Yasunari Fujinaga1, Akira Yamada1, Ayumi Ohya1, Hirokazu Tokoro1, Takeshi Suzuki1, Hayato Hayashihara2, Aya Shiobara2, Yasuo Adachi2, Yoshihiro Kitou2, Marcel Dominik Nickel3, Terumasa Takemaru4, Hirokazu Kawaguchi5, and Katsuya Maruyama5
1Department of Radiology, Shinshu University, School of Medicine, Matsumoto, Japan, 2Radiology Division, Shinshu University Hospital, Matsumoto, Japan, 3MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany, 4Department of Application, Siemens Healthcare K. K., Tokyo, Japan, 5Diagnostic Imaging Business Area, DI Research & Collaboration Dpt., Siemens Healthcare K. K., Tokyo, Japan
Synopsis
We aimed to evaluate the
differences of the DCE-MR images between radial VIBE with k-space weighted
image contrast reconstruction (r-VIBE-KWIC) and Golden-angle RAdial Sparse
Parallel (GRASP). DCE-MRI using r-VIBE-KWIC and GRASP was performed in 36 and
35 patients, respectively. The most optimal arterial phase image was selected
from eight sub-frame images at arterial phase, and factors of image quality in the both
two groups were assessed using five-point scales. In GRASP, the median scores
for all factors except for one were significantly higher than those in
r-VIBE-KWIC. In conclusion, GRASP provided the better DCE-MR images than
r-VIBE-KWIC.
INTRODUCTION
High-spatial and -temporal resolution dynamic
contrast-enhanced MRI (DCE-MRI) of the liver using the radial volumetric
interpolated breath-hold examination with k-space weighted image contrast
reconstruction (r-VIBE-KWIC) has advantages such as optimal scan timing, less
motion artifact, detailed hemodynamic evaluation of lesions1,2.
Recently, compressed sensing Golden-angle RAdial Sparse Parallel (GRASP), which
is a golden-angle radial acquisition combined with compressed sensing reconstruction
technique, has been available for DCE-MRI of the liver3,4. In
this study, we aimed to evaluate the differences of the DCE-MR images between r-VIBE-KWIC
and GRASP.
MATERIALS AND METHODS
This study was a prospective observation study, and
the study design was approved our institutional review board. Written informed
consent was obtained from all participating patients before MRI examinations.
Consecutive seventy-one patients who underwent breath-holding dynamic
contrast-enhanced MRI (DCE-MRI) of the liver at two kinds of 3-tesla MR units were enrolled
in this study. Thirty-six patients (24 men and 12 women; mean age 65.6 years
old) were performed DCE-MRI using r-VIBE-KWIC between January 2018 and march
2018 (r-VIBE-KWIC group). Thirty-five patients (21 men and 14 women; mean age
64.3 years old) were performed DCE-MRI using GRASP between April 2018 and July
2018 (GRASP group). Scan parameters of the two sequences were shown in table 1.
Standard dose of Gd-EOB-DTPA (0.025 mmol/kg body weight) were used in all
patients. The contrast agent was injected from the cubital vein at the rate of
2 mL/s followed by 50 mL of 0.9% saline at the same rate. Arterial phase images
were obtained 22 s after the injection started. Of the eight sub-frame of the
arterial phase images, the most optimal arterial phase image was selected and factors
of image quality were assessed using five-point scales as follows:
visualization of the right and left hepatic arteries (5, excellent, diagnostic;
4, good, diagnostic; 3, fair, diagnostic; 2, poor, non-diagnostic; 1,
non-detectable, non-diagnostic), degree of the artifact at right lobe, left
lobe and caudate lobe based on the visualization of intrahepatic vessels and
the homogeneity of the hepatic parenchyma (5, no artifact, diagnostic; 4,
faint, diagnostic; 3, moderate, diagnostic; 2, intermediate, non-diagnostic; 1,
strong, non-diagnostic), and overall image quality (5, excellent, diagnostic;
4, good, diagnostic; 3, fair, diagnostic; 2, poor, non-diagnostic; 1, very
poor, non-diagnostic). The scores of the two groups were compared using
Mann-Whitney U test. In each group, the score of each lobe was compared using
Kruskal-Wallis test and Dunn’s multiple comparison test.
RESULTS
The median scores of overall, right hepatic artery,
left hepatic artery, artifact at right lobe, left lobe and caudate lobe in
r-VIBE-KWIC/GRASP were 3/4, 2/4, 2/4, 3/4, 3.5/4 and 3/3, respectively. For all
factors except for artifact at caudate lobe, the scores in the GRASP group were significantly higher than those in
r-VIBE-KWIC group (Figure 1, 2). Regarding artifact, the score for the caudate
was significantly lower than other groups in each group (Figure 3). A
representative case was shown in Figure 4.
DISCUSSION
There is no report analyzing image quality
of breath-holding DCE-MRI using GRASP because GRASP has been used for
free-breathing DCE-MRI. In this sense, optimization of the breath-holding GRASP
was challenging. Regarding GRASP, number of spokes used for one sub-frame
images was 21. In this study, hepatic arteries were clearly seen in GRASP than in
r-VIBE-KWIC. Because the acceleration factor was 21.5, the sub-frame image had
the image quality equivalent to the image with 451.5 (21 x 21.5) spokes, that
was more than r-VIBE-KWIC (198–208 spokes). In addition, GRASP allowed smaller the
voxel size (about 5.5 mm3) than that of r-VIBE-KWIC (about 15.3 mm3)
even though breath-holding time was similar in both r-VIBE-KWIC and GRASP. The
advantage of the GRASP in the parameter setting might be the reason for the
better visualization of the hepatic arteries. This result may indicate GRASP
has a potential to demonstrate detailed structures of the normal anatomy and
the lesions.
Artifact in GRASP was equal or weaker than that in
r-VIBE-KWIC. We attributed the reason to artifact reduction by iterative
reconstruction. However, artifact at the caudate lobe was worse than that at
other lobes in both r-VIBE-KWIC and GRASP. The reason was unclear but it may be
a disadvantage of radial sequences.
CONCLUSION
Better visualization of the hepatic arteries and
less artifact of the hepatic parenchyma were provided in GRASP than in r-VIBE-KWIC.Acknowledgements
No acknowledgement found.References
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