title: Orbital Fat Volumetry and Water Fraction Measurements Using T2-Weighted FSE-IDEAL Imaging in Patients with Thyroid-Associated Orbitopathy.
abstract: OBJECTIVE
  The quantitative evaluation of orbital fat proliferation and edema and the assessment of extraocular muscles are useful for diagnosing and monitoring thyroid-associated orbitopathy. To evaluate therapy-induced quantitative changes in the orbital fat of patients with thyroid-associated orbitopathy, we performed volumetric and water fraction measurements by using T2-weighted FSE iterative decomposition of water and fat with echo asymmetry and least-squares estimation (FSE-IDEAL) imaging.
  
  
  METHODS
  Orbital FSE-IDEAL images of 30 volunteers were acquired twice within 1 week. Nine patients with thyroid-associated orbitopathy underwent FSE-IDEAL imaging before and after methylprednisolone pulse therapy, and the treatment results were assessed by using their pre- and post-methylprednisolone pulse therapy clinical activity scores. We performed volumetric and water fraction measurements of orbital fat by using FSE-IDEAL imaging and evaluated interscan differences in the volunteers. In patients with thyroid-associated orbitopathy, we compared pre- and posttherapy orbital fat measurements and assessed the correlation between the pretherapy values and clinical activity score improvement.
  
  
  RESULTS
  The reproducibility of results obtained by the quantitative evaluation of orbital fat in volunteers was acceptable. After methylprednisolone pulse therapy, the water fraction in the orbital fat of patients with thyroid-associated orbitopathy was significantly decreased (P< .001). There was a significant positive correlation between the pretherapy water fraction and clinical activity score improvement (right,r= 0.82; left,r= 0.79) and a significant negative correlation between the pretherapy volume and clinical activity score improvement (bilateral,r= -0.84).
  
  
  CONCLUSIONS
  Volumetric and water fraction measurements of orbital fat by using FSE-IDEAL imaging are feasible and useful for monitoring the effects of therapy and for predicting the response of patients with thyroid-associated orbitopathy to methylprednisolone pulse therapy.
authors.affiliation: From the Department of Diagnostic Radiology (Y.K., K.A.), Graduate School and Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan kaichi@hiroshima-u.ac.jp.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0001-6213-941X
authors.initials: Y
authors.lastname: Kaichi
authors.affiliation: Department of Radiology (K.T.), Chugoku Rosai Hospital, Kure, Japan.
authors.forename: K
authors.identifier: http://orcid.org/0000-0002-5825-376X
authors.initials: K
authors.lastname: Tanitame
authors.affiliation: Department of Ophthalmology and Visual Science (H.I.).
authors.forename: H
authors.identifier: http://orcid.org/0000-0002-1040-7504
authors.initials: H
authors.lastname: Itakura
authors.affiliation: Department of Molecular and Internal Medicine (H.O., M.Y.), Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: H
authors.identifier: http://orcid.org/0000-0001-5400-1162
authors.initials: H
authors.lastname: Ohno
authors.affiliation: Department of Molecular and Internal Medicine (H.O., M.Y.), Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: M
authors.identifier: http://orcid.org/0000-0001-6237-7688
authors.initials: M
authors.lastname: Yoneda
authors.affiliation: Department of Clinical Radiology (Y.T., Y.A.), Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0003-2394-2386
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Clinical Radiology (Y.T., Y.A.), Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0001-7153-8658
authors.initials: Y
authors.lastname: Akiyama
authors.affiliation: From the Department of Diagnostic Radiology (Y.K., K.A.), Graduate School and Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: K
authors.identifier: http://orcid.org/0000-0002-5039-2546
authors.initials: K
authors.lastname: Awai