Center for Advanced Magnetic Resonance Technology

Center for Advanced Magnetic Resonance Technology at Stanford

Research Emphasis

The mission of the Center for Advanced Magnetic Resonance Technology at Stanford is to develop innovative magnetic resonance (MR) techniques for fundamental anatomic, physiologic, and pathophysiologic studies involving animals and humans and to serve the academic and scientific community through collaborations, education, and access to center facilities and resources. Our core technology development encompasses the following six areas.

Reconstruction methods: Improved reconstruction methods and fast imaging sequences and a Web-based repository for data with a variety of k-space trajectories.

Imaging of brain activation: Susceptibility robust techniques as well as deconvolution and motion reduction methods for event relevant imaging.

Diffusion and perfusion imaging methods: Techniques for visualizing visualizing and mapping the functional aspects of tissue microvascular in diffusion, perfusion, and experimental brain activation at 1.5 T and 3 T, including tensor diffusion, exogenous and endogenous tracer perfusion, and BOLD and arterial spin-tagging techniques.

MR spectroscopy and multinuclear imaging (MRSI): Novel techniques for multivoxel two-dimensional MR spectroscopy, volumetric ¹H metabolic imaging, and ultrashort TE in vivo spectroscopy and imaging.

Cardiovascular structure and function: Visualizing cardiac and vascular anatomy for quantitating blood flow and hemodynamics.

Interventional imaging methods: Improved MR thermometry in the presence of susceptibility artifacts from ablation probe, develop methods for real-time feedback of thermometry data, and integrate an X-ray fluoroscopy system with our "open" MR magnet.

Current Research

Reconstruction methods: Reconstruction of very large three-dimensional (3-D) and four-dimensional (4-D) datasets; gridding reconstruction methods for non-Cartesian partial k-space reconstruction problems; tools to optimize gradient design for spiral imaging and to analyze and optimize variable density k-space trajectories in two and three dimensions; radiofrequency pulse design tools for fast imaging, steady-state acquisitions, and spectroscopic imaging specifically for 3 T and 7 T.

Imaging of brain activation: 3-D functional MR imaging (fMRI); localized resistive shimming methods; fMRI calibration methods; alternatives to BOLD contrast, including SSFP T2 and chemical shift weighted imaging; real-time fMRI for biofeedback-related neuroplasticity.

Diffusion and perfusion imaging methods: Quantitative assessment of tissue microperfusion and proton diffusion in stroke with the use of self-navigated multishot diffusion-weighted imaging (DWI) methods using variable-density and homodyne spiral sequences; parallel imaging enhancements to DWI; quantitative perfusion-weighted imaging toolboxes for optimizing the arterial input function through automated detection schemes; imaging of structural white matter integrity, including small field of view DW, improvements to the mapping of white matter anisotropy, software for analysis and display of directionality maps, framework to characterize diffusion in a heterogeneous environment (mathematical models of non-Gaussian diffusion), optimized magnetization transfer (MT) spiral sequence by adding adiabatic full and half-passage pulses, self-calibrating spiral parallel enhancements, and developing 2-D and 3-D relaxometry methods.

MRSI: 3 T volumetric J-resolved ¹H spiral MRSI including spectral quantitation methods; optimized 3 T volumetric J-resolved ¹H MRSI of the breast and prostate, including a phased-array compatible version of the pulse sequence along with the incorporation of readout gradient waveform designs and postacquisition algorithms aimed at minimizing motion artifacts; dual-tuned radiofrequency coils, direct- and indirect-detection pulse sequences, and optimized acquisition protocols for in vivo animal and human ¹³C MRS studies on at 7 T.

Cardiovascular structure and function: Improved pulse sequences for visualizing cardiac and vascular anatomy and for quantitating blood flow and hemodynamics, including short-spiral 3-D magnetic resonance angiography, multiple TI delayed enhancement, and a number of advanced phase contrast sequences; phase contrast reconstruction methods, including scanner-dependent calibrated eddy current correction and correction for gradient nonlinearity; analysis and visualization software for 4-D velocity data.

Interventional imaging methods: Real-time MR thermometry, including motion correction with local self-navigation; real-time temperature reconstruction and display software; methods for correlation of temperature maps with histology; improved MRI of frozen tissue by: 1) investigating MR parameters as a function of temperature, field strength, and tissue type; 2) investigating the unfrozen fraction; 3) investigating MT; 4) correlating the unfrozen fraction with MT; and 5) comparing MT with diffusion-weighted imaging after freezing.

BIRN

The center also is a partner in the Biomedical Informatics Research Network (BIRN) effort of NCRR. Specifically, the Center for Advanced Magnetic Resonance Technology provides direction for the Calibration Working Group of the FIRST-BIRN (fBIRN) and has developed much of the calibration methodology being used by the fBIRN.

Facilities

The center spans the School of Medicine and the School of Engineering. The central facility is the Richard M. Lucas Center for Magnetic Resonance Spectroscopy and Imaging, which has 1.5 T, 3.0 T, and 7.0 T GE Signa MRI systems; installation of a second 3.0 T GE scanner is in progress (summer 2006). Complete facilities are available for functional MRI, flow and motion experiments and molecular imaging. The 3 T suite also includes an electroencephalography, eyetracker, and physiologic monitoring systems. A second 1.5 T system in EE, a 7.0 T micro-Signa (31 cm) animal magnet in the adjacent Small-Animal Imaging Facility, and a GE Signa-SP interventional system in the adjacent Medical Center also support research and development efforts. Radiofrequency, electronics, and shop construction facilities are on site.

Publications

1. Santos, J. M., Cunningham, C. H., Lustig, M., et al., Single breath-hold whole-heart MRA using variable-density spirals at 3T. Magnetic Resonance in Medicine 55:371–379, 2006.

2. Kim, D. H. and Spielman, D. M., Reducing gradient imperfections for spiral magnetic resonance spectroscopic imaging. Magnetic Resonance in Medicine 56:198–203, 2006.

3. Yu, H., Reeder, S. B., McKenzie, C. A., et al., Single acquisition water-fat separation: feasibility study for dynamic imaging. Magnetic Resonance in Medicine 55:413–422, 2006.

4. Beatty, P. J., Nishimura, D. G., and Pauly, J. M., Rapid gridding reconstruction with a minimal oversampling ratio. IEEE Transactions on Medical Imaging 246:799–808, 2005.

5. Hsu, J. J. and Glover, G. H., Mitigation of susceptibility-induced signal loss in neuroimaging using localized shim coils. Magnetic Resonance in Medicine 53:243–248, 2005.

6. Thomason, M. E., Burrows, B. E., Gabrieli, J. D. E., and Glover, G. H., Breath holding reveals differences in fMRI BOLD signal in children and adults. NeuroImage 25:824-837, 2005.

7. Liu, C., Moseley, M. E., and Bammer, R., Simultaneous phase correction and SENSE reconstruction for navigated multi-shot DWI with non-cartesian k-space sampling. Magnetic Resonance in Medicine 54:1412–1422, 2005.

8. Wansapura, J. P., Daniel, B. L., Vigen, K. K., and Butts, K., In vivo MR thermometry of frozen tissue using R2* and signal intensity. Academic Radiology 12:1080–1084, 2005.