Download Magnetic Resonance Imaging at 7 Tesla in Glasgow

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 possible
from other clinical research sites
Professor Chris Hess,
UCSF School of
Medicine
GE 7T installed since
2006
Ultra high resolution
Early Work - Comparing 3T & 7T
T2* GRE - 6.5 min scan,
same parameters, 0.35 x 0.35 x 2.0 mm
3T
7T
Chris Hess, UCSF
Early Work - Pushing Spatial Resolution
0.250 mm in-plane, 2 mm slice
Line of Gennari
Chris Hess, UCSF
Small vessel resolution
Polemini, MGH
Contrast - phase differences
From Susceptibility to Phase Contrast
Phase Yields 10-fold Improvement in CNR over
Conventional MRI
3T
7T
Chris Hess, UCSF
Nuclear Substructure
depicted with 7T Phase
7T
3T
Magnitude
Phase
Chris Hess, UCSF
Contrast - susceptibility differences
Microscopic Susceptibility
T2* Contrast
B0
Diamagnetic
Paramagnetic
χ<0
B0
χ>0
Phase
Phase
Magnitude
Magnitude
Magnitude
Phase
Phase
Chris Hess, UCSF
Observations –
T2* Contrast + Resolution
Chris Hess, UCSF
SWI of Radiation-Induced Microbleeds
Anaplastic astrocytoma 9 years after EBRT
Chris Hess, UCSF
Improved Depiction
of Steno-occlusion
Closer Approximation to Catheter Angiography
3T
DSA
7T
Chris Hess, UCSF
7T Multi-echo MRA+MRV
Simultaneous Visualization of Arteries, Veins & Microbleeds
Chris Hess, UCSF
Multi-band 7T NODDI:
Low Grade Glioma
Clinically feasible (5.5 minute) diffusion modeling of brain tissue
OD
Viso
Vic
Vec
T1+
T2 FLAIR
ADC
FA
Qiuting Li et al, UCSF
Getting the best out of 7T
balance 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 Terra
specifications
Research and Development
Introducing 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
Clinical lead for research
“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
Direct from patient bed-side
to 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.....
Main Acute Hospital
Imaging Centre of
Excellence (ICE)
Clinical Research
Facility
Learning &
Teaching Building,
Innovation Floor
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!
Ensuring MR Safety
• 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.
Maintaining safety…
• Establish live patient RF safety modelling and pTx
optimisation 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.
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]