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Enabling Clinical 3T—MAGNETOM Trio Powered by Tim
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Enabling Clinical 3T—MAGNETOM Trio Powered by Tim
Milind D. Dhamankar, MD; Christopher Boyea, MBA, RT (R)(MR);
Abraham Padua, RT (R)(MR); Siemens Medical Solutions USA, Inc.
Introduction
“Tim proves it” is a message from Siemens and Siemens
users alike, as Tim systems have been shipping since
2003. However, 2005 saw Tim capabilities first
introduced to Ultra High Field at ISMRM in Miami.
The value provided at 3T has created a significant
amount of awareness within the world of Ultra High
Field users as well as clinical users currently operating
high field equipment. Consistently the question is
asked, “is 3T ready for prime time?”
Extended Coverage—Realized Clinical Benefit
Tim allows flexible coil combinations and extended
FoV imaging; after all, pathology doesn’t always end
at the edges of a coil. The elimination of the need to
reposition patients or coils allows greater flexibility
for extended coverage or multiple studies, providing
immeasurable benefits when imaging critically ill
patients. With the ability to leave the Spine Matrix
coil on the table at all times, Tim enables improved
patient workflow, efficiently enhancing patient
care. The following case is just one illustration of
the impact that extended coverage without patient
and coil repositioning has on the daily clinical routine
and results in improvement of care.
A 37-year-old male with medulloblastoma presents for
MR follow-up post-surgical treatment (see Figure 1).
To provide excellent quality of care it is important to
know the exact level and extent of spread of metastatic
disease for post-operative radiation therapy. In order
to look for skip metastases, a brain and whole spine
examination was performed in 20 minutes. This
extended exam was performed in this short duration
because of a combination of capabilities made possible
by Tim technology including the employment of
GRAPPA (made possible by Matrix coils) and the
elimination of the need to repositioning the patient
or coils. The examination showed a fourth ventricular
mass with high vertex metastases (normally missed
by CT due to partial volume effect if not careful),
enhancement in the brain
and several leptomeningeal
metastases down at the
T12-L1 levels. Spine
composing software
stitches the anatomy
seamlessly for referring
clinicians to better
understand the clinical
picture and plan therapy.
It is also particularly
helpful for the
neuroradiologist to ensure
each level is completely
covered, to verify each
of the levels carefully on
a composed whole spine
image and to confirm
the level of the pathology.
Essentials to delivering this
quality examination in the
short duration include
large homogenous FoVs,
use of GRAPPA, and
reduced patient set up
and transition between
anatomical coverage.
3T + GRAPPA Allows Orthopedic Imaging to Excel
MAGNETOM Trio with Tim is the first 3T system
to support parallel imaging for the spine, wrist,
and peripheral angiography. The flexibility of Tim
technology allows the implementation of parallel
imaging in almost any clinical application. This
flexibility directly translates to faster scans, increased
patient throughput and/or higher resolution, better
image quality, improved patient comfort due to
shorter acquisition times, 3D isotropic acquisitions
acquired in just a few minutes, and much more.
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Figure 1: Courtesy
NYU Medical Center.
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Notes
Figure 22: This 3D VIBE example was acquired post contrast 36 slices
in 19:52 seconds with a PAT factor of 2, and FoV 350mm and 5mm
effective thickness. Courtesy Siker Medical Imaging, USA.
Figure 21: Large FoV RF-Fat saturation VIBE breathhold acquired with
Body Matrix coils. Courtesy UCLA.
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aggressive resolution acquisition, with a 1.7mm
slice and a 14cm FoV, where 18cm may by typical
on other scanners and field strengths. The selection
of the 3D SPACE sequence, a variable flip angle 3D
Turbo Spin Echo, permits isotropic acquisitions in T1,
T2, or proton density weighting. This proton density
with fat-saturation was acquired with isotropic
resolution and employed an iPAT factor of 2.
The red and green lines on the images in Figure 5,
through the femoral neck, provide the axis for
surgical evaluation. In this clinical case the surgical
evaluation through radial MPR provided depiction
of a labral tear that otherwise may have been
difficult to visualize.
SWI—Susceptibility Weighted Imaging
SWI, a technique unique to Siemens, reveals blood
products and venous structures with greater clarity
than methods currently available, thanks to superior
sensitivity to deoxyhemoglobin and other blood
products. The SWI example shown in Figure 6
demonstrates the advantage of this new capability
compared to conventional T2* imaging methods.
A 52-year-old male trauma patient was imaged
with the conventional T2* image on the right
and the SWI method on the left. Improved
visualization of the hemorrhagic condition resulted
from the SWI acquisition.
