Free‐breathing liver fat and R2∗ quantification using motion‐corrected averaging based on a nonlocal means algorithm. Issue 2 (1st August 2020)

• Record Type: Journal Article
• Authors: Luo, Huiwen; Zhu, Ante; Wiens, Curtis N.; Starekova, Jitka; Shimakawa, Ann; Reeder, Scott B.; Johnson, Kevin M.; Hernando, Diego
• Is Part Of: Magnetic resonance in medicine. Volume 85:Issue 2(2021)
• Page Start: 653
• Page End: 666
• Publication Date: 2020-08-01
• Subjects: liver -- motion‐corrected averaging -- nonlocal means -- proton density fat fraction -- quantification -- R2∗; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.28439
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : Purpose: To propose a motion‐robust chemical shift‐encoded (CSE) method with high signal‐to‐noise (SNR) for accurate quantification of liver proton density fat fraction (PDFF) and R 2 ∗ . Methods: A free‐breathing multi‐repetition 2D CSE acquisition with motion‐corrected averaging using nonlocal means (NLM) was proposed. PDFF and R 2 ∗ quantified with 2D CSE‐NLM were compared to two alternative 2D techniques: direct averaging and single acquisition (2D 1ave) in a digital phantom. Further, 2D NLM was compared in patients to 3D techniques (standard breath‐hold, free‐breathing and navigated), and the alternative 2D techniques. A reader study and quantitative analysis (Bland‐Altman, correlation analysis, paired Student's t ‐test) were performed to evaluate the image quality and assess PDFF and R 2 ∗ measurements in regions of interest. Results: In simulations, 2D NLM resulted in lower standard deviations (STDs) of PDFF (2.7%) and R 2 ∗ (8.2 s - 1 ) compared to direct averaging (PDFF: 3.1%, R 2 ∗ : 13.6 s - 1 ) and 2D 1ave (PDFF: 8.7%, R 2 ∗ : 33.2 s - 1 ). In patients, 2D NLM resulted in fewer motion artifacts than 3D free‐breathing and 3D navigated, less signal loss than 2D direct averaging, and higher SNR than 2D 1ave. Quantitatively, the STDs of PDFF and R 2 ∗ of 2D NLM were comparable to those of 2D direct averaging (p>0.05). 2D NLM reduced bias, particularly in R 2 ∗ (−5.73 to −0.36 s - 1 ) that arises in direct averaging (−3.96 to 11.22 s - 1 ) in the presence of motion. Conclusions: 2D CSE‐NLM enables accurate mapping of PDFF and R 2 ∗ in the liver during free‐breathing.