title: The impact of spin coupling signal loss on fat content characterization in multi-echo acquisitions with different echo spacing.
abstract: This study aimed to assess the effect of echo spacing in transverse magnetization (T2) signal decay of gel and fat (oil) samples. Additionally, we assess the feasibility of using spin coupling as a determinant of fat content.
  
  
  
  Phantoms of known T2 values, as well as vegetable oil phantoms, were scanned at 1.5T scanner with a multi echo FSE sequence of variable echo spacing above and below the empirical threshold of 20ms for echo train signal modulation (6.7, 13.6, 26.8, and 40ms). T2 values were calculated from monoexponential fitting of the data. Relative signal loss between the four acquisitions of different echo spacing was calculated.
  
  
  
  Agreement in the T2 values of water gel phantom was observed in all acquisitions as opposed to fat phantom (oil) samples. Relative differences in signal intensity between two successive sequences of different echo spacing on composite fat/water regions of interest was found to be linearly correlated to fat fraction of the ROI.
  
  
  
  The sample specific degree of signal loss that was observed between different fat samples (vegetable oils) can be attributed to the composition of each sample in J coupled fat components. Hence, spin coupling may be used as a determinant of fat content.
authors.affiliation: Computational BioMedicine Laboratory, FORTH-ICS, Heraklion, Crete, Greece; Department of Medical Physics, University of Crete, Heraklion, Crete, Greece. Electronic address: nikiforakik@gmail.com.
authors.forename: K
authors.initials: K
authors.lastname: Nikiforaki
authors.affiliation: Computational BioMedicine Laboratory, FORTH-ICS, Heraklion, Crete, Greece.
authors.forename: G C
authors.initials: GC
authors.lastname: Manikis
authors.affiliation: Department of Medical Physics, University of Crete, Heraklion, Crete, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Boursianis
authors.affiliation: Computational BioMedicine Laboratory, FORTH-ICS, Heraklion, Crete, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Marias
authors.affiliation: Computational BioMedicine Laboratory, FORTH-ICS, Heraklion, Crete, Greece; Department of Radiology, University of Crete, Heraklion, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Karantanas
authors.affiliation: Computational BioMedicine Laboratory, FORTH-ICS, Heraklion, Crete, Greece; Department of Medical Physics, University of Crete, Heraklion, Crete, Greece.
authors.forename: T G
authors.initials: TG
authors.lastname: Maris
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D014867:Water
chemical_list: D014867:Water
keywords: Echo spacing; Fat content; Spin coupling; T2 relaxometry