Xiaoming Bi1, Zhaoyang Fan2, Yutaka Natsuaki1, Debiao Li2, and Gerhard Laub1
1Siemens Healthcare, Los Angeles, CA, United States, 2Cedars-Sinai Medical Center, Los Angeles, CA, United States
Synopsis
The recently developed
MATCH technique integrates multiple 3D image sets into a single measurement and
it is a promising method for carotid plaque characterization. One of the
remaining challenges is the gross motion of carotid arteries that originates
from pulsation, breathing and swallowing. In this work, a motion robust
stack-of-stars sampling trajectory was implemented into the MATCH sequence
(STAR-MATCH). Preliminary studies from volunteers and patient demonstrate it is
feasible to characterize carotid plaque using the STAR-MATCH sequence with
improve motion robustness.Purpose
2D Multi-contrast MR imaging has been well
established for the carotid plaque characterization [1-3]. Such method,
however, has limited slice resolution, spatial coverage, and potential
mis-registration between different images. The recently developed MATCH
technique integrates multiple 3D image sets into a single measurement [4]. Plaque
component-specific contrasts setting and intrinsic registration of multiple
images acquired with MATCH greatly simplify the workflow and image interpretation.
One of the remaining challenges for the MATCH technique is the gross motion of
carotid arteries (e.g. pulsation, breathing and swallowing) that compromises
the vessel wall delineation [5]. Stack-of-stars sampling scheme was recently
demonstrated to have excellent tolerance to carotid motion [6]. We hypothesize
that MATCH sequence benefits from integrating the stack-of-stars sampling trajectory
(i.e. STAR-MATCH). The current work investigates feasibility of using STAR-MATCH
sequence for carotid plaque characterization.
Methods
Figure 1 shows the schematic
diagram of the STAR-MATCH sequence. Following a non-selective inversion preparation,
three image sets are acquired at different TI time points using stack-of-stars
sampling trajectory. Readouts for image sets 1 and 3 are preceded by a DANTE preparation
[7] module for blood signal suppression. TI values and magnetization
preparations are optimized to delineate short-T1 hemorrhage, calcification, and
overall plaque morphology, respectively, in three image sets.
Three healthy subjects and one patient with
carotid plaque were scanned on a 3T MR scanner (MAGNETOM Prisma, Siemens Healthcare,
Erlangen, Germany). An eight-channel carotid coil (4 elements on each side) was
used as signal receiver in combination with a 20-channel head-neck coil. For
the comparison purpose, MATCH sequence using Cartesian sampling was also run on
same volunteers with identical protocol settings as with STAR-MATCH. Imaging
parameters included: FOV = 16 x 16 cm
2; 64 coronal partitions; acquisition
voxel = 0.83 x 0.83 x 0.83 mm
3; flip angle = 8°; 192 radial views (STAR-MATCH) or
phase-encoding lines (MATCH); TI1/TI2/TI3 = 370/1200/2650 ms; repetition time between
inversion pulse (IRTR) = 3000 ms. DANTE module (150 ms) was composed of 120
hard RF pulse (FA = 12°) with spoiler gradients
(20 mT/m, 0.9 ms duration) in between. For the patient scan, 3D TOF, 2D T1-weighted
and T2-weighted TSE images were also acquired. Parameters for TSE included: 5
axial slices; 0.51 x 0.51 x 3.00 mm
3 voxel size.
Results
Carotid artery images were
successfully acquired from all subjects. Figure 2 shows representative images
acquired from a healthy subject. Good quality images were acquired with three
desired tissue contrasts using both MATCH and STAR-MATCH sequences. Wrapping
artifacts in Cartesian acquisition were not present in STAR-MATCH images. MIP of
STAR-MATCH morphological image (image 3) showed improved carotid wall
delineation using STAR-MATCH. Figure 3 shows MPR images of patient scanned with
STAR-MATCH and conventional TOF, 2D TSE sequences. No intraplaque hemorrhage was
detected from the Hyper-T1 (image 2) STAR-MATCH images. As illustrated in
Figure 4, focal signal voids were detected in the gray-blood contrast (image 2)
presumably due to calcification of local vessel wall. Ulcerated plaque is
clearly visible in the sagittal MIP of 3rd STAR-MATCH image. Axial
MIPs of STAR-MATCH agree corresponding TSE and TOF images acquired from the
same slice location. Figure 5 illustrates sagittal MPRs of STAR-MATCH and TOF.
Fused TOF and STAR-MATCH image demonstrates excellent spatial registration
between these two images. Atheroma and surrounding blood can be clearly
differentiated. In comparison, 2D TSE shows poor slice resolution and spatial
coverage despite long imaging time (4.5 minutes for T1-TSE).
Discussion
Taking advantage of radial
sampling scheme, STAR-MATCH offers improved robustness to motion compared to
its Cartesian counterpart. This can be used to improve spatial coverage and/or
resolution despite slightly longer imaging time. Future work on combining
STAR-MATCH with MR acceleration technique (e.g. parallel imaging or other
advanced reconstruction) is warranted. Also its performance in patient needs to
be evaluated in a larger study population.
Conclusion
STAR-MATCH is a promising
3D technique for the characterization of carotid plaque in a single all-inclusive
measurement with improved carotid plaque motion robustness.
Acknowledgements
No acknowledgement found.References
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[2] Fayad ZA et al, Ann NY Acad Sci. 2000, p173.
[3] Saam T et al, Arterioscler Thromb Vasc Biol, 2005, p234.
[4] Fan Z et al, JCMR 2014, p53.
[5] Boussel L et al, JMRI 2006, p413.
[6] Bi X et al, ISMRM 2015, p555.
[7] Li L et al, MRM 2012, p1423