty cycles.
The improvements in the gradient system will combine with an rf subsystem that is more stable and flexible to facilitate the translation of fast chemical shift imaging methods developed at UCSF at 3T to 7T. Previous attempts to do this have been unsuccessful due to baseline distortions that were traced to uncompensated variations in the gradient waveforms. Fast MRI and MRSI methods will improve ongoing studies of multiple sclerosis, brain tumor, and dementia, by significantly reducing the acquisition time for spectroscopic imaging data and so reducing the sensitivity to subject motion. They will also support future pre-clinical studies of hyperpolarized 13C compounds at 7T.