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Late in 2005, the ISMRM study groups were
asked to compile lists of key unsolved problems and unmet needs in their
areas of interest. Here are the results:
MR Engineering
RF
1. Wireless
or optical transmission of the MR signal out of the bore, to facilitate
the use of large receiver coil arrays.
2. What
number of channels is optimal/required for both receive (Parallel
Imaging) and transmit (Transmit SENSE) .
3. SAR:
how to control SAR at high fields (> 3T), how to know where the hot
spots are in vivo, how to monitor the SAR in the human body in real
time.
Magnets, Shim
and Gradient Coils
4. Length
of magnet/bore: how short can it be? What are the limits in openness?
5. Actively
shielded > 7 T whole body magnets.
6. Dynamic
shimming: development of shim coils that can be used in dynamic shimming
(strong, low inductance, actively shielded) and quantification of the
advantages to be gained via dynamic shimming.
7. Reduction
of acoustic noise to due switched magnetic field gradients, especially
at high field.
8. Methods
for imaging without the use of pulsed field gradients.
Scanners
9. Methods
for Precise QA of the MRI scanner in terms of SNR/
stability/ distortion/ artifacts and differences between MR methods.
Currently, the lack of such methods limit the pooled use of MR data
generated from different scanners/vendors.
10.
Practical methods for
measuring the electrical properties of tissues using MRI.
11.
Methods for increasing patient
throughput - can we produce an order-of-magnitude improvement in any
way (parallel imaging, higher field, dockable tables, etc.) in the time
needed to image (leading to a reduction in scanning costs).
General
12.
A discussion board to draw an
active group of engineers together for dissemination of knowledge and
experience, rather than retainment in individual labs.
High-Field
Systems and Applications
I. Hardware
1. Solutions
for the transmit B1 inhomogeniety at high field due to
wavelength/dielectric effects.
2. Development
of standardized method for SAR monitoring and setting SAR limits for
multiple local transmit coils.
3. Development
of transmit SENSE at ultra-high field, along with development of
algorithms for determining the phase and amplitude of the RF for each
driven element in a coil, such as a TEM coil.
4. Acoustic
noise reduction at high field.
5. Low
noise, high fidelity, and powerful gradient amplifiers.
6. Development
of an actively shielded 7 T whole-body sized magnet.
II. Applications
7. Fast
CSI pulse sequences.
8. Pulse
sequences for clinical applications of hetero-nucleus imaging (such as
3Li, 31P, 17O, etc.)
9. Detection
of molecular probes that can pass through the blood-brain barrier and
selectively bind to specific cells or tissues.
10.
A method for identifying areal
boundaries via high resolution MRI (to allow definition of functional
areas on individual subjects).
III. Misc.
11.
Long-term health consequences
of exposure to very high magnetic field.
12. Methods
to remove magnetic susceptibility-induced image distortion.
Diffusion &
Perfusion
The Top
Twenty -- If only we could:
1. “Definitively
quantify the contributions of the intra- and extra-cellular components
to the diffusion signal” [Score = 30; Number of votes = 9]
2. “Measure
brain perfusion in acute stroke patients accurately enough to be useful”
[Score = 27; Number of votes = 7]
3. “Have
realistic phantoms for diffusion imaging”
[Score = 26; Number of votes = 11]
4. ”Quantify
connectivity between different regions, separated by different
distances, reliably and consistently”
[Score = 25; Number of votes = 8]
5.
“Have an accepted and
practical gold standard for tract tracing in the human brain”
[Score = 23; Number of votes = 7]
6. “Reliably
measure the vascular territories of individual arteries”
[Score = 21; Number of votes = 6]
7. “Better
understand the biophysical nature of diffusion MR signal, in order to
optimize diffusion experiments more effectively”
[Score = 20; Number of votes = 4]
8. “Have
a definitive, reproducible and easy way of calibrating ASL experiments
with respect to M0 (of tissue or blood, depending on the model) in order
to get quantitative CBF values”
[Score = 18; Number of votes = 4]
9.
“Use diffusion-derived measures, other than the mean diffusivity, in a
clinical manner”
[Score = 16; Number of votes = 5]
10. “Have
standard post-processing software (including motion correction) for ASL
integrated onto a clinical scanner”
[Score = 16; Number of votes = 5]
11.
“Perform meaningful group comparisons on low dimensionality diffusion
data (scalar invariants of the tensor), even if we don’t understand the
biophysical mechanisms underlying them” / “Perform meaningful voxel-based
comparisons of DTI data”
[Score = 16; Number of votes = 4]
12.
“Reliably quantify the
dependence of diffusion on diffusion time, to identify different tissue
types or geometrical features”
[Score = 15; Number of votes = 5]
13.
