CfN High Field Workshop 4/9/08

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CfN High Field Workshop4/9/08
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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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Workshop Schedule

• 900 Welcome and Introduction to 7T Imaging (me)
• 915 BOLD fMRI Opportunities and Pitfalls (Mark
  Elliott)
• 945 1H Spectroscopy (Harish Poptani)
• 1015 Coffee Break
• 1030 Multinuclear Imaging (Ravinder Reddy)
• 1100 ASL (Jiongjiong Wang)
• 1130 Discussion of Potential Projects and
  Instrumentation

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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

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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

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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)

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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
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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

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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

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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
  gtgtlinear
• Different BOLD contrast
• Susceptibility effects increase with field (but
  so does physiological noise)
• Spatial sensitivity changes

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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
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Phase Based ContrastDuyn et al, PNAS 2007
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MRA at 7Tvon Morze et al, JMRI 2008
3T
7T

• N5
• GE Signa
• 8-channel array
• Identical resolution

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Tolerability of 7TTheysohn et al, MAGMA 2008
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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 gt5yrs, limited
  literature on applications
• Opportunity to have fast impact with simple, good
  ideas
• Successful applications could provide competitive
  advantage for new grant applications