CfN High Field Workshop 4/9/08. Motivation for Workshop Highlight the upcoming delivery of a 7T whole-body MRI system at PennHighlight the upcoming delivery.

CfN High Field WorkshopCfN High Field Workshop4/9/084/9/08

Motivation for WorkshopMotivation for Workshop

• Highlight the upcoming delivery of a 7T Highlight the upcoming delivery of a 7T whole-body MRI system at Pennwhole-body MRI system at Penn

• Describe the potential benefits of 7T for basic Describe the potential benefits of 7T for basic and clinical neuroscience researchand clinical neuroscience research

• Begin to plan for 7T pilot projectsBegin to plan for 7T pilot projects

– ScienceScience

– InstrumentationInstrumentation

– RegulatoryRegulatory

Workshop ScheduleWorkshop 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

7T Project7T Project

• Supported by NCRR HEI Grant ($2M)Supported by NCRR HEI Grant ($2M)

– Ravi Reddy PIRavi Reddy PI

– CfN & LSNI projects contributed significantlyCfN & LSNI projects contributed significantly

– Other 7T MRI HEI to JHU, Vanderbilt, Pitt, NYUOther 7T MRI HEI to JHU, Vanderbilt, Pitt, NYU

– Total project cost ~$10MTotal project cost ~$10M

• First 7T whole-body system in regionFirst 7T whole-body system in region

– JHU held up due to siting issuesJHU held up due to siting issues

– ~20 7T sites worldwide~20 7T sites worldwide

Why 7T?Why 7T?

• Continue tradition of biomedical MRI developmentContinue tradition of biomedical MRI development

– Resource for Magnetic Resonance and Optical Research (NCRR RR)Resource for Magnetic Resonance and Optical Research (NCRR RR)

• Highest commercially-available field strengthHighest commercially-available field strength

– Few experimental whole-body systems at 8T, 9.4TFew experimental whole-body systems at 8T, 9.4T

– Cost (shielding) rises exponentially above 7TCost (shielding) rises exponentially above 7T

• Years of experience with Siemens 7T platformYears of experience with Siemens 7T platform

– System is now fully integratedSystem is now fully integrated

– Some product coils are also availableSome product coils are also available

– Software platform same as 1.5T and 3TSoftware platform same as 1.5T and 3T

Siemens 7 Tesla MRISiemens 7 Tesla MRI

• 7T Whole body magnet7T Whole body magnet– Weight 35000 kg Weight 35000 kg – UnshieldedUnshielded– Shield ~400 tonsShield ~400 tons– 90cm bore90cm bore– 2.4mx3.4 m longx3.8m2.4mx3.4 m longx3.8m– 5 ppm peak to peak over a 45 cm5 ppm peak to peak over a 45 cm

• Gradient systemGradient system– Based on Tim Trio gradientsBased on Tim Trio gradients– Resistive shims are tuned for 7TResistive shims are tuned for 7T– 45mT/m for longitudinal45mT/m for longitudinal– 40mT/m for horizontal and vertical direction40mT/m for horizontal and vertical direction– Max slew rate 200 mT/m/msMax slew rate 200 mT/m/ms– Minimal rise time 200 Minimal rise time 200 s, from 0 to 40 mT/m s, from 0 to 40 mT/m

amplitudeamplitude– Minimum slice thickness 0.1 mm (2D)Minimum slice thickness 0.1 mm (2D)

RF SystemRF System• 18 fully independent, fast receiver 18 fully independent, fast receiver

channelschannels– each with 1MHz bandwidth.each with 1MHz bandwidth.

