title: Simultaneous R2*, R2, and R2' quantification by combining S0 estimation of the free induction decay with a single spin echo: A single acquisition method for R2 insensitive quantification of holmium-166-loaded microspheres.
abstract: OBJECTIVE
  To present a new method, S0 estimation of the free induction decay combined with a single spin echo measurement (SOFIDSE), that enables simultaneous measurements of R2*, R2, and R2' in order to quantify the local concentration of holmium microspheres (Ho-MS) for radioembolization.
  
  
  METHODS
  SOFIDSE estimates R2* and the signal magnitude at time point 0, S0, from a multigradient echo readout of the free induction decay and subsequently estimates R2 using S0 and a single spin echo, from which R2' is deducted. The method was evaluated by comparing SOFIDSE R2 values with values obtained from shifted spin echo (SSE) measurements on a phantom setup containing Ho-MS and from dual spin echo measurements on a healthy volunteer.
  
  
  RESULTS
  On average, SOFIDSE showed a small overestimation of R2 values compared with SSE independent of the microsphere concentration. R2' values determined by subtraction of either SOFIDSE R2 or SSE R2 from R2* showed excellent agreement (correlation coefficient = 1; P = 9 · 10(-11)). The Ho-MS-induced R2' values obtained by SOFIDSE were insensitive to the R2 value of the tissue in which they resided.
  
  
  CONCLUSIONS
  SOFIDSE enables quantification of Ho-MS, in media with spatially or temporally varying R2 values, in a single acquisition.
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: G H
authors.initials: GH
authors.lastname: van de Maat
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: de Leeuw
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: P R
authors.initials: PR
authors.lastname: Seevinck
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: M A A J
authors.initials: MA
authors.lastname: van den Bosch
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: J F W
authors.initials: JF
authors.lastname: Nijsen
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: C J G
authors.initials: CJ
authors.lastname: Bakker
mesh_terms: D000328:Adult; D002214:Capsules / Q000032:analysis / Q000737:chemistry; D017352:Echo-Planar Imaging / Q000379:methods*; D006695:Holmium / Q000032:analysis*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008863:Microspheres; D057054:Molecular Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011868:Radioisotopes / Q000032:analysis*; D019275:Radiopharmaceuticals / Q000032:analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels; D014018:Tissue Distribution
chemical_list: D002214:Capsules; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D013113:Spin Labels; D006695:Holmium
keywords: R2; R2*; S0 estimation; SOFIDSE; holmium microspheres; quantification