Yuli HUANG1, Li ZHU2, Haiyang DONG2, Yuan QU3, and Yan WANG3
1MR, Philips Healthcare (Suzhou) Co., Ltd, SUZHOU, China, 2Radiology, Shanghai Chest Hospital, Shanghai JiaoTong University, Shanghai, China, 3Radiology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China
Synopsis
4D Flow MRI is a technique that can characterize vascular structure and
hemodynamics. Compared with SENSE, Compressed SENSE can further reduce scanning
time using the sparse characteristics of MR images. This study aims to
investigate the feasibility of 4D Flow MRI with Compressed SENSE by comparing
with 4D Flow MRI with SENSE. 4D Flow dynamic angiography of hepatic portal vein
using SENSE and Compressed SENSE could be completed within 5 minutes with
optimized parameters. The scanning time of Compressed SENSE 4D Flow was shorter
than that of SENSE 4D Flow.
INTRODUCTION
Portal hypertension is a common clinical prognosis of cirrhosis, which
often leads to blood disorders, collateral circulation, and in severe cases
portal vein blood flows away from the liver.1,2 4D Flow MRI is a magnetic
resonance (MR) imaging technique which can characterize vascular structure and
hemodynamics.3,4 However, long scanning time with 4D Flow scan
limited its clinical application. Recently, Compressed SENSE (CS) has been
validated as an efficient acceleration technique in fast MR imaging compared
with SENSE.5 This study aims to investigate the possibility of 4D
Flow MRI with CS by comparing with 4D Flow MRI with SENSE.METOHDS
Study
sample: Ten female and twelve male healthy controls (mean age, 38.2 ± 13.2 years) without any contraindication to MR scanning
underwent abdominal MR imaging after fasting. All the parts of this study were
approved by local institutional review board and written consent form was
obtained from each subject. MR
imaging: Abdominal MR imaging was performed on a 1.5 Tesla MR scanner (Achieva,
Philips Healthcare) with an 8-channel abdominal coil and a 12-channel spine
coil. Firstly, a 2D balanced FFE (bFFE) scan was performed with breath-hold to determine
the correct orientation of oblique section parallel to portal vein. Secondly,
maximum flow velocity in portal vein was measured by QFLOW was set as the input
of velocity encoding. Finally, 4D Flow MR imaging with SENSE and CS using ECG
gating was performed with the following parameters: 3D fast field echo, number
of excitations 3, repetition time 4.9 ms, echo time 3.5 ms, flip angle 10°, field
of view 320 × 320 mm2, slice number 36, slice thickness 3 mm, voxel
size = 3 × 3 × 3 mm3. The accelerator factor was 2 × 1.8 in
acquisition with SENSE and 4 with CS. Fifteen phases were acquired in a cardiac
circle. Data Analysis: Abdominal
4D Flow images were reviewed by two radiologists with >10 years’ experience
blinded to each other. Each reviewer drew five regions of interest (ROIs)
>50 mm2 in main portal vein (MPV), superior mesenteric vein (SMV),
splenic vein (SV), left and right portal vein (LPV, RPV), respectively. Signal-to-noise
ratio (SNR) was calculated in MPV, SMV, SV, LPV and RPV with the following
equation:
SNR=Svessel/SD(Snoise)
where Svessel
represented mean value of signal in PV and its branches. The maximum flow velocity
and flow volume were calculated in MPV, SMV, SV, LPV, and RPV using GTFlow
(Zurich, Switzerland). Additionally, 4D Flow reconstructed streamline images
were assessed by two reviewers according to a 1 to 4 rating principle which was
used to evaluate the image quality (Figure 1). The scanning time of 4D Flow
with SENSE and CS was recorded separately. Statistical
Analysis: The SNR was compared between the ROIs in 4D Flow images
acquired with SENSE and CS using a paired t
test. The difference between the image quality of the reconstructed streamline
was compared using a rank sum test. A p<0.05 was considered as statistically
significantly and all statistical analyses were conducted with SPSS 25.0 (IBM
Inc., USA).RESULTS
There was no significant difference in SNR between the ROIs in the
images acquired with SENSE and CS (P>0.05). No significant difference was
found in maximum flow velocity and flow volume of SV, SMV, MPV, LPV and RPV
(All P>0.05). Additionally, the image quality of streamline of SV, SMV, MPV,
LPV and RPV was similar (Figure 2) and no statistically significant difference
was found in image quality score (P>0.05) (Table 1). The score of image
quality was consistent between the two physicians (kappa = 0.89). There was a
significant difference in scanning time between 4D flow with SENSE and CS (293.70
± 31.63s vs. 271.45 ± 39.64s, p <0.05).DISCUSSION
In the present study, 4D Flow with CS acceleration
could shorten scanning time without loss of SNR in portal vein MR imaging
compared to that with SENSE acceleration. 4D Flow dynamic angiography of
hepatic portal vein using SENSE and CS could be completed successfully within 5
minutes with optimized parameters.6 After good preparation of
abrosia and water deprivation before examination, 4D Flow scanning combined
with diaphragm navigation and abdominal wall navigation technology could
minimize the impact of respiratory movement on image acquisition. The image
quality and reconstructed streamline tracking of the two methods were similar.7CONCLUSION
Fast 4D Flow imaging with SENSE and CS exhibited similar SNR and image
quality in portal vein imaging, but acquisition with CS might be a more
potential acceleration method in 4D Flow due to its shorter time consumption.Acknowledgements
No acknowledgement found.References
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