Effect of echo-sampling strategy on the accuracy of out-of-phase and in-phase multiecho gradient-Echo MRI hepatic fat fraction estimation

• Published in: Journal of magnetic resonance imaging Vol. 39; no. 3; pp. 567 - 575
• Main Authors: Levin, Yakir S., Yokoo, Takeshi, Wolfson, Tanya, Gamst, Anthony C., Collins, Julie, Achmad, Emil A., Hamilton, Gavin, Middleton, Michael S., Loomba, Rohit, Sirlin, Claude B.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.03.2014; Wiley Subscription Services, Inc
• Subjects: Adipose Tissue - metabolism; Adolescent; Adult; Child; Cross-Sectional Studies; Echo-Planar Imaging - methods; fat quantification; Fatty Liver - diagnosis; Fatty Liver - pathology; fatty liver disease; Female; hepatic steatosis; Humans; Image Interpretation, Computer-Assisted; Linear Models; magnetic resonance; Magnetic resonance imaging; Magnetic Resonance Spectroscopy - methods; Male; Middle Aged; multiecho; Prospective Studies; Sensitivity and Specificity; Young Adult; multiecho; fat quantification; magnetic resonance; fatty liver disease; hepatic steatosis
• ISSN: 1053-1807; 1522-2586; 1522-2586
• DOI: 10.1002/jmri.24193

Purpose To assess the effect of echo‐sampling strategy on the accuracy of out‐of‐phase (OP) and in‐phase (IP) multiecho gradient‐echo magnetic resonance imaging (MRI) hepatic fat fraction (FF) estimation, using MR spectroscopy (MRS) proton density FF (PDFF) as a reference standard. Materials and Methods In this Institutional Review Board (IRB)‐approved, Health Insurance Portability and Accountability Act (HIPAA)‐compliant prospective study, 84 subjects underwent proton MRS and non‐T1‐weighted gradient‐echo imaging of the liver at 3T. Imaging data were collected at 16 nominally OP and IP echo times (TEs). MRI‐FF was estimated while varying two echo‐sampling parameters (number of consecutive echoes, starting echo number). For each combination of these parameters, MRI‐FF estimation accuracy was assessed with slope, intercept, average bias, and R2 from a linear regression of MRS‐PDFF on MRI‐FF. The relationship between accuracy metrics and echo‐sampling parameters was assessed by Spearman rank correlation. Results For FF calculations using 3–16 echoes and a starting echo number of 1, the intercept ranged from 0.0046 to 0.0124, slope from 0.941 to 0.96, average bias from 0.0034 to 0.0078, and R2 from 0.968 to 0.976. All four accuracy metrics were the best with the 3‐ and 4‐echo calculations and worsened progressively with an increasing number of echoes. For a given number of echoes, there was an overall trend toward decreasing accuracy as starting echo number increased. Spearman correlation coefficients between starting echo number and intercept, slope, average bias, and R2 were 0.911, −0.64, −0.889, and −0.954, respectively, indicating progressive loss of accuracy in each case. Conclusion Multiecho OP and IP imaging provided high FF estimation accuracy. Accuracy was highest using the earliest 3 or 4 echoes. Incorporation of additional echoes or delaying the starting echo number progressively reduced accuracy. J. Magn. Reson. Imaging 2014;39:567–575. © 2013 Wiley Periodicals, Inc.