3D whole liver black blood imaging: a 3 min solution consisting of respiratory triggering and free breathing imaging techniques
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

[1] Schieda N et, al. Clin Radiol 2014;69(11):1136-41. [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; 68:1423-1438.

Figures

Fig.1 Representative images from the respiratory triggered VISTA (A1 & A2) and free breathing technique (B1 & B2). BB preparation improves the image contrasts in the peripheral liver regions for both techniques (A1, B1 without BB preparation; A2, B2 with).

Fig.2 Two healthy volunteers experienced unstable respiration during scanning. Free breathing technique (A2 & B2) depicts much better vessel boundaries than the respiratory triggered one (A1 &B1).

Fig.3 Respiratory triggered technique, due to lower background noise level, yields a higher CNR (volunteer 1-4). However, it’s also much more sensitive to respiration and image quality declines greatly in case of irregular or unstable breathing (volunteer 5 & 6).



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