BLADE
Motion correction is an important implementation
across field strengths, and the robustness of the
motion corrections available on Siemens products
are beyond any other systems available today.
With 1D PACE, 2D PACE, 3D PACE and 3D ART
(both for fMRI), and now BLADE, clinical studies
can be achieved with the most difficult patients.
The implementation of BLADE allows for correction
in any of the acquired orientations. The scenario
illustrated in Figure 7 is of a 34-year-old,
post-operative patient, presented to MR from
ICU for tumor evaluation. This case presented
a challenge for routine T2 imaging as demonstrated
in the image on the left. The implementation
of BLADE, with an acquisition time of less than
3 minutes, provided a motion-free 26 slice, T2 FSE,
acquired in the sagittal plane. The value of this
method is clearly demonstrated in this example.
Optimizing T1 Contrast at 3T
Throughout years of optimization, T1 Dark Fluid has
been found to have significant advantages in the
suppression of CSF for spinal applications. At higher
field strengths the T1 Dark Fluid over T1 Spin Echo
and Turbo Spin Echo methods have demonstrated
improvement in visualization of the cord, and in
post-contrast studies improved visualization of
metastatic disease and other subtle enhancements
(see Figure 8).
The comparison image of a
2-year-old pediatric spine
demonstrates the differences
in contrast of T1 Spin Echo
and T1 Dark Fluid at 3.0T
(see Figure 9). This example
demonstrates the conus and
the cauda equina, neither of
Figure 6: An example of Susceptibility Weighted Imaging.
Courtesy Duke University.
Figure 7: An example of the implementation of BLADE.
Courtesy Duke University.
Figure 8: Optimizing T1 Contrast at 3T.
The 4mm thick T1 Dark Fluid image
acquired at a 512 matrix, interpolated
to 1024. Courtesy Duke University.
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Optimizing Parameters for IAC Imaging
The selection of a 3D TSE sequence with a Restore
pulse minimizes pulsatility artifacts, and provides
the desired heavy T2 weighting for visualization
of intracranial nerves. The 12-channel Head Matrix
coil coupled with the signal provided by the field
strength of 3T permitted a 0.8mm slice thickness,
with an acquired 14cm FoV (see Figure 13).
An iPAT factor of 2 was used on the 3D TSE
sequence enabling nearly 40mm of coverage
in less than 5 minutes.
Matrix Spectroscopy
Another innovative Siemens technology currently
not available on other systems is Matrix Spectroscopy.
The SNR of 3T coupled with Matrix Spectroscopy
(using a 12-channel Head Matrix coil), provides
improved spectral quality with respect to SNR
and resolution compared to other methods.
Figure 14 shows a 16 x 16 matrix that was acquired
using a weighted acquisition method; an automated
combination of weighted and phase-corrected
signals from the twelve individual coil elements
provides a significantly reduced acquisition time
of 7:34 minutes (see Figures 14–15).
MAGNETOM Trio with Tim
With the introduction of Tim technology on the
MAGNETOM Trio, there are now up to 102 seamlessly
integrated Matrix coil elements and up to 32 RF
channels. Flexible combination of the ultra light
weight Tim Matrix coil elements encourages creativity
in building an anatomically- and patient-customized
coil. This reduces the need for a large number of
dedicated coils and at the same time covers
different applications.
Clinical Challenge: Brachial Plexus Imaging
In this case, acquired at NYU Medical Center,
a surface coil for Brachial Plexus imaging was
created by utilizing the Neck Matrix, Spine
Matrix, and a Body Matrix coil (see Figure 16).
The signal delivered as a result of this creative
coil combination provided a resolution opportunity
that was maximized through a 512 squared matrix,
interpolated to 1024, 2mm thickness, and a FoV
of 20cm. Sequence duration was 3 minutes for
this coronal T2 FSE.
Figure 14: A 16 x 16 matrix acquired using a weighted acquisition
method. Courtesy University of Tubingen.
Figure 15:
The Cho/Cr-map shows
the active tumor region
of this left temporal
Glioblastoma. Courtesy
University of Tubingen.
Figure 13: Optimizing Parameters for IAC Imaging.
Courtesy Duke University.
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Figure 16:
Combining the
Neck, Spine,
and Body Matrix
coil provides
opportunity for
optimal Brachial
Plexus imaging.
Courtesy NYU
Medical Center.
Figure 17:
Off-center fatsat
shoulder—2D TSE
fatsat with PAT 2,
3mm slices,
140mm FoV, TA
2:15 minutes,
Shoulder coil.
Courtesy
Siker Medical
Imaging, USA.
