Magnetic Resonance Imaging at 7T in Glasgo Foster.pdfMagnetic Resonance Imaging at 7T in Glasgow ... •The NHS MR Physics Group is part of this... ... UK 7T •This will provide ...

Magnetic Resonance Imaging at 7T

in Glasgow

A unique opportunity!

An NHS MR Physicist's perspective...

• What is different about 7T scanners?

• What has already been achieved?

• Imaging Centre of Excellence (ICE)

– What's different about this site?

• Research opportunities available.

• Ensuring MR safety

What is different about 7T scanners?

Over 4 times stronger than existing

standard clinical scanners

These are not routine systems.

There are a limited number of

manufacturers.

Imaging coils are often not standard

and even bespoke.

Stronger magnet, more energy, more

signal.

Shajan Gunamony, now at UoG

Examples of what is possiblefrom other clinical research sites

Professor Chris Hess, UCSF School of Medicine

GE 7T installed since 2006

Ultra high resolution

Early Work - Comparing 3T & 7TT2* GRE - 6.5 min scan,

same parameters, 0.35 x 0.35 x 2.0 mm

Chris Hess, UCSF

3T 7T

Early Work - Pushing Spatial Resolution0.250 mm in-plane, 2 mm slice

Line of Gennari

Chris Hess, UCSF

Small vessel resolution

Polemini, MGH

Contrast - phase differences

From Susceptibility to Phase ContrastPhase Yields 10-fold Improvement in CNR over

Conventional MRI

Chris Hess, UCSF

3T 7T

Nuclear Substructuredepicted with 7T Phase

7T

3T

Magnitude Phase Chris Hess, UCSF

Contrast - susceptibility differences

Microscopic SusceptibilityT2* Contrast

MagnitudePhase Phase

χ<0 χ>0

Diamagnetic Paramagnetic

MagnitudePhase Magnitude Phase

B0 B0

Chris Hess, UCSF

Observations –T2* Contrast + Resolution

Chris Hess, UCSF

Anaplastic astrocytoma 9 years after EBRT

SWI of Radiation-Induced Microbleeds

Chris Hess, UCSF

Improved Depictionof Steno-occlusion

Closer Approximation to Catheter Angiography

7T

3T DSA

Chris Hess, UCSF

7T Multi-echo MRA+MRV

Simultaneous Visualization of Arteries, Veins & Microbleeds

Chris Hess, UCSF

Multi-band 7T NODDI: Low Grade Glioma

OD Viso Vic Vec

T1+ T2 FLAIR ADC FA

Qiuting Li et al, UCSF

Clinically feasible (5.5 minute) diffusion modeling of brain tissue

Getting the best out of 7Tbalance benefits with challenges

• Benefits of 7T:

– Signal (to noise ratio SNR), T1 and T2 relaxation,

– Chemical Shift (for spectroscopy)

• Challenges of 7T:

– Specific Absorption Rate (SAR), RF Uniformity

– Ergonomics, Motion correction/detection

– Susceptibility

Problem: RF Inhomogeneity

Nonlinear SNR and Contrast, SAR Hotspots

Chris Hess, UCSF

And then this came along…

Siemens Magnetom Terra

First research 7T system designed for future clinical use.

Although weighing 25 tons it is about half the weight of previous designs!

Siemens Magnetom Terra

After Erlangen, Wurzburg and Cambridge,

Glasgow will have the fourth in the world of this new design system.

It will be delivered on 27th November 2016 – just before St Andrew’s Day!

Siemens Magnetom Terraspecifications

Research and DevelopmentIntroducing ICE

Clinical lead for research

“For my own specialism in stroke, the 7T MRI

scanner will allow us to produce detailed images of

the damage caused by stroke and give us the

capability of visualising the very small vessels

responsible for many strokes.”

Prof Keith Muir

“What sets Glasgow’s 7T scanner apart from those at other sites.. indeed internationally – is that it will be housed at a hospital.”

“Most other facilities.. handle patients who can walk into a university research building, but we’ll ..bring patients in their beds from the hospital into the ICE building to use the scanner.”

Prof Keith Muir

Clinical lead for research

Direct from patient bed-sideto scanner table

• The ICE building has been designed to ensure that the 7T imaging facility is completely integrated within a university hospital campus allowing direct access to the 7T from all patient groups.

• Other sites around the world are in separate research sites remote from the hospital or if nearby still requiring transport.

QEUH campus

7T will actually be sited at the very first location of MRI in Glasgow.

Connectivity.....

Learning & Teaching Building, Innovation Floor

Main Acute Hospital

Clinical Research Facility

Imaging Centre of Excellence (ICE)

Unique partnerships on site

• This facility unlocks the potential for ultra high field MRI based clinical research within the hospital campus.

• This facility has been made possible by a “triple helix approach” of partnership between the University of Glasgow, NHSGGC and Siemens.

A truly national resource

• The Imaging Centre of Excellence will bring together teams of clinical researchers, industry and academics.

• It will build on strong collaborations already existing at 1.5T and 3.0T

• There is now a strong desire in the industry to drive 7T to clinical especially since the static field limit is now 8T.

• Initial focus will be head but this will develop to other areas.

Translational research

• Ensuring the research activity reaches the patient is a role that NHS Researchers are well placed for.

• The NHS MR Physics Group is part of this...

• It comes with the same software platform as clinical 3T and 1.5T models aiding translational research between field strengths..

• The scanner is expected to be operational from April 2017

7T enables…

At a sub millimetre resolution;

– Structure

• Variations in myelin and iron content

– Function

• Grey matter and white matter

• Variations in signal across the cortex

– Connectivity

• rsfMRI at 1mm isotropic

• Layer based fMRI responses

Provided subject motion correction or detection

strategies can be utilised!

• Accurate RF modelling is critical

• Importance of inter-site site comparison to confirm image quality and RF deposition.

Ensuring MR Safety

• The use of numerical simulations on generic models remains the most widely used SAR evaluation method.

• Different safety factors are typically added to account for coil modelling errors, anatomic variability and uncertainties associated with the monitoring hardware.

• SAR and temperature can now be explicitly taken into account in pTx RF pulse design.

• Thermal dose likely to prove to be even more useful metric.

Ensuring MR Safety

• Establish live patient RF safety modelling and pTxoptimisation to increase feasibility of clinical research neuro scanning at 7T and other body areas by collaborating with appropriate sites.

• Many MR conditional implants are not yet tested to 7T and so accurate modelling is required. Sites such as MDC in Berlin have done extensive work on this.

Maintaining safety…

UK 7T

• This will provide a UK network with Glasgow taking a lead on patient safety.

• A standardised head imaging protocol will be set up.

• Develop exchange programmes with major 7T sites such as Oxford, Cambridge, Nottingham, Cardiff, as well as international sites.

Any questions?

[email protected]