Takashige Yoshida1,2, Yuki Furukawa1, Hiroaki Tsuchiya1, Kohei Yuda1, Masami Yoneyama3, Nobuo Kawauchi1, and Haruo Saito4
1radiology, Tokyo metropolitan police hospital, Tokyo, Japan, 2Graduate school of Medicine, Tohoku university, Miyagi, Japan, 3Marketing, Philips Electronics Japan, Tokyo, Japan, 4Division of Diagnostic Image Analysis, Graduate school of Medicine, Tohoku University, Miyagi, Japan
Synopsis
A extend of slice direction
and high resolution imaging cannot help to increase scan time in hepatic MRI. The
hepatic MRI is necessary to hold their breath, and breath holding influenced on
image quality. Hence improved image quality on hepatic MRI is a required free
breath sequence. Our study using 3D stack-of-stars trajectory with respiratory
navigator is objective that perfectly eliminate respiratory motion effect. A
sequence combined motion averaging by stack-of-stars and correction by navigator
is possible to eliminate respiratory motion.Purpose
Recently, free-breathing
radial 3D T1W-GRE sequence without compensation by respiratory gating was
performed during free breathing for Gd-EOB imaging of the liver with comparable
image quality to BH. However, the sequence with compensation by respiratory gating
has not yet been investigated.
This study aimed to evaluate the independent breathing
motion sequence using respiratory-gated kx-ky radial trajectory T1 high-resolution
isotropic volume excitation (THRIVE-GXR) sequence in abdominal MRI and compare with
gated enhanced-THRIVE (Ge-THRIVE) and gated ky-kz radial trajectory e-THRIVE (GXe-THRIVE) (Fig1).
Methods
Using our
institutional review board-approved procedures, 20 subjects were imaged using a
1.5-T Philips MR system and 32-channel torso-cardiac coil. All sequences were set
transverse using a navigator echo with
the following parameters: 3D T1-TFE, FOV x*y (mm) = 300*300, matrix x*y = 188*188,
number of slices = 150, thickness/gap (mm) = 3.0/−1.5, TFE factor = 18, flip
angle degree = 12, water–fat shift = 0.3, and respiratory gating = navigator
gate and tracking. In Ge-/GXe-THRIVE, the parameters were set as follows: TR/TE
= 3.1/1.49, SENSE = 2, fat sat = SPAIR (TI = 48 ms), and scan time (s) = 58/46.
In THRIVE-GXR, the parameters were set as follows: TR/TE = 3.9/1.6, density of
angle (degree) = 120, fat sat = SPIR, and scan time (s) = 127. The obtained image was measured using signal
intensity (SI) and standard deviation (SD) of the liver,[Editor1] and the coefficient
of variation (CV) was calculated using SI and SD. Overall image quality
(artifact and homogeneity) was evaluated on a 5-point scale (with “5” indicating
excellent quality and “1” indicating poor quality) by two blinded reviewers.
Results
CV of THRIVE-GXR sequence was
significantly lower than that for other sequences (P < 0.001). Image
quality of artifact was better for THRIVE-GXR
sequence than for any other sequence (P < 0.001); however,
homogeneity was not significantly different (Fig2).
Discussion
The Ge-THRIVE decreased respiratory
motion effect by respiratory gating. Radial
trajectory of GXe-THRIVE had only an
average effect on in-plain respiratory motion
effect. Ge- and GXe-THRIVE are not completely able to
eliminate the respiratory motion effect.
THRIVE-XR by 3D
stack-of-stars sequence adopts radial trajectory, which decreases the in-plane respiratory
motion effect. The main reason is that the central part of k-space is
oversampled in the radial trajectory, i.e., motion artifact is frequently
balanced by filling up the data subsets. Furthermore, the combination of
respiratory gating can decrease through plane respiratory motion. Therefore,
THRIVE-GXR can be used to reduce respiratory motion artifact and to improve its
quality (Fig3).
Conclusion
It is possible to provide
motionless hepatic image using
THRIVE-GXR of respiratory-gated 3D
stack-of-stars sequence.
Acknowledgements
No acknowledgement found.References
1. Maki Jeffrey H, Thomas L
Chenevert, Martin R Prince. The effects of incomplete breath-holding on 3D MR
Image Quality. Journal of Magnetic Resonance
Imaging 1997;7(6): 1132-1139.
2. Young P M, Brau A C, Iwadate Y, et al. Respiratory navigated free breathing 3D spoiled gradient-recalled echo sequence for contrast-enhanced examination of the liver: diagnostic utility and comparison with free breathing and breath-hold conventional examinations. American Journal of Roentgenology 2010;195(3): 687-691.
3. Azevedo R M, de Campos R O, Ramalho M, et al. Free-breathing 3D T1-weighted gradient-echo sequence with radial data sampling in abdominal MRI: preliminary observations. American Journal of Roentgenology 2011;197(3):650-657.
4. Shankaranarayanan A, Wendt M, Lewin J S, et al. Two-step navigatorless correction algorithm for radial k-space MRI acquisitions. Magnetic resonance in medicine 200;45(2): 277-288.