• RF Power amplifierRF Power amplifier– 7kW RFPA, 280-300 MHz7kW RFPA, 280-300 MHz

– Parallel transmission in the futureParallel transmission in the future

• The following transmit receive RF coils The following transmit receive RF coils will be providedwill be provided– CP head (quadrature Tx/Rx)CP head (quadrature Tx/Rx)

– 24-channel head array coil24-channel head array coil

– TX/RX surface loop coilTX/RX surface loop coil

• Additional 3rd party coils include Additional 3rd party coils include Na/head, Tx/Rx head arrayNa/head, Tx/Rx head array

7T_head_PD_TSE_133x133

7T Fee Schedule7T Fee Schedule

• During initial 6 months of operation, scanning During initial 6 months of operation, scanning charges will not be implementedcharges will not be implemented

– Much of this time will be used to implement and Much of this time will be used to implement and validate sequences and protocolsvalidate sequences and protocols

– Also intended to stimulate early applicationsAlso intended to stimulate early applications

• At some point, hourly fees similar to the other At some point, hourly fees similar to the other resources will be implementedresources will be implemented

• 7T ProDev will also be available7T ProDev will also be available

7T Regulatory Process7T Regulatory Process

• IRB + CAMRIS, similar to 3TIRB + CAMRIS, similar to 3T

– CAMRIS review will be outsourced to a 7T-specific CAMRIS review will be outsourced to a 7T-specific committeecommittee

– 7T is not FDA approved, but remains minimal risk7T is not FDA approved, but remains minimal risk

• A 7T Techdev protocol will cover initial studiesA 7T Techdev protocol will cover initial studies

• The CfN will develop approved verbiage for 7T The CfN will develop approved verbiage for 7T protocols and consentsprotocols and consents

• Initial studies on healthy volunteersInitial studies on healthy volunteers

Known Advantages of 7TKnown Advantages of 7T• Increased sensitivityIncreased sensitivity

– Although sensitivity of MRI scales with field, a doubling of sensitivity (from 3T to 7T) only Although sensitivity of MRI scales with field, a doubling of sensitivity (from 3T to 7T) only translates to a 1.3X improvement in resolutiontranslates to a 1.3X improvement in resolution

– Major sensitivity advantage is for non-1H nuclei at standard resolutionMajor sensitivity advantage is for non-1H nuclei at standard resolution

• Increased spectral resolutionIncreased spectral resolution– Improvement in spectral quality for both 1H and multinuclearImprovement in spectral quality for both 1H and multinuclear

– May obviate the need for spectral editing for some resonancesMay obviate the need for spectral editing for some resonances

• Better ASLBetter ASL– T1 increases with field so improvement is >>linearT1 increases with field so improvement is >>linear

• Different BOLD contrastDifferent BOLD contrast– Susceptibility effects increase with field (but so does physiological noise)Susceptibility effects increase with field (but so does physiological noise)

– Spatial sensitivity changesSpatial sensitivity changes

1H Imaging at 7T1H Imaging at 7T• Susceptibility effects are dramatically increasedSusceptibility effects are dramatically increased

– Alters appearance of vasculature, iron & calcium depositsAlters appearance of vasculature, iron & calcium deposits– These may provide basis for altered parenchymal appearanceThese may provide basis for altered parenchymal appearance

8T MRI, Robitaille et al., JCAT 2000 7T MRI, Li et al., NeuroImage 2006

Phase Based ContrastPhase Based ContrastDuyn et al, PNAS 2007Duyn et al, PNAS 2007

MRA at 7TMRA at 7Tvon Morze et al, JMRI 2008von Morze et al, JMRI 2008

• N=5N=5

• GE SignaGE Signa

• 8-channel array8-channel array

• Identical resolutionIdentical resolution

3T 7T

Tolerability of 7TTolerability of 7TTheysohn et al, MAGMA 2008Theysohn et al, MAGMA 2008

ConclusionsConclusions

• 7T MRI will be ready for use this summer7T MRI will be ready for use this summer

– Coils available for brain and cortical regionsCoils available for brain and cortical regions

– BOLD fMRI, MRS, some ASL, Sodium imaging should BOLD fMRI, MRS, some ASL, Sodium imaging should be feasible soon after deploymentbe feasible soon after deployment

– Initial experience on healthy volunteers, but ambulatory Initial experience on healthy volunteers, but ambulatory patients will eventually be eligiblepatients will eventually be eligible

• Despite existence of human 7T for >5yrs, limited Despite existence of human 7T for >5yrs, limited literature on applicationsliterature on applications

– Opportunity to have fast impact with simple, good ideasOpportunity to have fast impact with simple, good ideas

– Successful applications could provide competitive Successful applications could provide competitive advantage for new grant applicationsadvantage for new grant applications