Magnet
One of the essential ingredients to building
a system that meets both research and clinical
needs at 3T is homogeneity. The Siemens 3T
magnet offers 1 ppm VRMS at 50cm DSV which
is 3 times better then any other product offering.
A three-fold improvement in homogeneity directly
impacts the quality of spectroscopy, fMRI, EPI and
chemical-shift fat suppression. MAGNETOM Trio
with Tim is the only system that offers 50cm FoV
in one acquisition, essential for coronal and sagittal
spine imaging, MR colonography and head-to-neck
four vessel ce-MRA just to name a few.
The offset FoV RF fatsat coronal in Figure 17
implemented GRAPPA, with an acceleration of 2,
resulted in an acquisition time of just greater than
two minutes.
Gradients
Gradients are commonly referenced as the horse
power of the MR system. As a leader in the design
of gradient coils and amplifiers, Siemens designed
the TQ-engine (45mT/m @ 200mT/m/ms per axis at
full 50 x 50 x 50cm FoV), providing state-of-the art
gradient power, unsurpassed linearity and the least
possible eddy currents. All of this technology does not
lose sight of practicality; there is still the advantage of
being able to utilize the full slew rate across
any FoV and through Siemens unique technology
delivering Audio Comfort with a 90% reduction
in acoustic noise, without performance trade-off,
compared to conventional 3T systems.
High-grade Stenosis in the Right Carotid
Artery Right After the Bifurcation
Implementation of GRAPPA with iPAT 4 enables an
acquired 576 matrix, resulting in a 0.7mm isotropic
voxel in only 20 seconds (see Figure 19). These
acquisition parameters enable the ability to magnify
to the carotid bifurcation and the circle of willis for
further evaluation without the loss of detail. This
provides an excellent stroke evaluation protocol all
in one sequence (see Figure 18).
Figure 18:
Head and Neck
Matrix coil
combination
providing
extended
coverage for
this iPAT factor
4 carotid study
demonstrating
high grade
stenosis.
Courtesy UCLA.
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which are visualized clearly on the TSE T1 Spin Echo.
The SNR of the 24-element Spine Matrix coil allowed
resolution optimization of a 3mm thick slice at a
20cm FoV.
Siemens is the only vendor that provides a dedicated
coil for cervical spine imaging. The Neck Matrix coil
eliminates the need for users to make the tradeoff
of coverage for optimized signal. By employing the
3D VIBE sequence with the Neck Matrix coil, the full
signal potential of 3T can be harnessed enabling the
pursuit of higher resolution than what is achievable
at lower field strengths.
This axial 3D T1 VIBE was acquired at 2.0mm and
a 13 FoV (see Figure 10). The 256 acquired matrix,
resulting in a submillimeter pixel resolution of
0.6mm, was further improved in visual resolution
by employing a reconstruction matrix of 512.
The nerve roots coming off of the cord provide
visualization through the foramina and improve
the conspicuity for potential visualization of MS
lesions within the spinal cord.
Optimization of T1 contrast at 3T includes
employment of 2D FLASH-based sequences as a
result of the ability to achieve shorter TE’s and TR’s.
Compared to Spin Echo methods that at 1.5T may
have employed flow compensation and pushed TE’s
slightly higher, trading off flow compensation for the
Figure 9: Optimizing T1 Contrast at 3T. Comparison
image of a 2-year-old pediatric spine. Courtesy
Duke University.
Figure 11: Post contrast T1 weighted
2D FLASH. Acquired in 2:39 minutes.
Courtesy Duke University.
Figure 10: Optimizing T1 Contrast at 3T. Axial 3D
T1 VIBE. Courtesy Scott and White Hospital.
shorter TE’s offered by FLASH have been found to
significantly minimize pulsatility artifacts while the
reduced flip angle and short TR provide improved
grey white matter delineation. In the 2D FLASH
sequence shown in Figure 11, a TE of 2.6ms and TR
of 380 provide the desired contrast, while the signal
of 3T afforded a 3mm slice thickness, acquired in
2:39 minutes.
Figure 12: Large FoV, with a 1024 reconstruction matrix with Dark Fluid
for cord visualization. Courtesy NYU Medical Center.
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Figure 19: iPAT factor of 4 for this 112 slice 576 matrix and submillimeter slice thickness was acquired in 20 seconds. Courtesy UCLA.
Faster rise times are used to reduce echo times
and shorten inter-echo spacing to decrease the
dephasing associated with susceptibility-induced
field variations. Higher gradient strengths allow
thinner slices that help improve diagnostic
capability due to higher resolution. When high
gradient strength is coupled with Parallel Acquisition
Techniques (PAT), extreme speed for shorter
breathhold exams or higher resolution in the
same acquisition time becomes possible. Increased
coverage via more slices in both 2D and 3D imaging
with reduced acquisition times improve the diagnostic
confidence of breathhold imaging methods as a
result of increased patient acceptance.
