Li Jiang1, Chenguang Zhao1, Andy Jiang1, Ming Yang1, Wengu Su1, Allan Jin1, Ping Yang1, Stephon Xu1, and Feng Huang1
1Philips Healthcare (Suzhou), Suzhou, Jiangsu, China, People's Republic of
Synopsis
Liver black blood
imaging helps to detect and characterize focal liver lesions and thus is highly
desirable clinically. The commonly used low b-value DWI sequence is limited due
to inherent limitations of EPI, such as low spatial resolution and motion
artifacts including blurring and ghosting. We proposed a 3D whole liver black
blood imaging solution within 3 min. By combining with existing black blood
preparation, a respiratory triggered VISTA sequence and a free breathing
imaging technique utilizing GROWL reconstruction were proposed. Six healthy
volunteers with stable and irregular respiration were scanned to further validate
the feasibility of our proposed solution.Introduction
Liver black blood (BB) images contribute to improved detection and
characterization of focal liver lesions by suppressing vessel signals which show
similar signal intensity to malignant lesions, and thus are highly desirable in
clinical practice [1]. To achieve that, 2D low b-value DWI sequence is commonly
used. However, the current image quality is still limited due to inherent
limitations of EPI: poor SNR, low spatial resolution as well as blurring and
ghosting artifacts from motion [2]. In this study, we aim to provide a 3D whole
liver BB imaging solution which applies to patients with various respiration
states. Specifically, a) respiratory triggered VISTA sequence and b) free
breathing acquisition with GROWL reconstruction [3], which readily
combines with existing BB preparation techniques [4-6], were proposed and validated.
Methods
Respiratory triggered imaging VISTA (or SPACE), due to
its inherent black-blood effects and fast imaging speed, has been increasingly
applied in carotid and intracranial vessel wall imaging. However, it also
suffers from incomplete blood suppression for slower flows and flows not
parallel to its readout direction. To further attenuate signals from hepatic
and portal veins as well as to preserve more static tissue signals, we combined
the respiratory triggered VISTA sequence with an additional BB preparation.
Free breathing imaging BB prepared 3D stack
of stars golden angle radial was used for free breathing data acquisition. Images
were reconstructed using GROWL algorithm to enlarge the sampled k space region and
reduce streaking and blurring.
MR Experiment 6 healthy
volunteers were scanned on a Multiva 1.5T system (Philips Healthcare, Suzhou,
China) with the proposed and optimized respiratory triggering and free
breathing techniques. For respiratory triggered SPACE imaging: TR/TE
shortest/18 ms, flip angle 90°, TSE factor 100, resolution 1.4 mm isotropic,
SENSE factor P/S 2/1, scan time 2min 51s. Free breathing acquisition parameters
were: TR/TE 5.9/2.6, flip angle 15°, voxel size 1.6x1.6x2.5 mm3, bandwidth
304 Hz/pixel, spokes per slice 560, scan time 2min 57s.
Image Analysis Contrast
to noise ratio (CNR) of the portal veins vs right
anterior tissue was determined and compared for both techniques
to validate the image quality of liver peripheral regions. All the images were
evaluated in consensus by 2 radiologists.
Results
In both of the proposed respiratory triggered
and free breathing imaging techniques, image contrasts of the peripheral liver
regions were improved after applying BB preparation (Fig.1). Two of the six volunteers showed an unstable
breathing behavior during scanning, and motion related blurring was observed in
the respiratory triggered images, while the free breathing images were much less
affected (Fig. 2). CNRs were greatly
decreased for the respiratory triggered technique in cases of irregular
breathing, compared to that of free breathing technique (Fig. 3).
Discussion and
Conclusion
In this work, we proposed a within 3 min 3D
whole liver black blood imaging solution including respiratory triggered and
free breathing imaging techniques, which facilitates focal liver lesion
detection. Our free breathing technique showed to be robust against respiration
and is thus recommended for clinical usage. The
respiratory triggered technique is advantageous in providing a relatively
higher spatial resolution and SNR when the patient respiration is stable. More
studies involving patients are underway to validate the diagnostic value of the
proposed solution.
Acknowledgements
None.References
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[2] Galea N et, al. JMRI 2013; 37(6):1260-76. [3]
Lin W et, al MRM 2010; 64(3):757-66. [4] Edelman et, al. Radiology 1991; 181(3):655-660.
[5] Wang J et, al. JMRI 2010; 31(5):1256-1263. [6] Li L et, al. MRM 2012;
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