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CfN High Field Workshop 4/9/08

CfN High Field Workshop 4/9/08. Motivation for Workshop. Highlight the upcoming delivery of a 7T whole-body MRI system at Penn Describe the potential benefits of 7T for basic and clinical neuroscience research Begin to plan for 7T pilot projects Science Instrumentation Regulatory.

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CfN High Field Workshop 4/9/08

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  1. CfN High Field Workshop4/9/08

  2. Motivation for Workshop • Highlight the upcoming delivery of a 7T whole-body MRI system at Penn • Describe the potential benefits of 7T for basic and clinical neuroscience research • Begin to plan for 7T pilot projects • Science • Instrumentation • Regulatory

  3. Workshop Schedule • 9:00 Welcome and Introduction to 7T Imaging (me) • 9:15 BOLD fMRI: Opportunities and Pitfalls (Mark Elliott) • 9:45 1H Spectroscopy (Harish Poptani) • 10:15 Coffee Break • 10:30 Multinuclear Imaging (Ravinder Reddy) • 11:00 ASL (Jiongjiong Wang) • 11:30 Discussion of Potential Projects and Instrumentation

  4. 7T Project • Supported by NCRR HEI Grant ($2M) • Ravi Reddy PI • CfN & LSNI projects contributed significantly • Other 7T MRI HEI to JHU, Vanderbilt, Pitt, NYU • Total project cost ~$10M • First 7T whole-body system in region • JHU held up due to siting issues • ~20 7T sites worldwide

  5. Why 7T? • Continue tradition of biomedical MRI development • Resource for Magnetic Resonance and Optical Research (NCRR RR) • Highest commercially-available field strength • Few experimental whole-body systems at 8T, 9.4T • Cost (shielding) rises exponentially above 7T • Years of experience with Siemens 7T platform • System is now fully integrated • Some product coils are also available • Software platform same as 1.5T and 3T

  6. Siemens 7 Tesla MRI • 7T Whole body magnet • Weight 35000 kg • Unshielded • Shield ~400 tons • 90cm bore • 2.4mx3.4 m longx3.8m • 5 ppm peak to peak over a 45 cm • Gradient system • Based on Tim Trio gradients • Resistive shims are tuned for 7T • 45mT/m for longitudinal • 40mT/m for horizontal and vertical direction • Max slew rate 200 mT/m/ms • Minimal rise time 200 ms, from 0 to 40 mT/m amplitude • Minimum slice thickness 0.1 mm (2D)

  7. RF System • 18 fully independent, fast receiver channels • each with 1MHz bandwidth. • RF Power amplifier • 7kW RFPA, 280-300 MHz • Parallel transmission in the future • The following transmit receive RF coils will be provided • CP head (quadrature Tx/Rx) • 24-channel head array coil • TX/RX surface loop coil • Additional 3rd party coils include Na/head, Tx/Rx head array 7T_head_PD_TSE_133x133

  8. 7T Fee Schedule • During initial 6 months of operation, scanning charges will not be implemented • Much of this time will be used to implement and validate sequences and protocols • Also intended to stimulate early applications • At some point, hourly fees similar to the other resources will be implemented • 7T ProDev will also be available

  9. 7T Regulatory Process • IRB + CAMRIS, similar to 3T • CAMRIS review will be outsourced to a 7T-specific committee • 7T is not FDA approved, but remains minimal risk • A 7T Techdev protocol will cover initial studies • The CfN will develop approved verbiage for 7T protocols and consents • Initial studies on healthy volunteers

  10. Known Advantages of 7T • Increased sensitivity • Although sensitivity of MRI scales with field, a doubling of sensitivity (from 3T to 7T) only translates to a 1.3X improvement in resolution • Major sensitivity advantage is for non-1H nuclei at standard resolution • Increased spectral resolution • Improvement in spectral quality for both 1H and multinuclear • May obviate the need for spectral editing for some resonances • Better ASL • T1 increases with field so improvement is >>linear • Different BOLD contrast • Susceptibility effects increase with field (but so does physiological noise) • Spatial sensitivity changes

  11. 1H Imaging at 7T • Susceptibility effects are dramatically increased • Alters appearance of vasculature, iron & calcium deposits • These may provide basis for altered parenchymal appearance 8T MRI, Robitaille et al., JCAT 2000 7T MRI, Li et al., NeuroImage 2006

  12. Phase Based ContrastDuyn et al, PNAS 2007

  13. MRA at 7Tvon Morze et al, JMRI 2008 3T 7T • N=5 • GE Signa • 8-channel array • Identical resolution

  14. Tolerability of 7TTheysohn et al, MAGMA 2008

  15. Conclusions • 7T MRI will be ready for use this summer • Coils available for brain and cortical regions • BOLD fMRI, MRS, some ASL, Sodium imaging should be feasible soon after deployment • Initial experience on healthy volunteers, but ambulatory patients will eventually be eligible • Despite existence of human 7T for >5yrs, limited literature on applications • Opportunity to have fast impact with simple, good ideas • Successful applications could provide competitive advantage for new grant applications

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