The excellent linearity for a 50cm FoV (1.7% VRMS)
enables powerful advanced applications like EPI,
ce-MRA and cardiac to image with large FoVs.
Conclusion
For prospective MRI buyers, the MAGNETOM Trio
with Tim makes a well-calculated choice, particularly
if a 1.5T MRI is already present.
Siemens takes pride in its leadership in MRI and
continually delivers unsurpassed innovations.
With increased performance by means of a greater
application range, with higher throughput by
means of increased procedure volumes and
with better differentiation by means of satisfying
increasing clinical demands in the tough competitive
environment, the MAGNETOM Trio with Tim has
moved 3T from research to clinical. The MAGNETOM
Family heritage, including syngo MR, Inline technology,
Phoenix and iPAT, contribute to the distinct
advantages of the MAGNETOM Trio with Tim.
Figure 20: High temporal resolution enabled by
GRAPPA factor of 4. Courtesy UCLA.
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The Proton Density Turbo Spin Echo image shown
in Figure 4, demonstrating an anterior miniscal tear,
was acquired with a 1.7mm slice thickness and a
512 matrix in only 2:31 minutes as a result of the
implementation of GRAPPA.
Body Matrix Coils and iPAT Deliver
Improved Isotropic Imaging
The Body Matrix coil may be used for a number of
examinations beyond routine cardiac and body
applications. The coil may be combined with the Spine
Matrix and Neck Matrix coil for improved upper torso
and contrast enhanced imaging, or wrapped around
an anatomy in the case of a unilateral hip. Resolution
and acquisition time can be optimized further with the
employment of GRAPPA, which by the nature of the
method does not require opposed coil elements, as is
the case for image-based parallel imaging.
In this example of unilateral hip imaging, a 6-element
Body Matrix coil was wrapped around the patient’s
anatomy (see Figure 5). The signal of 3T permitted an
By offering both image-based (mSENSE) and raw
data-based (GRAPPA) parallel imaging methods,
users are able to employ the benefits offered
by parallel imaging in a greater number of
clinical situations.
The Siemens exclusive GRAPPA is found beneficial
in small FoV imaging. The orthopedic imaging
example in Figure 2 demonstrates the everyday
value acceleration capabilities can deliver in routine
clinical imaging.
GRAPPA allows parallel imaging to be employed in
smaller anatomies without the artifacts associated
with SENSE-based techniques. Both images were
acquired with identical resolution parameters
including a 6cm FoV, 2mm slice thickness, and a 320
matrix (interpolated to 640). The resultant resolution
based on acquisition resolution is 2 microns.
Acquisition time of the left image was 7:07 minutes;
however, employing GRAPPA with an acceleration
factor of 3 resulted in greater than a 50% reduction
in scan time at 2:57 minutes.
2
Figure 5: Isotropic unilateral hip imaging with iPAT factor of 2. Courtesy Duke University.
Figure 2: 6cm FoV wrist, at 2 micron resolution, left image 7:07 minutes,
with GRAPPA right image 2:57 minutes. Courtesy NYU Medical Center.
Figure 3: 5cm FoV finger acquired with
a 1mm slice thickness, demonstrating
the signal benefits of 3T. Courtesy
3T Imaging of Morton Grove.
Figure 4: GRAPPA enabled 51 slices
in 2:31 minutes. Courtesy 3T Imaging
of Morton Grove.
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On account of certain regional limitations of sales
rights and service availability, we cannot guarantee
that all products included in this brochure are
available through the Siemens sales organization
worldwide. Availability and packaging may vary
by country and is subject to change without prior
notice. Some/All of the features and products
described herein may not be available in the
United States.
The information in this document contains general
technical descriptions of specifications and options
as well as standard and optional features which do
not always have to be present in individual cases.
Siemens reserves the right to modify the design,
packaging, specifications and options described
herein without prior notice. Please contact your local
Siemens sales representative for the most current
information.
Note: Any technical data contained in this document
may vary within defined tolerances. Original images
always lose a certain amount of detail when
reproduced.
Siemens Medical Solutions USA, Inc.
Magnetic Resonance Division
51 Valley Stream Parkway
Malvern, PA 19355-1406 USA
Telephone: 1-888-826-9702
www.usa.siemens.com/medical
© 2006 Siemens Medical Solutions
Order No. A9119-6391-1C-4A00
Printed in USA
Siemens Medical
Solutions that help
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