“Have realistic phantoms for
perfusion imaging”
[Score = 15; Number of votes = 5]
14.
“Use DTI to reliably
discriminate tumor infiltration from bland (tumorfree) edema”
[Score = 14; Number of votes = 5]
15.
“Use arterial spin labeling to
measure perfusion in white matter”
[Score = 14; Number of votes = 3]
16.
"Establish the definitive
biophysical mechanism underlying the dependence of ADC on the b-value in
the brain".
[Score = 12; Number of votes = 4]
17.
“Resolve the topological
ambiguity in diffusion displacement profiles (cross, kiss, twist, bend)”
[Score = 11; Number of votes = 4]
18.
“Reach a common consensus,
once and for all, on the number of directions needed for DTI, and the b-
values needed (i.e., do we need b < 600 s/mm2 or b> 3000 s/mm2)”
[Score = 11; Number of votes = 4]
19.
“Identify the cellular
correlates of changes in diffusion anisotropy in white matter”
[Score = 11; Number of votes = 5]
20. “Know
whether FA abnormalities in specific fibers correlate with fMRI
abnormalities in gray matter (i.e., use DTI to predict the outcome of
fMRI experiments)” / “Identify the functional basis and the functional
meaning of DTI”
[Score = 10; Number of votes = 5]
Dynamic MR
1) A hand-held MRI scanner. The NMR mouse exists and is
capable of measuring spectra
at very small depths. However, for hand held medical imaging
we would need to
a. Create a reasonably homogeneous B0 field penetrating the body to
organ depth.
b. Overcome B0 field inhomogeneities.
c. Create reasonably linear B0 gradients
d. Compensate for the residual non-linearity of the gradients.
e. Have MRI sequences with only adiabatic pulses
f. Have enough B1 penetration for the adiabatic pulse without
exceeding SAR limits.
2) Create “The mother of all sequences” (so named by Paul
Bottomley), a truly high resolution
3D pulse sequence that in a reasonably short scan time
measures spin density, T1 and T2.
Then use this information to generate any slice at any
oblique angle with any T1 or T2 weighted
contrast. This would replace the series of scout images,
oblique scouts, T1 and T2 weighted images
that usually make examinations long.
3) Measure real time changes in spin density at a time scale shorter
than T1. Example measure
real time changes in phosphorous metabolites or in
intracellular sodium in vivo in muscle or other
excitable tissue.
4) Measure changes in T1 at a time scale shorter than T1.
Musculoskeletal
1.
Applications of Parallel
Imaging in MSK MRI
2.
New coils for 3T and 7T:
phased array, small coils
3.
Kinematic and loaded imaging
of joints and spine
4.
Novel sequences to image
cartilage including SSFP and uTE
5.
Automated segmentation and
parameter mapping software (morphology, T1, T2, T1rho)
6.
Spectroscopy for MSK MRI -
muscle, spine, cartilage (1H, 31P, Na)
7.
Fat saturation for low field -
robust Dixon imaging
8.
New hardware: gradient inserts
and dedicated extremity 3T systems
9.
Fast T1 and T1rho mapping
sequences
10.
DWI and DTI imaging for
muscle and nerves
11.
Marrow Imaging
White Matter
1.
How to distinguish between
demyelination, inflammation and axonal loss?
2.
Early diagnosis of Alzheimers
(before occurrence of atrophy)
3.
Increased specificity for
diagnosis of Multiple Sclerosis in patient with WM lesions
4.
Possibility to establish
glioma grading with high confidelity
5.
Expand the MRI capabilities
for brain white matter to high resolution imaging of the spine columns
6.
Diagnose White Matter
Pathology Definitively using MRI.
MR Flow &
Motion Quantitation
1. How to achieve robust, accurate,
high-temporal-and-spatial-resolution flow measurements in,
for example, the right and circumflex coronary arteries,
which move a lot.
2. We need a well-defined, complex flow
phantom for comparison/calibration of scanners.
3. How to have first-time, every-time
measurements of flow with likely errors less than 10%
in PATIENTS in vessels
down to 5mm diameter?
4. What consistutes a clinical report of
an MR flow study? an MR cardiac motion study?
5. When will MR velocimetry match
ultrasound?
6. Spiral, EPI, segmented gradient echo,
FVI, etc, etc, etc, do we have the right tools for
every situation? and do we really need them all in clinic and
in research settings?
7. Limits of temporal, spatial and
velocity resolution - how low and how high can we go
(in flow and
tagging)?
8. How well does phase mapping work with
accelerated imaging techniques?
9. How do I know if a flow study was done
well?
10. 4D velocity mapping - how fast? how
good?
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