Robust free-breathing hepatic MRI using respiratory-gated 3D stack-of-stars sequence
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


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.


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).


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.


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).


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).


It is possible to provide motionless hepatic image using THRIVE-GXR of respiratory-gated 3D stack-of-stars sequence.


No acknowledgement found.


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.


Fig1. k-space trajectory of (a) e-THRIVE, (b) Xe-THRIVE and (c) THRIVE-XR. (a) Cartesian k-space trajectory with linear ordering with 2 directions (ky, kz) half scan technique. (b) Radial(ky-kz) and (c) radial(kx-ky) k-space trajectory with linear ordering. Radial trajectory is overlap each data on center of k-space.

Fig2. This radar chart shows various sequences performance with artifact and homogeneity. The artifact of THRIVE-GXR grade higher than other sequence (P=0.056), but homogeneity was equally effective in all (no significant difference).

Fig3. Volunteer hepatic images. Left-upper is Ge-THRIVE, right-upper is Gxe-THRIVE and left-lower is THRIVE-GXR. THRIVE-GXR could visualize motionless hepatic image.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)